JP2019041364A - Network management by node-by-node cross phase modulation (xpm) compensation - Google Patents

Abstract

To provide a network management by node-by-node cross phase modulation (XPM) compensation.SOLUTION: A method and device for selective and node-to-node XPM compensation may divide the wavelength into a short distance propagation wavelength (STW) and a long distance propagation wavelength (LTW) on the basis of transmission distance over the respective optical paths of the wavelength. In the other functions of an ROADM node, the XPM compensation on the ROADM node may be selectively executed on the LTW, while the STW may pass therethrough without carrying out the XPM compensation.SELECTED DRAWING: Figure 11

Description

[Reference to related applications]
This application is a continuation-in-part of US patent application Ser. No. 15 / 373,289, Dec. 8, 2016, the entire contents of which are incorporated herein by reference.

[Technical field]
The present disclosure relates generally to optical communication networks, and more particularly to network management with per-node cross phase modulation (XPM) compensation.

  Telecommunications, cable television systems, and data communication systems use optical networks to quickly transfer large amounts of information between remote locations. In an optical network, information can be conveyed in the form of optical signals through optical fibers. An optical fiber can have a thin string of glass capable of transmitting signals over long distances. Optical networks often use modulation schemes to convey information with optical signals over optical fibers. Such modulation schemes may include PSK (phase-shift keying), FSK (frequency-shift keying), ASK (amplitude-shift keying), and QAM (quadrature amplitude modulation).

  As the data rate of the optical network continues to increase and reaches 1 terabit / s (1T) or higher, the OSNR (optical signal, for example, due to the use of advanced modulation formats such as QAM and PSK with dual polarization The demand for -to-noise ratio also increases. Furthermore, a phase shift of the optical signal transmitted over the optical network may be observed. The phase shift may be self-phase modulation (SPM) in which light interacts with the optical fiber during transmission. Furthermore, an XPM can occur in which one light wavelength can change the phase of another light wavelength.

  In one aspect, the disclosed reconfigurable optical add-drop multiplexer (ROADM) is wavelength division multiplexed (ROSS) that is provided as an input to a first wavelength selective switch (WSS). There may be a first WSS that switches between adjacent channel groups contained in a wavelength division multiplexed (WDM) optical signal. In ROADM, an adjacent channel group may represent an optical band transmitted by a WDM optical signal. The ROADM may further include a first cross-phase modulation (XPM) compensator that receives a first group of adjacent channel groups from the first WSS. In ROADM, the first XPM compensator may further include a forward feedback XPM adjustment loop that generates an XPM control signal. The forward feedback XPM adjustment loop includes a dispersion compensation module (DCM) to add dispersion corresponding to a portion of the effective length of the optical fiber span that carries the WDM optical signal following the ROADM. The first XPM compensator further includes: a phase modulator that receives the first group, receives the XPM control signal, and receives the XPM compensated first group; and a second WSS that receives the XPM compensated first group. May have.

  In any of the disclosed embodiments, the ROADM receives a plurality of additional adjacent channel groups from the first WSS in addition to the first XPM compensator and outputs an XPM compensated group to the second WSS, respectively. May further comprise a vessel.

  In any of the ROADM disclosure embodiments, the second WSS may receive the XPM compensated group and switch the channel corresponding to the WDM optical signal for transmission.

  In any of the disclosed embodiments of the ROADM, the first XPM compensator may exclusively compensate the first subgroup of XPM, the first group being the first subgroup and the first WSS. And at least one additional adjacent channel switched to a 1 XPM compensator. In ROADM, the second WSS may drop at least one adjacent channel received by the first XPM compensator.

  In any of the ROADM disclosed embodiments, the first XPM compensator receives a WDM optical signal, a second input to the forward feedback XPM adjustment loop, and a WDM optical signal in the forward feedback XPM adjustment loop. And an optical bandpass filter applied to the second input that passes the adjacent channel group selected from the above.

  In any of the ROADM disclosure embodiments, the first XPM compensator may be able to compensate for the X and Y polarization components of XPM with polarization diversity, the first XPM compensator being And a first phase modulator for compensating the first phase corresponding to the X polarization component, and a second phase modulator for compensating the second phase corresponding to the Y polarization component.

  In another aspect, the disclosed optical system may have a first WSS that switches between adjacent channel groups included in a WDM optical signal supplied as an input to the first WSS. In an optical system, an adjacent channel group may represent an optical band transmitted by a WDM optical signal. The optical system may further include a first XPM compensator that receives a first group of adjacent channel groups from the first WSS. In an optical system, the first XPM compensator may further include a forward feedback XPM adjustment loop that generates an XPM control signal. The forward feedback XPM regulation loop includes DCM to add dispersion corresponding to a portion of the effective length of the optical fiber span that carries the WDM optical signal following the optical system. The first XPM compensator further includes: a phase modulator that receives the first group, receives the XPM control signal, and receives the XPM compensated first group; and a second WSS that receives the XPM compensated first group. May have.

  In any of the disclosed embodiments, the optical system receives, in addition to the first XPM compensator, each additional adjacent channel group from the first WSS and outputs an XPM compensated group to the second WSS. A compensator may be further included.

  In any of the disclosed embodiments of the optical system, the second WSS may receive the XPM compensated group and switch the channel corresponding to the WDM optical signal for transmission.

  In any of the disclosed embodiments of the optical system, the first XPM compensator may exclusively compensate for the first subgroup of XPM, the first group by the first subgroup and the first WSS. And at least one additional adjacent channel switched to the first XPM compensator. In an optical system, the second WSS may drop at least one adjacent channel received by the first XPM compensator.

  In any of the disclosed embodiments of the optical system, the first XPM compensator receives a WDM optical signal, a second input to the forward feedback XPM adjustment loop, and WDM light in the forward feedback XPM adjustment loop. An optical bandpass filter applied to the second input that passes the adjacent channel group selected from the signal may be further included.

  In any of the disclosed embodiments of the optical system, the first XPM compensator may be capable of compensating for the X polarization component and the Y polarization component of the XPM having polarization diversity. Further includes a first phase modulator that compensates for the first phase corresponding to the X polarization component, and a second phase modulator that compensates for the second phase corresponding to the Y polarization component.

  In a further aspect, the disclosed method for XPM compensation of an optical signal may include switching between adjacent channel groups included in a WDM optical signal provided as an input to the first WSS. In the method, the adjacent channel group may represent an optical band transmitted by a WDM optical signal. The method may further comprise receiving a first group of adjacent channel groups from the first WSS at the first XPM compensator. In the method, the first XPM compensator may be able to generate an XPM control signal using a forward feedback XPM adjustment loop. The forward feedback XPM adjustment loop includes a DCM that adds dispersion corresponding to a portion of the effective length of the fiber optic span that carries the WDM optical signal following the second WSS. In the method, the first XPM compensator can further transmit the first group and the XPM control signal to the phase modulator that outputs the XPM compensated first group, and receive the XPM compensated first group at the second WSS. Good.

  In any of the disclosed embodiments, the method receives each additional adjacent channel group from the first WSS, and transmits each additional group to the corresponding plurality of XPM compensators in addition to the first XPM compensator. And outputting an XPM compensated group from the XPM compensator to the second WSS. In the method, the second WSS may receive the XPM compensated group and may select a channel corresponding to the WDM optical signal for transmission.

  In any of the disclosed embodiments of the method, the first XPM compensator may exclusively compensate the first subgroup of XPM, the first group being the first subgroup and the first WSS. And at least one additional adjacent channel switched to a 1 XPM compensator.

  In any of the disclosed embodiments of the method, the second WSS may drop at least one adjacent channel received by the first XPM compensator.

  In any of the disclosed embodiments, the method includes receiving the WDM optical signal at a second input to a forward feedback XPM adjustment loop; and the second input in the forward feedback XPM adjustment loop. And passing an adjacent channel group selected from the WDM optical signal by an optical bandpass filter applied to the WDM optical signal.

  In any of the disclosed embodiments, the method comprises compensating for the X and Y polarization components of XPM having polarization diversity, wherein the X phase component is compensated using a first phase modulator. Compensating a first phase corresponding to the polarization component, and compensating a second phase corresponding to the Y polarization component using a second phase modulator. good.

  In a further aspect, a reconfigurable optical add-drop multiplexer (ROADM) for selective per-node XPM compensation is disclosed. The ROADM may include a first optical splitter that can receive an optical signal having a short range propagation wavelength (STW) in the first group and a long range propagation wavelength (LTW) in the second group. In ROADM, the first group and the second group may be spectrally separated from each other in the optical signal. The ROADM may also include a wavelength selective switch (WSS) that can receive an optical signal from the first optical splitter. In ROADM, the WSS can pass the STW to the first group in the output optical signal. The ROADM may also include a second optical splitter that can receive an optical signal from the first optical splitter, and a first cross phase modulation (XPM) compensation unit that can receive STW and LTW from the second optical splitter. In ROADM, the LTW may be XPM compensated by the first XPM compensation unit and output as XPM compensation LTW, while the STW may be terminated by the first XPM compensation unit.

  In any of the disclosed embodiments, the ROADM may further include a first drop port in the second optical splitter that can drop at least one of the STWs without XPM compensation, The STW dropped at the drop port can be terminated.

  In any of the disclosed embodiments, the ROADM may further include a third optical splitter that can receive the XPM compensated LTW from the first XPM and transmit the XPM compensated LTW to the WSS. In ROADM, the WSS can switch the XPM compensation LTW to the second group in the output optical signal. The ROADM may further include a second drop port in the third optical splitter that can drop at least one of the XPM compensated LTW, and the WSS can terminate the XPM compensated LTW dropped at the second drop port. .

  In any of the disclosed embodiments, the ROADM may further include a first add port at the WSS that can add at least one new STW to the first group in the output optical signal.

  In any of the disclosed embodiments, the ROADM may further comprise a second cross phase modulation (XPM) compensation unit with a second add port and an output to the WSS. In ROADM, the second XPM compensation unit can add at least one new LTW to the second group in the output optical signal and XPM compensate the new LTW.

  In any of the disclosed embodiments, the ROADM may further include a wavelength conversion unit capable of shifting at least one wavelength of the new LTW and the new STW.

  In a further aspect, an optical system for selective per-node XPM compensation is disclosed. The optical system may include an optical network that includes a plurality of nodes. At least some of the nodes have ROADM nodes that include a first XPM compensation unit. The optical system may further include a network control unit including a processor and a storage medium accessible to the processor. The storage medium stores instructions executable by a processor that receives path information of an optical path provisioned over an optical network. The path information designates a common start point node and a first ROADM node included in the optical path. Each one ROADM node includes a first XPM compensation unit. The instructions may be further executable to configure at least one transmitter at the common source node to assign wavelengths that are transmitted over the optical path and received at each of the first ROADM nodes. The wavelengths assigned by the transmitter have a short range propagation wavelength (STW) in the first group and a long range propagation wavelength (LTW) in the second group. In an optical system, the first group and the second group may be spectrally separated from each other in the optical signal. The instructions may be further executable to configure the first ROADM node to perform XPM compensation of LTWs in the second group using the first XPM compensation unit.

