High-Speed Correlation and Equalization Using a Continuously Tunable All-Optical Tapped Delay Line

We demonstrate a reconfigurable high-speed optical tapped delay line (TDL), enabling several fundamental real-time signal processing functions such as correlation (for pattern search) and equalization. Weighted taps are created and added using optical multicasting and multiplexing schemes that utilize the nonlinear wave mixings in the periodically poled lithium niobate (PPLN) waveguides. Tunable tap delays are realized using the conversion-dispersion technique. In the demonstrated TDL, the amplitude and phase of tap coefficients can be varied, enabling signal processing on amplitude- and phase-encoded optical signals. We experimentally demonstrate the tunability of the TDL in time, amplitude, and phase. We analyze the TDL's theory of operation and present experimental results on reconfigurable pattern search (correlation) on on-off-keyed and phase-shift-keyed signals at data rates of up to 80 Gb/s, as well as equalization for chromatic dispersion.