Semiconductor Optical Amplifiers: Modeling, Signal Regeneration and Conversion

Semiconductor optical amplifiers (SOAs) have found widespread use in optical communications covering the important telecommunications window with optical carrier wavelengths from 1.1 μm up to 1.6 μm. While amplifiers are usually operated in their linear region, the inherent nonlinearities of SOAs can be exploited for all-optical signal processing like signal regeneration, wavelength conversion, and modulation format conversion. For both, linear and nonlinear applications, the onset and the amount of the nonlinear response is important for choosing the proper operating point. In this book a nonlinear SOA model is developed. Measuring the spectra resulting from a pump-probe experiment, the strength of the various nonlinear contributions can be assigned to inter- and intraband carrier dynamics in the semiconductor. The experiments reveal for the first time the importance and the role of two-photon induced free carrier absorption FCATPA – an effect that so far was not properly taken care of. The resulting blue-shifted sideband makes it possible to design a patterning-free all-optical wavelength converter. More generally, this model helps in finding optimal optical filter schemes for wavelength converters, resulting in patterning-free output signals at high bit rates