Why optical fibres are used?

∆∆Optical fibre links are being increasingly used for both short-distance communications, such as for local area networks (LANs), and long-distance communications. This arises from the fundamental advantages of optical f ibre communications:

• They are low cost.

• They are robust when packaged.

• They can have very wide optical bandwidths (GHz) and long communication links (hundreds of kilometres).

• They are insensitive to electromagnetic interference.

∆∆This has led to the wide range of intercontinental communication links which are several thousand kilometres long, which distance considerably exceeds the maximum length of optical fibre that can be manufactured. It also exceeds the maximum link length over which an optical signal can be propagated without periodic amplification or regeneration. The environment is also somewhat harsh and remote, requiring high reliability and robust packaging.

∆∆The highest frequency was of the order of 1000 GHz. If the frequency is increased to about 1015 Hz, we would find that the signal would literally appear as visible light. Signals in the range 1012–1015 Hz appear as infra-red light, whereas those in the range 1015–1017 Hz appear as ultraviolet light. This raises the question, if we can transmit data using the lower frequency ranges, why should we not communicate at the higher light frequencies? In fact, there is no reason why we should not, but there are difficulties in taking the light from a source to some form of receiving unit within which the carrier could be separated from the basic information signal. There are plenty of materials, such as glass, through which we can pass light. A glass fibre would make a simple conductor of light. The problem is to retain the light within the glass, but it is possible by simple conductor of light. The problem is to retain the light within the glass, but it is possible by simply placing the f ibre within a cladding.

Comments

HOW CAN WE MOTIVATE OURSELVES MORE EFFECTIVELY THROUGH REINFORCEMENT?

•We'd all like to be more effective in reaching our goals, and according to behaviorists, the way to improve our effectiveness is by rewarding ourselves for the little steps that take us closer and closer to those desirable outcomes. •First, find something you really like to do or something you'd like to have that can, realistically, serve as a reward. •Then, take the goal that you are hoping to achieve that, realistically, you could achieve but just haven't succeeded at yet. •Next, work backward from that goal to your present state. •Arrange to give yourself those desired rewards as you inch closer from where you are now to the desired end point. •As you start to make progress, only give yourself a reward when you've moved forward from where you are now. •For example, if you'd like to cut back on your television watching and instead read more often, reward yourself by allowing yourself to watch television only when you've read for 20 minutes,

15 Did You Know Fact that will surprise you

1) Did you know that this colourful little chap is the Costa Rican Variable Harlequin toad aka the Clown frog. 2) Did you know that the Karni Mata Hindu Temple in Rajasthan, India, is also known as the Temple of Rats. The temple is famous for the approximately 25,000 revered black rats that live there. Visitors play with and feed the rats and even sometimes drink from the same milk and eat the same food. 3) Did you know that vanilla flavoring is sometimes made with the urine of beavers. 4) Did you know that Botox is made from botulinium toxin which is considered the most deadly substance in the World as half a pound would be enough to wipe out the entire World population. Almost all the Botox in use throughout the World is made in one single factory in Ireland. 5) Did you know that tuna swim at a continuous steady rate of about 14km per hour for their whole life until they die. Whilst alive they never stop moving as if they stop they are unab

WHY DO WE SLEEP AND DREAM?

•We spend about one-third of our lives sleeping. •Why do we invest so much time in sleep? •The most straight forward answer is that, sleep is restorative, and it replenishes the body's energy stores. •However, intense neural activity during rapid eye movement (REM) sleep, the stage in which most dreams occur, suggests there may be more to the story. •One theory, which by far has the largest body of evidence, is that sleep plays a critical role in learning and consolidating memories. •It is probably why infants and toddlers need up to 14 hours of sleep a day, with half of it spent in REM sleep. •In adults, dreams may also play a role in brain plasticity and learning, which is why sleep-deprived adults perform worse in memory tests and tasks.

Knowledge N Fact4u

Search This Blog