JP5627427B2 - Wavelength multiplexing transmission apparatus and wavelength multiplexing transmission system - Google Patents

Description

  The present invention relates to a wavelength division multiplexing (WDM) apparatus and a wavelength division multiplexing transmission system for multiplexing and transmitting signal lights having a plurality of wavelengths.

  A wavelength division multiplexing (WDM) system is a wired optical communication system that converts a signal received from a user into different pre-assigned wavelengths, multiplexes a plurality of wavelengths, and transmits the signals via a single optical fiber. . In wavelength division multiplexing transmission systems used in the metro area, optical add / drop multiplexers (OADMs) that add (add), drop (drop), and transmit (thr) individual wavelengths, and losses in the transmission path Is a system configured by an optical amplifying unit that compensates for dispersion and a dispersion compensating unit that compensates for a dispersion value generated in the transmission line.

  In a wavelength division multiplexing (WDM) system, generally, in order to realize long-distance transmission, optical amplifiers are provided at both ends of a transmission line and are connected by an optical fiber for the transmission line. The optical fiber for the transmission path is not a single optical fiber, but a plurality of optical fibers are fused or extended by optical connector connection.

  When an optical fiber is connected, if the end face of the optical connector is contaminated or incomplete fitting occurs, light reflection occurs at the end face of the optical connector, and transmission quality may be deteriorated. In particular, in a system that detects the fiber fault by checking the absolute value of the optical output level and the return loss, an unnecessary optical attenuation function operates, which may cause disconnection of the main signal. As an improvement measure when a failure is detected, the end face of the optical connector is cleaned or the fitting is optimized. However, if the service is already in service, the main signal will be lost. It will have a big influence on.

  In order to deal with such problems, in order to detect the distance distribution of optical fiber propagation loss and the failure point, the measurement of the reflection level and the failure point are detected by OTDR (Optical Time-Domain Reflectometry). A method of detection is considered. For example, Patent Document 1 describes that in an optical transmission system, a long distance span is measured by an OTDR device before the start of operation or at the initial stage of operation.

JP 2004-282363 A

  However, in a system where the reflection level in the transmission line needs to be strictly managed, such as a wavelength division multiplexing transmission system, and when the system is constructed simultaneously at a plurality of sites, a plurality of expensive OTDR devices are required. There is a problem that the amount of capital investment increases.

  In addition, in order to use the OTDR device, it is necessary to remove the transmission line fiber used in the wavelength division multiplexing system and perform measurement, and the reliability of the system decreases, such as being unable to alarm or control the section. There is also.

  The present invention has been made to solve the above-described problems. In a wavelength division multiplexing transmission system, the reflection level is set without using an expensive OTDR device and with a transmission line fiber connected. The purpose is to identify the reflection point (failure location) by measuring.

A wavelength division multiplexing transmission apparatus according to the present invention is a wavelength division multiplexing transmission apparatus connected to another wavelength division multiplexing transmission apparatus by an optical fiber, and includes an optical multiplexing / demultiplexing unit that performs multiplexing / demultiplexing and transmission for each wavelength to be multiplexed. An optical amplifying unit that amplifies wavelength multiplexed light, an optical monitoring control unit that monitors a transmission path between other wavelength multiplexing transmission devices, and a signal from the optical monitoring control unit is inserted or branched into the transmission path A modulated optical transmitter that outputs a light monitoring signal wavelength, which is arbitrary modulated light for specifying a reflection point of light, comprising a WDM coupler and a system monitoring controller that monitors the system And a reflection point analysis unit for analyzing the reflected light from the transmission path and identifying the reflection point, and the wavelength band of the optical monitoring signal wavelength output from the modulated light transmission unit of the optical monitoring control unit is wavelength multiplexed. Wavelength multiplexed light output from transmission equipment to transmission line The optical monitoring control unit is different from the wavelength band, and the optical monitoring control unit further includes a reflector that reflects a part of the optical monitoring signal wavelength from another wavelength multiplexing transmission device located on the opposite side of the transmission path, and performs reflection point analysis. The unit compares the phase of the transmitted light transmitted by the modulated light transmission unit with the phase of the reflected light reflected by the reflector of another wavelength division multiplexing transmission device located on the opposite side of the transmission path. It measures the distance to the wavelength division multiplexing transmission apparatus .

