SIGNAL INPUT CUTOFF DETECTOR, PHOTO RECEIVER AND SIGNAL INPUT CUTOFF DETECTING METHOD

摘要

A photo receiver branches a data signal obtained by photoelectric conversion and supplies the signal to a signal cutoff detector. Depending on the degree of an autocorrelation of a data signal obtained by an autocorrelation detector, the signal cutoff detector detects abnormality/normality. Depending on a level of a control signal to a VCO contained in a frequency phase- locked loop for use in clock generation, an out-of- synchronization detector makes determination of abnormality/normality. Outputs of both the detectors are ORed at an alarm processor and when at least one of the detectors detects abnormality, the detector generates an alarm.