Optical transmitter having optical modulator

摘要

An optical transmitter having a Mach-Zender waveguide optical modulator (48) comprising a signal electrode (12) fed with a driving signal for effecting modulation, a bias electrode (16) for controlling operating point and a bias feedback control circuit. Because the signal electrode and the bias electrode are isolated from each other, a driving circuit (54) and the signal electrode (12) can be connected in a DC setup. This permits stable operating point control and improves waveform characteristics. Also it is disclosed an optical transmitter having a Mach-Zender waveguide optical modulator with a delay optical waveguide (118) directionally coupled to at least one of the Mach-Zender branching optical waveguides and provided with an electrode (124,126) for controlling the directional coupling ratio.