OPTICAL RECEIVER AND OPTICAL RECEIVING METHOD

PROBLEM TO BE SOLVED: To simplify an optical receiver configuration for improving reliability by minimizing analog control elements of the receiver.SOLUTION: The optical receiver comprises: a photoelectric transducer that performs photo-electric conversion of a received optical signal; an amplifier that controls a gain so as to obtain a constant output signal amplitude of the photoelectric transducer; an A/D converter that converts an encoded multi-level signal amplified by the amplifier into a digital value; a running key generation unit to generate the running key by using a public key shared with a sender; a comparator that compares a level of the encoded multi-level signal supplied from the A/D converter with a base level, which is specified by the running key generated in the running key generation unit, in a digital signal state; and a polarity decoding unit that controls inverting/non-inverting of a polarity of a decoded signal according to a comparison result by the comparator.