Optical Fibre: Definition, Structure, Propagation

Optical Fibre: Definition, Structure, Propagation

Optical fibre has completely revolutionised the communications industry. Various industries use it for varying purposes. If you wish to understand its specifics, such as the structure of optical fibre and much more, continue reading this post. The Schneider Electric team is here with this exclusive post to help you learn everything about optical fibre. So, start reading below. 

What is an Optical Fibre?

Made with glass (silica) or plastic, optical fibre is a thin and flexible strand. It is primarily used for the transmission of optical (light) signals. Usually, these strands have a diameter larger than that of human hair. In a more technical way, we can say that an optical fibre is a waveguide that transmits electromagnetic waves at optical frequencies. These electromagnetic waves are in the form of light. 

Structure of Optical Fibre

In the most simple words, the construction and working of optical fibre is based on its simple structure, which consists of a core and cladding. Its core is a cylindrical dielectric made with glass. Light propagates through this glass, which is enclosed in a plastic cladding. This entire structure is surrounded by an elastic jacket to protect the fibre. 

In the structure of optical fibre, cladding usually does not participate in lightwave transmission. This is because light only propagates through the core. However, the combination of the core and cladding is of utmost importance in reducing the signal losses due to scattering. The optical fibre is composed in a way that its core refractive index is much more than the refractive index of the cladding. 

Propagation of Light Ray Through an Optical Fibre

Optical fibre facilitates the transmission of a signal in the form of photons or light. But how is this propagation of light rays through an optical fibre carried out? The right answer to this question is- total internal reflection. 

When light gets transmitted through an optical fibre, it travels only through the core. This results in the light experiencing continuous reflections from the cladding. These reflections are the total internal reflections. These reflections happen only when light incident from a denser medium to a rarer one with an angle of incidence larger than the critical angle. 

The larger angle of incidence propagates light through the core by making successive reflections instead of being refracted at the cladding. The core of the fibre is a cylinder with a smaller diameter. As a result, only a small reflection of the light ray occurs. This leads to the incident angle being greater than the critical angle.

Modes of Propagation in Optical Fibre

When light travels along the optical fibre, it can take single or multiple paths. Therefore, the modes of propagation in optical fibre can be categorised into single and multiple modes. The single-mode fibre propagates the light ray in the fibre only through a single path. However, in multimode fibre, the larger core diameter allows the propagation of light rays through multiple paths. 

Optical Cable Advantages & Disadvantages

Now, it's time for you to understand the advantages and disadvantages of optical fibre.

Advantages of Fibre Optic Cable

Low Electrical Interference

Fibre optic cabling is composed of small strands of glass which carry electronic data signals by light. This particular design ensures immunity from electronic interference, a typical problem with conventional metal-based wiring. Metal cables are able to get electromagnetic radio and interference frequency signals, possibly causing data corruption and slowing network performance. Fibre optics, nonetheless, practically eliminate these risks, providing a reliable and stable connection without the worry of data loss or perhaps corruption. This results in far more consistent network performance and a considerable decrease in transmission errors.

Low Power Loss

Optical fibres are much less susceptible to power loss, allowing them to transmit information over greater distances. In comparison to copper networks, which are generally restricted to a maximum range of one hundred metres, optical fibre is able to include ranges of as many as two kilometres with no substantial signal degradation.

Reduced Latency and Faster Speeds

A vital advantage of fibre optics is the ability to deliver reliable and fast communication. Unlike typical copper wires, fibre optic lines are unaffected by outside sources like vehicle traffic or any other electrical disruptions, assuring an interference-free and stable connection.

Some other advantages of optical fibre include improved reliability, high scalability, enhanced flexibility and durability. 

Disadvantages of Optical Fibre

Challenging to Splice

Optical fibres are difficult to isolate, and light scattering in the fibres can lead to substantial signal loss. Furthermore, they have a constrained bending tolerance; bending or twisting them too much can easily result in breakage.


Fibre optic cables are manufactured of glass, and that is significantly a lot more flimsy compared to conventional electrical conductors such as copper wiring. This particular fragility makes them prone to different types of harm, such as degradation by chemicals such as hydrogen gas, that may hinder signal transmission. Given their vulnerability, installing fibre optic cables underwater demands specialised techniques and meticulous care to make sure they stay functional and intact.

Highly Susceptible

Fibre optic cables are lightweight and compact, though they're extremely prone to damage from cuts or other disruptions during installation or construction work. Thus, when working with fibre optics as the transmission medium, it is essential to have distinct techniques for maintenance and backup.


Summing Up

The vast world of electrical components has a lot for you to discover. One such crucial element is an optical fibre. It has completely revolutionised various industries. If you are looking forward to buying the best optical fibre, order online from the e-shop of Schneider Electric to get the best quality and relish all the advantages of fibre optic cable. 

Frequently Asked Questions

Q1. What is an Optical Fibre?

Ans: Optical fibre is made with glass (silica) or plastic. It is a thin and flexible strand used for the transmission of optical (light) signals.

Q2. What are the applications of Optical Fibres?

Ans: Optical fibres usually have the following applications-

  • Telephone
  • Medical Applications
  • CCTV cameras
  • Computer Networking
  • Internet
  • Defence and Space-Related Applications
  • Automobile Industries
  • Television Cables