EE 230: Optical Fiber Communication Lecture 16

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EE 230 Optical Fiber Communication Lecture 16
Active WDM Components and Networks
From the movie Warriors of the Net
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Optical Switches
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Optical Switching Matrix
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Switching methods

• Thermo-optic
• Tunable filters
• Liquid crystal
• Electro-optic
• Liquid reflection
• MEMS

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Tunable Optical Filters
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Agilent Bubble Switch
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MEMS Technology
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Wavelength Converters
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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OADM Illustrated
Optical Fiber
1557.36nm
1555.75nm
OADM Sites
1535.04nm
1533.47nm
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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

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MEMS OXC in Action (MEMX Co.)
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Spectral Efficiency of WDM Systems

• For ?100 GHz and B10 Gb/s, ?10
• For ?50 GHz and B40 Gb/s, ?80

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Typical Network Structure
Composed of WDM Transport Equipment SONET
ADD/Drop Muxes Digital Crossconnect
Advantages Off the shelf technology Full SONET
Management and QOS Flexible routing at STS-1 or
below Disadvantages Large Expensive Diversit
y of management systems Difficult
Provisioning Expensive interconnect cabling
Digital Crossconnect
Transport Fiber
WDM Transport Equipment
SONET Add/Drop Mux
Add/Drop Channels
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Types of WDM Networks

• Local area (LAN)
• Metropolitan area (MAN)
• Wide area (WAN)

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Configurations of WDM Networks

• stargood for LANs
• bus (chain)--LANs
• ringgood for MANs and WANs
• hubgood for WANs collection of stars or rings

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Limitations on Performance, N

• Wavelength stability of diode lasers
• Nonlinear optical effects
• Crosstalk in the demultiplexing process

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OC-48 Link Performance vs. Distance
16 km
25 km
0 km
41 km
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OC-48 Eye Diagrams
Receiver Module Output
BERT
Laser Input
CDR Input
Laser Output
Regenerated Data (CDR output)
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10Gb/s Eye vs. Transmission Distance
Optical Signal
Input to CDR
Optical Signal
Input to CDR
0 km
25 km
12 km
37 km
16 km
41 km
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OC-192 Link TestingEye Diagrams throughout the
system
After Receiver Module
Input Signal from BERT
Input to CDR
After Laser Driver
Regenerated Data
Optical Signal from Laser
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The Future?
Advantages
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
Disadvantages
No low level traffic grooming Not directly
compatible with SONET protection protocols
Less bandwidth efficient No statistical
multiplexing of low level STS-n data streams
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Design Objective120 Gb/s Optical WDM Cross
Connect Switch
WDM with Electronic Switching Technology

• 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

Advantages of an Electronic Core

• 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)

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WEST System DemonstrationConfiguration Overview

• Configured as an Add/Drop node
• 4 Channels of Add/Drop
• 8 Transmission Channels
• Optical Monitoring
• Eye diagram monitoring
• Clock monitoring for acquisition
• demonstration

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12x12 VXI Switch ModuleFeature Highlights

• 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
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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)