  In any of the disclosed embodiments of the optical system, the instructions configure the first ROADM node to pass at least one of the STWs in the first group to the output optical signal without XPM compensation. Instructions may be included.

  In any of the disclosed embodiments of the optical system, a second ROADM node selected from at least some of the first ROADM nodes has a first add port that receives at least one new LTW added to the optical signal. The instruction may further comprise a second XPM compensation unit having an instruction for configuring a second ROADM node to XPM compensate a new LTW received at the first add port using the second XPM compensation unit. May have.

  In any of the disclosed embodiments of the optical system, at least some of the second ROADM nodes may have a second add port that can receive at least one new STW that is added to the optical signal, and the instructions are An instruction for configuring the second ROADM node may be further included to add a new STW from the second add port to the first group in the output optical signal without a new STW XPM compensation.

  In any of the disclosed embodiments of the optical system, at least some of the first ROADMs have a wavelength conversion unit that can shift the wavelength of at least one of the new LTW and the new STW.

  In any of the disclosed embodiments of the optical system, at least some of the first ROADM nodes have a first drop port that can drop at least one of the STWs without XPM compensation.

  In any of the disclosed embodiments of the optical system, at least some of the first ROADM nodes have a second drop port that can drop at least one of the XPM compensated LTWs.

  In a further aspect, a method for selective per-node XPM compensation of an optical signal is disclosed. The method includes receiving path information of provisioned optical paths across the optical network. The path information specifies a common start node and a first reconfigurable optical add / drop multiplexer (ROADM) node included in the optical path. Each of the first ROADM nodes includes a first XPM compensation unit. The method may further comprise configuring at least one transmitter at the common source node to assign wavelengths that are transmitted over the optical path and received at each of the first ROADM nodes. The wavelengths assigned by the transmitter have a short range propagation wavelength (STW) in the first group and a long range propagation wavelength (LTW) in the second group. In the method, the first group and the second group may be spectrally separated from each other in the optical signal. The method may further comprise configuring the first ROADM node to perform XPM compensation of LTWs in the second group using the first XPM compensation unit.

  In any of the disclosed embodiments, the method may further comprise configuring a first ROADM node to pass the STW in the first group without XPM compensation to the output optical signal.

  In any of the method disclosure embodiments, a second ROADM node selected from at least some of the first ROADM nodes has a first add port that receives at least one new LTW that is added to the optical signal. Further comprising a second XPM compensation unit, the method may further comprise configuring a second ROADM node to XPM compensate the new LTW received at the first add port using the second XPM compensation unit.

  In any of the disclosed embodiments of the method, at least some of the second ROADM nodes have a second add port capable of receiving at least one new STW that is added to the optical signal, A step of configuring a second ROADM node to add a new STW from the second add port to the first group in the output optical signal without XPM compensation of the STW may be further included.

  In any of the disclosed embodiments, the method shifts the wavelength of at least one of the new LTW and the new STW using a wavelength conversion unit included in at least some of the first ROADM nodes; May further be included.

  In any of the disclosed embodiments, the method drops at least one of the STWs without XPM compensation from the optical signal using a first drop port included in at least some of the first ROADM nodes. A step.

  In any of the disclosed embodiments, the method further comprises dropping at least one of the XPM compensated LTW using a second drop port included in at least some of the first ROADM nodes. Good.

For a more complete understanding of the present disclosure and its features and advantages, reference is made to the following description, taken in conjunction with the accompanying drawings, in which:
FIG. 3 is a block diagram of selected elements of one embodiment of an optical network. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator. FIG. 6 is a block diagram of selected elements of one embodiment of an example XPM compensation. FIG. 6 is a block diagram of selected elements of one embodiment of an example XPM compensation. FIG. 6 is a block diagram of selected elements of one embodiment of an example XPM compensation. FIG. 6 is a block diagram of selected elements of one embodiment of an example XPM compensation. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator with polarization diversity. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator with polarization diversity. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator with polarization diversity. FIG. 6 is a block diagram of selected elements of an exemplary embodiment of an XPM compensator with polarization diversity. Figure 5 is a flowchart of selected elements of a method for XPM compensation. Figure 5 is a flowchart of selected elements of a method for XPM compensation. It is a spectrum of spectrally grouped wavelengths. FIG. 4 is a block diagram of selected elements of one embodiment of a ROADM with selective XPM compensation. FIG. 4 is a block diagram of selected elements of one embodiment of a ROADM with selective XPM compensation. FIG. 6 is a network diagram of selected elements of one embodiment of a ring interconnect with selective XPM compensation. FIG. 6 is a network diagram of selected elements of one embodiment of a ring interconnect with selective XPM compensation. FIG. 6 is a network diagram of selected elements of one embodiment of a ring interconnect with selective XPM compensation. FIG. 6 is a flowchart of selected elements of a method for selective XPM compensation. FIG. 6 is a block diagram of selected elements of one embodiment of a network controller.

  In the following description, details are set forth as an example to facilitate discussion of the disclosed subject matter. However, it will be apparent to one skilled in the art that the disclosed embodiments are illustrative and are not exhaustive of all possible embodiments.

  Throughout this disclosure, reference signs in the form of hyphens represent specific instances of one element, and reference signs in the form without a hyphen represent elements in general or collectively. Thus, by way of example (not shown), device 12-1 represents an instance of a device class and may be collectively referred to as device 12, any of which are generally referred to as device 12. good. In the figures and the description, like symbols represent like elements.

  Referring to the figures, FIG. 1 illustrates an exemplary embodiment of an optical network 101 that may represent an optical communication system. The optical network 101 may include one or more optical fibers 106 for carrying one or more optical signals communicated by components of the optical network 101. The network elements of the optical network 101 are coupled together by a fiber 106, one or more transmitters 102, one or more multiplexers (MUX) 104, one or more optical amplifiers 108, one or more optical add / drop multiplexers. An optical add / drop multiplexer (OADM) 110 and one or more demultiplexers (DEMUX) 105 and one or more receivers 112 may be included.

  The optical network 101 may comprise a point-to-point optical network with terminal nodes, a ring optical network, a mesh optical network, or any other suitable optical network or combination of optical networks. The optical network 101 may be used in a short distance urban area network, a long distance intercity network, or any other suitable network or combination of networks. The capacity of the optical network 101 may include, for example, 100 Gbit / s, 400 Gbit / s, or 1 Tbit / s. The optical fiber 106 may have a thin glass string capable of transmitting a signal over a long distance with very low loss. The optical fiber 106 may comprise any suitable type of fiber selected from a variety of different fibers for optical transmission. The optical fiber 106 includes any suitable type of fiber such as SMF (Single-Mode Fiber), E-LEAF (Enhanced Large Effective Area Fiber), or TW-RS (TrueWave® Reduced Slope) fiber. You can do it.

  The optical network 101 may include a device that transmits an optical signal via the optical fiber 106. Information may be transmitted and received over the optical network 101 by modulation of one or more wavelengths of light to encode information about the wavelength. In an optical network, the wavelength of light may also be referred to as a channel included in an optical signal (also referred to herein as a “wavelength channel”). Each channel may carry a specific amount of information through the optical network 101.

  To increase the information capacity and transmission capability of the optical network 101, multiple signals transmitted on multiple channels may be combined into a single broadband optical signal. The process of communicating information over multiple channels is optically referred to as WDM (wavelength division multiplexing). Coarse wavelength division multiplexing (CWDM) represents the multiplexing of widely spaced wavelengths with a small number of channels into a single fiber, typically greater than 20 nm and less than 16 wavelengths. DWDM (dense wavelength division multiplexing) represents multiplexing of densely spaced wavelengths having a large number of channels, more than 40 at intervals narrower than 0.8 nm, into a single fiber. WDM or other multiple wavelength multiplex transmission techniques are used in optical networks to increase the aggregate bandwidth per optical fiber. Without WDM, the bandwidth in an optical network can be limited to a bit rate of only one wavelength. With greater bandwidth, the optical network can transmit more information. Optical network 101 may transmit different channels using WDM or some other suitable multi-channel multiplexing technique to amplify multi-channel signals.

  The optical network 101 may include one or more optical transmitters (Tx) 102 that transmit optical signals through the optical network 101 at specific wavelengths or channels. The transmitter 102 may include a system, device, or apparatus that converts an electrical signal into an optical signal and transmits the optical signal. For example, each transmitter 102 transmits a laser and a beam that receives an electrical signal, modulates the information contained in the electrical signal into a beam of light generated by the laser at a specific wavelength, and transmits the signal through an optical network. Modulator.

  Multiplexer 104 may be coupled to transmitter 102 and may be a system, apparatus, or device that couples signals transmitted by transmitter 102 at respective individual wavelengths, for example, to WDM signals.

  The optical amplifier 108 may amplify the multi-channel signal in the optical network 101. The optical amplifier 108 may be placed before or after the specific length of fiber 106. The optical amplifier 108 may include a system, device, or apparatus that amplifies an optical signal. For example, the optical amplifier 108 may include an optical repeater that amplifies the optical signal. This amplification may be performed by opto-electric or electro-optical conversion. In some embodiments, the optical amplifier 108 may include an optical fiber doped with a rare earth element to form a doped optical fiber amplifying element. As the signal passes through the fiber, external energy is applied in the form of a pump, exciting atoms in the doped portion of the optical fiber and increasing the intensity of the optical signal. As an example, the optical amplifier 108 may include an erbium-doped fiber amplifier (EDFA).

  OADM 110 may be coupled to optical network 101 via fiber 106. The OADM 110 may include an add / drop module that may include a system, apparatus, or device that adds or drops an optical signal from the fiber 106 (eg, at individual wavelengths). After passing through the OADM 110, the optical signal may travel directly to the destination along the fiber 106, or the signal may pass through one or more additional OADMs 110 and / or the optical amplifier 108 before reaching the destination. good.

  In a particular embodiment of the optical network 101, the OADM 110 may represent a reconfigurable OADM (ROADM) that can add or drop individual or multiple wavelengths of a WDM signal. Individual or multiple wavelengths may be added or dropped in the optical domain using, for example, a wavelength selective switch (WSS) (not shown) that may be included in the ROADM.

  As shown in FIG. 1, the optical network 101 may include one or more demultiplexers 105 at one or more destinations of the network 101. The demultiplexer 105 may comprise a system, apparatus or device that operates as a demultiplexer by separating a single combined WDM signal into individual channels at each wavelength. For example, the optical network 101 may transmit a 40 channel DWDM signal. The demultiplexer 105 may split the signal, 40 channel DWDM signal, into 40 separate signals according to 40 different channels.

