Patent ID: 8098998

Claim:
An optical transmitter having a single-drive LN-MZ modulator, comprising: means for converting a data signal into a three-level, duobinary signal; means for generating a three-level, optical duobinary signal by modulating an optical signal using the duobinary signal; means for amplitude modulating by a low-frequency signal onto the duobinary signal input into the means for generating the optical duobinary signal; means for outputting a monitor output signal by monitoring the output from the means for generating the optical duobinary signal; and means for generating and controlling a bias voltage applied to the means for generating the optical duobinary signal; wherein the means for generating and controlling a bias voltage generates two bias voltages (Vb+ΔVb) and (Vb−ΔVb) by adding a drift bias ±ΔVb to a set bias value Vb, and applies the two bias voltages in alternation to the means for generating the optical duobinary signal; wherein the two bias voltages are respectively generated by first solving for the differences V−mon and V+mon between the monitor output signal value when the low-frequency signal is high and the monitor output signal value when the low-frequency signal is low; and wherein, upon solving for the difference between V−mon and V+mon, a new set bias value Vb is configured and the two bias voltages (Vb+ΔVb) and (Vb−ΔVb) are generated based on the difference between V−mon and V+mon.