Next-Generation Optical Access Architecture

STMicroelectronics

Advanced System Technology

Next-Generation OpticalAccess Architecture

- SNRC Industry Seminar Series -

Joseph KimST Researcher-in-Residence at SNRC

February 24, 2004

ADVANCED SYSTEM TECHNOLOGY


Advanced System Technology

Mission• To provide the advanced system knowledge able

to establish ST as the system on a chip leadingcompany in the market for the products of the nextdecade

Role• To provide the Company with long-term core

business and leadership in key markets by: Identifying fundamental market changes

Ensuring early access to Intellectual Property

Developing system architectures and prototypes


SAN JOSE’

SAN DIEGOCATANIA GRENOBLE

GENEVA

MILANO

AIX EN PROVENCE

BOSTON LECCE

HONG KONG

= large research lab (>15 people)

NOIDABANGALORE

BRISTOL LUGANO

PORTLAND PARIS

AST - Global R&D Organization


AST - Optical Networking Activities

GIANTValidation of GPON indemonstratorIntegration of building blocksPerformance (efficiency, QoS)testingService demonstration

GBRA

GXT0

CPA

GLTA Board GNTA Board

GBLALD+AFE

PD+AFE

WDM

GXTPNT version

PD+AFE

LD+AFE

WDM CDR

GXTPLT

version

LDDriver

ARM

Designed by STM

Designed by STM

Designed by Intec

Designed by IntecSystem Info control

PTSP OBC PTSP OBC

Designedby ABell

Designedby ABell

1.25 Gbps

622 MbpsGBRA

GXT0

CPA

GLTA Board GNTA Board

GBLALD+AFE

PD+AFE

WDM

GXTPNT version

PD+AFE

LD+AFE

WDM CDR

GXTPLT

version

LDDriver

ARM

Designed by STM

Designed by STM

Designed by Intec

Designed by IntecSystem Info control

PTSP OBC PTSP OBC

Designedby ABell

Designedby ABell

1.25 Gbps

622 Mbps

SYMPHATISymmetrical PON at high bit rateSpecify and design chipset for 1.25Gbps upstream GPON - Class BLab demo at 622 Mb/s upstreamAPON system


MEMS – free space

Bubble switch

ST Competences in Optics - 1


ST Competences in Optics - 2


Outline

Paradigm Shift in Optical Networking

Next-Generation Optical Access Architecture• Why Optical Access?

• TDM-PON: Current-Generation Optical Access

• Stanford University aCCESS (SUCCESS)

Summary


Paradigm Shift in Optical Networking

Towards more Flexible, Dynamically-ReconfigurableOptical Networks from Fixed, Static ones

Driving forces behind this shift• Mismatch between service/usage model & network infrastructure

• Unbalance between backbone (waste of BW) and access (lack ofit)

• Rapid development in enabling technologies Tunable optical components

Burst-mode communications

Optical packet/burst/flow switching

Dynamically-reconfigurable networks better meetvarying user demands even with fewer resources!


Traditional Way of Using Wavelengths

TX

TX

TX

TX

RX

RX

RX

RX

SW SW


Optical Network withPassive/Semi-passive Nodes

New Way of Using Wavelengths

TunableTXSW

TunableTXSW

TunableTXSW

FixedRX SW

FixedRX SW

FixedRX SW


Continuous-Mode vs. Burst-ModeCommunications

TX RXSW SW...010110100101110100101001001010101111101001010101…

SONET/SDH

Packet Packet Packet

RX SW10011…0110

Packet Packet Packet011…010 011…010


Examples

WAN• TWIN, Lucent Bell Labs

MAN• HORNET, PNRL/Stanford

• RINGO, Politechnico de Turin

Regional Access• ONRAMP, Lincoln Lab/MIT

Access• STARNET, DWA-PON & SUCCESS, PNRL/Stanford

• TOBASCO, Lucent


TWIN: Network is a Giant Switch

TWIN cloud

DS-3interface

Ethernetinterface

ATMover OC-3interface

Traffic destined to this nodeshould use purple wavelength

Network ~ Logical node

Core ~ Virtual back-plane

Edge node ~ Port * Slide from Indra Widjaja, Bell Labs


TunableTransmitter

λ1

POPAccess Point

Access Point

Access Point

Access Point

Access Point. . . . . .WirelessIP Cell

λΝ

Packet Switch

Localnetwork

POP = Point of Presence

To long-haul network

λ1dropMAC

PacketReceiver

HORNET: Flexible, Multi Service Ring

* Slide from Kapil Shrikhande, PNRL, Stanford

ADVANCED SYSTEM TECHNOLOGY* Slide from Sarah Dubner, MIT Lincoln Lab


OLT

TL1TL2 TL3 TL4

A W G

PON1Infrastructure

PON4Infrastructure

ONUs

4 Ultra-fast Tunable Lasers,

capable of 25GHz tuning

32 λ,100GHz spacing,

flat top filtersEach Laser can reach each ONU

λ32

Burst-mode[all CMOS]Central

Office Boundary

DWA-PON

* Slide from Matt Rogge, PNRL, Stanford


Enabling Technologies

Common denominator in technologies enablingflexible, dynamically-reconfigurable opticalnetworks• CWDM

• Tunable Filters

• Tunable Lasers

• Burst-Mode Receivers (BMRs)

The paradigm shift pushes these technologiestowards the edge of the networks!


