OPTICAL SHUTOFF DETECTOR, OPTICAL RECEIVER, OPTICAL TRANSMITTER AND OPTICAL SHUTOFF DETECTION METHOD

摘要

PROBLEM TO BE SOLVED: To fix time until an optical shutoff alarm signal is outputted as short. SOLUTION: The optical shutoff detector is provided with an optical power monitor circuit 11 for outputting voltage according to input power of an optical signal to be inputted, a threshold setting circuit 12 for outputting threshold voltage Vth according to the input power of the optical signal and a comparator circuit 13 for comparing output voltage of the optical power monitor circuit 11 with the threshold voltage Vth and for outputting the optical shutoff alarm signal for informing shutoff of input of the optical signal, sets the threshold voltage Vth of the optical power monitor circuit 11 when the optical signal is inputted as smaller than output voltage of the optical power monitor circuit 11 when the optical signal is inputted and sets a time coefficient of the threshold setting circuit 12 larger than a time coefficient of the optical power monitor circuit 11.