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Optical fibre


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Optical fibre

  1. 1.
  2. 2. Muhammad Awais Ali UW-11-EE-BSc-12 Sikandar sittar UW-11-EE-BSc-76 Faraz Hussain UW-11-EE-BSc-64 Ali Raza UW-11-EE-BSc-08 Saac Aurangzab UW-10-EE-BSc-50 Group Members
  3. 3. Topic Optical Fiber Communication
  4. 4. Introduction <ul><li>Transmission Media </li></ul>
  5. 5. Introduction <ul><li>Communications systems that carry information through a guided fiber cable are called fiber optic systems . </li></ul><ul><li>Use of optical fibers to replace conventional transmission lines and microwave wave-guide in telecommunication systems. </li></ul><ul><li>Light is effectively the same as RF radiation but at a much higher frequency , theoretically the information-carrying capacity of a fiber is much greater than that of microwave radio systems. </li></ul>
  6. 6. <ul><li>As they are not electrically conductive , hence very suitable for use in areas where electrical isolation and interference are severe problems. </li></ul><ul><li>An attenuation of less than 2dB/Km . </li></ul>
  7. 7. Advantages of Optical Communications 1) Extremely wide system bandwidth - up to 10 GHz is possible 2) Immunity to EMI - such as lightning, electric motors, fluorescent lights 3) Virtual elimination of cross-talk 4) Lower signal attenuation than other propagation systems
  8. 8. Advantages of Optical Communications 5) Lighter weight and smaller size 6) Lower cost 7) Conversion of the earth’s resources - principal ingredient in glass is sand which is cheap and virtually unlimited supply 8) Safety - no hazard of short circuits nor spark will exist in optical fiber
  9. 9. Fundamentals of Fiber Optic Systems <ul><li>Optical fibers guide light waves within the fiber material because light rays bend or change direction when they pass from one medium to another . This phenomenon is called reflaction . </li></ul><ul><li>Optical fiber is a thin, transparent strand of material, usually glass or plastic or a combination of the two, that is used to carry light beams. </li></ul>
  10. 10. Reflection in Optical Fiber <ul><li>The light rays are reflected from the inner walls as they propagate lengthwise along the fiber. </li></ul><ul><li>A single light beam can be modulated simultaneously by hundreds, or even thousands, of independent signals. </li></ul>
  11. 11. Refraction of Light <ul><li>Light travels at approximately 3x10 8 m/s in free space and slower in a material denser than free space . This reduction in speed as it passes from free space into a denser material results in refraction of the light . </li></ul><ul><li>Sshows the light is bent at the interface. The degree to which the ray is bent depends on the index of refraction n of the denser material . </li></ul>
  12. 12. Physics of Light <ul><li>The normal is an imaginary line perpendicular to the interface of the 2 materials. </li></ul><ul><li>The angle of incidence is the angle of incident ray to the normal. </li></ul><ul><li>The angle of refraction is the angle of refracted ray to the normal. </li></ul><ul><li>The critical angle is the angle of incidence that will produce a 90 0 angle of refraction . </li></ul>
  13. 13. <ul><li>3 specific conditions are shown in Fig. The angle of incidence, A 1 and the angle of refraction, A 2 . </li></ul><ul><li>Material 1 is more dense than material 2, so n 1 is greater than n 2 . </li></ul>
  14. 14. <ul><li>Fig. 3A shows how a light ray passing from material 1 to material 2 is refracted in material 2 when A 1 is less than the critical angle. </li></ul><ul><li>Fig. 3B shows the condition that exists when A 1 is at the critical angle and angle A 2 is at 90 0 . The light is directed along the boundary between the 2 materials. </li></ul><ul><li>Fig. 3C shows that any light ray incident at an angle greater than A 1 of Fig. 3B will be reflected back into material 1 with A 2 equal to A 1 . </li></ul>
  15. 15. <ul><li>Applications include </li></ul><ul><ul><li>Telephones </li></ul></ul><ul><ul><li>Internet </li></ul></ul><ul><ul><li>LANs - local area networks </li></ul></ul><ul><ul><li>CATV - for video, voice and Internet connections </li></ul></ul><ul><ul><li>Utilities - management of power grid </li></ul></ul><ul><ul><li>Security - closed-circuit TV and intrusion sensors </li></ul></ul><ul><ul><li>Military - everywhere! </li></ul></ul>Fiber Optic Communications
  16. 16. Why Use Fiber Optics? <ul><li>Economics </li></ul><ul><li>Speed </li></ul><ul><li>Distance </li></ul><ul><li>Weight/size </li></ul><ul><li>Freedom from interference </li></ul><ul><li>Electrical isolation </li></ul><ul><li>Security </li></ul>
  17. 17. Total Internal Reflection of Light <ul><li>Total internal reflection in optical fibers </li></ul><ul><li>Total internal reflection forms the basis for light propagation in optical fibers. </li></ul>
  18. 18. Fiber construction
  19. 19. Fiber Optic Applications <ul><li>Fiber is already used in: </li></ul><ul><ul><li>> 90% of all long distance telephony </li></ul></ul><ul><ul><li>> 50% of all local telephony </li></ul></ul><ul><ul><li>Most CATV networks </li></ul></ul><ul><ul><li>Most LAN (computer network) backbones </li></ul></ul><ul><ul><li>Many video surveillance links </li></ul></ul>
  20. 20. Fiber Optic Applications <ul><li>Fiber is the least expensive, most reliable method for high speed and/or long distance communications </li></ul><ul><li>While we already transmit signals at Gigabits per second speeds, we have only started to utilize the potential bandwidth of fiber </li></ul>
  21. 21. Light Used In Fiber Optics <ul><li>Fiber optic systems transmit using infrared light, invisible to the human eye, because it goes further in the optical fiber at those wavelengths. </li></ul>
  22. 22. Propagation modes
  23. 23. Mode of Propagation <ul><li>Mode simply means path from which light is propagated. </li></ul><ul><li>If there is only one path for light to take down the cable, it is called single mode . </li></ul><ul><li>If there is more than one path , it is called multi-mode . </li></ul>
  24. 24. Modes
  25. 25. Fiber types
  26. 26. LOSSES OF POWER 1.Power Loss By Scattering And Absorption. 2.Power Loss Due To The Dispertion Or Scattering
  27. 27. Any Question ??????
  28. 28. <ul><li>Thanks </li></ul>