Theoretical study on linewidth characteristics of SGDBR lasers for coherent optical communications

Summar form only given. Widely tunable lasers are expected to be used in coherent optical communications as primary laser sources for a more agile optical network. Sampled grating distributed Bragg reflector (SGDBR) lasers have been proven to be a good candidate for these applications. SGDBR lasers, which are multi-section lasers, exhibit a more complex linewidth broadening than fixed-wavelength semiconductor lasers1. To understand how the phase noise processes in the laser will affect the performance of coherent systems, it is important to be able to accurately model their linewidth. Besides spontaneous emission noise in the active section, shot noise in the passive sections results in a significant linewidth broadening when the tuning current is injected. This process when combined with the detuning of the cavity mode and super mode, consequently result in regular variations of the linewidth2.Based on TLLM we have developed a theoretical model for SGDBR lasers previously3. In this paper, we extend this model to investigate the linewidth of SGDBR lasers taking into account spontaneous emission noise in the active section and shot noise in the passive sections. The linewith of SGDBR lasers is successfully characterized with 1MHz frequency resolution by the developed model.