Experimental demonstration of low complexity hybrid FFE algorithm for strictly band-limited IM/DD system

Abstract

Feed forward equalizer (FFE) has been widely used in high-speed short-haul optical transmission. When system suffers from serious inter-symbol interference (ISI), i.e. low-cost transceiver induced narrow-bandwidth limitation, FFE with large number of taps is necessary, which significantly increases the computational complexity. In this paper, we proposed a hybrid FFE (H-FFE) algorithm with tap delay adjusted between T space and T/2 space. Enabled by the H-FFE and conventional T/2-spaced FFE algorithms, we demonstrated the intensity modulation and direct detection (IM/DD) transmission of 56, 70, and 80 Gbaud PAM4 signals over standard single mode fiber (SSMF) links up to 2, 1 km and 500 m employing the 18 GHz (3 dB) system bandwidth at C band. The experimental results indicate that the proposed H-FFE algorithm has the similar performance with the conventional T/2-spaced FFE algorithm. In addition, using the proposed H-FFE algorithm, the computational complexity is one third of that of the conventional T/2-spaced FFE algorithm.