REAL TIME CONSTANT EXCITATION RATIO (ER) LASER DRIVING CIRCUIT

摘要

Adverse effects to laser excitation ratio slope caused for example by ambient temperature maybe compensated for by adjusting drive current to the laser. The real time excitation ratio slope may be determined by dithering the code word by +/- 1 least significant bit (LSB) of a digital-to-analog drive current source (DAC). A slight variation in laser output power caused by the dither may be detected and used to calculate in real time the laser excitation ratio slope. This may be used to select a drive current to compensate for ambient changes keeping the excitation ratio slope substantially constant.