Optical receiver

摘要

An optical receiver including: a preamplifier capable of changing a conversion gain in accordance with a reception level of a received burst signal; a gain control circuit capable of switching between a fast time constant and a slow time constant; and a convergence determination circuit for outputting a time constant switching signal in accordance with a state of the gain control circuit (transient state or steady state) and a reset signal between the burst signals. This configuration can switch the time constant of the gain control circuit at an appropriate timing.

主权项

1. An optical receiver, comprising:
a photodetector for converting a light reception signal into a current signal; a preamplifier for converting the current signal output from the photodetector into a voltage signal; gain control means for detecting an average voltage of the voltage signal output from the preamplifier by a first average voltage detection section that has a first time constant or a second average voltage detection section that has a second time constant longer than the first time constant, and controlling, with use of the detected average voltage, a conversion gain of the preamplifier to be a desired gain according to a reception level of the light reception signal; and convergence determination means for determining whether the gain control means is in a transient state or in a steady state, and generating a time constant switching signal for selecting the first average voltage detection section of the gain control means when it is determined that the gain control means is in the transient state and selecting the second average voltage detection section of the gain control means when it is determined that the gain control means is in the steady state, wherein the convergence determination means comprises:
a third average voltage detection section that has a third time constant longer than the first time constant of the first average voltage detection section and shorter than the second time constant of the second average voltage detection section, for detecting an average voltage of the voltage signal output from the preamplifier;a difference voltage detection section for calculating a difference voltage between the average voltage detected by the first average voltage detection section and the average voltage detected by the third average voltage detection section when the first average voltage detection section is selected; anda comparator section for comparing the difference voltage with a predetermined threshold voltage and determining whether the gain control means is in the transient state or in the steady state based on a result of the comparison.