Apparatus and method for laser bias and modulation control

Apparatus for controlling the bias and modulation of a laser diode, comprising:

• a monitor device responsive to an output from said laser diode and providing a photo-current having a magnitude indicative of the laser diode output;
• a low input impedance current-to-voltage converter coupled to said monitor device and converting said photo-current into a photo-voltage;
• a power divider circuit coupled to said low input impedance current-to-voltage converter and producing three power output signals each having one-third power in response to said photo-voltage;
• an average bias power control circuit coupled to said power divider and receiving one of said power output signals, said average power control circuit averaging said received power output signal, comparing said averaged power output signal with a predetermined reference average signal, and generating an average laser bias control signal in response to said comparison;
• a modulation power control circuit coupled to said power divider and receiving two of said power output signals, said modulation power control circuit detecting a maximum and a minimum peak in said received power output signals, averaging said detected maximum and minimum peaks, comparing said maximum and minimum peaks with said averaged power output signal from said average bias power control circuit, and generating a digital modulation control signal and an analog modulation control signal in response to said comparison;
• and
• a laser driver, coupled to said average bias power control circuit and said modulation power control circuit and receiving low and high speed, digital and analog input signals, for biasing and modulating said laser diode in response to said average laser bias control signal, said digital and analog modulation control signals, and said low and high speed, digital and analog signals.

A method for optimal linear operation of a laser diode, comprising:

• receiving low and high speed, digital and analog input signals;
• driving said laser diode in response to said received input signals;
• monitoring the output from said laser diode and providing a laser output signal having a magnitude indicative of the laser diode output;
• comparing an average of said laser output signal with a predetermined reference average signal and biasing said laser diode in response thereto;
• comparing a midpoint of maximum and minimum peaks of said laser output signal with said average of said laser output signal, and modulating said laser diode in response thereto.

A method for controlling the bias and modulation of a laser diode, comprising:

• receiving low and high speed, digital and analog input signals;
• driving said laser diode in response to said received input signals;
• monitoring the output from said laser diode and providing a laser output signal having a magnitude indicative of the laser diode output;
• averaging said laser output signal;
• comparing said averaged laser output signal with a predetermined reference average signal and generating an average laser bias control signal in response thereto;
• detecting a maximum and a minimum in said laser output signal, averaging said detected maximum and minimum, comparing said maximum and minimum peaks with said average laser bias control signal, and generating a digital modulation control signal and an analog modulation control signal in response to said comparison;
• biasing said laser diode in response to said average laser bias control signal;
• and
• modulating said laser diode in response to said digital and analog modulation control signals.