WO2022053133A1 - Réflectométrie optique en domaine temporel désagrégée accordée en lambda - Google Patents

Réflectométrie optique en domaine temporel désagrégée accordée en lambda Download PDF

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Publication number
WO2022053133A1
WO2022053133A1 PCT/EP2020/075226 EP2020075226W WO2022053133A1 WO 2022053133 A1 WO2022053133 A1 WO 2022053133A1 EP 2020075226 W EP2020075226 W EP 2020075226W WO 2022053133 A1 WO2022053133 A1 WO 2022053133A1
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Prior art keywords
optical
wavelengths
measurement
wavelength
wdm system
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PCT/EP2020/075226
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English (en)
Inventor
Roberto Magri
Alberto Deho
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Telefonaktiebolaget Lm Ericsson (Publ)
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Priority to PCT/EP2020/075226 priority Critical patent/WO2022053133A1/fr
Publication of WO2022053133A1 publication Critical patent/WO2022053133A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/40—Transceivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0279—WDM point-to-point architectures

Definitions

  • Optical time domain reflectometry is a powerful technique to precisely find the fault location of an optical fiber. OTDR is based on sending pulses into the optical fiber and measuring the reflected optical power from the fault. By measuring the roundtrip delay, it is possible to calculate the distance of the fault.
  • OTDR can be exploited for latency measurements in the optical fiber.
  • 3GPP 3 rd Generation Partnership Project
  • 5G also referred to as New Radio (NR)
  • RAN New Radio
  • Digitally Coded OTDR instead of a single pulse, a train of pulses according to a coded digital sequence are transmitted. This approach breaks the usual dynamic-range vs. accuracy trade off of conventional OTDR.
  • modified transceivers e.g., small form-factor pluggable (SFP)
  • SFP small form-factor pluggable
  • the transmitter may be used for both the data and the OTDR.
  • both of these types of transceivers are single fiber devices that cannot operate safely under reflections since they use a splitter to receive the optical signal from the optical line.
  • typical single fiber systems use different wavelengths for upstream and downstream direction to avoid reflections.
  • this is not possible since the receiver path is not selective to allow the reception of the OTDR signal.
  • This limitation strongly limits the performance of the device which depends on the Optical return Loss of the line fiber.
  • both of these transceivers need proprietary modifications which increase the complexity and cost as the modifications would be vendor specific.
  • Some embodiments advantageously provide a method and system for measurement configurations and functions in single fiber WDM systems.
  • an OTDR system implementation is provided where the OTDR system has a functional split that allows for re-use of Of-the-Shelf optical transceivers while keeping high accuracy and reflection immunity in single fiber operation and WDM per wavelength OTDR capability.
  • the implementation is based on three functional blocks: host device functions, optical transceiver functions and passive routing device functions.
  • a host device includes pluggable transceiver ports configured to: provide the OTDR coded digital signal generation, receive OTDR signal Analog-to-digital conversion and decode the signal.
  • the optical transceivers may be “off-the-shelf’ tunable linear pluggable transceivers with no modifications (i.e., with no OTDR processing) which operate in data transceiver mode or OTDR mode based on host device 12 commands and/or signaling.
  • the optical transceiver may include bare minimum functionality such as being wavelength tunable and being able to transmit/receive digital signals as the OTDR signal is a digital signal similar to a data traffic signal, and the receiver is linear where the digital reception and processing is specifically delegated and/or provided by the host device.
  • the passive routing device is configured to route the data signal and OTDR signal based in part due to the optical transceiver’s wavelength tunability.
  • the transceiver change to OTDR mode may be provided, in part, by tuning to the upstream wavelength (i.e., wavelength that is reserved for transmission in the opposite direction) and the passive block of the passive routing device routes the reflections toward the receiver of the optical transceiver.
  • the upstream wavelength i.e., wavelength that is reserved for transmission in the opposite direction
  • a wave division multiplexing, WDM, system includes an optical multiplexer configured to multiplex a plurality of measurement wavelengths and a plurality of transmission wavelengths onto a single fiber, an optical demultiplexer configured to demultiplex a plurality of reception wavelengths received from the single fiber where the plurality of measurement wavelengths overlap with the reception wavelengths, and a first optical transceiver in optical communication with the optical multiplexer and optical demultiplexer.
