1 stephen schultzee466 fall 2007 1. introduction

Stephen Schultz EE466Fall 2007

1

1. Introduction


2

Communication Links


3

Undersea Optical Fiber Backbones


4

Fiber Data Rate


5

Fiber Capacity

http://www.laserfocusworld.com/articles/article_display.html?id=277158


6

Multiplexing


7

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


8

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)


9

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


10

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)


11

Additional Components

• External modulator

– Better signal—lower signal dispersion

• Optical amplifier

– Amplifies signal to overcome attenuation


12

Topics to be Covered

• Fibers

– Attenuation

– Dispersion

• Sources

• Detectors

• System performance

1 stephen schultzee466 fall 2007 1. introduction

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