Patent ID: 8280252

Claim:
A subscriber terminal for use in an optical communication network including a central-office apparatus, comprising: a variable optical attenuator for attenuating an optical signal received from the central-office apparatus; an optical-electric converter for converting the optical signal received via said variable optical attenuator to a corresponding electric signal; a clock extractor for extracting a clock from the electric signal and producing a clock extraction information signal representing whether or not the clock is extracted stably; and a controller for controlling said variable optical attenuator, said controller including: a clock extraction decider for determining whether or not said clock extractor stably extracts the clock on a basis of the clock extraction information signal; a receiving level adjuster for setting an attenuation value to a value between a predetermined minimum value and a predetermined maximum value; and an attenuation controller for setting the attenuation amount for said variable optical attenuator to the attenuation value.