Optical Fiber Sources And Detectors

2. PRESENTATION <ul><li>TOPIC: FIBER OPTICS </li></ul><ul><li>CONTEMPORARY STUDENT. </li></ul><ul><li>NAME:…
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  • 2. PRESENTATION <ul><li>TOPIC: FIBER OPTICS </li></ul><ul><li>CONTEMPORARY STUDENT. </li></ul><ul><li>NAME: AZIZ ZOAIB </li></ul><ul><li>ID: FA06-BS-0013 </li></ul><ul><li>COURSE: TELECOM INFRASTRUCTURE </li></ul>
  • 3. TOPICS IN PRESENTATION <ul><li>History </li></ul><ul><li>Intro about Optical fiber. </li></ul><ul><li>Advantages and Disadvantages of Optical fiber. </li></ul><ul><li>Optical fiber link. </li></ul><ul><li>Types of Fiber. </li></ul><ul><li>Losses in Optical fiber cables. </li></ul><ul><li>Light sources and light detectors. </li></ul><ul><li>Amplification. </li></ul>
  • 4. HISTORY <ul><li>Optical communication: </li></ul><ul><li>Transfer of information from source to destination in the form of light signals. </li></ul><ul><li>1968 NIPPON co. developed graded index fiber with lot of impurities. (about 100 dB/km) </li></ul><ul><li>1970 CORNING GLASS WORKS (USA) fabricated single mode fiber with losses less than 20 dB/km </li></ul>
  • 5. CONTD. <ul><li>1977 BELL LAB based fiber optic in PCM format at 44.7 mbps for VOICE, VIDEO & DATA. </li></ul><ul><li>1978 instead of lab trials field trials were done. </li></ul><ul><li>1982 40000 km of optical fiber were in operation </li></ul><ul><li>A MERGER OF: </li></ul><ul><li>Semiconductor technology. </li></ul><ul><li>Optical fiber (medium). </li></ul>
  • 7. OPTICAL FIBER <ul><li>The thin glass center of the fiber where the light travels is called the “core”. </li></ul><ul><li>The outer optical material surrounding the core that reflects the light back into the core is called the “cladding”. </li></ul><ul><li>In order to protect the optical surface from moisture and damage, it is coated with a layer of buffer coating. </li></ul>
  • 8. OPTICAL FIBER <ul><li>ADVANTAGES: </li></ul><ul><li>Much wider bandwidth of 10 GHz </li></ul><ul><li>Fiber optic cables weigh less than a copper wire cable </li></ul><ul><li>Data can be transmitted digitally. </li></ul><ul><li>Lower-power transmitters can be used instead of the high-voltage electrical transmitters used for copper wires. </li></ul><ul><li>Unlike electrical signals in copper wires, light signals from one fiber do not interfere with those of other fibers in the same cable. </li></ul><ul><li>Impossible to tap into a fiber optics cable, making it more secure </li></ul>
  • 9. OPTICAL FIBER <ul><li>DISADVANTAGES: </li></ul><ul><li>Higher initial cost in installation. </li></ul><ul><li>They are more fragile than coaxial cable. </li></ul><ul><li>More expensive to repair and maintain. </li></ul>
  • 11. FIBER USED <ul><li>Glass core with plastic cladding PCS (Plastic-clad silicon) </li></ul><ul><li>Glass core and glass cladding SCS (Silica-clad silica) </li></ul><ul><li>Under research (non silicate zinc-chloride) </li></ul>
  • 12. OPTICAL FIBER <ul><li>Losses in Optical Fiber Cables: </li></ul><ul><li>Absorption due impurities in the fiber material </li></ul><ul><li>Rayleigh scattering due microscopic irregularities in the Fiber </li></ul><ul><li>Radiation losses caused by kinks and bends Of fiber </li></ul><ul><li>Coupling losses due to misalignment and imperfect surface finish </li></ul>
  • 13. ABSORPTION LOSSES IN OPTICAL FIBER Loss (dB/km) 1 0 0.7 0.8 Wavelength (  m) 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 2 3 4 5 6 Peaks caused by OH - ions Infrared absorption Rayleigh scattering & ultraviolet absorption
  • 14. LIGHT SOURCES <ul><li>LED (Light emitting diode): </li></ul><ul><li>Made from material such as AIGaAs and GaAsP </li></ul><ul><li>Light is emitted when holes and electrons recombine </li></ul><ul><li>ILD (Injection Laser diode): </li></ul><ul><li>Similar in construction as LED but ends are highly polished to reflect photons back and fourth </li></ul>
