JP4018075B2 - Optical fiber fault isolation method - Google Patents

Description

  The present invention relates to an optical fiber failure isolation method used for an optical transmission system. In particular, the present invention relates to an optical fiber fault isolation method used in an optical transmission system using a high-power transmitter.

  In the conventional optical transmission system, an optical connector is connected to the connection point of the optical fiber in the relay section from the viewpoint of workability. When a failure occurs in the optical fiber in the relay section, the optical connector at the connection point is attached and detached to determine the failure location, and the presence or absence of the failure of the optical fiber is determined by an optical tester or the like.

  However, in recent optical transmission systems that perform remote excitation light transmission aiming at long-distance transmission, the optical power of signal light or excitation light has exceeded 1 W (see, for example, Patent Document 1). When the optical power of signal light or pumping light exceeds 1 W, there is a risk of occurrence of a fiber fuse at the connection point of the optical connector. For this reason, in recent optical transmission systems aiming at long-distance optical transmission, optical fibers are fused and connected without using an optical connector. When a failure occurs in such a fusion-connected optical fiber line, the optical fiber cannot be isolated by disconnecting the optical connector.

Further, in the optical transmission system that performs remote pumping light transmission, the pumping light for remote pumping is stopped together with the signal light for transmission at the time of failure, so that the remote pumping light amplifier does not operate. Therefore, the remote pumping optical amplifier composed of the erbium-doped optical fiber becomes a loss medium that absorbs signal light for transmission in the 1.55 μm band. Therefore, the optical pulse tester having the 1.55 μm band as the test wavelength cannot identify the failure of the optical fiber far from the remote pumping optical amplifier.
Japanese Patent Laid-Open No. 3-54530

  Under such circumstances, it is an object of the present invention to provide an optical fiber fault isolation method for optical fiber lines that cannot use optical connectors.

  In order to achieve the above object, in the optical fiber fault isolation method of the present invention, the first optical fiber mainly laid in the communication equipment building and the second optical fiber mainly laid outside the communication equipment building. Are detected through optical couplers, and signal light from an optical transmission device connected to the first optical fiber is detected to determine whether or not the first optical fiber has failed. The failure point of the second optical fiber is identified by detecting the backscattered light from the second optical fiber with an optical pulse tester, and the failure between the first optical fiber and the second optical fiber is identified. .

  By this optical fiber failure isolation method, it is possible to isolate a failure between an optical fiber laid in the site and an optical fiber laid outside the site, even if the optical fiber line cannot use an optical connector.

Specifically, the present invention includes a first optical fiber that transmits the signal light from the optical transmission device, the signal light from the first optical fiber coupled to the second optical fiber, and the first optical fiber. Second light optically coupled to the first optical fiber via an optical coupler that branches the signal light from the optical fiber and inserts the test light from the optical pulse tester into the second optical fiber. An optical fiber fault isolation method for isolating a fault with a fiber, wherein the monitor device detects signal light from the optical transmitter branched by the optical coupler, thereby determining whether there is a fault in the first optical fiber The optical transmission device includes a pumping light source for remote pumping amplification and transmits pumping light from the pumping light source, the second optical fiber includes an erbium-doped optical fiber in a part thereof, and the optical coupler Inserted in A second optical fiber failure is detected by amplifying the test light from the optical pulse tester with the erbium-doped optical fiber and detecting the backscattered light from the amplified test light with the optical pulse tester for coherent detection. An optical fiber failure isolation method characterized by identifying a location and isolating a failure between the first optical fiber and the second optical fiber.

By using the amplification effect of the erbium-doped optical fiber, the failure location can be specified even for a remote optical fiber. By performing coherent detection, a highly sensitive optical pulse test can be realized, and a fault location can be identified even with a remote optical fiber.

  In this application, an optical pulse tester is a device that detects a backscattered light propagating in the direction of an optical pulse tester out of scattered light generated by Rayleigh scattering in an optical fiber by entering a light pulse from one end of the optical fiber. This means a tester that can identify the location of an optical fiber failure.

