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Phyics of Fiber Optics

FiberHelp is a free resource site dedicated to the one thing that powers the Internet and enables those blazing fast speeds, Fibre Optic Cables!

This page is dedicated to the Physics of Fibre Optics. We will give a brief overview, without getting into the nitty gritty of optics, refraction, reflection and all those other things that kept us up at night before Physics tests in school.

Fibre optic cable is essentially a long thing glass tube (although this glass tube is less than the width of a piece of string!). Over this glass 'tube' there is a protective cover like all wire, electrical or optical. We then use a device to 'shoot' infrared light down this tube. For the physics geeks out there, the wavelengths we will typically use are 850nm, 1300nm and 1550nm. As a note, a nm is a Nano Metre, which is billionths of a metre! Generally humans can see light visible in the 400-700 nm range.

We can send this light (and this light ultimately is your internet transmissions!) a long distance because there is very little attenuation in the cable, unlike Cat5/6 which can only go 90m (300 feet) due to attenuation. As clean as the glass 'tube' in the fibre is, there is slight bit of attenuation due to slight minute water vapour or air bubbles in the glass.

So this glass cable/tubing.. Is it fragile and suseptable to damage? We it's not that fragile, but a good shovel or a backhoe can damage or break a fibre cable. We will talk more about construction and how we protect these glass fibre cables we have running all over the world. (and down your street!)

If you have any questions, comments, or suggestions, feel free to email us at: Thanks and enjoy the site!

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