Performance Improvement of Low-Cost 2.5-Gb/s Rated DML Sources Operated at 10 Gb/s

The transmission performance improvement of low-cost conventional directly modulated laser (DML) sources, fabricated for operation at 2.5 Gb/s but modulated at 10 Gb/s is presented and experimentally demonstrated. Performance improvement is achieved by electronic feed-forward and decision-feedback equalization as well as offset optical filtering at the receiver end. Experimental studies consider both transient and adiabatic chirp dominated DML sources. The transmission improvement is evaluated in terms of required optical signal-to-noise ratio (OSNR) for bit-error-rate values of 10^-9 versus transmission length over uncompensated links of standard single-mode fiber (SSMF). Additionally, the optimum filter position is examined in combination with equalization and in terms of OSNR versus detuning from the center wavelength.