  • the first optical transceiver is configured to: transmit a measurement signal at a first wavelength of the plurality of measurement wavelengths to the optical multiplexer, and receive a reflected version of the measurement signal at the first wavelength from the optical demultiplexer.
  • the WDM system includes an interface for enabling communication between a host device and the first optical transceiver where the host device includes a processing circuitry configured to control transmission of the measurement signal and determine a measurement characteristic associated with the reflected version of the measurement signal.
  • the first optical transceiver is configured to be tuned from one of the plurality of transmission wavelengths to the first wavelength of the plurality of measurement wavelengths.
  • the WDM system further includes a plurality of optical transceivers including the first optical transceiver where the plurality of optical transceivers are configured to transmit data traffic using the plurality of transmission wavelengths.
  • at least one of the optical transceivers is configured to continue transmitting data traffic while the first optical transceiver is transmitting the measurement signal.
  • the reflected version of the signal at the first wavelength is configured to travel at least a portion of the single fiber.
  • the WDM system includes an optical circulator in optical communication with the optical multiplexer and optical demultiplexer where the optical circulator is configured to: route the plurality of transmission wavelengths and the plurality of measurement wavelengths to the single fiber, and route the plurality of reception wavelengths to the optical demultiplexer.
  • the measurement signal is a digital signal based on an OTDR sequence.
  • the measurement characteristic is at least one of a time and space characteristic of the single fiber with respect to the first wavelength.
  • the at least one of the time and space characteristic includes one of a latency characteristic, length characteristic and a OTDR characteristic.
  • the optical demultiplexer is configured with greater wavelength spacing than a wavelength spacing of the optical multiplexer.
  • optical demultiplexer is configured with lOOGhz wavelength spacing and the optical multiplexer is configured with 200Ghz wavelength spacing. According to one or more embodiments, the optical demultiplexer and the optical multiplexer are configured with equal wavelength spacing. According to one or more embodiments, the wavelength spacing is lOOGhz.
  • the WDM system includes an optical multiplexer (34) configured to multiplex a plurality of measurement wavelengths and a plurality of transmission wavelengths onto a single fiber (18), an optical demultiplexer (36) configured to demultiplex a plurality of reception wavelengths received from the single fiber where the plurality of measurement wavelengths overlap with the reception wavelengths.
  • the WDM system further includes a first optical transceiver in optical communication with the optical multiplexer (34) and optical demultiplexer (36), and an interface for enabling communication between a host device (12) and the first optical transceiver where the interface configured to control transmission of the measurement signal.
  • Transmission, at the first optical transceiver, of a measurement signal at a first wavelength of the plurality of measurement wavelengths is caused to the optical multiplexer.
  • a reflected version of the measurement signal at the first wavelength is received at the first optical transceiver from the optical demultiplexer.
  • a measurement characteristic associated with the reflected version of the measurement signal is determined at the host device.
  • the first optical transceiver is tuned from one of the plurality of transmission wavelengths to the first wavelength of the plurality of measurement wavelengths.
  • the WDM system includes a plurality of optical transceivers including the first optical transceiver. Transmission is caused of data traffic using the plurality of transmission wavelengths. According to one or more embodiments, transmission is caused of data traffic using at least one of the optical transceivers while the first optical transceiver is transmitting the measurement signal.
  • the reflected version of the signal at the first wavelength is configured to travel at least a portion of the single fiber.
  • the WDM system further includes an optical circulator in optical communication with the optical multiplexer and optical demultiplexer.
  • the plurality of transmission wavelengths and the plurality of measurement wavelengths are routed at the optical circulator to the single fiber.
  • the plurality of reception wavelengths are routed at the optical circulator to the optical demultiplexer.
  • the measurement signal is a digital signal based on an OTDR sequence.
  • the measurement characteristic is at least one of a time and space characteristic of the single fiber with respect to the first wavelength.
  • the at least one of the time and space characteristic includes one of a latency characteristic, length characteristic and a OTDR characteristic.
