Broadband Optical Networks

Delivered by

Dr. Erna Sri Sugesti

22 November 2018

Agenda

• Fiber Optics System- Overview

• PON Technologies and Developments

Fiber optics - overview

PONs Slide 4

© = sin¯ (n2/n1)1

V =c/n

t = L·n/c

t = Propagation Time

t Vacuum: n=1, t=3.336ns/m

t Water : n=1.33, t=4.446ns/m

Total Internal Reflection

in Step-Index Multimode Fiber

Multimode Graded-

Index Fiber

Single-mode

Fiber

Types of Optical Fiber

Popular Fiber

Sizes

• Click to edit Master text styles

– Second level

• Third level– Fourth level

Optical Loss versus Wavelength

Total Dispersion

Multimode Dispersion

Chromatic Dispersion

Material Dispersion

Sources of Dispersion

1 0 11

Multimode Dispersion

1 11 11 11

Dispersion limits bandwidth in optical fiber

1 0 11

Graded-index Dispersion

1 10

PONs Slide 10

1 0 1 1 10

In SM the limit bandwidth is caused by chromatic dispersion.

1

Single-Mode Dispersion

How to calculate bandwidth?

Tc = (20ps/nm * km) * 5nm * 15km = 1.5ns

Tc = Dmat * * L

Tc = (20ps/nm * km) * 0.2nm * 60km = 0.24ns

For Laser 1550nm Fabry Perot

For Laser 1550nm DFB

For a 1.25 Gb/s we need a BW of 0.7 BitRate = 1.143ns

System Design Consideration

Material Dispersion (Dmat)

PONs Slide 13

LASER/laser diode: Light Amplification by Stimulated Emission of Radiation. Done of the wide range of

devices that generates light by that principle. Laser light is directional, covers a narrow range of

wavelengths, and is more coherent than ordinary light. Semiconductor diode lasers are the standard light

sources in fiber optic systems. Lasers emit light by stimulated emission.

Spectral Characteristics

Laser

W

Laser Optical Power Output vs. Forward Current

PIN DIODES (PD)

- Operation simular to LEDs, but in reverse, photon are converted to electrons

- Simple, relatively low- cost

- Limited in sensitivity and operating range

- Used for lower- speed or short distance applications

AVALANCHE PHOTODIODES (APD)

- Use more complex design and higher operating voltage than PIN diodes

to produce amplification effect

- Significantly more sensitive than PIN diodes

- More complex design increases cost

- Used for long-haul/higher bit rate systems

Light Detectors

Wavelength-Division Multiplexing

WDM Duplexing

PASSIVE OPTICAL NETWORKS (PON) TECHNOLOGY AND DEVELOPMENTS

BMCDR = Burst Mode Clock Data Recovery

OLT = Optical Line Termination

ONU = Optical Network Unit

Basic Configuration of PON

Typical PON Configuration and Optical Packets

Access network bottleneckhard for end users to get high datarates because of the access bottleneck

local area networks

• use copper cable• get high datarates over short distances

core networks

• use fiber optics• get high datarate over long distances• small number of active network elements

access networks (first/last mile)

• long distances– so fiber would be the best choice

• many network elements and large number of endpoints – if fiber is used then need multiple optical transceivers– so copper is the best choice– this severely limits the datarates

coreaccess

LAN

Fiber To The CurbHybrid Fiber Coax and VDSL

• switch/transceiver/miniDSLAM located at curb or in basement• need only 2 optical transceivers but not pure optical solution• lower BW from transceiver to end users• need complex converter in constrained environment

N end userscore

access network

feeder fiber

copper

Fiber To The Premiseswe can implement point-to-multipoint topology purely in optics

• but we need a fiber (pair) to each end user

• requires 2 N optical transceivers

• complex and costly to maintain

N end userscore

access network

An obvious solutiondeploy intermediate switches • (active) switch located at curb or in basement• saves space at central office• need 2 N + 2 optical transceivers

N end userscore

access network

feeder fiber

fiber

The PON solutionanother alternative - implement point-to-multipoint topology purely in optics• avoid costly optic-electronic conversions • use passive splitters – no power needed, unlimited MTBF• only N+1 optical transceivers (minimum possible) !

1:2 passive splitter

1:4 passive splitter

N end users

feeder fiber

core

access network

typically N=32

max defined 128

PONs Slide 26

PON advantagesShared infrastructure translates to lower cost per customer

• minimal number of optical transceivers

• feeder fiber and transceiver costs divided by N customers

• greenfield per-customer cost similar to UTP

Passive splitters translate to lower cost

• can be installed anywhere

• no power needed

• essentially unlimited MTBF

Fiber data-rates can be upgraded as technology improves

• initially 155 Mbps

• then 622 Mbps

• now 1.25 Gbps

• soon 2.5 Gbps and higher

PONs Slide 27

PON

architecture

PONs Slide 28

TerminologyLike every other field, PON technology has its own terminology

• the CO head-end is called an OLT

• ONUs are the CPE devices (sometimes called ONTs in ITU)

