Explain the impact of fibre optic technology in communicationtion of sound wave
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OPTICAL COMMUNICATIONS
Optical communications systems have a long history. Ancient man signalled with smoke and fire, often relaying messages from mountain top to mountain top. However, this optical communication scheme had limited transmission capacity. They could serve as a warning, as Queen Elizabeth the First of England planned when she had a network of bonfires erected to be set in the event of a seaborne invasion from Spain. The smoke signals transmitted by native Americans had the capacity to transmit various messages. Since the end of the eighteenth century messages have been passed by semaphore – the use of flags to indicate the transmission of one letter at a time. This form of communication could transmit information at a rate of about one letter per second over a direct line of sight, although messages could be relayed over long distances. Such means of communication were not very secure: anyone in the line of sight to the message sender could read the information (if he knew the code). The message could also be intercepted and altered during the relay process as the Count of Monte Cristo did to his advantage .
Another historical use of optical communication involved the heliograph -- a device to reflect the sun's rays from a transmitting to receiving station using a code. This technique was widely used by the US Cavalry in the desert south-west of the United States until the early part of the twentieth century. For optical communication to progress past these early efforts, an information carrying channel had to be developed that was reliable, inexpensive, and that could be used over long distances, preferably at high rates of data transmission. The fundamental physical phenomenon that makes this possible is called total internal reflection. This phenomenon causes light to reflect, rather than refract, when it attempts to cross the boundary from one transparent optical medium to another of lower optical density, at a sufficiently large angle. As early as 1854, in London, John Tyndall demonstrated that light could be guided inside a transparent medium with such a density discontinuity with its surroundings. He did this by showing light being guided along a stream of water flowing from a container. His simple demonstration proves that in the right circumstances light need not travel in straight lines.