Stephen Schultz EE466Fall 2007
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1. Introduction
Stephen Schultz EE466Fall 2007
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Communication Links
Stephen Schultz EE466Fall 2007
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Undersea Optical Fiber Backbones
Stephen Schultz EE466Fall 2007
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Fiber Data Rate
Stephen Schultz EE466Fall 2007
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Fiber Capacity
http://www.laserfocusworld.com/articles/article_display.html?id=277158
Stephen Schultz EE466Fall 2007
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Multiplexing
Stephen Schultz EE466Fall 2007
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TDM Standards• Standards developed for optical fiber communications rates
– Synchronous Optical NETwork (SONET)
– Synchronous Digital Hierarchy (SDH)
SONET SDH B (Mb/s) Channels
OC-1 51.84 672
OC-3 STM-1 155.52 2,016
OC-12 STM-4 622.08 8,064
OC-48 STM-16 2,488.32 32,256
OC-192 STM-64 9,953.28 129,024
OC-768 STM-256 39,813.12 516,096
Stephen Schultz EE466Fall 2007
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Optical Signal
• Optical signals are typically sent using on-off keying (OOK)
– Power received: 1
– No power: 0
• Two primary formats
– Nonreturn to zero (NRZ)
– Return to zero (RZ)
Stephen Schultz EE466Fall 2007
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Basic Optical Communication Link
• Electrical signal transferred to another location
– Electrical-to-Optical (E-O) conversion
• Modulated laser
– Signal transmission
• Optical fiber
– Optical-to-Electrical (O-E) conversion
• Detector
Stephen Schultz EE466Fall 2007
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Signal Transmission
• Signal is attenuated as it propagates through the fiber
– Decrease in signal amplitude
– Reduction in signal-to-noise ratio (SNR)
• Pulse is spread in time
– Called signal dispersion
– Causes inter-symbol interference (ISI)
Stephen Schultz EE466Fall 2007
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Additional Components
• External modulator
– Better signal—lower signal dispersion
• Optical amplifier
– Amplifies signal to overcome attenuation
Stephen Schultz EE466Fall 2007
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Topics to be Covered
• Fibers
– Attenuation
– Dispersion
• Sources
• Detectors
• System performance