Mach-Zehnder interferometer based design of all optical reversible binary adder

In recent years reversible logic has emerged as a promising computing model for applications in dissipation less optical computing, low power CMOS, quantum computing, etc. In reversible circuits there exist a one-to-one mapping between the inputs and the outputs resulting in no loss of information. Researchers have implemented reversible logic gates in optical computing domain as it can provide high speed and low energy requirement along with easy fabrication at the chip level [1]. The all optical implementation of reversible gates are based on semiconductor optical amplifier (SOA) based Mach-Zehnder interferometer (MZI) due to its significant advantages such as high speed, low power, fast switching time and ease in fabrication. In this work we present the all optical implementation of an n bit reversible ripple carry adder for the first time in literature. The all optical reversible adder design is based on two new optical reversible gates referred as optical reversible gate I (ORG-I) and optical reversible gate II (ORG-II) and the existing all optical Feynman gate. The two new reversible gates ORG-I and ORGI-I are proposed as they can implement a reversible adder with reduced optical cost which is the measure of number of MZIs switches and the propagation delay, and with zero overhead in terms of number of ancilla inputs and the garbage outputs. The proposed all optical reversible adder design based on the ORG-I and ORG-II reversible gates are compared and shown to be better than the other existing designs of reversible adder proposed in non-optical domain in terms of number of MZIs, delay, number of ancilla inputs and the garbage outputs. The proposed all optical reversible ripple carry adder will be a key component of an all optical reversible ALU that can be applied in a wide variety of optical signal processing applications.