JP5811259B2 - Optical line monitoring system - Google Patents

Description

  The present invention relates to an optical line monitoring system.

  An optical line monitoring system using OTDR (Optical Time Domain Reflectometry) technology introduces pulse test light output from an optical pulse tester to one end of an optical fiber line and propagates the pulse test light to the optical fiber line. The backscattered light generated during propagation of the pulse test light is taken out from the one end side and received by the optical pulse tester, and the optical fiber line is monitored based on the temporal change of the intensity of the received backscattered light.

  If the optical fiber line to be monitored is disconnected, the pulse test light is reflected at the disconnection position and becomes backscattered light, so that the backscattered light at the time corresponding to the disconnection position becomes strong. That is, the presence or absence of a failure in the optical fiber line can be detected based on the time change of the intensity of the backscattered light received by the optical pulse tester, and the failure position in the optical fiber line can be detected.

NTT Technical Journal, December 2006, pp. 58-61

  In the conventional optical line monitoring system, when a plurality of optical fiber lines are monitored, it is necessary to propagate the pulse test light to each optical fiber line sequentially one by one.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an optical line monitoring system capable of monitoring a plurality of optical fiber lines in a short time.

The optical line monitoring system according to the present invention propagates pulse test light to each of the N optical fiber lines, and based on the time change of the intensity of the backscattered light generated during propagation of the pulse test light. A system for monitoring an optical fiber line, (1) an optical pulse tester that outputs pulse test light and inputs backscattered light to detect temporal changes in the intensity of the backscattered light; and (2) A pulse test light having a port P and ports P _{0 to} P _N and outputted from the optical pulse tester is inputted to the port P, and a pulse test light is selected from one selected from the ports P _{0 to} P _N (3) A splitter that inputs the pulse test light output from the port P _{0 of the} optical switch, outputs the pulse test light by N-branching, and (4) The pulse test light is output by the splitter. Is N-branched and output The n branch pulsed test light of the light, and, one of the output pulse test light from port P _n of the optical switch, to propagate to the n optical fiber line of the N optical fiber line An optical coupling part, and (5) a reflection part provided in each of the N optical fiber lines, the optical path length between the installation position and the optical pulse tester being different from each other, and reflecting the pulse test light It is characterized by. However, N is an integer greater than or equal to 2, and n is each integer greater than or equal to 1 and less than or equal to N. An optical pulse tester, an optical switch, a splitter, and an optical coupling unit are provided in the center.

Furthermore, the optical line monitoring system according to the present invention is provided in each of the N optical fiber lines when (a) the pulse test light input to the port P is selectively output from the port P ₀ by the optical switch. The pulse width of the pulse test light is reduced so that reflections at the respective reflection portions can be mutually decomposed in the optical pulse tester, and the N optical fiber lines pass from the port P _{0 of the} optical switch through the splitter and the optical coupling portion. Based on the time variation of the intensity of the backscattered light, propagating the pulsed test light, and the backscattered light generated in the N optical fiber lines is input to the optical pulse tester through the optical coupling unit, the splitter, and the optical switch. N optical fiber lines are collectively monitored, and (b) any n-th optical fiber based on the intensity of the backscattered light generated at the reflecting portion provided in each of the N optical fiber lines When it is determined by collective monitoring that a failure has occurred in the line, the pulse test light input to the port P by the optical switch is selectively output from the port _Pn , and the optical switch from the port _{Pn of the} optical switch passes through the optical coupling unit. The pulse test light is propagated to the n optical fiber line, and the backscattered light generated in the nth optical fiber line is input to the optical pulse tester through the optical coupling part and the optical switch, and the time change of the intensity of this backscattered light The n-th optical fiber line is individually monitored based on the above.

  In the optical line monitoring system according to the present invention, the reflecting portion is provided at the far end of any one of the N optical fiber lines, and has a first port, a second port, and a third port, An optical coupler having a first port connected to the far end of the optical fiber line, outputting light input to the first port from the second port, and outputting light input to the third port from the first port; It is preferable that the optical waveguide which optically connects between the 2nd port and 3rd port of a coupler is included.

  According to the present invention, a plurality of optical fiber lines can be monitored in a short time.

1 is a configuration diagram of an optical line monitoring system 1 according to the present embodiment. It is a lineblock diagram of optical line monitoring system 1A concerning this embodiment. It is a block diagram of the reflecting portions 23 _n of the optical line monitoring system 1A according to this embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

FIG. 1 is a configuration diagram of an optical line monitoring system 1 according to the present embodiment. An optical line monitoring system 1 shown in this figure monitors optical fiber lines 30 ₁ to 30 _N laid between a center 10 and facilities 20 _{1 to} 20 _N. Each optical fiber line 30 _n transmits signal light between the transmission device 11 _n in the center 10 and the transmission device 21 _n in the facility 20 _n . N is an integer of 2 or more, and n is an integer of 1 or more and N or less.

