JPS6344142A - Monitoring of immersion for optical fiber cable - Google Patents

Abstract

PURPOSE:To achieve the efficiency of searching work, by inserting a light testing circuit containing a light wavelength filter for reflecting or transmitting a specified optical pulse signal alone into an optical fiber core at a connection where an optical fiber cable is branched off to measure a reflection waveform. CONSTITUTION:When an optical fiber cable 13 is searched, a light test pulse with the wavelength lambda1 is used. This pulse is sent out to an optical fiber core 20 from an optical main distributing board 50 and enters a light testing circuit 71 in an optical fiber branch section 41. A light wavelength filter 81 in the circuit 71 totally reflects light with the wavelength lambda1 while transmitting lights with other wavelengths lambda2 and lambda3 to be propagated to an optical fiber core 23. A back scattered light of a light test pulse is inputted reversely into a optical pulse tester 60 via the core 23, the circuit 71 and the core 20. Now when light loss of a water infiltration detecting sensor 33 increases by several dB with the filtration of water at a connection of the optical fiber, the detection of the filtration point is made possible depending on an input waveform of the tester 60. Likewise, an optical test with the wavelength lambda2 is used in the searching of the optical fiber cable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides for a subscriber optical line or a relay optical line,
The present invention relates to a method of monitoring water intrusion in an optical fiber cable when the optical fiber cable is branched.

(Prior art) As a method for monitoring water intrusion into optical fiber cables, 65051/c is installed inside optical fiber cables as a preventive maintenance measure.
There are two methods: one is to enclose dry air (A gas), and the other is to install a water intrusion detection sensor at the connection point of the optical fiber cable to monitor water intrusion.

Figure 2 shows the use of a water intrusion detection sensor to monitor water intrusion into the connection point of an optical fiber cable when A gas is not sealed.
FIG. 2 is a configuration diagram of a conventional method. Here, 10.11,12
, 13.14 is optical fiber cable, 20.21.22
．． 23.24 is optical fiber core wire, 30.31, 32, 3
3.34゜35.36.37.38.39 is the water intrusion detection sensor weight, 41.42 is the branch part of the optical fiber cable,
50 is a main wiring device (optical MDF), and 60 is an optical pulse tester (0TDR).

For example, when the optical fiber cable 10 is flooded, the optical loss at the flooded location locally increases by several dB due to the operation of the flood detection sensor 30 installed inside the cable.
The optical pulse tester 60 can detect flooded areas. The structure of the water immersion detection sensors 32 to 39 is shown in FIG. 8(^)(B). The fiber yarn 1, which contracts when it comes into contact with the optical fiber, is hung on the optical fiber (FIG. 8(A)). When this pin 1 comes into contact with water, the thread 1 contracts and the optical fiber cores 20 to 24 are sharply bent (FIG. 8 FB)), causing a sudden increase in transmission loss. : Measurement of flooded areas is possible. As shown in FIG. 9, the transmission loss of the optical fiber increases rapidly as the amount of displacement increases.

When one fiber optic cable 10 branches into an optical cable 13.14 at a branch portion 41.degree. 42, water intrusion detection sensors 32, 33, 36.degree. It is necessary to use one optical fiber core 123, 24 for each period.

The search for a flooded area is performed by receiving backscattered light in the optical fiber generated by the optical test pulse of the optical pulse test: tomoe 60 from the optical distribution board 50 in the station, using the optical pulse tester 60.

FIG. 7 shows an example of receiving backscattered light. As shown in the figure, the receiving level decreases discontinuously at J3 at the submergence point or optical fiber breakage point, so the submergence point or breakage point of the optical fiber cable can be detected from the fluctuation ω of the reception level.

(Problems to be Solved by the Invention) However, such conventional methods have the following drawbacks.

■ When branching optical fiber cables, one optical fiber core is required for each branching optical fiber cable.

(2) When conducting an optical pulse test for each branched optical fiber cable, it is necessary to change connections each time using an optical connector at the seller distribution board 50 in the station. As a result, there is a need for a lot of reconnection work, and the optical connector is likely to become dirty or scratched, and a new optical fiber core wire is likely to be formed at the optical connector.

(Objective of the Invention) An object of the present invention is to solve the problem that when searching for flooded areas using optical fibers, the number of optical fibers for measurement increases by the number of branches in the optical path where there are branches, The object is to be able to carry out the measurement using a single optical fiber for measurement and to improve the efficiency of the search work.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides an optical fiber core line at a connection point where an optical fiber cable branches in a subscriber optical line or a relay optical line using an optical fiber cable. An optical test circuit containing a built-in optical wavelength filter that reflects or transmits only optical pulse signals of specific wavelengths was inserted to measure the reflected waveform.

