past, present, and future of fiber-to-the-home solutions

1ADVANCED SYSTEM TECHNOLOGY

STMicroelectronics

Advanced System Technology

Past, Present, and Future of Fiber-To-The-Home Solutions

Joseph Kim, Ph.D.ST Researcher-in-Residence, Stanford Networking Research Center

Special thanks to:AST Optical Networking R&D Team, and Brian Ford of Bell South

ADVANCED SYSTEM TECHNOLOGY 2 Dec. 3, 2001

Goals of This Talk

Review past and present FTTH solutions.Discuss evolution scenarios to WDM PON.Give an idea on what’s really going on in this area.



Outline

Why FTTH?APONEPONSlides from BellSouth: First Day in the Life of FTTHWDM-PON: Evolution of FTTH SolutionsFinal Words


Why Fiber-To-The-Home?

Advantages of fiber as a transmission medium• Greater capacity (> 100 Tbit/s*)• Smaller size and light weight• Immune to electromagnetic interference

Fiber penetration in the networks• Already deployed in the backbone, the WANs, and

the MANs.• Optical Ethernet is being introduced in LANs and

will spread to MANs and WANs.

* Mitra & Stark, Nature, vol 411, June 28, 2001.



APON

Point-to-Point vs. PONFSAN InitiativeCommon Network ElementsSpecificationsFrame FormatsRangingMedium Access ControlBurst Mode ReceptionUNI Signaling and Control FlowsExample – Lucent APON SystemSummary


APON: Point-to-Point vs. PON

Central OfficeAccess SW

(Statistical MUX)

PassiveSplitter

Houses



APON: FSAN Initiative

Goal: To break through the economic barrierMeans: By large-scale introduction of broadband access networks through definition of basic set of common requirementsStandards: ITU-T Recs. G.983.1 & 2• Upcoming extensions

� G.983.3: WDM overlay� G.983.4: Dynamic bandwidth allocation (DBA)� G.983.5: Enhanced survivability (protection)


APON: Common Network Elements

ONU

ONU

ONU

OLT

OLT

OLT

OLT

NTE

NTE

NTE

ONT

SN

SN

SN

SN

ServiceNode

PON HeadEnd Node

LocalExchange

Cabinet

SDH PON ADSL

VDSL

VDSL

UNI

FTTCab

FTTC/FTTBFTTB/FTTH

FTTEx

VB5

HomeCurb

Source: Tom Rowbotham, BT• SN: Service Node • OLT: Optical Line Termination• ONU: Optical Network Unit• ONT: Optical Network Termination• NTE: Network Termination Equipment



APON: Specifications

Symmetrical 155 Mb/s downstream/upstream(Optional) Asymmetrical 622 Mb/s downstream & 155 Mb/s upstreamOptical attenuation ranges• Class B: 10-25 dB• Class C: 15-30 dB

Maximum fiber distance: 20 kmMaximum split ratio: 32 (optional 64)


APON: Frame Formats*

PLOAM1

ATMCell 1 . . . ATM

Cell 27PLOAM

2ATM

Cell 28 . . . ATMCell 54

Tframe = 56 cells of 53 bytes

Contain 53 upstream grants

ATMCell 1

ATMCell 2

ATMCell 3

ATMCell 53

Tframe = 53 cells per frame

3 overhead bytes per cell (guard time, preamble, delimiter)

Downstream frame format

Upstream frame format

* For 155.52/155.52 Mb/s PON

. . .



APON: Ranging

Placing all ONTs at the same virtual distance from the OLT.

Before ranging: physically at different distances

ONT

OLTONT

ONT

After ranging: virtually at the same distance

OLT

ONT

ONT

ONT


APON: Medium Access Control

Based on TDMA with grant mechanism

. . .

Grants

Cells or Minislots

OperationalParameters

ONT

ONT

ONT

OLT

Management



APON: Burst Mode Reception

The following should be done during the short overhead (24 bits at 155.52Mb/s ≈ 154.3 ns):• Threshold level control• Bit synchronization• Cell delineation

t…

From ONT A

…

From ONT B

…

From ONT C


APON: UNI Signaling and Control Flows

TerminalEquipment

ONT OLTServiceNode

B-ISDN User-Network Signaling (Q.2931 etc.)

