The Theory of Light Relevant to Fiber Optics - Essay Example

?Fiber Optics Introduction People hear about fiber optic cables all the time in the present world especially when dealing with internet, cable system, or television set related issues but not everyone knows exactly a great deal about their history, construction, application, types, and integration in the aviation industry. Basically, fiber optics refer to the cables or lines which contain optically pure glass used to transmit digital information signals. The bedrock of these cables is formed by this optically pure glass which is more or less as thin as a human hair but has astounding ability to carry digital information over far across corners of the world. This essay aims at scrutinizing what authentic technical literature has to say on the issue of integrating fiber optics in the aircraft systems in addition to contemplating the theory of light in relation to optical fibers as a way of illuminating exactly how the idea to transmit light through a thin fiber made of glass or plastic originated. The application of optical fibers in fiber-optic communication will also be discussed to evaluate how they allow transmission over longer distances at higher speeds as compared to other communication media. Theory of light relevant to fiber optics While ray theory best explains the light transmission and guiding properties of optical fibers, mode theory works to explain the behavior of light within a fiber. Ray theory basically serves to describe the direction taken by a plane wave inside a fiber (Einstein College of Engineering n.d.). According to ray theory, there are two types of rays which are carried by an optical fiber namely meridional and skew rays both of which stand in contrast to each other in context of the course they take inside a fiber. While meridional rays pass through the axis of a fiber, the skew rays journey through a fiber without passing through its central axis. Also literature suggests that “the acceptance angle for skew rays is larger than the acceptance angle of meridional rays” (Einstein College of Engineering n.d). The light capacity of a fiber is enhanced when skew rays are added to meridional rays. But it is argued that as “skew rays tend to propagate near the edge of the fiber core” (Einstein College of Engineering n.d.), so the addition results in entrapment of a large number of skew rays in the fiber core made of thin glass. “A large portion of the number of skew rays that are trapped in the fiber core are considered to be leaky rays” (Einstein College of Engineering, n.d.). Construction of fiber optic cables Fiber optic cables basically consist of three parts namely the core, the cladding, and the coating which are also referred to as the triple C’s. Though light has been shown to propagate along the fiber core even without the aid of cladding, it is suggested that cladding made of plastic or glass has its share of important functions like improving mechanical strength, reducing the loss of light into the surrounding during transmission course and protecting the fiber against many surface contaminants to smooth the process of transmission. Buffer or the coating forms the outermost layer which serves to lend extra durability and strength to an optical fiber as a way of protecting it against physical harm (Freudenrich, 2012). It is important to remember that the core is essentially made of glass, the cladding layer is made up of either plastic or glass, and plastic is used as a preferred material for the buffer.   Basic fiber optic theory  As mentioned earlier, mode theory along with ray theory is used to explain the propagation and behavior of light in an optical fiber. Mode theory also largely serves to explain the issue of leaky ray loss caused by the addition of skew rays to a fiber’s core. It also suggests that a light wave can be referred to as a plan wave or a wavefront when travelling through an optical fiber and such wave is described by “its direction, amplitude, and wavelength of propagation” (Einstein College of Engineering n.d). It is further claimed that though plane waves are similar to light waves in context of their propagation along a fiber, not all wavefronts confronting the fiber core “at angles less than or equal to the critical angle of light acceptance propagate along the fiber” (Einstein College of Engineering n.d). The dispersion of an optical fiber is also explained by the mode theory which refers to “the change in the propagation constant for different waves” (Einstein College of Engineering n.d.). Types of fiber optic cable  Optical fiber cables are available in the market in two main types namely single-mode and multi-mode fibers. Major difference between these two types is that while the single-mode fibers use small cores and carry laser light, multi-mode optical fibers use larger cores and transmit infrared light light-emitting diodes or LEDs (Freudenrich, 2012). Literature about history of fiber optics suggests that as early fiber-optic communication systems were largely limited by multi-mode fibers, the single-mode fibers using smaller cores were introduced in 1981 to highly enhance the system performance. In addition to that, some optical fibers are made up of plastic also and such fibers typically have large cores of 1mm dm. Plastic optical