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Overview of high-speed TDM-PON beyond 50 Gbps per wavelength using digital signal processing [Invited Tutorial]

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Overview of High-Speed TDM-PON beyond 50 Gbps
per Wavelength using Digital Signal Processing
[Invited/Tutorial]
PABLO TORRES-FERRERA1,2,*, FRANK EFFENBERGER3, MD SAIFUDDIN FARUK1, SEB
J. SAVORY1, ROBERTO GAUDINO2
1Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge CB3 0FA, United Kingdom.
2Department of Electronics and Telecommunications, Politecnico di Torino, 10129 Turin, Italy.
3Futurewei Technologies, Inc., Plano, TX 75024, United States of America.
*Corresponding author: pt449@cam.ac.uk
Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX
The recent evolution of Passive Optical Network (PON) standards and related research activities for physical layer
solutions achieving bit rates well above 10 Gbps per wavelength () is discussed. We show that the advancement
toward 50, 100 and 200 Gbps/ will for sure require a strong introduction of advanced digital signal processing
(DSP) technologies for linear, and maybe nonlinear, equalization, and for forward-error correction (FEC).
We start by reviewing in detail the current standardization activities in the International Telecommunication Union
(ITU)-T and the Institute of Electrical and Electronics Engineers (IEEE), and then we present a comparison of the DSP
approaches for traditional Direct-Detection (DD) solutions and for future Coherent Detection approaches.
http://dx.doi.org/10.1364/JOCN.99.099999
1. Introduction
In this paper, we review the recent research and standardization steps
towards the development of higher-speed PON physical layer, following
the evolution for bit rates well above 10 Gbps/.
The paper is organized as follows. We begin with a section (Section
2) that provides an in-depth overview on the evolution of PON market
and standardization. Within this overview section there is a specific
focus on bit rate standardization for 25 and 50 Gbps/, showing the
resulting progressive introduction in these standards of DSP
functionalities. The following section (Section 3), details DSP-based
solutions that have been proposed recently at the research level for 100
Gbps/ direct-detection (DD) PON. This is then contrasted in the next
section (Section 4) with approaches for 100 Gbps/ and beyond based
on Coherent PON, including means of simplifying coherent receivers
with a view of reducing cost and DSP power consumption. We then
conclude in Section 5 with a final discussion on the ongoing PON trends.
2. Overview of PON standardization
A. Overview of market status and deployment
The deployment progress of PON is remarkable. Since its initial mass
deployments began circa 2004, the technology has grown to approach
a billion users worldwide by 2021. It now surpasses digital subscriber
line services in number of users, and this will only increase as more
networks are upgraded worldwide by their operators. Through this
development, system standards have been very important, due to the
special practical and commercial characteristics of broadband access. In
short, access networks are a huge investment, and are composed of
millions of cables and associated equipment distributed over a wide
area. This makes low cost, high volume, and supply-chain reliability key
aspects for PON systems. By standardizing the system, multiple vendors
can build compliant products that multiple operators can use in an
interoperable way. Over time, this has been shown to reduce costs
through efficiencies of scale and free market economics. It makes the
business more stable since there are multiple vendors and operators,
and therefore no single entity is critical.
Over the last 20 years, ITU-T and IEEE have been very active in this
field. In particular, the ITU-T study group SG-15 (question Q2) has
standardized many PON systems [1]. The early systems like
asynchronous transfer mode (ATM)-PON were almost experimental
and never reached significant volume. The first system that had over 1
million users was broadband PON (B-PON, ITU-T G.983 series), due to
its deployment in Japan and the United States [2]. However, B-PON was
quickly overtaken by Gigabit PON (G-PON ITU-T G.984 series), and G-
PON is the system that has taken PON to the billion level now [3]. G-PON
delivers 2.5 Gbps downstream and 1.25 Gbps upstream. Its widespread
adoption caused the industry to realize that the optical distribution
network (ODN) is a huge investment that is intended to work for many
decades. This directly led to the consideration of PON coexistence,
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