Experimental Demonstration of an Optical Second-Order Volterra Nonlinear Filter using Wave Mixing and Delays to Equalize a 20-Gbaud 4-APSK Channel

We demonstrate an optical second-order Volterra filter using wave mixing and delays. We measure the frequency response and perform the compensation of a nonlinearly distorted 20-Gbaud 4-APSK signal with BER reduction from 8.2×10−3 to 3.2×10−3.