JP2008032592A - Optical fiber air route surveillance system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber air route surveillance system for clearly obtaining distance information of positions of all optical fiber fusion connection points. <P>SOLUTION: The optical fiber air route surveillance system discriminates the position of a light loss part by forming the light loss part generating light loss of a prescribed value in an optical fiber for surveillance composing an optical fiber air route at a prescribed part of the optical fiber air route. A plurality of closure components are successively arranged at the prescribed part of the optical fiber air route, and the light loss part generating the light loss of the prescribed value is formed in the optical fiber for surveillance in the closure component to discriminate the position of a closure. The closures are successively arranged at regular intervals, and each of the closures is provided at a connection point of fusion connection of the optical fiber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical fiber route monitoring system using an optical fiber.

  A conventional optical fiber line monitoring system measures the connection loss at the fusion splicing point of the optical fiber in advance with an optical pulse tester (OTDR) and prepares the data. When a failure occurs in the optical fiber transmission line In addition, the position is specified based on the position information of the connection point specified in advance. FIG. 5 shows a fusion splice point of a conventional optical fiber. As shown in FIG. 5, when splicing the monitoring optical fiber cores, a connection point is formed.

  However, the splicing loss is further reduced by the improvement of the fusion splicing technique of the optical fiber, and the splicing loss at the splicing point (ie, appearing as a step in the measured waveform) cannot be detected even when measured by the optical pulse tester (OTDR). There was a place. When the position of the connection point could not be specified by prior measurement, the estimated value with reference to the design length or the like was used, so the data was inaccurate.

FIG. 5 is a diagram for explaining a situation in which the position of the fusion splicing point of the optical fiber provided on the monitoring core is estimated by the optical pulse tester.
As shown in FIG. 5, when a spliced connection point of an optical fiber is provided on the monitoring core and measurement is performed by an optical pulse tester (OTDR), a connection loss appears as a step in the measurement waveform at the connection point. At that time, as described above, there may be a portion where the step of the measurement waveform does not appear.
In this optical fiber route monitoring system, an optical signal is incident from one end of an optical fiber, and an optical signal reflected by the other end of the optical fiber is received by an optical measuring device to detect a measurement waveform.
JP-A-8-75606

  As described above, in the conventional optical fiber route monitoring system, the connection loss at the fusion splice point is reduced by the improvement of the fusion splicing technique of the optical fiber, and even if measured by the optical pulse tester (OTDR) There was a point where the point connection loss (ie, appearing as a step in the measured waveform) could not be detected. When the position of the connection point could not be specified by prior measurement, the estimated value with reference to the design length was used, so the data was inaccurate.

  An object of the present invention is to solve the above-described problems and to provide an optical fiber line monitoring system capable of clearly obtaining the positions of all the optical fiber fusion splicing points.

The present invention has been made based on the above-described research results, and a first aspect of the optical fiber route monitoring system of the present invention includes a monitoring light generator, an optical fiber connected to the monitoring light generator, A light receiver connected to the optical fiber, forming a light loss portion that generates a light loss of a predetermined value at a predetermined location of the optical fiber, and from the monitoring light generator through the optical fiber In the optical fiber route monitoring system, at least one of reflected light or transmitted light of the transmitted monitoring light is measured by the light receiver to identify the position of the optical loss portion.

  A second aspect of the optical fiber route monitoring system according to the present invention is an optical fiber route monitoring system in which the optical loss portion is sequentially formed at a plurality of locations at predetermined intervals.

  A third aspect of the optical fiber route monitoring system according to the present invention is an optical fiber monitoring system in which the optical loss portions are formed at intervals of 1 km.

  According to a fourth aspect of the optical fiber route monitoring system of the present invention, the optical loss unit is an optical fiber route monitoring system in which transmission loss values of the respective optical loss units are different from each other.

  A fifth aspect of the optical fiber route monitoring system of the present invention is an optical fiber route monitoring system formed by fusing and connecting the optical axes of the optical fibers.

  A sixth aspect of the optical fiber route monitoring system of the present invention is an optical fiber route monitoring system formed by a mechanical splice.