  • the optical demultiplexer is configured with greater wavelength spacing than a wavelength spacing of the optical multiplexer.
  • optical demultiplexer is configured with lOOGhz wavelength spacing and the optical multiplexer is configured with 200Ghz wavelength spacing. According to one or more embodiments, the optical demultiplexer and the optical multiplexer are configured with equal wavelength spacing. According to one or more embodiments, the wavelength spacing is lOOGhz.
  • FIG. 1 is a schematic diagram of an example WDM architecture illustrating a WDM system according to the principles of the disclosure
  • FIG. 2 is a flow diagram illustrating an example process according to one or more embodiments of the disclosure
  • FIG. 3 is a block diagram of an example system with an example passive routing device according to one or more embodiments of the disclosure
  • FIG. 4 is a block diagram of the WDM system in data transmission mode according to one or more embodiments of the disclosure.
  • FIG. 5 is a block diagram of the WDM system in measurement/OTDR mode according to one or more embodiments of the disclosure
  • FIG. 6 is block diagram of a digital OTDR scheme according to one or more embodiments of the disclosure.
  • FIG. 7 is a block diagram of a common ADC according to one or more embodiments of the disclosure.
  • FIG. 8 is a block diagram of dedicated ADCs according to one or more embodiments of the disclosure.
  • FIG. 9 is a block diagram of another example of a WDM system according to one or more embodiments of the disclosure. DETAILED DESCRIPTION
  • relational terms such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.
  • the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein.
  • the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
  • the joining term, “in communication with” and the like may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example.
  • electrical or data communication may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example.
  • the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or wireless connections such as optical connections.
  • the term “network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi -standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node,
  • MME mobile
  • functions described herein as being performed by a WDM system may be distributed over a various entities/devices.
  • the functions of the WDM system described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.
  • Some embodiments provide measurement configurations and functions in single fiber WDM systems.
  • FIG. 1 a schematic diagram of a WDM system 10, according to an embodiment, may support telecommunications such as 3GPP-type cellular network via backhaul communications.
  • WDM system 10 may include host device 12 in communication (e.g., electrical communication) with multiple optical transceivers 14a-14n (collectively referred to as optical transceiver 14) and a passive routing device 16 that is in optical communication with the optical transceiver 14 and single fiber 18. While not shown in FIG. 1, single fiber 18 may be in communication with another WDM system 10 such that single fiber 18 provides bidirectional communication between two WDM systems 10.
  • host device includes hardware 20 enabling it to communicate with the optical transceiver 14, among other entities in WDM system 10, and process signals from the optical transceiver 14, as described herein.
  • the hardware 20 may include an interface 22 for enabling communicating between host device 12 and optical transceiver 14.
  • the hardware 20 of the host device 12 further includes processing circuitry 24.
  • the processing circuitry 24 may include a processor 26 and a memory 28.
  • the processing circuitry 24 may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions.
  • Processing circuitry 24 may include and/or provide analog-to-digital converter module(s)/functions, digital signal processing module(s)/functions, logic module(s)/functions, clock data recovery module(s)/functions as described herein.
  • the processor 26 may be configured to access (e.g., write to and/or read from) the memory 28, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).
  • the memory 28 may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory).
  • the host device 12 further has software 30 stored internally in, for example, memory 28, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the host device 12 via an external connection.
  • the software 30 may be executable by the processing circuitry 24.
  • the processing circuitry 24 may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by host device 12.
  • Processor 26 corresponds to one or more processors 26 for performing host device 12 functions described herein.
  • the memory 28 is configured to store data, programmatic software code and/or other information described herein.
  • the software 30 may include instructions that, when executed by the processor 26 and/or processing circuitry 24, causes the processor 26 and/or processing circuitry 24 to perform the processes described herein with respect to host device 12.
  • processing circuitry 24 of the host device 12 may include measurement unit 32 configured to perform one or more host device 12 functions as described herein such as with respect to measurement configurations and functions in single fiber WDM systems.
  • system 10 is an OTDR system operating in split architecture where the host device 12 is performing OTDR functionality as well as data communication functionality such that WDM system 10 provides a lambda (X) tuned disaggregated OTDR system. Therefore, system 10 is able to provide OTDR functionality “on demand” via the interface 22 of host device 12 where a single host device 12 may provide OTDR service to one or more nodes, i.e., OTDR may be shared among a plurality of nodes.