BBCC (VB5.2, concentration)

OMCC

IFPON SNI NNIUNI

• RTMC: Real Time Management Co-ordination• BBCC: Broadband Bearer Channel Control• OMCC: ONT Management & Control Channel

RTMC (VB5.1)



APON: Example –Lucent APON System

AscendGX-550

LucentAC 230

ONTs PONUNI Cards• 8-port DS1 CES• 10/100 Base-T• ATM25• ATM45

155 Mbit/s

32 Split

DS3/1 CircuitNetwork

ATM IF (OC3)

ATMNetwork

OC-3c/STM-1OC-12c/STM-4OC-48c/STM-16

EMS(NavisTM)

NMS

CORBA Interface


APON: Example –Lucent FTTB/H ONT

Top View Rear View*

Front View Fiber Cassette

* UNI cards are PCMCIA type.



APON: Summary

With the APON, ILECs can finally service broadcasting video through their access networks, competing with CA-TV service providers.

ILECsStrong

Players

A core set of APON standards (ITU-T G.983.1 & 2) exists today, has been proven by several field trials, and thereby guarantees interoperability among products from different vendors.

MatureLevel of

Standards

Voice, data, and streaming video are transported by normal ATM cells, while broadcasting video is delivered by WDM overlay (optional).

YesService

Integration

APON is based on ATM technology, so it continues to use network service providers’ existing ATM-based infrastructure.

Downside is, however, its relative difficulty in adapting to all IP-based solutions in the near future.

LowInitial Capital

Expenditure

RemarksAnswersKey Questions


EPON

OverviewUp/Down Traffic FlowFrame FormatsEPON vs. APONSummary



EPON: Overview

Focus on direct support of Ethernet services.Candidate solution for Ethernet in the First Mile (EFM)*Initial focus: FTTB and FTTC solutionsLong-term objective: Full-service FTTH solutionBenefits compared to the APON

• Low protocol overhead• Higher bandwidth

• Lower costs

• Broader service capabilities

Similar upstream architecture to ITU-T G.983* EFM is a new IEEE 802.3 working group (mostly Ethernet vendors) formed Nov. 2000.


EPON: Up/Down Traffic Flow

Proposed 1490nm downstream and 1310 nm upstream (1550 free for WDM overlays)Data is transmitted in variable-length packets of up to 1,518 bytes (i.e., Ethernet frame)Some packets may be intended for all of the ONUs (broadcast packets) or a particular group of ONUs (multicast packets)Upstream traffic is managed utilizing TDM technology, in which transmission time slots are dedicated to the ONUsTime slots are synchronized so that upstream packets from the ONUs do not interfere with each otherThe synchronization marker is a one-byte code that is transmitted every 2 ms to synchronize the ONUs with the OLT

* Source: Alloptic



EPON: Frame FormatsDownstream traffic is segmented into fixed-interval frames, each of which carries multiple variable-length packets (IEEE 802.3 format) and transmitted downstream at 1 Gbps.

Clocking information, in the form of a synchronization marker, is included at the beginning of each frame: one-byte code transmitted every 2 ms.

Upstream frames are formed by a continuous transmission interval of 2 ms. A frame header identifies the start of each upstream frame.The example includes two variable-length packets and some time-slot overhead.

The time-slot overhead includes a guard band, timing indicators, and signal power indicators.When there is no traffic to transmit from the ONU, a time slot may be filled with an idle signal.

* Source: Alloptic


EPON vs. APON

ATMEthernet cost+Cost

ATMIP/EthernetComponents

Basically cross-connect, (but can have the same

features as EPON)

routing, switching, firewall, etc.

ONU Features

DifficultYes (easily up to 10 Gbps)

Scalable

TDMATDMA, OthersMultiple Access Scheme

LargeSmallProtocol OverheadFor IP Service

155/622 Mbps1 GbpsSpeed

1998 (1995)N/ADate

ITU-T (FSAN)IEEEStandard Body

APONEPON



EPON: Summary

This is the effect of a current generalized weak R&D activity within Operators.

