An optical systolic finite impulse response (FIR) filter (or convolution operation) implementation using barrel shifters and a Modified Signed-Digit (MSD) adder is proposed in this paper. The computational element used in systolic FIR filters in electronics consists of a multiplier and an accumulator. A speed-up in the throughput data rate can be achieved along with a high degree of regularity and concurrency by replacing the multiplier with barrel shifters and accumulators. The basic cell for the optical implementation consists of a barrel-shifter, an intensity-to-polarization converter and an optical MSD adder. The principle underlying barrel-shifting is the same as that of an optical matrix-vector multiplier. The Liquid crystal light valve (LCLV) structure forms the switching matrix whose elements are determined by the number of shifts specified and also the specified output precision. All barrel shifters in the architecture are implemented using different areas on the same LCLV structure. The MSD adder is implemented using symbolic substitution logic (SSL) and the input operands in the various cells are arranged on the same input data plane to give all the required summation terms.The optical implementation of the above architecture offers reconfigurability together with the inherent speed and massive parallelism of optics. It is shown that a FIR filter of order eight can be implemented using one LCLV and one optical MSD adder.
P. A. Ramamoorthy,
"Optical Implementation Of Systolic FIR Filters", Proc. SPIE 0827, Real-Time Signal Processing X, (25 November 1987); doi: 10.1117/12.942062; https://doi.org/10.1117/12.942062