Effect of gain spectral linewidth on chirp of 10 Gbit/s RZ data stream converted by inverse optical comb injected semiconductor optical amplifier

By temporally and spectrally reshaping the gain spectrum of the SOA, we investigate the effect of the backward injecting linewidth on the rise/fall time, duty-cycle and frequency chirp of the 10 Gbit/s format-converted pulsed RZ data-stream from the inverse-optical-comb injected SOA. The NRZ-to-RZ conversion in the SOA under intense XGM not only results in patterning but also induces large chirp with its level proportional to the amount of gain depletion. The multi-wavelength inverse-optical-comb injection effectively depletes the TWSOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 6.7 GHz. The converted pulsed RZ signal is subject to the net effect of addition chirp as well as dispersion being to increase the power penalty of the link. Under the injection of multi- and single-wavelength inverse-optical-comb with average power of 16.5 dBm and duty-cycle of 64%, the peak-to-peak chirp of the converted pulsed RZ signal are 11.95 GHz and 13.23 GHz, respectively. The FWHM of the multi- and single-wavelength injection converted pulsed RZ data are 31.64 ps and 30.81 ps, respectively. The rising time remain almost unchanged, however, the falling time was monotonically reduced by increasing injection power. The evolution of FWHM with injection power exhibits similar trend with falling time. In comparison with single-wavelength inverse-optical-comb injection, multi-wavelength injection exhibits better frequency-chirp reduction performance.