We experimentally demonstrate an all-optical digital processing circuit that can perform the full addition of binary optical words. The circuit comprises two coupled all-optical regenerative memories. One memory performs the modulo-2 addition and the other memory generates the carry bits from the addition. The two memories are configured to differ in capacity by a single bit so that the full adder operates in bit-differential mode.
Poustie, A. J., Blow, K. J., Kelly, A. E., & Manning, R. J. (1999). All-optical full adder with bit-differential delay. Optics Communications, 168(1-4), 89-93. https://doi.org/10.1016/S0030-4018(99)00348-X