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Principle of optical fibre communication

Optical Fibre Communication: Optical fibre communication is a method of communication in which an optical wave passes through optical fibre by the total internal reflection principle. This optical signal consists of the electrical signal (Also known as information) and the laser beam i.e. a carrier wave. The optical fibre is used as a waveguide or transmission medium in optical fibre communication. Principle of optical fibre communication: In the optical fibre communication principle, the information (such as voice) is first converted into an electrical signal. Then it is modulated onto the laser beam (Also known as a carrier wave). In the modulation process, The electrical signal is superimposed onto the laser beam and the frequency of laser light changes with the frequency of the electrical signal. The optical fibre communication uses the pulse code modulation (PCM) for transmitting the optical signal. Now modulated optical signal passes through the optical fibre or waveguide

Comparison of Step Index and Graded Index Fibres

Comparison of Step Index Fibres and Graded Index Fibres(GRIN)→ S.No. Step Index Fibre Graded Index Fibre 1. In a step-index fibre, the refractive index of the core a constant value. In graded-index fibre, the refractive index in the core decreases continuously in a nearly parabolic manner from a maximum value at the centre of the core to a constant value at the core-cladding interface. 2. For a step-index fibre, the variation of refractive index is mathematically expressed as, $\begin{cases} & \mu(r)=\mu_{1} \qquad 0 < r < a \quad for (core)\\ & \mu(r)=\mu_{2} \qquad r >a \quad for(Cladding)\\ \end{cases} \\ Where \: \mu_{1} > \mu{2} $ Parabolic refractive index variation in GRIN fibre is mathematically expressed as, $ \begin{cases} & \mu^{2}(r)=\mu^{2}_{1} \left[ 1- \left(\frac{r}{\alpha} \right)^{2} \

Comparison of Single Mode and Multimode Index Fibres

Comparison of Single-Mode Index Fibres and Multimode Index Fibres→ S.No. Single Mode Index Fibre Multimode Index Fibre 1. In single mode index fibre, the diameter of the core is very small and is of the same order as the wavelength of light to be propagated. It is in the range $5\mu m - 10 \mu m$. The Cladding diameter is about $125 \mu m$. In multimode index fibre, the diameter of the core is large. It is in the range $30\mu m - 100 \mu m$. The Cladding diameter is in the range $125 \mu m - 500 \mu m$. 2. The difference in refractive indices of the core and cladding material is very small. The difference in the refractive indices of the core and the cladding materials is large. 3. In single-mode fibre, only a single mode is propagated. In multi-mode fibre, a large number of modes can be propagated. 4. Single mod fibre does require a much more sophisticated li

Numerical Aperture and Acceptance Angle of the Optical Fibre

Angle of Acceptance → If incident angle of light on the core for which the incident angle on the core-cladding interface equals the critical angle then incident angle of light on the core is called the "Angle of Acceptance. Transmission of light when the incident angle is equal to the acceptance angle If the incident angle is greater then the acceptance angle i.e. $\theta_{i}>\theta_{0}$ then the angle of incidence on the core-cladding interface will be less than the critical angle due to which part of incident light is transmitted into cladding as shown in the figure below Transmission of light when the incident angle is greater than the acceptance angle If the incident angle is less then the acceptance angle i.e. $\theta_{i}<\theta_{0}$ then the angle of incidence on the core-cladding interface will be greater than the critical angle for which total internal reflection takes place inside the core. As shown in the figure below Transmission of light w