All-optical switches based on Mach-Zehnder configuration with improved extinction ratios

We study driving conditions to improve the extinction ratios in 2/spl times/2 and 1/spl times/2 all-optical switches based on semiconductor optical amplifiers in Mach-Zehnder configuration. In 2/spl times/2 switches, the optimization of the relative phases of both arms of the interferometer together with the introduction of an optical push-pull lead to enhanced and symmetrical extinctions. In 1/spl times/2 switches, perfect extinctions can theoretically be obtained by adapting the splitting ratios of the input and output couplers to the saturation behavior of the amplifiers.