08 Infrastructures PON [modalità compatibilità]netgroup.diet.uniroma1.it/.../default/files/08_Infrastructures_14.pdf · Network Infrastructures – a.a. 2008-2009 Lecture 0 pag

Network Infrastructures – a.a. 2008-2009 Lecture 0 pag. 1

Network Infrastructures

A.A. 2014-2015Prof. Francesca Cuomo

Towards Fiber to the X (FTTX): Passive Optical Networks

Francesco Matera

Responsabile Area Tecnologie Reti di Nuova Generazione

[email protected] ; +39 06 5480 2215


Outline

• Why FTTx

• How FTTx: PON

• Principles of Optical Fibre Systems

• PON characteristics (APON, BPON, EPON, GPON)

• Future: WDM PON

• Application

• Market (cost, unbundling)

Main source: Project EU E-Photon/One+, Lessons from Prof. A. Pattavina, G. Maier, Politecnico di Milano

Access/backhoul

10 Gbps

1 Gbps

100 Mbps

10 Mbps

1 Mbps

200 m50 m 500 m 1 km 5 km 15 km+

Fiber

Microwave

LMDS

Optical Wireless

xDSL


PSTN access-networkPhysical architecture

Primary network

• High sharing• Cost minimization

Secondary network

• Flexibility• Branching

Cables

• Primary 2400-2000 pairs In duct or pipe

• Secondary 100-10 pairs Trenched or aerial

Cascading more stages of cabinetsis possible but rare

Distribution point (box)Distribution

cabinetPrimary cable

Twisted pairCentral office

Feeder / primarynetwork

Distribution / secondarynetwork

Homenetwork

Dedicated / leased line

Secondary cable

Telecom access networks


Optical Fiber: Attenuation

Single Mode Fiber (SMF) to achieve large distances

• ITU G.652 SMF (STD) “water peak” attenuation renders the 1360nm–1480nm spectrum unusable for data transmission

• ITU G652c/d SMF (ZWP) “zero-water peak”

800 900 1000 1100 1200 1300 1400 1500 1600 1700

0.5

1.0

1.5

2.0

2.5

3.0First

Window SecondWindow

ThirdWindow

ATT

ENU

ATI

ON

(d

B/k

m)

WAVELENGTH (nm)

1310nm

1550nm

850nm

STD SMF

ZWP SMF

Optical Fiber: Chromatic Dispersion

Causes signal pulse broadening

Dispersion

+

-

Wavelength [nm]

Waveguide Dispersion

Total Dispersion

Material Dispersion

1200 1400 1600Zero at 1310 nm

Single-mode optical fiber

Shorter Wavelengths

Longer Wavelengths


Lasers Diodes (LD)

Fabry-Perot (FP)

• Cheap

• Noisy Sensitive to chromatic dispersion

• Used on 1310 nm

Distributed Feedback (DFB)

• More expensive

• Narrow spectral width Less sensitive to chromatic dispersion

• Used on 1550 nm (or 1310 nm)

Simple FP

mirror

gain

cleave

+

-

mirror

gain

AR coating

+

-

DFB

Passive Splitters

1x2 Splitter 1xN Splitter

• The basic element consists of two fibers fused together

• Every time the signal is split two ways, the signal is reduced by 10log(0.5)=3dB

• Loss ~3dB x log2(#ONUs)

3.4dB3.7dBSplitter 1x2Low-loss Conventional


Photodiodes (PD)

PIN Photodiodes

• Good optical sensitivity (-22 dBm)

• Silicon for shorter ’s (eg 850nm)

• InGaAs for longer ’s (eg 1310/1550nm) Avalanche Photodiodes (APDs)

• Higher sensitivity (-30 dBm)

• Primarily for extended distances in Gb/s rates

• Much higher cost than PIN diodes

Transceiver Assumptions

Upstream (@1310nm) Power Budget = 30 dB

Downstream (@1490nm) Power Budget = 22 dB

-22 dBm0 dBmONU (FP+PIN)OLT (DFB+APD) -30 dBm1 dBm

RX SensitivityTX Power


Fiber installation

La microtrincea come semplice ed economica soluzione per la diffusione della fibra ottica nella rete di accesso(from HighBand)

Soffiaggio della fibra (ERICSSON)