  An erbium-doped optical fiber refers to an optical fiber in which erbium, which is a rare earth, is added to an optical fiber, and signal light incident in a state excited by pumping light is amplified by stimulated emission.

  According to the present invention, it is possible to provide an optical fiber failure isolation method even for an optical fiber line that cannot use an optical connector.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not construed as being limited to these descriptions.

(Embodiment 1)
In the present embodiment, the first optical fiber that transmits the signal light from the optical transmission device, the signal light from the first optical fiber are coupled to the second optical fiber, and the first optical fiber A second optical fiber that splits the signal light and is optically coupled to the first optical fiber via an optical coupler that inserts the test light from the optical pulse tester into the second optical fiber; An optical fiber fault isolation method for isolating a failure, wherein the monitor device detects signal light for transmission from the optical transmission device branched by the optical coupler to determine whether there is a failure in the first optical fiber. The failure point of the second optical fiber is specified by detecting the backscattered light by the optical pulse tester from the optical pulse tester inserted by the optical coupler, and the first optical fiber and the second An optical fiber fault isolation method characterized by carving a failure of the optical fiber.

  FIG. 1 is a diagram for explaining the present embodiment, in which 10 is a communication facility building that accommodates an optical transmitter and a monitoring device, 11 is a first optical fiber laid mainly in the communication facility building, and 12 is a main The second optical fiber laid outside the communication equipment building, 21 is an optical transmission device for transmitting signal light, 22 is coupled to the second optical fiber 12 and the signal light from the first optical fiber 11 An optical coupler for branching the signal light from one optical fiber 11 to the monitor device 24 and inserting the test light from the optical pulse tester 23 into the second optical fiber 12. , 24 is a monitor device for detecting signal light for transmission from the optical transmission device 21, and 31 is a transmission circuit for transmission that is included in the optical transmission device 21 and transmits signal light for transmission. .

  In the present application, the signal light for transmission refers to signal light that is transmitted to transmit information to the optical receiving device that the optical transmitting device 21 faces.

  In FIG. 1, a transmission transmission circuit 31 included in the optical transmission device 21 is connected to the first optical fiber 11. The first optical fiber 11 is connected to the input terminal of the optical coupler 22, and the second optical fiber 12 is connected to the output terminal of the optical coupler 22. A monitor device 24 is connected to the branch terminal of the optical coupler 22, and an optical pulse tester is connected to the insertion terminal of the optical coupler 22. The first optical fiber 11 and the second optical fiber 12 are optically coupled via an optical coupler 22. Since one end of the second optical fiber 12 is connected to the optical coupler, one end is accommodated in the communication facility building 10, but most of the second optical fiber 12 is connected to another communication facility building or the like in order to connect the other end to the communication facility building. It is laid outside.

  In FIG. 1, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the transmission circuit 31 for transmission included in the optical transmission device 21 transmits the signal light for transmission. The transmission signal light propagated through the first optical fiber 11 is branched by the optical coupler 22, and the transmission signal light is detected by the monitor device 24. If the signal light for transmission can be detected by the monitor device 24, it is determined that the first optical fiber 11 is normal. If the monitor device 24 cannot detect the signal light for transmission, it is determined that the first optical fiber 11 is broken.

  In the optical fiber fault isolation method according to the present embodiment, since a transmission transmission circuit can be used for transmission of transmission signal light, it is not necessary to newly provide a monitoring optical transmission circuit.

  The signal light for transmission may be detected by detecting the optical power of the signal light. Since an optical power meter can be used for detecting optical power, the monitor device 24 can be configured simply.

  For the detection of the signal light for transmission, transmission information may be detected from the signal light. Since transmission information is detected from signal light, signal light for transmission can be detected without being disturbed by external noise light. Transmission information may be detected by extracting a signal clock from signal light and detecting the clock, or establishing frame synchronization of signal light and detecting a frame. Alternatively, specific information included in the signal light frame may be detected.

