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

1
ADVANCED 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.

2
Outline
Why FTTH?
APON
EPON
Slides from BellSouth: First Day in the Life of
FTTH
WDM-PON: Evolution of FTTH Solutions
Final 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.

3
APON
Point-to-Point vs. PON
FSAN Initiative
Common Network Elements
Specifications
Frame Formats
Ranging
Medium Access Control
Burst Mode Reception
UNI Signaling and Control Flows
Example – Lucent APON System
Summary
APON: Point-to-Point vs. PON
Central Office
Access SW
(Statistical MUX)
Passive
Splitter
Houses

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APON: FSAN Initiative
Goal: To break through the economic barrier
Means: By large-scale introduction of
broadband access networks through definition
of basic set of common requirements
Standards: 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
Service
Node
PON Head
End Node
Local
Exchange
Cabinet
SDH PON ADSL
VDSL
VDSL
UNI
FTTCab
FTTC/
FTTB
FTTB/
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

5
APON: Specifications
Symmetrical 155 Mb/s downstream/upstream
(Optional) Asymmetrical 622 Mb/s
downstream & 155 Mb/s upstream
Optical attenuation ranges
• Class B: 10-25 dB
• Class C: 15-30 dB
Maximum fiber distance: 20 km
Maximum split ratio: 32 (optional 64)
APON: Frame Formats*
PLOAM
1
ATM
Cell 1
. . . ATM
Cell 27
PLOAM
2
ATM
Cell 28
. . . ATM
Cell 54
Tframe = 56 cells of 53 bytes
Contain 53 upstream grants
ATM
Cell 1
ATM
Cell 2
ATM
Cell 3
ATM
Cell 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
. . .

6
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
Operational
Parameters
ONT
ONT
ONT
OLT
Management

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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
Terminal
Equipment
ONT OLT
Service
Node
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)

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APON: Example –
Lucent APON System
Ascend
GX-550
Lucent
AC 230
ONTs PONUNI Cards
• 8-port DS1 CES
• 10/100 Base-T
• ATM25
• ATM45
155 Mbit/s
32 Split
DS3/1
Circuit
Network
ATM IF (OC3)
ATM
Network
OC-3c/STM-1
OC-12c/STM-4
OC-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.

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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
Overview
Up/Down Traffic Flow
Frame Formats
EPON vs. APON
Summary

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EPON: Overview
Focus on direct support of Ethernet services.
Candidate solution for Ethernet in the First Mile (EFM)*
Initial focus: FTTB and FTTC solutions
Long-term objective: Full-service FTTH solution
Benefits 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 ONUs
Time slots are synchronized so that
upstream packets from the ONUs do
not interfere with each other
The synchronization marker is a one-
byte code that is transmitted every 2
ms to synchronize the ONUs with the
OLT
* Source: Alloptic

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EPON: Frame Formats
Downstream 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 Overhead
For IP Service
155/622 Mbps1 GbpsSpeed
1998 (1995)N/ADate
ITU-T (FSAN)IEEEStandard Body
APONEPON

12
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

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WDM-PON
Drivers
Evolution Scenarios
Wavelength Allocation
Example 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)

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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

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WDM-PON: Wavelength Allocation
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
Reserved for allocation by ITU-T
Guard 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
Downstream
Guard band Guard band
Future L Band
Reserved for
allocation by ITU-T
λ
1
λ
2
λ
4
λ
3
λ
5
λ
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
Guard band
1480
Guard band
1360 14601440142014001380
Guard band
1480
Guard band
1.5 µm wavelength band (Upstream and/or Downstream)
ATM-PON
Downstream
Future L Band
Reserved for
allocation by ITU-T
λ
1
λ
2
λ
4
λ
3
λ
5
λ
6
ATM-PON
Downstream
Future L Band
Reserved for
allocation by ITU-T
λ
1
λ
2
λ
4
λ
3
λ
5
λ
6
λ1-λ6:Defined in Table 2
* ITU-T Rec. G.983-3.
WDM-PON: For Video Overlay
WDM
(WF1)
or
Combiner
For Bas ic Band
For Enhancement Band
(Bas ic Band and Video Receiver)
Tx
for Bas ic Band
for Enhancement Band
Tx
Rx
Logic
Tx
Rx
LogicWDM -L
Tx
Tx
Rx
Logic
RxRx
WDM
Combiner
WDM
Combiner
For Bas ic Band
ONU
Tx
Rx
Logic
OLT
Tx
Rx
LogicWDM -LTx
Rx
Logic
Tx
Rx
WDM LL
(combined Bas ic Band and Enhancement Band)
RxRx
WDM
(WF2)
Combiner
WDM-N
WDM
(WF1)
or
Combiner
For Bas ic Band
(Bas ic Band and Video Receiver)
Tx
for Bas ic Band
for Enhancement Band
Tx
Rx
Logic
Tx
Rx
LogicWDM -L
Tx
Tx
Rx
Logic
RxRx
WDM
Combiner
WDM
Combiner
For Bas ic Band
ONU
Tx
Rx
Logic
OLT
Tx
Rx
LogicWDM -LTx
Rx
Logic
Tx
Rx
WDM LL
(combined Bas ic Band and Enhancement Band)
RxRx
WDM
(WF2)
Combiner
WDM-N
Combiner
(first stage
of 2:N
splitter)
Tx
Rx
Logic
WDM
-N
OLT (for Basic Band)
E-OLT (for Enhancement Band)Lo
Hi
Amp
Tx
Pass
band
Tx
Rx
LogicWDM-L
Combiner
(first stage
of 2:N
splitter)
Tx
Rx
Logic
WDM
-N -Lo
Hi
Amp
Combiner
(first stage
of 2:N
splitter)
ONU (for Basic Band and
Enhancement Band)
Tx
Rx
Logic
WDM
-N
Hi
Amp
Tx
Pass
band
Tx
Rx
LogicWDM-L
Combiner
(first stage
of 2:N
splitter)
Tx
Rx
Logic
WDM
-N
Hi
Amp
Tx
Pass
band
Tx
Rx
LogicWDM-L
Combiner
(first stage
of 2:N
splitter)
Tx
Rx
Logic
WDM
-N -Lo
Hi
Amp
Combiner
(first stage
of 2:N
splitter)
ONU (for Basic Band and
Enhancement Band)
Tx
Rx
Logic
WDM
-N
Hi
Amp
Tx
Pass
band
Tx
Rx
LogicWDM-L
* ITU-T Rec. G.983-3.

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WDM-PON: With WGR (AWG)
RX
TX
1x16
WGR
RX
TX
WDM
-N
WDM
-N
ONT 1
ONT N
…………
λ1
λ16
λ17
λ32
WDM
-L
λ1, …, λ 16
λ17, …, λ 32
WDM
TX
WDM
TX
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.

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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.

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For Further Information
ADSL
• 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/

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