DEVICE FOR DETECTING INPUT INTERRUPTION OF OPTICAL SIGNAL AND DEVICE FOR DETECTING INPUT INTERRUPTION OF ELECTRIC SIGNAL

摘要

PROBLEM TO BE SOLVED: To provide a device capable of accurately detecting the input interruption of an optical signal.;SOLUTION: A photoelectric converter 10 converts the optical signal to an electric signal. A clock extraction circuit 20 extracts a clock signal from the electric signal outputted from the photoelectric converter 10, and forms three clock signals CLK1, CLK2, and CLK3 in which a phase is deviated only a prescribed period of time. First/second/third discrimination reproduction circuits 31, 32, and 33 of a discrimination reproduction discriminating part 30 discriminates whether the electric signals respectively exceed a preset threshold at each output timing of the three clock signals. The discrimination result is entered to a logic circuit 41 in an alarm output 40. The presence of the input of the optical signal is detected corresponding to the predetermined logic. The detection result is outputted to a circuit 42 for detecting the optical input interruption. The circuit 42 for detecting the optical input interruption outputs an alarm signal when the detection result is the input interruption of the optical signal.;COPYRIGHT: (C)2005,JPO&NCIPI