30-40 K €/km per microtrincea

DSLAM

Cavo

PrimoArmadio

SecondoArmadio

500-1000 m 100-300 m 50-200 m

Centrale

Switch/Router

PrimoArmadio

SecondoArmadio

a) Best cuurent architecture

DSLAM

Fibra ottica

b) Fiber to the cabinet


Switch/router

PrimoArmadio Secondo

ArmadioFibra ottica

c) Fiber to the curb

DSLAM

Switch/router

PrimoArmadio

SecondoArmadioFibra ottica

d) Fiber to the building

D

Switch/router

PrimoArmadio

SecondoArmadioFibra ottica

e) Fiber to the home


Centraloffice

Centraloffice

Centraloffice

Curbswitch

Splitterottico

a)

b)

c)PON

Access capacities


Core

GbE based: FASTWEB

Daisy chain architecture

First case in Europe:Fastweb 2000FTTH: Accesso Residenziale

FTTB: Accesso Business

Verso la Backbone

RouterPABX

LAN

Technical room

Verso la Backbone

IP switch

HAG

Uplink Fibra


FTTx = Fiber-to-the-x

FTTH - Home

FTTC - Curb

FTTN - Node or Neighborhood

FTTP - Premise

FTTB - Building or Business

FTTU - User

FTTZ - Zone

FTTO - Office

FTTD - Desk

Basic PON operations

The optical line terminal (OLT) broadcasts data downstream on 1,510 nm andthe ONTs burst data back upstream on 1,310 nm in their assigned time slots.


Photonics Evolution

Distanze

10 m 100 m 1 km 10 km 100 km 1000 km e oltre

2008

2010

2015

ADSL2+

VDSL/2 FTTP

VDSL2 FTTB

FTTH Provider backbone transpoortT-MPLS

VPLSMPLS

Optical Packet switching

Optical burst switching

Conversione lunghezza d’onda

GbE SDH

OTN

FTTH

WDM

L3

L2

L1

Time vs. Spectrum Sharing

Downstream point-to-multipoint network

• The OLT manages the whole bandwidth Upstream multipoint-to-point network

• ONUs transmit only towards the OLT

• ONUs cannot detect other ONUs transmissions

• Data transmitted by ONUs may collide

Need of a channel separation mechanism to fairly share bandwidth resources

TDMATime Division Multiple Access

WDMAWavelength Division Multiple Access


PON Overview

TDM-PONs

• Standardized

• Use few wavelengths (typically 2 or 3)

• Low cost and mature devices (splitters, lasers, etc.)

• Limited power budget Maximum distances 20km, Split ratios 64

• Traffic distribution Broadcast scheme in downstream TDMA techniques in upstream

• Examples: APON/BPON, EPON & GPON WDM-PONs

• Proposed in literature and/or demonstrated

• Introduce WDM techniques and devices (AWG)

• Long-reach and bandwidth

• Examples: CPON, LARNET, RITENET, Success-DWA…

Downstream Traffic Scheduling

OLT

A

B

C

Passive Splitter

A B C B A B C B

• OLT schedules traffic inside timeslots -Time Division Multiplexing (TDM) scheme

• Time slots can vary from s to ms


Upstream Traffic

OLT

ONU

ONU

ONU

Passive Splitter

• All ONUs share the same upstream channel ONUs cannot exchange data directly

Collisions may occur at the splitter/combiner

Upstream Traffic Scheduling 2/4

• In general, PON standards propose Time Division Multiplexing Access (TDMA) schemes Upstream time slicing and assignment

OLT

ONU

ONU

ONU

Passive Splitter

B BA B C B


Upstream Frame Reception

• The OLT receives frames with different powers Much difficult to recover synchronism (clock and data recovery)

Burst Mode Receiver (complex) @ OLT• Sets 0-1 threshold on a burst basis

OLT

A

B

C

Passive Splitter

BB A

7 km

3 km

1 km

Automatic Gain Control to adjust 0-1 threshold at the beginning of each received burst

Evolution of the standards

10 GB EPON


Fiber in the loopPON standardization: a brief history

ATM PON (A-PON)

• Traffic is carried using ATM raw-cell format and framing• 1982: idea of PON (British Telecom)• 1987 – 1999: PON testbeds by BT, Deutsche Telekom (Eastern Germany), NTT

(Japan), BellSouth (Atlanta, USA)• 1995: 622 Mbit/s APON testbed (RACE BAF project)• 1996: beginning of Full Service Access Network (FSAN) works• 1997-’98: ACTS BONAPARTE and EXPERT/VIKING projects

Broadband PON (B-PON)

• APON system is standardized by ITU-T with a new name to indicate that thePON can offer full broadband service and not just ATM

• Line rates: 155 Mbit/s symmetrical or 622/155 Mbit/s down/upstream;ONU/OLT max distance: 20 km; max. # ONUs: 64

