Tuesday, 4 July 2006 - 12:00 AM
DEVIP-49

Pure non-blocking matrix LC optical switch for all-optical fibre networks

Yuri P. Panarin and Vimal Alex. School of Electronic & Communication Engineering, Dublin Institute of Technology, Kevin Street, Dublin, Ireland

At present, more and more communication transmission infrastructures are based on optical fibre links, while communication switching remains entirely electronic. This limits very high capabilities of optical fibres. In this context, all-optical switching devices play a central role and will be a significant breakthrough on this way. Currently the optical switching is performed by Micro Electro-Mechanical Switches (MEMS), which are based on mechanical movements of the mirrors. This limits the switching speed and lifetime of such optical switches. On the other hand, the optical switching can be easily achieved with help of Liquid Crystals, utilizing a number of different electrooptic effects (e.g. TN, total reflection, holographic, cholesteric mirrors, etc...). Although binary (1-to-2 or 2-to-2) LC based optical switches are well known, they are not yet commercialised. The main reason is follows. In conventional matrix approach to perform non-blocking N to N switching it is necessary to use a matrix with N x N single Switching Elements (SE), each placed on the crosspoint of input and output channels. This crosspoint architecture offers simple control and wide-sense non-blocking switching. Nevertheless it has several key drawbacks * Large number of single switches S = N2. This dramatically increases the total cost of the matrix and complicates its adjustment and reliability. * The light beam is travelling through N switches accumulating extra insertion loss and cross-talk. In other words, even if the single switch's performance is rather fascinating - the total matrix switch performance will be unacceptable. Recently we have suggested and patented new approach for LC based multi-channel matrix optical switch. The main idea of this scheme is a use of conventional LCD technology to perform optical switching. In other words we suggest to use a simple and inexpensive LC matrix (LCM - i.e. matrix LCD without polarizers) in conjunction with lateral displacement beamsplitter (LBS) as a core part of Switching Array (SA). Such LCM, performs parallel and independent switching of all input optical channels (N-to-2N), where one pixel of the matrix performs 1-to-2 binary switching. The matrix optical switch can be assembled by simple stacking several SAs which needs no additional adjustment. The number of SAs in this scheme is just: S=log 2 (N)= log 2 (2n)=n (where N=2n is a number of channels) which is dramatically lower than in the crosspoint architecture (N2). The light beam is travelling through only n (not N !) switches worsening the total performance of the switch in much less extend. Moreover the final performance of the switch can be as good as of a single switch by introducing special "clean-up" stage. This makes possible to use FLCs instead of TN to design a much faster matrix switch with reasonable optical parameters. A simple 4-to-4 version of described architecture was experimentally studied using He-Ne laser and 6 µm TN LCMs corresponding to Mauguins "second minima". Such gap thickness also fits to the "first minima" for IR 1.5 µm wavelength. The detailed description of the proposed matrix switch and experimental results will be presented in the poster session.

See more of Posters - Devices and applications
See more of Technical Program

See more of The 21st International Liquid Crystal Conference (July 2 -- 7, 2006)