OPTICAL FIBRE
An optical fibre is a thin strand of glass or plastic that serves as a transmission medium over which the information passes. To be more technical, an optical fibre
is a dielectric waveguide that operates at optical frequencies (1013 to 1016 Hz) and transfers information in the form of light by the mechanism of total internal reflection. The optical fibre consists of a central core surrounded by a cladding layer.
Types of Optical Fibres
The different types of optical fibres are,
- Step index and Graded index fibre based on refractive index profile
- Single-mode and multimode fibre based on the number of modes
- Glass, Plastic clad and All plastic fibres based on material
Comparison
A detailed comparison of different types of optical fibres is presented below:
1. Step Index and Graded Index Fibre
This classification is based on the refractive index profile of the core and cladding. The refractive index or Index of Refraction is the fundamental optical parameter of a medium. The value of the refractive index shows how a ray of light travels in a medium.
2. Single Mode and Multi Mode Fibres
Mode describes the path of propagation of light rays along the optical fibre. The pattern of light ray propagation classifies fibres into single-mode and multi-mode.
3. Glass, Plastic Clad and All Plastic Fibres
An optical fibre is usually made of glass. It can also be made out of plastic in order to add strength to it. Based on the material of fabrication of optical fibre, it is categorised into Glass, Plastic clad and All plastic fibres.
Glass fibres | Plastic clad fibres | All plastic fibres |
In glass fibres, both the core and cladding are made of glass consisting of either silica or silicate. | Plastic-clad fibres have a plastic cladding made of silicone rubber and a glass core made of silica. | All plastic fibres have plastic cores and cladding. |
Glass fibres resist deformation at temperatures as high as 1000˚C, and thermal shock and are highly transparent. | These fibres exhibit lower radiation-induced losses and have improved performance. | The plastic core and cladding reduce the requirement for a buffer jacket for fibre protection. |
Losses are less. | Medium losses | High losses |
Mechanical strength is poor. | Mechanical strength is medium | Large mechanical strength. |
These are used for long-distance communication because of low losses. | These are used for medium-distance communication. | These fibres are used for very short-haul low-cost links. |
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