Patent ID: 7903981

Claim:
A software-based electro-optic modulator bias control system resident in an optical transceiver comprising an electro-optic modulator, comprising: an optical-to-electrical converter comprising a transimpedance amplifier; an analog-to-digital converter; a software algorithm, wherein the software algorithm is operable for determining an optimum bias voltage applied to the electro-optic modulator by discovering a maximum average optical power transmitted by the electro-optic modulator, or quadrature point, wherein the quadrature point is discovered by determining at what bias voltage the slope of an average optical power transmitted by the electro-optic modulator, defined as an optical power change given an incremental bias voltage change, is equal to zero; and a software control loop operable for determining if a radio frequency port of the electro-optic modulator is driven with a voltage that is greater than (over-driven) or less than (under-driven) the peak-to-trough voltage of a response curve of the electro-optic modulator; wherein determining if a radio frequency port of the electro-optic modulator is driven with a voltage that is greater than (over-driven) or less than (under-driven) the peak-to-trough voltage of a response curve of the electro-optic modulator is performed by determining if, when a radio frequency drive level is increased, the average optical power transmitted by the electro-optic modulator at the point of zero slope increases compared to an average optical power at the point of zero slope at the previous radio frequency drive level, or, when the radio frequency drive level is increased, the average optical power transmitted by the electro-optic modulator at the point of zero slope decreases compared to the average optical power at the point of zero slope at the previous radio frequency drive level, respectively.