What Is Optical Fiber?


What is an Optical Fiber?

Optical fiber is the technology associated with data transmission using light pulses travelling along with a long fiber which is usually made of plastic or glass. Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages. Optical fibers are also unaffected by electromagnetic interference. The fiber optical cable uses the application of total internal reflection of light. The fibers are designed such that they facilitate the propagation of light along the optical fiber depending on the requirement of power and distance of transmission. A single mode fiber is used for long-distance transmission while a multimode fiber is used for shorter distances. The outer cladding of this fibers needs better protection than metal wires.

How Does an Optical Fibre Work?

The optical fiber works on the principle of total internal reflection. Light rays can be used to transmit a huge amount of data but there is a problem here – the light rays travel in straight lines. So unless we have a straight long wire without any bends at all, harnessing this advantage will be very tedious. Instead, the optical cables are designed such that they bend all the light rays’ inwards (using TIR). Light rays travel continuously, bouncing off the optical fiber walls and transmitting end to end data. Although light signals do degrade over progressing distances, depending on the purity of the material used, the loss is much less compared to using metal cables. A Fibre Optic Relay System consists of the following components:

  • The Transmitter – It produces the light signals and encodes them to fit to transmit.
  • The Optical Fibre – The medium for transmitting the light pulse (signal).
  • The Optical Receiver – It receives the transmitted light pulse (signal) and decodes them to be fit to use.
  • The Optical Regenerator – Necessary for long distance data transmission.

Types of Optical Fibers

Optical fibers are classified into different types based on the refractive index, materials used and mode of propagation of light.

The classification based on the refractive index is as follows:

  • Step Index Fibers
  • Graded Index Fibers

The classification based on the materials used is as follows:

  • Plastic made Fibers
  • Glass made Fibers

The classification based on the mode of propagation of light is as follows:

  • Single Mode Fibers
  • Multimode Fibers

The mode of propagation and refractive index of core is used to form four combination types optic fibers as follows:

  • Step index-single mode fibres
  • Graded index-Single mode fibres
  • Step index-Multimode fibres
  • Graded index-Multimode fibres

Advantages of Optical Fibre Communication

  • Economical and cost effective
  • Thin and non-flammable
  • Less power consumption
  • Less signal degradation
  • Flexible and lightweight

Learn more about optics, fiber optics, its application and about multimode fibers from our expert tutors at BYJU’S.

Optical Fibre Important Questions

Q1. What is optical fibre?

Ans: Optical fibre is defined as a pure glass strand which flexible and transparent and acts as a light pipe to transmit light between the two ends of the fibre.

Q2. What is used for the fabrication of optical fibers that are used for communication?

Ans: Silica or multicomponent glass are used for the fabrication of optical fibers.

Q3. Why silica is used for the fabrication of the optical fibers?

Ans: Silica has a perfect elasticity until it reaches the breaking point which makes it best for the fabrication.

Q4. What is the principle of fiber optical communication?

Ans: Total internal reflection is the principle on which the optical fiber communication is based.

Q5. Name the factors that are responsible for generating attenuation of optical power in fiber.

Ans: Following are the factors that are responsible for generating attenuation of optical power in fiber:

  • Absorption
  • Scattering
  • Waveguide effect

Q6. Why are plastic clad silica fiber optic cables not user-friendly?

Ans: Following are the reasons why plastic clad silica fiber optic cables not user-friendly:

  • The fibers are insoluble in organic solvents
  • Bonding becomes difficult
  • Connector application becomes difficult as there is excessive plasticity in the cladding

Q7. What is Raman effect?

Ans: Raman effect is the change in the wavelength of light which occurs when the light beam is deflected by the molecules.

Q8. What are the benefits of optical fiber cable?

Ans: Following are the benefits of optical fiber cable:

  • The data security is excellent
  • It is cost effective
  • It won’t be affected by interference.

Q9. What is the bandwidth of optical fiber?

Ans: 900 THz is the bandwidth of optical fiber.

Q10. What is core in the optical fiber?

Ans: Core is the inner part of the optical fiber which carries light.

Optical Fibre Questions

Q1) What is an optical fibre?

Answer:

An optical fibre is a thin transparent fibre that is associated with data transmission using light pulses travelling along with a long fibre that is usually made of plastic or glass.

Q2) Name the different types of optical fibre.

Answer:

Optical fibres are classified into different types based on the mode of propagation of light, refractive index and materials used as follows:

Based on the mode of propagation of light:

  • Single mode fibres
  • Multimode fibres

Based on the refractive index:

  • Graded Index Fibre
  • Step Index Fibre

Based on the materials used:

  • Plastic made fibres
  • Glass made fibres

Q3) List a few advantages of optical fibre communication.

Answer:

A few advantages of optical fibre communication are:

  • Less signal degradation
  • Thin and non-flammable
  • Economical and cost effective
  • Less power consumption

Q4) List a few disadvantages of the optical fibre.

Answer:

A few disadvantages of the optical fibre are as follows:

  • Optical fibres are fragile and are more vulnerable to damage than copper.
  • As the transmission distance gets longer, the signal will be attenuated and dispersed. This requires extra optical equipment like EDFA to be added.
  • Higher cost than copper
  • It is difficult to install

Q5) Optical fibre works on the principle of _____.

Answer: total internal reflection

Optical fibre works on the principle of total internal reflection.

Q6) Does information travel faster in optical fibre than a copper wire?

Answer:

Q7) The most important parameter to consider while installing optical fibre in a working environment is

  1. Core cladding ratio of the fibre
  2. Mechanical property of the fibre
  3. Numerical aperture of the fibre
  4. Transmission property of the fibre

Answer: b. The mechanical property of the fibre

Q8) List the components in a fibre optic relay system.

Answer:

The fibre optic relay system consists of the following components:

  • Transmitter – Produces light signal
  • Optical Fibre – a medium used to transmit light signals
  • Optical receiver – receives the transmitted light signal and decodes them
  • Optical regenerator – necessary for long distance data transmission

Q9) The refractive index in the graded index fibre varies _____.

  1. radially
  2. tangentially
  3. transversely
  4. longitudinally

Answer: a. radially

The refractive index in the graded index fibre varies radially.

Q10) A multimode fibre has more intermodal dispersion than a single mode fibre.

  1. True
  2. False

Answer: a. True

Multimode fibre has more intermodal dispersion than a single mode fibre.


Practise This Question

A glass prism of refractive index 1.5 is immersed in water (μ=43). A light beam incident normally on the face AB is totally reflected to reach the face BC if