Optical Fibres: Meaning, Types and Advantages | Material Science

In this article we will discuss about:- 1. Meaning of Optical Fibres 2. Types of Optical Fibres 3. Advantages.

Meaning of Optical Fibres:

Optical fibres are extremely fine and flexible rods of glass. They are optical transmission medium used for the purpose of communicating the light,

These fibres function as an optical waveguide with a transmitter and a detector. Light propagates through it by total internal reflection and refraction.

During operation, they are placed between a light source and detector for transmission of signals.

The operation of optical fibers is based on the principle of ‘total internal reflection and refraction’ at the interface between high refractive index core and lower refractive index cladding of pure glass.

Types of Optical Fibres:

On the basis of construction and operation, the optical fibres can be categorized into following two types:

1. Monomode Fibres:

In which the diameter of inner core is comparable with the wavelength of light. Hence, only one mode of light propagates through it.

2. Multimode Fibres:

In which the diameter of core is sufficiently larger than the wavelength of light. Hence, the light propagation takes place in a large number of modes.

The multimode fibres, on the basis of refractive index μ of the core, may be further divided into following two types:

(i) Step-index type, and

(ii) Graded-index type

Optical Fibres Material should have:

(i) High purity, having impurities to the level of less than 1 ppm.

(ii) Low loss.

(iii) Low-dispersion.

(iv) High refractive index for core materials.

(v) Low refractive index for cladding material.

Materials Used in:

i. Fiber of highly pure glass.

ii. Core made of vitreous high-silica glass doped with germanium oxide (Ge₂0) i.e. Germania.

iii. Jacket of plastic, glass of rubber.

Advantages of Optical Fibres:

i. They are of miniature size.

ii. They are immune to cross-talks

iii. They are least subjected to electromagnetic interference

iv. They are capable of carrying much more information for a given cross-section of fibre, than can be transmitted via the conventional coaxial cable.

v. They can guide the optical signals over long distances (Many kilometres) without the necessity of perfect alignment between source and detector.

vi. Dark resistance of a photoconductor- It is the resistance of a photo-conducting cell when it is un-illuminated. Dark resistance is always higher than the bright resistance (i.e. the resistance of the cell when illuminated).