Fibre optics is being used to transmit television, voice, and digital data signals by light waves over flexible hair like threads of glass and plastic. It has evolved into a system of great importance and use since the 1980’s.
The advantages of fibre optics compared to coaxial cable or twisted pair cable, are endless. Millions of dollars are being spent to put light wave communication systems into operation, as a result of its performance.
Light is ejected into the glass core at the correct angle and transmitted; it will reflect back repeatedly with internal reflections, even when the rod is curved. Light cannot escape from a fibre optics cable. A bundle of rods of fibres is capable of taking an image projected at one end of the bundle and reproducing it at the other end.
This cable has a specific index of refraction for the core and the cladding. It causes deformations due to the various paths lengths of the light ray. This is called modal distortion. It is the cheapest type of cabling. Within the cladding and the core, the refractive index is constant.
Graded Index Fibre
In graded index fibre, rays of light follow sinusoidal paths. Although the paths are different lengths, they all reach the end of the fibre at the same time. Multimode dispersion is eliminated and pulse spreading is reduced. Graded Index fibre can hold the same amount of energy as multimode fibre. The disadvantage is that this takes place at only one wavelength.
Optical fibres that carry data consist of pulses of light energy following each other. The fibre has a limit as to how many pulses per second can be sent to it and be expected to emerge intact at the other end. This is known as pulse spreading which limits the Bandwidth of the fibre.
The pulse sets off down the fibre with a square wave shape. As it travels along the fibre, it progressively gets wider and the peak intensity decreases.
The transmission loss or attenuation of an optical fibre is perhaps the most important characteristic of the fibre; this determines if a system is practical. It controls (1) spacing between repeaters and (2) the type of optical transmitter and receiver to be used.
As light waves travel down an optical fibre, they lose part of their energy because of various imperfections in the fibre. These losses are measured in decibels per kilometers (dB/km).
Stated fibre optics is a revolution that may affect our lives as much as computers and integrated circuits have. Fibre optics is being compared in importance with microwave and satellite transmissions in the advanced world of communications.
Ali, Zafar, Configuration Supervisor, Unisys Canada Inc.
stated that fibre optics will make using devices that use services such as two-way television that was too costly before the development of fibre optics easier to use with better quality. In addition to an incredible bandwidth, fibre optics has smaller and lighter cables than conventional copper-conductor systems, with immunity to electrical noise, and numerous other advantages.
The age of optical communications is a new era. In several ways fibre optics is a pivotal breakthrough from the electric communication we have been accustomed to. Instead of electrons moving back and forth over a regular copper or metallic wire to carry signals, light waves navigate tiny fibres of glass or plastic to accomplish the same purpose.
With a bandwidth and information capacity a thousand times greater than that of copper circuits, fibre optics may soon provide us with all the communication technology we could want in a lifetime, at a cost efficient price.
Any new communication system that does not use fibre optics, or consider its use, is obsolete even before it has been built. It is apparent that the average technician may also become superseded if he or she fails to master fibre optics. After all, the technician will be responsible for repairing and maintaining fibre optic systems wherever they are used, not the engineer.