JPH02232548A - Water infiltration detection sensor in closure - Google Patents

Abstract

PURPOSE:To enable detection of water infiltration in a closure accurately by a method wherein a float floats with an infiltration of water in the closure to pull up an optical fiber. CONSTITUTION:An optical fiber 1 is fixed at two points on a substrate 2 by a disc-shaped fixing devices 3 with a periphery thereof pressed onto the fiber 1 and the fiber 1 is given a margin between the fixing devices 3. A disc-shaped changer 4 is mounted movably at the optical fiber part and a float 5 is linked to the hanger 4. A base body of a water infiltration detecting sensor is fastened on a floor within a closure 8 in which a connection part 7 of an optical fiber cable 6 is housed. When a water infiltration occurs in the closure 8, the float 5 floats and a tension is applied on the fiber 1 between fixing devices 3 so that the fiber 1 comes in contact with the two fixing devices 3 and the hanger 4 to form a bending with a specified curvature. A light transmitter/receiver is mounted at an end of the fiber 1 to measure a light loss caused by the bending of the fiber 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water immersion detection sensor within a closure in which an optical cable connection section is housed. [Conventional technology and its iI!
Problem] When water enters the closure that houses the optical cable connection, water enters the optical fiber connection and deteriorates the optical fiber, impairing the reliability of optical communications. For this reason, various methods of detecting water intrusion inside the closure have been studied. An optical fiber is wired to the substrate, and a plate-like body that grows a convex portion of a predetermined curvature is placed above the plate-like body with the convex portion facing downward. A method has been proposed for detecting water intrusion by measuring the optical loss or loss in which an optical fiber is pressed against the convex part of the plate-shaped body and bent at a predetermined curvature. However, with this method, the degree of swelling of the swollen body varies greatly depending on the ion concentration of the water in which it is immersed, so errors in detecting water intrusion are likely to occur, resulting in a lack of reliability. [Means for Solving the Problem] The present invention was made in view of the above situation, and its purpose is to provide a sensor for detecting water intrusion inside a closure that can reliably detect water intrusion inside a closure. be. That is, in the present invention, an optical fiber of a desired length is mounted on a substrate by a fixture having a predetermined curvature on the surface in contact with the optical fiber.
At this point, fix the optical fiber between the above-mentioned fixtures with a predetermined extra length, and attach a float to the optical fiber between the above-mentioned fixtures via a hanging fixture with a predetermined curvature on the surface that contacts the optical fiber. In the water immersion detection sensor, the base body of the sensor is disposed on the floor inside the closure, the float floats up due to water intrusion inside the closure and pulls up the optical fiber, and the optical fiber is connected to the two fixing tools described above. and close to the sling,
This system is characterized in that the optical fiber is bent to a predetermined curvature, and the light loss due to the bending of the optical fiber is measured to detect water intrusion inside the closure. The configuration of the present invention will be explained below with reference to the drawings. FIG. 1A is a perspective explanatory view showing an embodiment of the water immersion detection sensor of the present invention. In the figure, 1 is an optical fiber, and 2 is a base body to which the optical fiber 1 is fixed. The water immersion detection sensor of the present invention, as shown in Fig. 1A,
The optical fiber 1 is fixed on the base 2 by a disk-shaped fixture 3 at two locations by pressing its peripheral edge against the optical fiber, and a predetermined extra length is provided for the optical fiber 1 between the fixtures 3. ,
A disc-shaped hanging tool 4 is movably attached to the optical fiber portion having a predetermined extra length, and a float 5 is connected to the hanging tool 4. In the figure, the base of the water immersion detection sensor is fixed on the floor inside the closure 8 in which the connection part 7 of the optical cable 6 is housed.
This is a diagram showing a state in which water has entered the closure 8. The float 5 floats up, which applies tension to the optical fiber 1 between the fixtures 3, and the optical fiber 1 is connected to the two fixtures 3 and the hanging fixture 4. A bend of a predetermined curvature is formed in the optical fiber 1 in close proximity to the . An optical transmitter/receiver such as an OTDR is attached to the terminal of the optical fiber 1, and the optical loss caused by bending the optical fiber 1 is measured. In the present invention, the extra length of the optical fiber between the fixtures is
It is set based on the permissible flooding value; for example, when detecting flooding at a shallow point, the extra length should be set short. It is preferable to use a disc body as the fixture or hanging fixture so that the periphery of the disc body is in contact with the optical fiber. The smaller the curvature of the surface of the fixture or hanger in contact with the optical fiber, and the narrower the distance between the fixtures, the smaller the bending that occurs in the optical fiber, and as a result, the amount of optical loss increases and the measurement sensitivity improves. ．． Plastics such as styrofoam, which are lightweight and have excellent water resistance, are mainly used for floats, but materials such as wood can also be used. Instead of using a hanging tool to connect the optical fiber to the float, a thick insertion hole may be provided in the float and the optical fiber may be passed directly through this insertion hole. Further, a member for fixing the optical fiber on the base body and a bending member for forming a predetermined curvature on the optical fiber may be provided separately. In the present invention, the water immersion detection sensor is constructed on a base body, but this base body may be a simple plate-like body, for example, the floor of a container having a water entry hole at least in the lower part, or the floor of a closure. (Function) In the water immersion detection sensor of the present invention, optical fibers are fixed at two locations on the base, an extra length is provided for the optical fiber in the fixed section, a float is attached to the optical fiber in this fixed section, and the float is Water intrusion is detected by floating and forming a bend in the optical fiber with a predetermined curvature and measuring the loss of light caused by this bending, so water intrusion can be reliably detected without being affected by water quality. [Example] Below The present invention will be explained in detail with reference to examples.Example 1 The water immersion detection sensor shown in Fig. 1A is connected to an optical cable 6.
We conducted a water intrusion detection experiment by installing the sensor firmly on the floor inside the closure 8 where the connecting part 7 of the sensor was placed. The optical cable connection section 7 is located at a height of 200 m above the inner floor surface of the closure 6, and based on this, the water intrusion detection level was set at a height of about 110 m above the inner floor surface of the closure 8. Based on these settings, the distance between the fixing devices 3 for the optical fibers 1 on the base 2 of the water immersion detection sensor is set to 160 m, and the length of the optical fiber 1 between the fixing devices 3 is set to 260 m, that is, the extra length is set to 100 m. Ta. The base body 2 was made of a 2 m thick plastic plate, and was attached to the inner floor of the closure 8 with bolts. Float 5 was a styrofoam ball with a diameter of 40 mm. The fixing device 3 and the hanging device 4 are plastic disks with a diameter of 4 cm and have mounting rods on both sides. They were installed leaving only the space for the optical fiber l to pass through. The optical fiber I has a mode field diameter of IO, a cutoff wavelength of 1.2 m, a fiber diameter of 125 mm, and a coating outer diameter of 2 mm.
50n is used, and an OTDR is installed at the end of this optical fiber.
was connected, and light with a wavelength of 1.55μ was propagated through this optical fiber I.

