intensity of incident optical radiation. The relationship
between the input optical radiation and the output
electrical current is given by the detector responsivity.
FIBER-OPTIC SYSTEM TOPOLOGY
Most of the discussion on fiber-optic data links
provided earlier in this chapter and in the CE Basic
TRAMAN refers to simple point-to-point links. A
point-to-point fiber-optic data link consists of an
optical transmitter, an optical fiber, and an optical
receiver. In addition. any splices or connectors used to
join individual optical fiber sections to each other and
to the transmitter and the receiver are included. Figure
6-3 provides a schematic diagram of a point-to-point
fiber-optic data link.
A common fiber-optic application is the full
duplex link. This link consists of two simple point-to-
point links. The links transmit in opposite directions
between the equipment. This application may be
configured using only one fiber. If configured with one
fiber. fiber-optic splitters are used at each end to couple
the transmit signal onto the fiber and receive signals to
All fiber-optic systems are simply sets of point-to-
point fiber-optic links. Different system topologies
arise from the different ways that point-to-point fiber-
optic links can be connected between equipment. The
term topology, as used here, refers to the configuration
of various types of equipment and the fiber--optic
components interconnecting them. This equipment
may be computers, workstations, consoles, or other
equipment. Point-to-point links are connected to
produce systems with linear bus, ring, star, or tree
topologies. Point-to-point fiber-optic links are the
basic building block of all fiber-optic systems.
The Navy has a standard to provide detailed
information and guidance to personnel concerned with
the installation of fiber-optic cables and cable plants.
The fiber-optic cable plant consists of all the fiber-
optic cables and the fiber-optic interconnection
equipment, including connectors, splices, and
interconnection boxes. The fiber-optic cable and cable
plant installation standard consists of the following:
Detailed methods for cable storage and
handling, end sealing, repair, and splicing
Detailed methods for fiber-optic equipment
installation and cable entrance to equipment
Detailed methods to install fiber-optic cables in
Detailed methods for installing fiber-optic
connectors and other interconnections, such as
Detailed methods for testing fiber-optic cable
plants before, during, and after installation and
There are other standards that discuss fiber-optic
system installation. Many of these standards incor-
porate procedures for repair, maintenance, and testing.
The techniques developed for installing fiber-optic
hardware are not much different than for installing
hardware for copper-based systems: however. the
primary precautions that need to be emphasized when
installing fiber-optic systems are as follows:
Optical fibers or cables should never be bent at a
radius of curvature less than a certain value, called the
minimum bend radius. Bending an optical fiber or
cable at a radius smaller than the minimum bend radius
causes signal loss.
Fiber-optic cables should never be pulled tight or
fastened over or through sharp comers or cutting edges.
Extremely sharp bends increase the fiber loss and may
lead to fiber breakage.
Fiber-optic connectors should always be cleaned
before mating. Dirt in a fiber-optic connection will
significantly increase the connection loss and may
damage the connector.
Precautions must be taken so the cable does not
become kinked or crushed during installation of the
Figure 6-3.A schematic diagram of a point-to-point fiber-optic data link.