Optical ceramics
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  • 2. contents- Introduction- General structures and properties- Case study : fiber optics- Introduction- Optical Fiber & Communications System- Modes and materials- Optical fibers processing- Applications- Applications- Conclusions and References
  • 3. Introduction
  • 4. Optical ceramics Materials with special light reflecting,transmitting or other optical propertiesinclude a wide range of glass compositions,glass ceramics, and selected ceramics. Classification: Transparent ceramics : glass, optical fibers,opticalswitches, laser amplifiers and lenses… Glass coloring Luminessence ceramics…
  • 5. OPTICAL PROPERTIES OF CERAMICS-REFRACTIONLight that is transmitted from onemedium into another, undergoesrefraction.Refractive index, (n) of a material isthe ratio of the speed of light in avacuum (c = 3 x 108 m/s) to the speedof light in that material.n = c/v5
  • 7. OPTICAL PROPERTIES OF CERAMICSCallister, W., D., (2007), Materials Science And Engineering, 7th Edition,730.04.2013
  • 8. OPTICAL PROPERTIES OF CERAMICSABSORPTION•Color in ceramicsMost dielectric ceramics andglasses are colorless.By adding transition metals(TM)Ti, V, Cr, Mn, Fe, Co, NiCarter, C., B., Norton, M., G., Ceramic Materials Science And Engineering,8
  • 9. Case study: fiber optics(optical fibers )
  • 10. Introduction An optical fiber is essentially awaveguide for light It consists of a core andcladding that surrounds thecore The index of refraction of thecladding is less than that ofthe core, causing rays of lightleaving the core to berefracted back into the core A light-emitting diode (LED)or laser diode (LD) can beused for the source
  • 11. Optical Fiber &Communications System
  • 12. Optical Fibers It has little mechanical strength, so it must beenclosed in a protective jacket Often, two or more fibers are enclosed in the samecable for increased bandwidth and redundancy in caseone of the fibers breaks It is also easier to build a full-duplex system using twofibers, one for transmission in each direction- Fiber optics ( optical fibers) is a flexible, transparentfiber made of glass (silica) or plastic, slightly thickerthan a human hair. It functions as a waveguide, or“light pipe”,to transmit light between the two endsof the fiber
  • 13. Types of Fiber Both types of fiber described earlier are known as step-index fibers becausethe index of refraction changes radically between the core and the cladding Graded-index fiber is a compromise multimode fiber, but the index ofrefraction gradually decreases away from the center of the core Graded-index fiber has less dispersion than a multimode step-index fiber
  • 14. Why are fiber-optic systems revolutionizingtelecommunications?Compared to conventional metal wire(copper wire), optical fibers are……….
  • 15. Less costSeveral miles of optical cable can be madecheaper than equivalent lengths of copperwire. This saves your provider (cable TV,Internet) and you money.
  • 16. Smaller-ThinnerOptical fibers can be drawn to smallerdiameters than copper wire.
  • 17. Higher carrying capacityBecause optical fibers are thinner than copperwires, more fibers can be bundled into a given-diameter cable than copper wires. This allowsmore phone lines to go over the same cable ormore channels to come through the cable to yourtv.
  • 18. Less Signal Degradation- The loss of signal in optical fiber is lessthan in copper wire, so there is far less“bleeding” on the lines.
  • 19. Light signalsUnlike electrical signals in copper wires, lightsignals from one fiber do not interfere with thoseof other fibers in the same cable. This meansclearer phone conversations or TV reception.
  • 20. Low power RequirementBecause signals in optical fibers degrade less,lower-power transmitters can be used instead ofthe high-voltage electrical transmitters neededfor copper wires. Again, this saves your providerand you money.
  • 21. Digital signalsOptical fibers are ideally suited for carryingdigital information, which is especially useful incomputer networks.
  • 22. Non-flammableBecause no electricity is passed throughoptical fibers, there is no fire hazard.
