Semiconductor Optical Amplifier Dynamics for Wavelength Conversion Applications

Abstract

The data exchange efficiency of distributed optical information processing systems can be greatly spurred by the use of optical wavelength conversion (OWC). Based on the nonlinear optical effect of gain or absorption saturation, OWC can be carried out using the cross-phase or cross-gain modulation effects. Although OWC can in principle be performed in multi-level saturable-media, semiconductor optical amplifiers (SOAs) are preferred due to the broad spectrum, high gain, large nonlinearity, and fast effective carrier lifetime (τ) that they exhibit. The latter characteristic is particularly relevant since the conversion data sequence is limited by the speed of the SOA. In this contribution our measurements of τ in bulk InGaAsP/InP SOAs will be shown. They were performed at different levels of saturation on short and long amplifiers, where a τ as small as 60 ps for the long SOA was found. Additionally, a theoretical analysis of the experimental results in the light of a recently developed SOA model will be presented. Albeit its relative simplicity, our transient model takes into account a space and time-dependent carrier lifetime, the presence of the often disregarded amplified spontaneous emission and the nonlinear gain compression effect produced by carrier heating and spectral hole burning. The dynamical gain response of a SOA to a pulse sequence is also important for practical high-bit-rate applications. Therefore, corresponding curves at GHz data rates will be presented, and cross-phase modulation simulations that show the influence of τ as limiting factor on the performance of wavelength converters will be discussed.