Patent ID: 8718107
Filing Date: 2014-05-06
Classification: H01S,H04B

Abstract:
1. A bias circuit coupled to an electro-absorption modulated laser, including: a drive circuit, which is used for providing a forward bias voltage to a laser diode in the electro-absorption modulated laser, wherein the forward bias voltage enables the laser diode to generate laser; a direct current bias voltage circuit, which is connected to a cathode of an electro-absorption modulator in the electro-absorption modulated laser, wherein the direct current bias voltage circuit is used for providing a positive direct current bias voltage to the cathode of the electro-absorption modulator and causing a reverse bias voltage of the electro-absorption modulator to fall within a predefined range of modulation such that, when the reverse bias voltage falls within the predefined range of modulation, the electro-absorption modulator utilizes the laser generated by the laser diode as an optical carrier wave, modulates the optical carrier wave with a modulation voltage, and outputs a modulated optical signal; and a feedback control circuit, used for generating a voltage control signal for controlling the drive circuit according to the modulated optical signal and a bias current, wherein the bias current is generated by the laser diode under drive of the forward bias voltage; wherein, under control of the voltage control signal, the drive circuit regulates the forward bias voltage provided to the laser diode so as to regulate the bias current in the laser diode; wherein the feedback control circuit includes: a bias current detecting circuit, which is used for detecting the bias current in the laser diode, and converting it into a first voltage signal and outputting the first voltage signal; a first amplifier, which is used for converting an optical current output by a photo-detector in the electro-absorption modulated laser into a second voltage signal and amplifying the second voltage signal, wherein the photo-detector is used for sensing an optical power of the modulated optical signal, and converting it into the optical current; a comparator, which is used for treating the amplified second voltage signal as a power feedback voltage, and comparing the amplified second voltage signal with a preset power voltage to generate a differential signal; and a feedback controller, which is used for generating the voltage control signal for controlling the drive circuit, according to the differential signal generated by the comparator and the first voltage signal output by the bias current detecting circuit, and outputting the voltage control signal.