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CompTIA A+ Certification All-in-One Exam Guide

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Light can be sent down a fiber optic cable as regular light or as laser light.

Each type of light requires totally different fiber optic cables. Most network

technologies that use fiber optics use light-emitting diodes (LEDs) to send

light signals. These use multimode fiber optic cabling. Multimode fiber

transmits multiple light signals at the same time, each using a different

reflection angle within the core of the cable. The multiple reflection angles

tend to disperse over long distances, so multimode fiber optic cables are used

for relatively short distances.

EXAM TIP Know fiber connector types and the difference between

multimode and single-mode fiber.

Network technologies that use laser light use single-mode fiber optic

cabling. Using laser light and single-mode fiber optic cables allows for

phenomenally high transfer rates over long distances. Except for longdistance

links, single-mode is currently quite rare; if you see fiber optic

cabling, you can be relatively sure it is multimode.

There are close to 100 different Ethernet fiber optic cabling standards,

with names like 1000BaseSX and 10GBaseSR. The major difference is the

speed of the network (there are also some important differences in the way

systems interconnect, and so on). If you want to use fiber optic cabling, you

need a fiber optic switch and fiber optic network cards.

Fiber networks follow the speed and distance limitations of their

networking standard, so it’s hard to pin down precise numbers on true

limitations. Multimode overall is slower and has a shorter range than singlemode.

A typical multimode network runs at 10, 100, or 1000 Mbps, though

some can go to 10,000 Mbps. Distances for multimode runs generally top out

at ~600 meters. With single-mode, speed and distance—depending on the

standard—can blow multimode away. The record transmission speed way

back in 2011, for example, was 100 terabits per second and that was over 100

miles!

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