US Patent:
20080193144, Aug 14, 2008
Inventors:
Jianying Zhou - Acton MA, US
Xueyan Zheng - Andover MA, US
Kevin J. McCallion - Charlestown MA, US
Daniel Mahgerefteh - Palo Alto CA, US
Hongmin Chen - Waltham MA, US
Guoxi Sun - Woburn MA, US
Parviz Tayebati - Boston MA, US
Assignee:
Finisar Corporation - Sunnyvale CA
International Classification:
H04B 10/04
Abstract:
The frequency chirp modulation response of a directly modulated laser is described using a small signal model that depends on slow chirp amplitude s and slow chirp time constant τ. The small signal model can be used to derive an inverse response for designing slow chirp compensation means. Slow chirp compensation means include electrical compensation, optical compensation, or both. Slow chirp electrical compensation can be implemented with an LR filter or other RF circuit coupled to a direct modulation source (e.g., a laser driver) and the directly modulated laser. Slow chirp optical compensation can be implemented with an optical spectrum reshaper having a rounded top and relatively large slope (e.g., 1.5-3 dB/GHz). The inverse response can be designed to under-compensate, to produce a flat response, or to over-compensate.