The optical line monitoring system 1 includes an optical pulse tester 12, an optical switch 13, a splitter 14, optical couplers 15 ₁ to 15 _N , optical couplers 16 _{1 to} 16 _N , a control unit 17, and reflection units 22 _{1 to} 22 _N. Among these, the optical pulse tester 12, the optical switch 13, the splitter 14, the optical couplers 15 ₁ to 15 _N , the optical couplers 16 _{1 to} 16 _N, and the control unit 17 are provided in the center 10. Each reflection part 22 _n is provided on site 20 _n. The splitter 14 and the optical couplers 15 ₁ to 15 _N are preferably integrated as a module 100.

The optical pulse tester 12 outputs pulse test light to be propagated to the optical fiber lines 30 ₁ to 30 _N to the optical switch 13. Further, the optical pulse tester 12 inputs backscattered light generated during propagation of the pulse test light in the optical fiber lines 30 ₁ to 30 _N from the optical switch 13, and is based on the time change of the intensity of the backscattered light. The optical fiber lines 30 ₁ to 30 _N are monitored.

The optical switch 13 has a port P and ports P _{0 to} P _N. The port P is optically connected to one selected from the ports P _{0 to} P _N. The optical switch 13 inputs the pulse test light output from the optical pulse tester 12 to the port P, and outputs the pulse test light from a selected one of the ports P _{0 to} P _N. The optical switch 13 outputs the backscattered light input to the selected one of the ports P _{0 to} P _N from the port P to the optical pulse tester 12.

In the optical switch 13, for example, the end faces of (N + 1) optical fibers arranged in parallel corresponding to the ports P _{0 to} P _N are fixed in the V-groove, and the end face of the optical fiber corresponding to the port P is moved. Possible configuration. In the optical switch 13, the end face of the optical fiber corresponding to the port P faces the end face of any one of the optical fibers selected from (N + 1) optical fibers corresponding to the ports P _{0 to} P _N. Thus, the optical path can be switched.

The splitter 14 receives the pulse test light output from the port P ₀ of the optical switch 13, splits this pulse test light into _N, and outputs it to the optical couplers 15 ₁ to 15 _N. The splitter 14 also receives the backscattered light output from the optical couplers 15 ₁ to 15 _N, and outputs the backscattered light to the port P ₀ of the optical switch 13.

Each of the optical couplers 15 _n includes any one of the n-th branch pulse test light out of the light that is output after the pulse test light is N-branched by the splitter 14 and the pulse test light output from the port P _n of the optical switch 13. or the outputs to the optical coupler 16 _n. Each optical coupler 15 _n receives the backscattered light output from the optical coupler 16 _n and outputs this backscattered light to the splitter 14 and the port P _{n of the} optical switch 13.

Each optical coupler 16 _n inputs the pulse test light outputted from the optical coupler 15 _n, to propagate this pulse test light to the optical fiber line 30 _n. Further, each of the optical coupler 16 _n, enter the backscattered light generated in the optical fiber line 30 _n, and outputs the backward scattered light to the optical coupler 15 _n.

The optical coupler 15 _n and the optical coupler 16 _n include the n-th branch pulse test light out of the light that is output after the pulse test light is branched N times by the splitter 14, and the pulse output from the port P _n of the optical switch 13. An optical coupling unit for propagating any one of the test lights to the optical fiber line 30 _n is configured.

The control unit 17 controls operations of the optical pulse tester 12 and the optical switch 13. That is, the control unit 17 controls the output of the pulse test light from the optical pulse tester 12 and acquires the monitoring result of the backscattered light by the optical pulse tester 12. The control unit 17 selects any one of the ports P _{0 to} P _N in the optical switch 13 and optically connects the selected port and the port P.

Each reflector 22 _n is provided at the far end of the optical fiber line 30 _n , that is, immediately before the transmission device 21 _n . The reflectors 22 _{1 to} 22 _N are arranged so that the optical path lengths between the respective installation positions and the optical pulse tester 12 are different from each other. Each reflector 22 _n reflects the pulse test light and transmits the signal light. Each of the reflection portions 22 _n preferably has an optical fiber Bragg grating (e.g., an optical fiber Bragg grating) that makes it easy to reflect test light significantly higher than Fresnel reflection (reflection loss of about 14.7 dB) caused by breakage (disconnection) of the optical fiber line. FBG), dielectric multilayer filter and the like.

