Fiber Optics: Development of Pure Glass - Coursework Example

Fiber Optics Introduction The advent of technology has generated many inventions among them easing the way information is transferred from one place to another. The ever increasing efficiency to transmit information globally has made the world to be regarded as a ‘global village’. Progress from the use of copper wires as a medium for transfer of information to the use of optic cables serves as an evidence of the great leap in technology over the centuries. Of all the earlier transmission media, an increase in the volume of information that can be sent over a large distance at higher speed is the technological development that has been made a reality by the invention of fiber optic cables. However, for the above development to be realized, painstaking research has been done due to a myriad of problems that plagued this technology. Various events were crucial among them the invention of laser and development of pure glass which overall made optic communication practical. In this paper, a detailed explanation of these developments and the principles and law of physics behind them will be analyzed. This will help to create a clear picture on the path that had to be followed for fiber optic cables to be of practical and efficient use in spearheading the digital revolution. The history of optical communication Optical communication was still in use long time ago. Fire and smoke was time and again used by the ancient man to relay messages from one mountain top to the other. In most cases it was used to warn people about invasion or natural catastrophe. However, this form of communication had minimal transmission capacity as it wholly dependent on a clear line of sight and favorable weather conditions (Mach, 46). In addition, anyone in the line of sight could get the message which advantageous to the enemies in case of an invasion. In England, Queen Elizabeth used systematically positioned bonfire to be used to warn people in case of invasion by sea from Spain. Smoke signals were also widely used by the Native Americans in messages transmission. The beginning of the 19th century saw the birth of semaphore which had a capacity of transmitting a single letter per second though dependent on a clear line of sight. Unfortunately, this form of transmission was open to sabotage by enemies in its path as was done by Count of Monte Cristo. By the end of the 19th century, communication had shifted to the use of heliograph which used the sun’s rays to transmit coded information from one station to the other (Darrigol, 150). The US Cavalry widely employed this technique in their journey through the desert till early 20th century. This early efforts to transmit information were deficient of an inexpensive and reliable channel that could guarantee speedy transmission over long distances. It was also imperative to come up with channel that was not dependent on a clear line of sight. However, this required more researches to done since from elementary physics it clear that light travels in a straight line (Mach, 25). The flurry of events that followed made this phenomenon possible by ensuring they were no refraction as laid out in the Snell’s law leading to total internal reflection (Mach, 34). This was the most important part in the invention of fiber optic cables. Physics of optic fiber To form a better understanding of the technology that is behind the development of fiber optic, it is imperative to look into the principles of physics behind it. Fiber optic systems largely operate following the basic rules governing optics including the law of reflection. It is in the properties of light that this noble invention in the communication industry was derived (Rao, 73). Figure A Optic fibers fully employ this principle of total internal reflection which is made possible by the cladding apartments that surrounds the core as shown on figure A. The cladding material which is made of plastics ensures that light remains trapped on the denser part of the core which is mainly made up of pure glass (Thavenaz, 25). On the transmitting end, the cable is fitted with a laser diode which generate light into the conduit whereas on the other end photosensitive devices are used to convert the light impulses back into electrical signals (Rao, 103). A single optic cable can be made up of hundred of optic fibers which are protected are protected by an outer covering referred to as a jacket. Fibers are mainly categorized into two, single and multi-mode. The difference between the two is in the size of the core and the wavelength of the transmitted light. Single mode fiber has a core with a diameter of about nine microns and transmits infrared light in the wavelength between 1300 and 1550 nanometers (Lecoy, 50). On the other hand, multi-mode has a core diameter of 62.5 microns and transmits light in the wavelength between 850 and 1300 nanometers (Lecoy, 30). Mathematical representation of total internal reflection Snell’s law states that; n1sinq 1=n2sinq 2 Where q 1is the angle of incidence, and q 2 is the angle of refraction. See Fig.(B) The media refractive indices are represented by quantities n1 and n2 (Mach, 214).     Figure B Incase the refractive index n1 is significantly greater than n2, total internal reflection may occur. However, its occurrence depends on if q 1 will exceed the critical angle (Mach, 218). Thus the cladding material should possess less refractive index than the core for total internal reflection to occur. Problems encountered in fiber optic cables development Attenuation This is the exponential reduction in the intensity of transmitted light as the length of the fiber increases measured in decibel (dB). Attenuation (dB)= 10 log(P1/P2), Where (P1) is the input light power while (P2) is the output light power (Rao, 84). This was a stumbling block in fiber development until 1966 when George Hockham and Charles Kao discovered that impurities in glass were responsible for the high level of attenuation. The removal of impurities such as copper, iron, vanadium, hydroxyl ions, and chromium has resulted to the significant decrease in attenuation enjoyed today in fiber transmission. Absorption Absorption of light contributes to attenuation during the transmission process. It mainly occur in three ways namely; residual infrared absorption, Rayleigh scattering and residual ultraviolet absorption. Even if the latter is minimized, the former two losses are hard to control and where Rayleigh scattering can only be managed during the production of the fiber since it is brought about by variation in glass composition (Rao, 85). Dispersion There is a tendency for optical pulses to lose shape referred to as dispersion also affects the rate of transmission In addition, over extremely long distances, attenuation still occurs prompting for the need to amplify them after a given distance. This is duly rectified by the use of repeater which detects the weakened light impulse and processes it electronically for re-transmission by its inbuilt laser. In this way, optical pulses can cover large distances without suffering from attenuation and dispersion (Rao, 86). In a situation where two impulses carry independent messages, it is very complex for a repeater to boost them separately. In this case, Erbium Doped Fiber Amplifiers (EDFAs) are used to address this short-coming. However, the EDFAs scheme only rectifies attenuation but not light impulses dispersion (Thevenaz, 182). Fortunately, this can be addressed by use of dispersion management which involves incorporation of dispersive agents between the receiver and the transmitter. Optic fiber use industries Optic fiber has transformed the communication industry overshadowing the traditional coaxial cables, microwave links and wires. This is due to its superior data-carrying capacity in comparison to its competitors which is down to the fact that they carry light. Fermat’s principle states that when light travels between points, its path is the one which occurs in the least amount of time. In addition, it is economical to produce, it is not affected by electrical and electromagnetic disturbances except from nuclear radiation, are resistant to corrosion and are small in size (Rao, 150). Their small sizes have also favored their application in the medical industry during diagnosis. In industry where electrical control is critical in setting up safety measures, optic fibers has come in hardy since harbor no potential electrical ignition risk e.g. in the petroleum industry (Rao, 160). In conclusion, fiber optic cables are currently responsible for the movement of vast amount of information all over the planet. This is due to the fact that they possess desirable properties suited for information transmission over long distances. They are economical on cost and are resistance to electrical and magnetic disturbances seen in electrical wires communication links. This high end superiority has seen optic fiber replace older technologies in the communication industry. Over the last three decades, fiber optic technology has undergone an exponential growth evident in its transformation of the internet. Although it is very hard to predict the future, it is highly likely that most of the technological invention will be centered on fiber optic. Works Cited Darrigol, Olivier. A History of Optics: From Greek Antiquity to the Nineteenth Century. Oxford: Oxford University Press, 2012. Print. Lecoy, Pierre. Fiber-optic Communications. London: ISTE, 2008. Print. Mach, Ernst. Principles of Physical Optics: An Historical and Philosophical Treatment. Dover Publications, 2013. Internet resource. Rao, M M. Optical Communication. Hyderabad, India: Universities Press, 2000. Print. Thévenaz, Luc. Advanced Fiber Optics: Concepts and Technology. Lausanne, Switzerland: EFPL Press, 2011. Print. Read More