On the polarisation sensitivity and performance optimisation of a dual pump four wave mixing based wavelength converter

This paper presents a detailed investigation of the performance of a wavelength conversion scheme. The converter is based on four wave mixing in semiconductor optical amplifiers using two parallel polarised pumps. Measurements of the conversion efficiency and the signal to background noise ratio of the two replicas of the signal, for the cases of the signal polarisation being either parallel or orthogonal relative to the pump waves have been carried out. These measurements will reveal the polarisation sensitivity of this scheme which appears to be less than 1 dB when the wavelength spacing between the signal and its closest spaced pump is larger than 12 nm. The experimental results are supported in a satisfactory way by theoretical considerations. A simple theoretical expression describing the polarisation sensitivity have been derived and the theoretical results are in good agreement with those experimentally obtained. A performance comparison of the conversion scheme using semiconductor optical amplifiers with different lengths but the same structure is also performed. Through the following study the optimum operational conditions for this wavelength conversion scheme will be determined.