| 摘要 |
PURPOSE:To detect the change of the state of a body such as the opening and closing state of the metallic manhole cover of an underground cable, etc., by connecting plural pieces of optical fiber sensors storing a bimetal switch, a battery and a switch by a permanent magnet to an optical fiber cable in series, and installing a central device at one end of the optical fiber cable. CONSTITUTION:A resistor 12 such as nichrome wire is wound around an optical fiber coil 11 made by forming optical fiber whose transmission loss varies sharply according to temperature into a coil shape, and the switch 13 provided with bimetal to open on detecting the temperature, the battery 14, and the switch 15 provided with the permanent magnet are connected to the resistor 12 so as to form a closed circuit, and these are stored in a case 3. Besides, the end parts of the optical fiber coil 11 are connected to the optical fiber cable 2. Then, plural pieces S1, S2, S3 of such the optical fiber sensors 1 are connected in series by the optical fiber cable 2 for transmission, and one end of the optical fiber cable 2 is connected to a central supervisory device 4 provided with an OTDR, etc. Thus, the supervision of the state at a place without power supply is facilitated, and in addition, this system can be easily realized by only laying the optical fiber cable. |
