Patent ID: 8165478

Claim:
An optical receiver, comprising: a light receiving element for outputting a current corresponding to a light receiving level of a received light signal; a preamplifier for converting an output current signal from the light receiving element into a voltage signal; level detecting means including: a first level detecting unit having a short time constant; and a second level detecting unit having a time constant longer than the time constant of the first level detecting unit, the level detecting means switching over to any one of the first level detecting unit and the second level detecting unit in response to a time constant switching signal to detect a voltage level of an output voltage signal output from the preamplifier; conversion gain control means for variably controlling a conversion gain of the preamplifier based on a result obtained by the detecting by the level detection means; and time constant switching control means for outputting the time constant switching signal based on the output voltage signal from the preamplifier, wherein the time constant switching control means outputs the time constant switching signal to the level detecting means so as to select the first level detecting unit when a number of consecutive identical digits of a bit string of a packet of a received burst signal is smaller than a predetermined number, and so as to select the second level detecting unit when the number of consecutive identical digits is equal to or larger than the predetermined number.