Hardware Efficient and Chromatic Dispersion Tolerant Symbol-Rate Equalization Scheme for Short-Reach Coherent Transmission System
Qian Xiang, Yanfu Yang, Tianjian Zuo, Qun Zhang, Tingting Zhang, Sen Zhang, Lei Liu, Yong Yao
Abstract
Chromatic dispersion enhanced spectrum aliasing, a nonlinear effect in the frequency domain, is theoretically analyzed under symbol-rate sampling conditions, and the relationship between its nonlinear strength and chromatic dispersion is investigated in detail. To address chromatic dispersion enhanced spectrum aliasing efficiently, a hardware efficient and chromatic dispersion tolerant equalization scheme is proposed to deal with inter-symbol-interference, chromatic dispersion, chromatic dispersion enhanced spectrum aliasing and phase noise simultaneously. Compared with the conventional T/2-spaced adaptive equalizer (AEQ) and symbol-rate AEQ, the proposed scheme can deal with large accumulated chromatic dispersion in a cost-efficient manner, which is extremely attractive for ultra-high baud rate and short-reach coherent optical interconnects. The experimental results also indicate that the proposed scheme can provide more than 3 dB received optical power sensitivity improvement over symbol-rate Sim-AEQ after 20 km fiber transmission links. With 7% FEC threshold, the proposed scheme with the same tap number can provide around 250 ps/nm and 90 ps/nm chromatic dispersion tolerance improvement over symbol-rate Sim-AEQ and conventional T/2-spaced equalization schemes, respectively. Additionally, compared with T/2-spaced 2 × 2 MIMO, the proposed scheme can also save around 50% real value multiplier because of the simplified equalization structure. Consequently, the proposed scheme with high chromatic dispersion tolerance and low complexity can be considered a promising DSP solution for ultra-capacity short-reach coherent optical interconnects such as datacenter interconnects and access applications.