Title page for ETD etd-093099-094314

Type of Document

Master's Thesis

Author

Kanprachar, Surachet

Author's Email Address

skanprac@vt.edu

URN

etd-093099-094314

Title

Modeling and Analysis of the Effects of Impairments in Fiber Optic Links

Degree

Master of Science

Department

Electrical Engineering

Advisory Committee

Advisor Name	Title
Ira Jacobs	Committee Chair
Anbo Wang	Committee Member
Brian D. Woerner	Committee Member

Keywords

Intersymbol Interference
Impairments
Fiber Optic Links

Date of Defense

1999-09-14

Availability

unrestricted

Abstract

In digital communication systems, several types of impairments may be introduced
to the signal. These impairments result in degraded system performance; for example,
high bit-error-rate or power penalty. For optical communication systems, in this thesis,
these impairments are categorized into four types; that is, thermal noise, shot noise,
signal-dependent noise, and intersymbol interference (ISI). By using a Gaussian approximation,
effects of the first three impairments are analyzed. It is shown that signal-dependent noise
introduces an error floor to the system and the bit-error-rate is considerably degraded
if a nonzero-extinction ratio is applied to the system. It is shown that if the decision
threshold at the decision circuit is set improperly, more received power is required to
keep the bit-error-rate constant.
Three main components in the system (i.e., transmitter, optical fiber, and receiver)
are modeled as Butterworth filters. ISI from this model is determined by computer simulation.
A high ISI is from a small system bandwidth. It is shown that a minimum power penalty can be
achieved if the transmitter and receiver bandwidths are matched and fixed, and the ratio of
fiber bandwidth to bit rate is 0.85. Comparing ISI from this model to ISI from raised cosine-
rolloff filters, it is shown that at some particular bandwidths ISI from raised cosine-rolloff
filters is much lower that that from this model. However, if the transmitter and receiver
bandwidths are not matched and are not equal to these bandwidths, ISI from this model is lower
than ISI from raised cosine-rolloff filters.

Files

Filename		Size	Approximate Download Time (Hours:Minutes:Seconds)
Filename		Size	28.8 Modem	56K Modem	ISDN (64 Kb)	ISDN (128 Kb)	Higher-speed Access
	CompleteThesis.pdf	2.04 Mb	00:09:26	00:04:51	00:04:15	00:02:07	00:00:10