Manufacturers design fiber-optic cables for
specific applications. For example, is the cable buried
underground or hung from telephone poles? Is the cable
snaked through cableways, submerged in water, or just
laid on the ground? Is the cable used in industrial,
telecommunication, utility, or military applications?
Each type of application may require a slightly different
Agreement on standard cable designs is difficult.
Cable design choices include jacket materials, water-
optic cables. Some fiber-optic cables are used in
commercial applications, and others are used in military
applications. Standard commercial cable designs will
develop over time as fiber-optic technology becomes
FIBER-OPTIC DATA LINKS
A fiber-optic data link sends input data through
fiber-optic components and provides this data as output
information. It has the following three basic functions:
To convert an electrical input signal to an optical
To send the optical signal over an optical fiber
To convert the optical signal back to an electrical
A fiber-optic data link consists of three parts:
transmitter, optical fiber, and receiver. Figure 6-8 is
an illustration of a fiber-optic data-link connection. The
transmitter, optical fiber, and receiver perform the basic
functions of the fiber-optic data link. Each part of the
data link is responsible for the successful transfer of the
data signal. A fiber-optic data link needs a transmitter
that can effectively convert an electrical input signal to
an optical signal and launch the data-containing light
down the optical fiber. Also, fiber-optic data link needs
a receiver that can effectively transform this optical
signal back into its original form. This means that the
electrical signal provided as data output should exactly
match the electrical signal provided as data input.
A fiber-optic splice is a permanent fiber joint
whose purpose is to establish an optical connection
between two individual optical fibers. System design
may require that fiber connections have specific optical
properties (low loss) that are met only by fiber splicing.
Also, fiber-optic splices permit the repair of optical
fibers damaged during installation, accident, or stress.
System designers generally require fiber splicing
whenever repeated connection or disconnection is
unnecessary or unwanted.
Mechanical and fusion splicing are two broad
categories that describe the techniques used for fiber
splicing. A mechanical splice is a fiber splice where
mechanical fixtures and materials perform fiber
alignment and connection. A fusion splice is a fiber
splice where localized heat fuses or melts the ends of
two optical fibers together. Each splicing technique
seeks to optimize splice performance and reduce splice
loss. Low-loss fiber splicing results from proper fiber
end preparation and alignment.
A fiber-optic connector is a device that permits the
coupling of optical power between two optical fibers or
two groups of fibers. Designing a device that allows for
repeated fiber coupling without significant loss of light
is difficult. Fiber-optic connectors must maintain fiber
alignment and provide repeatable loss measurements
during numerous connections. Fiber-optic connectors
should be easy to assemble (in a laboratory or field
environment) and should be cost effective. Also, they
should be reliable. Fiber-optic connections using
connectors should be insensitive to environmental
conditions, such as temperature, dust, and moisture.
Fiber-optic connector designs attempt to optimize
connector performance by meeting each of these
Figure 6-8.Parts of a fiber-optic data link.