Patent ID: 7400661

Claim:
A bias control for a laser driver circuit comprising: a laser diode that is controlled to emit modulated light that travels along a first optical path and a second optical path, wherein said laser diode is driven by a bias current when said laser diode is modulated off and an on state operating current when said laser diode is modulated on so as to emit laser light; a first detector that detects the optical power of light along said first optical path and provides a first detector signal; a first polarizer in said first optical path between said laser diode and said first detector; a second detector that detects the optical power of light along said second optical path and provides a second detector signal; a bias compensation circuit that receives said first detector signal and said second detector signal and provides a bias current control signal, wherein said first detector signal corresponds to the optical power of polarized light along said first optical path, said second detector signal corresponds to the optical power of said light along said second optical path and said bias current control signal is determined based upon a ratio of said first detector signal relative to said second detector signal and a comparison of the ratio with respect to a predetermined bias signal; and a programmable bias current source that supplies said bias current to said laser diode, said programmable bias current source programmed by said bias current control signal of said bias compensation circuit so as to adjust said bias current to a predetermined value.