Type of Document Master's Thesis Author Kanprachar, Surachet Author's Email Address email@example.com 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 Jacobs, Ira Committee Chair Wang, Anbo Committee Member Woerner, Brian D. Committee Member Keywords
- Intersymbol Interference
- Fiber Optic Links
Date of Defense 1999-09-14 Availability unrestricted AbstractIn 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.
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