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Nonlinear optics has been of increased interest for all-optical signal, data and image processing in high speed photonic networks. The application of multi-valued (nonbinary) digital signals can provide considerable relief in transmission, storage and processing of a large amount of information in digital signal processing. Here, we propose the design of an all-optical system for some basic tri-state logic operations (trinary OR, trinary AND, trinary XOR, Inverter, Truth detector, False detector) which exploits the polarization properties of light. Nonlinear material based optical switch can play an important role. Tri-state logic can play a significant role towards carry and borrow free arithmetic operations. The principles and possibilities of the design of nonlinear material based tri-state logic circuits are proposed and described.

Spread-spectrum communication, with its inherent interference attenuation capability, has over the years become an increasingly popular technique for use in many different systems. In multiuser environment, Gold sequences are an important class of sequences that allow construction of long sequences. To achieve this goal, a modified Gold code generator in all-optical domain using semiconductor optical amplifier based terahertz optical asymmetric demultiplexer (TOAD) is explored in this paper. All-optical Gold code generator circuit realization is TOAD based D flip-flop and exclusive-OR logic gates in a configuration analogous to the standard electronic setup, with properties similar to that of both Gold and Kasami sequences. It is compatible with a multichannel direct sequence spread spectrum system. Numerical simulation confirmed the circuit's feasibility and performance in terms of the choice of the critical parameters. However, the proposed sequence generator circuit is more complex than the existing Gold sequence generator, but it is less complex than the Kasami sequence and has performance better than both.Keywords Terahertz optical asymmetric demultiplexer Á R-S and D-flip-flop Á m-Sequence Á Gold code Á Pseudorandom binary new sequence & Goutam Kumar Maity