  According to a seventh aspect of the optical fiber route monitoring system of the present invention, the optical loss unit is formed by connecting a heterogeneous fiber having an MFD different from that of the optical fiber to the optical fiber located in the optical loss unit. It is an optical fiber route monitoring system.

  An eighth aspect of the optical fiber route monitoring system according to the present invention is an optical fiber route monitoring system in which the heterogeneous fiber is a dispersion shifted fiber (DSF).

  A ninth aspect of the optical fiber route monitoring system according to the present invention is an optical fiber route monitoring system in which the dissimilar fiber is a graded fiber (GIF).

  According to a tenth aspect of the optical fiber route monitoring system of the present invention, the optical loss unit is an optical fiber route monitoring system having a transmission loss value in a range of 0.08 dB to 0.15 dB.

  An eleventh aspect of the optical fiber route monitoring system according to the present invention is an optical fiber route monitoring system in which the wavelength of the monitoring light emitted from the monitoring light generator is 1310 nm, 1550 nm, or 1650 nm.

  A twelfth aspect of the optical fiber route monitoring system according to the present invention is an optical fiber route monitoring system in which a closure part is disposed in the optical loss portion and the position of the closure part is identified.

  According to the optical fiber route monitoring system of the present invention, since a transmission loss part is formed at the fusion splicing point of the optical fiber, the connection loss at the connection point (optical loss part) is measured by the optical pulse tester (OTDR). It appears as a step in the clear measurement waveform. As a result, the position information of the connection point (light loss portion) can be obtained accurately.

  Furthermore, a closure is provided at the splicing point (optical loss part) of the optical fiber, and different optical losses are generated in advance in each optical loss part inside the closure, and the optical loss value is observed. By doing so, the position of the closure can be accurately identified.

Furthermore, according to the optical fiber line monitoring system of the present invention, since the position information of the connection point (light loss portion) can be detected accurately, the abnormal point detection position error due to the non-detection of the connection point can be improved.
When connecting the off-axis attenuator with the local monitoring line, no special work is required.

  Furthermore, according to the optical fiber route monitoring system, a reflector for reflecting an optical signal is provided at one end of at least one optical fiber constituting the optical fiber, and an optical branching device is provided at the other end of the optical fiber provided with the reflector. The optical signal is input from the input device of the optical branching device, and the reflected signal reflected through the optical fiber is measured by the optical measuring device provided at the output end of the optical branching device. Since the reflected light has a sufficiently high signal level, it can be measured even if the accuracy of the optical measuring instrument is not high.

Hereinafter, an optical fiber line monitoring system of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, an optical fiber route monitoring system according to the present invention includes a monitoring light generator, an optical fiber connected to the monitoring light generator, and a light receiving device connected to the optical fiber via a coupler. The optical fiber is formed with an optical loss portion that generates an optical loss of a predetermined value at a predetermined location.

  As shown in FIG. 2, a closure part is disposed in the light loss part as necessary. The light loss portion of the closure part is provided with, for example, an off-axis attenuator that generates a predetermined value of light loss. A plurality of closures formed in advance so as to generate a predetermined value of light loss are arranged at predetermined intervals (see FIG. 1).

Next, an optical loss part is demonstrated.
FIG. 3 shows an example of the optical loss part. At the connection point of the optical fiber, the optical axis is shifted and fused to form an optical loss portion. As a method of fusing by shifting the optical axis, a method using mechanical splice is preferable.

  FIG. 4 shows another example of the optical loss part. The optical loss part is obtained by interposing a different type of fiber having an MFD different from that of the optical fiber for monitoring on the route of the optical fiber for monitoring. It is. Since the MFDs are different, it is possible to generate optical loss even if the optical axes are connected together. Examples of the different types of fibers include DSF (dispersion shifted fiber) and GIF (graded index fiber).

  In any of the optical loss portions of FIGS. 3 and 4, the transmission loss value is preferably a value between 0.08 dB and 0.15 dB. If the transmission loss value to be set is less than 0.08 dB, the optical loss may be too small to clearly identify the position. On the other hand, if the set transmission loss exceeds 0.15 dB, the optical loss is unnecessarily large, which is not preferable.

