A Programmable 8-bit Optical Correlator Filter for Optical Bit Pattern Recognition

We demonstrate a compact reconfigurable 8-bit optical matching filter fabricated using 4% delta high-index-contrast silica-on-silicon waveguides. This planar lightwave circuit is based on an eighth-order tap-and-delay finite impulse response architecture. Multimode interference-based splitters/combiners along with variable optical attenuators and phase shifters allow us to tune and dynamically reconfigure all the taps and delays (filter coefficients) in the filter using a simple automated algorithm. The filter is designed to recognize 8-bit patterns in 40-Gb/s data streams and we demonstrate its working principle by successfully correlating 8-bit binary phase-shift-keyed patterns.