1 50 -G b/ s S EF DM IM/DD t ra ns mi ss io n using
l og -M AP Viterbi decoding for sh ort reach optic al
l in ks
BAOXIAN YU,
1,3
CHANGJIAN GUO,
2,3,6
LANGYU YI,
2,3
HAN ZHANG,
4
JIE LIU,
1
XIANHUA DAI,
1,7
ALAN PAK TAO LAU,
5
AND CHAO LU
3
1
School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510006, China
2
South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006,
China
3
Photonics Research Center, Department of Electronic and Information Engineering, The Hong Kong
Polytechnic University, Hong Kong, China
4
School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou
510006, China
5
Photonics Research Center, Department of Electrical Engineering, The Hong Kong Polytechnic University,
Hong Kong, China
6
changjian.guo@coer-scnu.org
7
issdxh@mail.sysu.edu.cn
Abstract:
Spectral efficient frequency division multiplexing (SEFDM) can improve the spectral
efficiency for next-generation optical and wireless communications. In this work, we apply
SEFDM in beyond 100-Gb/s optical intensity modulation and direct detection transmissions
and propose a low-complexity logarithmic-maximum-a-posteriori (log-MAP) Viterbi decoding
algorithm to achieve the maximum likelihood (ML) detection. We evaluate the likelihood of
detections using a posteriori probability instead of Euclidean distance by taking both noise and
inter-carrier interference into consideration. In order to balance the performance and complexity,
we then employ Viterbi decoding principle to retain only certain paths with ML detections (a.k.a.,
the surviving paths) while discarding the others during the decoding procedure. Results show
that the proposed log-MAP Viterbi decoding scheme achieves optimal performance due to the
precise likelihood evaluation, which guarantees the retention of the global ML detection. By
using the proposed decoding scheme, the data rate of SEFDM signals can reach 150-Gb/s in
a 2-km standard single mode fiber transmission, using only 28-GHz bandwidth and 16-QAM
modulation. Experimental results show that the 16-QAM modulated SEFDM signal with a
bandwidth compression factor of 0.8 outperforms 32-QAM modulated OFDM, while both signals
have the same bandwidth (28-GHz) and data rate (140-Gb/s), which demonstrate the superiority
of SEFDM in optical short reach applications.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
Driven by the emerging applications such as Internet of Things, big data, cloud computing, etc.,
the ever-increasing demand for high speed in data centers requires short reach optical systems that
operates beyond 100-Gb/s. Recently, it has been reported that the short reach interconnects will
face severe internet traffic in the future [1]. In short reach applications, intensity modulation and
direct detection (IM/DD) is preferred over coherent schemes owing to its simple implementation
and low cost. Conventional schemes achieving the high data rate short reach transmissions
include single carrier pulse amplitude modulation (PAM), discrete multi-tone (DMT), carrier-less
amplitude and phase modulation (CAP), as well as faster than Nyquist (FTN) signaling [2–8].
Spectrally efficient frequency division multiplexing (SEFDM) is another effective scheme to
improve the spectral efficiency (SE), through compressing sub-carriers closer than orthogonal
Vol. 26, No. 24 | 26 Nov 2018 | OPTICS EXPRESS 31075
https://doi.org/10.1364/OE.26.031075
Received 17 Jul 2018; revised 16 Oct 2018; accepted 16 Oct 2018; published 12 Nov 2018