Coarse Wavelength Division Multiplexing

ITU-T Recommendation G.694.2• 1270-1610 nm, 18 wavelengths, 13nm flat-top

• Permitting low-cost components Uncooled, unstabilized, direct-modulated transmitter

Migration path: CWDM to DWDM• Iannone, “In-Service Upgrade of an Amplified 130-km Metro CWDM

Transmission System Using a Single LOA with 140-nm Bandwidth,” OFC ‘03


Tunable Filters – PromisingTechnology for Access

Active thin film (Aegis Semiconductor)

Integrated into semiconductors

Small size & power


Tunable LasersFast tuning time is critical

• State-of-the-art: ~5 ns over entire C-band Based on GCSR laser

Digitally-controlled driver with overdriving pulse technique

* Slide from Kapil Shrikhande, PNRL, Stanford


Burst-Mode Receivers

Focus shifted from OLT to ONUs

One-chip solution preferred• For mass deployment with ONUs

• Eventually, there will be no cost differencebetween continuous-mode & burst-mode receivers


Why Optical Access?

Advantages of fiber as a transmissionmedium• Greater capacity (100s of Tb/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.


TDM-PON Example - EPON

Proposed 1490nm downstream and1310 nm upstream (1550 free for WDMoverlays)Data is transmitted in variable-lengthpackets of up to 1,518 bytes (i.e.,Ethernet frame)Some packets may be intended for allof the ONUs (broadcast packets) or aparticular group of ONUs (multicastpackets)Upstream traffic is managed utilizingTDM technology, in which transmissiontime slots are dedicated to the ONUsTime slots are synchronized so thatupstream packets from the ONUs donot interfere with each otherThe synchronization marker is a one-byte code that is transmitted every 2ms to synchronize the ONUs with theOLT

* Source: Alloptic


TDM-PON Example- APON (Lucent FTTB/H ONT)

Top View Rear View*

Front View Fiber Cassette

* UNI cards are PCMCIA type.


Evolution of PONs

TDM-PONs

OLT

ONT

ONT

ONTWDM-PONs

OLT

ONT

ONT

ONT

?


SUCCESS - Overview

Sponsored by ST/SNRC• Through F/M/A program

Next-generation optical access architecture based on• Hybrid WDM/TDM-PONs

• Ring+Tree topology

• Fast Tunable Components

Starting point: How to efficiently/smoothly upgradeTDM-PONs with those enabling technologies in thefuture?


SUCCESS – Major Objectives

Backward compatibility• To guarantee the coexistence of current-generation (TDM-

PON) and next-generation (WDM-PON) optical accesssystems in the same network

Easy upgradeability• To provide smooth migration paths:

TDM-PON ⇒ Hybrid WDM/TDM-PON ⇒ WDM-PON

Protection/restoration capability• To support both residential/business users on the same

access infrastructure


SUCCESS – Features

Flexible Remote Nodes (RNs) with protection & restorationcapability

• Thin film filters as CWDM add/drop filters• Passive splitter for TDM-PONs• Athermal cyclic AWG for new WDM-PONs

Cost-effective ONUs for WDM-PON• No local light source (for DWDM)

Optical bursts provided by OLT for upstream transmission, aremodulated by SOA at ONU, and send back to OLT.

New MAC protocols designed for efficient bidirectional transmission

Integrated OLT• Based on tunable components• Can support both TDM-PONs and WDM-PONs


:Passive splitter

C :CWDM, splitterC

C

C

Single Fiber, bi-directional transmission

Network Migration Scenario

CO

“Plain-old” PON

2×N

Flexible, protected, efficientAccess Networks.

Old ONUs and dist.fibers are preserved.

W

W :DWDM, AWG

Co-Existing TDM/WDM-PONs

W

W


RN with Passive Splitter

2×N

Downstream: 1550.12nm

Upstream:1310nm

RN 15dB

4~32 ONUs

N×N

RN

ring ringring ring

Other λs


Upstream: 1310nm


Upstream: 1290nm

Other λs

ONU group #2 ONU group #1

N-2N-2

For TDM-PONs


For WDM-PONsBased on Athermal cyclic AWGBW of the thin-film band splitter (for DWDM λs):

• Up/down-stream shares same λ: (N-1)×Δ.• Up/down-stream have different λ : (2×N-1)× Δ.