  In the above-described optical fiber line monitoring system, when the monitoring light emitted from the monitoring light generator enters the optical fiber, it propagates in the length direction of the optical fiber and is lost at each optical loss portion (loss of optical power). Backscattered light is generated toward the monitoring light generator side while generating. A spectrum as shown by a chain line in FIG. 5 can be obtained by measuring the back scattered light by propagating it to a light receiver using a coupler. The optical fiber route monitoring system detects an abnormal point (increased loss, disconnection, etc.) occurring on the optical fiber by using this spectrum as a reference value at normal time, and specifies the position thereof. The wavelength of the monitoring light is not particularly limited, but is preferably 1310 nm, 1550 nm, or 1650 nm.

(Example 1)
Using the optical fiber line monitoring system of the present invention, measurements were performed in combination with the following conditions. The light loss part was formed by off-axis fusion, and the transmission loss value was 0.05 dB to 3.00 dB.
Monitoring route: single mode fiber Monitoring distance: within 400 km (5, 10, 25, 50, 100, 200, 2580, 400 km)
Loss interval: 3 km or less (0.01, 0.05, 0.1, 0.5, 1.0, 2.0, 3.0 km)
Monitoring wavelength: 1310 nm, 1550 nm, 1650 nm
OTDR pulse width: 20 μs or less (10 ns, 30 ns, 100 ns, 300 ns, 1 μs, 3 μs, 10 μs, 20 μs)

  Although OTDR measurement was performed under the above-mentioned conditions, a spectrum as shown by a chain line in FIG. 5 could be obtained under any condition.

(Example 2)
Various optical loss portions that generate optical loss were formed in the monitoring optical fiber in the optical fiber route monitoring system of the present invention, and the characteristics of each optical loss were further investigated.
First, the following sample (single core) was connected in the transmission line and actually measured by OTDR. The connection was measured by connecting the following samples (each optical loss part) between 22 km single mode fibers.

There are the following five types of samples of the optical loss part.
Sample No. 1: 2 m single-mode fiber (ie, off-axis attenuator) including a connection that generates 0.1 dB optical loss at a wavelength of 1550 nm

Sample No. 2: 2 m single-mode fiber (ie, off-axis attenuator) including a connection that generates 0.2 dB of optical loss at a wavelength of 1550 nm
Sample No. 3: 2m dispersion shifted fiber (DSF)
Sample No. 4: 2 m single-mode fiber sample No. 4 containing 30 mm dispersion-shifted fiber (DSF) in the connection. 2m single mode fiber with 5: 30mm graded fiber in the connection

The measurement conditions in this case were as follows.
Distance range: 50km
Pulse width: 500ns
As a result, sample no. It became clear that splice loss can be detected in all of 1 to 5. That is, the above sample No. In all of 1 to 5, it was possible to obtain a spectrum as shown by the chain line in FIG. Sample No. In Nos. 1 and 2, light loss can be clearly detected, and sample Nos. Using different types of fibers are used. In Nos. 3 to 5, sample no. The optical loss value was larger than 1 and 2.

(Example 3)
FIG. 6 is a diagram for explaining an optical fiber route monitoring system according to the present invention. In FIG. 6, 1 is an optical fiber line, and 2 is an optical fiber constituting the optical fiber line 1. A reflector 3 is provided on the optical fiber 2 on one end side of the optical fiber line 1. The reflector 3 is composed of an optical coupler. The optical fiber 2 is connected to one port P1 on the input side of the optical coupler, and the two ports P2 and P3 on the output side are connected to the loop by the optical fiber 4. It functions as the reflector 3.

  An optical coupler 5 is provided in the optical fiber 2 on the other end side of the optical fiber line 1. As shown in FIG. 7, the optical coupler 5 has an optical fiber 6 connected to the light source A connected to one port P4 on the input side. An optical fiber 7 connected to the optical measuring device B is connected to the other port P5 (output side of reflected light) on the input side of the optical coupler 5. The optical coupler 5 is provided with an optical isolator 8 at a port P4 connected to the light source A so as to prevent the reflected return light from returning to the light source A.