Mostly Vendors

Strong

Players

IEEE can expedite process with link to ITU-T APON.EFM is not looking for a ‘final’ ‘single’ solution; the Working Group is just considering EPON as an option for Ethernet.

Just Started

Level of

Standards

Voice, data, and streaming video are transported by normal IP packets, while broadcasting video can be delivered by WDM overlay.

YesService

Integration

EPON is based on Ethernet and IP protocols, so the current NSPs (mostly ILECs) should upgrade their existing ATM-based infrastructure at COs and backbones.But this is not the case for CLECs, which are very active in investing new all IP-based technologies.

Mid to High

Initial Capital

Expenditure

RemarksAnswersKey Questions


WDM-PON:Evolution of FTTH Solutions

APON/EPON

B-ISDN UNI

WDM-PON



WDM-PON

DriversEvolution ScenariosWavelength AllocationExample Configurations• For Video Overlay• With WGR (AWG)

R&D Opportunities


WDM-PON: Drivers

What are network/service providers’ needs?• Bandwidth (trivial)

What are (will be) user requirements?• Bandwidth (trivial)

What are (will be) killer applications?• Digital video distribution!• Video on demand• Advanced multimedia services (peer-to-peer)• Ultra-fast FTP(up/down-load)



WDM-PON:Evolution Scenarios

ADSL to VDSL w/ FTTx APON• Big boost in BW without fiber deployment in the last mile

VDSL w/ FTTx APON to FTTH APON (or EPON*)• Only VDSL modems and DSLAMs are to be replaced by

ONTs and OLTs (keep existing ATM-based infrastructure).• Mature standards and strong supports from leading telecom

service providers and equipment suppliers.� Can drive and afford initial deployment of fibers in the last mile.

• Lower maintenance costs.• We’ll see a focus has already been moved onto a next

generation PON (i.e., WDM-PON) until EFM (for EPON) standards finally come out.

* CLECs may choose EPON as their solution at this step.


WDM-PON:Evolution Scenarios (Continued)

FTTH APON to WDM-PON• WDM-PON will introduce advanced schemes for

‘IP over WDM’• Provides protocol/format-independent P-t-P paths

between ONTs and OLT.� Can use relatively-cheap optical Ethernet components

(or those of any other P2P solutions) w/o all the hassles of complicated MAC protocols (unlike APON & EPON).

• Many implementation options



WDM-PON: Wavelength Allocation1.3 µm wavelength band (Upstream)

1260 13601340132013001280

G983.1 Upstream Band(unchanged at 100 nm bandpass)

Upstream Window (no change)Basic Band (constrained APON band)Enhancement Band (other uses)For future use

1360 14601440142014001380

Reserved for allocation by ITU-TGuard band

1480

Guard band

Intermediate wavelength band (Upstream and/or Downstream)

1.5 µm wavelength band (Upstream and/or Downstream)Enhancement BandBasic Band

ATM-PON

DownstreamGuard band Guard band

Future L Band

Reserved forallocation by ITU-T

λ 1λ

2λ

4λ

3λ

5λ

6

λ1-λ6:Defined in Table 2

1.3 µm wavelength band (Upstream)

1260 13601340132013001280

G983.1 Upstream Band(unchanged at 100 nm bandpass)

Upstream Window (no change)Basic Band (constrained APON band)Enhancement Band (other uses)For future use

1360 14601440142014001380


1480

Guard band


1360 14601440142014001380


1480

Guard band


1.5 µm wavelength band (Upstream and/or Downstream)Enhancement BandBasic Band

ATM-PON


Future L Band


λ 1λ

2λ

4λ

3λ

5λ

6

Enhancement BandBasic Band

ATM-PON


Future L Band


λ 1λ

2λ

4λ

3λ

5λ

6

λ1-λ6:Defined in Table 2

* ITU-T Rec. G.983-3.


