Ultrafast semiconductor-based all-optical logic for 100 Gbit/s OTDM networks

Ultrafast optical time-division multiplexing (OTDM) networks have the potential to provide truly flexible bandwidth-on-demand at burst rates in excess of 100 Gbit/s for high-end users, high-speed video servers, terabyte media banks, supercomputers, and aggregates of lower speed users. Because 100 Gbit/s channel rates exceed the current speed available from electronics, functions such as slot or packet synchronization, header address comparison, and data rate conversion at OTDM packet routers or network receiver nodes must be achieved using all-optical techniques. Interferometric logic gates based on gain and index nonlinearities in semiconductor optical amplifiers (SOAs) are of particular interest due to their compact size, low latency, low required switching pulse energies, and potential for large-scale integration. One challenge for SOA-based optical switching is gain saturation that leads to pattern-dependent amplitude modulation at the switch output. We demonstrate pulse-position modulation as a viable means for mitigating carrier-induced amplitude patterning and use this data format to implement optical switches capable of stable operation at 100 Gbit/s data rates with low switching energies. We also show that semiconductor-based optical logic gates can be cascaded together to achieve advanced functionality for ultrafast system applications. As an example, we will present our recent implementation of a synchronous OTDM network testbed capable of fully loaded packet transmission. We demonstrate receiver functionality with multi-layered independent all-optical logic to achieve packet self-synchronization, multiple-bit address comparison, and data demultiplexing at channel speeds exceeding 100 Gbit/s.