CN111512576A - Method and apparatus for hardware configured network - Google Patents

Abstract

A method for configuring a hardware configured optical link includes generating a first optical signal comprising a slow scan of wavelength channels, wherein the slow scan has a dwell time on a particular wavelength channel. Generating a second optical signal comprising a fast scan of wavelength channels, wherein the fast scan has a dwell time on a particular wavelength channel and a full channel scan time, wherein a slow scan dwell time is greater than or equal to the full channel scan time. The first optical signal is transmitted over the link and then the portion is detected. Light pulses having a duration less than the dwell time on the rapidly scanned particular wavelength channel are then detected. Client data traffic is then sent over the link in response to detecting the optical pulse and detecting the portion of the first optical signal.

Description

Method and apparatus for hardware configured network

The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in the application in any way.

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application serial No. 62/573,142 entitled "Method and Apparatus for hardware-Configured Network" filed on 16/10/2017. U.S. provisional patent application serial No. 62/573,142 is incorporated herein by reference in its entirety.

Background

The increased need for high-capacity data transmission over optical fibers and the increased number of optical network elements that are flexibly and dynamically networked together pose significant challenges to the optical fiber telecommunications industry. For example, higher capacity demands require more transceiver wavelengths to be more closely spaced together in the spectral domain to provide higher capacity on a single fiber or connection. These high capacity high channel number systems require more real-time performance data monitoring to control the transceiver. In addition, the larger number of transceivers required for these high capacity high channel count systems requires a higher degree of automation of the transceiver configuration to improve reliability and reduce human operation. In addition, configuring a network to include an increased number of various optical elements (including transceivers, amplifiers, wavelength filters, wavelength multiplexers, wavelength demultiplexers, cross-connects, optical switches, passive splitters, and combiners) requires automation and control schemes capable of operating on the various optical element types.

It is desirable for high capacity high channel number systems to have an automated configuration that allows network elements to self-provision and self-monitor in order to reduce the burden on network operators during network discovery (turn-up) as well as during ongoing operation. The automation allows larger scale optical networks to be constructed and operated at lower cost.

It is also desirable for high capacity, high channel number optical communication systems to have dynamic and reconfigurable optical networks that provide increased network flexibility and bandwidth utilization. These optical communication systems often require real-time configuration in response to changing conditions and data communication requirements. In addition, support for dynamic traffic (traffic) routing requires advanced wavelength and channel monitoring to tune the transceiver and Wavelength Selective Switch (WSS) wavelength.

In addition, adapting optical communication systems to achieve high capacity and high channel count requires providing enhanced configurability within the same or smaller coverage area as currently deployed optical communications. It is therefore desirable that the configuration method and apparatus be reusable and/or rely to a large extent on existing network element components.

Drawings

The present teachings in accordance with the preferred exemplary embodiments, as well as further advantages thereof, are more particularly described in the following detailed description taken in conjunction with the accompanying drawings. Those skilled in the art will appreciate that the drawings described below are for illustration purposes only. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the teachings. In the drawings, like numerals generally refer to like features and structural elements throughout the various views. The drawings are not intended to limit the scope of applicants' teachings in any way.

FIG. 1A shows a block diagram of an embodiment of a hardware configured optical element of the present teachings.

FIG. 1B shows a block diagram of an embodiment of a hardware configured optical element of the present teachings in which an optical carrier signal is generated internally within the optical element.

Figure 1C shows a block diagram of an embodiment of a hardware configured optical element of the present teachings in which the optical carrier signal originates externally from the optical element.

Figure 1D illustrates a block diagram of one embodiment of the optical components comprising a hardware configuration of an optical transceiver.

FIG. 1E shows an oscilloscope trace of the measured output of the optical transceiver on the transmit fiber described in connection with FIG. 1D.

Figure 2A represents a block diagram of an embodiment of a hardware configured optical component of the present teachings including an optical transceiver with a tunable transmitter.

Figure 2B shows a spectrum representing the measured output of a tunable transceiver on a transmitting fiber according to the present teachings.

Figure 2C shows a long time scale oscilloscope trace of low frequency modulation measured at the output of a tunable transceiver on a transmitting fiber according to the present teachings.

Figure 3A represents an embodiment of a hardware configured network element according to the present teachings that includes a wavelength selective switch.

FIG. 3B represents an oscilloscope trace showing the measured output of a wavelength selective switch for a low frequency control signal according to the present teachings.

Figure 4 illustrates a block diagram of one embodiment of a hardware configured optical element including an optical amplifier in accordance with the present teachings.

Figure 5 shows an oscilloscope trace of a low frequency control signal according to the present teachings including a collision avoidance protocol based on a modification of the well known ethernet protocol.

Figure 6 represents an embodiment of a hardware-configured network of the present teachings in a point-to-point transceiver topology (sometimes referred to in the art as an optical link).

Figure 7 represents an embodiment of a network of hardware configurations of the present teachings that includes a plurality of tunable transceivers connected to wavelength selective switches or optically programmable filter elements.

Figure 8 shows an embodiment of a network including a hardware configuration of the present teachings with a wavelength division multiplexed network of wavelength selective switching optical elements.

Fig. 9 shows a network of the hardware configuration of fig. 8, in which the wiring is erroneously installed at the position B.

Fig. 10 shows a network of the hardware configuration of fig. 8 in which the mounter makes an error in wiring the components at location a.

FIG. 11 illustrates an embodiment of a low cost combiner-splitter including hardware configured elements in accordance with the present teachings.

Figure 12A represents a block diagram of an embodiment of a hardware configurable link of a tunable transceiver including a hardware configuration of the present teachings.

Figure 12B shows a block diagram of an embodiment of a transceiver according to the present teachings that may be used with the hardware configurable link described in conjunction with figure 12A.

FIG. 13 shows a graph showing optical power as a function of time for an embodiment of a set of transmitter states according to the present teachings.

Figure 14 shows a graph showing optical power as a function of time for a set of transmitter and receiver states that exist during an embodiment of a method of connecting protocols of the present teachings.

Figure 15 represents a flow diagram of an embodiment of a protocol for establishing a link using a hardware-configured transceiver element of the present teachings.

Figure 16 shows a graph of measured optical signals for an embodiment of a method of configuring an optical link using a hardware configured transceiver according to the present teachings.

Figure 17A shows a top view of an embodiment of a hardware-configured transceiver according to the present teachings.

Fig. 17B shows a bottom view of the hardware configured transceiver described in connection with fig. 17A.

Figure 17C shows a top view of another embodiment of a hardware-configured transceiver according to the present teachings.

Figure 18 shows a schematic diagram of an embodiment of the opto-electronic components in a hardware configured transceiver of the present teachings.

Figure 19A shows a schematic diagram of an embodiment of a WDM transport system including a hardware configured transceiver of the present teachings.

Figure 19B shows a schematic diagram of the WDM transport system of figure 19A in the state of an embodiment of a setup protocol of the hardware configuration of the present teachings.

Figure 19C shows a schematic diagram of the WDM transport system of figure 19A in another state of an embodiment of a setup protocol of a hardware configuration of the present teachings.

Figure 19D shows a schematic diagram of the WDM transport system of figure 19A in another state of an embodiment of a setup protocol of a hardware configuration of the present teachings.

Figure 19E shows a schematic diagram of the WDM transport system of figure 19A in another state of an embodiment of a setup protocol of a hardware configuration of the present teachings.

Fig. 20 shows an embodiment of a remote PHY subsystem with gain of the present teachings.

Figure 21 shows a schematic diagram of an embodiment of a WDM transmission system with gain of a transceiver configured with hardware in accordance with the present teachings.

Fig. 22A represents an embodiment of a remote PHY system using a hardware configured network element of the present teachings configured for a telecommunications application.

FIG. 22B represents an embodiment of a remote PHY system using a hardware configured network element of the present teachings configured for data communication applications.

FIG. 23A represents an embodiment of a front panel of a remote PHY system using a hardware-configured network element of the present teachings.

FIG. 23B shows an embodiment of a backplane of a remote PHY system using a hardware-configured network element of the present teachings.

FIG. 24 shows a schematic diagram of the functional blocks and layout of an embodiment of a remote PHY system that supports two remote PHYs using a hardware configured network element of the present teachings.

Figure 25 shows a schematic diagram of an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect a hardware configured tunable transceiver using a fixed AWG filter in accordance with the present teachings.

Fig. 26A shows a state diagram of an embodiment of a method of automatic channel discovery for the optical link of the hardware configuration of fig. 25.

Fig. 26B shows a process flow diagram of an embodiment of a method of automatic channel discovery of an optical link of the hardware configuration of fig. 25.

Fig. 27A shows a graph showing optical power as a function of time for a set of transmitter and receiver states and associated state timing diagrams for an embodiment of a method of link connection associated with the hardware configured optical link of fig. 25.

Figure 27B represents an experimental setup to measure optical power as a function of time for an embodiment of a method of link connection associated with a hardware configured optical link of the present teachings.

FIG. 27C shows an oscilloscope trace showing optical power as a function of time for an embodiment of a method of connection protocol associated with the hardware configured optical link of FIG. 27B.

Figure 28A shows a schematic diagram of an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect tunable coherent transceivers of a hardware configuration using a filter-based combiner/splitter in accordance with the present teachings.

Fig. 28B shows a state diagram of an embodiment of a method of automatic channel discovery of an optical link of the hardware configuration of fig. 28A.

Fig. 28C shows a process flow diagram of an embodiment of a method of automatic channel discovery of an optical link of the hardware configuration of fig. 28A.

Fig. 28D shows a graph showing optical power as a function of time for a set of transmitter and receiver states that exist during an embodiment of a method of automatic channel discovery for the hardware configured optical link of fig. 28A.

Figure 29 shows a schematic diagram of an embodiment of a WDM transport link utilizing two unidirectional optical fibers to connect a hardware configured tunable coherent transceiver using a non-filter based combiner/splitter in accordance with the present teachings.

Figure 30A shows a spectrum generated by a transceiver in a startup state according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 30B shows a spectrum generated by a transceiver in an established link operating state according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 30C shows a spectral time series of a transceiver in a tuned state without RF modulation according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 30D shows a spectral time series in a tuned state with a link having RF modulation on channel 1, according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 31 shows a schematic diagram of an embodiment of a bidirectional WDM transport link utilizing a coherent hardware configured transceiver with an AWG splitter of the present teachings.

Figure 32 shows a schematic diagram of an embodiment of a bidirectional WDM transport link utilizing coherent hardware-configured transceivers with unfiltered passive splitters in accordance with the present teachings.

Figure 33A shows a spectral time series of a transceiver in a tuned state without RF modulation according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 33B shows a spectral time series showing how a transceiver without RF modulation can utilize latency tuning between sequences to avoid collisions in accordance with an embodiment of a method of using a connection protocol of the present teachings.

Figure 33C shows the spectrum of a transceiver with RF modulation after a successful completion of a connection according to an embodiment of a method using a connection protocol of the present teachings.

Figure 34A shows a spectral time series associated with the state of the search and connect steps according to an embodiment of a method using a connection protocol of the present teachings.

Figure 34B shows a spectral time series associated with the state of a transceiver and an associated L O laser according to an embodiment of a method of using a connection protocol of the present teachings.

FIG. 35 represents a set of time series for an unfiltered optical link showing search and detection, according to an embodiment of a method of using a connection protocol of the present teachings.

Figure 36A shows a spectral timing diagram of an embodiment of a link establishment method for a coherent link with a non-filtering passive splitter/combiner of the present teachings.

Figure 36B shows a combined spectral timing diagram of an embodiment of a link establishment method for a coherent link with the unfiltered passive splitter/combiner of figure 36A.

Detailed Description

Reference in the specification to "one embodiment" or "an embodiment" means: the particular features, structures, or characteristics described in connection with the embodiment are included in at least one embodiment of the teachings. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

It should be understood that the steps of the methods of the present teachings may be performed in any order and/or simultaneously as long as the present teachings remain operable. Additionally, it should be understood that the apparatus and methods of the present teachings can include any number of the described embodiments or all of the described embodiments, so long as the present teachings remain operable.

The present teachings will now be described in more detail with reference to exemplary embodiments thereof as illustrated in the accompanying drawings. While the present teachings are described in conjunction with various embodiments and examples, the present teachings should not be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Those of ordinary skill in the art having access to the present teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein.

The term "element" or "network element" is used herein to describe various devices and optical subsystems used to establish and operate an optical network. Some examples of these devices and optical subsystems are transceivers, switches, wavelength selective switches, programmable filters, amplifiers, add/drop multiplexers, and cross-connects. As used herein, the term "component" describes the optical, mechanical, and electronic components that make up these subsystems. The term "network" describes a plurality of network elements connected to form a group or system of elements that exchange information and operate in a coordinated manner.

The term "configuration" when used in this disclosure in connection with a network is intended to include a variety of network management, control, and operational functions. For example, the term "configuration" includes various tasks such as component inspection, component diagnostics, component performance monitoring, and control of component operating parameters. Some terms of the art that should be considered part of the definition of "configuration" include network management, network operation, FCAPS (fault management, configuration, charging, performance, security), and network monitoring and alerting. Network management includes various tasks such as configuring, discovering, identifying and inspecting network elements, discovering and reacting to failures or misconfigurations of network elements, and monitoring performance of network elements. In addition, the term "configuration" can apply to a single element, or it can apply to a collection of elements that serve or are intended to serve as a connected system or network. In particular, the term "configuring a network" includes various tasks such as network discovery, passive monitoring, and active control of network operation.

The prior art optical network elements are configured primarily via the optical client interface. Management information is rarely or not exchanged directly between elements, such as transceivers, wavelength selective switches, amplifiers, and other elements in an optical network. Configuration information is typically sent on a single channel, which limits the amount of management information and the number of network elements that can be configured. A single management or supervisory channel also limits the amount of information available to external network management systems, especially during startup operations.

In addition, in prior art optical network configuration systems, a large amount of diagnostic information is sent from the network element to one or more external network management systems or users for processing. The diagnostic information is processed in the external network management system and instructions are then sent back to the elements to generate network configuration changes. This remote and/or in-person (hands-on) configuration architecture of known systems limits the size of networks that can be configured. This limitation is especially true as the amount of information from network elements that needs to be processed increases in order to improve element monitoring and/or provide dynamic element operation. For example, support for dynamic traffic routing requires optical components that provide large amounts of real-time data for optical path computation, including embedded amplifier performance and dynamic path spectral conditions.

It would therefore be highly desirable to have a method and apparatus for configuring elements in an optical network that is automated, tunable over multiple channels, and operates on the various optical elements that make up the network. The present teachings relate, at least in part, to embodiments of methods and apparatus for transmitting and processing control and management information for a Hardware Configured Network (HCN). As used herein, the term "hardware-configured network" is a networked system of optical and electrical switching and transmission elements and components that automatically configure, control, and manage their operation with little or no user input.

One possible characteristic of a hardware configured network is: it automatically connects and provides channels and wavelengths without centralized commands or user intervention. Another possible characteristic of a hardware configured network is: it detects and corrects configuration errors without centralized commands or user intervention. Another possible characteristic of a typical hardware configured network is: it reconfigures the optical elements without a centralized command or user intervention. Examples of configurations performed by hardware configured networks include component start-up, tuning of tunable components, programming of programmable optical filter characteristics such as bandwidth, filter shape, dispersion, and other configurable parameters, setting attenuation levels of Wavelength Selective Switches (WSS), setting gain and gain spectra on Erbium Doped Fiber Amplifiers (EDFAs), configuring ports and wavelengths of each port for optical switches and wavelength add/drop multiplexers and cross-connects, and optical link establishment. Although aspects of the hardware-configured network of the present teachings are described in connection with self-configuration of network elements, those skilled in the art will appreciate that user and/or centralized commands or external management systems that can access configuration control and information of the hardware-configured network can also be used in connection with self-configuration of network elements.

FIG. 1A shows a block diagram of an embodiment of a hardware configured optical element according to the present teachings. The hardware-configured network of the present teachings transmits control information over the network using low frequency modulation modulated onto various optical signals passing through the network (rather than using a dedicated supervisory optical channel). That is, the low frequency modulated optical carrier used to transmit and receive control information is some portion of the optical signal propagating in the network. These optical signals used as optical carriers in various embodiments of hardware configured networks of the present teachings can include customer data traffic, spurious signals, CW light, and amplified spontaneous emissions. As used herein, the term "optical carrier" is defined as any light to which a modulation (which may be a low frequency modulation) is applied. This definition is broader than other uses of this term in the art. For example, in some applications of optical communications, the term "optical carrier" is used to describe a particular wavelength of light used to transmit data, often an ITU-grid based wavelength from a laser transmitter. In various embodiments, the optical carrier can be generated in the optical element itself, or the optical carrier can be an optical carrier received from a network.

The hardware configurable optical element 100 includes an electronic control port 102 for sending and receiving electrical control information. An electronic control port 103 is also included for sending and receiving client data traffic. The hardware configurable optical element 100 further comprises: an output port coupled to a transmission optical fiber 104 for transmitting optical signals to an optical network; and an input port coupled to a receive optical fiber 106 for receiving optical signals from the optical network. The demodulator 108 decodes the receive control information received from the receive fiber 106 and sends the decoded control information to the control processor 110, and the control processor 110 processes the information and then configures the optical elements according to the control information.

The optical modulator 112 modulates the optical carrier with the transmission control information so that the transmission control information can be transmitted into the optical network. In one method of operation, optical modulator 112 modulates an optical carrier with low frequency modulation representative of the transmission control information. The transmit optical control signal is then transmitted to the network using transmit optical fiber 104. In some methods of operation, the transmit optical control signal is applied directly to the customer data signal used as the optical carrier, and this combination of modulated optical signals is then transmitted over the transmit optical fiber 104.

FIG. 1B shows a block diagram of an embodiment of a hardware configured optical element 120 of the present teachings in which an optical carrier signal is generated internally within the optical element. That is, the optical carrier signal is generated by an optical signal generator 122 located inside the optical element. In some embodiments, the optical signal generator 122 is part of a client transmitter of an optical transceiver component. In some embodiments, the transceiver operates using a coherent signaling format. In some embodiments, the optical transceiver is a tunable coherent transceiver and the optical signal generator is a tunable laser that generates a local oscillator signal. In some embodiments, the optical signal generator 122 includes an optical amplifier and the optical carrier is amplified spontaneous emission. Modulator 124 is used to modulate the optical carrier with control information. In some methods of operation, control information is generated by the local processor 126. In other methods of operation, the control information is generated by a remote source having an output electrically connected to the electronic control port 128. In some embodiments, the optical amplifier gain generated by the optical amplifier that is part of the optical signal generator 122 is controlled by a pump laser. The low frequency modulation is implemented as a gain variation over time. Thus, in some embodiments, modulator 124 is a gain controller. In embodiments including an optical amplifier modulated to add control information, the amplified spontaneous emission from the amplifier carries the control information if no optical carrier signal is present. If, on the other hand, one or more carriers are present, modulation of the gain imparts information on each of the one or more carriers. These various carriers may then follow different paths in the optical network, for example, because they may occupy different wavelength channels that are routed differently. A port 136 is also provided for transmitting and receiving client data traffic, the port 136 being connected to the modulator 124 and the demodulator 134. Splitter 130 is used to split a portion of an input optical signal that includes a receive control signal from optical network 132. The demodulator 134 decodes the reception control information and then sends the reception control information to the control processor 126, and the control processor 126 configures the hardware-configured element 120 based on the provided control information.

