Page 18 - Optical Switching And Networking Handbook

Introduction to Optical Communications 3

true! Probably all of us have picked up a trade magazine and seen a
feature article written by some VP of engineering at a local manu-
facturer. The article presents several different acronyms and offers
several opinions about the product or service. Yes, there is merit in
the article, but too often there is so much jargon that readers have a
tendency to put the article aside. What a sad thing it would be to
have a communications industry that cannot communicate. It is for
this reason that McGraw-Hill keeps asking for help in offering some
semblance of understanding of industry techniques. One hopes that
such understanding will result from this book as it has with the past
ones.

Transmission System Terms

Before discussing the fiberoptic world, I should at least describe
some very basic terms. These will help you to understand the world
of fiber. There are many other ways of describing the use of fiber, but
these definitions will aid in rudimentary understanding.

Amplifier This device increases the power of an electromagnetic
wave, such as sound or light, without distorting it, as shown in Fig-
ure 1-1. Your stereo amplifier takes the weak radio signals from the
air and boosts them so that they are strong enough to drive the
speakers. Amplifiers in fiberoptics systems do almost the same
thing—they brighten the light passing through the fibers.

Coaxial cable Coaxial cable is a high-frequency transmission line
that is used to send telephone and television impulses. The CATV
companies use a single cable to deliver multiple channels of TV by
employing a multiplexing technique that separates the signals by
frequency. See the representation of coaxial cable in Figure 1-2.

Modulator A modulator is a change agent. This device converts
(changes) electrical on/off pulses into sound pulses for voice tele-
phone calls. The modulator in a fiberoptic system does the same
thing, except that it converts the electrical pulses into pulses of light,
as shown in Figure 1-3. A modulator-demodulator (called a modem)