Optic Fibres

How does it work?

You hear about fiber-optic cables whenever people talk about the telephone system, the cable TV system or the Internet. Fiber-optic lines are strands of optically pure glass as thin as a human hair that carry digital information over long distances. They are also used in medical imaging and mechanical engineering inspection.

Relation to Snell's Law

Snell's Law, named after the Dutch mathematician Willebrord van Roijen Snell, states that the product of the refractive index and the sine of the angle of incidence of a ray in one medium is equal to the product of the refractive index and the sine of the angle of refraction in a successive medium. This can be represented algebraically by n1 sin1 = n2 sin2, where n1, n2 are the two values of refractive index and1,2 are the angles of the incidence and refraction. 

Optical Fibres relies heavily on two concepts of physics, the concepts of refraction, refractive indexes, critical angles and Total Internal Reflection. The concepts of refraction states that a ray of light travelling from a medium with a higher refractive index to a medium with a lower refractive index would bend away from the normal. With this in mind, it also states that a critical angle would be reached when the ray of light increases to an angle that will bend it 90 deg. away from the normal. The concept of Total Internal Reflection is apparent when the ray of light travelling from a higher refractive index medium to a lower refractive index medium has an angle so great it is able to refract the light greater than the critical angle, resulting in the ray reflecting back into the first high refractive index medium.

When the fiber is bent.