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Engineering Physics

Types of Optical Fibers: Step Index & Graded Index

There are two types of OPTICAL FIBERS depending on the refractive index of core and cladding are available; a. Step Index Optical Fiber b. Graded Index Optical Fiber In step index optical fiber the core and cladding has a uniform refractive index. In the step index optical fibers the rays entering at different angles travel different paths and emerge out at the end of the optical fiber at different times.

This time lag between the signals is known as the dispersion. On the other hand in the Graded-Index Optical Fibers, the core has a non-uniform refractive index, it is maximum at the central axis of the optical fiber and gradually decreases up to the core-cladding interface. But the cladding has a uniform refractive index. As you know that the refractive index n=c/v; where c is the speed of light in free space and v in any medium.

So if n is changing obviously v will change. Here in the Graded-Index Optical Fiber, the refractive index of the core is changing and it is maximum near to the central axis so the light ray which enters through this will have lower speed as compared to the light signal which enters near to the co cladding interface because here the refractive index is lower.

So the speed of light will be faster. In this case, we found that there is no time lag between the signals, all the signals reach at the same time. The characteristics of the optical fiber are determined generally by the following parameters,

these are;

  1. The composition of the material; it indicates the value of the refractive index of the core
  2. The nature of light; it means the wavelength of the optical signal and
  3. The diameter of the core and length of the optical fiber.

In case of step index (single mode and multimode), graded index optical fiber (multimode) the diameter of the core and cladding is discussed along with the Band Width, Numerical Aperture, Attenuation, and Applications of the Optical fibers.

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  1. Tapas Sharma

    Nice informative video,Helps students to score good marks in engineering Physics

    1. Dr Sushil Kumar

      Thank you Tapas for your time and kind feedback.

  2. Dipin Gandhi

    A very instructive way of learning physics practically through experiments.

    1. Dr Sushil Kumar

      Thank you Dipin Gandhi, hope you are doing great at your end. Best wishes always.

  3. Shivang0308

    Great initiative

    1. Dr Sushil Kumar

      Thank you Shivang.
      best wishes always.

  4. Aashima Malhotra

    Excellent and very informative 👍

    1. Dr Sushil Kumar

      Thank you Ashima madam for your kind words.

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