Studies On Key Technologies In Optical Packet Switching

It is generally recognized that optical packet switching (OPS) is the key to the success of the next-generation optical networks due to its high data rate, high switching efficiency, transparency to data modulation format and flexible control. However, since it is impossible to construct practical optical random access memory (RAM) buffer nowadays, the contention is very serious in OPS. Besides, all the optical label processing schemes nowadays have their inherent shortcomings. Therefore, contention resolution and label processing are two key issues in OPS.To resolve contention, proposals on OPS's network layer, node layer and device layer are given, respectively. On the network layer, the network global control strategy is proposed, and then a slotted OPS networks with no contention can be realized. On the node layer, a buffer structure with output-aware buffering and variable delay buffer is proposed. Then optical RAM buffering can be equivalently realized at the core nodes in OPS. On the device layer, a class B slow light buffer based on semiconductor optical amplifier (SOA), and a broadband tunable optical delay scheme based on real-time Fourier transformation and ramp-type phase modulation are proposed, both of which do not have the delay-bandwidth product limit. In the tunable delay scheme, the setup is very simple; the signal distorts little after delay and nine times of pulse width delay is achieved.For label processing, firstly, using semiconductor optical amplifier based Mach-Zehnder interferometer (SOA-MZI), an all-optical label stripping scheme is realized. The stripping process is self-controlled without any synchronization process. Simulation results show that the code information in the stripped and remained label can be perfectly preserved. Besides, the stripping results deteriorate little when considering the devices'non-ideal performance in practice. And in the real multi-hops OPS networks, the penalty caused by the deterioration of the code information in the optical code (OC) label at each hop is acceptable. After that, four multi-bit OC label schemes are given: the cascaded OC label which can realize routing with only label recognition process; the stacked OC label which can support all-optical multicasting with a simple node structure; the cyclic postfix technique which enable stacked OC label to multiplex arbitrary number of basic codes; and the multi-sampling stacked OC label which can significantly increase label's information capacity. Finally, the parallel-to-cascading multi-bit OC label processing technique is proposed. At the transmitter end, the packet has low overhead cost; and at the receiver end, the label's multi-bit information is converted into low speed autocorrelation peak (ACP) pattern, making it easy to be optically or electronically processed to generate the control signal. The label's correlation performance can be increased by using our proposed multi-polar inserting zeros (MIZ) code. The node's physical structure can be significantly simplified since only one encoder, one decoder and one photo detector (PD) are needed.