Design of distributed feedback(dfb) laser-based external cavity structures for coherent communications

Critical parameter combinations, which govern the reduction of the linewidth and tunability in a DFB laser-based external cavity structure, are determined by a mathematical model. The coupling coefficient, operating point of the DFB laser, refractive index and the external cavity length are found to greatly determine the absolute linewidth of this structure. An optimum continuous tuning range of 55 GHz is predicted. However, the usable tuning range is much smaller as will be seen. © 1989 SPIE