  When a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the second optical fiber is simultaneously with or before or after the determination of the presence or absence of the failure of the first optical fiber 11. Twelve fault locations are identified. In FIG. 1, an optical pulse tester 23 transmits optical pulse test light. The test light is inserted from the optical coupler 22 into the second optical fiber 12 and propagates through the second optical fiber 12. Rayleigh scattering occurs when the test light propagates, and backscattered light returning in the direction of the optical coupler 22 propagates through the second optical fiber 12 and is branched by the optical coupler 22 and detected by the optical pulse tester 23. The If the backscattered light can be detected up to a predetermined length of the second optical fiber 12 by the optical pulse tester 23, it is determined that the second optical fiber 12 is normal. If the backscattered light cannot be detected to the predetermined length of the second optical fiber 12 by the optical pulse tester 23, it is determined that the second optical fiber 12 is broken. The predetermined length may be measured in advance. Furthermore, a failure location can be specified from the length of the optical fiber detecting the backscattered light.

  As described above, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the monitor device 24 determines whether or not the first optical fiber 11 has failed, and performs an optical pulse test. By determining whether or not there is a failure in the second optical fiber 12 with the device 23, the failure between the first optical fiber 11 and the second optical fiber 12 can be identified. Further, when the optical pulse tester is used, it is possible to identify up to the failure location of the second optical fiber 12.

(Embodiment 2)
In the present embodiment, the first optical fiber that transmits the signal light from the optical transmission device, the signal light from the first optical fiber are coupled to the second optical fiber, and the first optical fiber A second optical fiber that splits the signal light and is optically coupled to the first optical fiber via an optical coupler that inserts the test light from the optical pulse tester into the second optical fiber; An optical fiber fault isolation method for isolating a fault, wherein a monitoring signal from the optical transmission device branched by the optical coupler is detected by a monitor device to determine whether there is a fault in the first optical fiber. The failure point of the second optical fiber is specified by detecting the backscattered light by the optical pulse tester from the optical pulse tester inserted by the optical coupler, and the first optical fiber and the second An optical fiber fault isolation method characterized by carving a failure of the optical fiber.

FIG. 2 is a diagram for explaining the present embodiment, and the same reference numerals as those in FIG. 1 represent the same meaning. A monitoring transmission circuit 32 is included in the optical transmission device 21 and transmits a monitoring signal light.
In the present application, the monitoring signal light refers to signal light transmitted by the optical transmission device 21 to monitor the optical fiber, the optical transmission device, and the optical reception device when a failure occurs, apart from information transmission.

  In FIG. 2, the monitoring transmission circuit 32 included in the optical transmission device 21 is connected to the first optical fiber 11. The first optical fiber 11 is connected to the input terminal of the optical coupler 22, and the second optical fiber 12 is connected to the output terminal of the optical coupler 22. A monitor device 24 is connected to the branch terminal of the optical coupler 22, and an optical pulse tester is connected to the insertion terminal of the optical coupler 22. The first optical fiber 11 and the second optical fiber 12 are optically coupled via an optical coupler 22. Since one end of the second optical fiber 12 is connected to the optical coupler, one end is accommodated in the communication facility building 10, but most of the second optical fiber 12 is connected to another communication facility building or the like in order to connect the other end to the communication facility building. It is laid outside.

  The transmission transmission circuit 31 described in FIG. 1 and the monitoring transmission circuit 32 in FIG. 2 may be separated by an optical switch. That is, the transmission switch 31 is connected to the first optical fiber 11 during normal operation, and the optical switch is controlled so that the monitoring transmission circuit 32 is connected to the first optical fiber 11 during fault isolation. Further, the transmission transmission circuit 31 and the monitoring transmission circuit 32 may be coupled to the first optical fiber 11 with an optical coupler. That is, control is performed so that the transmission transmitter circuit 31 operates during normal operation and the monitoring transmission circuit 32 operates during fault isolation.

