| 摘要 |
PURPOSE:To simplify the circuit by bringing an output of a photocoupler of an intermediate relay station of a ring form optical fiber line to a low level received by an adjacent relay station only and increasing the output to a level reaching an adjacent next relay station with skipping at fault. CONSTITUTION:Plural relay stations are provided at the midpoint of a line where an optical fiber 40 is formed in a ring. Each relay station comprises a photocoupler 30 including a half mirror 31, an optical signal from the upper stream is reflected on the half mirror 31, photoelectrically converted (32) and enters a processing circuit 34, where the signal is subjected to processing, the result is electrooptically converted (33), enters the half mirror 31 of the coupler 30 and is transmitted to the down stream. The output level is kept to a level to be received by the next relay station only. If any of the relay stations is faulty, the optical signal does not circulate the loop, an output of the relay station of the upper stream of a faulty relay station is increased and the faulty relay station is skipped. Thus, no optical switch is required and the system with high reliability is constituted. |