  • 23. LightweightAn optical cable weighs less than a comparablecopper wire cable. Fiber-optic cables take up lessspace in the ground.
  • 24. how do we make an opticalfiber? Materials : glass (silica) or plastic Making optical fibers requires thefollowing steps: Making a preform glass cylinder Drawing the fibers from thepreform Testing the fibers
  • 25. Making a preform glass cylinder Purifying silica Mine sand (raw silica) React with chlorine to produce SiCl4 and other metalsfrom the impurities in the sand (FeCl3, etc.) Heat this mixture (essentially distilling) Collect SiCl4 vapors only Condense the pure SiCl4 vapors
  • 26. modified chemical vapordeposition (MCVD). Prepare a silica tube (glass extrusion). Heat the tube Inject SiCl4 and O2 into the tube At the heated portion, the SiCl4 is oxidizedThe lathe turns continuously to make an evencoating and consistent blank UItra pure SiO2 is deposited on the inner wallsof the tube Draw the tube through the furnace, continuouslycoating the inner walls. SiO2 particles deposit and sinter along thetube, leaving a hollow core [for now].2224 2ClSiOOSiCl heat
  • 27. modified chemical vapordeposition (MCVD).
  • 28.  This technique can be used to manufacture very longfibres (50 km). It is used for both step-index and graded-index fibres.Plasma-Enhanced Modified Chemical VapourDeposition (PMCVD)
  • 29. Fiber drawing and protecting Anneal the multiwalled tube to the glass softening temperature. The tube and inner coating collapse to a solid, multilayered rod. Fire the rod at an even higher temperature softening it further. Draw the fiber through a nozzle, thinning the fiber dramatically. Core diameters from <5 to 500 um are used. Polymer coatings must also be applied. Fibers are finally bundled.
  • 30. Fiber drawing- The tip of the preform is heated toabout 2000 oC in a furnace.- As the glass softens, a thin strandof softened glass falls by gravityand cools down.- As the fiber is drawn its diameter isconstantly monitored- A plastic coating is then applied tothe fiber, before it touches anycomponents.- The fiber is then wrapped around aspool.
  • 31. Continuous production Fibers are drawn at 30 to 60feet per second. Multiple polymer coatingsmay be applied Thermoplastic (buffer) Aramid (strength) PVC of fluoride co-polymer Spools of up to severalkilometers are wound.2000 C
  • 32. Fiber optic diameter Plastic fiber has a core diameter of upto 900 micrometer. 20-30 feet max length. Easy to work with. Cheap. Glass fibers have cores from 8 to 62.5micrometer across. Connecting two fibers end-to-end isthe hardest par—requires amicroscope or an automaticconnection of some kind.
  • 33. Fiber testing Fibers must generally pass the following tests Tensile strength greater than 100,000 lb/in2 Dimensional tolerance Temperature dependence Optical properties
  • 34. Importance of Fiber Purity This complicated procedure is necessary due to the incredible sensitivity ofoptical fiber communications to impurities and flaws. Fiber optics only became a reality in 1970, when Corning figured out how tomake fiber optics with less than 99% loss/km. Light transmission through 1 km of fiber drops to 1% of the input intensity ifthere are only: 2 Co atoms per billion 20 Fe atoms per billion 50 Cu atoms per billion Transmission in modern fibers is still limited to: 60 to 75 percent/km for light with a wavelength of 850 nm. Transmission losses <1% have been achieved over >3000 miles.
