Optimization of Optical Band-Pass Filters for All-Optical Wavelength Conversion Using Genetic Algorithms

We propose using genetic algorithms to numerically optimize optical band-pass filters (OBFs) for inverted and noninverted wavelength conversion based on semiconductor optical amplifiers. A fourth order Hermite–Gaussian sum series is used to describe the filter transfer function. Signal eye openings greater than 30 dB are obtained for both inverted and noninverted output signals. The dependence of the eye opening, overshoot and pulse amplitude fluctuation on variations in the filter center frequency and bandwidth is explored. We find that for an optimized eye opening in the noninverted signal the filter should be detuned towards lower frequency with respect to the probe frequency. Finally, we show that the optimum filter transfer function obtained with the genetic algorithm can be approximated with good agreement using an asymmetric Mach–Zehnder interferometer combined with a Gaussian OBF.

I. Introduction

Wavelength conversion has been investigated extensively in the past several years as it will play an important role in future wavelength division multiplexing optical networks [1]. Wavelength conversion techniques based on semiconductor optical amplifiers (SOA), promising due to their large nonlinearities and potential for integration, have attracted considerable attention [2]. However, relatively long carrier lifetimes (typically tens to hundreds of picoseconds) result in significant pattern effects limitting the maximum pattern-effect-free bit rate.