(Function) According to the present invention, since the optical wavelength filter in each test circuit reflects light of a certain wavelength and transmits light of another wavelength,
Optical pulse signals can be sent to each of the branched optical fibers.

(Embodiment) FIG. 1 is a system configuration diagram illustrating an embodiment of the present invention, and the same components as in the conventional example are represented by the same symbols.

In other words, 10, 11, 12, 13, 14 are optical fiber cables, 20, 21, 22, 23, 24 are optical fiber core wires, 30, 31, 32, 33, 34, 35, 36, 37
, 38, 39 are water immersion detection sensors, 41, 42 are optical fiber cable branch parts, 504 are seller distribution boards, 60 are optical pulse testers, and 71, 72 are optical test circuits.

Optical test circuits 71 and 72 having filters that reflect or transmit optical test pulses are inserted into the branch portions of the optical fibers.

FIGS. 3 and 4 show the configurations of the optical test circuits 71 and 72. The optical test circuits 71 and 72 include a branch circuit 92 formed of a quartz waveguide on an 81 substrate 91, and a 5i layer of 20 or more layers.
02 ・l"iQ2 It is constructed by combining four long wavelength passing optical wavelength filters 81 and 82 of alternating multilayer pattern. Figure 5 shows the characteristics of the optical wavelength filter 81, and Figure 6 shows the characteristics of the optical wavelength filter 82. Show each.

Next, regarding the monitoring method according to the present invention).

When searching the optical fiber cable 13, an optical test pulse of wavelength λ1 is used. The test pulse 21 is sent from the main distribution board 5 to the optical fiber core 20, and is sent to the optical fiber branch 4.
The optical test circuit 71 is located in the optical test circuit 1. Optical test circuit 7
The optical wavelength filter 81 in 1 has a wavelength λ1 as shown in FIG.
, and other wavelengths λ2. Since the configuration allows light of λ3 to pass through, it propagates to the optical fiber core wire 23. The backscattered light of the optical test pulse is conversely transmitted to the optical fiber core 23,
Optical test circuit 71. The signal is input to the optical pulse tester 60 via the optical fiber core 20.

Now, if there is water intrusion at the connection point of the optical fiber and the optical loss of the water inundation detection sensor 33 increases by several dB, the optical pulse tester 60
The input waveform becomes as shown in Fig. 7, and it is possible to detect a flooded area.

Similarly, the optical fiber cable 14 is searched using an optical test pulse of wavelength λ2, but the filter 82 in the test circuit 72 installed in the branch section 42 detects the light of wavelength λ2 as shown in FIG. Since the configuration is such that the light with the wavelength λ3 is reflected and the light with the other wavelength λ3 is transmitted, the optical test pulse with the wavelength λ2 propagates to the optical fiber core wire 24 and detects an abnormality in the θ water detection sensors 36 and 37.

J3, the test light wavelengths are currently considered to be the wavelengths (0.85 μm, 1.2 μm, 13 μm) of commercially available color optical pulse testers.

(Effects of the Invention) As explained above, according to the present invention, when searching for flooded areas using optical fibers, the number of branches and optical fibers are not required in conventional optical paths with branches. However, by inserting an optical test circuit into the optical fiber core of the branching contact point and changing the wavelength of the optical test pulse, there is an advantage that it is possible to search for flooded areas using a single optical fiber core. In addition, there is no need to change the optical connector connection at the main distribution board.
This has the advantage of not only increasing the efficiency of the search work but also preventing stains or scratches on the optical connector.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a system for explaining the present invention in detail, Fig. 2 is a block diagram of a conventional system for monitoring water intrusion into the connection point A of an optical fiber cable, and Figs. 3 and 4 are diagrams of a system according to the present invention. A configuration diagram of the optical test circuit used. Figures 5 and 6 do not show characteristic examples of the optical wavelength filter used in the test circuit. Figure 7 is an example 3 of reception of t9 direction scattered light by an optical pulse tester. Figure 8
Figure (^) 1 is a structural diagram of a water immersion detection sensor, Figure (B) is a diagram for explaining the operation, and Figure 9 is a diagram showing the relationship between the amount of displacement of the optical fiber and the increase in loss. 10.11, 12, 13.14... Optical fiber cable, 20.21, 22.23.24... Optical fiber core wire, 30.31.32.33.34.35° 36.37
... Water immersion detection sensor, 41.42 ... Branch part of optical fiber couple, 50 ... Main distribution board (optical MDF)
, 60... Optical pulse tester, 71° 72... Optical test circuit, 81.82... Optical wavelength filter.

Claims (1)

[Claims] In subscriber optical lines or relay optical lines using optical fiber cables, optical fibers at the connection points where optical fiber cables branch have a built-in optical wavelength filter that reflects or transmits only optical pulse signals of specific wavelengths. A method for monitoring flooding of optical fiber cables, which comprises inserting a test circuit and measuring reflected waveforms.