| 摘要 |
PURPOSE:To increase the number of valves to be detected and the number of bodies whose presence is to be detected by interposing optical fiber amplifiers in plural optical transmission lines which extend from an optical distributor to an optical coupler. CONSTITUTION:A single light pulse which has narrow time width is sent from an optical transmitter 1 to an input-side optical transmission line 30a and distributed equally by the optical distributor 2 to a 1st optical transmission line 3, a 2nd optical transmission line 4, a 3rd optical transmission line 5, and a 4th optical transmission line 6. A 1st optical fiber amplifier 22, a 2nd optical fiber amplifier 23, a 3rd optical fiber amplifier 24, and a 4th optical fiber amplifier 25 are adjusted in amplification factor respectively to compensate or reduce the distribution loss of the optical distributor 2 that the light pulse sent by the optical transmitter 1 has before reaching an optical receiver 16, the transmission loss of the optical transmission lines, the insertion loss of delay lines 7 - 10, the insertion loss of optical ON-OFF sensors 31 - 34, and the coupling loss of the optical coupler 15, and also makes light pulses 1, 2, 3, and 4, arriving at the optical receiver 16, have nearly the same power. The output of the optical receiver 16 is discriminated by a pulse discriminator 17. |