  In FIG. 2, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the monitoring transmission circuit 32 included in the optical transmission device 21 transmits the monitoring signal light. The monitoring signal light propagated through the first optical fiber 11 is branched by the optical coupler 22, and the monitoring signal light is detected by the monitor device 24. If the monitoring signal light can be detected by the monitor device 24, it is determined that the first optical fiber 11 is normal. If the monitoring signal light cannot be detected by the monitor device 24, it is determined that the first optical fiber 11 is broken.

  In the optical fiber fault isolation method of the present embodiment, since the monitoring signal light is used, it is possible to obtain a signal light suitable for monitoring. For example, the signal light level suitable for monitoring can be set, or a monitoring pilot signal can be superimposed.

  For detection of the monitoring signal light, the optical power of the signal light may be detected. Since an optical power meter can be used for detecting optical power, the monitor device 24 can be configured simply.

  For detection of the monitoring signal light on which the pilot signal is superimposed, the pilot signal may be detected from the signal light. Since the pilot signal is detected from the signal light, the pilot signal can be detected without being disturbed by external noise light. The pilot signal may be a repetitive signal having a specific frequency or a digital signal having a specific frame.

  When a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, as in the previous embodiment, at the same time as determining whether there is a failure in the first optical fiber 11, Or, before and after, the failure point of the second optical fiber 12 is specified by the optical pulse tester.

  As described above, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the monitor device 24 determines whether or not the first optical fiber 11 has failed, and performs an optical pulse test. By determining whether or not there is a failure in the second optical fiber 12 with the device 23, the failure between the first optical fiber 11 and the second optical fiber 12 can be identified. Further, when the optical pulse tester is used, it is possible to identify up to the failure location of the second optical fiber 12.

(Embodiment 3)
In recent optical transmission systems, optical amplification using an erbium-doped optical fiber and Raman amplification using the Raman effect are used to increase the transmission distance. For these amplifications, the optical transmitter is provided with a pumping light source. Such a pumping light source can also be used to determine whether or not the first optical fiber 11 has failed. In this embodiment, the optical transmission device includes a pumping light source for remote pumping light amplification or Raman amplification in the above-described embodiment, transmits pumping light from the pumping light source, and is branched by an optical coupler. This is an optical fiber failure isolation method for determining the presence or absence of a failure of the first optical fiber by detecting the optical power of the excitation light from the excitation light source with a monitor device.

  FIG. 3 is a diagram for explaining the present embodiment, and the same reference numerals as those in FIG. 1 represent the same meaning. 33 is a pumping light source for remote pumping light amplification or Raman amplification included in the optical transmitter 21, and 34 is a pumping light coupling coupler that couples signal light from the transmission circuit 31 for transmission and pumping light from the pumping light source 33. .

  In FIG. 3, the transmission circuit 31 and the excitation light source 33 operate normally to transmit both the transmission signal light and the excitation light, and when the failure is isolated, the transmission circuit 31 is stopped to activate the excitation light source. Only 33 is controlled to transmit the excitation light.

  In FIG. 3, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the excitation light source 33 included in the optical transmission device 21 transmits the excitation light, and the first light The excitation light propagated through the fiber 11 is branched by the optical coupler 22 and the excitation light is detected by the monitor device 24. If the monitor device 24 can detect the excitation light, it is determined that the first optical fiber 11 is normal. If excitation light cannot be detected by the monitor device 24, it is determined that the first optical fiber 11 has failed.

  In the optical fiber fault isolation method according to the present embodiment, the pumping light for remote pumping light amplification or Raman amplification is used, so that no new circuit is required. For detecting the excitation light, it is desirable to detect the optical power of the excitation light. Since an optical power meter can be used for detecting optical power, the monitor device 24 can be configured simply.

  When a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, as in the previous embodiment, at the same time as determining whether there is a failure in the first optical fiber 11, Or, before and after, the failure point of the second optical fiber 12 is specified by the optical pulse tester.

