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Now that you have completed this chapter, let's review some of the new terms, concepts, and ideas that you have learned. Understanding the basics of fiber optic system classification, design, and installation is recommended before you begin studying specific fiber optic system applications.
A basic POINT-TO-POINT fiber optic data link consists of an optical transmitter, 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.
The term TOPOLOGY refers to the configuration of various equipments and the fiber optic components interconnecting them.
A LINEAR BUS TOPOLOGY consists of a single transmission line that is shared by a number of equipments.
A RING TOPOLOGY consists of equipments attached to one another in a closed loop or ring.
In the STAR TOPOLOGY, each equipment is connected to a common center hub. The center hub can be a passive fiber optic star coupler or an active equipment.
A TREE TOPOLOGY consists of a transmission line that branches, or splits.
FIBER OPTIC LINKS are classified according to the modulation type: either digital or analog.
DIGITAL MODULATION implies that the optical signal consists of discrete levels.
ANALOG MODULATION implies that the intensity of the optical signal is proportional to a continuously varying electrical input.
MODULATION is the process of varying one or more characteristics of an optical signal to encode and convey information.
A DIGITAL SIGNAL is a discontinuous signal that changes from one state to another in discrete steps.
BINARY, or two level, digital modulation is a popular form of digital modulation.
LINE CODING is the process of arranging symbols that represent binary data in a particular pattern for transmission. The most common types of line coding used in fiber optic communications include non-return-to-zero (NRZ), return-to-zero (RZ), and biphase, or Manchester.
DIGITAL TRANSMISSION offers an advantage with regard to the acceptable SNR at the optical receiver.
An ANALOG SIGNAL is a continuous signal that varies in a direct proportion to the instantaneous value of a physical variable.
Most ANALOG FIBER OPTIC COMMUNICATIONS SYSTEMS intensity modulate the optical source.
In INTENSITY MODULATION, the intensity of the optical source's output signal is directly modulated by the incoming electrical analog baseband signal.
A BASEBAND SIGNAL is a signal that is in its original form and has not been changed by a modulation technique.
FIBER OPTIC SYSTEMS that have complex architectures can be simplified into a collection of point-to-point data links.
LINK ANALYSIS involves calculating each link's power budget and risetime budget.
Calculating a POWER BUDGET involves identifying all of the sources of loss in the fiber optic link. These losses and an additional safety margin are then compared to the difference between the transmitter output power and the receiver sensitivity.
Calculating the RISETIME BUDGET involves calculating the risetimes of the link transmitter and the optical fiber.
The FIBER OPTIC CABLE PLANT consists of all the fiber optic cables and the fiber optic interconnection equipment within the ship, including connectors, splices, and interconnection boxes.
OPTICAL FIBERS OR CABLES should never be bent at a radius of curvature less than a certain value, called the minimum bend radius.
FIBER OPTIC CONNECTORS should always be cleaned before mating.