  According to the present invention, it is possible to specify a reflection point (failure location) having a high reflection level with an inexpensive configuration without using an expensive OTDR device. In addition, since the reflection point (failure location) can be specified with the transmission line fiber connected, the reliability of the system can be improved.

It is a figure which shows the structure of the wavelength division multiplexing transmission system which concerns on Embodiment 1 of this invention. It is a figure explaining the reflective point analysis part which concerns on Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a figure which shows the flowchart at the time of performing a reflective point measurement by the node apparatus of both sides. It is a figure which shows the modification of the wavelength division multiplexing transmission system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the wavelength division multiplexing transmission system which concerns on Embodiment 2 of this invention. In Embodiment 2 of this invention, it is a figure which shows the spectrum at the time of taking out only the light for 1 wavelength from ASE light.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a wavelength division multiplexing transmission system according to Embodiment 1 of the present invention.
As shown in FIG. 1, the wavelength multiplexing transmission system includes node devices 10 and 20 for performing wavelength multiplexing transmission, and a plurality of transmission path fibers 101, 102, 103, 104 and optical connectors 110, 111, 112. Here, the transmission path fibers 101 and 102 are connected by an optical connector 110, the transmission path fibers 102 and 103 are connected by an optical connector 111, and the transmission path fibers 103 and 104 are connected by an optical connector 112.

  The node devices 10 and 20 are node devices for performing wavelength multiplexing transmission. First, the node device 10 will be described. The node device 10 includes an optical multiplexing / demultiplexing unit 11 that multiplexes, demultiplexes, or transmits wavelength multiplexed light, and optical amplification that collectively amplifies the wavelength multiplexed light that has passed through the optical multiplexing / demultiplexing unit 11. Unit 12, an optical supervisory control unit 14 that emits supervisory control light assigned to a wavelength different from the wavelength multiplexed light of the main signal for transmission path monitoring and information transmission of node device 10, and optical amplification unit 12 And a WDM coupler 13 that multiplexes or demultiplexes the light of the optical supervisory controller 14 and a system supervisory controller 15 that monitors the system. The wavelength multiplexed light and the supervisory control light are transmitted to the transmission line fiber 101 via the WDM coupler 13.

  The wavelength multiplexed light and supervisory control light transmitted to the transmission line fiber 101 pass through the transmission line fibers 102, 103, and 104, are received by the node device 20 that is the opposite side node device, and are monitored by the WDM coupler 23. Demultiplexed into wavelength multiplexed light. The wavelength multiplexed light demultiplexed by the WDM coupler 23 is collectively amplified by the optical amplifying unit 22 and transmitted to the optical multiplexing / demultiplexing unit 21. The supervisory control light demultiplexed by the WDM coupler 23 is transmitted to the optical supervisory control unit 24, and the optical supervisory control unit 24 processes the supervisory control signal.

  The WDM couplers 13 and 23, the transmission line fibers 101, 102, 103, and 104 and the optical connectors 110, 111, and 112 are optical devices capable of bidirectional transmission.

  The light monitoring control units 14 and 24 include modulated light transmission units 51 and 61, reflection point analysis units 52 and 62, and optical circulators 53 and 63 that change the light output direction according to the direction of the signal light. The system monitoring control units 15 and 25 have a function of processing information held by the light monitoring control units 14 and 24 and notifying the operator of the result via the user interface.

  Next, a method for specifying the reflection point position in the transmission path will be described. First, the system monitoring control unit 15 of the node device 10 controls the modulated light transmission unit 51 of the optical monitoring control unit 14 to transmit the modulated light. The transmitted modulated light is transmitted to the transmission path via the WDM coupler 13. If there is a reflection point in the transmission line caused by dirt on the optical connector end face or incomplete fitting, reflection occurs at that point, and the reflected light passes through the WDM coupler 13 again and is reflected by the light monitoring controller 14. Input to the analysis unit 52, and the reflection point (failure location) is specified as a result of the analysis.

FIG. 2 is a diagram showing the reflection point analysis unit 52 according to Embodiment 1 of the present invention.
The reflection point analysis unit 52 includes a photodiode (PD) 41 that converts the reflected light from the reflection point from an optical signal to an electrical signal, reflected wave and transmission wave buffer amplifiers 42 and 43, and other than transmission path distance information. A variable delay 44 that cancels the distance component, a variable delay 45 that is used when specifying the distance to the reflection point, a multiplier 46 that multiplies the reflected wave and the transmitted wave, a buffer amplifier 47 that amplifies the multiplication result, and smoothing A low-pass filter (LPF) 48 that performs the delay and a delay monitor 49 that monitors the value of the variable delay 45.