  As described above, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the monitor device 24 determines whether or not the first optical fiber 11 has failed, and performs an optical pulse test. By determining whether or not there is a failure in the second optical fiber 12 with the device 23, the failure between the first optical fiber 11 and the second optical fiber 12 can be identified. Further, when the optical pulse tester is used, it is possible to identify up to the failure location of the second optical fiber 12.

(Embodiment 4)
When there are many optical fibers to be identified as faults, it is necessary to switch the connection between the monitoring device and the optical pulse tester to the optical fibers that are identified as faults. FIG. 4 shows a form of optical fiber connection switching using an optical switch. The same reference numerals as those in FIG. 1 represent the same meaning. Reference numeral 41 denotes an optical fiber selection optical switch for connecting an arbitrary optical fiber to a monitor device and an optical pulse tester. When a failure occurs in the optical line, the failed optical line is connected to the monitor device and the optical pulse tester by the optical fiber selection optical switch 41. With this optical fiber selection optical switch 41, it is possible to isolate a failure of an optical fiber in an arbitrary optical line.

  Connection selection with an optical fiber by the optical fiber selection switch 41 and operations of the monitoring device 24 and the optical pulse tester 23 may be controlled using a communication line such as a LAN (Local Area Network). Further, failure isolation including an optical transmission device and an optical reception device facing the optical transmission device may be automatically controlled by a communication line.

(Embodiment 5)
FIG. 5 shows the configuration of an optical coupler that optically couples the first optical fiber and the second optical fiber. 5 (1) and FIG. 5 (2) are examples configured with planar waveguide circuits, and FIGS. 5 (3) and 5 (4) are examples configured with optical fiber couplers. 5 (1), 5 (2), 5 (3), and 5 (4), the first optical fiber is connected to the input port A, and the second optical fiber is connected to the output port B, respectively. The monitor port is connected to the branch port C, and the optical pulse tester is connected to the insertion port D.

  Since the optical coupler of FIG. 5A has only one branch insertion point, branch loss and insertion loss can be reduced. The optical coupler of FIG. 5B can reduce the leakage from the insertion port to the branch port. The optical couplers of FIGS. 5 (3) and 5 (4) can be realized by simply processing an optical fiber. Since the optical coupler of FIG. 5 (3) has one branch insertion point, branch loss and insertion loss can be reduced. The optical coupler of FIG. 5 (4) can reduce leakage from the insertion port to the branch port.

(Embodiment 6)
In recent optical transmission systems, an erbium-doped optical fiber is placed in the middle of the optical line to increase the transmission distance, and the erbium-doped optical fiber is pumped remotely to pump the erbium-doped optical fiber. It has a light source. Such a pumping light source and an erbium-doped optical fiber can also be used to determine whether or not the second optical fiber 12 has failed. In this embodiment, the optical transmitter includes a pumping light source for remote pumping amplification and transmits pumping light from the pumping light source, and the second optical fiber includes erbium in a part thereof. By amplifying the test light from the optical pulse tester including the doped optical fiber and inserted by the optical coupler with the erbium-doped optical fiber, and detecting the backscattered light by the amplified test light with the optical pulse tester, This is an optical fiber failure isolation method for identifying a failure location of the second optical fiber.

  FIG. 6 is a diagram for explaining this embodiment, and the same reference numerals as those in FIG. 3 represent the same meanings. Reference numeral 13 denotes an erbium-doped optical fiber.

  In FIG. 6, the transmission circuit 31 and the excitation light source 33 operate normally to transmit both the transmission signal light and the excitation light. When the fault is isolated, the transmission circuit 31 is stopped and the excitation light source Only 33 is controlled to transmit the excitation light.