  • 15. LIGHT EMITTING DIODE <ul><li>Basic LED operation: </li></ul><ul><li>The normally empty conduction band of semiconductors populated by electron injected into it by the forward current through the junction, and the light is generated with electrons recombine with holes. This the mechanism by which light is emitted from LED. </li></ul>
  • 16. LIGHT EMITTING DIODE <ul><li>For fiber-optics, the LED should have a high radiance (light intensity), fast response time and a high quantum efficiency. </li></ul><ul><li>LED Structures: </li></ul><ul><li>Planar LED </li></ul><ul><li>Dome LED </li></ul><ul><li>Surface emitter LED </li></ul><ul><li>Edge emitter LED </li></ul>
  • 17. LASER <ul><li>Light Amplification by ‘Stimulated Emission' and </li></ul><ul><li>Radiation (L A S E R) </li></ul><ul><li>Coherent light (stimulated emission) </li></ul><ul><li>Narrow beam width (very focused beam) </li></ul><ul><li>High output power (amplification) </li></ul><ul><li>Narrow line width because only few wavelength will experience a positive feedback and get amplified (optical filtering) </li></ul>
  • 18. LASER <ul><li>Absorption: An atom in the ground state might absorb a photon emitted by another atom, thus making a transition to an excited state. </li></ul><ul><li>Spontaneous Emission: Random emission of a photon, which enables the atom to relax to the ground state. </li></ul><ul><li>Stimulated Emission: An atom in an excited state might be stimulated to emit a photon by another incident photon. </li></ul>
  • 19. LIGHT DETECTORS <ul><li>PIN diode: </li></ul><ul><li>Photons are absorbed in the intrinsic layer </li></ul><ul><li>Sufficient energy is added to generate carriers in the depletion layer for current to flow through the device </li></ul>
  • 20. LIGHT DETECTORS <ul><li>APD (Avalanche photo diode): </li></ul><ul><li>Photo generated electrons are accelerated by relatively large reverse voltage and collide with other atoms to produce more free electrons </li></ul><ul><li>Avalanche multiplication effect makes APD more sensitive but also more noisy than PIN diode. </li></ul>
  • 21. OPTICAL AMPLIFIERS <ul><li>W ith the demand for longer transmission lengths, </li></ul><ul><li>optical amplifiers have become an essential </li></ul><ul><li>component in long-haul fiber optic systems which </li></ul><ul><li>lessen the effects of dispersion and attenuation </li></ul><ul><li>allowing improved performance of long-haul optical </li></ul><ul><li>systems. </li></ul>
  • 22. Types of optical amplifiers <ul><li>Semiconductor optical amplifiers (SOA) </li></ul><ul><li>Erbium doped fiber amplifiers (EDFA) </li></ul>
  • 23. Semiconductor Optical Amplifiers <ul><li>S emiconductor optical amplifiers (SOA) are essentially laser diodes, without end mirrors, which have fiber attached to both ends. They amplify any optical signal that comes from either fiber and transmit an amplified version of the signal out of the second fiber. </li></ul><ul><li>SOA are typically constructed in a small package, and they work for 1310 nm and 1550 nm systems. </li></ul><ul><li>The drawbacks to SOA include high-coupling loss, polarization dependence, and a higher noise figure </li></ul>
  • 24.                       
  • 25. EDFA <ul><li>EDFA allow information to be transmitted over longer distances without the need for conventional repeaters. The fiber is doped with erbium, a rare earth element, that has the appropriate energy levels in their atomic structures for amplifying light. </li></ul><ul><li>Functioning like a laser without mirrors, the EDFA uses a semiconductor pump laser to introduce a powerful beam at a shorter wavelength into a section of erbium-doped fiber several meters long. The pump light excites the erbium atoms to higher orbits, and the input signal stimulates them to release excess energy as photons in phase and at the same wavelength. EDFAs boost wavelengths in the 1550 nm range, and the pump light is typically 1480 nm or 980 nm. </li></ul>
  • 27. <ul><li>THANKS </li></ul>
  • Cox_AMT

    Jul 25, 2017
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