  The reflection point analysis unit 52 performs phase comparison between the reflected wave and the transmitted wave by the multiplier 46, feeds back the multiplication result to the variable delay 45, and controls the phase of the reflected wave and the transmitted wave to be in phase. Thus, information on the delay between the reflected wave and the transmitted wave is extracted, and the position of the reflection point is specified based on the information on the delay between the reflected wave and the transmitted wave.

  According to this method, without using an expensive OTDR device, there is no light source to be multiplexed in the optical multiplexing / demultiplexing portion, and the position where the reflection occurs due to dirt or incomplete fitting on the end face of the optical connector (failure location). Can be specified. Further, since the reflection position can be specified without removing the optical fiber from the wavelength division multiplexing transmission system, the reliability of the system can be improved.

  Here, although the reflection point measurement is possible by the above method, in order to more accurately identify the position of the reflection point, the reflection point measurement is also performed from the other node device 20 by the method described above. A case where a reflection point is specified based on the result will be described. FIG. 3 is a sequence flowchart when the reflection point measurement is performed by the node devices 10 and 20 on both sides of the transmission path.

  First, the system monitoring control unit 15 of the node device 10 instructs the start of reflection point measurement (step ST301). Next, the light monitoring controller 14 of the node device 10 receives the instruction to start the reflection point measurement and transmits a modulated wave (step ST302).

  Here, when the reflection position is specified by one node device, the reflection point position is specified by the node device 10 as described above, and the process ends. However, when the reflection position is specified using the node devices 10 and 20 on both sides, the system monitoring control unit 15 further checks whether or not the reflection point measurement is completed from the light reflected from the transmission path ( Step ST303). If not completed, the process returns to step ST302 to continue the measurement, and if completed, the process proceeds to the next step ST304.

  In step ST303, when the system monitoring control unit 15 receives the reflection point measurement completion notification, the light monitoring control unit 14 stops the transmission of the modulated light, and the system monitoring control unit 15 completes the reflection point measurement in the node device 10. This is notified to the system monitoring control unit 25 of the node device 20 (step ST304).

  When the system monitoring control unit 25 of the node device 20 receives the notification, the system monitoring control unit 25 instructs the start of reflection point measurement (step ST305). Next, the light monitoring control unit 24 of the node device 20 receives the instruction to start the reflection point measurement and transmits modulated light (step ST306). Then, the system monitoring control unit 25 checks whether or not the reflection point measurement is completed from the light reflected from the transmission path (step ST307). If not completed, the process returns to step ST306 to continue the measurement, and if completed, the process proceeds to the next step ST308.

  In step ST307, when the system monitoring control unit 25 receives the reflection point measurement completion notification, the light monitoring control unit 24 stops the transmission of the modulated light, and the reflection from the reflection point measurement result by the node device 10 and the node device 20 is reflected. A point is specified (step ST308).

  In addition, as a method of specifying the reflection point from the result of the reflection point measurement by the two node devices, an optical connector or a fitting portion that is closest to the intermediate point of the measured reflection position is used as the reflection point (failure point). There are methods such as specifying.

  According to this method, since the range of the reflection points can be narrowed compared to the case where the reflection points are measured by one node device, the reflection points can be specified with higher accuracy.

  Further, the light monitoring control unit 14 may be provided with a reflector that reflects a part of the light monitoring signal wavelength. FIG. 4 is a diagram showing a modification of the wavelength division multiplexing transmission system according to Embodiment 1 of the present invention. The difference from the wavelength division multiplexing transmission system according to Embodiment 1 shown in FIG. 1 is that the optical monitoring control units 14 and 24 of the node devices 10 and 20 include reflectors 54 and 64, respectively.

  The reflector 54 sends the reflected light from the reflection point in the transmission path as it is to the reflection point analysis unit 52, but reflects the optical monitoring signal wavelength from the node device 20 which is the opposite side node device in the transmission path. is there. Similarly, the reflector 64 of the node device 20 reflects the optical monitoring signal wavelength from the node device 10, and the reflectors 54 and 64 can adjust the amount of reflection.