  One port P 6 on the output side of the optical coupler 5 is connected to the optical fiber 2. A plurality of off-axis attenuators that generate optical loss are disposed at appropriate intervals in the optical fiber line 1. The off-axis attenuator is disposed in the closure and is formed to generate a predetermined value of optical loss. The closures 10-1, 10-2, 10-3, 10-4,..., 10-n-2, 10-n-1, 10-n having an axial attenuator inside are shown in FIG. As shown, for example, they are arranged every 1 km. Although not shown, a monitoring optical fiber is connected to each closure.

  First, the case where the optical loss in each closure in the optical fiber line 1 is measured will be described. An optical signal from the light source A is input to the optical coupler 5 through the optical fiber 6. The optical signal input to the optical coupler 5 is incident on the optical fiber 2 of the optical fiber line 1 connected to the output side port P 6 of the optical coupler 5, and is transmitted to the reflector 3 provided on the opposite side of the optical fiber line 1. It reaches via the fiber 2. This optical signal is reflected by the reflector 3 (more precisely, looped by the loop optical fiber 4) and returned to the optical fiber 2, and the output side port P6 of the optical coupler 5 via the original optical fiber 2 (reflected return light). The light enters the optical fiber 7 of the input side port P5 of the optical coupler 5 and is input to the optical measuring device B. The measured value of the reflected return light is compared with a preset optical loss value.

It is a figure explaining the optical fiber route monitoring system of this invention. It is a figure explaining the optical loss part of the optical fiber route monitoring system of this invention. It is a figure explaining one Example of a light loss part. It is a figure explaining the other Example of an optical loss part. It is a figure which shows the measurement result by OTDR measurement. It is a figure explaining the other Example of the optical fiber route monitoring system of this invention. It is a figure explaining the detail of an optical coupler. It is a figure explaining an optical loss part.

Explanation of symbols

1 Optical fiber route 2 Optical fiber 3 Reflector 4 Optical fiber (loop)
5 Optical coupler 6, 7 Optical fiber 8 Optical isolator 9 Optical loss part A Light source B Optical measuring device P1, P2, P3 Port P4, P5, P6 port

Claims (12)

A monitoring light generator; an optical fiber connected to the monitoring light generator; and a light receiver connected to the optical fiber, wherein a predetermined value of optical loss is generated at a predetermined position of the optical fiber. An optical loss portion is formed, and at least one of reflected light or transmitted light of the monitoring light propagated from the monitoring light generator through the optical fiber is measured by the light receiver, and the position of the optical loss portion is identified. , Optical fiber route monitoring system. The optical fiber route monitoring system according to claim 1, wherein the optical loss unit is sequentially formed at a plurality of locations at predetermined intervals. The optical fiber monitoring system according to claim 2, wherein the light loss portions are formed at intervals of 1 km. The optical fiber route monitoring system according to claim 2, wherein the optical loss unit has mutually different transmission loss values. 3. The optical fiber route monitoring system according to claim 1, wherein the optical loss unit is formed by shifting the optical axes of the optical fibers and performing fusion connection. 4. The optical fiber line monitoring system according to claim 5, wherein the optical loss portion is formed by a mechanical splice. The optical fiber route monitoring according to claim 1, wherein the optical loss unit is formed by connecting a heterogeneous fiber having an MFD different from the MFD included in the optical fiber to the optical fiber located in the optical loss unit. system. The optical fiber line monitoring system according to claim 7, wherein the heterogeneous fiber is a dispersion shifted fiber (DSF). The optical fiber route monitoring system according to claim 7, wherein the different type fiber is a graded fiber (GIF). The optical fiber route monitoring system according to claim 1 or 2, wherein the optical loss unit has a transmission loss value in a range of 0.08 dB to 0.15 dB. The optical fiber route monitoring system according to claim 1 or 2, wherein the wavelength of the monitoring light emitted from the monitoring light generator is 1310 nm, 1550 nm, or 1650 nm. The optical fiber route monitoring system according to claim 1, wherein a closure component is disposed in the optical loss unit, and a position of the closure component is identified.

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