Laser control circuit for maintaining constant power and extinction ratio

摘要

A laser transmitter with a laser diode and first and second feedback loops for maintaining a constant average laser power output and constant extinction level. A photo detector samples and detects transmitter laser light. The detector output is split, with one portion sent to a low-pass detector circuit for detecting the average laser power and using the detected signal to control a laser power current bias source. The other portion of the detector output is delivered to a high-pass detector circuit for detecting the amplitude of the modulation for outputting a signal to control a modulation laser current source that adds to the power current bias for a logic "1" state and does not add to the power bias for a logic "0" state.