Basic Construction of Optical Fibre

1. Core:

The centre of the fibre through which the light is transmitted.

2. Cladding:

The outside optical layer of the fibre that traps the light in the core and guides it along and even through curves.

3. Buffer coating or primary coating:

A hard plastic coating on the outside of the fibre that protects the glass from moisture or physical damage.
        Fiber optic cable functions as a "light guide," guiding the light introduced at one end of the cable through to the other end. The core and cladding are manufactured together as a single piece of silica glass. The core region’s refractive index (or optical density) is greater than the cladding layer. The glass does not have a hole in the core, but is completely solid throughout. The light is "guided" down through the core. The cladding traps the light in the core using an optical technique called "total internal reflection.” The third section of an optical fibre is the outer protective coating called the "primary buffer coating". This coating is typically an ultraviolet (UV) light-cured acrylate applied during the manufacturing process to provide physical and environmental protection for the fibre. During the installation process, this coating is stripped away from the cladding to allow proper termination to an optical transmission system.