Monday, November 28, 2016


These days fiber optic cables are used everywhere to connect our modern world and are able to send information across countries and vast oceans, but how do they work? Let’s get stuck in and find out how fiber optics work.

How They Work

Fiber optics are fairly simple to understand on a basic level. Essentially information in the form of light is sent from one place to another, this is generally done through fiber optic cable. The beauty of this comes from something known as Total Internal Reflection (TIR), what this means is that the light is able to be sent through a flexible fiber optic cable by simply ‘bouncing from one surface to another’ until it reaches it’s destination.

Reflection vs Refraction

Any time light strikes a surface it can either be reflected from it (reflection) or pass through it (refraction). The key to transmission of light via fiber optics is to ensure that light hits the surface greater than the critical angle to ensure complete reflection and not refraction. This requires quite a bit of mathematics, but to simplify it one should ensure that the angle of the surface the light hits is not too great so as to ensure reflection takes place and not refraction.

Understanding the Structure of Fiber Optic Cable

Fiber optic cable typically contains a core made of ultra-pure glass  which is then surrounded by an outside layer of glass known as cladding. The cladding is designed manufactured in such a way as to decrease it’s index of refraction by using small bits of boron or germanium. The core and cladding are manufactured as a very long, thin piece of glass that is made by heating what is know as a preform with the center being the pure glass core and the outside is the cladding. It is then stretched to an length of unusually around  18.2 m (60 ft).

Sending Data by Light

Data is sent and received in our modern society in what is known as binary numbers, essentially 1’s and 0’s. Think of it as a light switch with 2 settings, either On (1) or Off (0). If you turn the light on and off at the switch with a specific pattern it can be used to form somewhat complex messages. Such as the example one below:

Data is sent similarly through fiber optic cable in the form of laser light pulses using what is known as Pulse Code Modulation or PCM. Unfortunately this is a lengthy topic and this will be adiscussed in a future article.

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