Figure 1C shows a block diagram of an embodiment of a hardware configured optical element 140 of the present teachings in which the optical carrier signal originates externally from the optical element. The optical carrier originates from the optical network and arrives at the input fiber 142. A portion of the optical signal from the input fiber 142 is split by the splitter 144 and sent to the demodulator 148. The demodulator 148 decodes the reception control information and then transmits the reception control information to the control processor 149, and the control processor 149 configures the hardware-configured element 140 based on the provided control information. A portion of the optical signal is split by splitter 144 and sent to optical modulator 146, and optical modulator 146 applies transmit control information in the form of low frequency modulation on the optical carrier. The transmit optical control signal then exits the optical element on transmit optical fiber 147. A port 150 for client data traffic is also provided, the port 150 being connected to the demodulator 148 and the modulator 146. In some embodiments, a wavelength selective switch with a photodiode is used as the demodulator 148. In some embodiments, a VOA with a wavelength selective switch is used as the modulator 146.

In some embodiments, the optical carrier includes a customer data signal generated by an optical transceiver component located upstream of the hardware-configured optical component 140. In some embodiments, the client data signal is generated using a coherent signaling format. In other embodiments, the optical carrier includes amplified spontaneous emission from an upstream optical amplifier. Fig. 1D shows a block diagram of one embodiment of the optical components comprising a hardware configuration of the optical transceiver 150. The optical transceiver 150 includes an electrical control port 152 for sending and receiving electronic command and control information. Electrical port 158 provides and receives customer data traffic. In some embodiments, the electrical control port 152 is an industry standard I2C interface. In other embodiments, the electrical control port 152 uses a multi-master multi-slave serial protocol for embedded system control. The optical transceiver 150 further includes: an output optically coupled to the transmit optical fiber 154; and an input optically coupled to the receive fiber 156, the receive fiber 156 transmitting the optical signal to the optical transceiver 150. The optical signals can include either or both of customer data traffic and low frequency control signals in the transmit optical fiber 154 and the receive optical fiber 156. The client data traffic can include network traffic sent over the network. The low frequency control signal can include various types of information for configuring the network element.

Fig. 1E shows an oscilloscope trace of the measured output 160 on the transmit fiber 154 of the optical transceiver 150 described in connection with fig. 1D. Referring to fig. 1D and 1E, in this embodiment, the optical transceiver 150 generates a client data traffic 162 at a10 Gb/s data rate. The client data traffic 162 exhibits high and low data levels as a function of time on a relatively long time scale. The modulated control signal 164 uses strings of "1" and "0" at low frequencies that are applied directly to the optical communication signals comprising the client data traffic 162.

Accordingly, one aspect of the present teachings is to encode the control signal 164 using strings of 1's and 0's at low frequencies that are applied directly on the optical communication signal from the transceiver 100. In the embodiment shown in fig. 1D, 1E, the control signal 164 is applied directly to the client data traffic 162 generated by the transceiver 150. In various embodiments, low frequencies "1" and "0" can be decoded at corresponding receive optical elements (not shown) optically coupled to the transmit optical fiber 154. The low frequency modulation may be amplitude modulation as shown in fig. 1E. In various other embodiments, the low frequency modulation can be any modulation format, such as phase modulation or frequency modulation.

Significantly, it should be noted that the client data traffic 162 is not affected by low frequency modulation. One advantage of using the "1" and "0" strings 164 at low frequencies to encode the control signal to provide the control signal 164 that is applied directly on the optical signal from the transceiver 150 is that: the frequencies used for low frequency modulation typically cannot pass through an electrical filter in a receiver that decodes high data rate client data traffic 162. The baseline wander may set the low frequency cut-off of these high pass filters as low as 100kHz depending on the details of the modulation, scrambling and encoding of the optical signal. Thus, the frequency of the low frequency control signal is selected to be lower than the lowest frequency of the high pass filtering used in the transceiver, and therefore, the low frequency control signal will not affect the integrity of the client data traffic 162. In addition, encoding and decoding based on low frequency modulation can be accomplished using relatively low cost, lower bandwidth optical and electronic devices that are well known and widely available in the art. Some embodiments of a hardware configured network according to the present teachings use optical and electrical components already present in currently deployed transceivers 150.

FIG. 2A shows a block diagram 200 of one embodiment of the optical components of a hardware configuration including an optical transceiver having a tunable transmitter 202. the optical transceiver may also include a detector and a receiver. in some embodiments, the detector and receiver may be a L O detector and receiver that may process signals from the link. in some embodiments, the tunable transmitter 202 also includes a receiver having a detector that may also include a local oscillator detector for coherent detection of incoming signals.some embodiments use two L O lasers, one for transmission and one for reception, and some embodiments use a L O laser, the L O laser being used for both transmission and reception.the tunable transceiver 202 includes an electrical control port having an electrical input 204 for transmitting and receiving command and control information.additionally, port 208 is used for input customer data traffic.in some embodiments, the input port 208 for input customer data traffic may be the same input port as the electrical input 204 for transmitting and receiving command and control information.the input port 208 may be an electrical port 208. in some embodiments, the tunable transceiver 202 may use an optical fiber optic transceiver to receive optical signals from a coherent optical fiber optic transceiver 206, receive optical signals, and process signals from the optical transceiver 202 using a coherent optical fiber optic transceiver 206, receive optical signals, and receive signals from the optical fiber optic transceiver 206 in some embodiments.

Figure 2B shows a spectrum 208 representing the measured output of the tunable transceiver on the transmit fiber 206 according to the present teachings. Spectrum 208 indicates: a tunable laser in the tunable transceiver 202 generates a modulated signal on a particular wavelength channel 210. In one particular embodiment, the tunable transceiver 202 wavelength or channel can be set and adjusted over a wavelength range from 1528nm to 1567 nm.

Referring to fig. 2A and 2B, in this embodiment, the optical transceiver 200 is generating a client data traffic 224 at a10 Gb/s data rate, the client data traffic 224 being shown as high and low data levels as a function of time using a relatively long time scale of measured oscilloscope traces 220 of modulated signals on a particular wavelength channel 210. The control and management information for configuring the network is encoded as a string 222 of "1" s and "0" s at a low frequency that are applied directly to the client data traffic 224. In some methods of operation according to the present teachings, a typical output power of the tunable transceiver 202 is in the range of 0-3dbm, which corresponds to approximately 1-2 mW. Further, in some methods of operation, the low frequency coded modulation format is a low frequency power variation of the tunable laser channel, and thus operates at the wavelength of the laser channel set point. Additionally, in some methods of operation, the modulation depth of the low frequency modulation is between about 0.5% and 10%. In some embodiments, the low frequency modulation is 5% or less. In various embodiments, client data traffic 224 uses various known modulation formats. For example, the client data traffic 224 may utilize coherent modulation.

One feature of the present teachings is that the low frequency modulation may be manifested as a high extinction low frequency modulation. For example, the transceiver of fig. 2A may be turned on and off at low frequencies. In this case, the control signal "0" would be when the transceiver is turned off, and the low frequency "1" would be when the transceiver is turned on. Figure 2C shows a long time scale oscilloscope trace 240 of a low frequency modulation measured at the output of a tunable transceiver on a transmitting fiber according to the present teachings. The transceiver client data traffic 242 is generated at a10 Gb/s data rate. The control and management information for configuring the network is encoded as a string 244 of "1" s and "0" s at low frequencies that are applied directly to the client data traffic 242, and is shown as high and low data levels as a function of time using the relatively long time scale of oscilloscope traces 240. In this embodiment, the extinction of low frequency modulation is very high, however, the frequency of the low frequency control signal is selected to be lower than the lowest frequency of the high pass filtering used in the transceiver, so the low frequency control signal will not affect the integrity of the client data traffic 242.

Thus, one feature of a hardware configured network according to the present teachings is: the control information is encoded on the tunable transmitter signal so that the wavelength carrying the encoded control information is tunable based on the tuning configuration of the tunable transmitter. Thus, by tuning the wavelength of the signal carrying the encoded information, the destination of the encoded control information can be changed based on the specific wavelength path configured in the optical network. For example, a configuration that includes wavelength switches, filters, and amplifiers of an optical network establishes a wavelength path from a source to a destination in the optical network. Wavelength paths from various sources to various destinations may also be changed based on reconfiguration of the network elements. The source wavelength may be tuned to take a desired wavelength path to a particular destination or set of destinations, and therefore, a low frequency control signal applied on an optical signal at the source wavelength will provide encoded control information to the particular destination or set of destinations. Thus, the destination of the low frequency control signal can be changed by simply tuning the laser wavelength of the tunable transceiver. This ability to select the wavelength of the control signal carrying the low frequency modulation allows the encoded control information from one network element to reach any of a variety of different elements in the network by selecting a particular wavelength path.

Another feature of a hardware configured network according to the present teachings is: the low frequency encoding of the control signal on a particular wavelength does not affect other wavelengths propagating in the fiber or throughout the optical network.

FIG. 3A shows an embodiment of a hardware configured optical element 300 according to the present teachings that includes a wavelength selective switch 302. In some embodiments according to the present teachings, the wavelength selective switch 302 is a standard commercially available wavelength selective switch 302 without special modifications. Wavelength selective switches are widely present in the realm of port fabrics and channel planning and are currently used in prior art optical networks. Wavelength selective switches, such as those manufactured by Finisar corporation, provide a highly programmable and flexible switching platform that switches traffic from one optical link to another over multiple wavelengths in the same network. However, a wavelength selective switch according to the present teachings can be configured with additional features according to the present teachings. In one embodiment of the present teachings, the wavelength selective switch 302 includes one or more low frequency photodiodes for directly detecting the encoded control data.

In addition, the wavelength selective switches used in the hardware configured network according to the present teachings are bi-directional and capable of operating equivalently in both directions. Accordingly, one aspect of the present teachings is: the wavelength selective switch 302 is also capable of receiving and decoding control signals from other optical elements in the network, as well as sending and encoding control signals intended for other optical elements in the network.

The hardware configured optical element 300 includes a wavelength selective switch 302, the wavelength selective switch 302 having: at least one optical input optically connected to the receiving optical fiber 304; and a plurality of optical outputs optically connected to the plurality of transmitting optical fibers 306, 306', 306 ". The wavelength selective switch 302 also has an electrical control port 308. In some methods of operation according to the present teachings, the receiving fiber 304 propagates optical signals at one or more wavelengths. Referring back to fig. 2A, 2B, the optical signal may include customer data traffic originating from the tunable optical transceiver 202.

Fig. 3A shows client data traffic 310 on receive fiber 304. One function typically performed by the wavelength selective switch 302 is to vary the attenuation of the received optical signal in response to an electronic control signal and to produce an amplitude modulated signal by varying the attenuation. The results were: the low frequency modulation imposed on the optical signal received at the optical input of the wavelength selective switch 302 can be independently imposed on the optical signal at any or all wavelengths or channels passing through the wavelength selective switch 302.

Fig. 3A also shows a client data traffic 310 with a low frequency control signal 312, the low frequency control signal 312 being in the form of a string of "1" s and "0" s encoded by an electronic control signal. It should be noted that the integrity of the client data traffic 310 is not affected by low frequency control signals. The low frequency control signal is selectively applied on a desired wavelength channel routed to any of the plurality of transmit fibers 306, 306', 306 "using an electronic control signal that selectively controls attenuation of a particular wavelength channel of the wavelength selective switch 302.

The low frequency control signal generated by the wavelength selective switch 302 in the form of a "1" and "0" string 312 can be filtered to eliminate high frequency signals from the customer data traffic, as shown in the oscilloscope trace 350 shown in fig. 3B. FIG. 3B illustrates an oscilloscope trace 350 of the measured output of wavelength selective switch 302 showing a low frequency control signal according to the present teachings. The measured output is measured at the receive fiber 306, where the client data traffic is filtered in accordance with the present teachings. The result is a first signal level of "1" obtained by a low attenuation of the wavelength selective switch 302 and a second low signal level of "0" obtained by a higher attenuation of the wavelength selective switch 302. The data rate of the filtered control signal can be relatively low. For example, the data rate of the low frequency control signal can be about 5 bits/s lower than the client traffic rate.

Figure 4 shows a block diagram of one embodiment of a hardware configured optical amplifier 400 according to the present teachings. In the illustrated embodiment, the hardware configured optical amplifier 400 is an Erbium Doped Fiber Amplifier (EDFA), which is an optical amplifier commonly used in modern optical communication systems. Those skilled in the art will appreciate that many other types of optical amplifiers can be used, including Raman (Raman) and/or Raman/EDFA combinations. Optical amplifier 400 includes an electrical control port 402 configured to send and receive electrical command and control information. In accordance with the present teachings, the optical amplifier 400 further includes: an optical input port coupled to a receive fiber 404, the receive fiber 404 providing an optical signal to be amplified; and an optical output port coupled to the transmit fiber 406, the transmit fiber 406 transmitting the amplified optical signal, which may also include a low frequency control signal.

Fig. 4 also shows an oscilloscope trace of an incoming client data traffic 408 provided by a receive fiber 404 to be amplified by an optical amplifier 400. In this embodiment, the client data traffic 408 is modulated at, for example, a10 Gb/s data rate. The optical amplifier 400 changes the attenuation of the received optical signal and generates a low frequency amplitude modulated control signal 410.

In the embodiment shown in fig. 4, the configuration information is encoded on the low frequency modulated control signal using an electronic control signal provided by the control port 402. The configuration information data in the low frequency amplitude modulated control signal 410 is encoded as a string of "1" s and "0" s using the low frequency modulation imposed on the client data traffic 408, as shown in fig. 4. The integrity of the client data traffic 408 is not affected by the control signal of the low frequency amplitude modulation because the amplitude modulation depth of the low frequency modulation is small relative to the modulation depth of the client data traffic. Additionally, the integrity of the client data traffic 408 is not affected by the low frequency amplitude modulated control signal because the frequency of the low frequency modulation is too low to pass through the receive filter of the client data traffic.

As described herein, one feature of a hardware configured network of the present teachings is: the integrity of the client data traffic 408 is not affected by the small amount of low frequency modulation applied by the optical amplifier 400. In some embodiments, the amplitude modulation applied by optical amplifier 400 provides low frequency modulation for the entire spectral bandwidth of optical amplifier 400. In other words, all channels amplified by the optical amplifier experience substantially the same low frequency modulation. In these embodiments, the same encoded information is received from the electronic control signal through all channels of the optical amplifier 400. However, in other embodiments of the present teachings, the optical amplifier 400 has a gain control that is capable of controlling the gain of a particular channel or band of channels through the optical amplifier 400. In these embodiments, the control signal is encoded on a selected one or more channels, wavelengths, or frequency bands that pass through the optical amplifier 400. In some embodiments, the modulation is encoded by modulating the power of a pump laser that controls the gain of the amplifier 400.

One feature of the present teachings is: the low frequency control signal can be applied to various types of existing optical signals. For the embodiments shown in connection with fig. 1D-1E and 2, the existing optical signal includes client data traffic originating from the transceiver element. In some embodiments, the existing optical signal does not include real-time data traffic. For example, the existing optical signal can include a dummy communication data signal. In other embodiments, the existing optical signal includes the CW output of the optical transceiver or amplified spontaneous emissions from the optical amplifier.

Further, in some embodiments, the existing optical signal originates from the same optical element that imposed the electronic control information on the existing optical signal. In other embodiments, the existing optical signal originates from other optical elements upstream of the optical element that applies the electronic control information to the existing optical signal. In some embodiments, electronic control information from one or more separate elements connected in the network is imposed on the same existing optical signal. In some embodiments, the electronic control port provides configuration information for the light control signal. In some embodiments, a processor in the optical network element provides configuration information for the optical control signal. In some embodiments, configuration information for a transmitted optical control signal provided by a processor in an optical network element is generated based on a received optical control signal.

In one embodiment of the present teachings, the hardware configured optical elements include a counter-propagating raman pump unit and a Variable Gain (VG) optical amplifier, such as a variable gain EDFA optical amplifier. The raman pump unit and the variable gain optical amplifier can be integrated to provide a very low noise figure and excellent gain flatness, which are highly desirable characteristics for ultra-long range optical communication systems. In various configurations, prior art optical amplifier modules are capable of currently supporting up to three raman/EDFA pump optical amplifiers in various configurations.

In embodiments using a raman pump unit and a variable gain optical amplifier, a fast Automatic Gain Control (AGC) circuit can be used to provide a high degree of transient suppression that allows the optical amplifier to keep the gain constant during such operating conditions: there is a rapid and large change in the input power independent of the Amplified Stimulated Emission (ASE) produced by the raman pump optical amplifier. Suitable variable gain two-stage erbium doped fiber amplifiers providing flat gain over the C-band with low noise figure and large dynamic gain range (up to 15dB) are commercially available from Finisar corporation. In some embodiments, the optical amplifier includes various features, such as integrated transient control, tunable intermediate stage access (MSA) loss, and gain tilt functions, all of which may be used together or separately to control attenuation by the device to impose low frequency modulation on an existing optical signal.

One feature of the present teachings is: a hardware configured optical element provides a means for sending configuration information to elements in a network that includes many hardware configured optical elements. The methods and apparatus of the present teachings are compatible with existing deployed optical elements in known networks and can be readily implemented using known low frequency modulation techniques and known methods of information processing. Compatible existing networks include industry standard data communications and telecommunications networks such as large service provider networks and enterprise networks as well as private networks and purpose built network systems such as those used for industrial control. In some embodiments of the present teachings, configuration information or control signals are exchanged between optical elements in a point-to-point manner. In other embodiments, configuration information is exchanged between optical elements in a broadcast manner or a multicast manner for some or all of the optical elements on the network. In other embodiments, the configuration information is exchanged in a multipoint manner or a cascaded manner. In various embodiments, any combination of these ways for exchanging configuration information or control signal information between optical elements can be used.

Another feature of a hardware-configured network comprising hardware-configured optical elements of the present teachings is: known communication protocols and known management information protocols may be used to configure the network elements. That is, known rule systems for collecting information from and configuring network elements can be used. These protocols include data communications, telecommunications transport, and management protocols used, for example, to manage data formats, addressing, routing, error and fault management, traffic and sequence control, and other known management elements and functions. In various embodiments, these protocols include embedded systems, real-time systems, and computer bus protocols.

Figure 5 shows an oscilloscope trace of a low frequency control signal 500 according to the present teachings including a collision avoidance protocol based on a modification of the well known ethernet protocol. The low frequency control signal 500 shown in fig. 5 includes a protocol suitable for multipoint communication. The encoded control information is sent in "bursts" shown as regions 502, 502', where modulated "1's" and "0's" appear on the client data traffic 504. The burst duration, shown as time T506, is small compared to the retransmission time T508. In some embodiments, the ratio of T/T is 0.1, such that the packet time is only 10% of the retransmission time. Each transceiver uses a random percentage of retransmission time for the packet bursts in order to avoid possible collisions of packets transmitted from different transmitters and to improve the reliability of decoding at the receiver. In other words, the T/T of the various transmitters are randomly selected.

One aspect of the present teachings is: the optical elements in a hardware configured network can be arranged in any network configuration, including nets, point-to-point, rings, buses, trees, and other known structures. Additionally, the optical elements of the hardware-configured networks of the present teachings may include several different element types, including transceivers, amplifiers, Optical Channel Monitors (OCMs), wavelength selective switches, Wavelength Division Multiplexing (WDM) multiplexers and WDM demultiplexers, cross-connects, and optical switches. Thus, the configuration system of the present teachings supports a wide variety of network topologies, network sizes and ranges, and network services.

Another aspect of the present teachings is: different combinations of optical network elements (including transceivers, amplifiers, optical channel monitors, wavelength selective switches, multiplexers/demultiplexers, cross-connects, and optical switches) can be configured using common configuration schemes as described herein.

Figure 6 represents an embodiment of a hardware-configured network of the present teachings in a point-to-point transceiver topology (sometimes referred to in the art as an optical link). The point-to-point configuration shown in fig. 6 can be extended to other more complex network topologies (such as mesh, ring, and bus) that include additional optical transceiver components. In the embodiment shown in fig. 6, two optical transceivers 602, 602 'are connected via one optical fiber 604, the optical fiber 604 being used for transmission from the first transceiver 602 to the second transceiver 602'. The second optical fiber 606 transmits information from the second transceiver 602' to the first transceiver 602. In some embodiments, the optical link operates using a coherent optical signal format.

