JPH0725645Y2 - Road surface temperature distribution measuring device using optical fiber cable - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for measuring a temperature distribution on a road surface using an optical fiber cable (hereinafter, simply referred to as an optical cable).

2. Description of the Related Art When an optical pulse is incident on an optical cable, it is known that scattered light due to Raman scattering occurs in addition to Rayleigh scattering due to nonuniformity of glass molecules. The intensity of scattered light due to Raman scattering is weaker than that of Rayleigh scattered light, but its intensity is proportional to the temperature at the location where Raman scattered light occurs, and its backscattered light returns to the incident part of the light pulse. come. Then, conventionally, it has been attempted to measure the temperature distribution over a long distance by utilizing such characteristics of the optical cable. That is, while laying an optical cable along the measurement object, detecting the back-reflected light due to Raman scattering, obtaining the temperature from the intensity of the Raman scattered light, and from the time when the optical pulse is incident until the back-scattered light returns The position is obtained from the time delay.

Problems to be Solved by the Invention It is possible to measure the temperature distribution on the road surface by utilizing the above-mentioned characteristics of the optical cable. When performing a steady measurement of, the optical cable must be inserted into the protection tube buried just below the road surface. However, in order to facilitate the insertion of the optical cable into the protective tube and to prevent the load from being directly applied to the optical cable when the protective tube is deformed, it is recommended to use a protective tube with a diameter considerably larger than the diameter of the optical cable. Become. As a result, a thick air layer exists on the outer circumference of the optical cable, and since the optical cable is located in the lower side of the protection tube, heat on the road surface is less likely to be transmitted to the optical cable. Therefore, when measuring the distribution of the road surface temperature through the optical cable, the measurement accuracy must be poor, and even if the measurement error is corrected based on the diameter of the protective tube, etc.
There was a problem that a fairly complicated process had to be performed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an apparatus capable of accurately measuring a temperature distribution on a road surface.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention inserts an optical cable into a protection tube embedded right below a road surface, and also provides an optical fiber in a space between the optical cable and the protection tube. The optical cable is filled with a non-freezing heat transfer liquid having a specific gravity larger than that of the cable, and the optical cable is connected to a measuring instrument for measuring the temperature based on Raman scattered light.

The inside of the protection tube in this invention is filled with a liquid for heat transfer that gives buoyancy to the optical cable together with the optical cable, so that the optical cable is positioned above the protection tube by buoyancy. . Therefore, in combination with the absence of air layer around the optical cable, the heat transfer between the optical cable and the road surface is performed well,
The temperature of the optical cable becomes almost equal to the temperature of the road surface. As a result, the temperature distribution on the road surface can be accurately measured by injecting an optical pulse from the measuring instrument into this optical cable and detecting backscattered light due to Raman scattering.

Embodiment Next, an embodiment of the present invention will be described with reference to the drawings.

1 and 2 are schematic illustrations showing an embodiment of the present invention, in which a protection pipe 2 made of a metal pipe, a synthetic resin pipe or the like is buried substantially horizontally just below a road surface 1 and inside thereof. An optical cable 3 is inserted through the. The optical cable 3 has a structure in which a plurality of optical fiber core wires are arranged on the outer circumference of a tensile strength wire and the outer circumference is covered, or a structure in which the optical cable core wires are loosely inserted through a small diameter pipe such as a stainless pipe. Things etc. can be used. The inside of the protection tube 2 is filled with a heat transfer medium 4 which is non-freezing and has fluidity. The heat transfer medium 4 is, for example, ethylene glycol or silicon oil having a specific gravity of about 0.8. The specific gravity of the optical cable 3 gives a levitation force to the optical cable 3, so that the optical cable 3 is protected by a protective tube. It is located in the upper part inside 2.

The optical cable 3 includes means for injecting an optical pulse into the optical cable 3, means for measuring the intensity of backscattered light due to Raman scattering, means for measuring the delay time of backscattered light, means for obtaining temperature from the intensity of backscattered light, It is connected to a measuring instrument 5 equipped with a means for obtaining the position from the delay time, and the measuring instrument 5 is further connected to an output device 6 such as a CRT or a printer for outputting the measurement result.

In the device described above, the temperature of each position in the optical cable 3 is measured by making the optical pulse enter the optical cable 3 from the measuring instrument 5 and detecting the backscattered light due to Raman scattering. In this case, the optical cable 3 is as close to the road surface 1 as possible, and the outer periphery of the optical cable 3 is filled with the transfer medium 4 for ensuring good heat transfer.
Since the heat transfer between the optical cable 3 and the optical cable 3 is excellent and the temperatures of the two are equal, the temperature distribution of the road surface 1 can be accurately measured by determining the temperature of each part of the optical cable 3. Since the heat transfer medium 4 does not contain water, it is possible to prevent the loss of the optical cable 3 from increasing due to the permeation of water. Further, even if the outside air temperature becomes low in winter, the heat transfer medium does not freeze, and the rupture of the protective tube 2 and the damage to the optical cable 3 are prevented.

Effects of the Invention As described above, in the device of the present invention, the optical cable is inserted into the protection tube embedded right below the road surface, and the space between the optical cable and the protection tube has a larger specific gravity than the optical fiber cable. Since the optical cable is connected to a measuring instrument that measures the temperature based on Raman scattered light by filling the liquid for freezing heat transfer, heat transfer between the road surface and the optical cable is performed well. As a result, the temperatures of both are almost equalized, and as a result, it is possible to accurately measure the road surface temperature using Raman scattering in the optical cable.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, and FIG. 2 is an enlarged sectional view taken along the line II-II in FIG. 1 ... Road surface, 2 ... Protective tube, 3 ... Optical cable, 4 ...
Heat transfer medium, 5 ... Measuring instrument.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Masataka Mochizuki 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Takashi Chiba 1-1-5, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (72) Inventor Yuichi Kobayashi 6 461 Satozuka, Toyohira-ku, Sapporo, Hokkaido Kita Kaido Electric Power Co., Inc. Research Institute (72) Inventor, Mitsuaki Ishioka 461 6 Satotsuka, Toyohira-ku, Sapporo, Hokkaido Kita Kaido Electric Power Co., Ltd. Company Research Institute (56) Reference JP-A-3-84102 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A non-freezing heat having a specific gravity larger than that of the optical fiber cable is inserted into a protection tube buried directly below a road surface and the space between the optical fiber cable and the protection tube is inserted. A road surface temperature distribution measuring device using an optical fiber cable, characterized in that the optical fiber cable is connected to a measuring instrument that is filled with a liquid for transmission and further measures the temperature based on Raman scattered light.