Patent ID: 8155535

Claim:
An optical receiver, comprising: a light receiving element for outputting a current in response to a light receiving level of an optical signal; a preamplifier whose gain is controlled in a variable manner based upon a control voltage, for converting the current signal outputted from the light receiving element into a voltage signal; a consecutive same binary symbols detecting circuit that detects a consecutive same binary symbols portion from a binary symbols stream of the voltage signal outputted from the preamplifier to output a time constant switching signal in response to a detection result thereof; a level detecting circuit that detects a voltage level of the voltage signal outputted from the preamplifier based upon a time constant which is switched/controlled in response to the time constant switching signal from the consecutive same binary symbols detecting circuit; and an amplifier that amplifies an output voltage of the level detecting circuit to apply a control voltage for controlling the gain to the preamplifier, wherein the consecutive same binary symbols detecting circuit includes: a threshold comparison comparator for comparing the voltage signal outputted from the preamplifier with a predetermined threshold; a low-pass filter for restricting a pass band of a comparison result of the comparator; and an amplitude detection comparator for detecting an output amplitude of the signal which has passed through the low-pass filter.