What is an Optical fiber & its Construction [Basics]

What is an optical fiber?

what is an optical fiber ? Typically, fiber optics are long, thin strands of glass (SiO2) about the diameter of human hair; some can be made out of plastic. Long distance telecommunication systems always use glass because of its lower optical absorption during transmission to maintain the signal strength. When arranged in bundles, they are called optical cables which are used to transmit light signals containing information over long distances.

Construction of optical fiber:

Parts of an optical fiber

1 Core
2 Cladding
3 Buffer
4 Jacket


The core of a fiber cable is a cylinder of plastic or silica or glass that runs all along the fiber cable’s length, and offers protection by cladding. The diameter of the core depends on the application used. Due to internal reflection, the light travelling within the core reflects from the core and the cladding boundary. The core cross section needs to be a circular one for most of the applications.

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Cladding is an outer optical material that protects the core. The main function of the cladding is that it reflects the light back into the core. When light enters through the core (dense material) into the cladding(less dense material), it changes its angle, and then reflects back to the core.

Buffer jacket

The main function of the buffer is to protect the fiber fromdamage while arranged in optical cables. These bundles are protected by the cable’s strength members covering.

Outer jacket

Fiber optic cable’s jackets are available in different colours that can easily make us recognize the exact colour of the cable we are dealing with. The colour yellow clearly signifies a single mode cable, and orange colour indicates multimode. It is also given mechanical strength to the optical cables.

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