  In FIG. 1, the optical network 101 may also include a receiver 112 coupled to the demultiplexer 105. Each receiver 112 may receive optical signals transmitted at a particular wavelength or channel and process the optical signals to obtain (eg, demodulate) information (ie, data) that they contain. Accordingly, the network 101 may have at least one receiver 112 for each channel of the network.

  An optical network, such as the optical network 101 of FIG. 1, may use modulation techniques to convey information in an optical signal via an optical fiber. Such modulation schemes include PSK (phase-shift keying), FSK (frequency-shift keying), ASK (amplitude-shift keying), and QAM (quadrature amplitude modulation), among other examples of modulation techniques. You can do it. In PSK, the information conveyed by the optical signal may be converted by modulating the phase of the reference signal, also known as the carrier or simply the carrier. Information uses two-level or BPSK (binary phase-shift keying), four-level or QPSK (quadrature phase-shift keying), M-PSK (multi-level phase-shift keying) and DPSK (differential phase-shift keying) And may be conveyed by modulating the phase of the signal itself. In QAM, information carried by an optical signal may be transmitted by modulating both the amplitude and phase of the carrier wave. PSK is considered part of QAM. Here, the amplitude of the carrier wave is kept constant.

  Furthermore, polarization division multiplexing (PDM) technology can achieve a higher bit rate for information transmission. PDM transmission involves independently modulating information into different polarization components of the optical signal associated with the channel. In this way, each polarization component can carry a signal separate from the other polarization components. Thereby, the bit rate can be increased according to the number of individual polarization components. The polarization of an optical signal can usually represent the direction of vibration of the optical signal. The term “polarization” can refer to a path that is tracked by the tip of the electric field vector of an optical signal at a point in space, usually perpendicular to the propagation direction of the optical signal.

  In an optical network such as the optical network 101 of FIG. 1, it is common to refer to a management plane, a control plane, and a transport plane (often referred to as a physical layer). A central management host (not shown) may be present in the management plane and may configure and manage components of the control plane. The management plane has ultimate control over all transport plane and control plane entities (eg, network elements). As an example, the management plane may include a central processing center (eg, a central management host) that includes one or more processing resources, data storage components, and the like. The management plane may be in electrical communication with elements of the control plane and may be in electrical communication with one or more network elements of the transport plane. The management plane may perform system-wide management functions and provide coordination between network elements, control planes and transport planes. As an example, the management plane is an EMS (element management system) that handles one or more network elements from an element perspective, an NMS (network management system) that handles many devices from a network perspective, and an OSS that handles network-wide operations. (Operational support system).

  Changes, additions or omissions may be made to the optical network 101 without departing from the scope of the present disclosure. For example, the optical network 101 may have more or fewer elements than those shown in FIG. Also, as described above, although illustrated as a point-to-point network, the optical network 101 has any suitable network topology for transmitting optical signals, such as ring, mesh, and / or hierarchical network topologies. You can do it.

  As described above, XPM can occur where one optical wavelength can change the phase of another optical wavelength, such as between channels of a WDM optical signal. Phase modulation from one WDM channel to another WDM channel can appear as power fluctuations caused by dispersion of the optical signal. Therefore, XPM compensators are known that modulate the entire optical path or span between two nodes. Although some XPM compensation systems may be effective in improving signal quality when there are relatively few channels (less than about 15 channels), certain XPM compensation systems are actually As the number of channels increases (more than about 15 channels), it may have a negative effect on the optical signal-to-noise ratio (OSNR).

  As described in further detail herein, a method and system for implementing a multi-channel optical XPM compensator is disclosed herein. The multi-channel optical XPM compensator disclosed herein can allow XPM to be compensated for all channels in a multi-channel WDM optical signal, even for many channels greater than 15 channels. The multi-channel optical XPM compensator disclosed herein may provide a forward feedback XPM compensation loop having a dispersion compensation module (DCM) that simulates dispersion along the effective length of a subsequent optical fiber span. . The multi-channel optical XPM compensator disclosed herein can further be used in a configuration that allows simultaneous XPM compensation for all WDM channels without introducing delay in the propagation of individual WDM channels. The multi-channel optical XPM compensator disclosed herein can be implemented using various spectral overlap schemes that optimize XPM compensation.

  In the operation of the optical network 101, for example, the ROADM node included in the optical network 101 may be provided with the multi-channel optical XPM compensator disclosed in the present specification.

  Referring to FIG. 2A, a block diagram of selected elements of an exemplary embodiment of XPM compensator 200-1 is shown. In FIG. 2A, the XPM compensator 200-1 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 200-1 may be operated with additional or fewer elements.

  In FIG. 2A, the XPM compensator 200-1 includes a forward feedback control loop extending from an optical tap 202 disposed along a WDM optical path having an input WDM optical signal 210 and an output WDM optical signal 220 to the phase modulator 204. Including. Note that in different embodiments, different configurations of components in the forward feedback loop may be implemented in both the optical and electrical domains. At optical tap 202 (also referred to as an optical splitter), a portion of the input WDM optical signal 210 is directed to the forward feedback control loop. Specifically, the DCM 206 receives an optical signal from the optical tap 202 and forward-feedback to enable XPM compensation of the optical signal within the effective length of the optical fiber after the XPM compensator 200-1. A specific amount of variance can be added to the control loop. Since chromatic dispersion (CD) results in pulse broadening and inter-symbol interference (ISI), the addition of dispersion in DCM 206 is caused by power signal variations along the effective length. By simulating the XPM, the XPM compensation in the forward feedback loop can be improved. Specifically, the variance may correspond to the calculated portion of the effective length. Here, the part is between 0 and 1. After DCM 206, photodiode 212 (or another type of light sensor) receives the light signal in the forward feedback loop and generates a corresponding electrical signal. As shown in the XPM compensator 200-1, the RF amplifier 208 may then amplify the electrical signal received from the photodiode 212. Next, a low pass filter (LPF) 213 may be applied to the electrical signal output by the RF amplifier 208. After LPF 213 and before outputting an electrical signal to phase modulator 204, variable delay 214 applies a time delay to compensate for path length variations. In the exemplary configuration of FIG. 2A, the optical path between tap 202 and phase modulator 204 is such that the variable delay 214 is the delay between the optical signal arriving at phase modulator 204 and the forward feedback signal at variable delay 214. Is assumed to be sufficiently long so that can be adjusted or matched. The phase modulator 204 operates to modulate the phase of the WDM input optical signal 210 based on the received portion of the WDM input optical signal 210 from the optical tap 202 to generate an XPM compensated output WDM optical signal 220. obtain.

  Referring to FIG. 2B, a block diagram of selected elements of an exemplary embodiment of XPM compensator 200-2 is shown. In FIG. 2B, the XPM compensator 200-2 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 200-2 may be operated with additional or fewer elements.

  In FIG. 2B, XPM compensator 200-2 includes all of the same elements as shown for XPM compensator 200-1 in FIG. 2A. Additionally, the XPM compensator 200-2 can be used to select an optical band, such as an optical band that includes a discontinuous number of optical channels, from the input WDM optical signal 210. OBPF) 216. When PBPF 216 is used to separate the center wavelength (non-edge wavelength) channel, some improvement in XPM can be observed for the center wavelength channel. However, since the OBPF 216 uses a narrower bandwidth than the input WDM optical signal 210 for the forward feedback loop, the edge wavelength channel XPM compensation may suffer. This is because signal strength from neighboring channels outside the range of the band pass of OBPF 216 is not detected for forward feedback compensation and does not contribute to XPM compensation in XPM compensator 200-2.

  Referring to FIG. 2C, a block diagram of selected elements of an exemplary embodiment of XPM compensator 200-3 is shown. In FIG. 2C, the XPM compensator 200-3 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 200-3 may be operated with additional or fewer elements.

  In FIG. 2C, the XPM compensator 200-3 includes a forward feedback control loop that receives the external input 222 and does not rely on the optical tap 202 from the input WDM optical signal 210. In this manner, the XPM compensator 200-3 may be integrated into various ROADM environments that use WSS (see also FIG. 6). After receiving external input 222, the forward feedback loop in XPM compensator 200-3 may include the same elements as described above with respect to XPM compensator 200-2 in FIG. 2B.

  Referring to FIG. 3, selected elements of one embodiment of an example XPM compensation 300 are shown. In FIG. 3, the XPM compensation example 300 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensation example 300 may include additional or fewer elements.

  In the XPM compensation example 300 shown in FIG. 3, the input WDM optical signal 310 is assumed to be composed of nine wavelength channels continuously indicated as λ1 to λ9. Note that in various embodiments, a different number of channels may be included in the input WDM optical signal 310, and a different number of XPM compensators 200 may be used in a variety of different spectrum allocation schemes as needed. . XPM compensation example 300 illustrates a spectrum allocation scheme in which three examples of XPM compensator 200-1 are used in parallel to compensate for XPM in the subband of input WDM optical signal 310. At splitter 304, the input WDM optical signal 310 is split into three separate fibers to parallel OBPFs 308-1, 308-2, 308-3. Each OBPF 308 may be programmed to pass a specific subband of the input WDM optical signal 310. In the exemplary embodiment shown in FIG. 3, each OBPF 308 passes a subband that includes three wavelength channels. Accordingly, the OBPF 308-1 passes the wavelengths λ1, λ2, and λ3, the OBPF 308-2 passes the wavelengths λ4, λ5, and λ6, and the OBPF 308-3 passes the wavelengths λ7, λ8, and λ9. At combiner 306, the XPM compensated subbands are combined to form output WDM optical signal 320.

  Referring to FIG. 4, selected elements of one embodiment of an example XPM compensation 400 are shown. In FIG. 4, the XPM compensation example 400 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensation example 400 may include additional or fewer elements.

  The XPM compensation example 400 shown in FIG. 4 shows a configuration using WSSs 404 and 406 instead of the splitter 304 and combiner 306 from FIG. Compared to splitter 304 and combiner 306, the use of two WSSs provides the ability to select individual channels to add and drop from the subband. In an exemplary embodiment, the same spectrum allocation scheme described above with respect to FIG. 3 may be implemented using the example XPM compensation 400. Here, the WSS 404 passes each subband from the input WDM optical signal 310 to each XPM compensator 200-1 in parallel. On the other hand, the WSS 406 is used to recombine the subbands to the XPM compensated output WDM optical signal 320. Note that in various embodiments, a different number of channels may be included in the input WDM optical signal 310, and a different number of XPM compensators 200 may be used in a variety of different spectrum allocation schemes as needed. .

  Further, it should be noted that the example XPM compensation 400 of FIG. 4 may be used to implement a variety of different spectrum allocation schemes, as described below with respect to FIG.

  Referring to FIG. 5, selected elements of one embodiment of an example XPM compensation 500 are shown. In FIG. 5, the XPM compensation example 500 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensation example 500 may include additional or fewer elements.