The transceiver 602 includes control ports 608, 608' for sending and receiving command and control information signals. Also on each transceiver 602, 602 'is a port 607, 607' for transmitting and receiving client data traffic. An oscilloscope trace of the measured output of the first transceiver 602 shows normal client data traffic 610 and low frequency control signals 612 at a10 Gb/s data rate. It should be noted that the integrity of client data traffic 610 is not affected by low frequency control signal 612. The low frequency control signal 612 shown in fig. 6 is an amplitude modulated signal, but one skilled in the art will appreciate that any modulation format can be used. The low frequency control signal 612 includes control and management information transmitted from the first transceiver 602. The microprocessor in the second optical transceiver 602' is used to decode the "1" and "0" strings received from the first optical transceiver 602. In this manner, configuration information is shared from the first optical transceiver 602 to the second optical transceiver 602'.

The second optical fiber 606 is used to transmit configuration information from the second transceiver 602' to the first transceiver 602. In this manner, configuration information is shared from the second optical transceiver 602' to the first optical transceiver 602. The control ports 608, 608 'on the first and second transceivers 602, 602' can include an industry standard I2C interface or other type of communication interface. Thus, using the low frequency modulation method of the present teachings, digital diagnostic information can be encoded, shared, and decoded in both directions between the two transceivers 602, 602'. One or the other of the transceivers 602, 602' is not required to communicate with a separate control processor or management system to configure the link as in prior art link configuration systems. In some embodiments, the low frequency modulation is due to tuning of wavelengths in one and/or the other transceiver 602, 602'. In these embodiments, the tuning through the different wavelength channels causes the low frequency detection signal to appear when a signal is detected at the input of the transceiver 602, 602'. The tuning through the wavelength channels occurs during various wavelength channel scans (e.g., slow and fast scans of wavelength channels) described in more detail herein.

A hardware configured link that operates autonomously without requiring communication with a separate management system or controller can be extended to large optical systems. For example, a large wavelength-counting optical link comprising a large number of transceivers may be configured using various embodiments of the methods and apparatus of the present teachings. FIG. 7 shows a scheme involving connection to a wavelengthAn embodiment of a hardware configured network 700 of the present teachings of a plurality of tunable optical transceivers 702, 702' of select switches or optically programmable filter elements 704. As with other embodiments described herein, the transceivers 702, 702' may include client traffic ports. Wavelength selective switches can be used to route optical signals between optical fibers based on a particular wavelength or channel. The wavelength selective switch can be configured as a reconfigurable optical add/drop multiplexer and act as an automated patch panel that quickly moves wavelengths and bandwidths to different fibers. For example, Flexgrid commercially available from Finisar corporation^TMThe technology product provides dynamic control of channel center frequency with 6.25GHz resolution and 12.5GHz channel width resolution within a wavelength selective switch. Using Flexgrid^TMTechniques, once deployed, the channel plan may be configured "on the fly," meaning that: the channel bandwidth can be adjusted to most efficiently support future demands as they arise, or for any other purpose.

One example of a prior art programmable optical filter is the programmable optical processor of the wavesharp family commercially available from Finisar corporation.

Programmable optical filters provide a range of programmable optical filtering and switching, including very fine control of filter characteristics such as center wavelength, bandwidth, shape and dispersion, and attenuation. The programmable optical filter can provide various functions such as tunable optical filtering, optical bandwidth management, dynamic gain equalization, programmable optical filtering, polarization processing, and multiport optical processing). All of these parameters of the wavelength selective switch and the programmable optical filter can be configured using the hardware configured network method and apparatus of the present teachings.

Fig. 7 shows two optical transceivers 702, 702', the two optical transceivers 702, 702' having optical outputs connected to inputs of a programmable filter element 704 with optical fibers 706, 706 '. In some embodiments, the optical connection between the two transceivers 702, 702' and the programmable filter element 704 may be bi-directional. Programmable filter element 704 includes: an output optically connected to output fiber 708; and an electronic control port 710 for receiving electronic control signals. The two optical transceivers 702, 702' have electronic control ports 712, 714 that receive electronic control signals.

In some embodiments, the optical transceivers 702, 702' are tunable and configured to transmit and receive different wavelength channels. In the configuration shown in fig. 7, programmable filter element 704 is programmed to receive two wavelength channels and transmit the two wavelength channels on output fiber 708. Those skilled in the art will appreciate that any number of transceivers having any number of channels can be used with the methods and apparatus of the present teachings.

In some embodiments, the local client 716 is used to provide control information to configure the programmable filter element 704 and set the wavelength channel from the transceiver 702, 702'. In some embodiments, control information is provided independently from an external source using control ports 710, 712, and 714. The control information is encoded on a low frequency control signal that is applied to the existing optical signals propagating on the optical fibers 706, 706', and 708. In this way, information for element configuration is transmitted through the network. In some embodiments, both local client-based input methods and independent input methods are used. In various embodiments, the local client may or may not be co-located with the optical element. In various embodiments, the local client is preprogrammed, for example, to auto-launch components and provide other local control information so that the elements (e.g., the transceivers 702, 702' and/or WSS or programmable filter 704) can operate autonomously without requiring an external management system or controller to launch and/or configure the link.

Figure 8 illustrates an embodiment of a network 800 including a hardware configuration of the present teachings with a wavelength division multiplexed network of wavelength selective switching optical elements. Many known network element configurations rely on the use of a client to communicate configuration information to various elements in a wavelength division multiplexed network using a separate "supervisory" channel. One feature of the hardware configured network of the present teachings is: providing the component configuration eliminates the need for known client hardware. Client hardware and other external management systems can be provided and used in the network, but are no longer required by the element configuration. Furthermore, if these client hardware and other external management systems are used, they can have a greatly reduced role. Alternatively, as described herein, the configuration information is provided via a low frequency control signal that is applied to an existing optical signal in the optical network.

Fig. 8 shows first and second transceivers 802, 802', the first and second transceivers 802, 802' having bidirectional optical ports optically coupled to a add wavelength selective switch 804 using optical fibers 806, 806 '. In some embodiments, there is bi-directional communication between the first and second transceivers 802, 802' and the add wavelength selective switch 804. In other embodiments, there is only one-way communication from the first and second transceivers 802, 802' to the add wavelength selective switch 804. The transceivers 802, 802 'also include control ports 808, 808' that receive control information.

The add wavelength selective switch 804 has an electrical control port 810 that receives control information. In some embodiments, electrical control port 810 is not used and control information is provided via optical fibers 806, 806'. In addition, add wavelength selective switch 804 includes an optical bidirectional port that is optically coupled to a bidirectional port of a drop wavelength selective switch 814 using an optical fiber 812. The sub-wavelength selective switch 814 has an electrical control port 816 that receives control information. In operation, add wavelength selective switch 804 can be configured to controllably connect various wavelengths from various input ports to particular output ports. The sub-wavelength selective switch 814 can also be configured to controllably connect various wavelengths from a particular input port to one or more of various output ports. Those skilled in the art will appreciate that the add wavelength selective switch 804 and the drop wavelength selective switch 814 can also be operated in reverse, such that the add wavelength selective switch 804 becomes a drop wavelength selective switch, and vice versa.

The wavelength division selective switch 814 also includes two bidirectional ports optically coupled to first and second optical fibers 818, 818'. In the illustrated embodiment, optical fibers 818, 818 'transmit the optical signals from the sub-wavelength selective switch 814 to transceivers 820, 820'. Transceivers 820, 820 'have electrical control ports 822, 822'. In the embodiment shown in fig. 8, transceivers 802, 802' transmit to the sub-wavelength selective switch 814 through the add wavelength selective switch 804, transmit to transceivers 820, 820', and transceivers 820, 820' receive signals. With respect to other embodiments described herein, the transceivers 802, 802', 820' may include client data traffic ports.

In the embodiment shown in fig. 8, transceiver 802 at location a 824 is in a transmit mode and optically coupled to transceiver 820, and transceiver 820 is in a receive mode at location B826. Similarly, transceiver 802' at location a 824 is in a transmit mode and is connected to transceiver 820' at location B826, and transceiver 820' is in a receive mode. In one method of operation, the transceiver 802 is configured, at least in part, using the client configuration device 828 to provide data on a particular wavelength channel.

The encoded control information is applied using low frequency modulation on a wavelength channel originating from the transceiver 802, which is sent to the add wavelength selective switch 804. The encoded control information is received by add wavelength selective switch 804, then decoded and used to configure add wavelength selective switch 804 to transmit signals from transceiver 802 to output fiber 812, which output fiber 812 is connected to drop wavelength selective switch 814. This action causes the control signal to pass to the sub-wavelength selective switch 814 where it is then decoded. The sub-wavelength selective switch 814 then uses the decoded control information to configure the sub-wavelength selective switch 814 to transmit the signal from the transceiver 802 to the optical fiber 818. This configuration of the sub-wavelength selective switch 814 thus conveys signals originating from the transceiver 802 and encoded control information to the receiver 820. The encoded control information is received at transceiver 820 and is used to configure transceiver 820 to receive signal data from transceiver 802.

In some embodiments, one or more optical channel monitors 830, 832 provide control information to the hardware configurable add wavelength switch 804 and the drop wavelength switch 814. The optical channel monitors 830, 832 monitor the details of the optical signal passing through the add wavelength selective switch 804 or the drop wavelength selective switch 814, or both, and use this information to inform the hardware configured network of various control actions. The control action is signaled to the network via the low frequency modulation coding described herein. As described above, elements in a hardware-configured network are thus able to automatically configure and/or otherwise manage and control the connectivity of the hardware-configured network.

Those skilled in the art will appreciate that add wavelength selective switch 804 and drop wavelength selective switch 814 are capable of simultaneously running traffic in both forward and reverse directions. However, two fibers between each element are required to propagate traffic in both directions and may be configured for a bi-directional transceiver for client traffic.

Those skilled in the art will appreciate that the particular sequence of events that illustrate the automatic configuration and provisioning of the network of hardware configurations shown in FIG. 8 is illustrative and not limiting of the present teachings in any way. For example, various protocols can be used to establish network connectivity and network configuration between optical elements in various sequences using the low frequency control signals described herein. Further, the client can be used to provide electronic control signals to any element in the network for any or all configuration events. In addition, the client can be used to initiate one or more configuration events, and the automatically encoded information is used for the remainder of the configuration event.

One aspect of the present teachings is: installation errors can be detected in an automated manner without the use of a client or an external network manager. Installation errors deviate the actual deployed hardware physical connections from the planned hardware physical connections. The term "physical connection" is referred to herein as the connection of a particular port of one or more optical elements to a particular fiber or a particular port on an optical element. When a mounting error occurs, a planned configuration of components preprogrammed into optical components physically connected using planned hardware will not result in a proper optical signal path among the components. In known configuration systems, the only way to recover from installation errors is to both detect the erroneous connection and redeploy the hardware using expensive human intervention to establish the planned hardware physical connection.

Fig. 9 shows a network 900 of the hardware configuration of fig. 8, in which the wiring is erroneously installed at location B. The mounting error causes a cross-wiring condition at location B902. The planned wiring connection requires that the receiving transceiver RX-1904 be connected to fiber 906 and that the receiving transceiver RX-2908 be connected to fiber 910. Installer error causes receiving transceiver RX-1904 to connect with fiber 910 and receiving transceiver RX-2908 to connect with fiber 906 as shown in fig. 9. Unfortunately, for telecommunication service providers, such installation errors often occur and cause significant service initiation delays and increased costs. Even with prior art network hardware configured systems, cross-wiring conditions are difficult to detect and difficult to correct. Detecting installation error conditions requires the use of human operators to correlate error conditions of multiple network elements and subsequent service calls performed by field technicians to locate equipment and reconnect the equipment to the planned physical connections. For example, in a system where transceiver ports are intentionally or accidentally swapped to different channels, the different channels of a connection may be identified by the connected transceiver, which may be a client. The filter connected to the client may be determined by polling the connected transceivers. In some embodiments, the detected client data traffic may be used to provide additional troubleshooting information, but frames modulated at low frequencies need to be decoded and compared. A simple low-speed poll through a debug port connected channel will indicate an error.

Using the hardware configured network apparatus and method of the present teachings, the cross-wiring installation error of fig. 9 can be automatically detected and corrected with little human intervention or out-of-vehicle maintenance. Specifically, at the beginning, the sub-wavelength selective switch 912 transmits an optical signal including a low frequency control signal according to the present teachings from the transmitting transceiver TX-1916 at location a914 to the receiving transceiver RX-2908 at location B902. The receiving transceiver RX-2908 at location B902 identifies a connection error because the encoded configuration information on the low frequency control signal is from TX-1916 at location a914 rather than from TX-2918 at location a914 as expected. The receiving transceiver RX-2908 at location B902 then initiates corrective action by encoding the corrective configuration information on a low frequency control signal directed to the appropriate network element in order to provide corrective action that mitigates installation errors.

Specifically, the reconfiguration using the wavelength division selection switch 912 corrects the wiring error. Reconfiguration is initiated by encoded information sent from the receiving transceiver RX-2908 at location B902 to the wavelength division select switch 912 at location B902 to reconfigure the subchannel so that RX-2908 at location B902 receives an optical signal from TX-2918 at location a 914. Thus, sub-wavelength selective switch 912 is reconfigured based on control information transmitted from receiving transceiver RX-2908 so that signals from TX-1916 at location A914 appear on deployed fiber 910 instead of planned fiber 906 and signals from TX-2918 at location A914 appear on deployed fiber 906 instead of planned fiber 908. In this manner, reconfiguration of optical elements in a hardware configured network of the present teachings corrects installation errors without costly human intervention. The extension of other installation errors and the necessary reconfiguration steps are well understood by those familiar with the prior art of network configuration and failure recovery.

One aspect of the present teachings is the ability to: installation errors are captured earlier on the transmitting side of the network, rather than just detecting configuration errors at the receiving end of the network where the signal arrives, as is currently performed in known systems. Fig. 10 shows a network 1000 of the hardware configuration of fig. 8 in which a mounter makes an error in wiring elements at position a 1002. In particular, fiber 1004 from the transmitting transceiver TX-11006 is connected to input 1008 on add wavelength selective switch 1010, input 1008 being actually programmed for fiber transmit receiver TX-21012. In addition, an optical fiber 1014 originating from the transmitting transceiver TX-21012 is connected to an input 1016 on add wavelength selective switch 1010, input 1016 being intended for the transmit receiver TX-11006. In other words, because of installation errors, the connections from the transceivers 1006, 1012 to the add wavelength selective switch 1010 are swapped on the inputs 1008, 1016 with respect to the planned deployment. In this misconfiguration, the add wavelength selective switch 1010, which was initially configured to route signals appearing on the input 1016 from the transmitting transceiver TX-11006, instead receives signals from the transceiver TX-21012 on that port 1016. The encoded configuration information provided on the low frequency control signal detected by add wavelength selective switch 1010 causes this error to be immediately detected within add wavelength selective switch 1010. In some methods of operation, the error can be repaired by having the network of the hardware configuration notify the client or third party manager that the wiring needs to be repaired. In other automatic methods of operation, a hardware configured network automatically reconfigures the transceivers 1006, 1012, or automatically reconfigures the add-wavelength-selective switch 1010. An automatic reconfiguration is initiated based on control information sent to the optical elements that can be reconfigured to repair the error from the optical element that detected the error.

One aspect of the present teachings is the ability to: a low cost multi-transceiver combiner-splitter is provided. FIG. 11 shows an embodiment of a low cost combiner-splitter 1100 that includes hardware configured elements in accordance with the present teachings. The plurality of transceivers 1102, 1102 'are connected to the passive combiner 1106 using a plurality of optical fibers 1104, 1104'. The passive combiner 1106 can include any number of ports. For example, the passive combiner 1106 can be a sixteen-port (16:1) passive combiner. By passive combiner we mean a combiner without filtering capability to filter individual wavelength channels, but in some embodiments some other kind of wavelength filtering may occur in the passive combiner element.

The output of passive combiner 1106 is optically coupled to optical amplifier 1110 using optical fiber 1108. Optical amplifier 1110 is used to overcome the loss of combiner 1106, which is about 13dB for a 16:1 combiner. Optical amplifier 1110 can be a widely available low cost erbium doped fiber amplifier. For example, in one embodiment, the optical amplifier 1110 has a start-up power of 0dBm for each transceiver 1102, 1102' and sufficient amplifier gain to overcome combiner losses so that the output power of the amplifier 1110 is 12 dBm. The output of optical amplifier 1110 is optically coupled to optical splitter-combiner 1114 using optical fiber 1112. The optical splitter-combiner 1114 includes a plurality of optical outputs 1116, 1116 'optically coupled to a plurality of transceivers 1118, 1118'.

In various embodiments, transceivers 1102, 1102 'and transceivers 1118, 1118' operate in a transmit or receive mode. For example, in one method of operation, the transceivers 1102, 1102 'operate in a transmit mode and the transceivers 1118, 1118' operate in a receive mode. In another method of operation, the transceivers 1102, 1102 'operate in a receive mode and the transceivers 1118, 1118' operate in a transmit mode.

Some or all of transceivers 1102, 1102', transceivers 1118, 1118', and amplifiers 1110 are configured using low frequency modulation as described herein. One feature of the hardware configured network of the present teachings is: there is no need to track the fiber order or label a particular transceiver connection because all configuration information can be provided by the low frequency control signal. The configuration information allows for automatic provisioning of the tunable channel and all data connections are established between the transceivers.

One aspect of the present teachings is: the hardware-configured network described herein is capable of providing digital diagnostics for optical network elements. Known transceivers sometimes include a microprocessor and a diagnostic interface that provides performance information about the data link. This allows the user to remotely monitor many performance parameters of any transceiver in the network in real time, such as received optical power, transmitted optical power, laser bias current, transceiver input voltage, and transceiver temperature. The digital diagnostic function provides the user, client and external network management system with tools for implementing performance monitoring.

Some known optical transceivers provide digital diagnostics via a Digital Diagnostic Monitoring Interface (DDMI). The digital diagnostic monitoring interface specifies control information that is communicated to the client or external management system and includes information such as: component identification information, component operating parameters, network and component configuration information, alarm and warning parameters, and vendor information. The Digital Diagnostic Monitoring Interface for small form factor (SFP) optical Transceivers is detailed in the Finisar application notes AN-2030, "Digital Diagnostic Monitoring Interface for optical Transceivers".

Digital diagnostic monitoring interfaces are known that include an interface device or optical transceiver that allows real-time access to device operating parameters and alarm and warning flags that warn a user when operating parameters are outside of normal ranges. Digital diagnostic monitoring interface devices are known to generate diagnostic data by digitizing analog signals monitored internally. Calibration and alarm threshold data are typically written during manufacture of the interface device. In addition to generating digital readings of internal analog values, known digital diagnostic monitoring interface devices also generate various status bits based on comparisons with current values and plant preset values. In addition, digital diagnostic monitoring interface devices are known to generate identifier information.

Another aspect of the hardware configured network of the present teachings is to provide enhanced digital diagnostic monitoring. Some embodiments of the hardware configured network of the present teachings provide digital diagnostic monitoring interface control information as part of the low frequency control signals described herein. In particular, the low frequency control information can include a data field that is part of the low frequency control signal described herein and provides specific information about the transmitter component of the transceiver element. For example, the low frequency information signal can include one or more transmitter serial numbers of transceiver elements comprising the transmitter and/or a transmitter channel identification number of a particular transceiver element. The transmitter channel identification number provides the wavelength and/or channel number to which the laser transmitter is tuned. The low frequency information signal described herein can also include information about the receiver component of the transceiver element. For example, the low frequency information signal can include one or more receiver serial numbers of transceiver elements that comprise the receiver and/or a receiver channel identification number of a particular transceiver element.

