Low Crosstalk, Based On Banyan Network Nonblocking Optical Switching Fabric Research

The optical switching node as a key equipment for the optical transport network, not only eliminates an expensive optical-electrical-optical conversion, realizes all-optical switching and fills the serious disparity between optical transmission capacity and electronic switching speeds, but also has the advantage of full transparent to optical signal bit-rate, modulation formats and communications protocols. Optical switching fabrics are core components of the optical switching node, providing physical support for optical switching operation, and possessing the primary characteristics such as low crosstalk, uniform loss, internal nonblocking and flexible scalability.According to the above characteristics, several improved nonblocking approaches in this dissertation are proposed to remove the first-order optical switch crosstalk and link blocking to construct low crosstalk and nonblocking spatial optical switching fabrics with less complexity of optical switches from Banyan-type networks based on 2×2 directional coupler optical switch. Furthermore, the proposed optical switching fabrics will be applied to the WDM optical switching fabrics model and various wavelength assignment manners of their inlet-end are analysed. The main contents of the thesis are summarized as follows.First, the function of optical switching node, its general configuration model and the functional modules of configuration are introduced. Simultaneously, a simplified WDM optical switching fabrics model and its spatial optical switching fabrics-related optical switch element, performance assessment indices are explicitly formulated. The properties of Banyan-type networks, low crosstalk and nonblocking dilation approaches, their HC(N, m) network and VS( N , p )optical switching fabrics are also illuminated. The existing conclusions of Banyan-type networks-based optical switching fabrics are concisely described.Next, for the VS( N , p )optical switching fabrics, a principle of wavelength assignment of the inlet-end is given to prove and calculate the low crosstalk and rearrangeable nonblocking condition p when using the conjunction of space and wavelength dilation approaches. The obtained condition p≥2 ?? n2??is less than or equal to the existing one p≥2^[( n+1)/2], where, n = log₂^N and [x] denoting the integer part of x. Taking advantage of edge coloring algorithm for bipartite graph, the routing of any full permutation within VS( N , p )optical switching fabrics is achieved. The specific w-f wavelength assignment manner is addressed while designing an f×f w-wavelength WDM VS( N ,2^[n/2])optical switching fabrics.Then, on the issue of low crosstalk and rearrangeable nonblocking from HC(N, m) network, the reason for exclusively considering even n-m is clarified, such that the novel HVM( N , m, 2^(n-m-2)/2)fabrics are established with internal 2^(n-m-2)/2-layer stacking scheme based on HC( N , m )network. Moreover, low crosstalk and rearrangeable nonblockingVHV( N , m )optical switching fabrics can also be built by utilizing double HVM( N , m, 2^(n-m-2)/2fabrics under straight vertical stacking. Compared with existing VH( N , m, 2^(n-m+1)/2optical switching fabrics, VHV( N , m )optical switching fabrics have less total number of optical switches and gain a competitive edge.Finally, there are some redundant optical switches and links when space dilation approach is adopted to accomplish nonblocking fabrics from Banyan-type networks. To avoid the redundancy, a method for double-end (DE) pruning Banyan-type networks is presented and the remainder can be used for recursively constructing two classes of strictly nonblocking DE-module, namelyDEM-αandDEM-β. Due to the requirement of scalability of f×f w-wavelength WDM optical switching fabrics, based on the famous Clos network, four distinct inlet-end wavelength assignment manners and each corresponding to one mode of different selections of DEM-αandDEM-βas the modules in Clos network have been discussed. Ultimately, three fabrics, Clos-(β,1) network, Clos-(β,2) network and Clos-(β,3) network with low crosstalk and nonblocking are obtained and show less total number of optical switches than WDM VS( N ,2^[n/2])optical switching fabrics.