  In the XPM compensation example 500 shown in FIG. 5, the input WDM optical signal 310 is assumed to be composed of nine wavelength channels as shown in FIG. Note that in various embodiments, a different number of channels may be included in the input WDM optical signal 310, and a different number of XPM compensators 200 may be used in a variety of different spectrum allocation schemes as needed. . XPM compensation example 500 illustrates a spectrum allocation scheme in which three examples of XPM compensator 200-1 are used in parallel to compensate for XPM in the subband of input WDM optical signal 310. At splitter 304, the input WDM optical signal 310 is split into three separate fibers to parallel OBPFs 308-1, 308-2, 308-3. Each OBPF 308 may be programmed to pass a specific subband of the input WDM optical signal 310. In the exemplary embodiment shown in FIG. 5, each OBPF 308 passes a subband that includes a different number of wavelength channels. As shown, OBPF 308-1 passes wavelengths λ1, λ2, λ3, λ4, OBPF 308-2 passes wavelengths λ2, λ3, λ4, λ5, λ6, λ7, and OBPF 308-3 passes wavelengths λ5, λ6, Let λ7, λ8, and λ9 pass. Next, in the XPM compensation example 500, the second OBPF 516 is used to remove overlapping wavelength channels. Therefore, the OBPF 516-1 passes the wavelengths λ1, λ2, and λ3, the OBPF 516-2 passes the wavelengths λ4, λ5, and λ6, and the OBPF 516-3 passes the wavelengths λ7, λ8, and λ9. The use of overlapping spectra in the XPM compensation example 500 can improve XPM compensation within the individual forward feedback loops of the XPM compensator 200-1, while channels with poor XPM compensation can be dropped. Note that gain equalization (not shown) may be applied in the XPM compensation example 500 after OBPF 516 depending on the actual spectral overlap scheme used. The XPM compensated subbands are then combined at combiner 306 to form output WDM optical signal 320.

  Note that the spectrum allocation described above may be implemented using the example XPM compensation 400 shown in FIG. For example, the first WSS 404 may switch the spectral subband of the wavelength channel to the individual XPM compensator 200-1, while the second WSS 406 may drop the overlapping wavelength channel.

  Referring to FIG. 6, selected elements of one embodiment of an example XPM compensation 600 are shown. In FIG. 6, the XPM compensation example 600 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensation example 600 may include additional or fewer elements.

  In the XPM compensation example 600 shown in FIG. 6, the input WDM optical signal 310 is assumed to be composed of nine wavelength channels as shown in FIG. Note that in various embodiments, a different number of channels may be included in the input WDM optical signal 310, and a different number of XPM compensators 200 may be used in a variety of different spectrum allocation schemes as needed. . XPM compensation example 600 illustrates a spectrum allocation scheme in which three examples of XPM compensator 200-3 are used in parallel to compensate for XPM in the subband of input WDM optical signal 310. In splitter 304, input WDM optical signal 310 may be split in parallel into four separate fibers. One fiber may be used as the input level 602 of the WSS 404, while the other three fibers may be used as the external input 222 of the individual XPM compensator 200-3. Each OBPF 216 (see FIG. 2C) in the XPM compensator 200-3 may be programmed to pass a specific subband of the external input 222. Here, the specific sub-band carries the input WDM optical signal 310. In the exemplary embodiment shown in FIG. 6, output stage 610-1 from WSS 404 may pass wavelengths λ1, λ2, and λ3, and output stage 610-2 from WSS 404 passes wavelengths λ4, λ5, and λ6. The output stage 610-3 from the WSS 404 may pass wavelengths λ7, λ8, and λ9. At the same time, each external input signal 222 passes through the OBPF 216 in the individual XPM compensator 200-3. Accordingly, the external input signal 222-1 is spectrally narrowed down to the pass subband having wavelengths λ1, λ2, λ3, and λ4, and the external input signal 222-2 has wavelengths λ2, λ3, λ4, λ5, λ6, and λ7. The external input signal 222-3 is spectrally narrowed to pass subbands having wavelengths λ5, λ6, λ7, λ8, and λ9. Note that in some embodiments, the external input signal 222-2 may be narrowed using an OBPF that is external to the XPM compensator 200-3. Next, the XPM compensated subband 620-1 includes wavelengths λ1, λ2, and λ3, the XPM compensated subband 620-2 includes wavelengths λ4, λ5, and λ6, and the XPM compensated subband 620-3 includes , Including wavelengths λ7, λ8, and λ9. The use of overlapping spectra in the XPM compensation example 600 can improve XPM compensation in the individual forward feedback loops of the XPM compensator 200-3, while channels with poor XPM compensation can be dropped. Note that gain equalization (not shown) may be applied in the XPM compensation example 600, depending on the actual spectral overlap scheme used. The XPM compensated subbands 620 are then combined at WSS 406 to form output WDM optical signal 320.

  Referring to FIG. 7A, a block diagram of selected elements of an exemplary embodiment of an XPM compensator 700-1 with polarization diversity is shown. In FIG. 7A, the XPM compensator 700-1 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 700-1 may be operated with additional or fewer elements.

In FIG. 7A, the input WDM optical signal 710 has polarization diversity, and therefore it is assumed that there are X and Y polarization components of the optical signal. XPM compensator 700-1 includes a forward feedback control loop extending from optical tap 202 disposed along a WDM optical path having an input WDM optical signal 710 and an output WDM optical signal 720 to phase modulator 704. At optical tap 202 (also referred to as an optical splitter), a portion of the input WDM optical signal 710 is directed to the forward feedback control loop. Specifically, as described above with respect to FIG. 2A, the DCM 206 can receive the optical signal from the optical tap 202 and add a certain amount of variance to the forward feedback control loop. After the DCM 206, a polarization beam splitter (PBS) 702 further divides the optical signal into an X polarization component and a Y polarization component. The X polarization component is supplied from the PBS 702 to the photodiode 212-X. The photodiode 212-X generates an electrical signal that is amplified by the RF amplifier 208-X and filtered using the LPF 213-X. The Y polarization component is supplied from the PBS 702 to the photodiode 212-Y. The photodiode 212-Y generates an electrical signal amplified by the RF amplifier 208-Y and filtered using the LPF 213-Y. Next, from the LPFs 213-X and 213-Y, the variable coupler 722 uses the inputs p and q and the outputs r and s so that r = h ₁₁ p + h ₁₂ q and s = h ₂₁ p + h ₂₂ q. It can be applied to electrical signals. Here, h is a weighting coefficient. In one example, h ₁₁ = h ₁₂ = h ₂₁ = h ₂₂ = 0.5. However, different values may be used differently in the embodiments. In addition, variable delays 714-X and 718-X are used for the X polarization component signal before and after variable coupler 722, while variable delays 714-Y and 718-Y are for the Y polarization component. Used before and after the variable coupler 722. Next, the variable delay 718-X outputs a control signal for the X polarization component to the X phase modulator 704-X, and the variable delay 718-Y outputs the control signal for the Y polarization component to Y. Output to the phase modulator 704-Y to generate an XPM compensated output WDM optical signal 702 having polarization diversity.

  Referring to FIG. 7B, a block diagram of selected elements of an exemplary embodiment of an XPM compensator 700-2 with polarization diversity is shown. In FIG. 7B, the XPM compensator 700-2 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 700-2 may be operated with additional or fewer elements.

  In FIG. 7B, the input WDM optical signal 710 has polarization diversity, so it is assumed that there are X and Y polarization components of the optical signal. XPM compensator 700-2 includes a forward feedback control loop extending from optical tap 202 disposed along a WDM optical path having an input WDM optical signal 710 and an output WDM optical signal 720 to phase modulator 204. Input WDM optical signal 710 is received at PBS 702. The PBS 702 separates the X polarization component and the Y polarization component along different optical fibers. In the optical tap 202-X, a part of the X polarization component is directed to the X polarization forward feedback control loop. On the other hand, in the optical tap 202-Y, a part of the Y polarization component is directed to the Y polarization front feedback control loop. Specifically, as described above with respect to FIG. 2A, within the X polarization forward feedback control loop, the DCM 206-X receives the optical signal from the optical tap 202-X and places a certain amount of dispersion into the X forward feedback control loop. Can be added. On the other hand, within the Y polarization forward feedback control loop, the DCM 206-Y can receive the optical signal from the optical tap 202-Y and add a certain amount of dispersion to the Y forward feedback control loop. After the DCM 206-X, the X polarization component is supplied to the photodiode 212-X. The photodiode 212-X generates an electrical signal that is amplified by the RF amplifier 208-X and filtered using the LPF 213-X. After the DCM 206-Y, the Y polarization component is supplied to the photodiode 212-Y. The photodiode 212-Y generates an electrical signal amplified by the RF amplifier 208-Y and filtered using the LPF 213-Y. As described above with respect to FIG. 7A, the variable coupler 722 may be applied to the electrical signals from the LPFs 213-X, 213-Y and the variable delay used before and after the variable coupler 722 for the X polarization component signal. It includes variable delays 714-Y and 718-Y used before and after variable coupler 722 for 714-X and 718-X and Y polarization component signals. Next, the variable delay 718-X outputs a control signal for the X polarization component to the first phase modulator 204-1, and the variable delay 718-Y outputs a control signal for the Y polarization component. Output to the second phase modulator 204-2. The output signal from phase modulator 204 is combined in polarization beam combiner 724 to produce an XPM compensated output WDM optical signal 720 having polarization diversity.

  Referring to FIG. 7C, a block diagram of selected elements of an exemplary embodiment of an XPM compensator 700-3 with polarization diversity is shown. In FIG. 7C, the XPM compensator 700-3 is shown in schematic representation and not to scale. It should be noted that in different embodiments, the XPM compensator 700-3 may be operated with additional or fewer elements.

In FIG. 7C, the input WDM optical signal 710 has polarization diversity, so it is assumed that there are X and Y polarization components of the optical signal. XPM compensator 700-3 includes a forward feedback control loop that extends from optical tap 202 disposed along a WDM optical path having an input WDM optical signal 710 and an output WDM optical signal 720 to phase modulator 704. At optical tap 202, a portion of the input WDM optical signal 710 is directed to the forward feedback control loop. Specifically, as described above with respect to FIG. 2A, the DCM 206 can receive the optical signal from the optical tap 202 and add a certain amount of variance to the forward feedback control loop. Photodiode 212, RF amplifier 208, and LPF 213 operate in a manner substantially similar to that described above with respect to FIG. 2A. After LPF 213, the electrical signal is supplied to variable delay 714-X and variable delay 714-Y to adjust for the X and Y polarization components. The configuration shown in FIG. 7C may be substantially equivalent to the use of a variable coupler with h ₁₁ = h ₁₂ = h ₂₁ = h ₂₂ = 0.5 as shown in FIG. 7A. Next, the variable delay 714-X outputs a control signal for the X polarization component to the X phase modulator 704-X, and the variable delay 714-Y outputs the control signal for the Y polarization component to Y. Output to the phase modulator 704-Y to generate an XPM compensated output WDM optical signal 702 having polarization diversity.