Another aspect of the hardware configured network of the present teachings is: it is capable of providing enhanced digital diagnostics by exchanging configuration information with elements such as transceivers, amplifiers, wavelength filters, optical channel monitors, wavelength selective switches, wavelength multiplexers, wavelength demultiplexers, cross-connects, and optical switches. The enhanced digital diagnostic information is used as control information encoded on the light control signal of the present teachings. The use of the optical control signals of the present teachings provides additional flexibility in the ability to reach various optical elements in a hardware configured network by selecting the appropriate optical carrier as compared to prior art configuration systems. In some embodiments of a hardware-configured network of the present teachings, the hardware-configurable element comprises a photodiode that decodes the low frequency control signals described herein.

Those skilled in the art will appreciate that hardware configurable elements in accordance with the present teachings can be used for a variety of purposes. For example, in some embodiments, a hardware configurable optical amplifier can be used for network discovery configuration prior to transceiver transmitter operation. Further, in some embodiments, the hardware configurable amplifier may be configured to have an optical gain that depends on the optical path noise calculation. Further, in some embodiments, the hardware configurable amplifier gain profile is adjusted based on the channel start of the remote transceiver. Further, in some embodiments, the hardware configurable amplifier can send information about the optical gain to the transceiver.

Further, in some embodiments, the hardware-configurable wavelength selective switch ports are configured and reconfigured as needed with flexible channel planning based on data traffic. Furthermore, in some embodiments, a hardware configurable wavelength selective switch is used to provide network protection against faults by reconfiguring optical paths in the network after a fault. Further, in some embodiments, the hardware-configurable optical programmable filter automatically adjusts path dispersion based on performance information provided by the hardware-configurable transceiver element without user or external network management intervention.

Further, in some embodiments, the low frequency control signal described herein is used to calibrate a hardware configurable optical channel monitor. Referring to fig. 8, by adding sophisticated channel monitors 830, 832 and using enhanced digital diagnostic control information in a hardware configured network of the present teachings, the transceivers used in the network can be tuned and more closely spaced for higher overall optical transmission rates and spectral efficiency.

One feature of the present teachings is that a hardware configured network element according to the present teachings can be configured without using an amplitude modulated control signal on the optical carrier. In particular, changes to the optical carrier may be utilized, the changes being simply generated by actions taken during the configuration protocol. These changes in the optical signal based on protocol-driven actions in the control processor are recognized at the appropriate downstream devices or elements as part of the network configuration, and information derived from these changes recognized in the optical signal is used to close the configuration loop for the particular predetermined configuration. For example, the fact that the transmitter is on and/or the duration of the transmitter's on time and/or power level may be monitored and determined at one element (e.g., a downstream receiver). The determined status of the transmitter and the monitored optical signal derived by the downstream receiver are then used as part of the information to manage and control the network. For example, a network may include a sender, a receiver, and one or more elements connecting the sender and the receiver. Any of the downstream elements of the transmitter may monitor for changes to the optical carrier generated by the configuration change.

The benefit of constructing the configuration protocol from signals due only to configuration changes of the elements themselves is that framing, additional traffic bandwidth, or complex control signaling or encoding of the optical signals for configuration is not required. The change in the optical signal caused by the normal function of a particular element (e.g., turning on or off or changing wavelength) is independent of any framing, traffic, or other modulated control signal. In case of switching on or off the transmitter, only the presence or absence of light may be needed to control the channel switching and configuration. In embodiments where the transmitter is a tunable transmitter, the signals may be changed as fast as the tuning speed of the transmitter. As such, the network of hardware configurations may change and/or determine its operational state and approach the final configuration very quickly.

Figure 12A shows a block diagram of an embodiment of a hardware configurable link 1200 including a hardware configured tunable transceiver according to the present teachings. Link 1200 may operate bi-directionally, but only a single direction is represented. Two transceivers 1202, 1204 are shown transmitting at the near end of the link 1200. Each transceiver 1202, 1204 generates an optical signal on an optical carrier at a particular wavelength channel. The outputs of the transceivers 1202, 1204 are input to a WDM combiner 1206 and transmitted over a delivery fiber 1208 to the far end of the link. The fiber connections between the transceivers 1202, 1204 and the WDM combiner 1206 can be relatively long, in some embodiments up to 2km long. The signal from the delivery fiber 1208 is split at a WDM splitter 1210 and the different wavelength channels are sent to specific transceivers 1212, 1214 that receive the optical signal on a specific channel based on the WDM configuration. Transceivers 1202, 1204, 1212, 1214 are thus interconnected with low cost WDM splitter 1210 and combiner 1206. One feature is that the particular order of the connecting fibers 1216, 1218, 1220, 1222 need not be tracked in order to configure the link 1200. Tunable channels may be provisioned and connections and traffic between the transceivers 1202, 1204, 1212, 1214 may be established without additional optical channels for control. In some embodiments, the transceivers 1202, 1204, 1212, 1214 are tunable coherent transceivers.

Figure 12B shows a block diagram of an embodiment of a transceiver according to the present teachings that may be used with the hardware configurable link described in conjunction with figure 12A. The transmitter 1232 and receiver 1234 are controlled by a processor 1236. The transmitter 1232 is connected to transmit optical fibers 1238 and the receiver 1234 is connected to receive optical fibers 1240. In some embodiments, the transmit fiber 1238 and the receive fiber 1240 are connected to a WDM multiplexer/demultiplexer that may be collocated with the transceiver 1202 or remotely located.

An embodiment of a control protocol according to the present teachings that may be used to configure the hardware configured links of figures 12A-B is as follows. At power up, in the near-end transceiver 1202, the transmitter in the transceiver 1202 turns on and begins a slow channel change. In this slow scan, the transmitter produces an optical signal that sequentially steps through all channels in the system. Each wavelength channel is transmitted using dwell (dwell) time on a particular wavelength channel. Dwell time is the time in the scan of a channel in which the transmitter produces a wavelength for a particular channel. Each complete scan includes transmitting from a transmitter with dwell time on each channel of the wavelength of the system. The system typically starts scanning at the first wavelength channel, but in some cases other orders are used, and/or scanning may start at the next channel after the last channel transmitted. This occurs, for example, if the scan is interrupted for some reason. Some embodiments include a gap between dwell times on particular wavelength channels, while some embodiments operate with nominally no gap between dwell times on particular wavelength channels. The receiver at remote transceiver 1212 waits for a signal. A signal, for example, will be detected when a portion of a signal generated by transceiver 1202 that includes a slow scan is detected in transceiver 1212. In various embodiments, a receiver in transceiver 1212 may determine the state of transceiver 1202 on the other side of the link based on the duration of the received signal as described herein.

When the receiver at the far-end transceiver 1212 senses an optical signal from the near-end transmitter because the transmitter at the near-end transceiver 1202 has tuned to the correct channel, the transmitter in the far-end transceiver 1212 enters a fast scan mode. In a fast scan, the transmitter generates an optical signal that sequentially steps through all channels in the system. Each wavelength channel is transmitted with a dwell time on the particular wavelength channel. For fast scans, these transmissions may be referred to as short pulses. The duration of the dwell time on a particular wavelength channel is much shorter than the duration of the slow scan dwell time on a particular wavelength channel because the fast scan is timed to completely traverse the wavelength channels in the scanning system in less time than the single channel dwell time of the slow scan wavelength channel. That is, the overall channel scan time for the fast scan is the same duration as the dwell time on the particular wavelength channel for the slow scan or a shorter duration than the dwell time on the particular wavelength channel for the slow scan. The fast tuning of the transmitter channel in the far-end transceiver 1212 in the fast scan makes it possible to connect the link back to the other end because the receiver in the near-end transceiver 1202 senses the signal from the far-end fast-tuned transmitter when the wavelength is tuned to the appropriate channel. That is, the transceiver 1202 detects a short duration signal, the duration of which is nominally equal to the dwell time on the particular channel of the fast scan. The near-end transceiver 1202 remains tuned to the channel it is transmitting when sensing a signal from the far-end fast-tuned transmitter, as that channel is suitable for connection to the far-end receiver. The near-end transceiver 1202 may now use the current operating wavelength-channel to transmit traffic over the link. The receiver in remote transceiver 1212 may be used to initiate any subsequent configuration including, for example, setting up of the link in the reverse direction. The link setup protocol may work in either direction. Although the block diagram of the transceiver 1202 of fig. 12A represents a transceiver transmitter and receiver, each connected to separate transmit and receive fibers, it is straightforward for those skilled in the art to apply the protocol to many types of bi-directional transceivers and fiber connections.

In some embodiments, the transceiver only needs to detect and determine dwell times from a particular wavelength of the slow scan to be able to complete link setup and transmit customer traffic through the link, depending on the particular application, other scan speeds and wavelength accuracies may be used, in some basic embodiments, the transceiver only needs to detect and determine dwell times from a particular wavelength of the slow scan, and detect and determine dwell times from a particular wavelength of the slow scan to be able to complete link setup and transmit customer traffic through the link, in some embodiments, the transceiver only needs to detect and determine dwell times from a particular wavelength of the slow scan to be able to maintain a particular power on state of the transceiver, and the transceiver may be powered on and off using a particular laser on state, which is typically a short dwell time on state, and a short dwell time on state, such that the transceiver may be powered on and off at a short dwell time on channel on state.

FIG. 13 shows a graph 1300 showing optical power as a function of time for an embodiment of a set of transmitter states 1302, 1304, 1306, 1308 of the present teachings TX _ S L OW _ TUNE 1302 traverses the state tuning where power is transmitted in channel 11310, then in channel 21312, and so on until transmitted in channel 401314, then starting again at channel 11316. TX _ S L OW _ TUNE 1302 is an embodiment of a slow scan of wavelength channels. each channel generates power in about one second.

Some embodiments of the protocol of the present teachings that configure hardware configurable links use a limited set of possible receiver states. These include RX _ ON, where the power measured by the receiver is determined to be greater than a certain threshold in greater than 8 milliseconds. In some embodiments, the threshold is a power threshold and is the same as the power threshold of the receiver for the protection event. In some embodiments, the threshold comprises a duration threshold, and the power-up duration is determined to exceed the threshold when the duration is determined to be greater than a particular duration. In some embodiments, the power-on duration is determined to exceed the threshold when the duration is determined to be less than a particular duration. The state RX _10MS is a state in which the receiver determines that it has received light for a period greater than 8 MS. RX _1SEC is a state where the receiver determines that it has received light for a period greater than 1 s. RX _ BEACON is a state where the receiver determines that it has received light on for a duration of 0.5s and then light off for a duration of 0.5 s. The duration for the various receiver states may be different in different embodiments. In general, it is important that the receiver be able to distinguish between a long duration optical on state, a short duration optical on state, and an optical on/off state to implement embodiments of the link configuration protocol.

One feature of the present teachings is that a bi-directional link configuration protocol can be established without the need to implement two unidirectional setup protocols. For example, to enable multipoint communication to a particular receiver in a bidirectional mode, some embodiments of the present teachings utilize the following algorithm. Note that this algorithm description assumes that transceiver a is located at the near end of the link and includes transmitter a and receiver a. Transceiver B is located at the far end of the link and includes a transmitter B and a receiver B. The algorithm proceeds as follows: (1) after power up, transmitter a turns on to start on channel 1 of the particular channel plan; (2) transmitter a lingers for one second on channel 1 and progresses through the channel change at a rate of 1 second/channel (in other words, transmitter a produces a slow scan with a dwell time on a particular wavelength channel that is greater than the duration of the full channel scan of the fast scan, which is described in more detail in step 5); (3) when transmitter a tunes to a channel that arrives at receiver B over the link connection (so receiver B detects a portion of the first optical signal transmitted over the link, the detected light having a duration of the dwell time of the particular channel being scanned slowly), transceiver B (the far-end receiver) receives power; (4) the remote transmitter B enters a fast tuning channel 1-N (e.g., N-40); (5) the remote transmitter B goes through all N channels for fast tuning (in other words, the transmitter B generates a fast scan in which all channel scans are scans through all N channels of the system); (6) when sender B tunes to the channel that arrives at receiver a, receiver a detects light from sender B during fast channel tuning (in other words, receiver a detects light pulses with a duration equal to or less than the dwell time on the fast-scanned particular wavelength channel); (7) transmitter a enters a hold condition on the channel currently being transmitted to receiver B; (8) sender a enters beacon mode; (9) receiver B detects the beacon from transmitter a; (10) the transmitter B enters slow tuning; (11) receiver a detects a slow channel change from light from transmitter B; (12) sender a goes to hold; (13) receiver B detects a state transition from sender a, beacon-to-hold; (14) transmitter B enters a hold condition; (15) the bi-directional linking is completed. Transceiver a and transceiver B may then transmit client traffic bi-directionally.

The sequence is performed without a predetermined specific framing or ordering at the far-end or near-end transceiver. Further, no channel is predetermined. As such, the system is completely self-configuring and setup completely independent of the particular fiber optic connection pattern established when the system is routed. The transceivers are able to discover each other and establish a link without predetermined setup configuration information.

FIG. 14 shows a graph 1400 of optical power as a function of time for a set of transmitter and receiver states that exist during an embodiment of a method of a connection protocol according to the present teachings, in which a near-end transceiver is hardwired to a far-end transceiver through a WDN combiner and splitter such that channel 3 is a connection channel, the graph represents a transmit optical signal 1402 generated by the near-end transmitter, a receive optical signal 1404 received at the far-end receiver, a transmit optical signal 1406 generated by the far-end transmitter, a receive optical signal 1406 received at the near-end receiver, a near-end transmitter is turned on and a TX _ S L OW _ TUNE state 1410 is initiated to begin tuning up from channel 1 at a rate of one second per channel, generally, as shown, if entering state 1424, there is no need to resume at channel 1, in some embodiments, a slow scan is instead continued from the last channel transmitted over the link, a transceiver 1412 is caused to be detected at a far-end transceiver 1413, a transition is caused to be detected at a far-end transceiver 1423, a TX channel sync, a TX BEACON link is caused to be detected, and a BEACON link is caused to be processed by a transceiver 1413, a transceiver on a transceiver on transceiver on transceiver, a BEACON transceiver on a channel 1423.

Thus, in some embodiments, the reverse direction of the link is set autonomously by the near-end transceiver generating a beacon signal and transmitting it to the far-end transceiver over the WDM optical transport interconnect, without the use of separate control signaling. A remote transceiver receives a portion of the beacon signal. This causes the remote transceiver to generate a wavelength channel scan in response to receiving the transmitted beacon signal. In some embodiments, the wavelength channel scan is a slow scan, which may be a rate of one channel per second. The near-end transceiver receives a portion of the optical signal generated by the far-end transceiver when the channels through the WDM interconnect are tuned. When the processor in the near-end transceiver determines that the received portion of the signal exceeds the threshold, it generates a hold signal at the near-end transceiver. That is, the near-end transceiver is caused to generate a continuous-time signal at the current operating wavelength, rather than previously turning the beacon signal on and off. The hold signal is detected by the remote transceiver and based on the power and/or duration of the received signal being determined to be hold, the processor in the remote transceiver then sets the operating wavelength of the remote transceiver to maintain its current operating wavelength. Real-time traffic is then transmitted from the remote transceiver at the current operating wavelength. The operating wavelength of the signal from the near-end transceiver to the far-end transceiver may be the same as, or may be different from, the operating wavelength from the far-end transceiver to the near-end transceiver. The wavelength depends on the wavelength channel passband of the WDM interconnect connecting the near-end transceiver to the far-end transceiver.

In some embodiments, once the near-end transceiver enters the hold state 1418, the near-end transceiver begins sending real-time traffic to the far-end transceiver and does not transition to the TX BEACON state 1420.

In some embodiments, the transceivers on both sides of the link run the same state machine and start to initiate slow scan after power up. There is no need for a master or slave side, only one controller software. In these embodiments, it depends on which side hits the filter first. For a system so implemented, taps are added for the case where both sides of the low probability case are tuned to the appropriate filters simultaneously. The transceiver then restarts at a random time greater than the slow scan rate.

Figure 15 represents a flow diagram of an embodiment of a protocol for establishing a link using a hardware-configured transceiver element of the present teachings. The transceiver may operate in various modulation formats, including coherent modulation formats. The transceiver receiver may comprise a coherent receiver. The transceivers may include SFP, SFP + and/or CFP2/CFP4 transceivers. In some embodiments, the near-end transceiver is hardwired to the far-end transceiver through the WDM combiner and splitter to enable one particular channel to pass through the link from the near-end transceiver to the far-end transceiver in one pass to establish a connection channel for the unidirectional connection. Also, in these embodiments, a particular channel can be passed one-way through the link from the far-end transceiver to the near-end transceiver to establish a connection channel for the unidirectional connection. Note that these channels may be the same, or they may be different. The particular connection channel is not necessarily known prior to startup. That is, no special attention has to be paid to the hardwired fiber configuration in order to know in advance what channels will connect the near-end transceiver with the far-end transceiver and vice versa. In other embodiments, the transceivers may be hardwired through a passive splitter combiner so that multiple channels may be passed between transceivers on a link. One advantage of the apparatus and methods of the present teachings is that the configuration of the network and/or link is accomplished without external human or administrative system intervention and relies on a configuration protocol based on signals that are caused only by configuration changes of the elements themselves. That is, the configuration protocol in the methods and apparatus of the present teachings relies on the low frequency modulation control signal imparted on the optical carrier by the optical elements of the network being configured in hardware.

At step 11502, the near-end and far-end transceivers are optically powered up. Generally, one or more transceiver pairs may be powered up. At step 21504, one of the transceivers, transceiver 1 (which may be referred to as the near-end transceiver without loss of generality), begins a slow wavelength scan as described herein. At step 31506, transceiver 2 (which may be referred to as a far-end transceiver without loss of generality) detects the power. Transceiver 2 is able to distinguish that the detected power is caused by the near-end transceiver by appropriate processing of the received signal, so step 41508 is initiated from transceiver 2, step 41508 is a fast scan of the transmitter. Light from the signal generated in the fast scan of transceiver 2 at step 41508 arrives at transceiver 1, which results in step 51510, transceiver 1 receiver detecting the channel power. In various embodiments, the receiver in transceiver 1 is able to distinguish that the detected channel power is caused by the light generated in the fast scan of transceiver 2 at step 41508. The system then moves to state 61512 where the transceiver remains on the current channel in state 61512. Client data traffic may flow over the link.

It should be appreciated that the steps of a protocol for connecting a near-end transmitter to a far-end transmitter according to the present teachings may operate in either direction, from near-end to far-end and from far-end to near-end. Further, the various steps may be operated simultaneously or separately in time, so long as the present teachings remain operable.

One feature of the present teachings is the ability to deploy a multi-wavelength optical delivery system using multiple tunable transceivers that all have the same part number. For example, many prior art systems require transceivers having different wavelengths and/or pairs of transceivers intended to be used together in a link to be tracked separately. By using a hardware configured network transceiver in accordance with the present teachings, all operational benefits of a single part number are realized by the service provider, including ease of deployment without tracking individual parts, less on-hand inventory, and remote configuration of wavelengths without prior knowledge of how the device is hardwired. For example, the wavelength of the wavelength tunable transceiver is not manually set by the technician, nor is the technician required to select an appropriate fixed wavelength transceiver. A technician may place a hardware configurable transceiver into any host port and connect a duplex jumper to any fiber port on a WDM MUX/DEMUX (WDM multiplexer/demultiplexer). This eliminates the need to track the fiber from the WDM MUX/DEMUX to the transceiver. The client may then poll the transceiver's channels and create a connection map based on the channels that have been set in the link. In some embodiments, the remote transceiver may be positioned up to 2km from the fiber drop box.

FIG. 16 represents a graph 1600 of a measured optical signal for an embodiment of a method of configuring an optical link using a hardware-configured transceiver according to the present teachings graph 1600 includes an oscilloscope trace 1602 as a function of time for the optical output of a coherent transceiver being tuned across channels 30, 31, 32, 33, and 34 graph 1600 includes an oscilloscope trace 1604 of the output of an optical demultiplexer that delivers channel 32, oscilloscope trace 1604 showing that light appears when the coherent transceiver is tuned to channel 32 graph 1600 includes an oscilloscope trace 1606 of a signal loss (L OS) indicator showing that L OS becomes low (L OS 0) when a signal that has successfully passed through the demultiplexer appears at the receiver because the transmitter has been tuned to channel 32.

