Patent ID: 6317249
Filing Date: 2001-11-13
Classification: G02F,H04B

Abstract:
An optical modulator, comprising:a light source;a drive circuit generating a drive signal depending on an input signal;a low frequency oscillator generating a low frequency signal;a low frequency superimposing circuit amplitude-modulating said drive signal with the low frequency signal of said low frequency oscillator;a modulator modulating a light beam emitted from said light source depending on an output of said low frequency signal superimposing circuit;a light receiving element monitoring an optical output power of said optical modulator;a phase detector detecting a low frequency characteristic included in a signal output from said light receiving element for comparison with said low frequency signal generated by said low frequency oscillator;an operating point shift circuit receiving an electrical signal of the light receiving element and outputting a signal for shifting an operating point of the modulator in accordance with an output power of said light receiving element; anda controller controlling the operating point of the optical modulator with an output of said phase detector and an output of said operating point shift circuit.