  • Optical transceiver 14 is configured to convert an electrical signal such as a data signal to an optical signal for transmission, and is also configured to convert a received optical signal to an electrical signal such as a linear electrical photo-detected signal.
  • optical transceiver 14 is a “dummy” and/or “off-the-shelf’ optical transceiver with no modifications that is configured to convert an electrical signal to an optical signal and vice versa where digital processing of the electrical signal is not performed by the optical transceiver 14, i.e., the digital processing of the electrical signal is performed by the host device 12.
  • optical transceiver 14 is a tunable linear transceiver 14 that may be removably pluggable to passive routing device 16 and/or host device 12.
  • each optical transceiver 14a-14n is configured to operate at a respective wavelength for data transmission (i.e., respective transmission wavelength) where one or more optical transceivers 14a-14n may be configured to be tunable to a different wavelength (i.e., respective measurement wavelength) for measurement signaling, as described herein.
  • WDM system 10 includes a passive routing device 16 that is configured to route wavelengths to and from optical transceivers 14.
  • the passive routing device 16 is configured to multiplex a predefined wavelength received from each optical transceivers 14a-14n to single fiber 18, and is also configured to demultiplex predefined wavelengths form single fiber 18 to individual optical transceivers 14, as described herein.
  • passive routing device 16 includes two arrayed waveguides and a circulator, as described herein, although other optical components that perform the specific functions of passive routing device 16 described herein may be used.
  • Single fiber 18 may be a single optical fiber that is configured to carry one or more wavelengths such as one or more multiplexed signals. In one or more embodiments, more than one single fiber 18 may be used such that the additional single fiber 18 may be a backup fiber that may be measured as described herein and/or may be configured to carry a portion of wavelengths such that the two or more single fibers 18 are configured to carry respective wavelengths.
  • FIG. 2 is a flowchart of an example process in a host device 12 for according to the principles of the disclosure.
  • the WDM system 10 includes an optical multiplexer 34 configured to multiplex a plurality of measurement wavelengths and a plurality of transmission wavelengths onto a single fiber 18, an optical demultiplexer 36 configured to demultiplex a plurality of reception wavelengths received from the single fiber 18 where the plurality of measurement wavelengths overlap with the reception wavelengths, and a first optical transceiver 14 in optical communication with the optical multiplexer 34 and optical demultiplexer 36.
  • the first optical transceiver 14 is configured to: transmit a measurement signal at a first wavelength of the plurality of measurement wavelengths to the optical multiplexer 34 and receive a reflected version of the measurement signal at the first wavelength from the optical demultiplexer.
  • the WDM system includes an interface 22 for enabling communication between a host device 12 and the first optical transceiver 14.
  • One or more Blocks and/or functions performed by host device 12 may be performed by one or more elements of host device 12 such as by measurement unit 32 in processing circuitry 24, processor 26, interface 22, etc.
  • Processing circuitry 24 is configured to control transmission of the measurement signal and determine a measurement characteristic associated with the reflected version of the measurement signal, as described herein (Block S100).
  • the first optical transceiver 14 is configured to be tuned from one of the plurality of transmission wavelengths to the first wavelength of the plurality of measurement wavelengths.
  • the WDM system 10 includes a plurality of optical transceivers 14 including the first optical transceiver where the plurality of optical transceivers 14 are configured to transmit data traffic using the plurality of transmission wavelengths.
  • the WDM system 10 includes an optical circulator 38 in optical communication with the optical multiplexer and optical demultiplexer where the optical circulator 38 configured to: route the plurality of transmission wavelengths and the plurality of measurement wavelengths to the single fiber 18, and route the plurality of reception wavelengths to the optical demultiplexer 36.
  • the measurement signal is a digital signal based on an OTDR sequence.
  • the measurement characteristic is at least one of a time and space characteristic of the single fiber 18 with respect to the first wavelength.
  • the at least one of the time and space characteristic includes one of a latency characteristic, length characteristic and a OTDR characteristic.
