Chapter 3
Optical Signal Attenuation
and Dispersion
Abstract When information signals travel in any type of transmission medium,
various signal power losses and signal fidelity distortions are always present. Attenuation of a light signal as it propagates along a fiber is an important consideration
in the design of an optical communication system because it plays a major role in
determining the maximum transmission distance between a transmitter and a receiver.
In addition to being attenuated, an optical signal undergoes continuous broadening
and distortion as it travels along a fiber. The signal broadening is a consequence of
intramodal and intermodal dispersion effects.
Chapter 2 showed the structure of optical fibers and examined the concepts of
how light propagates along a cylindrical dielectric optical waveguide. This chapter
continues the discussion of optical fibers by answering two very important questions:
1. What are the optical power loss or signal attenuation mechanisms in a fiber?
2. Why and to what degree do optical signals get distorted as they propagate along
a fiber?
Signal attenuation (also known as fiber attenuation, fiber loss, or power level
reduction) is one of the most important properties of an optical fiber because it
largely determines the maximum unamplified or repeaterless separation between a
transmitter and a receiver. Because amplifiers and repeaters are expensive to fabricate,
install, and maintain, the degree of attenuation in a fiber has a large influence on
system cost. Of equal importance is signal dispersion. The dispersion mechanisms
in a fiber cause optical signal pulses to broaden as they travel along a fiber. If these
pulses travel sufficiently far, they will eventually overlap with neighboring pulses,
thereby creating errors in the receiver output. The signal dispersion mechanisms thus
limit the information-carrying capacity of a fiber.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
G. Keiser, Fiber Optic Communications,
https://doi.org/10.1007/978-981-33-4665-9_3
93
Optical Signal Attenuation
and Dispersion
Abstract When information signals travel in any type of transmission medium,
various signal power losses and signal fidelity distortions are always present. Attenuation of a light signal as it propagates along a fiber is an important consideration
in the design of an optical communication system because it plays a major role in
determining the maximum transmission distance between a transmitter and a receiver.
In addition to being attenuated, an optical signal undergoes continuous broadening
and distortion as it travels along a fiber. The signal broadening is a consequence of
intramodal and intermodal dispersion effects.
Chapter 2 showed the structure of optical fibers and examined the concepts of
how light propagates along a cylindrical dielectric optical waveguide. This chapter
continues the discussion of optical fibers by answering two very important questions:
1. What are the optical power loss or signal attenuation mechanisms in a fiber?
2. Why and to what degree do optical signals get distorted as they propagate along
a fiber?
Signal attenuation (also known as fiber attenuation, fiber loss, or power level
reduction) is one of the most important properties of an optical fiber because it
largely determines the maximum unamplified or repeaterless separation between a
transmitter and a receiver. Because amplifiers and repeaters are expensive to fabricate,
install, and maintain, the degree of attenuation in a fiber has a large influence on
system cost. Of equal importance is signal dispersion. The dispersion mechanisms
in a fiber cause optical signal pulses to broaden as they travel along a fiber. If these
pulses travel sufficiently far, they will eventually overlap with neighboring pulses,
thereby creating errors in the receiver output. The signal dispersion mechanisms thus
limit the information-carrying capacity of a fiber.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
G. Keiser, Fiber Optic Communications,
https://doi.org/10.1007/978-981-33-4665-9_3
93