MISALIGNMENT DISTORTION PENALTY IN MODERATE-SPEED DIRECTLY MODULATED WDM SYSTEMS AND ITS REDUCTION USING FIBER BRAGG GRATING LASERS

Experimental studies show that de and dynamic chirps in directly modul ated distributed-feedback (DFB) lasers cause even larger distortion pe nalties in Lower speed (155-622 Mb/s) wavelength-division multiplexed (WDM) fiber transmission systems than in high speed (2.5 Gb/s) when th e passband edges of the wavelength-selective components act as frequen cy discriminators and result in FM-to-AM conversion, Such penalties im pose laser-to-filter wavelength alignment accuracy requirements on the order of 0.1 nm for 1-dB penalty, Low-chirp lasers such as directly m odulated fiber Bragg grating lasers are shown to reduce penalties to l ess than 0.5 dB for 0.2-nm detuning.