Optical transmission apparatus and bias voltage control method for the optical modulator

摘要

The optical transmission apparatus has a Mach-Zehnder optical modulator (3), a light source (1) for applying an optical signal of a continuous light to the optical modulator (3), a driving circuit (24) for inputting a driving signal into the optical modulator (3), a branching filter (4) for taking out a part of an output optical signal, a photodiode (5) for converting the taken-out output optical signal into an electric signal, a band pass filter (16) for extracting a frequency component of a driving signal included in this electric signal, an error signal generator circuit (7) for generating an error signal of a bias voltage that minimizes a value of the extracted frequency component, and a bias voltage control circuit (10) for applying a bias voltage added with this error signal to the optical modulator (3).