WDM-PON: For Video Overlay

WDM(WF1)

orCombiner

For Bas ic Band

For Enhancement Band

(Bas ic Band and Video Rece iver)

Tx

for Bas ic Band

for Enhancement Band

Tx

RxLogic

Tx

RxLogicWDM -L

Tx

Tx

RxLogic

RxRx

WDM

Combiner

WDM

Combiner

For Bas ic Band


ONU

Tx

RxLogic

OLT

Tx

RxLogicWDM -LTx

RxLogic

Tx

RxWDM LL

(combined Bas ic Band and Enhancement Band)

RxRx

WDM

(WF2)Combiner

WDM-NWDM

(WF1)or

Combiner

For Bas ic Band


(Bas ic Band and Video Rece iver)

Tx

for Bas ic Band

for Enhancement Band

Tx

RxLogic

Tx

RxLogicWDM -L

Tx

Tx

RxLogic

RxRx

WDM

Combiner

WDM

Combiner

For Bas ic Band


ONU

Tx

RxLogic

OLT

Tx

RxLogicWDM -LTx

RxLogic

Tx

RxWDM LL

(combined Bas ic Band and Enhancement Band)

RxRx

WDM

(WF2)Combiner

WDM-N

Combiner(first stageof 2:Nsplitter)

Tx

RxLogic

WDM-N

OLT (for Basic Band)

E-OLT (for Enhancement Band)Lo

Hi

AmpTx

Passband

Tx

RxLogicWDM-L


Tx

RxLogic

WDM-N -Lo

Hi

Amp


ONU (for Basic Band and Enhancement Band)

Tx

RxLogic

WDM-N



Hi

AmpTx

Passband

Tx

RxLogicWDM-L


Tx

RxLogic

WDM-N



Hi

AmpTx

Passband

Tx

RxLogicWDM-L


Tx

RxLogic

WDM-N -Lo

Hi

Amp


ONU (for Basic Band and Enhancement Band)

Tx

RxLogic

WDM-N



Hi

AmpTx

Passband

Tx

RxLogicWDM-L

* ITU-T Rec. G.983-3.



WDM-PON: With WGR (AWG)

RX

TX

1x16WGR

RX

TX

WDM-N

WDM-N

ONT 1

ONT N

…… ……λ1

λ16

λ17

λ32

WDM-L

λ1, …, λ 16

λ17, …, λ 32

WDMTX

WDMTX

OLT


WDM-PON: R&D Opportunities

Targets• Find the best strategy for future upgrades based on the

existing (in the future) PON infrastructure: Possible steps are� Systems overlap on the same infrastructure� Dynamic reconfiguration to accomplish providers and/or

services grooming� All-optical packet switching

• Define system architecture and protocols.• Identify new equipment (e.g. LT, NT, CPE) in the access

� Envisaging solutions for the ‘last meter’ � Listing requirements to enable ‘Fiber-to-the-appliance”

• Identify and develop components enabling new system architecture.



WDM-PON: R&D Opportunities (Continued)

Research Topics• New IP-centric operations and management protocols

� OAM&P� Protection

• WDM components� AWGs� Optical filters

• Tunable lasers• Use of optical Ethernet (i.e.,10GigE) components• Electronic components• Testbed

� Jointly with Industrial and/or Academic partners


Final Words

The infrastructure for future FTTH solutions will be based on PON.APON provides a better migration path to CLECs, while EPON is more attractive to ILECs.Focus of R&D activities in FTTH will be put on the next generation PON based on WDM and IP technologies, leveraging the existing (in the future) PON infrastructure.



For Further InformationADSL

• DSL Forum� http://dslforum.org/

APON• FSAN

� http://www.fsanet.net/

EPON• IEEE 802.3 Ethernet in the First Mile Study Group

� http://www.ieee802.org/3/efm/

Optical Ethernet• IEEE P802.3ae 10Gb/s Ethernet Task Force

� http://grouper.ieee.org/groups/802/3/ae/index.html

• 10 Gigabit Ethernet Alliance� http://www.10gea.org/

past, present, and future of fiber-to-the-home solutions

Technology

optical network unit

apon epon slides

upstream grants atm

service node olt

example lucent fttbh

mbs pon

oc3 atm network oc

wdm pon