Figure 17A shows a top view 1700 of a hardware-configured transceiver of the present teachings. Fig. 17B shows a bottom view 1750 of the hardware configured transceiver of fig. 17B. The hardware configured transceivers of the present teachings can be fabricated in a variety of packages including SFP, SFP + or XFP specifications. Alternatively or additionally, the hardware-configured transceiver of the present teachings may be a CFP2/CFP4, coherent transceiver. Figure 17C shows a top view of another embodiment of a hardware-configured transceiver according to the present teachings. Specifically, fig. 17C shows a top view of a CFP4 specification hardware configured transceiver 1780. In some embodiments, the hardware configured transceiver is electronically tuned to 1 of the 88 different wavelengths. In various embodiments, various numbers of channels are included in the system, including 88 channels, 96 channels, 16 channels, four channels, and various other channel counts. These channel wavelengths may represent particular channels on the ITU grid. In some embodiments, the link distance that can be achieved with a hardware-configured transceiver of the present teachings is up to 80 km. Further, in some embodiments, the operating temperature range is from-5C to 85C. In some embodiments, the operating temperature range includes a lower range of-40C or lower.

Figure 18 shows a schematic diagram 1800 of an embodiment of the opto-electronic components in a hardware configured transceiver of the present teachings. The tunable laser 1802 semiconductor optical amplifier 1804 and the Mach-Zehnder modulator 1806 are positioned on a monolithic substrate 1808. Tunable laser 1802 may include a narrow linewidth laser suitable for coherent transmission using a coherent modulation format. The Mach-Zehnder modulator 1806 may be an InP Mach-Zehnder modulator. The Mach-Zehnder modulator may be a silicon photonic modulator, which is also referred to as a SiP modulator. The Mach-Zehnder modulators 1806 may comprise low-power, compact integrated InP IQ modulators for coherent transmission. The output of the Mach-Zehnder modulator 1806 is coupled to an optical element 1810, the optical element 1810 including collimating optics and an optical isolator. The optical element is coupled to the power monitor and wavelength locker element 1812. These elements are all placed on a thermoelectric cooler 1814. The power monitor and wavelength locker element 1812 may be configured to support tunable coherent transmit operations from a hardware configured transceiver. The power monitor and wavelength locker element 1812 is coupled to a lens 1816, the lens 1816 being attached to a receptacle 1818.

One feature of the hardware-configured optical elements of the present teachings is that large networks can be self-configured quickly without any intervention from host equipment or network management systems. The hardware configured elements may act autonomously and may be able to configure themselves based on predetermined information stored in memory devices residing within the hardware configured elements. The firmware routine for configuration is self-contained in the network element. In various embodiments, the routine enables the use of two fiber configurations for duplexing, or for configuring a bidirectional single fiber connection, or both. In some embodiments, the firmware routine is initiated when the device is powered up.

Figure 19A shows a schematic diagram of an embodiment of a WDN delivery system 1900 including a hardware configured transceiver of the present teachings. The proximal twenty hardware-configured transceivers 1902 are each connected to a WDM multiplexer/demultiplexer 1904 using two optical fibers 1906, 1908, one for each direction. The output of multiplexer 1904 is connected to one end of optical fiber 1910. The length of the optical fiber 1910 may be many lengths. In some embodiments, the optical fiber 1910 is 80km long, and may be longer. In some embodiments, the optical fiber 1910 is about 18km long, and may be longer. In some embodiments, the optical fiber 1910 is less than 18km long. The other end of the fiber 1910 is connected to the input of a remote WDM multiplexer/demultiplexer 1912. The output of the WDM multiplexer/demultiplexer 1912 is connected to twenty hardware-configured transceivers 1914 at the far end, one fiber per direction, using two optical fibers 1916, 1918. The term WDM transport optical interconnect as used herein refers to a connection between a transceiver at the near end and a transceiver at the far end of an optical link configured in accordance with the present teachings in hardware. The WDM transport optical interconnect extends from the input of the near-end WDM multiplexer/demultiplexer 1904 to the output of the far-end WDM multiplexer/demultiplexer 1912. The WDM transport optical interconnect may include various optical components including optical amplifiers and performance monitoring devices. Various embodiments of WDM transport system 1900 use various types of optical transceivers 1902, 1904. Some embodiments use a coherent transceiver of the CFP2 specification. Some embodiments use a T-SFP + transceiver. Some embodiments use a transceiver mixing type.

In some embodiments, at least some of the optical fibers 1906, 1908, 1916, 1918 are approximately 2km long, the configuration is also referred to as a "remote PHY" configuration, remote PHY is an emerging industrial specification that applies to cable headend applications, but also to wireless and wired communication applications (including Wi-Fi, L TE, various types of Passive Optical Networks (PONs), and other telecommunication fiber optic network applications). remote PHY refers to an architecture that moves a physical layer transceiver element (also referred to as PHY) out of a traditional access point to place it closer to a network endpoint or end user.

FIG. 19B is a schematic illustration of the WDN delivery system 1900 of FIG. 19A in a state of an embodiment of a setup protocol of a hardware configuration according to the present teachings. The transmitter of the near-end transceiver 1920 slowly scans the wavelengths, which may be ITU wavelength channels. The slow scan duration may be approximately one second per channel. The slow scan duration is set to provide a time sufficient for the receiver at remote transceiver 1922 to detect the light and determine that its incoming link is on. The receiver at the far-end transceiver 1922 will only receive light having the appropriate channel wavelength to pass through the WDM multiplexer/demultiplexer 19041912. For example, if transceiver 1920 is connected to a WDM multiplexer/demultiplexer 1904 port for ITU 20 and the transceiver is transmitting channel ITU 18, the light is blocked 1924 at WDM multiplexer/demultiplexer 1904. A far-end transceiver 1924, which expects to receive light from a near-end transmitter 1920, is connected to the ITU 20 port of the WDM multiplexer/demultiplexer 1812.

FIG. 19C shows a schematic view of the WDN delivery system 1900 of FIG. 18A in another state of an embodiment of a setup protocol of a hardware configuration according to the present teachings. Figure 19C shows that the slow-tuning near-end transceiver 1920 is tuned to the channel ITU 20. This means that light from near-end transceiver 1920 passes through WDM multiplexers/ demultiplexers 1904, 1912 and passes to far-end transceiver 1924. Thus, when the near-end transceiver 1920 wavelength is matched with the WDM multiplexer/demultiplexer 1904 port, the wavelength travels all the way through the network to the far-end transceiver 1924. Thus, the far-end transceiver 1924 detects a portion of the first optical signal transmitted over the link by transceiver 1920 having a duration of the dwell time of the particular channel being scanned slowly. Once the remote transceiver determines that it is receiving light above a certain power threshold, it initiates a fast-tuning optical power sequence from the transmitter at remote transceiver 1924. The power threshold in some embodiments is a signal loss received power value. The fast-tuning optical power sequence in some embodiments is a step-wise increment of each wavelength channel with a dwell time of 10ms on each channel.

FIG. 19D depicts a schematic view of the WDN delivery system 1900 of FIG. 19A in another state of an embodiment of a setup protocol of a hardware configuration according to the present teachings. The transmitter of remote transceiver 1924 may produce a fast scan of wavelengths. The transmitter of the remote transceiver 1924 rapidly scans the sequence of wavelengths, which may be the wavelengths of the ITU wavelength channels. The dwell time on any one channel in the scan is referred to as the fast scan duration. In some embodiments, the fast scan duration is about 10 milliseconds per channel. The snapshot of fig. 19D indicates that the transmitter is generating illumination under channel ITU 18 that will not pass through a port of the delivery channel ITU 44.

Fig. 19E shows a schematic view of the WDN delivery system of fig. 19A in another state of an embodiment of a hardware configured setup protocol of the present teachings. The fast-tuning transmitter in the far-end transceiver 1924 hits channel ITU 44, and channel ITU 44 passes through the port of WDM 1912 and the port of WDM 1904 to be received at the receiver of the near-end transceiver 1920. Thus, the wavelength of the far-end transmitter matches the wavelength for both ports, and the light travels all the way through the network to the near-end transceiver 1920. Thus, the near-end transceiver 1920 detects light pulses having a duration equal to or less than the dwell time on the particular wavelength channel being rapidly scanned. At this point, both transceivers 1920, 1924 may lock their transmit wavelengths and begin normal operation, including passing real-time client traffic. In other words, the transceiver maintains the respective transmitter at the current operating wavelength to complete the bidirectional link and initiate communication.

Each of the twenty hardware-configured transceivers 1902 connected to the near end of twenty hardware-configured transceivers 1914 over a WDM interconnect, including optical multiplexers 1904, 1912 and optical fiber 1910, may be configured using various embodiments of the methods of the present teachings. For example, a transceiver pair may be configured using two unidirectional protocols as described in connection with fig. 12A-B, or a transceiver pair may be configured using a single bidirectional protocol as described in connection with fig. 14. In addition, some transceivers may be configured by using a look-up table containing data on which wavelength channel the WDM interconnect will communicate in each direction between a particular transceiver pair. In embodiments using a look-up table, the wavelength is tuned directly to the predetermined channel and a connection is immediately established between the transceivers at the near and far ends of the link. The use of such a look-up table for establishing operating wavelengths for transmitting real-time traffic between transceivers will speed up the connection time for configuring the link. The use of lookup tables may be performed for any or all of the unidirectional and/or bidirectional link settings in a multi-transceiver WDM system. For example, in some embodiments, a look-up table may be available with data regarding some, but not all, of the wavelength channels communicated over the connection of the WDM interconnect between a particular near-end/far-end transceiver pair.

It is a feature of the present teachings that the link for the hardware configured optical element may be an amplified link. In some embodiments with high loss and/or long haul optical fiber links, optical gain and/or compensation for fiber dispersion (including chromatic dispersion) is required. In addition, control, monitoring, and troubleshooting of the WDM network may be desirable for one or all of the channels. Fig. 20 shows an embodiment of a remote PHY subsystem 2000 having the gains of the present teachings. The package 2002 supports two remote PHY links in a1 RU. The package 2002 supports optical gain, a compact high resolution Optical Channel Monitor (OCM), and can provide performance monitoring at each wavelength. In some embodiments, the remote PHY subsystem 2000 may support fiber transport links up to 60km in length.

Figure 21 shows a schematic diagram of a WDN delivery system with gain utilizing the elements of the hardware configuration of the present teachings. The elements of the hardware configuration may be configured in a remote PHY configuration. Remote PHY systems typically separate transceiver devices from multiplexing and link technologies by relatively long fiber optic links, as opposed to having them in the same box. This allows transceivers to be deployed at locations remote from multiplexing and link technologies. The proximal twenty hardware configured transceivers 2102 are connected to a WDM multiplexer/demultiplexer 2106, the WDM multiplexer/demultiplexer 2106 being remotely connected to the transceivers 2102 using two optical fibers 2108, 2110 (one for each direction) for each transceiver 2102. The optical fibers 2108, 2110 are typically 2 kilometers long, but may be longer in some systems. The output of the WDM multiplexer/demultiplexer 2106 is connected to a first WDM 2112. The output of the first WDM2112 is connected to an optical amplifier 2114. The output of the optical amplifier 2114 is connected to a second WDM 2118. One output of the second WDM2118 is connected to a second optical amplifier 2120, which second optical amplifier 2120 is connected back to the first WDM 2112. The other output of the second WDM2118 is connected to a splitter which sends some light to a high resolution optical channel monitor 2124. The high resolution optical channel monitor controls the two optical amplifiers 2114, 2120 to maintain a high quality optical signal on each wavelength channel. The second output of the splitter is connected to a delivery fiber 2126. In some embodiments, the delivery fiber 2126 is about 58km long, but in other embodiments it may be longer. The other end of the delivery fiber 2126 is connected to the input of a remote WDM multiplexer/demultiplexer 2128. The output of the WDM multiplexer/demultiplexer 2128 is connected to the remote twenty hardware-configured transceivers 2130 using two optical fibers 2132, 2134 (one fiber in each direction). In some embodiments, at least some of the optical fibers 2132, 2134 are approximately 2km long, but in other embodiments may be longer.

Another feature of the present teachings is that it can be configured for different network applications. For example, the hardware-configured network elements of the present teachings may be configured for typical telecommunication service provider network configurations. Alternatively, the hardware-configured network elements of the present teachings may be configured for typical data communication service provider network configurations.

FIG. 22A represents an embodiment of a remote PHY system 2200 using a hardware configured network element of the present teachings configured for a telecommunications application FIG. 22B represents an embodiment of a remote PHY system 2250 using a hardware configured network element of the present teachings configured for a data communications application in some embodiments, a remote PHY system 2200, 2250 includes front to back cooling in some embodiments, a remote PHY system 2200, 2250 has a dual redundant hot swap power supply accessible from a back panel, the power supply may be either AC or DC in some embodiments, a remote PHY system 2200, 2250 includes a dual redundant hot swap fan unit accessible from a back panel 2252250 in some embodiments, a remote PHY system 2250 has a 1U specification with a depth of 450 mm. in some embodiments, a remote PHY system 2200, 2250 includes a front panel that has no front connectors and is capable of supporting approximately one hundred L C type connectors.

Fig. 23A shows an embodiment of a front panel 2300 of a remote PHY system using a hardware configured network element of the present teachings. The remote PHY system may support two remote PHYs. Front panel 2300 includes primary and secondary line ports 2302. The secondary line port is optional. Including monitor port 2304. The first remote PHY includes forty multiplexer/demultiplexer ports 2306. Further, there are forty multiplexer/demultiplexer ports 2308 for the second remote PHY.

Fig. 23B shows an embodiment of a backplane 2350 of a remote PHY system using a hardware-configured network element of the present teachings. There are dual redundant heat exchange fan units 2352, 2354. Each fan unit comprises two fans. There are dual redundant hot swap power supplies 2356, 2358.

FIG. 24 shows a schematic diagram of the functional blocks and layout of an embodiment of a remote PHY system that supports two remote PHYs using a hardware configured network element of the present teachings. The multiplexer/demultiplexer ports 2402 on the front panel support first and second remote PHY connections. The remote PHY system includes fan units 2404, 2406 and two power supplies 2408, 2410. There are two dual optical amplifiers 2412, 2414, which may be Erbium Doped Fiber Amplifiers (EDFAs). There is also a light performance monitor 2416. There are also two sets of dispersion compensating units 2318, 2320, two per set. There is an optical switch 2422 and a fiber management system 2424. There are also two WDM multiplexers/ demultiplexers 2426, 2428. Thus, this embodiment of the remote PHY system is capable of supporting some of the elements of the hardware configuration of the two WDM transport systems that may be configured as the remote PHY system described in connection with fig. 21.

The optical channel monitor measures the number of wavelengths, the optical power level of each channel, and the OSNR of each channel. Automatic setup and configuration of optical channel line monitors for primary and secondary links is supported. The optical output power is optimized for the optimal Bit Error Rate (BER) for each receiver. The power may be set to +/-2dB for each receiver. This is critical for links with low OSNR. Dynamic system optimization may be performed in which an optical performance monitor provides real-time feedback to adjust the optical amplifier and also the variable optical attenuator settings for balancing the power in the various channels.

One feature of the method and apparatus of the present teachings is that manual entry of parameters is not required, which shortens setup time and minimizes errors. Nor does it require operations to measure parameters on the fiber link (such as distance, link loss, etc.) in advance. Link loss versus distance can vary widely depending on fiber quality, connection loss, and passive optical element changes. Previous systems required measurements for each link and were also notoriously compromised because errors in manually entered connections could not be discovered until a fiber cut or other disruption in service. This means that the service is disturbed. The optical performance monitor of the present teachings provides an early warning of OSNR or power degradation of each wavelength channel, which means that scheduled maintenance can be performed before the link drops. This improves the quality of service and reduces customer downtime. The optical performance monitor of the present teachings also helps to find the source of link problems, whether they are in the multiplexer/demultiplexer or in the remote PHY transceiver. The improved operational nature of the hardware-configured network of the present teachings reduces service rollouts (truck rolls) and reduces the time and cost of running the network.

One feature of the hardware configurable transceivers of the present teachings is that they simplify the deployment of systems that utilize wavelength tunable optical transceivers. For example, various Dense Wavelength Division Multiplexing (DWDM) transceivers used in remote PHY access networks are constructed by Multiple System Operators (MSOs). These systems may include products such as: finisar Corporation Flextune and for remote PHY access networks

Optical amplifiers, and 200G coherent optical transceivers that support commercial services.

Some embodiments of a WDM transport system utilizing hardware-configured transceivers of the present teachings enable up to ninety-six wavelength tunable optical transceivers in a remote PHY network to self-configure their wavelengths to operate on a DWDM infrastructure without input from host equipment, nor intervention from a technician. The technician plugs the hardware-configured transceiver into any host port in the head-end equipment and the remote PHY node, and connects the hardware-configured transceiver to any of the optical multiplexer ports using fiber optic patch cables. Firmware and a controller contained in the transceiver determine the appropriate wavelength to link the head-end equipment to each remote PHY node.

An operator need only be equipped with one general purpose hardware configuration of the wavelength tunable transceiver of the present teachings, as opposed to having many different fixed wavelength modules. The configuration time of a transceiver for a fixed wavelength module link may take hours. The configuration time of a link using a hardware configured transceiver may take several minutes or less. In addition, the technician does not have to trace the optical fiber from the optical multiplexer to the remote PHY node. These fibers may be 2km in distance or longer.

Some embodiments of hardware-configured transceivers of the present teachings utilize Finisar's 10Gb/s wavelength tunable duplex and dual-band bi-directional (BiDi) transceivers. In these embodiments, a dual-band BiDi SFP + transceiver adapts a pair of wavelengths into each port of a standard 100GHz DWDM multiplexer and demultiplexer. This allows up to eighty wavelengths to be deployed on existing forty wavelength DWDM networks. This results in an increase in data capacity from 200Gb/s to 400Gb/s in each direction on a single fiber without replacing the entire infrastructure. The BiDi transceiver also reduces the number of fiber patch cables by a factor of two because it has only one optical connection for a pair of wavelengths, which simplifies installation and saves space.

One feature of the present teachings is a method of supporting automatic discovery or configuration of a link that includes a hardware configured optical element. The auto-discovery function is also referred to in the art as establishing a link, establishing a connection, connecting a link, initiating a connection, and similar terms. The automatic discovery may be performed without any intervention from a human operator and/or without using an external network management system once the element is wired into the link. The various steps of a discovery method according to the present teachings may be referred to as a connectivity protocol, a connectivity algorithm, and/or a discovery protocol or algorithm. Embodiments of methods according to the present teachings generally relate to one or more of the steps for pre-configuring a module, powering up the module, and tuning the module operating wavelength. The method may be used, for example, to turn on and off Radio Frequency (RF) modulation (which may, for example, contain customer data traffic in the transceiver module), and also to perform other steps involved in establishing an optical link.

It should be understood that while various embodiments of methods according to the present teachings are directed to establishing a communication link between two hardware configured elements, various steps of the methods may be implemented in whole or in part to achieve other purposes, such as testing, network reconfiguration, and various other operations. The communication link may be unidirectional and/or bidirectional. The hardware modules involved in the discovery method of the hardware configured link may be, for example, optical transceiver modules. Some embodiments of the hardware module may include other elements in the link, such as amplifiers, wavelength selective switches, and many other devices. The method is effectively applied to both discovery of new links and addition of devices to existing links that include operational connections not established by embodiments of the method of the present teachings.