RN with AWG

N-1 ONU N-1 ONU

AWG

.

.

.

.

.

.

λ

ring ring

RN

Other λs


Semi-Passive RN forProtection/ Restoration

10/90Elec.Ctrl.

2×2switch

N-1 N-1

Band splitters (A/D)

Passive splitteror AWG

West East

Power fromone ONU

RN


ONUs for WDM-PON

SOA

distributionfiber

Single port VCSOAas modulator

SOA

2

3

1distributionfiber

SOA may be usedas pre-amplifier

No local DWDM source for lowering cost

SOA as modulator and/or pre-amp


to the ring

WDM coupler

CWDM

DWDM

Fast TLS

Pre-Amp

Post-Amp

Demux

TFsameISP

…

OLT Structure Use tunable components to reduce transceiver counts and

network cost. Each ISP can have TX/RX pair(s) to bundle/unbundle

data in optical domain. The number of fast tunable laser sources depends on the

number of users, services, and the network load.


ONU1 ONU2

ONU3

scope

pattern generator

AWG AWG

SMF:2.2km SMF:15km

SMF:5kmSMF:15kmSMF:2.2km

ONU

SOA AM

TLS:λ2

TLS:λ1

OBPF EDFA

thin-film A/D

circulator

passive splitter

OLT

75/25

Experimental Setup


800 ps

800 ps

Experimental ResultsDownstream Data Eye Diagram:

Upstream Data Eye Diagram:

2 ms

2 ms

leading edge ofCW burst on λ1

leading edge ofupstream traffic on λ1

2 ms

The timing diagram of packetized transmission based on SUCCESS MAC:

Downstreampackets and CWbursts on λ1

Downstreampackets and CWbursts on λ2

Upstreamtraffic monitoredat OLT


SUCCESS WDM-PON MAC Protocol

Design goal• To provide efficient bidirectional transmission

Challenges• Variable-length frames

• Time-sharing of the same channel for both up-and downstream traffic

• No separate control channel/frame structure

• No delay equalization Need to reduce the impact of different RTTs.


SUCCESS WDM-PON Frame Formats

Delimiter Preamble(01…01)

1-BitID(=1)

Ethernet Frame

CW

or

16-BitGrant

Overhead (= 24 Bits)

Down-stream

Up-stream Delimiter Preamble

(01…01)

Overhead

Ethernet Frame 16-BitReport

Ethernet Frame …

Delimiter Preamble(01…01)

1-BitID(=0)

Overhead


First Step - Sequential Scheduling

RX1

RX2

TX1

TX2

TX3 t0

RTT3

λ1

λ2

λ4

G

λ4λ1

New transmissionscheduled!

t1

l1

RTT1

λ2

λ1

t

Example for 3 TXs, 2 RXs & 4 CHs


Simulation Results - Throughput

Upstream Throughput

Downstream Throughput


Next Step - Batch Scheduling

Improvements over sequential scheduling• Schedule over HOL frames in VOQs with the earliest

available TX and RX Room for optimization & priority queueing to minimize wasted

resources for higher throughput and shorter delay

Implementation Options• Adaptive Batch Size

Batch size varying upon queue length, packet dead line andso on

• Multiple sets of VOQs per ONU To provide multiple QoS classes and better fairness between

up- and downstream traffic through priority queueing


Batch Scheduling – Timing Diagram

ArrivalTime

ScheduledTX Time

(n-1)th batch nth batch (n+1)th batch

Scheduling (n-1)th batch Scheduling nth batch andany remnant from (n-1)thbatch


Batch Scheduling - OLT Structure

…DownstreamVOQs

…UpstreamVOQs Scheduler*

…PollingVOQs

TX queue(1 frame)

TunableLaser

TX1

Fiber

. .

.

TX queue(1 frame)

TunableLaser

TXM

Pointer to a frame tobe scheduled next

* Scheduler maintains a list ofscheduled transmissions andreceptions where transmission &reception times, VOQ #, CH #, RX #and TX # are stored.

Scheduled framesTo RXs (control signals)


Summary

Mismatch between current service/usage model andnetwork infrastructure is a driving force behind theparadigm shift in optical networking

• Towards flexible dynamically-reconfigurable optical networking• Rapid developments in tunable optical components, CWDM, and

BMRs make such dynamically-reconfigurable optical networkingfeasible.

• Advances in architectural study push those enabling technologiestowards the edge of the network.

SUCCESS is a joint research initiative for a next-generation optical access architecture

• Exploiting the benefit of flexible, dynamically-reconfigurableoptical networking in access

• Guaranteeing smooth transition paths from current TDM-PONs tofuture WDM-based optical access

Next-Generation Optical Access Architecture

Technology

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