Volterra series based blind equalization for nonlinear distortions in short reach optical CAP system

• The blind VNLE for CAP modulation is a simple extension to the linear equalizers.
• Two blind VNLE schemes using MCMMA and DD-LMS are investigated experimentally.
• Blind schemes benefit from the unnecessary training symbols and shorter memory length.

In this paper, we propose a blind Volterra series based nonlinear equalization (VNLE) with low complexity for the nonlinear distortion mitigation in short reach optical carrierless amplitude and phase (CAP) modulation system. The principle of the blind VNLE is presented and the performance of its blind adaptive algorithms including the modified cascaded multi-mode algorithm (MCMMA) and direct detection LMS (DD-LMS) are investigated experimentally. Compared to the conventional VNLE using training symbols before demodulation, it is performed after matched filtering and downsampling, so shorter memory length is required but similar performance improvement is observed. About 1 dB improvement is observed at BER of 3.8×10−3 for 40 Gb/s CAP32 signal over 40 km standard single mode fiber.