• 1998-’00: ITU-T G.983.1 (physical aspects) and G.983.2 (ONT managementand control)

• 2001-’02: other ITU-T G.983.x and Q.834.x, e.g. G.983.4/.7: Dynamic Bandwidth Assignment (DBA), providing statistical multiplexing ( more users per ONU) and Quality of Service

(QoS) enforcement G.983.3: adoption of WDM to increase capacity or to carry video signals

Fiber in the loopPON standardization: a brief history

Ethernet PON (EPON)• Traffic is carried using Ethernet framing

Cheaper user equipment then BPON Ethernet much more widespread than ATM

• Higher subscriber rates (up to 1.25 GbE symmetrical), 16 ONU (power budget)• 2001: IEEE 802.3ah Study Group “Ethernet in the First Mile (EFM)”• First documents in Sept. 2003)• 2004: final approval of Standard IEEE 802.3ah

Gigabit-capable PON (G-PON)• Traffic is carried by using different possible framings: ATM (G.983 base) or via

G-PON Encapsulation Method (GEM), which can interface SDH (G.707 base) orEthernet (IEEE802.3 base).

• Various line rates, up to 2.4 Gbit/s symmetrical, ONU/OLT max distance: 20km; max. # ONUs: 64-128

• 2001: activity initiated by the FSAN group• 2003: ITU-T G.984.x


Layer 1: physical layer

Layer 2: data link layer

10Mb/s 100Mb/s 1Gb/s 10Gb/s

IEEE802.2 logical link control

IEEE802.1 bridging

IEEE802.3Ethernet

MAC layer

IEEE802.4Token busMAC layer

802.3ah EFM

Physical layer

IEEE802.5Token ringMAC layer

IEEE802.6MAN

MAC layer

IEEE802.11wireless

MAC layer

Physical layer

Physical layer

Physical layer

Physical layer

• EPON started to be standardized by IEEE 802.3ah EFM since 2001, it

was ratified in 2004

Ethernet Standards in EPONs

Ethernet PONs (EPONs)

All packets carried in EPON are encapsulated in Ethernet frames

• Support for variable size packets Similar wavelength plan to BPON

Maximum bit rate is 1Gbps MAC-MAC (1.25 Gbps at the physical layer with 8b/10bline coding)

Minimum number of splits is 16

Maximum reach is• 10 km (FP-LD @ ONUs, limited by dispersion in downstrea for G.652)

• 20 km (DFB-LD @ ONUs)

Different configurations are allowed


OLT

OLT

OLT

OLT

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

ONU

1) Tree Topology

(2) Ring Topology

(3) Tree with Redundant Trunk

(4) Bus Topology

EPON Configurations

EPON Downstream Traffic

Similar to a shared medium network

Packets are broadcasted by the OLT and selected by their destination ONU

ONU 3

OLT

21 13

Header Payload FCS

802.3 frame

21 13

1 1

2

3

USER 2

USER 3

USER 1

ONU 2

ONU 1


EPON Upstream Traffic

ONU 1

ONU 2

ONU 3

USER 1

OLT

FCSHeader Payload

3

802.3 frame

Time slot

33

333

USER 2

USER 3

222

11

11

ONUs synchronized to a common time reference

Centralized arbitration scheme OLT based

OLT grants access to ONU for a timeslot

• Several Ethernet packets

Frames Buffer

The Multi-Point Control Protocol (MPCP)

Original Ethernet MAC protocol cannot operate properly in the upstream channel(no collision detection) since each ONU cannot hear other ONUs

MPCP (Multi-Point Control Protocol) is a new function of the MAC control sublayer.It is developed to support dynamic capacity allocation but the algorithms are anequipment vendors choice (Dynamic Bandwidth Allocation - DBA)

• In-band signalling• Messages (64 bytes)

GATE REGISTER REGISTER_REQUEST REGISTER_ACK REPORT

4

40

4

2

2

6

FCS

Data/Reserved/Pad

Timestamp

Opcode

Length/Type 88-08

Source Address

Destination Address 6

MSBLSB

b7b0

Octets

Bits within frame transmitted left-to-right

Octets within frame transmitted top-to-bottom


Autodiscovery mode

3 control messages:

• Register, start message sent by OLT;

• Register_Request, answer message from ONUnot registered yet;

• Register_Ack, message by OLT that allowsONU registration.

GPON Standardization

Feb. 2004G-PON TC layer spec.

(Transmission convergence layer specification)G.984.3

Mar. 2003G-PON Physical Layer spec.

