Patent ID: 6580544
Filing Date: 2003-06-17
Classification: G02F,H04B

Abstract:
A method for automatic correcting a bias voltage on an optical modulator of an external-modulation optical emitter, wherein when the optical modulator receives a base control signal provided by a bias voltage controller, in which the base control signal includes a combination of a base signal and a DC voltage, a receiving terminal of the bias voltage controller can receive a first second-order harmonic component signal from the optical modulator, wherein a second second-order harmonic component signal with a frequency equal to a frequency of the first second-order harmonic component signal is generated in the bias voltage controller and is compared with the first second-order harmonic component signal, so as to produce the DC voltage used to control the bias voltage on the optical modulator, the method comprising:switching the receiving terminal to a ground voltage when the bias voltage controller is at a measuring cycle; measuring an extra offset voltage and a zero shifting voltage induced by the bias voltage controller; switching the receiving terminal to receive the first second-order harmonic component signal when the bias voltage controller is at a correcting cycle; obtaining a DC error voltage by comparing the first second-order harmonic component signal with the second second-order harmonic component signal; subtracting the extra offset voltage and the zero shifting voltage from the DC error voltage; and using the DC error voltage after subtraction to control the bias voltage on the optical modulator.