There has been difficulty in achieving a fully parallel, digital optical adder or multiplier. The primary obstacle is the carry operation inherent in any fixed-radix number system. The concepts of residue number representation and symbolic substitution can be combined to produce a parallel optical arithmetic/logic unit.
© 1988 Optical Society of America
C. David Capps, R. Aaron Falk, and Theodore L. Houk, "Optical arithmetic/logic unit based on residue arithmetic and symbolic substitution," Appl. Opt. 27, 1682-1686 (1988)