  As a result, the reflection point analysis unit 52 of the node device 10 reflects the reflected light of the optical monitoring signal transmitted from the own node reflected from the reflection point in the transmission path, and the reflector of the node device 20 that is the opposite side node device. The reflected light reflected by 64 can be distinguished and detected. Then, the distance from the node device 20 on the opposite side of the transmission path is measured by comparing the phase of the transmitted light from the optical monitoring control unit 14 of the own node and the phase of the reflected light from the reflector 64 of the node device 20. can do.

  Here, since the distance between the node device 10 and the opposite-side node device 20 is a known value, the failure point is determined by comparing the known value with the distance between the opposite-side node device 20 by the measurement. It becomes possible to calibrate the measurement result of the position of the reflection point.

  According to this method, when measuring the position of the reflection point, the measurement result of the reflection point can be calibrated by measuring the distance from the node device on the opposite side of the transmission line, and the reflection point can be specified with higher accuracy. be able to.

Embodiment 2. FIG.
FIG. 5 is a diagram showing a configuration of a wavelength division multiplexing transmission system according to Embodiment 2 of the present invention.
As in the first embodiment, as shown in FIG. 5, in the wavelength multiplexing transmission system, the node devices 30 and 40 for performing wavelength multiplexing transmission include a plurality of transmission line fibers 101, 102, 103, and 104. The optical connectors 110, 111, and 112 in the transmission path are connected.

  The node device 30 varies the level for each wavelength by optical amplification units 74 and 22 that amplify the received wavelength multiplexed light, an optical demultiplexing unit (DEMUX) 75 that performs wavelength demultiplexing, and a VOA (Variable Optical Attenuator). An optical level adjustment unit 76, an optical multiplexing unit (MUX) 77 for combining wavelengths, an optical amplification unit 12 for amplifying the level of wavelength multiplexed light, an output control unit 78 for controlling the output of the amplifier, and an optical level adjustment unit 76. It comprises a modulation control unit 79 that controls, a reflection point analysis unit 73 that performs reflection point measurement, an optical circulator 71, and an optical coupler 72.

  Here, the optical amplifying unit 74 is for making the level of light from the transmission line constant, and adjusts the level of the optical signal lost in the transmission line. Further, the system monitoring control unit 15 controls the output control unit 78 that controls the output of the optical amplifier and the modulation control unit 79 that generates modulated light by turning on / off the light by the light level adjusting unit 76. The result of analyzing the reflected light from the transmission path is transmitted from the reflection point analysis unit 73 to the system monitoring control unit 15.

  In the wavelength division multiplexing transmission system according to the second embodiment, spontaneous emission light (ASE light: Amplified Spontaneous) of an optical amplifier 74 for making the light level from the transmission line constant as a light source used for reflection point measurement in the transmission line. Emission). Since the ASE light is broadband light as shown in FIG. 6A, the light reflected and returned from the reflection point also becomes broadband light, and the reflection point cannot be specified. Therefore, by setting the optical demultiplexing unit (DEMUX) 75 and the optical level adjusting unit 76 to transmit only one wavelength, the band can be limited (filtered) as shown in FIG. The light can be modulated by turning on / off the light by the light level adjusting unit 76.

  By the above method, a modulated wave having a narrow band can be transmitted from the node device 30, and the reflected point measurement is performed by inputting the reflected wave from the reflected point to the reflected point analysis unit 73 and comparing it with the transmitted light as in the first embodiment. By doing so, the position of the reflection point can be specified.

  According to this method, as in the first embodiment, without using an expensive OTDR device, there is no light source to be multiplexed in the optical multiplexing / demultiplexing unit, and reflection is caused by dirt on the optical connector end face or incomplete fitting. The position (failure location) where the error occurs can be specified, and the reflection position can be specified without removing the optical fiber from the wavelength division multiplexing transmission system, so that the reliability of the system can be improved. In addition to the effect of the above, since the spontaneous emission light (ASE light) of the optical amplifier is used, even if the system does not have an optical monitoring control unit, it is not necessary to remove the optical fiber and perform highly reliable reflection point measurement. Can do. Further, by using light obtained by filtering and modulating the ASE light, the band of light to be transmitted for measuring the reflection point is narrow, so that the light that is reflected and returned is also narrow-band light. The reflection point can be specified.

