What is Optical Fiber Communication?

Communication in which information is transmitted from sender to receiver in the form of visible light or infrared through the glass medium known as optical fiber using a physical phenomenon called T.I.R. (total internal reflection). And the information is transmitted at the speed of light. Optical fiber is used over the electrical cables because it provides high bandwidth and low transmission losses for long distance communication. Also, immunity to electromagnetic interference is good. An optical fiber cable can contain lots of glass fibers inside, up to more than a hundred. Optical fiber is used to transmit voice, video and telemetry using local area networks.


What is Optical Fiber and its construction?

Optical fiber looks like a normal copper wire from outside, but it contains a glass core inside protected from different layers of materials as shown in the above image.

1. Core
2. Cladding
3. Buffer
4. Jacket

1.Core- Light in optical fiber travels inside the core because of total internal reflection. The light in the core travels when reflected from core-cladding boundary.

2.Cladding- Cladding surrounds the core and protects the core. It keeps light inside the core. It reflects light back to the core.

3.Buffer- Buffer protects the core from mechanical and environmental damage and provides strength to the fiber.

4.Jacket- Provides additional protection to the fiber. The outer jacket is color coded to recognize the type of fiber. The yellow color of jacket indicates that fiber is single-mode and orange color indicates multi-mode fiber. It helps a lot for the person dealing with optical fibers.

Working Principle of Optical Fiber

The propagation of light inside of an optical fiber is achieved by using a physical phenomenon known as T.I.R. (total internal reflection). Total internal reflection occurs if waves can form a narrow beam such as electromagnetic waves, light or sound waves and travel from denser to rarer medium. And the incident angle of wave should be greater than the critical angle.

Refraction- When the ray of light travels from denser to rarer medium it bends away from normal. As shown in the image below.


Critical Angle(Qc)- The angle of incidence for which the angle of refraction is 90 degrees as shown in the image below. The refracted ray of light travels from the interface.

Total Internal Reflection (TIR)- When the ray of light travels from denser to rarer medium at the angle more than the critical angle, then it returns to the same medium, called total internal reflection. It is the actual working principle of optical fiber communication. The core in the fiber carries the light and cladding surrounds the core. Cladding is made up of lower refractive index (rarer medium) material and core is made up of slightly higher refractive index (denser medium) material that is the proper conditions for internal refraction to happen inside the core.



Types of Optical Fibers

There are two main types of optical fibers-

Single Mode Fiber Optic Cable
Multi-Mode Fiber Optic Cable


Single Mode Fiber Optic Cable- It is also known as fundamental or mono-mode fiber optic cable. Mode in the fiber optics refers to the path of light traveling in the fiber. In single mode optical fiber only single wavelength of light travels through the fiber at a time. So, the attenuation is very less. Single mode fiber used for long distances. The core diameter of single mode fiber is between 8-10 microns. The capacity to transmit information of single mode fiber is high because it can retain the fidelity of each pulse over long distances.

Multi-Mode Fiber Optic Cable- In multi-mode fiber cable multiple wavelengths of light travel through the fiber at a time. Multi-mode fiber is mainly used for short distances such as in LANs (local area networks), within a building or campus. The core diameter of multi-mode fiber cable is larger than single mode fiber cable which allows larger numbers of modes in a single fiber at a time. Core diameter of multimode fiber is available in two sizes, 50 micron and 62.5 micron.

According to the variation in material composition of core or refractive index of the fiber multimode fiber can be divided into two types.

Step Index Multi-mode Fiber
Graded Index Multi-mode Fiber




Advantages of Optical Fiber Communication

High Bandwidth- The frequency range used in optical fiber communication provides a high bandwidth. The transmission at several gigahertz can be achieved over 100 km (about 62.14 mi) without using amplifiers or repeaters.

Low transmission losses- Transmission of data over optical fiber is immune to losses as compared to the best copper cables.

Security- Signal transmitted over the optical fiber is secure because it always remains within the cable.

Low Cost- Mainly glass is used to make fiber. And sand is used to make optical fiber cables. Sand is found in abundance. Due to this optical fiber is less costly line communication.

Flexibility and Rigidness- Optical fibers are made up from many different layers and materials which give rigidness. And these cables can be bent to a degree without damage.



Disadvantages of Optical Fiber Communication

Maintenance- To keep the optical communication working it requires time to time maintenance. Specific tools are used in maintenance and repair.

Initial Cost- Installation cost of optical fiber communication system is not that cheap it requires good amount of investment and time.

Skilled Labour- Skilled labor is required to keep communication working. Training and skill are required to reconnect the cables and connectors.

Attenuation and losses- Optical fibers are prone to attenuation as the light travels very long distances. And the dispersion of signal occurs when the light pulses spread out over the time when different wavelengths of light experience varying velocities as they travel through the fiber.

Prone to Damage- Optical fibers are literally made of glass and get easily broken when they get bent.



Applications Of Optical Fiber Communication

Communication- Optical fiber is used for communication to transmit data over long distances. Optical fiber is back bone of internet and data servers. Optical fiber provides high speed communication. Optical fibers are used for communication because it is immune to electromagnetic interference. Optical fibers are used in broadband services to provide high speed data access to the public via LANs (local area networks).

Medical Use- Optical fiber is used in medicine to take images of organs inside of the human body. It is used to study and research biology because the small dimensions of it help to reach inside. Because fiber is thin and flexible.

Military Applications- Optical fibers are also used in the military. Because security is very important during data transmission, communication, command and control links on ships and aircraft.

Broadcasting- Optical fiber cable can be used to broadcast high-definition television signals. Optical fiber provides better signal to noise ratio. It also reduces the interference.