An optical fiber is a cylindrical dielectric waveguide that transmits _____ along its axis.

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RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 2)

Answer 1

Optical fiber

An optical fiber is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair.
Optical fibers are used to transmit light between the two ends of the fiber and have wide usage in fiber-optic communications.
They permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables.
Fibers are used instead of metal wires because signals travel along them with less loss. In addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer.
An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis through the process of total internal reflection.
The fiber consists of a core surrounded by a cladding layer, both of which are made of dielectric materials. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding.

Construction of optical fiber

F2 Savita Engineering 31-3-23 D2

A fiber optic cable consists of five main components: core, cladding, coating, strengthening fibers, and cable jacket.

1.) Core:

This is the physical medium that transports optical signals from an attached light source to a receiving device.
The core is a single continuous strand of high-purity glass or plastic whose diameter is measured in microns (less than the diameter of a human hair).
The larger the core, the more light the cable can carry, which correlates to a higher data transfer rate.

2.) Cladding:

This is a thin layer that is extruded over the core and serves as the boundary that contains the light waves (more on this later), enabling data to travel through the length of the fiber.

3.) Coating:

This is a plastic coating over the cladding to reinforce the fiber core, help absorb shocks, and provide extra protection against excessive cable bends.
It does not have any effect on the optical waveguide properties, though.

4.) Straightening fibre:

These components help protect the core against crushing forces and excessive tension during installation.
Sometimes light-absorbing (“dark”) glass is added between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers.

5.) Cable jacket:

This is the outer layer, or sheathing, of the cable.
Its purpose is to protect the cable from environmental hazards, such as construction work, fishing gear, and even sharks, which are often attracted to the electrical fields created by signal conductors to repeaters.