The optical line monitoring system 1 according to the present embodiment operates as follows when the pulse test light input to the port P by the optical switch 13 is selectively output from the port P ₀ to the splitter 14. The pulse test light output from the optical pulse tester 12 is input to the splitter 14 via the port P and the port P ₀ of the optical switch 13, and is branched into N by the splitter 14. The n-th branch pulse test light output after being branched N by the splitter 14 is introduced into the optical fiber line 30 _n via the optical coupler 15 _n and the optical coupler 16 _n , and this optical fiber line 30 _n is directed to the facility 20 _n . Propagate.

Backscattered light generated during the propagation of the pulse test light in the optical fiber line 30 _n is the optical fiber line 30 _n propagates toward the optical coupler 16 _n, the optical coupler 16 _n, the optical coupler 15 _n, the splitter 14 and the light The signal is input to the optical pulse tester 12 through the switch 13. Backscattered light generated in each of the optical fiber lines 30 ₁ to 30 _N is input to the optical pulse tester 12. In the optical pulse tester 12, the optical fiber lines 30 ₁ to 30 _N are monitored based on the temporal change in the intensity of the input backscattered light.

In this monitoring, the intensity of the backscattered light generated by the reflection of the pulse test light at the reflecting portion 22 _n provided at the far end of each optical fiber line 30 _n is used. Here, since the reflection units 22 _{1 to} 22 _N are arranged so that the optical path lengths between the respective installation positions and the optical pulse tester 12 are different from each other, the input backscattering is performed in the optical pulse tester 12. it is possible to identify the backscattered light generated by the reflection portion 22 _n of the light.

If the intensity of the backscattered light generated by the reflection portion 22 _n is within the predetermined range, the optical fiber line 30 _n and the reflected portion 22 _n is provided is determined to be good. Conversely, If the intensity of the backscattered light generated by the reflection portion 22 _n is smaller than the predetermined value, the optical fiber line 30 _n and the reflected portion 22 _n is provided there is failure locations such as disconnection or loss increase It is judged. Incidentally, if the reflectance of the reflection portion 22 _n is larger than the Fresnel reflectivity at the optical fiber end face, by the reflectance of the test light from the reflecting portion near monitors whether it is below the Fresnel reflectance, optical fiber it becomes possible to determine the disconnection caused in the vicinity of the far end of the line 30 _n.

In order to make such a determination possible, the number of event dead thorns is reduced (that is, the reflection at each of the _N reflecting portions 22 _{1 to} 22 _N can be mutually decomposed in the optical pulse tester 12). It is necessary to measure with the pulse width of the pulse test light as small as possible. However, in this case, since the light quantity of the pulsed test light decreases qualitatively, backscattered light on the optical fiber line 30 _n, the level is a waveform buried in noise down (i.e., high in the noise It becomes a waveform where each peak of reflection stands.) Even if an abnormality occurs in the optical fiber line 30 _n , the waveform of the backscattered light observed by the optical pulse tester 12 is buried in noise, so the anomalous location is not known.

That is, OTDR has a resolution (sampling resolution, event dead zone) according to measurement conditions. When a plurality of far ends are located at a distance less than the resolution, each reflection cannot be resolved by OTDR and is measured as a single reflection. In this case, even if one optical fiber line abnormality occurs far end 30 _n is lost, since reflection at the far end of the other optical fiber line in resolution occurs, the optical fiber line It becomes difficult to detect an abnormality of 30 _n . For this reason, it is necessary that each of the reflecting portions 22 _{1 to} 22 _N be located at a distance greater than the resolution. For example, when the collective simple measurement is performed under the conditions of a 25 km range, 25000 point sampling, and a pulse width of 10 nsec, each of the reflectors 22 _{1 to} 22 _N needs a distance difference of about 3 to 4 m.

The optical line monitoring system 1 according to this embodiment can collectively monitor the optical fiber lines 30 ₁ to 30 _N by operating as described above. However, even if the optical line monitoring system 1 can determine that any one of the optical fiber lines 30 ₁ to 30 _N is out of _order , the optical line 30 _n is out of _order . The position cannot be determined.

Therefore, when the optical line monitoring system 1 determines that any one of the optical fiber lines 30 _n is faulty, the optical coupler 15 selectively selects the pulse test light input to the port P by the optical switch 13 from the port P _{n. The} following operation is performed by outputting to _n .

