Patent ID: 6362913
Filing Date: 2002-03-26
Classification: G02F

Abstract:
An optical modulation apparatus including an optical modulator having a voltage-optical output characteristics in which optical output varies periodically with respect to a voltage value of an electrical drive signal, and a drive signal generator for generating an electrical device signal which drives the optical modulator by an amplitude between two light emission culminations or two light extinction culminations of the voltage-optical output characteristic, said apparatus comprising:a low-frequency oscillator generating a prescribed low-frequency signal; a low-frequency superimposing unit superimposing the prescribed low-frequency signal on the drive signal by varying a center level of the drive signal by said low-frequency signal; a low-frequency signal detection unit detecting operating-point drift of the optical modulator based upon the low-frequency signal component contained in an optical signal output from said optical modulator; and an operating-point control unit controlling the operating point of the optical modulator in dependence upon the drift of the operating point of the optical modulator.