All-Optical Demultiplexing of a 640 Gbit/s OTDM Signal Using Bulk SOA Turbo-Switched Mach-Zehnder Interferometer with Improved Differential Scheme

All-optical demultiplexing of a 640 Gb/s OTDM signal is numerically demonstrated. The proposed architecture is based on a Mach-Zehnder interferometer (MZI) that relies on a bulk semiconductor optical amplifier (SOA) as nonlinear element. A turbo-switch structure is employed in order to accelerate the recovery dynamics of the active interferometric configuration. Moreover, we make use of an enhanced version of the conventional differential scheme. This novel technique allows us not only to set an effective switching window, but also to make the most of it by means of a precise synchronization with the data stream. This can be accomplished by the addition of a variable optical attenuator (VOA) and an extra delay element to the conventional differential scheme configuration. Additionally, the demultiplexed signal experiences optical gain as a consequence of the amplifying nature of this active interferometric device. The proposed structure is simulated to demultiplex different combinations of channels per OTDM signal while maintaining the multiplexed data rate of 640 Gb/s. In all cases, error-free operation is achieved (BER < 1.0×10 ⁻¹³ ), irrespective of the number of channels. The development of faster all-optical photonic circuits based on SOAs, as the one presented here, confirms its potential as a nonlinear processing element.