Research On CLOS-Type Nonblocking WDM Optical Switching Networks With Reduced Hardware Cost

Compared to traditional electronic switching networks, wavelength division multiplexing (WDM) optical switching networks can provide not only much faster connections, but also much richer communicational patterns according to diverse network applications. Clos network is a preferred solution to realize nonblocking WDM optical switching networks thanks to its regular structure and good scalability. Therefore, researching on Clos-type nonblocking WDM optical switching networks with reduced hardware cost is of great significance both in theory and application.This dissertation focuses on how to reduce hardware cost of Clos-type nonblocking WDM optical switching networks. In summary, the major contributions of this dissertation are as follows:(1) Based on the traditional architecture in which space switching module and wavelength conversion module are separate, two Clos-type nonblocking WDM multicast optical switching networks are proposed. One is called CWMNA, which is three-stage strictly nonblocking (SNB). And the other is called CWMNB, which is four-stage wide-sense nonblocking (WSNB). We present the constructing approach of the two networks under wavelength model, and then optimize their hardware cost by the necessary and sufficient nonblocking conditions we proved.(2) A novel optical switching element, called Space Switching and Wavelength Conversion Element (SWE), is proposed. We present the structure and states of SWE by its design principle and implementation. We also give the wavelength distinction and wavelength specificity conditions which SWE has to follow. Analysis shows that SWE can combine the process of space switching and wavelength conversion, so as to replace WC to construct novel WDM optical switching networks, which can abandon the traditional architecture that induces many problems of performance and hardware cost.(3) Based on SWE, two novel nonblocking WDM crossbar networks, called SWCS and SWCS-S separately, are proposed. Both consisted of SSE and SWE, SWCS is constructed by matrix method, while SWCS-S is constructed by broadcast-select method. We present their nonblocking characteristics and routing strategy, and then calculate hardware cost. Compared to other existing counterparts, the proposed networks do not need extra wavelength conversion module, so as to obtain a better balance between the cost of space switching and wavelength conver-sion.(4) A new series of Clos-type nonblocking WDM optical permutation networks, which adopt SSCS, SWCS and SWCS-S as basic units, are proposed. These networks not only keep the advantage of SWCS and SWCS-S, but also effectively reduce the hardware cost and support efficient routing algorithms. Results from theoretical analysis demonstrate that when the size of the network increases, the hardware cost of CWPNB-FM2 network can be reduced to about 70%of that of the best-known Clos-type nonblocking WDM optical permutation network. Therefore, CWPNB-FM2 is a much more cost-effective WDM networking option.