Chapter 26Long-haul equipment (Fiber-optic cables)Fiber-optic cable VS Copper wireHow does it all work?Slide 5From Analog to DigitalSending an E-mailChapter 26 Shedding Light on CommunicationsPresented by Pete LeFebvreLong-haul equipment(Fiber-optic cables)Fiber-optic cables can transmit light signals for thousands of miles (with the assistance of optical regenerators.Fiber-optic cable VS Copper wireTelephones transmit encoded signals through copper wire using electrical current.This current creates a magnetic field that may lead to interference otherwise known as noiseDue to this noise the signal must be regenerated every mile or soFiber optic cables eliminate noise and improve the clarity of the signal.Optical regenerators are only necessary every 50-60 milesHow does it all work?Visible light moves very fast (about 186,000 miles, per second in a vacuum. Light radiates in all directions until it strikes an object and is either absorbed, reflected, or refractedAbsorbtion—the energy of a light wave is transferred to and heats up an objectReflection—the energy of a light wave bounces off an objectRefraction—light traveling in one medium passes into another and bends at the intersection of the two materials-Fiber optic cable takes advantage of total internal reflection, where the all the light is bent and reflected backHow does it all work?Fiber optic cable takes advantage of total internal reflectionA cable consists of a bundle of very thin fibers or strands of glass. Each of these fibers (aka core) is coated with a glass material called cladding.When light enters the fiber it is angled towards the cladding where it is reflected (because the speed of light is significantly different between the two materials).Total internal reflection occurs as the cladding reflects the beam into the center of the core keeping the beam focused and strong.Due to the inevitable impurities that exist within these cables the signal must be strengthened occasionally using an oprtical regeneratorFrom Analog to DigitalTo send a light signal:A transmitter translates an analog electric signal into a matching digital pattern that turns a laser on and off.These flashes occur within a small fraction of a second so large quantities of information can be sent quickly.At the end of the cable a light sensitive cell receives the light signal and translates it back into an electrical signalSending an E-mailWhen using a cable connection the information is transferred even faster because the computer bypasses the telephone system and connects directly to the
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