Patent ID: 7092643
Filing Date: 2006-08-15
Classification: G02F,H04B

Abstract:
1. An optical transmission apparatus for transmitting an optical pulse string having a frequency two times that of a driving signal (fc), said optical transmission apparatus comprising: a Mach-Zehnder optical modulator; a light source which inputs an optical signal into said optical modulator; a driving unit which inputs the driving signal into the optical modulator; a converting unit which receives a frequency component of the driving signal (fc), takes out a part of an optical signal output from said optical modulator and converts that part of the optical signal into electric signal; an extracting unit connected to the converting unit, the extracting unit extracting a frequency component of the driving signal (fc) included in the electric signal converted by said converting unit; an error signal generating unit which includes a level detector for detecting a level of the frequency component of the driving signal (fc) and a processing unit connected to said level detector receiving said frequency component and generating an error signal based on the level detected by the level detector, the generated error signal being output to a digital to analog converter connected to the processing unit which converts the error signal from a digital error signal to an analog error signal the error signal generating unit generating an error signal of a bias voltage for minimizing a value of a frequency component of the driving signal (fc) extracted by said extracting unit; and a bias voltage control unit which applies a summed bias voltage obtained as a result of addition of the bias voltage and a voltage corresponding to the analog error signal to said optical modulator.