Multimode Dispersion in Optical Fibre Calculator

This tutorial introduces the concept of multimode dispersion in optical fibres, a key principle in the field of fibre optics, a sub-discipline of physics. Optical fibres transmit information in the form of light pulses, and dispersion refers to the broadening of these pulses as they travel along the fibre. In multimode fibres, different light rays, or modes, travel along different paths and thus arrive at different times, causing pulse broadening or dispersion.

Multimode Dispersion in Optical Fibre Calculator
Multimode Dispersion in Optical Fibre Calculator Results
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Example Formula

One of the most important formulas related to multimode dispersion is for calculating the modal dispersion of a step-index fibre. The modal dispersion (Δτ), expressed in nanoseconds per kilometre (ns/km), is given by:

Δτ = (L × n12 × Δ) / (c)


  1. Δτ: Modal dispersion
  2. L: Length of the fibre
  3. n1: Fibre refractive index
  4. Δ: Relative refractive index difference, given by (n1 - n2) / n1, where n2 is the cladding refractive index
  5. c: Speed of light in a vacuum

Who wrote/refined the formula

The formula was derived from the principles of light propagation in optical fibres, which have been studied and refined by countless scientists and engineers in the field of fibre optics. The refractive index difference and the effects it has on the propagation time of different modes form the basis for this formula.

Real Life Application

Multimode dispersion is an important factor in the design and operation of fibre optic communication systems. Engineers must account for this when designing systems to ensure data is transmitted accurately and efficiently over long distances. For instance, to reduce multimode dispersion, graded-index fibres are often used in local area networks (LANs).

Key individuals in the discipline

Charles Kao, who received the Nobel Prize in Physics in 2009, is one of the key figures in the field of fibre optics. His work in the late 1960s paved the way for fibre optic communications by demonstrating the feasibility of transmitting light over long distances through optical fibres.

Interesting Facts

  1. Fibre optic cables have revolutionized global communications, enabling high-speed internet connections and telecommunications across continents.
  2. Multimode optical fibres are used in a variety of applications, from telecommunications to medical imaging to industrial sensing.
  3. Understanding and managing multimode dispersion has been key to continually improving the capacity and reliability of fibre optic communications.


Multimode dispersion in optical fibres is a crucial concept in fibre optics and has a significant impact on the performance of fibre optic communication systems. Understanding this phenomenon allows us to better design and optimize these systems, leading to faster and more reliable data transmission. It's another great example of how understanding the principles of physics can lead to transformative technological advancements.

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