One feature of the method of the present teachings is that it enables deployment on existing systems because it uses a transparent connection of the light control plane that operates independently of the customer data traffic control plane. That is, there is no need to demodulate customer data to configure the elements. The optical control plane refers to the connections and protocols used by the hardware configured elements to achieve management purposes, such as link discovery. The light control plane in some embodiments operates only between optical transceivers and/or other hardware configured optical elements in the link, and does not necessarily need to be connected to a host management system, or to other elements in the optical system, to configure. The hardware configured elements need not be connected to or integrated into an existing physical layer control plane or data plane control system to become operational.

The light control plane of the present teachings is used to automatically discover links without interacting with any operating control system for existing traffic, e.g., after powering up the transceiver. This is because a hardware configured transceiver may be configured to sense other operational traffic during the discovery process without interrupting the traffic. As such, fiber optic cable installations that are transmitting real-time traffic may be upgraded, for example, from direct detection links operating at 100Gb/s rates or lower to coherent links operating at 400Gb/s rates or higher. One feature of the optical control plane of the present teachings is that there will be no service disruption during the upgrade because the operational traffic does not need to be acquired offline.

One feature of the methods and apparatus of the present teachings is the ability to automatically discover optical links using a coherent optical signaling format with a hardware configured SFP + transceiver. The control information is modulated at a rate lower than the data rate of the traffic. Another feature of the method and apparatus of the present teachings is that it can be used to automatically discover optical links without flexible or tunable optical multiplexers (such as WSSs) to combine signals onto a delivery fiber. The links may be unidirectional or bidirectional. Further, the link may use a transceiver configured for direct detection or coherent signaling formats, or a combination of these formats. The transceiver may also be either a tunable transceiver or a fixed transceiver.

Another feature of the method and apparatus of the present teachings is that it can be used to automatically configure optical links with various multiplexing and demultiplexing capabilities. Multiplexer and demultiplexer devices are commonly referred to as combiners and/or splitters. The terms splitter and combiner may be used interchangeably when referring to these devices. The splitters and combiners combine and split optical signals from one or more inputs to one or more outputs and are capable of operating in both directions as is well known to those skilled in the art.

As an example of various multiplexer/demultiplexer capabilities, it is taught that some embodiments of the coherent link use passive splitters/combiners without any wavelength filtering. Some link embodiments use fixed filter splitters, such as Arrayed Waveguide Grating (AWG) devices. Other embodiments use flexible, tunable filter splitters, such as Wavelength Selective Switches (WSSs). Embodiments using filtering splitters and combiners may use direct detection, coherent detection, or a combination of the two transceiver types. Some link embodiments use a bi-directional single fiber link. Other link embodiments use two unidirectional fibers to form a bidirectional link.

Some embodiments use a coherent architecture with a single laser within the transceiver, in which the receive operating wavelength is the same as the transmit operating wavelength because the transmit and receive operations share the same local oscillator (L O) laser device.

In some embodiments of systems according to the present teachings, the AWG and/or WDM demultiplexer are not present and the result is an optical link with both ends operating on the same ITU channel. Further, in some embodiments of systems according to the present teachings, the transmission is on a separate wavelength. In these embodiments, the receive path operates in a listening mode to determine the desired broadcast ITU channel. In these embodiments, there is no downlink, only an uplink. In other words, a unidirectional link is established.

In embodiments of the system according to the present teachings in which at least some of the transceivers use direct detection, the receivers are not operational. For direct detection systems, the transceiver does not use a coherent signal format. This means that these receivers do not require a local oscillator laser to function. Thus, one wavelength may be received by a WDM demultiplexer or WSS and transmitted on a different laser wavelength.

It is a feature of the present teachings that coherent transceivers may be used for some channels of a WDM system, with the channels being provided by the transceivers utilizing direct detection. That is, a coherent transceiver may be added to existing systems that use direct detection for some channels.

Some embodiments of the present teachings use fixed, wavelength filtered combiners/splitters. Fig. 25 shows a schematic diagram of an embodiment of a WDM transport link 2500 utilizing two unidirectional optical fibers 2502, 2504 to connect hardware configured tunable transceivers, transceiver 12506 and transceiver 22508, using fixed, non-tunable AWG filters 2510, 2512, 2514, 2516 in accordance with the present teachings. A transmitter of transceiver 12506 is connected to an input port of AWG 2510 to transmit optical signals to AWG 2512 over optical fiber 2502. The signal from the transmitter of transceiver 12506 passes to the output port of AWG 2512 connected to the receiver of transceiver 22508. The transmitter of transceiver 22508 is connected to the input port of AWG 2516 to transmit optical signals to AWG 2514 over optical fiber 2504. The signal from the transmitter of transceiver 22508 passes to the output port of AWG 2514 connected to the receiver of transceiver 12506.

The discovery method of automatically establishing a link according to the present teachings eliminates upper layer software and connects the link after the transceivers 2506, 2508 on both sides of the link 2500 are powered on. For purposes of the following description of the methods of the present teachings in association with fig. 25-27C, channel 52518 is selected for the transmit side of transceiver 12506 and channel 52520 is selected for the receive side of transceiver 12506. These are channels that pass a path connecting from a transmitter at one end of the link to a receiver at the other end of the link through the AWG. The two ends of the link may be referred to as the near end and the far end to distinguish the two ends without loss of generality. An embodiment of a method for automatically establishing a link between two ends is further described below in conjunction with fig. 26A-27C.

Referring to both fig. 25 and 26, transceivers 2506, 2508 have a loss of signal (L OS) indicator, where L OS 1 means no light is detected and L OS 0 means light is detected in the receiver, the link system typically starts from an idle state 2602, the idle state 2602 occurs, for example, when both transceivers 2506, 2508 are powered up, one rule of the state machine shown in state diagram 2600 is that if L OS is generating a "BEACON (BEACON)" signal, where the signal is turned on and off as described, for example, in connection with fig. 13-14 above, the transmitter transitions to a slow SCAN state 2604 (referred to as S L OW _ SCAN _ T) to tune its wavelength by scanning the channel at a slow rate, each channel change in the SCAN is shown in state diagram 2600 as a channel change 2606 and a slow SCAN state 2608, where each channel change in the SCAN is associated with a fast SCAN BEACON (BEACON) at a similar time as when the transceiver 2506, 2508 is sensing a fast SCAN power from a fast SCAN state, where the same TX pulse is being detected in connection with the transceiver 25013-on state, where the transceiver 2506, 2508 is sensing a fast SCAN pulse, a signal, which is being associated with a fast SCAN transceiver (BEACON) at a similar time as when the transceiver, which is being on transceiver 2506 is being described, which is being described in connection with the same as a fast SCAN state, which is being described, where the transceiver 2508.

From state S L OW SCAN 2604, when L OS-0 is received (where the duration of power is longer than the duration of two consecutive FAST SCAN pulses as shown in the received power map 2618), the transmitter transitions to FASTSCAN 2620, where the transmitter provides a FAST channel wavelength SCAN L OS-0 case represents the duration of light on the detector longer than a single FAST SCAN pulse, thus representing that light from the other end transmitter has caused it to reach the receiver.

From the TX BEACON state 2610, the transmitter transitions to a TX HO L D (TX hold) state 2614 when receiving L OS ═ 0 (where the pulse duration is longer than at least half the duration of the slow SCAN dwell time as shown in the receive power map 2612. in the TX HO L D state 2614, the transmitter continues to hold the current wavelength channel to which it is tuned from the TXHO L D state 2614, when receiving L OS ═ 1 as shown in the receive power map 2616, the transmitter transitions to a TX S L OWSCAN (TX slow SCAN) state 2604. from the TX BEACON, the transmitter transitions to an S L SCAN state 2604 when receiving L OS ═ 1 for a duration greater than the slow SCAN period, the receive status 2612 ═ 1 as shown in the receive power map 2616 initiates a transition from the HO L D (hold) state 2604 to the SCAN state 2604.

Fig. 26B shows a process flow diagram of an embodiment of a method 2650 for automatic channel discovery of the hardware-configured optical link of fig. 25. The flow chart is intended to represent steps in state transitions in an embodiment of a method 2650 of the present teachings. It should be understood that the numbering of the steps in the process flow diagram does not imply a particular order and/or particular timing of the execution of the steps of method 2650. In various embodiments, it is desirable to use all or a portion of the steps consistent with the present teachings. Fig. 26B depicts an SFP + type transceiver, but other embodiments may use other transceiver types. Fig. 26B is described herein using the transceiver configuration shown in fig. 25. However, as will be understood by those skilled in the art, various different transceiver configurations may follow the steps of method 2650 of fig. 26B to establish a link. It is also understood that multiple transceivers may operate in parallel and/or in series using the steps of method 2650 to establish multiple optical links between transceivers without human and/or administrative system intervention. Unidirectional and bidirectional links may also be established. Further, although the description includes reference to a predetermined threshold P_thAnd discussion of various durations and times, these are merely representative of particular embodiments. In various embodiments, various power thresholds may be used, and the same or different thresholds may be used for various decision steps. Various durations and pulse widths may also be used as described herein.

Step 12652 of the method is to power up a transceiver, such as transceivers 2506, 2508 of fig. 25. Continuing the description of the method by discussing only one transceiver, it is understood that any number of transceivers may perform the various steps of the method in the various embodiments of the method of establishing a link using the methods of the present teachings.

In step 22654, the transmitter laser in the transceiver begins transmitting power on channel N.In step 32656, the transmitter laser waits for a one second dwell on the channel and then changes to channel N +1 in step 42658. In decision step 52660, the receiver in the transceiver monitors the power and determines whether the received power is greater than a predetermined threshold P_th. In some embodiments, the threshold is an established signal loss received power value. For example, the signal loss received power level may be in the range of-35 dBm to 0dBm, depending on the application.

The receiver also determines whether the detected power has a duration equal to a certain predetermined value. The duration is selected to be the duration of the fast scan dwell time on a particular channel. In some embodiments, the particular value of the pulse duration is 10 ms. As described in connection with fig. 26B, the duration may also be referred to as a Pulse Width (PW). If the receiver does not sense power greater than the predetermined threshold and has a duration or pulse width equal to 10ms or other predetermined value, the method proceeds to another decision in a sixth step 2662. In step 62662, the receiver continues to monitor to determine if the duration of the received power, and the duration or pulse width PW, exceeds 10 ms. If so, the method moves to step 72664 and in step 72664 the transmitter initiates a fast scan wavelength scan sequence as described herein.

In decision step 82666, the receiver in the transceiver monitors the power and detects the optical power. The receiver determines whether the detected optical power is greater than a predetermined threshold P_thAnd whether the detected optical power has a timing pattern having a duration that is consistent with the beacon signal as described herein. If a beacon signal is detected, the method proceeds to step 92668 and the wavelength channel is incremented by one channel when the transmitter of the transceiver detects the beacon. In decision step 102670, the receiver in the transceiver continues to monitor the optical power and determines whether the detected optical power is greater than a predetermined threshold P_thAnd whether the detected optical power has a duration greater than a particular duration of the beacon signal ON state (in this example, 0.5 seconds). If so, the method continues to step 112672In decision step 122674, the receiver in the transceiver monitors the power and detects the optical power if the power is not less than the predetermined threshold P_thThe system proceeds to step 112672. that is, the system remains in the HO L D state_thThen the method moves back to step 22654 to begin another slow scan as described herein.

If in the decision associated with step 52660 the receiver in the transceiver monitors the power and determines that the received power is greater than the predetermined threshold P_thAnd the duration is greater than the dwell time on the particular channel being rapidly scanned (which is PW ═ 10ms for some embodiments), then the method proceeds to step 132676 and the transmitter in the transceiver moves to the BEACON state as described herein. In decision step 142678, the receiver monitors the detected optical power and determines whether the detected optical power is greater than a predetermined threshold P_thIf not, the method returns to step 132676. if yes, the method continues to step 152680 and the transmitter moves to the HO L D state as described herein. in decision step 162682, the receiver monitors the detected optical power and determines if the detected power is less than a predetermined threshold P_thIf not, the method returns to step 152680. that is, the transceiver remains at HO L D. if so, the method returns to step 22654 to begin another slow scan as described herein_thThat is, the power detected at the transceiver from the optical signal being present on the link that results in the L OS-0 condition at the transceiver connected to the link.

Fig. 27A shows a graph 2700 showing optical power as a function of time for an embodiment of a method of link connection associated with the hardware configured optical link of fig. 25 for a set of transmitter and receiver states and associated state timing diagrams, referring to fig. 25-27A, the graph 2700 shows a transmitted optical signal 2702 generated by the transmitter at the near end transceiver 12506 in the S L OW SCAN state 2604, a received optical signal 2704 received at the receiver at the far end transceiver 22508, a transmitted optical signal 2706 generated by the transmitter at the far end transceiver 22508, and a received optical signal 2708 received at the receiver at the near end transceiver 12506, further showing graphs of timing diagrams 2710 for the HO L D state 2614 of the transmitter at the near end transceiver 12506, timing diagrams 2712 for the BEACON state 2610 of the transmitter at the near end transceiver 12506, timing diagrams 2614 for the HO L D state of the transmitter at the near end transceiver 22508, timing diagrams 2714 in the high state, timing diagrams representing no state.

In the illustrative example presented in fig. 27A, transceiver 12506 is on and starts in TX _ S L OW _ TUNE state 2716, starting at channel 1, traversing wavelength tuning at a rate of, for example, one second per channel, when transceiver 12506 is tuned to channel 5, signal 2718 is detected at transceiver 22508. in some embodiments, the receiver specifically detects the duration of the signal longer than the time it takes to traverse the two channel tuning of the FAST scan duration, which is twice the duration of the FAST scan duration, which may be evidenced by the transceiver monitor generating L OS ═ 0 for the duration, in addition to the presence or absence of light on the detector, ensuring that the detection is a slow scan rather than a FAST scan, which will only last for one FAST scan pulse duration, which is optional, the signal detected at transceiver 638 causes the transmitter in transceiver 1254 to implement a FAST scan pulse duration, which is only for one FAST scan pulse duration, which is optional, when the transceiver 1257 is switched on, which causes the transceiver 12506 to transmit a signal on at TX _ n transition 12527, which causes the transceiver 1257 to be on, which causes the transceiver to transmit a signal to be on at a transition 12527, which is shown in TX _ n 12527, which causes the transceiver 12506 to be detected at the transceiver 12527, and which causes the transceiver to be on state 12519 to be detected at the transceiver 12519 when the transceiver 12519, the transceiver 1256, which causes the transceiver to be on state 2719, which causes the transceiver to be on transceiver to be detected at the transceiver to be on state 2719, which is the transceiver to detect the transceiver to be on, which is the transceiver 12519, which is shown in the transceiver 12519, which causes the transceiver to be on state 2719, which causes the transceiver to be on transition, which causes the transceiver to be on a transition, which causes the transceiver to be on state 2719 when the transceiver to be on a transition, which causes the transceiver to be on, which causes the transceiver to be detected when the transceiver 12519, which is shown in the transceiver 12519, which causes the transceiver to be on a transition, which causes the transceiver to detect the transceiver to be on state 2719, which is the transceiver to be on state 2727, which causes the transceiver 125.

Figure 27B shows an experimental setup 2750 measuring optical power as a function of time for an embodiment of a method of link connection associated with a hardware configured optical link of the present teachings. The two transceivers 2752, 2754 are connected in a unidirectional manner through AWG 2756, 2758, 2760, 2762 via two fiber links 2764, 2766.

Fig. 27C shows an oscilloscope trace 2780 showing optical power as a function of time for an embodiment of a method of connection protocol associated with the optical link of the hardware configuration of fig. 27B. Referring to both fig. 27B-C, there is a trace 2782 associated with the first transceiver 2752 and a trace 2784 associated with the second transceiver 2754. First transceiver 2752 is shown running slow scan 2786 and beacon 2788. Second transceiver 2754 is shown running fast scan 2790. For a forty wavelength channel system, a slow scan would require 40 seconds to scan all channels. However, as will be appreciated by those skilled in the art, various other scan times are possible in various embodiments of the slow wavelength scan of the present teachings.

One feature of the present teachings is that the connection protocol method can be applied to transceivers that use a coherent signaling format. A coherent transceiver includes a tunable transmitter and a tunable receiver. The wavelength is based on the laser channel set point. One of the photodiodes in the receiver allows the total power to be monitored, which is equivalent to a non-coherent SFP + tunable transceiver. This allows for easy connection without the need for labeling or fiber numbering.

Fig. 28A shows a schematic diagram of an embodiment of a WDM transport link 2800 in accordance with the present teachings, the WDM transport link 2800 utilizing two unidirectional optical fibers 2802, 2804 to connect tunable coherent transceivers, a transceiver 12806, and a transceiver 22808, in a hardware configuration using filter-based combiners/ splitters 2810, 2812, 2814, 2816. In some embodiments, the combiners/ splitters 2810, 2812, 2814, 2816 are AWG filters. In some embodiments, the combiner/ splitters 2810, 2812, 2814, 2816 are WSS devices. A transmitter of the transceiver 12806 is connected to an input port of the combiner/splitter 2810 to transmit an optical signal to the combiner 2812 through the optical fiber 2802. The signal from the transmitter of transceiver 12806 passes to the output port of combiner/splitter 2812 which is connected to the receiver of transceiver 22808. The transmitter of transceiver 22808 is connected to the input port of combiner/splitter 2816 to transmit optical signals to combiner/splitter 2814 via optical fiber 2804. The signal from the transmitter of transceiver 22808 is passed to an output port of combiner/splitter 2814 which is connected to a receiver of transceiver 12806. The connection protocol method for link 2800 may be the same as that described in connection with link 2500 of fig. 25, and also described in connection with fig. 26-27C.

Fig. 28B shows a state diagram 2820 of an embodiment of the method of automatic channel discovery of the hardware configured optical link of fig. 28A. generally speaking, for coherent systems using a filtered combiner-splitter (such as an AWG), an embodiment of the method utilizes a state similar to that of the SFP + case described in connection with fig. 25-27C.

The optical link may be in an idle state 2822 this idle state 2822 may for example exist at system start-up and/or transceiver power-up the system has an allowed transition from the idle state 2822 to a slow SCAN state 2824 the slow SCAN state 2824 is also referred to as S L OW SCAN _ T, where the transmitter tunes its wavelength by scanning the channel at a slow rate speed the transition may for example be triggered automatically some time after start-up each channel change in the SCAN associated with the slow SCAN state 2824 is shown as a channel change transition 2826 in the state diagram 2820 the slow SCAN and FAST SCAN wavelength tuning parameters are the same or similar to those described above in connection with fig. 13-14 from the slow SCAN state 2824 when the receiver in the transceiver detects L OS 0 (where as shown in the receive power diagram 2828 the power value is positive and the duration is longer than the duration of two consecutive FAST SCAN pulses) when the receiver in the transceiver detects L OS, the TX OFF state is set as a TX OFF signal, the associated transceiver is therefore the TX OFF signal is set to a TX OFF signal for a certain time to be received by the transceiver before the transceiver is set as a TX OFF signal, thus the transceiver is not required to be sent from the local transceiver when the transceiver is found to be OFF.

The transition out of the slow SCAN state 2824 is also triggered by the receiver detecting L OS FAST SCAN L O T, that is, L OS 0 or power is detected for a brief duration of the FAST SCAN pulse time under which condition the transceiver state transitions to the HO L D state 2836. for more than two FAST SCAN pulse durations, the HO L D state 2836 remains at L OS 1 or no power is detected and transitions to the slow SCAN state 2824.

From the TX OFF, L O _ FAST _ SCAN state 2830 on the sense channel to receive direct detection, the transmitter is set to the sense channel and enters the State 2834 to generate TX short pulses, which effectively generates an "ACK" for the far side to indicate that light is detected, the channel is determined, and the transceiver is ready for the HO L D state for another transceiver the TX short pulse state 2834 then transitions to the HO L D state 2836.

