Self-switching in Mach-Zehnder Interferometers based on SOA phase shifters.

A self-switching mechanism in Mach-Zehnder Interferometers is described. The input light signal is distributed unequally over the branches where Semiconductor Optical Am-plifiers are placed as non-linear phase shifters. Unequal intensities yield a non-linear phase shift. The signals from the two branches are then recombined in an output cou-pler. If pi/2-phase shift is reached, the signals are in phase. This effect can be used in the low-loss optical combiner circuit. In this device the transmission can be improved by more then 2 dB with respect to a passive 3-dB splitter. Fabrication, characterization and performance of the combiners are presented in this paper