Patent ID: 7899338
Filing Date: 2011-03-01
Classification: G02F

Abstract:
1. A method for controlling bias of optical modulator for controlling a DC bias of each of a plurality of optical modulating sections of an optical modulator comprising an optical waveguide formed on a single substrate with an electro-optic effect, and the plurality of optical modulating sections for modulating optical waves propagating through the optical waveguide, and being configured so as to combine the optical waves modulated by the plurality of optical modulating sections, comprising the steps of: superposing a low frequency electrical signal with a specific frequency on a modulating signal or a DC bias applied into a specific first one of the plurality of optical modulating sections; detecting a change of light intensity corresponding to the low frequency electrical signal from the optical wave exiting from the specific first optical modulating section, into which the modulating signal or the DC bias superposed with the low frequency electrical signal is applied; and controlling the DC biases of the specific first optical modulating section and at least one second optical modulating section, into which the modulating signal or the DC bias without superposing of the low frequency electrical signal is applied, based on the detected change of light intensity.