  Referring to FIG. 7D, a block diagram of selected elements of an exemplary embodiment of an XPM compensator 700-4 with polarization diversity is shown. In FIG. 7D, the XPM compensator 700-4 is shown in schematic representation and not to scale. It should be noted that in different embodiments, XPM compensator 700-4 may be operated with additional or fewer elements.

In FIG. 7D, the input WDM optical signal 710 has polarization diversity, and therefore it is assumed that there are X and Y polarization components of the optical signal. XPM compensator 700-4 includes a forward feedback control loop extending from optical tap 202 disposed along a WDM optical path having an input WDM optical signal 710 and an output WDM optical signal 720 to phase modulator 204. At optical tap 202, a portion of the input WDM optical signal 710 is directed to the forward feedback control loop, while the remaining portion is directed to PBS 702. Specifically, as described above with respect to FIG. 2A, the DCM 206 can receive the optical signal from the optical tap 202 and add a certain amount of variance to the forward feedback control loop. Photodiode 212, RF amplifier 208, and LPF 213 operate in a manner substantially similar to that described above with respect to FIG. 2A. After LPF 213, the electrical signal is supplied to variable delay 714-X and variable delay 714-Y to adjust for the X and Y polarization components. The configuration shown in FIG. 7D may be substantially equivalent to the use of a variable coupler with h ₁₁ = h ₁₂ = h ₂₁ = h ₂₂ = 0.5 as shown in FIG. 7A. Next, the variable delay 714-X outputs a control signal for the X polarization component to the first phase modulator 204-1, and the variable delay 714-Y outputs a control signal for the Y polarization component. Output to the second phase modulator 204-2. The first phase modulator 204-1 receives the X polarization component from the PBS 702, while the second phase modulator 204-2 receives the Y polarization component from the PBS 702. The outputs from the first and second phase modulators 204 corresponding to the X polarization component and the Y polarization component are combined at the PBC 724 to produce an XPM compensated output WDM optical signal 720 having polarization diversity.

  Referring to FIG. 8, a flowchart of selected elements of one embodiment of a method 800 for XPM compensation, as described herein, is shown. In various embodiments, the method 800 may be performed using XPM compensators 200, 700 in ROADM nodes in an optical network, eg, corresponding to XPM compensation examples 400, 600. It should be noted that the specific operations described in method 800 may be optional or rearranged in different embodiments.

  The method 800 may begin at step 802, switching between adjacent channel groups included in a WDM optical signal supplied as an input to the first WSS. In step 8024, a first group of adjacent channel groups is received from a first WSS at a first XPM compensator that includes a DCM. At step 806, the XPM compensated first group is received at the second WSS.

  Referring to FIG. 9, a flowchart of selected elements of one embodiment of a method 900 for XPM compensation, as described herein, is shown. In various embodiments, method 900 may be performed using XPM compensator 200, 700 in a ROADM node in an optical network, eg, in XPM compensation examples 400, 600. It should be noted that certain operations described in method 900 may be optional or rearranged in different embodiments.

  The method 900 may begin at step 902 and generate an XPM control signal using a forward feedback XPM adjustment loop. The forward feedback XPM adjustment loop includes DCM to add dispersion corresponding to a portion of the effective length of the optical fiber span that carries the WDM optical signal following the second WSS. In step 902, the first group and the XPM control signal are transmitted to the phase modulator to output an XPM compensated first group.

  As disclosed herein, a method and system for multi-channel optical XPM compensation may include a DCM that improves the performance of a forward feedback control loop in an optical path in an optical network. In addition, various spectral overlap schemes may be used with multi-channel WDM optical signals using XPM compensators in parallel, as in ROADM nodes. Polarization diversity may also be supported for XPM compensation including DCM.

<Network management by cross phase modulation (XPM) compensation per node: selective (XPM) compensation>
Various aspects of optical XPM compensation have been described in detail with respect to FIGS. 10-16, network management with per-node XPM compensation is described using selective XPM compensation for a specific wavelength.

  In a further aspect, selective XPM compensation of the optical signal may also be performed. Selective XPM compensation may be performed when at least two wavelength groups for transmission to different destinations are present at the common source node of their respective optical paths. Each wavelength group may be selected based on the distance of the optical path from the common source node to their individual destination nodes. For example, the optical path length is calculated between the common start node and the destination node for each wavelength. Due to different network topologies such as linear, ring, mesh, etc. that can be interconnected and used to route different wavelengths to different destinations, certain wavelengths in the optical signal can be optical networks over different distances. May propagate.

  Specifically, the wavelengths can be grouped into short traveling wavelengths (STW) and long traveling wavelengths (LTW) based on the optical path length of each individual group. In a common source node transmitter, a specific threshold of optical path length, such as 10 km, 50 km, 100 km, 150 km, 200 km, or 250 km, is used in various embodiments to distinguish between STW and LTW. Good. In some embodiments, the threshold path distance used to distinguish between STW and LTW may be determined based at least in part on the XPM characteristics of the optical signal being transmitted by each wavelength. In certain embodiments, the transmitters 102 at the common source node may receive path information for each wavelength from the path computation engine (PCE) of the network controller (see also FIG. 17). The path information may include the length of the optical path from the common source node for each individual wavelength. Then, based on the optical path length and the threshold used, each wavelength may be assigned as an LTW or STW at the common source node.

  In addition, after grouping the wavelengths into STW and LTW at the common source node, the wavelength group is spectrally transmitted by the transmitter 102 to achieve STW and LTW separation at any subsequent nodes along the optical path. May be spaced. In other words, a guard band may be applied between the STW group and the LTW group in order to separate the groups from each other with spectral separation. The spectral spacing may be selected based on at least one wavelength slot width and may be several wavelength slot widths. In some implementations, a particular optical bandwidth may be allocated for transmission of wavelength groups (both STW and LTW) at the common source node transmitter 102. Thus, the STW group is assigned to one end of the optical bandwidth, while the LTW is assigned to the other end of the optical bandwidth, and the resulting guard band between the STW group and the LTW group is all wavelengths Is determined by the remaining bandwidth left after being assigned to those individual wavelength slots. Various other ways of grouping STW and LTW apart are possible.

  After starting from a common source node, the STW and LTW may propagate together during at least the first part of their respective optical paths with a spectral distance interval between the STW group and the LTW group. The STW and LTW may then be sent to a specific node with ROADM. With ROADM, wavelength specific switches and routing may be performed. The ROADM node may be capable of ROADM for selective XPM compensation, as described herein. Specifically, XPM compensation may be performed for the LTW in the ROADM that transmits the STW and the LTW, and may be omitted for the STW. The selective application of XPM compensation makes sense because the effect of XPM on STW is small compared to the effect of XPM on LTW. By reducing the number of wavelengths subject to XPM compensation, the resources associated with XPM compensation at each node may be reduced compared to applying XPM compensation to all wavelengths, as described herein. This is economically advantageous. For example, a specific ROADM node capable of selective XPM compensation may be provided with fewer WSS ports and fewer optical band pass filters (OPBF). This can reduce equipment costs at such nodes without any substantial adverse effect on the transmission of optical signals.

FIG. 10 shows a spectrum 1000 of spectrally grouped wavelengths in an optical signal grouped into LTW and STW. Specifically, in spectrum 1000, wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ are shown grouped together as an LTW on one side of the spectrum. On the other hand, the wavelengths λ ₅ , λ ₆ , λ ₇ , λ ₈ are shown grouped together as STWs on the other side of the spectrum. Spectral gaps or guard bands are shown in FIG. 10 as a free area between λ ₄ and λ ₅ and the separation of LTW and STW as individual wavelength groups by using optical filtering or optical demultiplexing at the ROADM node. It can be realized. The grouping shown in spectrum 1000 is based on controlling the transmitter 102 (see FIG. 1) for each individual wavelength, as described above, and the path when optical signals are transmitted from a common source node. This can be done by using PCE for length determination. For illustrative purposes in FIG. 10, it is shown that the STW and LTW are each grouped by four wavelengths, but it is understood that in different embodiments, different numbers of STWs and LTWs may be grouped together, respectively. The

  Referring to FIG. 11, a block diagram of selected elements of one embodiment of ROADM 1100 with selective XPM compensation is shown. The ROADM 1100 shows a post-compensation method in which XPM is compensated after transmission of an optical signal, and the added optical signal is not XPM compensated. The ROADM 1100 may therefore be used along the optical path of an optical signal, such as inside a node in the optical network 101. Note that the ROADM 1100 may be provided with fewer or more elements than those shown in FIG. 11 in different embodiments. In FIG. 11, the XPM compensation unit 1101 is shown implemented in the ROADM 1100 and will be used below to explain the function of the ROADM 1100. As shown in FIG. 11, the XPM compensation unit 1101 may represent any of the above-described exemplary configurations 300, 400, 500, or 600 (see FIGS. 3-6). In particular, the XPM compensation unit 1101 may use the OPBF 308 or the OPBF 308 to enable separation of the first group of STWs from the second group of LTWs as shown in the spectrum 1000 of FIG. 10 for wavelength specific optical processing including XPM compensation. It has a specific wavelength selection element such as WSS404.

  Accordingly, FIG. 11, ROADM 1100 has multiple wavelengths, such as the exemplary optical signal in spectrum 1000 of FIG. 10 that is spectrally divided into a first group of STWs and a second group of LTWs as described above. An optical signal 1102 including In a fiber optic splitter 1104, which can be a passive filter, the optical signal 1102 is separated, for example, with the same optical power, so that it is directed to the WSS 1106 and to the splitter 1108, with each output from the splitter 1104 being in a first group. Includes STW and second group of LTWs. The WSS 1106 may receive both STW and LTW from the splitter 1104, but may send only certain of the STWs to the output optical signal 1112, while directly from the splitter 1104 that is not XPM compensated. Block incoming LTW. Thus, any selected one of the STWs in the optical signal 1102 may be passed to the output optical signal 1112 without XPM compensation.

  Further, the splitter 1108 may receive both the first group of STWs and the second group of LTWs from the splitter 1104. The splitter 1108 may be a passive splitter with a corresponding decrease in output optical power and may output the first group of STWs and the second group of LTWs to the XPM compensation unit 1101 and to the drop port 1116.

  At the drop port 1116, certain some of the STWs may be dropped without XPM compensation, such as the STW when the ROADM 1100 is at the destination node. Specifically, the STW dropped at drop port 1116 is received by one or more receivers (not shown in FIG. 11) having spectrum filtering capability to receive and demodulate one wavelength per receiver. good. Thus, when multiple STWs are dropped at drop port 1116, multiple corresponding receivers are used. An LTW arriving at drop port 1116 is not received by any receiver, as is an STW that is not dropped, and is therefore effectively terminated. For specific STWs dropped and received at drop port 1116, WSS 1106 may be configured to block these specific STWs from output optical signal 1112 and prevent duplicate transmissions of the same STW. From splitter 1108, both the first group of STWs and the second group of LTWs may be passed to XPM compensation unit 1101 for XPM compensation, as disclosed herein.