  • 35. Repeating Stations Repeating stations are generally placed at regular distancesalong a fiber network to detect and amplify the signals since losswill occur over km, or hundreds of km, of fiber. When light drops to 95% of transmission, a repeating stationis required. Since the cost of the repeaters is high compared to fiber,tremendous effort goes into making pure, flaw free opticalfibers. Repeating stations today are generally 100 km apart for majorfiber bundles (trans-oceanic, etc).http://www.telebyteusa.com/foprimer/foch2.htm
  • 36. disadvantages difficult to install and test optical fibers fiber is a less familiar technology andrequires skills Fibers can be damaged easily if bent toomuch fiber interfaces cost more than electricalinterfaces
  • 37. Future fiber optic manufacturing? Why bother purifying Si and the trouble of making pureand flaw-free fiber optics when a spider does it naturally?http://www.newscientist.com/article.ns?id=dn3522
  • 38. APPLICATIONS- Optical fiber communication :telecommunicationand computer networking- Fiber optic sensors ( removesensing )- Other uses…
  • 39. Optical fiber communication
  • 40. Fiber optic sensing systems (opticalsensors )Two types :-Intrinsic sensor : the sensors are internal or embedded into thefibers-Extrinsic sensors : the transducer is external to the fiber
  • 41. how the environmental signal isdetected Informations (in terms ofintensity, phase, frequency,polarization, spectral content,etc.) are printed into the lightbeam and is carried through theoptical fiber to an optical and/orelectronic processor.The environmental signal isperceived by the fiber optic itself( as the light modulator )-intrinsic sensor can be classifiedas a distributed sensor, since itallows the measurement to takeplace in any point along the opticfiber.
  • 42. Properties of Fiber OpticSensing - Highly sensitive (more than other technologies) - Configuration versatility - point and distributed configurations possible - Dielectric construction (can be used with high voltages, high temperatures,and stressed environments) -Wide dynamic range - Multiplexing capabilities - Freedom from electromagnetic interface (fibers carry no current) - Chemically passive - Provide real-time feedback - Resistant to corrosion - Multi point measurement (intrinsic sensors) or specific location sensing(extrinsic sensors)
  • 43.  -Ability to measure a wide range of different properties (wide rangeof applications) - High resistance to extreme environments due to their robustnessand immunity to both electromagnetic and radio frequencyinterference (intrinsic sensors). -They do not conduct electricity which means that themeasurements are not easily affected by external causes (intrinsicsensors). - Extremely small size - Remotely powered -Ability to measure direct physical strain. - Sensors can placed upon the optic fiber
  • 44. Input and Output Input: Light beam that carries the information Output:-Extrinsic: 1. encoder plates/disks: linear and angular position 2. Evanescence: temperature, strain 3. reflection and transmission: pressure, flow, damage 4. Laser Doppler velocimetry: flow measurement 5. total internal reflection: liquid level, pressure 6. absorption Band edge: temperature 7. Gratings: Pressure,Acoustics, vibrations 8. Photo elastics effects: pressure, acceleration, vibration, rotatory, position. 9. Fluorescence: temperature, viscosity, chemical analysis. 10. Pyrometers: temperature.- Intrinsic: 1. Microbends sensors: strain, pressure, vibration. 2. blackbody sensors: temperature 3. interferometryc sensors: rotation acceleration, acoustics, magnetic fileds,electric fields, strain, temperature, pressure, current.
  • 45. Uses of Fiber optic sensingsystems testing machinery monitoring conditions in bridges or windturbines. used for industrial automation, biomedical technologies for digitaldiagnostic imagery, Endoscopy… military, space, and automotive applications.
  • 46. Example: Uses of Fiber opticsensing systems in Endoscopy
  • 47. SUMMARY Optical Fiber Processing Initial tube CVD of core Sintering and annealing coating applications
  • 48. references Callister, W., D., (2007), Materials Science And Engineering, 7thEdition, http://www.laserfocusworld.com/articles/2011/01/medical-applications-of-fiber-optics-optical-fiber-sees-growth-as-medical-sensors.html http://en.wikipedia.org/wiki/Optical_fiber http://www.ofsoptics.com/fiber/ http://www.madehow.com/Volume-1/Optical-Fiber.html#b [4] John Crisp, Barry Elliott, Introduction to Fiber Optics, 3rdedition, Newnes, 2005 http://www.fiberopticproducts.com/ http://www.fiber-optics.info/ ………………………..