Design of all-optical T-gate and quaternary subtractor circuit

All-optical data processing technology has the strong potential to reach the goal of ultra fast data processing for the present and coming generation. But use of conventional binary logic based operation degrades the expected speed because of the limitation of data representation scheme based on only two states. A very promising approach to deal with enormous amount of data with a very high speed is switching to Multi Valued Logic (MVL) from conventional binary logic based operation in the optical domain. In this article the authors have designed all-optical T-gate, a universal gate in quaternary logic system with radix-4, and an all-optical quaternary subtractor have also been developed using the T-gates. The basic building unit used to make these circuits are Semiconductor Optical Amplifiers (SOA). The property of polarization switching and frequency routing properties of SOA have been exploited in the present scheme. Here the authors have encoded every data bit with a particular frequency of an optical signal. The utility of the frequency encoding technique is that the value of frequency encoded data remains unchanged during transmission, and thereby bit error problem can be significantly reduced. The corresponding simulation results hike the acceptability of the proposed scheme.