  In XPM compensation unit 1101, both the first group of STWs and the second group of LTWs are received from splitter 1108, and as described above, the first group of STWs may be terminated, while the second group of LTWs is It may be XPM compensated. For example, OPBF 308 or WSS 404 may be used to terminate the STW in XPM compensation unit 1101 in different implementations.

  After XPM compensation unit 1101, second optical fiber splitter 1110, which may be a passive splitter, may output XPM compensation LTW to WSS 1106 and to drop port 1118. At the drop port 1118, the XPM compensated LTW arriving at each destination node in the ROADM 1100 is dropped and received as described above for the drop port 1116. Similar to drop port 1116, for a specific XPM compensated LTW dropped at drop port 1118, WSS 1106 blocks the specific LTW dropped at drop port 1118 from output optical signal 1112, and drops the desired single LTW. It may be configured to maintain a single light path. LTWs that are not dropped at drop port 1118 are switched by WSS 1106 to output optical signal 1112 for inclusion in the XPM compensated second group of LTWs.

  The ROADM 1100 also shows an input stage 1114 to the WSS 1106 that can be used to add a new STW or LTW or both to the output optical signal 1112 that can be XPM compensated at a subsequent ROADM node (not shown). Although the ROADM 1100 has been configured and shown with three fiber optic splitters 1104, 1108, and 1110, it will be understood that different numbers of fiber optic splitters, optical filters, and demultiplexers may be used in different configurations. . In certain embodiments, one or more additional WSSs (not shown in FIG. 11) may be used to enable dynamic or programmable wavelength switching, for example, instead of splitters 1104, 1108, 1110, or for any desired optical power. Can be used for control.

  Referring to FIG. 12, a block diagram of selected elements of one embodiment of ROADM 1200 with selective XPM compensation is shown. In ROADM 1200, a pre-compensation scheme is shown in which XPM can be compensated before transmitting the added LTW. ROADM 1200 may therefore be used along the optical path of an optical signal, such as inside a node in optical network 101 that interconnects two network segments. Note that ROADM 1200 may be provided with fewer or more elements than shown in FIG. 12 in different embodiments. In FIG. 12, XPM compensation units 1101-A, 1101-B are shown implemented in ROADM 1200 and are used to describe the functionality of ROADM 1200 below. As shown in FIG. 12, XPM compensation units 1101-A, 1101-B represent any of the above-described exemplary configurations 300, 400, 500, or 600 (see FIGS. 3-6). good. In particular, the XPM compensation units 1101-A and 1101-B can separate the first group of STWs from the second group of LTWs as shown in the spectrum 1000 of FIG. 10 for wavelength specific optical processing including XPM compensation. In order to do this, it has specific wavelength selection elements such as OPBF308 or WSS404.

  The ROADM 1200 of FIG. 12 is the same as the operation of the ROADM 1100 described above with reference to FIG. Specifically, ROADM 1200 includes an optical signal 1102 that includes multiple wavelengths, such as the exemplary optical signal shown in spectrum 1000, that is spectrally divided into a first group of STWs and a second group of LTWs. You can receive it. With an optical fiber splitter 1104, which may be a passive filter, the optical signal 1102 is separated, for example, with the same optical power, so that each output from the splitter 1104 is first to be directed to the WSS 1106 and the second splitter 1108 It includes the STW of the group and the LTW of the second group. At splitter 1108, drop port 1216 is received by a receiver with spectral filtering capability, for example, where dropped STW / LTW arrives at their destination node and isolates a single wavelength using a single receiver. XPM uncompensated STW and LTW drop is enabled. Thus, when multiple STWs or LTWs are dropped and received at drop port 1216, multiple corresponding receivers are used. An undropped LTW / STW arriving at drop port 1216 is not received by any receiver and is therefore effectively terminated. For certain STW / LTWs dropped and received at drop port 1216, WSS 1106 is configured to terminate dropped STW / LTWs and block their transmission to output optical signal 1112. Also from the splitter 1108, the first group of STWs and the second group of LTWs are received by the XPM compensation unit 1101-A. In the XPM compensation unit 1101-A, the first group of STWs may be terminated by wavelength specific blocks using, for example, OPBF308 or WSS404. Next, in the XPM compensation unit 1101 -A, the second group of LTWs may be XPM compensated and output to the WSS 1106. Another XPM compensation unit 1101-B may receive the added LTW without XPM compensation at the add port 1218, and may XPM compensate the added LTW. The XPM compensated added LTW is then output from the XPM compensation unit 1101-B to the WSS 1106.

  ROADM 1200 also shows an input stage 1202 to WSS 1106 that may be used to add additional STWs to output optical signal 1112. Although ROADM 1200 has been constructed and shown with fiber optic splitters 1104 and 1108, it is understood that different numbers of fiber optic splitters, optical filters, and demultiplexers may be used in different configurations. In certain embodiments, one or more additional WSSs (not shown in FIG. 12) may be used to enable dynamic or programmable wavelength switching, for example, instead of splitter 1104, or for desired control of optical power. Can be used ,.

  Figures 13-15 show different embodiments of ring interconnects where two optical networks are fused. Specifically, the first ring having nodes N, N + 1 and N + 2 is shown to merge at node N + 1 with another ring having node M. In each figure, a specific spectrum is shown and the output of the optical signal for each node labeled in the spectrum is shown.

  Referring to FIG. 13, a network diagram of selected elements of one embodiment of a ring interconnect 1300 with selective XPM compensation is shown. In the ring interconnect 1300, the first ring 1302 is composed of nodes 1304-N, 1304-N + 1, and 1304-N + 2. A second ring 1306 having nodes 1304-M interconnects with the first ring 1302 at node 1304N + 1. In ring interconnect 1300, node 1304 is assumed to include XPM compensation, for example, by including ROADM with selective XPM compensation as described herein. Accordingly, the first ring 1302 and the second ring 1306 are XPM compensation rings.

  After node 1304-N along the first ring 1302, spectrum N shows four wavelengths, respectively, for the LTW group and the STW group, respectively. After node 1304-M along second ring 1306, spectrum M shows two wavelengths respectively for the LTW group and the STW group. After second ring 1306 merges with first ring 1302 at node 1304-N + 1, spectrum N + 1 indicates that each LTW group and STW group includes six wavelengths. Accordingly, the node 1304 in the ring interconnect 1300 may perform XPM compensation for the LTW group, while leaving the STW group uncompensated by passing the STW group.

  In one embodiment of the ring interconnect 1300, the first ring 1302 and the second ring 1306 have the same fiber type. In another embodiment of the ring interconnect 1300, the first ring 1302 may comprise SMF type fiber, while the second ring 1306 comprises NZ-DSF type fiber. Since both the first ring 1302 and the second ring 1306 are XPM compensated for the LTW, the NZ-DSF type fiber has greater nonlinearity than the SMF type fiber, and the STW remains uncompensated. Good.

  Referring to FIG. 14, a network diagram of selected elements of one embodiment of a ring interconnect 1400 with selective XPM compensation is shown. In the ring interconnect 1400, the first ring 1402 is composed of nodes 1404-N, 1404-N + 1, and 1404-N + 2. A second ring 1406 having nodes 1404-M interconnects with the first ring 1402 at node 1404N + 1. In ring interconnect 1400, node 1404 in first ring 1402 is assumed to include XPM compensation, for example, by including ROADM with selective XPM compensation as described herein. On the other hand, the node 1404 in the second ring 1406 is not XPM compensated. Thus, the first ring 1402 is XPM compensated while the second ring 1406 is not XPM compensated. Further, in the ring interconnect 1400, the first ring 1402 may comprise SMF type fibers, while the second ring 1406 comprises NZ-DSF type fibers with stronger fiber nonlinearity.

  After node 1404-N along the first ring 1402, spectrum N shows four wavelengths respectively for the LTW group and the STW group, respectively. After node 1404-M along the second ring 1406, spectrum M shows two wavelengths for the mixed and ungrouped LTW and STW, respectively, representing any mixed configuration of the LTW and STW. In this configuration, the STW that arrives at the node 1404-N + 1 can also benefit from XPM compensation. In this case, all wavelengths in spectrum M have been added to the LTW in spectrum N + 1 at node 1404-N + 1 and now have 8 LTWs. Therefore, the node 1404-N + 1 can handle all wavelengths coming from the second ring 1406 as LTW for the purpose of XPM compensation, and does not distinguish wavelengths coming from the second ring 1406 as STW or LTW. After XPM compensation of eight LTWs at node 1404-N + 1, at node 1404-N + 2, the STW from the second ring 1406 is converted to EO-O conversion, wavelength shifter, or first ring 1402 and second ring 1406. Are reassigned to STWs using wavelength conversion, such as by pre-planning specific wavelength assignments. For example, node 1404-N + 2 may receive wavelength assignment information from a network controller (see FIG. 17) that tracks or controls the wavelength assignment at each node 1404, and which LTW wavelength in spectrum N + 1 is in spectrum N + 2. Can be reassigned to the STW. After node 1404-N + 2, the LTW group and STW group have been reassigned as shown in spectrum N + 2 with 4 LTWs and 4 STWs grouped together.

  Referring to FIG. 15, a network diagram of selected elements of one embodiment of a ring interconnect 1500 with selective XPM compensation is shown. In the ring interconnect 1500, the first ring 1502 is composed of nodes 1504-N, 1504-N + 1, and 1504-N + 2. A second ring 1506 having nodes 1504-M interconnects with the first ring 1502 at node 1504N + 1. In ring interconnect 1500, node 1504 in first ring 1502 is assumed to include XPM compensation, for example, by including ROADM with selective XPM compensation as described herein. On the other hand, the node 1504 in the second ring 1506 is not XPM compensated. Thus, the first ring 1502 is XPM compensated while the second ring 1506 is not XPM compensated.

  In one embodiment of the ring interconnect 1500, the first ring 1502 and the second ring 1506 have the same fiber type. In another embodiment of the ring interconnect 1500, the first ring 1502 may comprise NZ-DSF type fiber, while the second ring 1506 comprises SMF type fiber with less fiber nonlinearity.

  After node 1504-N along the first ring 1502, spectrum N shows four wavelengths respectively for the LTW group and the STW group, respectively. After node 1504-M along the second ring 1506, spectrum M shows two wavelengths for LTW and STW, respectively, which are mixed and ungrouped, representing any mixed configuration of LTW and STW. In this configuration, the STW arriving at node 1504-N + 1 will receive the XPM regardless of whether the fiber type is the same or whether the second ring 1506 has an SMF fiber and the first ring 1502 has an NZ-DSF fiber. It can be sent without compensation. In this case, all LTWs in spectrum M are added to the LTWs in spectrum N + 1 at node 1504-N + 1, and all STWs in spectrum M become STWs in spectrum N + 1 at node 1504-N + 1. To be added. The STW and LTW from the second ring 1506 can be regenerated using wavelength conversion, such as by preplanning O-E-O conversion, wavelength shifters, or specific wavelength assignments for the first ring 1502 and the second ring 1506. Assigned. For example, node 1504-N + 2 may receive wavelength assignment information from a network controller (see FIG. 17) that tracks or controls wavelength assignment at each node 1504, and which wavelength in spectrum M is an LTW or STW. You can decide if there is. After node 1504-N + 1, the LTW group and the STW group are assigned as shown in spectrum N + 1 of FIG. 15, each having 6 LTWs and 6 STWs grouped together. .