(Physical Media Dependent (PMD) layer specification)

G.984.2

Mar. 2003G-PON service requirements

(General characteristics)G.984.1

AdoptionOutlineITU-T


G.984.1 Service Requirements

Downstream video wavelength (1550 –

1560nm) may be overlaid

Downstream: 1480 – 1500nmUpstream: 1260 – 1360nm

Wavelength allocation

Max. 64 in physical layerBranches

Max. 60 kmLogical reach

Max. 20 km or max. 10 kmPhysical reach

1.25Gbit/s symmetric or higher (2.4 Gbit/s). Asymmetric with 155/622Mb/s upstream

Bit rates

TargetItem

GPON Encapsulation Mode (GEM)

GEM provides a Generic Frame where to carry both TDM and packet traffic overfixed data-rate channels

• Similar Generic Framing Procedure (GFP) used inSDH/SONET

A Generic Frame consists of:

• a core header

• a payload header

• an optional extension header

• a payload

• an optional frame check sequence (FCS).


Downstream Frame Structure 1/3

It consists of

• a Physical Control Block Downstream (PCBD)

• the ATM partition (N×53 bytes)

• the GEM partition

PCBdn+1

PCBdn+2

Payload n Payload n+1PCBd

n

TP-Frame = 125 µs

TDM & Data Fragmentsover GEM Section

“Pure” ATM cellsSection

N * 53 bytes

GPON Header


Technical Standards Comparison

Technology Standard Downstream/Upstream Bandwidth # ONT served Lambda Framing/

Protocol Distance

APON/BPON(ATM PON/ BroadbandPON)

ITU-T G.983.x

155, 622 or 1244 Mbit/s down

155 or 622 Mbit/s up

Limited by power budget and ONU addressing limits:

16 to 32 splitter

1490 nm Down

1310 nm Up

(1550 nm Down for RF video )

ATM 20 km

GPON(Gigabit PON) ITU-T G.984

1.2 or 2.4 Gbit/s down

155, 622, 1.2 or 2.4 Gbit/s up

Up to 64(physical)

Up to 128 (logical)

1490 nm Down

1310 nm Up

(1550 nm Down for RF video)

GEM: G-PON Encapsulation

Method (supports Ethernet), ATM

10/20 km (up to 60

km )

EPON

(Ethernet PON)*IEEE 802.3ah Symmetric 1.25 Gbit/s Up to 16

1550 nm Down

1310 nm UpEthernet 10/20 km

10GEPON(10 Gigabit EthernetPON)

IEEE 802.3av (Working

Task Force)

10 Gbit/s down 1 Gbit/s up

(symmetric 10 Gbit/s in the future?)

32 (maybe more?)

1480-1500 nm Down ?

1260-1360 nm Up ?

1550-1560 Video overlay ?

Ethernet 20 km

Transmission Efficiency

0

200

400

600

800

1000

1200

1400

EPON GPON BPON

Mb

/s

scheduling OH : framedelineation

scheduling OH : PHY burst OH

scheduling OH : controlmessages

payload encapulation OH

line coding

payload


Header’s Comparison

Guard Preamble DelimiterGPON

EPON

min. 25.6 ns

typ. 35.2 ns

typ. 16.0ns

min. 76.8 ns

Data

Laser turn on time

AGC, CDRsetting time

Data

max. 400 ns max. 400 ns

Guard Preamble DelimiterBPON

min. 4 bits

typ. 12 bits

typ. 8 bits

24 bits

Data

AGC: Automatic Gain Control; CDR: Clock and Data RecoveryLaser turn on time overlaps the laser turn off time of the previous burst

Laserturn off time

max. 400ns

Data

EPON costs about ~10% the cost of BPON/G

Simple WDM-PON

Number of ONUs limited by wavelengths

Point-to-point topology

Long-reach (almost point-to-point reach)

WDM Receiver

Receiver Array/Optical

Demux

AWG

1 x N

Receiver

ONUsWDM ModulatedSource

OLT

Central Office (CO)

λ1, λ2….λn

λN+1, λN+2….λ2N

λ1

λN+1

λN

λ2N

Transmitter

Receiver

Transmitter

.

.

