PURPOSE: To obtain an optical fiber type water infiltration sensor which can detect water filtration quickly and accurately by utilizing a hygroscopic swelling material composed of a rubber-like material, highly hygroscopic resin, hydrophilic resin, and foaming agent.
CONSTITUTION: Optical fibers 5 and 5a respectively taken out from optical fiber cables 1 and 1a by removing sheaths are connected with each other by their end faces and the outer periphery of each connected section is coated and sealed. After connecting the optical fibers 5 and 5a and sealing the connected sections of the fibers 5 and 5a in such way, the entire body of the connected section is housed in an enclosure 6 in a watertight state. This water infiltration sensor tool 8 is connected between each one of the optical fibers 5 and 5a which is not used tor communication and water infiltration into the enclosure 6 is detected through the deformation and a change in light transmitting quantities of the fibers 5 and 5a due to the swelling of the tool 8 by the water infiltrated into the enclosure 6. A mixture of 100 pts.wt. of a rubber-like material, 50-500 pts.wt. of highly hygroscopic resin, 5-50 pts.wt. of hydrophilic resin, and 5-50 pts.wt. of foaming agent is used as the hygroscopic swelling material for making the sensor tool 8.
SAKURABA YUKIO
UMEDA MASANARI
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