Filter concatenation in metropolitan optical networks utilizing directly modulated lasers

We studied the impact of different chirp characteristics of 2.5 Gb/s direct ly modulated lasers on the filter concatenation effects in transparent metr opolitan area optical networks. For adiabatic chirp-dominated lasers, it is found that the filter concatenation results in performance improvement, if the overall detuning between the laser wavelength and the center wavelengt h of the overall transfer function of the filter cascade is positive, and i n significant performance degradation if the detuning is negative. For a tr ansient chirp-dominated laser, a small penalty was observed for both positi ve and negative detunings. The measured Q-factor penalties, due to filter c oncatenation, were compared with theoretical Q-factor calculations for the worst-case transmitter and the results are in excellent agreement.