Question

Please help..

Give a few uses of the optical fibre and if you have any idea how it works you can explain it in your own words

Answer 1

One of the main uses of optical fibers is in telecommunications (telephone or internet transmissions). At one end of the fiber an electrical or electronic signal is converted into a light pulse, which can be transmitted along the inside of the extremely thin fiber.

There are certain conditions which have to be satisfied for this to occur. The fiber is usually made of glass or plastic. This will have a higher refractive index than the air that surrounds it.



We know that when a light ray strikes a boundary travelling from a medium of higher refractive index to one of lower refractive index, then it its refracted outward through into the next medium, away from the normal line perpendicular to the boundary. The larger the angle of incidence, the greater the refraction which could be observed. Eventually, if the light ray is incident at a large enough angle with respect to this normal line, then the refracted ray will run along the boundary between the fiber and the air. This particular angle of incidence is known as the CRITICAL ANGLE.

In an optical fiber, we aim to make sure that the angle of incidence is larger than the critical angle, as when this occurs the ray does not enter the other medium at all. Instead, it is now reflected (as if we were shining the beam off a mirror, for example) in a process known as TOTAL INTERNAL REFLECTION. So, the light beam is reflected back within the fiber and now travels towards the opposite boundary, where a similar process can occur. This allows the light pulse to travel along the entire fiber until it reaches the end, where it is detected and reconverted into the original signal/message. The optical fiber also allows multiple light pulses to travel along its length at any given time, so along as we always make sure that

ANGLE OF INCIDENCE > CRITICAL ANGLE

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Another use of optical fibers is in medicine. They let doctors view and work inside the body, requiring only small incisions to enter the body and no surgery. Endoscopes, for example, use optical fibers to inspect the insides of hollow organs in the body, with images being transmitted along the fiber using the same principles as in telecommunications.