Optoelectronic properties of semiconductor lasers butt-coupled to optical fibers

The authors have theoretically and experimentally examined the electrical noise properties of a semiconductor laser coupled to a single-mode fiber with a plane endface. It is found that the performance of semiconductor lasers butt-coupled to optical fibers critically depends on the axial position of the fiber. Measurements show that the influence of the fiber may change the output power as much as ±40% and the modulation bandwidth, determined by the relaxation frequency by as much as ±35% (for a bias 15% above the solitary threshold). Moreover, the pulse response and the longitudinal mode spectrum deteriorate if the laser-to-fiber distance departs from its optimal value. The authors propose a nonoptical scheme for maintaining the optimal laser-to-fiber distance so as to avoid these degrading effects