Filter as Optical router


B type1+1 protection of OLT

C type1+1 protection of PON

Protection Mechanisms

Cost-effective

Redundant feeder

Redundant OLT transceivers Most secure and expensive

Redundant feeder and drops

Redundant transceivers

TR

TR

TR

TR

TR

OLT ONU-1

ONU-2

ONU-n

・・

TR

TR

TR

TRTR

TR

TR

TR

OLTONU-1

ONU-2

ONU-n

・・

Carrier Ethernet for PON (EPON)

Centraloffice

c)PONNetwork

Carrier Ethernet: Processing from level 3 to 2Specific path for QoS

VLANTAG, VPLS, Q-in-Q, MAC in MAC, PBT


Elements of a PON

STB

Rete Domestica

Sede d’UtenteRete SecondariaRete PrimariaCentrale Edificio

F.O.OLT

coppia inrame

coppia inrame

VDSL

VDSL

F.O.

coppia inrame

NTVDSL

F.O.

Cabinet

Curb

Building

Diramatore1:N

NodoATM

Rete CDN

V5.1V5.2

VB5.1VB5.2

PSTN/ISDN

ONU

ONU

OLT: Optical Line

VDSL: Very high bitrate Subscriber Loop

ONU: Optical Network UnitNT : Network Termination

STB: Set Top Box

NT

NT

International development overview

China• GPON and EPON are being tested in China : future PON growth mainly depends on Chinese market

evolution• Beijing, Wuhan, Shanghai e Guangzhou are the cities with the greatest FTTX deployment

Japan• The number of xDSL users has decreased for the first time at the end of 2006, while FTTH users have

grown by 10% in 2006 last trimester.• At the end of 2006, out of 26 million Broadband lines, FTTH accounted for 30% of the total amount.

South Korea• In July 2007, 500.000 FTTH users• Almost 4 million FTTB “apartment LANs”



USA

• Large average cable-length

• Large investments form cable operators, that account for arelevant share of the broadband market

• No unbundling required for new fiber infrastructures. Brazil, Colombia, Argentina, Chile

• Less than 300.000 FTTH users Australia, New Zeeland, Kuwait, Russia, United Arab Emirates, Pakistan

• Less than 2 million FTTH users

Ref: EXFO, may 2007

• Mostly in Northern Europe, local administrations are building the infrastructure, with equal access conditions for service providers

• The leading incumbents are deploying extended FTTCab/VDSL infrastructure plans.

• Sweden: more than 500.000 FTTH users

• France, UK: more than 600.000 FTTH users

• Italy : more than 250.000 FTTH users

• Denmark: more than 400.000 FTTH users

• Holland : more than 500.000 FTTH users



FTTx costs

FUB study on NGN economics

• 1400 Mega Euro for digital Divide end (connection of central office to babckbone)

• FTTC/B/H for all? No 2 Mb/s for all but 20 Mb/s for almost all and >50 Mb/s for many

• 10 million of users based on FTTB: total cost 15000 Mega Euro!

• Unbundling problems: – For OLO no PON, yes Point-to-point

– We say yes PON since:

» with logical unbundling now and WDM later!

» Too cost to include devices in central office and fibres in current ducts

» With PON we can shift OLO location from central office to l t b kb


FUB Experiments on EPON

IP DSLAM

Line Simulator

J2

J3

J1

J4

C1

C2

C3

xDSL Access (ADSL2+)

FTTx Access (EPON)

OLT

ONU1

ONU2

ONU3

ONU4

Fast Ethernet

Doppino telefonico

Roma – Pomezia Anello Ottico 50 Km single mode 1550 nm

Optical link 50 m multi mode 850 nmEPON UP 1310 nmDOWN 1490 nm

IP DSLAM

Line Simulator

xDSL Access (VDSL)

NAS 3640 Switch ATM

ATM DSLAM

Line Simulator

Line Simulator

ATM DSLAM

xDSL Access (ADSL)

xDSL Access (SHDSL)Alcatel

ESS 7450

Juniper M10 e M10i

Cisco 3845

Alcatel ESS 7450

Cisco 3640

FiberHome OLT e ONU

ALCATEL IPDSLAM 7324

ASAM 1000 e 7300

Video Server

Anello ottico sperimentale Roma - Pomezia, distanze variabili tra 50 e 350 Km

Logical network by means of VPLS&VLAN Tagging

Un generatore ditraffico permette uncongestionamento traPE2 e OLT

Ethernet PON FiberHome


Throughput in downstream

Congestione tra PE2 e OLT

Conclusions

• FTTx necessary for NGN

• PON is the best current solution

• Problems for investments and network properties

Documents

08 Infrastructures PON [modalità compatibilità]netgroup.diet.uniroma1.it/.../default/files/08_Infrastructures_14.pdf · Network Infrastructures – a.a. 2008-2009 Lecture 0 pag