  Also, in the case of the second embodiment in which a reflection point is specified using ASE light, the reflection point may be measured using the node devices 30 and 40 on both sides of the transmission line, as in the first embodiment. . Although the flowchart in this case is not shown, it is basically the same as FIG. 3. When the start of reflection point measurement is instructed from the system monitoring controller 15 of the node device 30, a modulated wave is input from the node device 30. The reflection point is specified, and the system monitoring control unit 15 monitors whether the specification of the reflection point is completed. At this time, the modulated wave from the node device 30 does not output the modulated light from the optical monitoring control unit 14 of the node device 10 as in the first embodiment, but the ASE light of the optical amplifier 74 of the node device 30. The modulated modulated light is output. When the system monitoring control unit 25 of the node device 40 receives a notification that the specification of the reflection point has been completed, the system monitoring control unit 25 instructs the start of reflection point measurement, and receives a modulated wave from the node device 40. Specify the reflection point. Then, the position of the reflection point is narrowed down from the measurement results by both node devices.

  According to this method, it is possible to specify the reflection point with higher accuracy than when the reflection point is measured by one node device.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  10, 20, 30, 40 Node device, 11, 21 Optical multiplexing / demultiplexing unit, 12, 22, 74, 84 Optical amplification unit, 13, 23 WDM coupler, 14, 24 Optical monitoring control unit, 15, 25 System monitoring control unit , 41 Photodiode (PD), 42, 43, 47 Buffer amplifier, 44, 45 Variable delay, 46 Multiplier, 48 Low pass filter (LPF), 49 Delay monitor, 51, 61 Modulated light transmitter, 52, 62, 73 , 83 Reflection point analysis unit, 53, 63, 71, 81 Optical circulator, 54, 64 reflector, 72, 82 Optical coupler, 75, 85 Optical demultiplexing unit (DEMUX), 76, 86 Optical level adjustment unit, 77, 87 Optical multiplexing unit (MUX), 78, 88 Output control unit, 79, 89 Modulation control unit, 101, 102, 103, 104 Transmission path fiber, 1 10, 111, 112 Optical connector.

Claims (2)

A wavelength multiplexing transmission device connected to another wavelength multiplexing transmission device by an optical fiber,
Optical supervisory control for monitoring transmission paths between optical multiplexing / demultiplexing units for multiplexing / demultiplexing and transmission for each wavelength to be multiplexed, optical amplification units for amplifying wavelength multiplexed light, and other wavelength multiplexing transmission devices A WDM coupler that inserts or branches a signal from the optical monitoring control unit into a transmission path, and a system monitoring control unit that monitors the system,
The light monitoring control unit analyzes a modulated light transmitting unit that outputs a light monitoring signal wavelength, which is arbitrary modulated light for specifying a reflection point of light, and analyzes the reflected light from the transmission path, and specifies the reflection point and a reflection point analyzer for,
The wavelength band of the optical monitoring signal wavelength output from the modulated light transmission unit of the optical monitoring control unit is different from the wavelength band of the wavelength multiplexed light output from the wavelength multiplexing transmission device to the transmission path,
The optical monitoring control unit further includes a reflector that reflects a part of the optical monitoring signal wavelength from another wavelength multiplexing transmission device located on the opposite side of the transmission path ,
The reflection point analyzer compares the phase of the transmitted light transmitted by the modulated light transmitter with the phase of the reflected light reflected by a reflector of another wavelength division multiplexing apparatus located on the opposite side of the transmission path. And measuring the distance between the own apparatus and the other wavelength division multiplexing transmission apparatus. A plurality connected wavelength division multiplexed transmission system by the optical fiber wavelength division multiplexing transmission apparatus according to claim 1 Symbol placement,
In one of the wavelength division multiplexing transmission apparatuses at both ends of the transmission path, the reflection point is identified by the optical supervisory control unit, and after the reflection point in the one wavelength division multiplexing transmission apparatus has been identified, The reflection point specified by the one wavelength division multiplex transmission apparatus and the reflection point specified by the other wavelength division multiplex transmission apparatus are executed by specifying the reflection point by the optical supervisory control unit in the other wavelength division multiplex transmission apparatus located. A wavelength division multiplexing transmission system, wherein a more accurate reflection point is determined based on the point.

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