TWDM-PON Burst Mode Lasers With Reduced Thermal Frequency Shift

For emerging TWDM-PON systems, based on burst-mode operation over WDM channels, a main challenge is the laser self-heating during bursts. This effect creates a drift of the emission frequency, leading to degraded transmission performances, and perturbation of adjacent channels. We explain an accurate method for characterization of wavelength drift during bursts at a bit time level, and use this method along the paper to characterize frequency drifts in burst-mode operation. First, we present an optimized directly modulated laser design for reduced self-heating, compatible for 100 GHz-spaced systems. Then, we propose a new solution based on counter-heating of the laser with a side heater, enabling to reduce self-heating induced frequency drift. This counter-heating scheme is applied to a standard laser, demonstrating a stringent reduction of frequency drift, and making it compatible for 100-GHz-spaced TWDM-PON transmissions. This simple method opens the way for simple low-cost transmitters in dense and high power TWDM-PON systems.