The pulse test light output from the optical pulse tester 12 is introduced into only the optical fiber line 30 _n through the port P and the port P _n of the optical switch 13 and further through the optical coupler 15 _n and the optical coupler 16 _n. an optical fiber line 30 _n propagates toward the facility 20 _n.

Backscattered light generated during the propagation of the OTDR light at the n optical fiber line 30 _n is the optical fiber line 30 _n propagates toward the optical coupler 16 _n, the optical coupler 16 _n, the optical coupler 15 _n, the splitter 14 And input to the optical pulse tester 12 through the optical switch 13. The optical pulse tester 12 receives backscattered light generated only by the optical fiber line 30 _n . In the optical pulse tester 12, only the optical fiber line _30n is monitored based on the temporal change in the intensity of the input backscattered light.

In this monitoring, the optical line monitoring system 1 can monitor only a specific optical fiber line 30 _n and monitor the backscattered light generated at each position of the optical fiber line 30 _n by the optical pulse tester 12. since it is possible to determine the fault position in the optical fiber line 30 _n.

As described above, the optical line monitoring system 1 according to the present embodiment selectively outputs the pulse test light input to the port P by the optical switch 13 from the port P ₀ to the splitter 14, thereby enabling the optical fiber line 30 _1. ˜30 _N can be easily monitored collectively, and the optical fiber line 30 _{n in} which the failure has occurred can be specified. Further, the optical line monitoring system 1 according to this embodiment, selected when any of the optical fiber line 30 _n is determined that the failure, the pulse test light optical switch 13 is input to the port P from a port P _n Therefore, the failure position in the specified optical fiber line 30 _n can be determined by outputting to the optical coupler 15 _n . Therefore, the optical line monitoring system 1 according to the present embodiment can monitor a plurality of optical fiber lines in a short time.

Next, a configuration of a modified example of the optical line monitoring system 1 according to the present embodiment will be described. FIG. 2 is a configuration diagram of the optical line monitoring system 1A according to the present embodiment. An optical line monitoring system 1A shown in this figure monitors optical fiber lines 30 ₁ to 30 _N laid between a center 10 and facilities 20 _{1 to} 20 _N. However, in this modification, each optical fiber line 30 _n is a so-called air core, and is not connected to a transmission device in the center 10 and is not connected to a transmission device in the facility 20 _n . N is an integer of 2 or more, and n is an integer of 1 or more and N or less. Conventionally, even when monitoring such an air core wire, it was necessary to install an expensive reflection filter having a function of reflecting the test light and transmitting the signal light at the far end of the optical fiber line. .

The optical line monitoring system 1A includes an optical pulse tester 12, an optical switch 13, a splitter 14, optical couplers 15 ₁ to 15 _N , a control unit 17, and reflection units 23 ₁ to 23 _N. Among these, the optical pulse tester 12, the optical switch 13, the splitter 14, the optical couplers 15 ₁ to 15 _N, and the control unit 17 are provided in the center 10. Each reflection part 23 _n are provided on site 20 _n.

In this modification, the optical couplers 16 _{1 to} 16 _N are not provided. An optical coupler 15 _n is connected to one end of each optical fiber line 30 _n . The optical coupler 15 _n is one of the n-th branch pulse test light out of the light that is output after the pulse test light is N-branched by the splitter 14 and the pulse test light output from the port P _n of the optical switch 13. the constitute an optical coupling portion to propagate to the optical fiber line 30 _n.

Each reflecting portion 23 _n is provided at the far end of the optical fiber line 30 _n . The reflectors 23 ₁ to 23 _N are arranged such that the optical path lengths between the respective installation positions and the optical pulse tester 12 are different from each other. Each reflector 23 _n reflects the pulse test light. Each reflection portion 23 _n may be an optical fiber Bragg grating filter or a dielectric multilayer filter. However, in this modification, since each optical fiber line _30n is an air core and does not propagate signal light, the reflectance is not only for test light but also for light that should be signal light like a simple mirror. A high configuration may be used as each reflecting portion 23 _n .

The optical line monitoring system 1A shown in FIG. 2 operates in substantially the same manner as the optical line monitoring system 1 shown in FIG. That is, the optical line monitoring system 1A simplifies the optical fiber lines 30 ₁ to 30 _N collectively by selectively outputting the pulse test light input to the port P by the optical switch 13 to the splitter 14 from the port P _0. The optical fiber line 30 _{n in} which a failure has occurred can be identified. In addition, when the optical line monitoring system 1A determines that any one of the optical fiber lines _30n has a failure, the optical coupler 15 selectively selects the pulse test light input to the port P by the optical switch 13 from the port _{Pn. By} outputting to _n, the failure position in the specified optical fiber line 30 _n can be determined. Therefore, the optical line monitoring system 1A can monitor a plurality of optical fiber lines in a short time.