  • the optical demultiplexer 36 is configured with greater wavelength spacing than a wavelength spacing of the optical multiplexer 34.
  • the optical demultiplexer 36 is configured with lOOGhz wavelength spacing and the optical multiplexer 34 is configured with 200Ghz wavelength spacing.
  • the optical demultiplexer 36 and the optical multiplexer 34 are configured with equal wavelength spacing.
  • the wavelength spacing is lOOGhz.
  • Some embodiments provide measurement configurations and functions in single fiber WDM systems.
  • the WDM system 10 architecture is a split architecture that provides perchannel OTDR function in a Single Fiber Working WDM system without using special proprietary optical transceivers with embedded OTDR function, thereby allowing the scheme described herein to work with off the shelf commercially available linear optical transceiver 14 (e.g., Linear SFP).
  • the OTDR functionality may be on demand OTDR functionality that is enabled, in part, by interface 22.
  • FIG. 3 is an example of the WDM system 10 that includes several subsystems.
  • WDM system 10 includes host device 12 (i.e., one subsystem) which houses the linear transceivers modules for transmitting/receiving signals to/from optical transceivers 14, performing the clock and data recovery (CDR) of the transmitted data and switches to OTDR mode when required by sending digitally coded sequences to optical transceivers 14 and processing the received samples.
  • CDR clock and data recovery
  • the processing of the received samples may be provided in non-real time by processing circuitry 24 and/or by another external entity.
  • Optical transceiver 14 i.e., another subsystem
  • a tunable linear transceiver may be a common off-the-shelf optical transceiver that sends to the single fiber 18 the client data and returns to the host device 12 the linear electrical signal photo-detected from the optical line from the demultiplexer.
  • one or more optical transceivers 14 may be dedicated measurement transceivers that are configured to only transmit measurement signals or non-data traffic signals.
  • the passive routing device 16 is a passive multiplexer (Mux)Zdemul tiplexer (Demux) subsystem where multiplexer 34 is configured with a 200Ghz grid that can filter the up-stream and down-stream wavelengths and demultiplexer 36 is configured with a lOOGhz grid that can filter-out the up-stream wavelengths and deliver the downstream wavelength to one or more optical transceivers 14.
  • the passive routing device 16 block is responsible for routing of the data and OTDR wavelength, as described in detail below. While mux 34 and demux 36 is illustrated as being arrayed waveguide (AWG), other optical components that are able to provide the passive routing device 16 functionality described herein are equally applicable.
  • multiplexer 34 may support channels 1-48 where each channel corresponds to a wavelength such as X1-X48.
  • the odd channels I, X3, etc. i.e., transmission wavelengths
  • the even channels X2, X4, etc. i.e., measurement wavelengths
  • the demultiplexer 36 may be configured with support the even channels X2, X4, etc., which depending on the transmission mode, may corresponds to measurement wavelength(s) and/or data traffic wavelengths.
  • X2 may correspond to a measurement wavelength transmitted by optical transceiver 14 while, in data/normal mode, X2 may correspond to a data traffic signal received from single fiber 18.
  • the optical circulator 38 is configured to pass incoming wavelengths from multiplexer 34 to single fiber 18 while passing incoming wavelengths from single fiber 18 to demultiplexer 36.
  • Another other optical component (s) that are configured to provide the optical circulator 38 functionality may be used instead of the optical circulator 38.
  • One or more embodiments relate to single-fiber (SFW) operation where different wavelengths are used in two propagation directions to avoid reflection- induced interference.
  • SFW single-fiber
  • alternate wavelengths are used upstream and downstream (e.g., channels 1, 3, 5... .47 downstream and 2, 4, 6, ...48 upstream where each channel is associated with a different wavelength). While the example operation is described with respect to single fiber operation, the teachings described herein are equally applicable to DFW with modification to the passive block as described below.
  • optical transceiver 14a When in “OTDR-mode” such as to verify one or more characteristics of the single fiber 18 such as due to a fiber break, optical transceiver 14a is tuned to the twin upstream even wavelength (e.g., 2) so that the OTDR coded bits reflected from the fiber are routed to optical transceiver 14a as if the upstream signal on 2 had original from another entity attached to the single fiber 18 such as host device 12 at the other end of single fiber 18.