Fig. 28C shows a process flow diagram of an embodiment of a method 2850 of automatic channel discovery of an optical link of the hardware configuration of fig. 28A. For an optical link setup, the transceivers on both sides will be powered up. The first step 2852 is to power up the transceiver. At step 22854, the transceiver begins slow tuning of the wavelength, starting with wavelength channel N. In step 32856, the laser remains on the wavelength channel from step 22854 for 1 second. As described herein, in some embodiments, other predetermined long scan channel durations are used instead of the 1 second duration. Then, in step 42858, the channel becomes N + 1. In step 52860, it is determined whether the received power in the transmitter has exceeded a threshold P_th. If not, the method moves back to step 22854 and the slowly tuned channel is incremented. If the received power in the transmitter has exceeded the threshold value P_thIn step 72864, the transceiver performs fast tuning of the receiver L O to find the value of the wavelength channel being transmitted in step 82866, the transmitter in the transceiver is set to the channel found by the L O receiver fast tuning, and in step 92868, a short pulse is transmitted as an "ACK" to acknowledge receipt of the signal and initiate HO L D in the other transceiver decision step 102870 determines if the received power exceeds a threshold, and if so, in step 11, the transmitter HO L D state 2872 decision step 122874 effectively maintains the state until power is lost_thThe method continues to step 22854 otherwise it continues to the HO L D state of step 112872 in decision step 102870, if the received power is not greater than the predetermined threshold, the method moves to step 22854 for slow tuning of the wavelength.

One feature of the present teachings is that embodiments using coherent transceivers do not require the transmission of a fast scan signal over the link. A fast scan optical signal is generated in the transceiver and then mixed with a signal incoming to the transceiver. When the incoming signal has the same wavelength channel as the fast-scan wavelength channel, a short pulse of light with a dwell time nominally equal to the dwell time of the particular channel in the fast scan is detected at the output of a mixer in the transceiver. This detection of an optical pulse having a duration equal to or less than the dwell time on the rapidly scanned particular wavelength channel provides information to proceed with link establishment as described herein.

Fig. 28D represents a graph 2880 showing optical power as a function of time for a set of transmitter and receiver states that exist during an embodiment of the method of automatic channel discovery for a hardware-configured optical link of fig. 28A, sender trace 2882 in transceiver 12806 represents the transceiver power-on and slow SCAN start, receiver in transceiver 22808 directly detects trace 2884 represents the power detected from transceiver 12806 by direct detection, where it is not mixed with a local oscillator in transceiver 22808, which represents channel 5 through combiners/ splitters 2810, 2812, 2814, 2816, trace 2866 output by the sender in transceiver 22808 and trace 2888 of the receive L O laser in transceiver 22808 show the start of slow SCAN interrupted by a state transition to TX OFF, L O _ SCAN state 30 in fig. 28B, trace 2890 of the signal detected in transceiver 22808, channel 5, the incoming trace 2890 of the signal is represented by a short pulse TX signal generated by the transceiver 2896, the receive signal generated by the transceiver 2896, when the receive signal is received by fastscan on fastscan 2896, as indicated by short pulse signal rx 2896, receiver 2896.

The link configurations of the present teachings are used in a variety of different use cases, including, for example, data centers, cable television distribution, and/or telecommunications applications.A large number of deployments currently exist in data centers such as 1.6 terabit switches built with separate 100-Gb/s transceivers.with 100-Gb/s coherent signaling, in some configurations, there is a 30dB dynamic range.for 400-Gb/s in some configurations, there is a 22dB dynamic range.in configurations with longer links, EDFA is used.

Fig. 29 shows a schematic diagram of a WDM transport link 2900, the WDM transport link 2900 utilizing two unidirectional optical fibers 2902, 2904 to connect a hardware configured tunable coherent transceiver, transceiver 12906, and transceiver 22908, with non-filter based combiners/ splitters 2910, 2912, 2914, 2916 of the present teachings. The transmitter of transceiver 12906 is connected to the input port of combiner/splitter 2910 to transmit the optical signal to combiner 2912 through optical fiber 2902. The signal from the transmitter of transceiver 12906 passes to the output port of combiner/splitter 2912 which is connected to the receiver of transceiver 22908. The transmitter of transceiver 22908 is connected to an input port of combiner/splitter 2916 to transmit the optical signal to combiner/splitter 2914 through optical fiber 2904. The signal from the transmitter of transceiver 22908 is passed to the output port of combiner/splitter 2914 which is connected to the receiver of transceiver 12906. Optional optical amplifiers 2918, 2920 may be added to the link to account for losses from the passive combiners/ splitters 2910, 2912, 2914, 2916. An amplifier may be placed anywhere between transceiver 12906 and transceiver 22908 to account for losses in the link as understood by those skilled in the art.

The high dynamic range of the coherent technology in the transceivers 2906, 2908 makes it possible to implement passive combiner and splitter architectures using combiner/ splitters 2910, 2912, 2914, 2916 without filters. The embodiment of link 2900 of fig. 29 eliminates AWG and WSS costs and allows simple connections without the need for labels or fiber numbering.

Basically, the establishment of the link is still based on the detection of optical signals including a slow scan, the determination that the duration of the detected signal is at least as long as the dwell time on the slow scan specific wavelength channel, and the detection of optical signals having a duration less than or equal to the duration of the dwell time on the fast scan specific wavelength channel.

In operation, the far-side receiver uses RF detection and total power detection to determine when the near-side transmitter is not modulated and tuned to the CW channel that it can receive because it is the same as L O in the far-side receiver.

An embodiment of a startup connection protocol method for a coherent link with a passive unfiltered combiner as shown in fig. 29 will now be described in more detail. For embodiments using a master/slave approach, the master transceiver is, for example, transceiver 2906 and the slave transceiver is transceiver 2908, but the designation is arbitrary. The RF amplifier is turned off in the transceiver on the near side of the link, generating a CW carrier on power up.

FIG. 30A shows a spectrum 3000 produced by a transceiver in an active state according to a method using a connection protocol according to the present teachings, this represents the spectrum of a signal produced by CW L O at a particular wavelength channel, the transceiver to laser output power is only transmitted when VOA or SOA is on, FIG. 30B shows a spectrum 3020 produced by a transceiver in an established link operating state according to a method of a connection protocol according to the present teachings, this represents the spectrum of a signal produced by a transmitter on a particular channel with RF modulation on, FIG. 30C shows a spectrum time series 3040 of a method of a connection protocol of the present teachings in a tuned state without RF modulation, in these figures, different line types indicate different wavelength channels, FIG. 30C shows a received light detection signal according to a slow scan including L O, a transceiver scans the occupied channels on its connected fiber, a spectrum time series 3040 shows the spectrum for four sequential wavelength channels, then the spectrum time series 3040 is shown after the spectrum time series 3040 is shown as being a slow scan signal, which may be "T" in a predetermined time interval "and the spectrum time series is shown as a series of a data spectrum time series 60, which is used in a WDM data channel scan method of a WDM system with a frequency spectrum time series representing the present teachings, a method of a system which is generally representing the number of a system channel scan without the initial bandwidth of a series of a system which is a frequency spectrum time series of a frequency spectrum of a system which is not modulated by a signal carried by a WDM channel.

Continuing with the description of initiating the connection protocol, the near side receiver uses the RF detection from L O and a photodiode located in the coherent receiver behind the polarization splitter to look for a modulated channel if no modulated channel exists, the receiver waits on channel 1, the slave transceiver powers up, and starts tuning from channel 1, this causes the master receiver to detect the far side L O on channel 1, thus initiating a beacon state for the master transmitter.

In the case of a link being established on channel 1, as described further below, the protocol will proceed to another transceiver master/slave pair that will not affect traffic on channel 1. the scanning of the link will result in a spectral time series 3060 as shown in FIG. 30D, where the modulated signal is on channel 1 and tuned by the master L O on the other channels.

In some embodiments, the transceiver modules are configured in master or slave mode and have, for example, different product numbers to distinguish them via internal database parameters prior to shipment. The master and slave transceiver modules operate in pairs to form a link. However, in some embodiments, master or slave designation is not necessary, and transceivers at the near or far end of the link can execute the protocol as described herein without master or slave designation. The module of the master configuration may support vendor defined "auto-tune configuration" register usage for initiating the connection protocol. The primary side transceiver module is connected to or includes a host processor that knows the appropriate transmit channel configuration for that module. The slave configured modules will start in auto-tune mode at power cycle and/or power-on reset. Thus, for some embodiments, auto-tuning is a step in a method that implements a connection protocol, and initiates slow tuning of a transmitter through a sequence of channels that stay on each channel for a particular duration before changing to the next channel in the sequence of channels. The duration may be of various durations. For example, in some embodiments, the duration is 1 second. In other embodiments, the duration is 5 seconds. In some embodiments, a channel sequence is a sequence that starts from a particular channel number on the ITU grid and steps one channel number at a time. For example, the sequence may start from channel 1 of the ITU grid, or the sequence may start from another channel of the ITU grid.

If receive L OS is asserted, in other words, the receiver indicates L OS ═ 1, the host processor writes to an "auto-tune configuration" register that begins the slow scan tuning mode.

For the slave, the transmitter finds asserted at power-up, a five second per channel slow channel tuning process begins, with the tuned channel set to the last set channel, if RX _ L OS is cleared, tuning is suspended, otherwise, if RX _ L OS is asserted, the method continues tuning to the next channel.

In these embodiments, the first channel tuned will cause the link to be established, the master will immediately exit the tuning mode and enter normal operation, in which case, from power up, a transmit discovery mode is asserted, TX DIS, and slow tuning channel processing begins, with tuning starting from the last channel set.

In an embodiment of the existing link route slave setup, the master side module proceeds as follows.in the master module, TX _ DIS is asserted at power up.the host processor sets the appropriate TX channel.if RX _ L OS (L OS ═ 0) is shut down, the processor skips setting the "auto tune configuration" register.

In some embodiments, a new slave-side module is installed and the process is as follows for the master, slow tuning is complete and the link is established the master module is in normal operation if the host processor detects that RX _ L OS (L OS 0) is asserted for "x" time, the host writes an "auto-tune configuration" register to start the auto-tuning mode.

The process is as follows when a new slave side module is installed TX _ DIS is asserted at power up, the slow channel tuning process starts with five seconds per channel, starting with the last set channel or the first channel, if RX _ L OS (L OS 0) is deasserted, then automatic tuning stops, otherwise, if RX _ L OS (L OS 0) is asserted, then the method tunes to the next channel, the current TX channel is stored after RX _ L OS (L OS 0) is deasserted.

Some embodiments of the present teachings utilize an unfiltered splitter to connect a transceiver to a device that combines optical signals onto a link fiber to provide a bi-directional connection with a reduced component count. The means for combining the optical signals onto the link fibers may or may not be filtered. The use of passive splitters connected to the transceiver transmitter and receiver reduces the number of combiner elements by half for a bi-directional link. In some embodiments, the fiber optic link includes an optical amplifier. In other embodiments, no amplifier is used.

In some of these embodiments, both sides ping-pong the routine until the L O fast scan for search overlaps the TX CW turn-on.

Fig. 31 shows a schematic diagram of a WDM transport link 3100 of the present teachings, the WDM transport link 3100 utilizing coherent hardware configured transceivers 3102, 3104 with AWG filters. The output of coherent transmitter 3106 is connected to a port of 1X2 splitter 3108. The input of coherent receiver 3110 is connected to the second port of 1X2 splitter 3108. The third port of the 1X2 splitter 3108 is connected to the AWG filter 3112. The AWG filter 3112 combines the light from each input port into an optical fiber 3114 connected to the AWG filter 3116. The optical fiber 3114 carries bidirectional optical traffic. The output port of the AWG filter 3116 is connected to one port of the 1X2 splitter 3118. The coherent receiver 3120 is connected to another port of the 1X2 splitter 3118. The coherent transmitter 3122 is connected to a third port of the 1X2 splitter 3118. In some embodiments, the transceivers 3102, 3104 may be positioned far away from the AWGs 3112, 3116, e.g., as far as several kilometers away. This may be referred to as a remote PHY configuration. The AWG 3112, 3116 does not tune or change the filtering. The AWGs 3112, 3116 filter the wavelength channels.

In the WDM transport link 3100, transceivers 3102, 3104 are required on both sides of the link to operate on the same wavelength channel, since the wavelengths must pass through the filters of the AWG 3112, 3116. It also requires that the transceivers 3102, 3104 operate at overlapping times to establish a connection. Using master/slave technology, one of the transceivers 3102, 3104 is tuned fast and the other of the transceivers 3102, 3104 is tuned slow. This provides overlap and detection on both sides of the link 3100. Taking into account the filters of AWG 31123116 in link 3100, handshaking is used in this process to close the coherent link.

Fig. 32 shows a schematic diagram of a WDM transmission link 3200 according to the present teachings, the WDM transmission link 3200 utilizing coherent hardware configured transceivers 3202, 3204 with passive splitters without filtering. Link 3200 uses passive splitters 3206, 3208 to combine the optical signals from transceivers 3202, 3204. Link 3200 operates bi-directionally over optical fiber 3210. The output of coherent transmitter 3212 is connected to a port of passive splitter 3206. The input of coherent receiver 3216 is connected to a second port of passive splitter 3206. Passive splitters 3206, 3208 are free of wavelength filtering. Splitter 3206 combines and/or splits the light from each port into optical fibers 3210 that are connected to splitter 3208. The coherent receiver 3220 is connected to a first port of the splitter 3208. The coherent transmitter 3222 is connected to a second port of the splitter 3208. In some embodiments, for remote PHY configurations, transceivers 3202, 3204 are positioned remotely, e.g., up to several kilometers away, from respective splitters 3206, 3208.

In the discovery process of the embodiment of link 3200 described in connection with FIG. 32, the transmitters 3212, 3222 power up, traverse the established link search and check the established link, in the event that the transmitter on one side powers up, the far side transmitter is off, it is found to be necessary to work as well.

The connection algorithm operates with multiple transmitters (not shown) connected to link 3200 operating simultaneously. The passive splitter coherent architecture of link 3200 is relatively simple to connect. There is no need to label any TX or RX fibers and there is no need to align to any particular passive port. This allows links to be established and the PHY layer for the data center to be built without any higher layer software connectivity protocols. In some embodiments of an unfiltered link using coherent SFP + transceivers, a separate and distinct control, separate from SFP +, must be used to support the passive splitter architecture and reduce the wiring and ADD/DROP costs. These embodiments will be specific to low channel count coherent traffic use cases.

In addition, semiconductor optical amplifiers and/or variable optical attenuators (SOA/VOA) are deactivated at the transmit side to eliminate any contention when the far side receiver scans existing channels.

In some embodiments, a specific connection routine for receiver scanning, transmitter setup, and a wait state in which a far-side connection is established is used. This includes a specific framework that enables fast and slow technologies to be used for tunable lasers to establish connections without complex protocols. The process of avoiding contention is similar to older low-level ethernet copper connection management and collision avoidance techniques. However, in embodiments of methods according to the present teachings, these techniques are applied to coherent optical links propagating multiple wavelengths.

The steps of a method for establishing a hardware configured link including an unfiltered splitter and a coherent transceiver according to the present teachings generally include the steps of searching for occupied channels and CW-L O signals by tuning L O in the coherent receiver, the method further includes the steps of modulating on an optical signal with a coherent transmitter, and scanning CW-L O channels with a particular time sequence.

30A-B, the spectrum 3000 of the transmitter with the RF amplifier turned off is shown as being distinct from the spectrum 3020 of the transmitter with the RF amplifier turned on in order to generate spectrum 3000, the RF amplifier is turned off, which results in a single CW carrier signal spectrum, SOA is turned on, and is in an "up" (up) state, in order to generate spectrum 3020, the RF amplifier is turned on, providing data modulation on the CW carrier, and allowing data to flow through the link.

Figure 33A shows a spectral time series 3300 of a transceiver in a tuned state without RF modulation according to an embodiment of a method of a connection protocol of the present teachings, a far-end transceiver tunes L O at the receiver to mix with an incoming signal to search for an occupied channel, figure 33B shows a spectral time series 3320 of an embodiment of a method of using a connection protocol according to the present teachings, the spectral time series 3320 showing how a transceiver without RF modulation tunes with latency between the series to avoid collisions, each starting wavelength 3322 repeats in a given transmitter with a particular period 3324 to eliminate collisions between other transmitters hooked to the near side of the link, figure 33C shows the spectrum 3340 of a transceiver with RF modulation after a connection is successfully completed in a method of a connection protocol according to the present teachings, a near-end transmitter is turned on, a link is established, and customer data traffic is being transmitted over the link.

One feature of the present teachings is that L O fast scan and slow scan tuning timing sequences used for search tuning can be configured to achieve various objectives one objective is, for example, to enable a single laser in a transceiver package to perform both a L O fast scan for searching using a transceiver receiver and a L O slow tune to be sent to another transceiver to determine wiring connections and wavelength channels for the connections other objectives include utilizing the extensibility of channel counts the timing sequence should be such that even if the channel count is small, it can quickly converge to a particular link connection and wavelength channel and can also search over a relatively large number of channels.

FIG. 34A shows spectral- time series 3400, 3420 associated with the state of the search and connect steps of an embodiment of a method of a connection protocol according to the present teachings. different line types represent different spectral components for different wavelength channels.A L O search step using a resulting fast scan 3402 in the case of a spectral-time series 3400 is used to determine occupied channels as described herein. the spectral-time series 3400 is produced by a local oscillator laser in the receiver and is not transmitted along the link.A fast scan as described earlier includes a scan of wavelength channels in the system where the dwell time duration of each channel is relatively short and the total channel scan time is the time that steps through each channel.

A spectral time sequence 3400 of L O search steps is shown in which the far-side transceiver generates a fast scan 3402 using a fast scan of a receiver L O that includes a short duration scan that traverses each of a predetermined number of channels.

The modulation bandwidth of the detected mixed signal is used to identify the optical signal at the input of the receiver. A large modulation bandwidth indicates occupied channels. In contrast, the continuous wave local oscillator signal has no perceptible modulation bandwidth. Thus, a relatively small or negligible modulation bandwidth is indicative of the continuous wave local oscillator signal.

The unmodulated signals used to identify the link channels are distinguished in the receiver from the occupied channels because they have no modulation bandwidth, therefore, the RF detection at the far-side receiver indicates which channels have been occupied by coherent modulation because they exhibit RF modulation bandwidth, if occupied channels are identified, any occupied channels are discarded from the subsequent long duration TX _ ON state scan, however, all channels are typically scanned in a L O search step, which makes it possible to determine whether a channel or fiber is disconnected.

In the TX _ ON state, the transmitter is ON, with CW unmodulated L O signals for unoccupied channels, initiating L O slow scan spectral time series 3420 the scan interval T43426 and wavelength channel dwell duration T33424 of the scan of CW L O signals traversing the channels are set to avoid collisions with other transmitters and ensure a receive L O search overlap with the receive side of the link fast scan in the embodiment of the method shown in fig. 34A the near side transmitter scans for CW L O signals through the first wavelength channel 3422 for a duration T33424, in some embodiments time T33424 is about 3 times T13402, the near side transmitter waits a period T43426 before changing to the next wavelength channel 3428, T43426 may be a random time, in some embodiments time T43426 is about 2 n +/-rand T1, where rand is random time up to n T1, the number of different channels transmitted to the far side transceiver is increased to enable a short duration of the link search time T1 to be increased, and the number of links to remain closed.

FIG. 34B shows a spectral time series 3430 relating to the state of the transceiver and the associated L O laser, according to an embodiment of a method of using a connection protocol of the present teachings, the transceiver uses a single laser for both L O searches and for far-end communications over a fiber link, L O searches occur in some embodiments when L OS is asserted in the transceiver. Trace 3432 represents a slow scan where L O sends a L O signal over the link, with one transmission cycle of one wavelength channel being shown, Trace 3434 represents a transceiver L O search fast scan. the local receiver uses the fast series to scan possible channels to determine if a signal is present on any channel incoming to the receiver. Trace 3436 shows a composite view of the use of a particular L O laser for the combination of receiver search and far-end communications, L O search fast scan occupies a duration T1, followed by the interval T before the slow scan channel is sent, the slow scan duration T3, then a wait interval T4.

