Reliable semiconductor light sources for fiber optical communications

This paper reviews reliability aspects of CW laser diodes and high radiance LED´s. The most advanced of these devices are AlGaAs heterojunction structures designed for emission in the 8200- 8600 Å spectral range where most of the available fibers have the lowest transmission loss (5-10 dB/ km). In CW lasers emitted power levels to about 100 mW (from one side) have been achieved. More modest power levels are obtained from LED´s (1-5 mW). Excellent progress has been made in identifying and eliminating the major failure mechanisms which plagued early devices. A major failure mode is known to be caused by certain metallurgical defects in the vicinity of the p-n junction. In addition, CW laser diodes can degrade as a result of facet damage. Both of the basic failure modes have been brought under substantial control, and stable device operation for many thousands of hours is being achieved.