  • the 200Ghz wide mux 34 filter enables such a configuration as data traffic is routed from optical transceivers 14 to single fiber 18 using a subset of available optical bandwidth of multiplexer 34, thereby allowing at least some of the remaining bandwidth to be used to route measurement wavelengths (e.g., 2) to single fiber 18 for measurements.
  • the Ghz quantity associated with the mux/ demux may refer to a channel spacing such as a channel spacing of 200Ghz.
  • demultiplexer 36 is 100GHz wide, the reflections of the data traffic wavelengths are avoided during normal operation.
  • data is sent downstream on the odd wavelength (i.e., transmission wavelength such as 2J in this example), coupled through multiplexer 34 to the single fiber 18.
  • the received upstream even wavelength e.g., X2
  • the circulator 38 filtered and sent to the optical transceiver 14 (i.e., optical transceiver 14a in this example).
  • the OTDR mode exploits digitally coded sequences (e.g., Goolay or Simplex sequences) so that standard data bits can be used as OTDR signals and no modifications are required to the optical transceiver 14.
  • digitally coded sequences e.g., Goolay or Simplex sequences
  • the configurations described herein advantageously allow for an OTDR signal to be transmitted in the form of digital bits, thereby enabling the use of standard optical transceiver (e.g., common dual fiber optical transceiver) as OTDR devices that provide the transmission/reception of the OTDR signal but not the processing as described herein.
  • the digital implementation of using digital bits provides high accuracy.
  • the coded sequences have the property that their autocorrelation is a Dirac’s Delta so that, at optical transceiver 14, the OTDR trace is acquired by calculating the cross-correlation between the transmitted sequence and the received signal out of the analog-to-digital converter described below, which is a low complexity process.
  • this operation/processing can be performed offline by the host device 12.
  • the OTDR traces i.e. , OTDR data
  • FIG. 6 is a block diagram of a digital OTDR scheme that is implemented by host device 12.
  • the achievable accuracy is good operating at few hundred Mb/s (e.g., 200 Mb/s for 1 -meter accuracy).
  • a higher rate is also possible since the optical transceivers 14 can operate at 10G or higher, but the higher the rate, the faster the ADC should be, so the option to have a high-speed ADC for each wavelength for both data and OTDR detection is possible.
  • a standard clock and data recovery (CDR) on at the host device 12 is used to detect the high-speed client data, and low speed ADC (e.g., 10 - 500Mhz) is used to detect the OTDR bits in order to optimize both receiver chains, which reduces cost.
  • the OTDR bits can be sent at lower speed by duplicating the bits at the same data rate used for data signaling.
  • FIGS. 7 and 8 Two example configurations for the host device 12 as shown in FIGS. 7 and 8.
  • a single ADC is shared among all optical transceivers 14.
  • a digital switch may be used to select which transceiver is connected to the ADC during OTDR mode (e.g., via FPGA implementation).
  • multiple CDRs 42a-42n are provided such as one for each optical transceiver 14 where a common ADC 40 is used.
  • Processing circuitry 24 may include logic and DSP 44 components for processing of signals.
  • OTDR can be sequentially applied to each wavelength such that real-time operation may not be required.
  • multiple ADCs 40a-40n are used where each channel is provided an ADC 40 such as to provide for simultaneous operation.
  • FIG. 9 is a block diagram of a DFW scenario according to the principles of the disclosure.
  • the configuration of FIG. 9 exploits a wider bandwidth AWG (e.g., with +/- 30 GHz bandwidth) and the wavelength tuning of the optical transceiver 14 from the data mode to OTDR mode is performed within this bandwidth.
  • the periodic filter 46 has a narrower passband in order to let pass the reflected OTDR wavelength (i.e., measurement wavelength) in OTDR-mode and to block the un-shifted wavelength (i.e., transmission wavelength) during normal operation to avoid overlapping of upstream signal and reflected downstream signal.
  • a splitter 48 is used to inject the signal from the circulator 38 into the input fiber to demultiplexer 36. This embodiment may avoid reducing the capacity of the WDM system 10 that may occur for 100GHz shifting used in the SFW case.
