Feedback control of lasers in fiber optic systems

摘要

A feedback control arrangement in a fiber optic lightwave transmitter compensates for changes in the average power coupled from a laser into a fiber due to certain displacements of the fiber relative to the laser. The arrangement includes a laser (10) and an optical fiber (28) having a beveled end face (30) oriented to couple a major portion (13) of the laser beam into the fiber. The position of the fiber relative to the beam axis (12) is sensed by a pair of photodetectors (20, 22) positioned on opposite sides of the beam axis so as to receive other portions of the beam (15, 17) not coupled into the fiber. A feedback circuit (24) is selectively responsive to the smaller of the photodetector outputs for controlling the drive current to the laser so as to maintain the average power coupled into the fiber essentially constant.