Optical Permutation Network Using Birefringence

Abstract

ABSTRACT The paper describes the architecture of a planar (N X N) optical permutation network consisting of several surface stabilized ferroelectric liquid crystals (SSFLC) sandwiched betweentwo birefringent plates at each stage. The arrangement proposed has some advantages over the permutation arrangements available in the literature. 1. INTRODUCTION Efficient communication among different levels within a digital computer, is recognized to be the key to improve performance for parallel processing tasks. Recently, considerable attention has been directed to using optical technology to improve connections of the devices either on a single module or between modules . This is mainly stimulated by its potential to implement massively parallel architecture, which will occupy less area than their electronic counter­ parts . A comprehensive study oiL the optical interconnects for VLSI systems was first made by Goodman et al . There they discussed the feasibility for implementing different types of optical permutation networks. In this paper, we propose an architecture for a general permutation network using several polariza­ tion based optical switches.Permutation networks have played a major role in the telecommunication switch­ ing systems. Usually large circuit switching networks are composed of several tiny permutation networks. In a (N X N) permutation network, signals of N input lines can be directed to any one of the N output lines. A general permutation network belongs to the class of multistage interconnection networks (MIN). For interconnecting N inputs to N outputs a general permutation network requires 2 stages ( where N = 2 ). Throughout this paper we shall assume that N is an integral multiple of 2. This network has applications in several parallel data processing schemes; for example, in designing of fast algorithms like fast Fourier transform, evaluating polynomials, transposing matrices or for realiza­ tion of sorting networks.The proposed network is constructed from several (2 X 2) port optical exchange boxes or switches. The function of these switches are more or less similar to that of Fredkin gates . For implementing such an optical switching element, we suggest the use of a surface stabilized ferroelectric liquid crystal (SSFI£) device sandwiched between two blocks of uniaxial crystals . In the following section, we discuss the principle of operation of these switches. Section-3 deals with the proposed architecture of the general permutation network. Finally advan­ tages and limitations of the proposed system are discussed in the last section.