Misalignment Distortion Penalty in Wavelength-Division Multiplexed Systems and Its Reduction Using Fiber Bragg Grating Lasers

Experimental studies show that DC and dynamic chips in directly-modulated DFB lasers cause distortion penalties even in low-speed (155 Mb/s - 2.5 Gb/s) wavelength-division multiplexed fiber transmission systems when the passband edges of the wavelength-selective components act as frequency discriminators and result in FM-to-AM conversion. Such penalties impose laser-to-filter wavelength alignment accuracy requirements on the order of 0.1 nm for 1 dB penalty. Low-chirp lasers such as directly-modulated fiber Bragg grating lasers are shown to reduce penalties to less then 0.5 dB for 0.2 nm detuning.