  When a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the second optical fiber is simultaneously with or before or after the determination of the presence or absence of the failure of the first optical fiber 11. Twelve fault locations are identified. In FIG. 6, test light of an optical pulse having a wavelength having an amplification effect is transmitted from the optical pulse tester 23 through the erbium-doped optical fiber 13. The test light is inserted from the optical coupler 22 into the second optical fiber 12 and propagates through the second optical fiber 12. Rayleigh scattering occurs when the test light propagates, and backscattered light returning in the direction of the optical coupler 22 propagates through the second optical fiber 12 and is branched by the optical coupler 22 and detected by the optical pulse tester 23. The

  If the backscattered light can be detected up to a predetermined length of the second optical fiber 12 by the optical pulse tester 23, it is determined that the second optical fiber 12 is normal. If the backscattered light cannot be detected to the predetermined length of the second optical fiber 12 by the optical pulse tester 23, it is determined that the second optical fiber 12 is broken. Furthermore, a failure location can be specified from the length of the optical fiber detecting the backscattered light.

  In FIG. 6, since the erbium-doped optical fiber 13 is included in the middle of the second optical fiber 12, the optical pulse is amplified and propagated to the second optical fiber 12 ahead of the erbium-doped optical fiber 13. . Further, since the backscattered light is also amplified when returning, even if the second optical fiber 12 is long, it is possible to identify a fault location that has occurred in the second optical fiber 12.

  As described above, when a failure occurs in the optical line including the first optical fiber 11 and the second optical fiber 12, the monitor device 24 determines whether or not the first optical fiber 11 has failed, and performs an optical pulse test. By determining whether or not there is a failure in the second optical fiber 12 with the device 23, the failure between the first optical fiber 11 and the second optical fiber 12 can be identified. In addition, when an optical pulse tester that transmits an optical pulse having an amplifying function with an erbium-doped optical fiber is used, a failure location can be specified even if the second optical fiber 12 is long.

(Embodiment 7)
In the present embodiment, coherent detection is adopted for detecting the backscattered light by the optical pulse tester in the above-described embodiment. When coherent detection is used, noise can be suppressed, and the dynamic range to be detected is expanded. Therefore, even in the case of an optical fiber with a large optical loss or a long optical fiber, it is possible to identify a faulty part of the optical fiber. .

  The optical fiber fault isolation method of the present invention is not limited to an optical transmission system that transmits one wavelength with a single optical fiber, but an optical transmission system that transmits multiple wavelengths with a single optical fiber, or a single optical fiber. The present invention can also be applied to an optical transmission system that performs bidirectional transmission using a fiber.

It is a figure explaining the optical fiber failure isolation method of this embodiment. It is a figure explaining the optical fiber failure isolation method of this embodiment. It is a figure explaining the optical fiber failure isolation method of this embodiment. It is a figure explaining the method to select the optical fiber applied to the optical fiber failure isolation method of this embodiment. It is a figure explaining the structure of the optical coupler applied to the optical fiber failure isolation method of this embodiment. It is a figure explaining the optical fiber failure isolation method of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Communication equipment building 11 1st optical fiber 12 2nd optical fiber 13 Erbium doped optical fiber 21 Optical transmission device 22 Optical coupler 23 Optical pulse tester 24 Monitor device 31 Transmission circuit 32 Transmission circuit 33 Monitoring transmission circuit 33 Excitation light source 34 Pumping optical coupler 41 Optical fiber selection optical switch

Claims (1)

A first optical fiber for transmitting signal light from an optical transmission device including a pumping light source for remote pumping amplification , and signal light from the first optical fiber is a second optical fiber , part of which is erbium The first optical fiber is coupled to an optical fiber including a doped optical fiber, the signal light from the first optical fiber is branched, and the test light from the optical pulse tester is inserted into the second optical fiber via the optical coupler. An optical fiber fault isolation method for isolating a fault between a second optical fiber optically coupled to one optical fiber,
Determine the presence or absence of a failure of the first optical fiber by detecting the monitor device a signal light from the optical transmission apparatus which is branched by the optical coupler, the optical transmitter is the excitation light from the front Symbol excitation light source transmitted, said second optical fiber, the test light from the optical pulse tester branched by the optical coupler amplified by the erbium-doped optical fiber, coherently detecting the backscattered light due to the amplified test light the An optical fiber fault isolation characterized by identifying a fault location of the second optical fiber by detecting with an optical pulse tester and isolating the fault between the first optical fiber and the second optical fiber Method.

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