Wavelength shift-free all-optical 2R regenerator based on four-wave mixing

In this work we numerically investigated an all-optical 2R (reamplification and reshaping) regenerator based on four-wave mixing and implemented with two stages of highly nonlinear dispersion-shifted fiber. The two-stage setup, aside from providing an almost ideal transfer function, allows for the regenerated signal to maintain its original wavelength (wavelength shift-free). We tested the device operation by applying to its input an optical signal affected by accumulative amplified spontaneous emission noise from a cascade of erbium-doped fiber amplifiers. To assess the regenerator performance, we calculated and compared the Q-factor and extinction rate of the input signal with the corresponding values for the output signal. Our results show, due to the action of the proposed two-stage wavelength shift-free regenerator, the input signal Q-factor improves by up to 70% and its extinction ratio by up to 3 dB whilst maintaining the input signal carrier frequency.