TWO-WAY OPTICAL LINK TRANSMITTER-RECEIVER

PURPOSE:To detect the presence or absence of a fault of a data link by counting a difference between transmission and reception number of timing clocks and comparing the count value with a present value. CONSTITUTION:A station frequency-divides a clock A and generates a timing clock A for each prescribed period. The timing clock A is coded as a CRV signal and sent to a station B. A timing clock B obtained by synchronizing the timing clock A decoded by a station B with the clock B is returned to the station A. Thus, the timing clock A is circulated in a loop. Then a counter 11 counts a difference between transmission and reception number of timing clocks A, B in the station A. When the count value is more than a preset value, an alarm circuit 12 is operated.