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Introduction to Fibre Optics

Chris Angle
5 May 2020

Introduction to Fibre Optics

Optical fibre is made up of 2 glass elements. Core and Cladding. The core is the area which the light beams travel through. The cladding protects the core and stops the light beams from escaping.

Information is transmitted along the glass cables in a series of light pulses. The light pulses can follow a variety of paths. There are 3 factors which can affect the speed and capacity of data transfer. Attenuation, Dispersion & bend induced loss. 

Attenuation happens when signal is lost as light becomes dimmer as it travels through the fibre. This can be caused by bends of the glass or quality of the glass. Dispersion is the corruption of the signal due to the different spectral components of the light travelling at different speeds.

Bend induced loss is the loss of signal due to the micro and macro bending. The light travels along the optical fibre and hits the boundaries at steep angles, this creates Total Internal Reflection – which keeps the signal from escaping. The glass used in the core has higher Index of Refraction (IOR) than the glass used in the cladding. This means the light is trapped in the core and can travel along the fibre without loss of signal.

There are 2 types of fibre: single mode and multi-mode.

  • Single mode – small diameter core, light signals on a single path, high capacity, low attenuation. 
  • Multi-mode – Large diameter core, light signals on multiple paths, used over short distances.