Page 169 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Main element of Fiber Optics:
Core: It is the central tube of very thin size made of optically transparent dielectric medium and carries the light
transmitter to receiver and the core diameter may vary from about 5um to 100 um.

Cladding: It is outer optical material surrounding the core having reflecting index lower than core and cladding
helps to keep the light within the core throughout the phenomena of total internal reflection.
Buffer Coating: It is a plastic coating that protects the fiber made of silicon rubber. The typical diameter of the
fiber after the coating is 250-300 um.

Types of Fiber optics:
On the basis of the Number of Modes:

1 Single-mode fiber:
In single-mode fiber, only one type of ray of light can propagate through the fiber. This type of fiber has a small
core diameter (5um) and high cladding diameter (70um) and the difference between the refractive index of core
and cladding is very small. There is no dispersion i.e. no degradation of the signal during traveling through the
fiber. The light is passed through it through a laser diode.

2 Multi-mode fiber:

Multimode fiber allows a large number of modes for the light ray traveling through it. The core diameter is generally
(40um) and that of cladding is (70um). The relative refractive index difference is also greater than single mode
fiber. There is signal degradation due to multimode dispersion. It is not suitable for long-distance communication
due to large dispersion and attenuation of the signal. There are two categories on the basis of Multi-mode fiber
i.e. Step Index Fiber and Graded Index Fiber. Basically these are categories under the types of optical fiber on
the basis of Refractive Index

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CITS : E & H - Electronics Mechanic - Lesson 94 - 99