The accumulative demand for high-bandwidth communications has been liable for the hasty development of Optical Communication Systems (OCS). These systems employ fiber optics to convey electromagnetic waves, and need to take into account the undesired effects of dispersion and reduction on the bandwidth. In recent year, distributed feedback laser was one of the substantial topics that have been study for many years. It was introduced and developed by Kogelnik and Shank. Since that model release, people are now recognizing distributed feedback laser are imperative to human requisite. Distributed feedback lasers are useful item in society or the world because it provides the phase difference between the gain and the index grating based on using power series method to resolve the couple-wave equation that reveals the calculation of the threshold gain margin which located in complex-couple distributed feedback laser.

This handbook brings together cutting-edge research and reviews on distributed feedback laser diodes; illustrates the method of calculation the threshold gain margin that play important role in the optic world. This volume is intended to the study of semiconductor lasers with distributed feedback (DFB), namely their usage as the light source in high bit rate optical communication systems (OCS). This is particularly important in situations where direct modulation (DM) of the emitter is used. In addition, it also presents emphasis how distributed feedback laser (DFB) play important role in optic world and the advantage or disadvantage of using DFB. The fabrication of high-efficiency distributed feedback laser diodes is described.