JP2008014698A - Monitoring system by otdr - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance reliability of monitoring with simple constitution. <P>SOLUTION: This monitoring system is constituted of an OTDR 1, a plurality of 2×2 couplers 3 connected via an optical fiber 2 of a main line, 2×1 3dB couplers 5 connected to the respective couplers, and a reflection type sensor 4 connected to the respective 3dB couplers, a light pulse from the OTDR 1 is branched by the 2×2 couplers 3 and can reach the reflection type sensor 4 via the 2×1 3dB coupler 5 through a 1-side of the coupler 3, and the light pulse can reach the reflection type sensor 4 via the 2×1 3dB coupler 5 through a 2-side of the coupler 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a monitoring system using OTDR for monitoring rivers and large tanks.

  The conventional OTDR monitoring system shown in FIG. 3 uses sensors 1 (14 a, 14 b, 14 c) using a 1-port input, 2-port output optical coupler 13 from the main optical fiber 12 that is a main line connected to the OTDR 11. It is a configuration for branching light to the) side. An optical pulse (inspection light or test light) emitted from the OTDR 11 to the optical fiber 12 is transmitted to the sensors 14a, 14b, and 14c through the optical coupler 13. The light pulse undergoes intensity modulation depending on the state of the sensor 14, follows the same return path as the forward path, and returns to the OTDR 11.

According to the conventional example, when the optical fiber 12 is cut at the point A shown in FIG. 3, the sensor 14c and the sensors that follow the sensor 14c cannot be monitored. In other words, when the core optical fiber 12 is disconnected, there is a problem that light from the OTDR 11 does not reach the sensors after the disconnection point (in the drawing, the sensor 14c and the sensors that follow the sensor 14) and cannot be monitored.
In addition, when high reliability is required for the monitoring system, there is an example in which the core optical fiber and the sensor connected to it are doubled, but the configuration is complicated because it requires equipment of a double monitoring system. There was a problem that the monitoring cost increased with the time.
An object of the present invention is to improve monitoring reliability with a simple configuration.

In this invention, when the backbone optical fiber is disconnected, the sensors after the disconnection point can be monitored by putting light from the opposite side of the backbone optical fiber, so that the monitoring can be continued. Equipment costs can be saved and monitoring reliability can be improved.
According to a first aspect of the present invention, there is provided an OTDR, a backbone optical fiber connected to the OTDR and forming a loop, and a plurality of first branch portions connected via the backbone optical fiber. Each of the first branch portions is composed of a second branch portion connected to each of the first branch portions, and a reflection type sensor connected to each of the second branch portions, and the optical pulse from the OTDR is Branched by each first branching section, can pass through one side of the first branching section and reach the reflection type sensor via the second branching section, and the light pulse can be passed through the first branching section. It is possible to reach the reflection type sensor through the second branch portion through the two sides of the portion.
The second feature of the present invention is based on the first feature. The loop in the backbone optical fiber is composed of a left route and a right route, and the first branch portion is located on either the left route or the right route. It is located at the root.
A third feature of the present invention is based on the premise of the first or second feature, wherein the first branching unit is a 2 × 2 coupler and the second branching unit is a 2 × 1 3 dB coupler. It is in.

  According to the present invention, even when the main optical fiber is disconnected, monitoring of all the sensors can be continued by monitoring the sensors from the reverse direction, so that the reliability of the monitoring system is improved with a simple configuration.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
The monitoring system shown in FIG. 1 includes an OTDR (Optical Time Domain Reflectometer) 1, a backbone optical fiber 2 connected to the OTDR and forming a loop, and the backbone optical fiber. A plurality of first branch portions 3, a second branch portion 5 connected to each first branch portion, and a plurality of reflective sensors 4 a respectively connected to each second branch portion 5. , 4b, 4c.
The loop in the basic optical fiber 2 includes a left route 2a and a right route 2b. Each of the first branch portions 3 is arranged on the left route 2 a in the optical fiber 2. Each of the reflective sensors 4a, 4b, 4c is installed on a river bank, a large tank, or the like to be monitored.
Note that “4” is used as necessary for the reference numerals when collectively referring to the reflective sensors 4a, 4b, and 4c.

In FIG. 2 showing the basic connection configuration of the reflective sensor 4, a 2 × 2 coupler having a branch ratio of 1 to 10% is used as the first branch portion 3, and 2 × 1 is used as the second branch portion 5. A 3 dB coupler is used, and the reflective sensor is connected to one port side of the second branch section 5.
In FIG. 1, when the reflective sensor 4 (4 a, 4 b, 4 c) is monitored through the left route 2 a of the basic optical fiber 2, the light pulse (inspection light or test light) from the OTDR is transmitted by the first branching unit 3. The light is branched at a predetermined branching ratio, passes through one side (the right side in the figure), and reaches the reflective sensor 4 via the second branching portion 5. On the contrary, when the reflective sensor 4 is monitored from the right route 2b of the basic optical fiber 2, the optical pulse is branched by the first branching section 3, and passes through the second branching section 5 through the two sides (left side in the figure). It reaches the reflection type sensor 4 via.
In FIG. 1, 6 is an optical switch which is an optical coupling part.

When the optical fiber 2 is cut at the point A shown in FIG. 1, a sensor after the disconnection point (sensor 4c and the sensor 4c in the figure) is entered by inserting light from the opposite side of the main optical fiber (right route 2b) through the optical switch 6. Since the monitoring of the subsequent sensors) can be continued, the monitoring of all the sensors 4 can be continued even when the basic optical fiber is disconnected.
Therefore, by adopting such a basic connection configuration of the reflection type sensor 4 in the monitoring system based on OTDR, each of the reflection type sensors 4a, 4b, and 4c can be routed from either the left or right route of the backbone optical fiber 2. Can also be monitored, increasing the reliability of monitoring.

It is a block diagram which shows the monitoring system by OTDR which concerns on this invention. It is a block diagram which expands and shows the basic connection of the sensor used for the monitoring system by OTDR which concerns on this invention. It is a block diagram which shows the monitoring system by the conventional OTDR.

Explanation of symbols

1 OTDR
2 Basic optical fiber 2a Left route 2b Right route 3 First branch (2 × 2 coupler)
4, 4a, 4b, 4c Reflective sensor 5 Second branch (2 × 1 3 dB coupler)

Claims (3)

OTDR, a backbone optical fiber connected to the OTDR and forming a loop, a plurality of first branch portions connected via the backbone optical fiber, and a first branch portion, respectively. It is composed of a connected second branch part and a reflective sensor connected to each second branch part,
The optical pulse from the OTDR is branched by the first branch portions, can pass through one side of the first branch portion, and reach the reflective sensor via the second branch portion. An OTDR monitoring system, wherein an optical pulse can pass through two sides of the first branching section and reach the reflective sensor via the second branching section.   2. The OTDR according to claim 1, wherein the loop in the backbone optical fiber is composed of a left route and a right route, and the first branch portion is arranged in one of the left route and the right route. Monitoring system.   3. The OTDR monitoring system according to claim 1, wherein the first branching unit is a 2 × 2 coupler, and the second branching unit is a 2 × 1 3 dB coupler.

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