Fibre Optics

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Fibre Optics

Technology over the past century has advanced greatly. Fibre optics however is being utilized since more than a hundred years. Optical fibre is a model that has evolved greatly over time. From guided transmission lights experiments to lasers and light emitting diodes (LED), and to dense wavelength-division multiplexing (DWDM), the area under which optical fibre can be used has expanded. One of the modern and commonly used applications of fibre optics is high resolution visuals (HDTV) which has enabled us to view broadcasts at 1080p screen resolution which is a result of FTTc and FTTh (fibre to the curb) network. Satellites making use of fibre optics do not have to undergo lessening (fibreopticsinfo). There are generally six theories of light from which the theory of optical fibre has evolved. The relevant theories to optical fibre are emission theory, corpuscular theory, wav theory, electromagnetic theory and quantum theory. Reflection and refraction of light are vital elements in optical fibre. These two properties have been explained by Newton in his laws. Another very important property relative to fibre optics is the critical angle of light. Critical angle is defined as the minimum angle which can allow total internal reflection to take place. This is governed by Snell’s law. There are two theories which explain the propagation of light through optical fibres. The first theory is the ‘Ray Theory’ under which light is considered to be a simple ray of light and the propagation properties are relevant to that. This theory explains the accepting and guiding behavior of light inside a fibre (Sathish Kumar). The second theory is the ‘Mode Theory’ or the ‘Wave Representation’ approach. According to the Mode Theory, light is an electromagnetic wave and acts like an electromagnetic wave inside a fibre. This theory explains the phenomenon of absorption and dispersion of light inside a fibre as well as its attenuation (The Theory of Optical Fibres). Fibre optic cables are the source of transmission of light using the fibre optics technology. Fibre optic cables enable light to be transmitted along them from one point to another and there is no significant loss in the intensity of light which passes through fibre optical cables. The construction of a fibre optic cable has three main parts: A central core, cladding and a Plastic Jacket surrounding both the core is present at the centre of the cable which acts as a buffer. It is composed of fine quality thin transparent glass polymer or a dielectric. The refractive index of the core is μ1 and the diameter of the central core ranges from 10 μ to 100 μ. surrounding the central core is a jacket layer of plastic or glass called Cladding. The refractive index (μ2) of the cladding has to be smaller than that of the central core so that the light stays inside the core due to total internal reflection (μ1 > μ2). Safety and strength are provided to cable by surrounding the cladding and the central core with a plastic jacket or the buffer (Loremate). The transmission of light by fibre optics has the same basic components as the normal wiring transmitting devices. The system comprises of a transmitter, a medium through which the signals are propagated and a receiver. The propagating medium is a cable in case of fibre optics. The transmitter has an ability to emit light with the help of either a light emitting diode or a laser. The user inputs data into the transmitter in the form of audio, video or other data. The encoder or modulator used in the transmitter to convert electrical signals to optical signals is AM, FM or digital. The user inputs data which gets modulated and then transmitted through the fibre optic cable to the receiver where it converts from optical back to electrical and gives output in the...
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