Patent ID: 6046838
Filing Date: 2000-04-04
Classification: G02F,H04B

Abstract:
A bias control system for automatically controlling a bias point of an electro-optic modulator, wherein the electro-optic modulator has an electrical input, an optical input and an optical output, for modulating an optical carrier received at the optical input by an electrical signal received at the electrical input to produce a modulated optical signal at the optical output, the bias control system comprising:a pilot signal generator for generating a pilot signal applicable to the electrical input of the electro-optic modulator and further for generating a coherency reference signal;an optical sampler for sampling the optical output of the electro-optic modulator, wherein the sampled optical output includes a pilot component resulting from the pilot signal;a coherent feedback circuit coupled to the optical sampler and to the pilot signal generator for coherently generating an error signal based on the coherency reference signal and on the pilot component in the sampled optical output; anda bias generator coupled to the coherent feedback circuit for generating a bias signal responsive to the error signal, the bias signal applicable to the electrical input of the electro-optic modulator for controlling the bias point of the electro-optic modulator.