Demonstration of an optical full adder and subtractor for phase-encoded data using nonlinear wave mixing

The full adder (FA) and full subtractor (FS) are key operations used in the arithmetic and logic units of digital processors. Performing the FA and FS optically may enable the direct line-rate processing of high-speed optical data. Previous demonstrations of optical FA and FS have not been shown for phase-encoded input and output data signals. Such phase-encoded data formats could offer improved noise tolerances and longer distances of transmission compared to amplitude-encoded data formats. In this work, we experimentally demonstrate an optical FA and FS for binary-phase-shift-keying (BPSK) data signals at 2.5- and 5-Gbit/s. Our approach utilizes input BPSK data signals and continuous-wave pumps that are encoded at different frequencies, in which one of the input BPSK data signals is negated for the FS case. The data and pumps undergo nonlinear wave mixing in a periodically poled lithium niobate (PPLN) waveguide to generate the FA or FS BPSK outputs at different frequencies. The experimental results show error-free logic operation for both the FA and FS outputs at 2.5- and 5-Gbit/s over 1536 captured bits.