  Referring to FIG. 16, a flowchart of selected elements of one embodiment of a selective XPM compensation method 1600 as described herein is shown. In various embodiments, the method 1600 may be performed by the ROADM node 1100 or 1200 in the optical network, for example using the XPM compensation unit 1101. It should be noted that the particular operations described in method 1600 may be optional or rearranged in different embodiments.

  The method 1600 may begin at step 1602 by receiving route information for an optical path provisioned across the optical network. The path information specifies the common start point node and the first ROADM node included in the optical path. Each of the first ROADM nodes includes a first XPM compensation unit. At step 1604, the at least one transmitter is configured to assign wavelengths that are transmitted across the optical path and received at each of the first ROADM nodes at the common source node. The wavelengths assigned by the transmitter include short-traveling wavelengths (STW) in the first group and long-traveling wavelengths (LTW) in the second group. Here, the first group and the second group are spectrally separated from each other in the optical signal. At step 1606, the first ROADM node is configured to perform XPM compensation of the LTW in the second group using the first XPM compensation unit. In step 1608, the first ROADM node is configured to pass the STW in the first group to the output optical signal without XPM compensation.

  Referring to FIG. 17, a block diagram of selected elements of one embodiment of a network controller 1700 that implements a control plane function in an optical network, such as in the optical transport network 101 (see FIG. 1) is shown. Further, the network controller 1700 may function as or further include a software-defined networking (SDN) controller. The control plane may have functions for network intelligence and control, and supports the ability to establish network services including applications or modules for discovery, routing, route calculation, and signaling as described in more detail. You may have an application to do. In particular, the network controller 1700 may represent at least a particular portion of a control system used to implement XPM and selective per-node XPM as disclosed herein. For example, the network controller 1700 may send appropriate commands to the transmitter 102, the receiver 112, and the ROADM node to perform selective per-node XPM and other operations disclosed herein.

  In FIG. 17, control plane applications executed by the network controller 1700 may work together to automatically establish services in the optical network. The discovery module 1712 may discover local links that connect neighbors. The routing module 1710 may broadcast local link information to the optical network nodes during the populating of the database 1704. When a request for service from the optical network is received, the route calculation engine 1702 may be invoked to calculate a network route using the database 1704. This network path may then be provided to the signaling module 1706 to establish the requested service.

  As illustrated in FIG. 17, the network control unit 1700 includes a processor 1708 and a storage medium 1720. The storage medium 1720 may store executable instructions (ie, executable code) that can be executed by the processor 1708 having access to the storage medium 1720. The processor 1708 may execute instructions that cause the network controller 1700 to perform the functions and operations described herein. For the purposes of this disclosure, storage medium 1720 may include non-transitory computer readable media that stores data and instructions for at least a period of time. Storage media 1720 may include permanent and volatile media, fixed and removable media, magnetic and semiconductor media. The storage medium 1720 includes a direct access storage device (for example, a hard disk drive or a floppy disk), a sequential access storage device (for example, a tape disk drive), a CD (compact disk), a RAM (random access memory), and a ROM (read-only memory). CD-ROM, DVD (digital versatile disc), EEPROM (electrically erasable programmable read-only memory), and storage media such as flash memory, non-transitory media, or various combinations thereof, It is not limited to these. Storage medium 1720 operates to store instructions, data, or both. A storage medium 1720 as shown has a set or sequence of instructions that may represent an executable computer program: path computation engine 1702, signaling module 1706, discovery module 1712, and routing module 1710.

  As shown, the network control unit 1700 of FIG. Network interface 1714 may be any suitable system, device, or apparatus that operates to function as an interface between processor 1708 and network 1730. The network interface 1714 may allow the network controller 1700 to communicate via the network 1730 using an appropriate transmission protocol or standard. In some embodiments, network interface 1714 may be communicatively coupled to network storage resources via network 1730. In some embodiments, the network 1730 represents at least a particular portion of the optical transport network 101. The network 1730 may include a specific portion of the network that uses galvanic or electronic media. In particular embodiments, the network 1730 may include at least a particular portion of a public network such as the Internet. Network 1730 may be implemented using hardware, software, or various combinations thereof.

  In certain embodiments, the network controller 1700 may be configured to interact with a person (user) and receive data regarding the optical signal transmission path. For example, the network control unit 1700 includes or is coupled to one or more input devices and output devices to realize reception of data regarding an optical signal transmission path from the user and to output a result to the user. May be good. One or more input or output devices (not shown) may include, but are not limited to, a keyboard, mouse, touch pad, microphone, display, touch screen display, audio speaker, and the like. Alternatively or additionally, the network controller 1700 may be configured to receive data related to the optical signal transmission path from another computing device or a device such as a network node via the network 1730, for example.

  As shown in FIG. 17, in some embodiments, discovery module 1712 may be configured to receive data regarding optical signal transmission paths in an optical network and is responsible for discovery of neighbors and links between neighbors. good. In other words, the discovery module 1712 may transmit a discovery message according to a discovery protocol and may receive data regarding the optical signal transmission path. In some embodiments, the discovery module 1712 includes, among other things, fiber type, fiber length, number and type of components, data rate, data modulation format, optical signal input power, number of signal carrier wavelengths (ie, channels), among others. Features such as, but not limited to, channel spacing, traffic requirements, and network topology.

  As shown in FIG. 17, the routing module 1710 may be responsible for propagating link connectivity information to various nodes in an optical network such as the optical transport network 101. In certain embodiments, the routing module 1710 may populate the database 1704 with resource information to support traffic engineering, which may include link bandwidth availability. Thus, the database 1704 may be populated by the routing module 1710 with information useful for determining the network topology of the optical network.

  The route calculation engine 1702 may be configured to use information provided to the database 1704 by the routing module 1710 to determine the transmission characteristics of the optical signal transmission path, including the optical path length. The transmission characteristics of the optical signal transmission path include chromatic dispersion (CD), nonlinear (NL) effect, polarization mode dispersion (PMD), and polarization dependent loss (PDL). Such polarization effects as well as insight into how transmission degradation factors such as amplified spontaneous emission (ASE) can affect the optical signal in the optical signal transmission path may be provided. To determine the transmission characteristics of the optical signal transmission path, the path calculation engine 1702 may consider the interaction between transmission degradation factors. In various embodiments, the route calculation engine 1702 may generate values for specific transmission degradation factors. The route calculation engine 1702 may further store data describing the optical signal transmission route in the database 1704.

  In FIG. 17, the signaling module 1706 may provide functions related to setting, changing, and tearing down end-to-end network services in an optical network such as the optical transport network 101. For example, when an ingress node in an optical network receives a service request, the network controller 1700 uses the signaling module 1706 from the path computation engine 1702 that can be optimized according to different criteria such as bandwidth, cost, etc. You may request a network route. Once the desired network path is identified, the signaling module 1706 may then communicate with individual nodes along the network path to establish the requested network service. In different embodiments, the signaling module 1706 may use a signaling protocol to propagate subsequent communications to and from the node along the network path.

  In operation, the network controller 1700 module may implement various aspects of network management with selective per-node XPM compensation as disclosed herein.

  As disclosed herein, a method and apparatus for selective and node-by-node XPM compensation is based on a transmission distance over a respective optical path of wavelengths based on a short range propagation wavelength (STW) and a long range propagation. The wavelength may be divided into (LTW). Among other functions in the ROADM node, XPM compensation in the ROADM node may be selectively performed on the LTW. On the other hand, the STW may be passed without XPM compensation.

  The above disclosed subject matter is to be considered illustrative and not restrictive. Also, the appended claims are intended to cover all modifications, extensions and other embodiments that fall within the true spirit and scope of this disclosure. Thus, to the maximum extent permitted by law, the scope of the present disclosure should be determined by the broadest acceptable interpretation of the claims and their equivalents, and is limited or limited by the foregoing detailed description. Should not.