FIG. 3 is a configuration diagram of each reflector 23 _n in the optical line monitoring system 1A according to the present embodiment. The reflection unit 23 _n includes an optical coupler 24, an optical fiber 25, and an optical fiber 26. The optical coupler 24 has a first port _{P A,} a second port _{P B} and the third port _{P C.} The first port P _A of the optical coupler 24 is connected to the far end of the optical fiber line 30 _n via the optical fiber 25. The optical coupler 24, the light input to the first port P _A second output from the port P _B to the optical fiber 26, the light from the optical fiber 26 is input to the third port P _C from the first port P _A Output. Optical fiber 26 has a loop line which connects between the second port P _B and the third port P _C of the optical coupler 24 optically.

The reflection portion 23 _n configured as described above can achieve high reflection with a return loss of about 3 dB, and can achieve the purpose of high reflection simply and at low cost. Further, unlike the filter, the reflection unit 23 _n does not depend on the wavelength, so that the present monitoring method can be realized by using the existing OTDR and using the wavelength specification of the OTDR.

1, 1A ... optical line monitoring system, 10 ... center, ₁₁ 1 to 11 N _... transmission device, 12 ... OTDR, 13 ... optical switch, 14 ... splitter, ₁₅ 1 to 15 N _... optical coupler ₁₆ 1 - 16 _N : optical coupler, 17: control unit, 20 _{1 to} 20 _N ... facility, 21 _{1 to} 21 _N ... transmission device, 22 _{1 to} 22 _N ... reflection unit, 23 ₁ to 23 _N ... reflection unit, 30 ₁ to 30 _N : Optical fiber line.

Claims (2)

In this system, pulse test light is propagated to each of N optical fiber lines, and the N optical fiber lines are monitored based on temporal changes in the intensity of backscattered light generated during propagation of the pulse test light. And
An optical pulse tester that outputs the pulse test light and inputs the backscattered light to detect a temporal change in the intensity of the backscattered light;
The port P and the ports P _{0 to} P _N , the pulse test light output from the optical pulse tester is input to the port P, and a selected one of the ports P _{0 to} P _N An optical switch for outputting the pulse test light from:
A splitter for inputting the pulse test light output from the port P _{0 of the} optical switch and outputting the pulse test light by N-branching;
Any one of the n-th branch pulse test light out of the light output after the pulse test light is N-branched by the splitter and the pulse test light output from the port P _{n of the} optical switch, An optical coupling portion that propagates to the nth optical fiber line of the optical fiber lines;
A reflection unit provided in each of the N optical fiber lines, the optical path lengths between the installation position and the optical pulse tester are different from each other, and the reflection unit reflects the pulse test light;
With
The optical pulse tester, the optical switch, the splitter and the optical coupling unit are provided in the center,
When the pulsed test light input to the port P is selectively output from the port P ₀ by the optical switch, reflection at each of the reflection portions provided in each of the N optical fiber lines is reflected by the light. The pulse test light is reduced in width so that it can be mutually decomposed in the pulse tester, and the pulse test light is transferred from the port P _{0 of the} optical switch to the N optical fiber lines via the splitter and the optical coupling unit. Light is propagated, and the backscattered light generated in the N optical fiber lines is input to the optical pulse tester through the optical coupling unit, the splitter, and the optical switch. Based on the change, the N optical fiber lines are collectively monitored,
When it is determined by the collective monitoring that a failure has occurred in any of the n-th optical fiber lines based on the intensity of the backscattered light generated in the reflector provided in each of the N optical fiber lines, selectively outputting the pulse test light which the optical switch is input to the port P from the port P _n, the pulse through the optical coupling portion from said port P _n of the optical switch in the n-th optical fiber line The test light is propagated, and the backscattered light generated in the nth optical fiber line is input to the optical pulse tester through the optical coupling unit and the optical switch, and based on the time change of the intensity of the backscattered light. Individually monitoring the nth optical fiber line,
An optical line monitoring system (where N is an integer of 2 or more and n is an integer of 1 to N). The reflective portion is
A first port, a second port, and a third port are provided at the far end of any one of the N optical fiber lines, and the first port is connected to the far end of the optical fiber line. An optical coupler that outputs light input to the first port from the second port and outputs light input to the third port from the first port;
An optical waveguide that optically connects between the second port and the third port of the optical coupler;
The optical line monitoring system according to claim 1, comprising:

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