Signal recovery based on optoelectronic reservoir computing for high speed optical fiber communication system

Abstract

Signal recovery effects of a channel equalization method based on optoelectronic reservoir computing (RC) are investigated for actual high speed optical fiber communication systems. The RC is implemented numerically by using a Mach–Zehnder intensity modulator with an optoelectronic delay feedback loop. Two optical communication systems with different transmission distances and receivers based on 25G-class optics are built in-lab. 50-Gb/s non-return-to-zero (NRZ) and four-level pulse amplitude modulation (PAM4) signals transmitted by the two systems are recovered by using optoelectronic RC and different combinations of feed-forward equalizer (FFE) with decision feedback equalizer (DFE) and maximum likelihood sequence estimation (MLSE), respectively. Under the same conditions, optoelectronic RC is better than FFE&DFE, and far superior to FFE&MLSE in the equalization performances. When the receiver is a positive–intrinsic–negative or avalanche photodiode, for the NRZ signal, compared with 45-tap FFE and 9-tap DFE, the sensitivity is increased by ∼3.2/3.4 dB; for the PAM4 signal, the sensitivity is improved by ∼4.9/4.6 dB compared with 123-tap FFE and 9-tap DFE. These experimental results show that the optoelectronic RC has excellent performances for signal recovery of different modulation formats and transmission systems.