FIBER OPTIC CONNECTIONS
Chapter 1 states that a fiber optic data link performs three basic functions.
First, the data link transmitter converts an electrical input signal to an optical
signal. Then, the optical fiber transmits this optical signal. Finally, the data link
receiver converts the optical signal back to an electrical signal identical to the
original input. However, chapter 1 does not describe how optical power transfers from one
optical component to another.
This chapter describes how optical power is transferred from one fiber optic component
to another. It describes how an optical source launches optical power into a fiber as well
as how one optical fiber couples light into another fiber. In fiber optic system design,
this launching or coupling of optical power from one component to the next is important.
Fiber optic connections permit the transfer of optical power from one component to
another. Fiber optic connections also permit fiber optic systems to be more than just
point-to-point data communication links. In fact, fiber optic data links are often of a
more complex design than point-to-point data links.
A system connection may require either a fiber optic splice, connector, or coupler. One
type of system connection is a permanent connection made by splicing optical fibers
together. A fiber optic splice makes a permanent joint between two fibers or two
groups of fibers. There are two types of fiber optic splices--mechanical splices and
fusion splices. Even though removal of some mechanical splices is possible, they are
intended to be permanent. Another type of connection that allows for system
reconfiguration is a fiber optic connector. Fiber optic connectors permit easy
coupling and uncoupling of optical fibers. Fiber optic connectors sometimes resemble
familiar electrical plugs and sockets. Systems may also divide or combine optical signals
between fibers. Fiber optic couplers distribute or combine optical
signals between fibers. Couplers can distribute an optical signal from a single fiber into
several fibers. Couplers may also combine optical signals from several fibers into one
fiber.
Fiber optic connection losses may affect system performance. Poor fiber end
preparation and poor fiber alignment are the main causes of coupling loss.
Another source of coupling loss is differences in optical properties between the connected
fibers. If the connected fibers have different optical properties, such as different
numerical apertures, core and cladding diameters, and refractive index profiles, then
coupling losses may increase.
Q.1 Which fiber optic component (splice, connector, or coupler) makes a permanent
connection in a distributed system?
Q.2 What are the main causes of coupling loss?
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