An array (48, 49, 50, 51 ) of fiber optic couplers coupling an input (45) and an output (46) waveguide. The output waveguide (46) is routed among the couplers of the array such that either backward or forward coupling exists. With backward coupling, energy coupled into the output waveguide (46) in a coupler of the array is guided back to the preceding coupler for coupling back into the input waveguide (45). The backward coupling allows recirculations to occur between couplers to create poles and zeroes in the transfer function of the array which transfer function can be programmed or tailored somewhat to have specific characteristics. Further, the backward coupling allows the array to be used for matrix-vector multiplication.