When water was poured into closure 8, the water depth was 11.
A light loss of 0.5 dB was measured at a distance of 3 m, and water intrusion was clearly detected. Embodiment 2 In this embodiment, as shown in FIG. 2, an optical fiber 1 with a float 5 attached to the center is placed on the floor of a container 11 having a water entry hole 9 at the bottom and an air vent hole 10 at the top. It is fixed with an extra length between the fixtures 3 using the fixtures 3. This water immersion detection sensor is convenient to carry because the optical fiber I is inside the container 11, so there is no risk of damaging the optical fiber 1. Example 3 In this example, as shown in FIG. 3, a bending member 12 is attached inside a fixture 13 for fixing the optical fiber 1, and the fixing and bending of the optical fiber 1 are performed using separate jigs. With this structure, the curvature and spacing of the fixture l3 can be easily changed. Embodiment 4 In this embodiment, as shown in FIG. 4, a thick optical fiber insertion hole l4 is provided in the float 15, and the optical fiber 1 is directly passed through the insertion hole 14. The optical fiber 1 is bent into a predetermined curvature in close contact with the lower surface of the insertion hole 14. This water immersion detection sensor requires few jigs, so it is economical and has excellent workability. [Effects] The water intrusion detection sensor of the present invention can reliably detect water intrusion inside a closure, regardless of the quality of the water entering, and has a significant industrial effect.

[Brief explanation of the drawing]

FIG. 1 is a perspective explanatory diagram showing a first embodiment of the flood detection sensor of the present invention, and FIGS. 2 to 4 are cross-sectional explanatory diagrams showing second to fourth embodiments of the flood detection sensor of the present invention. be. l...optical fiber, 2...substrate, 3.13
...Fixing device, 4...Hanging device, 5.15...
・Float, 6... Optical cable, 7... Connection part,
8... Closure.

Claims (1)

[Claims] An optical fiber of a desired length is fixed on the base at two locations using fixing devices having a predetermined curvature on the surface in contact with the optical fiber, leaving a predetermined extra length for the optical fiber between the fixing devices. A water immersion detection sensor is a water immersion detection sensor in which a float is attached to an optical fiber between the parts via a hanging device having a predetermined curvature on the surface in contact with the optical fiber, and the base of the sensor is disposed on the floor inside the closure, The float floats up due to water entering the closure, pulls up the optical fiber, brings the optical fiber into close contact with the two fixing tools and the hanging tool, forms a bend of a predetermined curvature in the optical fiber, and A sensor for detecting water intrusion inside a closure, characterized in that water intrusion inside the closure is detected by measuring optical loss due to bending.