In addition to the above embodiment, the following additional notes are disclosed.
(Supplementary note 1) Reconfigurable optical add / drop multiplexer (ROADM) for selective per-node cross phase modulation (XPM) compensation, wherein the ROADM is:
A first optical splitter capable of receiving an optical signal including a short-range propagation wavelength (STW) in a first group and a long-distance propagation wavelength (LTW) in a second group, wherein the first group and the second group A group of first optical splitters spectrally separated from each other in the optical signal;
A wavelength selective switch (WSS) capable of receiving the optical signal from the first optical splitter, wherein the WSS is capable of passing the STW to the first group in an output optical signal;
A second optical splitter capable of receiving the optical signal from the first optical splitter;
A first cross phase modulation (XPM) compensation unit capable of receiving the STW and the LTW from the second optical splitter, wherein the LTW is XPM compensated by the first XPM compensation unit and output as an XPM compensation LTW; The STW is terminated in the first XPM compensation unit, the first XPM compensation unit;
ROADM with
(Supplementary Note 2) A first drop port in the second optical splitter capable of dropping at least one of the STWs without XPM compensation, wherein the WSS is dropped at the first drop port. A first drop port capable of terminating the STW;
The ROADM according to Appendix 1, further comprising:
(Supplementary Note 3) A third optical splitter capable of receiving the XPM compensation LTW from the first XPM compensation unit and transmitting the XPM compensation LTW to the WSS, wherein the WSS is the second optical signal in the output optical signal. A third optical splitter capable of switching the XPM compensation LTW to a group;
A second drop port in the third optical splitter capable of dropping at least one of the XPM compensated LTW, wherein the WSS can terminate the XPM compensated LTW dropped in the second drop port; A second drop port;
The ROADM according to Appendix 1, further comprising:
(Supplementary Note 4) A first add port in the WSS capable of adding at least one new STW to the first group in the output optical signal,
The ROADM according to Appendix 1, further comprising:
(Supplementary Note 5) A second cross phase modulation (XPM) compensation unit having a second add port and an output to the WSS, wherein the second XPM compensation unit includes at least one new LTW in the output optical signal. A second XPM compensation unit capable of being added to the second group of and capable of XPM compensating the new LTW;
The ROADM according to supplementary note 4, further comprising:
(Appendix 6) A wavelength conversion unit capable of shifting the wavelength of at least one of the new LTW and the new STW,
The ROADM according to Appendix 5, further comprising:
(Supplementary note 7) An optical system for selective per-node cross phase modulation (XPM) compensation, the optical system comprising:
An optical network having a plurality of nodes, wherein at least some of said nodes have reconfigurable optical add / drop multiplexer (ROADM) nodes comprising a first cross phase modulation (XPM) compensation unit When,
A network control unit comprising a processor and a storage medium accessible to the processor;
The storage medium has
Receiving path information of an optical path provisioned across the optical network, the path information specifying a common origin node and a first ROADM node included in the optical path, and each of the first ROADM nodes is configured to receive the first XPM Each including a compensation unit,
Configuring at least one transmitter at the common source node to allocate wavelengths transmitted over the optical path and received at each of the first ROADM nodes, wherein the wavelengths allocated by the transmitter are Having a short-range propagation wavelength (STW) in one group and a long-range propagation wavelength (LTW) in a second group, wherein the first group and the second group are spectrally related to each other in an optical signal. Away
Configuring the first ROADM node to perform XPM compensation of the LTW in the second group using the first XPM compensation unit;
An optical system for storing instructions executable by the processor for the purpose.
(Supplementary note 8)
Configuring the first ROADM node to pass at least one of the STWs in the first group to an output optical signal without XPM compensation;
The optical system of claim 7 further comprising instructions for.
(Supplementary Note 9) A second ROADM node selected from at least some of the first ROADM nodes includes a second XPM compensation unit having a first add port that receives at least one new LTW added to the optical signal. And further comprising:
Configuring the second ROADM node to XPM compensate the new LTW received at the first add port using the second XPM compensation unit;
The optical system of claim 7 further comprising instructions for.
(Supplementary Note 10) At least some of the second ROADM nodes have a second add port that can receive at least one new STW added to the optical signal, and the instructions are:
Configuring the second ROADM node to add the new STW from the second add port to the first group in the output optical signal without XPM compensation of the new STW;
The optical system of claim 9, further comprising instructions for:
(Supplementary note 11) The optical system according to supplementary note 10, wherein at least some of the first ROADM nodes include a wavelength conversion unit capable of shifting a wavelength of at least one of the new LTW and the new STW.
(Supplementary note 12) The optical system according to supplementary note 7, wherein at least some of the first ROADM nodes have a first drop port capable of dropping at least one of the STWs without XPM compensation.
(Supplementary note 13) The optical system according to supplementary note 12, wherein at least some of the first ROADM nodes have a second drop port capable of dropping at least one of the XPM compensated LTWs.
(Supplementary note 14) A method for cross-phase modulation (XPM) compensation per selective node of an optical signal, the method comprising:
Receiving path information of an optical path provisioned over an optical network, the path information including a common source node and a first reconfigurable optical add / drop multiplexer (ROADM) node included in the optical path; Each of the first ROADM nodes includes a first XPM compensation unit, respectively,
Configuring at least one transmitter at the common source node to assign wavelengths transmitted over the optical path and received at each of the first ROADM nodes, the assigned by the transmitter The wavelength includes a short-range propagation wavelength (STW) in the first group and a long-range propagation wavelength (LTW) in the second group, and the first group and the second group are included in the optical signal. Steps that are spectrally separated from each other;
Configuring the first ROADM node to perform XPM compensation of the LTW in the second group using the first XPM compensation unit;
Having a method.
(Supplementary Note 15) Configuring the first ROADM node to pass the STW in the first group to an output optical signal without XPM compensation;
The method according to appendix 14, further comprising:
(Supplementary Note 16) A second ROADM node selected from at least some of the first ROADM nodes includes a second XPM compensation unit having a first add port that receives at least one new LTW added to the optical signal. In addition,
Configuring the second ROADM node to XPM compensate the new LTW received at the first add port using the second XPM compensation unit;
The method according to appendix 14, further comprising:
(Supplementary note 17) At least some of the second ROADM nodes have a second add port that can receive at least one new STW added to the optical signal,
Configuring the second ROADM node to add the new STW from the second add port to the first group in the output optical signal without XPM compensation of the new STW;
The method according to supplementary note 16, further comprising:
(Supplementary note 18) Shifting at least one wavelength of the new LTW and the new STW using wavelength conversion units included in at least some of the first ROADM nodes;
The method according to appendix 17, further comprising:
(Supplementary note 19) Dropping at least one of the STWs without XPM compensation from the optical signal using a first drop port included in at least some of the first ROADM nodes;
The method according to appendix 14, further comprising:
(Supplementary note 20) Dropping at least one of the XPM compensation LTWs using a second drop port included in at least some of the first ROADM nodes;
The method according to appendix 19, further comprising:

1100 ROADM with selective XPM compensation
1101 XPM compensation unit 1102 Optical signal 1104, 1108, 1110 Splitter 1106 WSS
1112 Output optical signal 1114 Input stage 1116, 1118 Drop port

Claims (20)

A reconfigurable optical add / drop multiplexer (ROADM) for selective per-node cross phase modulation (XPM) compensation, wherein the ROADM is
A first optical splitter capable of receiving an optical signal including a short-range propagation wavelength (STW) in a first group and a long-distance propagation wavelength (LTW) in a second group, wherein the first group and the second group A group of first optical splitters spectrally separated from each other in the optical signal;
A wavelength selective switch (WSS) capable of receiving the optical signal from the first optical splitter, wherein the WSS is capable of passing the STW to the first group in an output optical signal;
A second optical splitter capable of receiving the optical signal from the first optical splitter;
A first cross phase modulation (XPM) compensation unit capable of receiving the STW and the LTW from the second optical splitter, wherein the LTW is XPM compensated by the first XPM compensation unit and output as an XPM compensation LTW; The STW is terminated in the first XPM compensation unit, the first XPM compensation unit;
ROADM with A first drop port in the second optical splitter capable of dropping at least one of the STWs without XPM compensation, wherein the WSS can terminate the STW dropped at the first drop port The first drop port,
The ROADM according to claim 1, further comprising: A third optical splitter capable of receiving the XPM compensation LTW from the first XPM compensation unit and transmitting the XPM compensation LTW to the WSS, wherein the WSS passes the second group in the output optical signal to the second group; A third optical splitter capable of switching the XPM compensation LTW;
A second drop port in the third optical splitter capable of dropping at least one of the XPM compensated LTW, wherein the WSS can terminate the XPM compensated LTW dropped in the second drop port; A second drop port;
The ROADM according to claim 1, further comprising: A first add port in the WSS capable of adding at least one new STW to the first group in the output optical signal;
The ROADM according to claim 1, further comprising: A second cross phase modulation (XPM) compensation unit having a second add port and an output to the WSS, wherein the second XPM compensation unit converts at least one new LTW into the second optical signal in the output optical signal. A second XPM compensation unit that can be added to the group and XPM compensated for the new LTW;
The ROADM according to claim 4, further comprising: A wavelength conversion unit capable of shifting the wavelength of at least one of the new LTW and the new STW;
The ROADM according to claim 5, further comprising: An optical system for selective per-node cross phase modulation (XPM) compensation, the optical system comprising:
An optical network having a plurality of nodes, wherein at least some of said nodes have reconfigurable optical add / drop multiplexer (ROADM) nodes comprising a first cross phase modulation (XPM) compensation unit When,
A network control unit comprising a processor and a storage medium accessible to the processor;
The storage medium has
Receiving path information of an optical path provisioned across the optical network, the path information specifying a common origin node and a first ROADM node included in the optical path, and each of the first ROADM nodes is configured to receive the first XPM Each including a compensation unit,
Configuring at least one transmitter at the common source node to allocate wavelengths transmitted over the optical path and received at each of the first ROADM nodes, wherein the wavelengths allocated by the transmitter are Having a short-range propagation wavelength (STW) in one group and a long-range propagation wavelength (LTW) in a second group, wherein the first group and the second group are spectrally related to each other in an optical signal. Away
Configuring the first ROADM node to perform XPM compensation of the LTW in the second group using the first XPM compensation unit;
An optical system for storing instructions executable by the processor for the purpose. The instructions are
Configuring the first ROADM node to pass at least one of the STWs in the first group to an output optical signal without XPM compensation;
The optical system of claim 7, further comprising instructions for: A second ROADM node selected from at least some of the first ROADM nodes further comprises a second XPM compensation unit having a first add port that receives at least one new LTW added to the optical signal; The instructions are
Configuring the second ROADM node to XPM compensate the new LTW received at the first add port using the second XPM compensation unit;
The optical system of claim 7, further comprising instructions for: At least some of the second ROADM nodes have a second add port that can receive at least one new STW that is added to the optical signal, and the instructions include:
Configuring the second ROADM node to add the new STW from the second add port to the first group in the output optical signal without XPM compensation of the new STW;
The optical system of claim 9, further comprising instructions for:   The optical system according to claim 10, wherein at least some of the first ROADM nodes have a wavelength conversion unit capable of shifting a wavelength of at least one of the new LTW and the new STW.   8. The optical system of claim 7, wherein at least some of the first ROADM nodes have a first drop port that can drop at least one of the STWs without XPM compensation.   13. The optical system of claim 12, wherein at least some of the first ROADM nodes have a second drop port that can drop at least one of the XPM compensated LTWs. A method for selective per-node cross phase modulation (XPM) compensation of an optical signal, the method comprising:
Receiving path information of an optical path provisioned over an optical network, the path information including a common source node and a first reconfigurable optical add / drop multiplexer (ROADM) node included in the optical path; Each of the first ROADM nodes includes a first XPM compensation unit, respectively,
Configuring at least one transmitter at the common source node to assign wavelengths transmitted over the optical path and received at each of the first ROADM nodes, the assigned by the transmitter The wavelength includes a short-range propagation wavelength (STW) in the first group and a long-range propagation wavelength (LTW) in the second group, and the first group and the second group are included in the optical signal. Steps that are spectrally separated from each other;
Configuring the first ROADM node to perform XPM compensation of the LTW in the second group using the first XPM compensation unit;
Having a method. Configuring the first ROADM node to pass the STW in the first group to an output optical signal without XPM compensation;
15. The method of claim 14, further comprising: A second ROADM node selected from at least some of the first ROADM nodes further comprises a second XPM compensation unit having a first add port that receives at least one new LTW added to the optical signal;
Configuring the second ROADM node to XPM compensate the new LTW received at the first add port using the second XPM compensation unit;
15. The method of claim 14, further comprising: At least some of the second ROADM nodes have a second add port capable of receiving at least one new STW added to the optical signal;
Configuring the second ROADM node to add the new STW from the second add port to the first group in the output optical signal without XPM compensation of the new STW;
The method of claim 16 further comprising: Shifting at least one wavelength of the new LTW and the new STW using wavelength conversion units included in at least some of the first ROADM nodes;
18. The method of claim 17, further comprising: Dropping at least one of the STWs without XPM compensation from the optical signal using a first drop port included in at least some of the first ROADM nodes;
15. The method of claim 14, further comprising: Dropping at least one of the XPM compensated LTWs using a second drop port included in at least some of the first ROADM nodes;
20. The method of claim 19, further comprising:

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