Cascaded all-optical wavelength conversion for RZ-DPSK signal based on four-wave mixing in semiconductor optical amplifier

We have demonstrated ten-stage cascaded wavelength conversion together with 800-km transmission for 10-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) format using four-wave mixing (FWM) in semiconductor optical amplifiers. To the best of our knowledge, this is the first experiment reported on cascade wavelength conversion for RZ-DPSK format, which cannot be realized by methods based on cross-gain modulation and cross-phase modulation using a semiconductor optical amplifier. Compared with wavelength conversion using FWM for conventional on-off keying format, the signal-to-pump ratio for RZ-DPSK format can be increased to higher level to achieve better performance.

I. Introduction

Wavelength conversion technique is very important for the implementation of future all-optical networks. Recently, extensive studies have been carried out in this area. The majority of wavelength conversion demonstrations have relied on cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) [1], [2]. SOA-based interferometers such as delayed-interference signal wavelength converters (DISCs) and Mach–Zehnder interferometer (MZI), were shown to provide wavelength conversion with high power efficiency, large conversion range, and also high optical signal-to-noise ratio (OSNR) for the converted signal. Some experiments have demonstrated cascaded wavelength conversion at 10 and 40 Gb/s for return-to-zero (RZ) format [3], [4].