All optical signal regeneration in cascaded Mach-Zehnder interferometer wavelength converter

The optimum condition of all optical signal regeneration (2R) was analysed in a cross-phase modulation (XPM) wavelength converter based on a Mach-Zehnder interferometer (MZI) using semiconductor optical amplifiers (SOAs). Since the input and probe signal power affect the transfer function of an interferometer, optimum operation conditions are needed to improve the pulse shape of the converted signal. A serially cascaded dual MZI-XPM wavelength converter scheme was proposed to realise the wavelength conversion and optical signal regeneration at the same time. The signal reshaping was achieved by controlling the gain and phase conditions of conventional SOAs in an interferometric decision circuit. To obtain the operation of a nonlinear optical gate (NLOG) using a decision circuit, the two SOAs should have different length and injection current. Based on the simulations of pulse shape in the time domain and bit error rate, we have confirmed that this scheme greatly improves the optical signal quality