• the entire fiber tree (incl. feeder, splitters, distribution fibers) is an ODN

• all trees emanating from the same OLT form an OAN

• downstream is from OLT to ONU (upstream is the opposite direction)

downstream

Optical Network Units

upstream

Optical Distribution NetworkNNI

Terminal Equipment

UNI

coresplitter

Optical Line Terminal

Optical Access Network

PON types

many types of PONs have been defined

APON ATM PON

BPON Broadband PON

GPON Gigabit PON

EPON Ethernet PON

GEPON Gigabit Ethernet PON

CPON CDMA PON

WPON WDM PON

in this course we will focus on GPON and EPON (including GEPON) with a touch of BPON thrown in for the flavor

Bibliography• BPON is explained in ITU-T G.983.x

• GPON is explained in ITU-T G.984.x

• EPON is explained in IEEE 802.3-2005 clauses 64 and 65– (but other 802.3 clauses are also needed)

EPONBPONGPON

PON principles(Almost) all PON types obey the same basic principles

OLT and ONU consist of

• Layer 2 (Ethernet MAC, ATM adapter, etc.)• optical transceiver using different s for transmit and receive• optionally: Wavelength Division Multiplexer

downstream transmission

• OLT broadcasts data downstream to all ONUs in ODN• ONU captures data destined for its address, discards all other data• encryption needed to ensure privacy

upstream transmission

• ONUs share bandwidth using Time Division Multiple Access• OLT manages the ONU timeslots• ranging is performed to determine ONU-OLT propagation time

additional functionality

• Physical Layer OAM• Autodiscovery• Dynamic Bandwidth Allocation

GPON, xGPON, Radio over Fiber

Dr. Erna Sri Sugesti

BACKGROUND

PON TECHNOLOGY DEVELOPMENT

APON/BPON AND G-PON

ATM-PON and ITU-T G.983

All ITU PON standards feature three classes of optical transmission layer designs with different ODN (Optical Distribution Network) attenuations between ONU and OLT. The three classes are specified in ITU-T G.982 as:• Class A: 5–20 dB• Class B: 10–25 dB• Class C: 15–30 dBClass C design is a very demanding power budget requirement for a passive fiber plant. For practical implementation yield and cost reasons, Class B+ with 28-dB attenuation was later introduced by most PON transceiver vendors

G-PON and ITU-T G.984To better cope with the changes in communication technologies and meet fast-growing demand, ITU-T created the G.984 series standards for PONs with Gigabit capabilities, or G-PON

ITU-T G.984.1 gives a high-level overview of G-PON components and reference structure. G-PON PMD layer or transceiver requirements are covered by the ITU-TG.984.2 standard. Similar to APON, G-PON also defined single-fiber and dual-fiber PMDs. The bit rates defined in G.984 are:• Downstream: 1244.16 Mbps/2488.32 Mbps• Upstream: 155.52 Mbps/622.08 Mbps/1244.16 Mbps/2488.32

Mbps

As the bit rate advances into the gigabit regime, PON optical layer starts to become challenging. First, to cover the full 20-km transmission distance, multilongitudinal-mode (MLM) lasers cannot be used at ONU any more in order toavoid excessive dispersion penalty.

Second, to cover the loss budget requirements for Class B (10–25 dB) and Class C (15–30 dB) fiber plants, more sensitive avalanche photo-diodes (APDs) are required instead of the lower cost PIN receivers. Without proper protection circuits, APDs are susceptible to damages due to avalanche breakdown if the inputs optical power becomes too high.

XGPON

XG-PON means• Full compatibility with G-PON — by virtue of a wavelength

plan, blocking filters and loss budget that allow coexistence on a common PON infrastructure

• Support for single-sided and mid-span reach extension, with reach of up to 60 km

• Full service support — including voice, TDM, Ethernet (up to Gigabit rates), xDSL, wireless backhaul

• Powerful Operation Administration Maintenance and Provisioning (OAM&P) capabilities providing a feature-rich service management system

• Advanced security features including authentication, rogue detection and information privacy

• Power-saving features on top of the already considerable power-efficient nature of fibre access

G.987 — 10-Gigabit-capable passive optical network (XG-PON) systems: Definitions, abbreviations and acronyms

Establishes common terms and acronyms used in the G.987 series, as well as delineates various optical access topologies.

G.987.1 — 10-Gigabit-capable passive optical network (XG-PON) systems: General requirements Lists system-level requirements for XG-PON systems. Most significantly, the XG-PON system can coexist with a G-PON system on the same ODN. Provides examples of the wide variety of SNIs, UNIs and system configurations possible.

G.987.2 — 10-Gigabit-capable passive optical network (XG-PON) systems: Physical media dependent (PMD) layer specification

Defines the physical layer interface specifications for the system operating at the nominal data rates of 10 Gbit/s downstream, 2.5 Gbit/s upstream.

RADIO OVER FIBER

F. Aurzada, M. Scheutzow, M. Reisslein, N. Ghazisaidi, and M. Maier, IEEECapacity and Delay Analysis of Next-GenerationPassive Optical Networks (NG-PONs), IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 59, NO. 5, May 2011

References:

• C. F. Lam, Passive optical networks : principles and practice, Elsevier, 2007.

• Fiber in The Data Center II: Another Lightwave Study, Webinar, May 7, 2014

• Some figures are downloaded from several sources in the internet