| 摘要 |
PURPOSE:To reduce the size and cost of an optical branching device by outputting an inputted light signal through a half-mirror unless a light signal is outputted by a light emitting element. CONSTITUTION:The light signal sent out of an A station passes through an optical fiber 15 and reaches the optical branching device 18 of a B station, and its reflected light from the half-mirror 13 is received, and self amplified in the optical branching device, and sent to the optical branching device 18 of a C station through a down optical fiber 16. The output 21 of the light receiving IC of the B station is passed through a buffer and, for example, a microcomputer 22 inputs RD and decodes the signal. Further, when this station needs to send the signal to another station, and a driver 23 is pulse-driven with a TD output and the transmission is carried out in taking aim at a signal free time of main optical paths 15 and 16, the light emitting element 17 emits pulse light for a transmission communication. If the B station and its optical branching device 18 have trouble in functioning, a sent signal from the A station passes through the optical branching device 18 of the B station and reaches the C station and if the C station is in operation, the signal is transmitted to a D station and succeeding stations, one after another.
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