Terascale Network Technology Workshop- Solutions for Lightpaths

- Architecture, Control and Cost

Kim Roberts, & Michel Belanger

Optical Systems

July 17, 2005

2 Nortel Confidential – Information under NDA

A LightPath

> A network connection that provides guaranteed capacity, constant latency, and high reliability.• Provisioned by a control plane. • Megabits to Terabits per second• The optimum implementation can be L0, L1, or L2, depending on

the capacity needed and facilities available

Layer 2 Packet EthernetLayer 1 Transport OC-192Layer 0 Photonic Photons

Layer 2 Packet EthernetLayer 1 Transport OC-192Layer 0 Photonic Photons

3 Nortel Confidential – Information under NDA

Challenges in using Lightpaths

> Layer 0 Photons• Need to make the connection independent of optical physics• Need effective way of switching of lots of wavelengths – any to any

> Layer 1 OC-192• Need to map efficiently into the appropriate bandwidth• Need cost-effective switching of lots of STS-Ns

> Layer 2 Ethernet Connections• Need to aggregate packets while preserving quality• Need cost-effective management of lots of VLANs

4 Nortel Confidential – Information under NDA

Summary: Lightpath Solutions

> Layer 0 Photons• Have made the connection independent of optical physics• WSS effective switch for lots of wavelengths

> Layer 1 OC-192• GFP/VCAT/LCAS maps efficiently into the appropriate bandwidth• OME and HDX effective switching for lots of STS-Ns

> Layer 2 Ethernet Connections• L2SS aggregates packets while preserving quality• L2SS, RPR provides cost-effective management of lots of VLANs• RPR provides high reliability ring.

5 Nortel Confidential – Information under NDA

Making Layer 0 Independent of Optical Physics

> What is wrong with physics?

> Solutions in CMOS

6 Nortel Confidential – Information under NDA

Hurdle: Fiber Dispersion Management

ROADM

SMF-28

SMF-28

SMF-28

E-LEAF

E-LEAF

E-LEAF

TWcTWc

PhotonicCross-Connect

PhotonicCross-Connect

PhotonicCross-Connect

Bulk dispersion compensation will not suffice

7 Nortel Confidential – Information under NDA

Effect of Dispersion

Transmitted Eye Eye after 320 km of Fiber

8 Nortel Confidential – Information under NDA

Optical Nonlinearities

> Self Phase Modulation (SPM) arises from the Kerr effect, where the amplitude of an optical signal changes its phase.• Rapid phase changes interact with chromatic dispersion to distort

high capacity optical signals.

> Cross Phase Modulation (XPM) is the similar effect between channels.

> Other nonlinearities: Four wave mixing, SRS, SBS, MI

> Amplified Spontaneous Emission (ASE) is optical noise

9 Nortel Confidential – Information under NDA

Issues with using present methods

10 Nortel Confidential – Information under NDA

Dispersion Compensation Modules (DCM)

> Coils of 1 to 20 km of special fiber

> 3 to 9 dB of loss

> One module for C, another for L band

> $3k to $10k per module

> Different slopes for different fiber types

> Generally needed at each line amp site• Depending upon fiber type, system topology, span lengths.

All the above still does not get us over the hurdle of full agility or address multiple line rates

11 Nortel Confidential – Information under NDA

Layer 0 Solutions

12 Nortel Confidential – Information under NDA

Transmitter Pre-compensation

Opticalmodulator

laser

D/A

D/A

CD-1

Digitaldata

Recovered data

0

Tx Rx

-30 -20 -10 0 10 20 30

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

13 Nortel Confidential – Information under NDA

Electronic Dispersion Compensation320 km of G.652 fiber, 2.5 dBm launched

No Compensation

14 Nortel Confidential – Information under NDA

Received Eye Diagram320 km of G.652 fiber, 2.5 dBm launched

No Compensation WARP CompensationOvercomes Dispersion

15 Nortel Confidential – Information under NDA

10 Gb/s with no Traditional Dispersion Compensation

Eye diagrams after transmission over standard G.652 fiber with Nortel WARP processing.

0 Km 1600 km 3200 km 5120 km

16 Nortel Confidential – Information under NDA

Forward Error Correction to mitigate noise

0

[dB] CodingGain

4.0

8.0

12.0

WRAP10

WRAPTOR

TRIFEC

FECAug 1996

10.0

6.0

2.0

RS-8; 6.2 dB (G.975)

2000 2001 2002 2003

0.13 um CMOS6M gates

9.2 dB; 7% OH 0.18 um CMOS

2M gates7.4 dB; 7%BCH-20

0.5 um BiCMOS600K gates4.2 dBBCH-3

Shannon Bound @ 7% (~ 10.4 dB)

3 dB

Performance: Effective Coding Gain> Wraptor corrects an error rate of 0.38% to < 10-16

> Increased system gain and improved burst tolerance

Performance: Effective Coding Gain> Wraptor corrects an error rate of 0.38% to < 10-16

> Increased system gain and improved burst tolerance

17 Nortel Confidential – Information under NDA

Simplified Optical Line Enables Lightpaths

OADM NodeM

ux

Terminal Node AMP Node

OEO

OEO

…

Mu

xOEO

OEO

…

DCF

DCF

DCF

DCF

DCF

DCF

DCF

DCF

OEO

OEO

…

OEO

OEO

…DCF

DCF

Dem

ux

Dem

ux

Terminal Node

Ram

an

Ram

an

Ram

an

OEO

OEO

OEO

OEO

OEO

OEO

WSS NodeTerminal Node AMP Node Terminal Node

Tom Di PasqualeOptical Solutions

Paul DaspitAdvanced Technology Research