  • One or more embodiments described herein allow for a practical and commercially feasibly implementation of an integrated per-wavelength OTDR subsystem in a transport equipment.
  • the following use cases can be provided in accordance with the teachings described herein:
  • Each wavelength may be tested independently so fiber integrity can be assessed in various kind of topologies where different wavelengths may travel different paths, patch cord, etc.
  • PTP precision time protocol
  • the system may send a command to the remote equipment (i.e., equipment receiving on the other side or coupled to single fiber 18) in order to switch off the laser, thereby avoiding interference with the OTDR reflection.
  • This step may not be necessary in presence of a fiber fault for fault location as the laser transmission from the remote equipment is unlikely to a substantially affect the OTDR measurement.
  • a digital OTDR system with perchannel monitoring capability is provided where the digital OTDR system in WDM system 10 includes:
  • a host device 12 responsible for data and OTDR bit sequence generator and processing
  • the pluggable transceiver are tunable to an adjacent wavelength when in OTDR mode so that the passive block routes the reflected signal toward the optical transceiver 14.
  • one or more embodiments described herein provide a configuration in a WDM system 10 that provides OTDR functionality where one or more of the following advantages are provided: does not require transceiver modifications such that commercial off-the-shelf linear optical transceivers can be used, i.e., “dummy” optical transceivers; high accuracy: the WDM system implements digitally coded OTDR signals that allows for high accuracy; the WDM system configuration is compatible with single fiber operation where two different wavelengths are used, one wavelength for the upstream direction and another wavelength for the downstream direction; per-wavelength OTDR capability (DWDM scenario); and
  • the following use cases can be covered: o High accuracy fault location and fiber monitoring; and o Fiber latency asymmetry measurement for 5G class A synchronization.
  • the concepts described herein may be embodied as a method, data processing system, and/or computer program product. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.
  • These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.
  • the computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
  • the functions/acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
  • some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.
  • Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Java® or C++.
  • the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language.
  • the program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer.
  • the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).
  • LAN local area network
  • WAN wide area network
  • Internet Service Provider for example, AT&T, MCI, Sprint, EarthLink, MSN, GTE, etc.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne un système (10) de multiplexage par répartition en longueur d'onde, WDM. Le système (10) de WDM comprend un multiplexeur optique (34) configuré pour multiplexer une pluralité de longueurs d'onde de mesure et une pluralité de longueurs d'onde d'émission sur une fibre unique (18), un démultiplexeur optique (36) configuré pour démultiplexer une pluralité de longueurs d'onde de réception reçues en provenance de la fibre unique (18), la pluralité de longueurs d'onde de mesure se chevauchant avec les longueurs d'onde de réception, et un premier émetteur-récepteur optique (14) en communication optique avec le multiplexeur optique (34) et le démultiplexeur optique (36). Le système (10) de WDM comprend en outre une interface (22) permettant une communication entre un dispositif hôte (12) et le premier émetteur-récepteur optique (14), le dispositif hôte (12) comprenant une circuiterie (24) de traitement configurée pour commander l'émission du signal de mesure et déterminer une caractéristique de mesure associée à une version réfléchie du signal de mesure.
PCT/EP2020/075226 2020-09-09 2020-09-09 Réflectométrie optique en domaine temporel désagrégée accordée en lambda WO2022053133A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8693866B1 (en) * 2012-01-20 2014-04-08 Google Inc. Fiber diagnosis system for WDM optical access networks
US8948589B2 (en) * 2012-03-30 2015-02-03 Alcatel Lucent Apparatus and method for testing fibers in a PON
US20180006722A1 (en) * 2016-06-30 2018-01-04 Alcatel-Lucent Usa Inc. In-band optical-link monitoring for a wdm network

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8693866B1 (en) * 2012-01-20 2014-04-08 Google Inc. Fiber diagnosis system for WDM optical access networks
US8948589B2 (en) * 2012-03-30 2015-02-03 Alcatel Lucent Apparatus and method for testing fibers in a PON
US20180006722A1 (en) * 2016-06-30 2018-01-04 Alcatel-Lucent Usa Inc. In-band optical-link monitoring for a wdm network

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