Optical Fiber

Optical fiber is a transparent and flexible fiber made up of plastic or glass, which carries information in the form of light pulses from one end of the fiber to another. Fiber optics is used for long-distance, and high-performance networking.

Optical fibers are usually used in telecommunication services like internet, telephone, and television.

Fiber optic cables have many advantages as compared to copper cables. It has higher bandwidth and transmits information much faster.

An optical fiber contains a number glass which may vary from a few to a few hundred. A layer of glass called cladding surrounds the glass fiber core of the fiber cable. There is also a protective layer around the cladding known as a buffer tube. A final protective layer of the strand is present which is called the jacket layer.

  • Core - This is a thin glass present at the center of the fiber where the light travels.

  • Cladding - This is the outer material that surrounds the inner glass core. It reflects the light back into the core.

  • Buffer Coating - This is a plastic coating that protects the fiber from external damage and moisture.

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Thousands of these kinds of optical fibers are arranged in bundles called optical cables. An outer covering called jacket protects these bundles.

Working of Optical Fiber

Fiber optics transfer data in the form of photons by converting the light particles into light pulse through an optical cable. An optical fiber consists of two parts, an inner glass fiber core, and an outer cladding. Each of them has a different refractive index to bed the incoming light.

When a pulse of light is passed through the optical fiber, it is reflected and bounced by the core and the cladding on a zig-zag motion by a process called total internal reflection. Total internal reflection can be defined as a phenomena that happens when light rays travel from an optically denser medium to an optically less denser medium.

The light signals travel at around 70% of the speed of light due to the denser medium. Optical fiber usually consists of repeaters at distant intervals to boost the signal strength and convert it to an electrical signal. This electrical signal is then processed and used for transmitting optical signals.

Principle of Optical Fiber

An optical fibre is a thin thread of lengthy, thin material, which is usually in the shape of a cylinder. Its core is located at the center and has a layer of the outer protective covering called cladding. The core and the cladding, both are made up of different materials. When light travels through the core, it travels very slowly and then transmitted to the cladding. The cladding further reflects light back to the core, and so on.

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When light from the core strikes the border of the cladding, with an angle less than 90°, it bounces off. Light is not escaped in any way, and it only comes out from the end of the fiber. The cladding of the cable usually gets damaged if it gets scratches. To protect this damage, a plastic coating like the buffer is applied to protect the cladding. This buffered fiber is normally located in a tough layer known as the jacket. So the fiber functions easily without any damage.

Types of Optical Fiber

Optical fibers are of two types:

  • Single-mode fibers

  • Multi-mode fibers

  1. Single-mode optical fibers are used for long-distance information transformation. It has a small diameter in the glass fiber core due to which it lessens the possibility of attenuation, i.e the reduction in signal strength. The smaller end of the fiber converts light into a single beam and focuses it into a direct route to make it travel a long distance. Single-mode fiber has more bandwidth as compared to multi-mode bandwidth. The laser is used as the light source in this mode. Single-mode optical fibers are much more expensive as it involves precise calculations to produce light in small openings.

  2. Multi-mode optical fiber has a larger core opening that bounces and reflects throughout the path, transmitting it through a shorter distance. Due to its larger diameter, multiple light beams can be sent at a time and hence more data transmission occurs. Signal loss, interference, and reduction is more in this case. An LED is usually used in a multimode optical fiber to create a light source.

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The classification of optical fiber is done in terms of refractive index as follows:

  • Step Index Fibers: The step-index fibers consist of a core, which is surrounded by a cladding having a uniform index of refraction.

  • Graded Index Fibers: In the graded-index fibers, the refractive index of the optical fiber gradually decreases as the radial distance from the axis of the fiber increases.

The classification of optical fiber based on the materials used is as follows:

  • Plastic Optical Fibers: In the plastic optical fibers, polymethylmethacrylate is used as the core material to carry out the transmission of light.

  • Glass Fibers: The glass fibers optical fiber is made up of extremely fine glass fibers.

FAQ (Frequently Asked Questions)

1. What are the Uses of Fiber Optics?

Ans- Computer networking is one of the major uses of fiber optics in which data is transmitted at a higher bandwidth. 

Fiber optics are also used in electronics and broadcasting to maintain better connection and performance. Internet, cable, and televisions are also the most common uses of fiber optics.


Fiber optics can also be used for long-distance connections of a computer network to different locations.

Military and space agencies use fiber optics for communication and for transferring signals. It is also used for temperature sensing.

2. Advantages of Optical Fiber Communication.

Ans- The major advantages of optical fiber are:

  • Economical and cost-effective

  • Less power consumption

  • Thin and non-flammable

  • Less signal degradation

  • Flexible and lightweight

3. Disadvantages of Optical Fiber Communication.

Ans- The major disadvantages of optical fibers are:

  • The optical fiber cables are very difficult to merge into each other and there might be loss of the light beam within the cable while scattering.

  • The Installation of optical cables is very expensive. Special test equipment is needed to install the optical fibers.

  • Fiber optic cables are compact and are very highly vulnerable while fitting.

  • The optical fiber cables are more delicate as compared to copper wires.

  • Special devices are required to analyze the transmission of light through the fiber cables.