EE 230: Optical Fiber Communication Lecture 16

From the movieWarriors of the Net

Active WDM Components and Networks

Optical Switches

Optical Switching Matrix

Switching methods

• Thermo-optic

• Tunable filters

• Liquid crystal

• Electro-optic

• Liquid reflection

• MEMS

Tunable Optical Filters

Agilent Bubble Switch

MEMS Technology

Wavelength Converters

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

OADM Illustrated

OADM Sites

1557.36nm

1555.75nm

1533.47nm

1535.04nm

Optical Fiber

Opaque vs. Transparent OXCs

• Opaque: every wavelength undergoes OEO conversion. S/N degradation does not accumulate, simple route choice, can change wavelengths at each hop, simple network management

• Transparent: all-optical. Less expensive, dissipates less power, fewer interfaces, no electronics limit on bit rate. Works better in ring networks

MEMS OXC in Action (MEMX Co.)

Spectral Efficiency of WDM Systems

For =100 GHz and B=10 Gb/s, =10%

For =50 GHz and B=40 Gb/s, =80%

B

Transport Fiber

SONET Add/Drop Mux

Digital Crossconnect

WDMTransportEquipment

Add/Drop Channels

• Composed of WDM Transport EquipmentSONET ADD/Drop MuxesDigital Crossconnect

• AdvantagesOff the shelf technologyFull SONET Management and QOSFlexible routing at STS-1 or below

• DisadvantagesLargeExpensiveDiversity of management systemsDifficult ProvisioningExpensive interconnect cabling

Typical Network Structure

Types of WDM Networks

• Local area (LAN)

• Metropolitan area (MAN)

• Wide area (WAN)

Configurations of WDM Networks

• star—good for LANs

• bus (chain)--LANs

• ring—good for MANs and WANs

• hub—good for WANs; collection of stars or rings

Limitations on Performance, N

• Wavelength stability of diode lasers

• Nonlinear optical effects

• Crosstalk in the demultiplexing process

OC-48 Link Performance vs. Distance

0 km

16 km

25 km

41 km

OC-48 Eye Diagrams

BERT

Laser Input

Laser Output

Receiver Module Output

Regenerated Data (CDR output)

CDR Input

10Gb/s Eye vs. Transmission DistanceOptical Signal Input to CDROptical Signal Input to CDR

0 km

12 km

16 km

25 km

37 km

41 km

OC-192 Link TestingEye Diagrams throughout the system

Input Signal from BERT

After Laser Driver

Optical Signal from Laser

After Receiver Module

Input to CDR

Regenerated Data

•Reduced Cost•More Compact•Lower Power•Rapid physical layer protection switching

Simplified Operation, Administration,Management and Provisioning

•Simpler Network interface•Fewer different management systems•Leverages traditional link based management and protection

Advantages

Disadvantages• No low level traffic grooming• Not directly compatible with SONET protection protocols• Less bandwidth efficient• No “statistical multiplexing” oflow level STS-n data streams

The Future?

Design Objective120 Gb/s Optical WDM Cross Connect Switch

Cross Connect Configuration• 3x3 fiber switch• 4 channels/fiber• 10 Gb/s/channel

Electronic Switch Core• OC192/OC48 compatible

Optical MUX/DEMUX• ITU WDM channels

Key Technology• Rockwell GaAs HBT• Ortel DFB Laser/PIN

WDM with Electronic Switching Technology

• Data regeneration/retiming• Wavelength translation• Low crosstalk• OC192/OC48 compatible

• Realizable with current state-of-the-art production technology

• Potential for additional processing of input signal (smart switch)

Advantages of an Electronic Core

WEST System DemonstrationConfiguration Overview

ST

S-4

8 A

dd

ST

S-4

8 D

rop

ST

S-4

8 D

rop

ST

S-4

8 A

dd

Dem

ux

Mu

x

Spl

itte

r

2.5

Gb

/sE

rror

De

t.

2.5

Gb

/sE

rror

De

t.

2.5

Gb

/sP

at. G

en

2.5

Gb

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at. G

en

STS-192 Add

STS-192 Add

ST

S-4

8 A

dd

ST

S-4

8 D

rop

STS-192/STS-48 Drop

STS-192 Drop

ST

S-4

8 D

rop

ST

S-4

8 A

dd

Dem

ux

Mu

x

Spl

itte

r

MuxDemux

Splitter

WDMMonitor With GPIB

Optical Spectrum Analyzer

2.5

Gb

/s

Err

or D

et.

2.5

Gb

/s

Err

or D

et.

2.5

Gb

/s

Pat

. Gen

2.5

Gb

/s

Pat

. Gen

10 Gb/s Pat. Gen

10 Gb/s Pat. Gen

10 Gb/s Error Det.

Scope

µ-wave SpectrumAnalyzer

Scope

ScopeSplitterInternal Nodes

Electrical Power Splitter

WEST Crossconnect

Long Reach Fiber

Short Reach Fiber

•Configured as an Add/Drop node

•4 Channels of Add/Drop

•8 Transmission Channels

•Optical Monitoring

•Eye diagram monitoring

•Clock monitoring for acquisitiondemonstration

Switch Module Features:• 120 Gb/s data throughput• Twelve 10 Gb/s channels• VXI Management and Control

High Speed Package Features:• Clean high speed interface• High Isolation• Thermal management

Switch Chip Highlights:•Suitable for larger switching fabrics•GaAs/AlGaAs HBT•Low crosstalk & jitter generation•Die size: 4.8 x 5.1 mm2

•4600 transistors•Pdiss: 7.4 W

10Gb/s

12x12 VXI Switch ModuleFeature Highlights

WDM Network Design Considerations

• transparent or opaque?

• power level? (high better for receivers, low better for transmitters and NLO)

• branching configuration?

• channel spacing? (small better for capacity, large better for crosstalk)