Joint Probabilistic-Nyquist Pulse Shaping for an LDPC-Coded 8-PAM Signal in DWDM Data Center Communications

Han Han,Yang Yang,Yue Yue,Wang Wang,Anderson Anderson,Qu Qu,Djordjevic Djordjevic

doi:10.3390/app9234996

Han Han, Yang Yang + Show 5 more

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https://doi.org/10.3390/app9234996

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Abstract

M-ary pulse-amplitude modulation (PAM) meets the requirements of data center communication because of its simplicity, but coarse entropy granularity cannot meet the dynamic bandwidth demands, and there is a large capacity gap between uniform formats and the Shannon limit. The dense wavelength division multiplexing (DWDM) system is widely used to increase the channel capacity, but low spectral efficiency of the intensity modulation/direct detection (IM/DD) solution restricts the throughput of the modern DWDM data center networks. Probabilistic shaping distribution is a good candidate to offer us a fine entropy granularity and efficiently reduce the gap to the Shannon limit, and Nyquist pulse shaping is widely used to increase the spectral efficiency. We aim toward the joint usage of probabilistic shaping and Nyquist pulse shaping with low-density parity-check (LDPC) coding to improve the bit error rate (BER) performance of 8-PAM signal transmission. We optimized the code rate of the LDPC code and compared different Nyquist pulse shaping parameters using simulations and experiments. We achieved a 0.43 dB gain using Nyquist pulse shaping, and a 1.1 dB gain using probabilistic shaping, while the joint use of probabilistic shaping and Nyquist pulse shaping achieved a 1.27 dB gain, which offers an excellent improvement without upgrading the transceivers.

Highlights

In view of the current development of the annual growth rate of data center transmission, the widely used coherent optical communication [1,2,3,4,5] is moving toward the data center networks market, but has not dominated because of its high cost, high power consumption, and implementation complexity
We found that a smaller roll-off factor (ROF) could provide a better bit error rate (BER) performance, and to optimize the probabilistic shaping (PS) performance, we needed to consider both the signal entropy and the error correction capability of an low-density parity-check (LDPC) code
We have shown that the optimization was not highly sensitive to either the ROF

Summary

Introduction

In view of the current development of the annual growth rate of data center transmission, the widely used coherent optical communication [1,2,3,4,5] is moving toward the data center networks market, but has not dominated because of its high cost, high power consumption, and implementation complexity. To compensate for the performance loss, in recent years, a constellation shaping scheme has attracted increasing research attention, which include geometric shaping (GS) [12,13,14,15,16,17], probabilistic shaping (PS) [18,19,20,21,22,23], and hybrid geometric-probabilistic shaping [24,25,26,27].

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