fibers “transmit visible red light (wavelength = 650 nm) from LEDs” (Freudenrich, 2012). Sources and detectors used in fiber optic communication Literature suggests that depending on the “situation and requirements either LED or LASER can be utilized as an optical source” (Pal, 2005) for optical fiber communication systems. A multi-mode step index optical fiber in contrast to a single-model fiber has a core diameter of 50µm and is used to transmit communication for shorter distances. Such fibers not only depend on low tolerance requirements on the fiber connecting ends but also make use of “spatially incoherent optical sources” (Pal, 2005). Semiconductor Lasers or LEDs are commonly used as sources in optical fiber communication systems for producing “modulated light wave carrier” (Pal, 2005). When the information signals reach the receiving end, the optical detectors produce an output signal and the commonly used optical detectors include “photodiodes (p-i-n, avalanche), phototransistors, photoconductors” (Pal, 2005). Attenuation in fiber optics systems It is suggested that early fiber optic systems displayed remarkably high attenuation up to the level of 1000dB/km and this stood nowhere close to the attenuation of coaxial cables which exhibited attenuation of only 5-10dB/km. But within ten years, this high attenuation of optical fibers plummeted down to level of 5dB/km which considerably helped in reducing optical fiber losses (Pal, 2005). With the continuous and rigorous development of optical fibers, other optical components like optical sources and detectors in addition to attenuation also underwent research process. As a result, such semiconductor optical sources and detectors got invented which enabled a remarkable shift in transmission wavelength due to which transmission distance became able to be increased. It is suggested that fiber optic systems operating at “1550nm provided lowest attenuation and these links routinely carry traffic at around 2.5Gb/s over 90 km repeaterless distance” (Pal, 2005). Advantage of Fiber Optics compared to copper wire Optical fiber cables are capable of transferring and guiding information in the form of video, voice, or data across phenomenally large distances. This is an achievement made possible by a giant shift in transmission length as already mentioned and which copper cables fail to manage by long shots. Also, the main part of an optical fiber is the core which has an extremely small diameter and the fiber itself is taken care to be kept very light weight which makes it easier to address a wide variety of cabling issues. Also, cables may often come in close vicinity of electronic devices but the advantage of optical fibers is that they are immune to radio frequency and electromagnetic interference which eliminates the risk of RFI and EMI disruption (Timbercon, Inc., 2012).   Use of fiber optics in the aircraft systems An optical fiber is really one amazing product of technology which introduced new horizons and made myriad unreachable targets absolutely reachable. The use of optical fiber cables in aerospace avionic systems is increasing with time. IGIC market research suggests the total fiber optic market for military and aviation industries grew from $306 million in 2009 to $775 million in 2015 (IGIC, 2012). This growth in total market reflects myriad factors like greater acceptance of new technology, vigorous developments in the telecommunication area, the need to control weight and size, the need to have faster transmission rates, and many other reasons all related to the merits offered by fiber optics. Optical fibers are small in size and weight so they are now considered ideal for the aircraft systems and they also ensure higher bandwidth. Also, single-mode fibers greatly improve the system’s performance. Conclusion Concluding, the above discussion shows that the transmission of light signals through an optical fiber can be described by two theories. One is the ray theory which describes light as a simple ray and other is the mode theory or wave representation approach which in contrast refers to light as an electromagnetic wave. Also, core is the inside most part of an optical fiber through which light is transmitted. Electromagnetic wave behavior forms the foundation of the mode theory which suggests that the modes of the optical fibers are made up of sets of guided electromagnetic waves. The core diameter of multi-mode fibers is wider in contrast to that of single-mode fibers and these fibers are used for communication transmission across smaller distances. Detectors in the fiber after receiving information from the source work to transmit it to the intended destination. Copper cables in contrast to optical fibers are heavier and less facilitative. References Einstein College of Engineering n.d., INTRODUCTION TO OPTICAL FIBERS, viewed, 08 December, 2012, Freudenrich, C 2012, How Fiber Optics Work, viewed, 08 December, howstuffworks, viewed, 08 December, 012, IGIC 2012, Vol. 1 - Market for Fiber Optics in Military & Aerospace Avionic Systems, Military & Aerospace Fiber Optics Market Report Series, viewed, 08 December, 2012, Pal, P 2005, OPTICAL FIBER COMMUNICATION SYSTEM – THEORY & ANALYSIS, viewed, 08 December, 2012, Timbercon, Inc. 2012, Copper Cable vs Fiber Optics, viewed, 08 December, 2012, Read More