In some embodiments, T1 is the duration that the short pulse for each channel can be scanned in a L O search fast scan.time T3 equals 3 times T1. time T equals 2 times the number of channels times T1, T2 is T1 plus the number of channels times a random number times T1, where the random number is between 0 and 0.99. time T4 is the sum of T minus T2 plus T3. for example, if the channel count is 4: T1 100ms, T800 ms, T3 300ms, 100ms < T2<396ms, 104ms < T4<400 ms. as another example, for a channel count of 3: T1 100ms, T600 ms, T3 300ms, 100ms < T2<297ms, 3ms < T4<400 ms.

The representation of the timing sequence of fig. 34B in trace 3436 shows how it can perform a receive L O search fast scan and transmit slow channel scan with a single laser in the transceiver.

Fig. 35 represents a set of time series 3500 for an embodiment of a method of using a connection protocol in accordance with the present teachings that displays an unfiltered optical link that searches for and detects, the time series 3500 optionally includes a direct detection time series and includes a spectral series, the same use of different line types for different wavelength channels is utilized in fig. 35 as in fig. 34A-b.a representation of a TX _ ON _1 state spectral time series trace 3502 is shown, where for a near side transceiver (also referred to as transceiver 1), a slow scan sequence is initiated in an ON state, a spectral series associated with a search for L O in transceiver 1 is represented in trace 3504. note that, as described in connection with fig. 34A-B, in some embodiments, a single laser L O may generate a tuning sequence represented in traces 3502, 3504. for a far side transceiver (also referred to as transceiver 2) a TX _ ON _2 state spectral time series trace 6 is shown in an ON state for a direct detection time series trace 358. a receiver in a direct detection time series trace for power detection in receiver 2 is represented in a direct detection time series L.

Both transmitters initiate a search sequence when they power up, which is shown at the beginning of time sequence traces 3504 and 3510. Note that the designations "near side" and "far side" are merely for descriptive clarity to distinguish the two sides of the link. The system works bi-directionally without any special designation of the near side and/or far side of the link.

In operation, when transceiver 2 begins to transmit optical signals 3514 to slowly traverse the channel scan and transmit them to the link using the spectral time series of its traces 3506, direct detection in the near-side receiver detects light 3516 as shown in trace 3508, but does not distinguish particular channels, likewise, when the near-side transceiver begins to transmit optical signals 3518 in a slow scan traversing the channels in its spectral time series 3502, direct detection in the far-side receiver spectral time series 3512 detects light 3520, but does not distinguish particular channels, however, the next tuned channel 3524 in the slow scan from transceiver 2 is picked UP by the receiver in transceiver 1, this is shown at region 3522, region 3522 shows the overlap of the slowly scanned channel 3524, and the match with the fast scan channel L O in trace 3504. thus, when the scan of the slow scan O in transceiver 1 overlaps with the matching channel O L from the slow scan of transceiver 2, this channel is found "on" and the particular channel is then dropped "for the RF channel and the RF amplifier is then turned on" and the RF amplifier is then turned on for that particular channel L.

The framing sequence associated with intervals T1, T, T3, and T4 described in connection with the scout scan of unmodulated channels described in connection with fig. 34A prevents collisions or repetition of channel overlaps fig. 36A shows a spectral timing diagram 3600 of an embodiment of a link establishment method for a coherent link with an unfiltered passive splitter/combiner according to the present teachings, L O scout trace 3602 shows that timing is characterized by a search interval T1, and an interval T between searches, L O fast scan scout sequence has a period T5-T1 + T-slow scan trace 3604 shows that timing is timed by the duration 3T 1 of the dwell time on the slow scan channel, and at random timesInterval T before inter-tuning to the next channel_rand(selected to avoid conflict with L O search fast scan.) characterization, e.g., T_randFIG. 36B shows a combined spectral timing diagram 3650 of an embodiment of the link establishment method of the coherent link with unfiltered passive splitter/combiner of FIG. 36A, how timing is such that a single laser can switch between receiving the slow scan signals being searched and sent at a local oscillator used for fast scanning of L O searching for incoming channels because there is no overlap of channel transmissions, that is, because T is fixed relative to T1, L O is turned on for one side of the channel within 3T 1 during the slow scan channel dwell time, and this is at T_randAnd so the probability of overlapping to close the link increases.

An important feature of the system and method for configuring optical network elements for optical links and other hardware configurations is the use of both slow wavelength scanning and fast wavelength scanning to exchange information between the elements. The relative timing of these scans allows the elements to identify each other and also to determine various other aspects of the link configuration so that links may be established, client data traffic sent over the links, for example, and other element configuration information may also be communicated. As such, the present teachings describe wavelength scanning that includes slow scanning and fast scanning that are used together to support various embodiments of a protocol for link setup. Wavelength scanning is the scanning of wavelength channels in a particular system, characterized by a particular dwell time on each channel and a full channel scan time, which is the time it takes to traverse all channel scans of the system given the particular dwell time of each channel. One important feature to ensure convergence of the protocol is the relative timing of the slow scan and the fast scan. In general, a slow scan is a scan in which the duration of the dwell time on a particular wavelength channel is as long as or longer than the duration of a complete scan of the wavelength channel in the fast scan.

The slow scan and fast scan timing parameters are selected such that elements in the link can be configured based on detection of the slow scan and fast scan signals and determination of the duration of the detected light. For example, in a link with two transceivers, the detection of light pulses of duration equal to the dwell time on a particular wavelength channel for fast scanning, and the detection of signals from the link of duration equal to the dwell time on a particular wavelength channel for slow scanning, allows the transceivers on both sides of the link to automatically configure the link and transmit client data traffic. Various embodiments of the system determine the detection of a light pulse having a duration equal to the dwell time on a particular wavelength channel for fast scanning and the detection signal from the link having a duration equal to the dwell time on a particular wavelength channel for slow scanning in various manners as described herein.

Equivalents of

While applicants 'teachings are described in conjunction with various embodiments, applicants' teachings should not be limited to such embodiments. On the contrary, the applicants' teachings encompass various alternatives, modifications, and equivalents as may be made thereto without departing from the spirit and scope of the present teachings, as will be appreciated by those skilled in the art.

Claims (41)

1. A method for establishing a communication link for a coherent transceiver, the method comprising:

a) receiving an optical signal having a channel wavelength from a link;

b) mixing an optical signal having a channel wavelength with a fast-scanned optical signal comprising a local oscillator channel wavelength to produce a mixed optical signal;

c) detecting the mixed optical signal when a particular one of the channel wavelength and the local oscillator channel wavelength is at the coincident channel wavelength, thereby generating an electrical detection signal;

d) determining a modulation bandwidth of the electrical detection signal; and

e) if the determined modulation bandwidth of the generated electrical mixing signal is greater than the predetermined bandwidth, the coincident channel wavelength is identified as the occupied channel wavelength.

2. The method for establishing a communication link for a coherent transceiver of claim 1, further comprising:

a) generating a slow-scan optical signal comprising a continuous wave local oscillator channel and transmitting the slow-scan optical signal comprising the continuous wave local oscillator channel over the link;

b) receiving a portion of a transmitted slow-scan optical signal comprising a continuous wave local oscillator channel;

c) mixing the received portion of the transmitted slow-scan optical signal including the continuous wave local oscillator wavelength channels with a second fast scan of the local oscillator wavelength channels to produce a second mixed optical signal;

d) detecting a second mixed optical signal when a particular one of the continuous wave local oscillator wavelength channels of the received portion of the transmitted optical signal and a particular one of the second fast-scan local oscillator wavelength channels are in a coincident second wavelength channel, thereby generating a second electrical detection signal;

e) tuning a wavelength channel of a local oscillator in an optical transmitter to a consistent second wavelength channel; and

f) if the modulation bandwidth of the second electrical detection signal is less than the predetermined bandwidth, then RF modulation is turned on to establish the communication link.

3. The method for establishing a communication link for a coherent transceiver of claim 1, wherein the fast scan of the local oscillator channel wavelength has a predetermined time sequence.

4. The method for establishing a communication link for a coherent transceiver of claim 2, wherein the fast scan of the local oscillator channel wavelength has a predetermined time sequence.

5. The method for establishing a communication link for a coherent transceiver of claim 2, wherein the second fast scan of local oscillator channel wavelengths has a predetermined time sequence.

6. The method for establishing a communication link for a coherent transceiver of claim 2, wherein the slow scan of the continuous wave of the local oscillator channel wavelength has a predetermined time sequence.

7. The method for establishing a communication link for a coherent transceiver of claim 6, wherein the predetermined time sequence of slow scans comprises random times between continuous wave local oscillator channel wavelengths.

8. The method for establishing a communication link for a coherent transceiver of claim 2, wherein the fast scan and the second fast scan of the local oscillator channel wavelengths have a predetermined time sequence and the slow scan has a second predetermined time sequence, wherein the predetermined time sequence of the fast scan and the second fast scan of the local oscillator channel wavelengths is faster than the predetermined time sequence of the slow scan of the continuous wave local oscillator channel wavelengths.

9. The method for establishing a communication link for a coherent transceiver of claim 8, wherein at least one of the predetermined time sequence of the fast scan and the second fast scan and the predetermined time sequence of the slow scan are selected to avoid collisions.

10. The method for establishing a communication link for a coherent transceiver of claim 8, wherein the predetermined time sequence of the fast scan and the second fast scan is relatively faster than the predetermined time sequence of the slow scan.

11. The method for establishing a communication link for a coherent transceiver of claim 1, wherein the occupied channel wavelengths are removed from a subsequent slow scan.

12. The method for establishing a communication link for a coherent transceiver of claim 2, wherein a fast scan is performed at a near-side coherent transceiver and a slow scan is performed at a far-side coherent transceiver.

13. The method for establishing a communication link for a coherent transceiver of claim 2, wherein a fast scan is performed at a far-side coherent transceiver and a slow scan is performed at a near-side coherent transceiver.

14. A method for configuring a hardware configured optical link between a near side transceiver and a far side transceiver, the method comprising:

a) generating a first optical signal comprising a slow scan of wavelength channels with a near-end transceiver and transmitting the generated first optical signal to a far-end transceiver;

b) receiving, at a far-end transceiver, a portion of a first optical signal generated with a near-end transceiver;

c) determining whether the received portion of the first optical signal includes a duration that is greater than a duration of a dwell time on a particular wavelength channel of the fast scan;

d) generating, with the far-end transceiver, a second optical signal comprising a fast scan of wavelength channels if the received portion of the first optical signal is determined to comprise a duration of dwell time on the fast scan particular wavelength channel, and transmitting the generated second optical signal to the near-end transceiver;

e) receiving, at the near-end transceiver, a portion of a second optical signal generated with the far-end transceiver and determining whether the received portion of the second optical signal comprises a duration that is less than twice a duration of a dwell time on a particular wavelength channel of the fast scan; and

f) if the received portion of the second optical signal is determined to comprise a duration less than twice the duration of the dwell time on the fast-scan particular wavelength channel, a third optical signal comprising a beacon signal is generated at the current operating wavelength of the near-end transceiver using the near-end transceiver and transmitted to the far-end transceiver.

15. The method for configuring a hardware-configured link of claim 14, wherein the slow scan of wavelength channels is at a rate approximately equal to one channel per second.

16. A method for configuring a hardware configured link as recited in claim 14, wherein the rate of the fast scan of wavelength channels is approximately equal to one channel per millisecond.

17. The method for configuring a hardware configured link of claim 14, wherein transmitting the generated first optical signal to a far-end transceiver connected to a near-end transceiver comprises: the generated first optical signal is transmitted through a wavelength filter.

18. The method for configuring a hardware-configured link of claim 14, wherein determining whether the received portion of the first optical signal comprises a duration of dwell time on a rapidly scanning particular wavelength channel comprises determining a duration of time for which a loss of signal (L OS) indicator is equal to zero.

19. The method for configuring a link of a hardware configuration of claim 14, further comprising:

a) receiving a portion of the third optical signal at the remote transceiver and determining whether the received portion of the third optical signal comprises a beacon signal;

b) generating a fourth optical signal comprising a slow scan of the wavelength channel with the far-end transceiver and transmitting the generated fourth optical signal to the near-end transceiver if the received portion of the fourth optical signal is determined to comprise a beacon signal;

c) receiving, at the near-end transceiver, a portion of a fourth optical signal generated with the far-end transceiver and determining whether the received portion of the fourth optical signal comprises a duration that is greater than half a duration of a dwell time on a particular wavelength channel of the slow scan;

d) generating a fifth optical signal comprising a hold signal at the near-end transceiver and transmitting the generated fifth optical signal to the far-end transceiver if the received portion of the fourth optical signal is determined to comprise a duration that is greater than half the duration of the dwell time on the slow-scan particular wavelength channel;

e) receiving a portion of the fifth optical signal at the remote transceiver and determining whether the received portion of the fifth optical signal comprises a duration greater than the fast scan duration; and

f) if the received portion of the fifth optical signal is determined to include a duration that is greater than the duration of the dwell time on the fast-scanned particular wavelength channel, the operating wavelength of the remote transceiver is set to the second current operating wavelength and real-time traffic is then transmitted from the remote transceiver using the second current operating wavelength.

20. A method for configuring a hardware configured optical link between a near-end coherent transceiver and a far-end coherent transceiver, the method comprising:

a) generating a first optical signal comprising a slow scan of a CW wavelength channel with a near-end coherent transceiver;

b) transmitting the generated first optical signal to a far-end coherent transceiver;

c) receiving, at a far-end coherent transceiver, a portion of a first optical signal generated with a near-end coherent transceiver;

d) determining whether the received portion of the first optical signal comprises a current CW wavelength channel;

e) generating a second optical signal comprising the current CW wavelength channel with a remote coherent transceiver; and

f) if the received portion of the first optical signal is determined to include the current CW wavelength channel, the resulting second optical signal is transmitted to a near-end coherent transceiver.

21. The method for configuring a link of a hardware configuration of claim 20, further comprising: determining, at the near-end coherent transceiver, whether the received signal includes RF modulation on a first wavelength channel, and if the received signal is determined to include RF modulation on the first wavelength channel, generating a slowly scanned first optical signal including CW wavelength channels starting from a second wavelength channel.

22. The method for configuring a hardware configured link of claim 21, wherein the first wavelength channel comprises channel 1 of an ITU grid and the second wavelength channel comprises channel 2 of the ITU grid.

23. The method for configuring a hardware configured link of claim 20, wherein transmitting the generated first optical signal to a far-end coherent transceiver comprises: the resulting first optical signal is transmitted through a passive optical splitter.

24. The method for configuring a hardware-configured link as recited in claim 20, wherein determining whether the received portion of the first optical signal includes the current CW wavelength channel comprises: the received portion of the first optical signal is mixed with a local oscillator and a DC detected power is generated.

25. The method for configuring a link of a hardware configuration of claim 20, further comprising:

a) receiving a portion of the second optical signal at the near-end coherent transceiver and determining whether the received portion of the second optical signal includes the current CW wavelength channel;

b) generating a third optical signal including a beacon signal on the current CW wavelength channel with the near-end coherent transceiver and transmitting the generated third optical signal to the far-end coherent transceiver if the received portion of the second optical signal is determined to include the current CW wavelength channel;

c) receiving, at the far-end coherent transceiver, a portion of the third optical signal generated with the far-end coherent transceiver and determining whether the received portion of the third optical signal comprises a beacon signal at the current CW wavelength channel; and

d) if the received portion of the third optical signal is determined to include a beacon signal at the current CW wavelength channel, a fourth optical signal including an RF modulated signal at the current CW wavelength channel is generated at the far-end coherent transceiver and transmitted to the near-end coherent transceiver.

26. A hardware configured optical link between a near-end transceiver and a far-end transceiver, comprising:

a) a far-end transceiver comprising a coherent optical transmitter and a coherent optical receiver;

b) a near-end transceiver, the near-end transceiver comprising:

i) a tunable coherent optical transmitter configured to generate a first optical signal comprising a first scan of continuous wave wavelength channels at a transmitting port;

ii) a coherent optical receiver that receives at a receiving port a portion of the second optical signal generated by the far-end transceiver; and

iii) a processor that instructs the tunable coherent optical transmitter to transmit the RF modulation using the current operating wavelength if the processor determines that the received portion of the second optical signal comprises an unmodulated RF optical signal;

c) a first optical combiner comprising a first port connected to the transmit port and a second port connected to the far-end transceiver; and

d) a second optical combiner including a first port connected to the receive port and a second port connected to the far-end transceiver.

27. The hardware configured optical link of claim 26, wherein at least one of the first optical combiner and the second optical combiner comprises a filter.

28. The hardware configured optical link of claim 26, wherein at least one of the first optical combiner and the second optical combiner comprises a wavelength selective switch.

29. The hardware configured optical link of claim 26, wherein at least one of the first optical combiner and the second optical combiner comprises a passive splitter.

30. The hardware configured optical link of claim 26, wherein at least one of the first optical combiner and the second optical combiner comprises an AWG.

31. A hardware configured optical link between a near-end transceiver and a far-end transceiver, comprising:

a) a far-end transceiver comprising a coherent optical transmitter and a coherent optical receiver;

b) a near-end transceiver, the near-end transceiver comprising:

i) a tunable coherent optical transmitter configured to generate a first optical signal comprising a first scan of continuous wave wavelength channels at a transmitting port;

ii) a coherent optical receiver configured to receive at a receiving port a portion of a second optical signal generated by the far-end transceiver; and

iii) a processor having an input connected to the output of the coherent optical receiver and an output connected to the input of the coherent optical transmitter, the processor configured to: instructing the tunable coherent optical transmitter to transmit the RF modulation using the current operating wavelength if the processor determines that the received portion of the second optical signal comprises an unmodulated RF optical signal;

c) an optical splitter including a first port connected to the transmission port and a second port connected to the reception port; and

d) an optical combiner including an input connected to the third port of the optical splitter and an output connected to the far-end transceiver.

32. The hardware configured optical link of claim 31, wherein the optical combiner comprises a filter.

33. The hardware configured optical link of claim 31, wherein the optical combiner comprises a wavelength selective switch.

34. The hardware configured optical link of claim 31, wherein the optical combiner comprises a passive splitter.

35. The hardware configured optical link of claim 31, wherein the optical combiner comprises an AWG.

36. A method for configuring a hardware configured optical link, the method comprising:

a) generating a first optical signal comprising a slow scan of wavelength channels, the slow scan having a dwell time on a particular wavelength channel;

b) generating a second optical signal comprising a fast scan of wavelength channels, the fast scan having a dwell time on a particular wavelength channel and a full channel scan time, wherein the slow scan dwell time is greater than or equal to the full channel scan time;

c) transmitting a first optical signal comprising a slow scan of wavelength channels over a link;

d) detecting a portion of a first optical signal transmitted over a link;

e) detecting light pulses having a duration equal to or less than the dwell time on the rapidly scanned particular wavelength channel; and

f) in response to detecting an optical pulse of duration equal to the dwell time on the particular wavelength channel of the fast scan and detecting the portion of the first optical signal transmitted over the link, a client data traffic is transmitted over the link.

37. The method of claim 36, wherein detecting the portion of the first optical signal transmitted over the link comprises: and (4) directly detecting.

38. The method of claim 36, wherein detecting the portion of the first optical signal transmitted over the link comprises: and (4) coherent detection.

39. The method of claim 36, wherein detecting a light pulse having a duration equal to a dwell time on a rapidly scanned particular wavelength channel comprises: the generated second optical signal is mixed with a signal from the link.

40. The method of claim 36, wherein detecting a light pulse having a duration equal to a dwell time on a rapidly scanned particular wavelength channel comprises: detection was performed using direct detection.

41. The method of claim 36, wherein detecting a light pulse having a duration equal to a dwell time on a rapidly scanned particular wavelength channel comprises: detection is performed using coherent detection.

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