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Introduction 
 Vapor Phase Deposition (VPD) technique is a 
method of preparing the extremely pure optical 
glasses. 
 V...
Ingredients 
Starting Materials Dopants 
Starting materials are volatile 
organic compounds such as: 
o SiCl4 
o GeCl4 
o ...
Classification 
4 
Vapor Phase 
Deposition 
Flame Hydrolysis 
Vapor Axial 
Deposition (VAD) 
Outside Vapor 
Phase Oxidatio...
Schematic Illustration 
5
Outside Vapor Phase Oxidation (OVPO) 
o Uses flame hydrolysis stems from work on soot processes which were 
used to produc...
Outside Vapor Phase Oxidation (OVPO) (cont.) 
o The silica is regenerated as a fine soot which is deposited on a cool 
rot...
Vapor Axial Depositions (VAD) 
o Continuous technique for 
producing low loss optical 
fibers. 
o Vaporized constituents a...
Modified Chemical Vapor Deposition (MCVD) 
o Vapor-phase reactants (halide and 
oxygen) pass through a hot zone. 
o Glass ...
The MCVD Process 
10
Plasma-activated Chemical Vapor Deposition (PCVD) 
o PCVD is the stimulation 
of oxide formation by 
means of a non-isothe...
General Optical Fiber Making Process 
Fig: Double Circle Method Fig: Rod-in-tube Method 12
General Optical Fiber Making Process 
13
Summery 
o Both step index and graded index fibers are made with 
these processes. 
o Gives relatively similar performance...
Vapor Phase Deposition Techniques
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Vapor Phase Deposition Techniques

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Optical Fiber Making: Vapor Phase Deposition Techniques

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Vapor Phase Deposition Techniques

  1. 1. Introduction  Vapor Phase Deposition (VPD) technique is a method of preparing the extremely pure optical glasses.  Vapor Phase methods are the ones that are now used to produce silica-based fibers with very low attenuation, highest transparency with the optimal optical properties. 2
  2. 2. Ingredients Starting Materials Dopants Starting materials are volatile organic compounds such as: o SiCl4 o GeCl4 o SiF4 o BCL3 o O2 o BBr3 o POCl3 Refractive index modification is achieved through the formation of dopants from the non-silica starting materials: o TiO2 o GeO2 o P2O5 o Al2O3 o B2O3 o F 3
  3. 3. Classification 4 Vapor Phase Deposition Flame Hydrolysis Vapor Axial Deposition (VAD) Outside Vapor Phase Oxidation Process (OVPO) Chemical Vapor Deposition Modified Chemical Vapor Deposition (MCVD) Plasma-activated Chemical Vapor Deposition (PCVD)
  4. 4. Schematic Illustration 5
  5. 5. Outside Vapor Phase Oxidation (OVPO) o Uses flame hydrolysis stems from work on soot processes which were used to produce the first fiber with losses of less than 20 dBKm-1. o Oxygen is passed through the silicon compound which is vaporized removing impurities. o Dopants are added and gave following reactions: 6
  6. 6. Outside Vapor Phase Oxidation (OVPO) (cont.) o The silica is regenerated as a fine soot which is deposited on a cool rotating mandrel. The flame is reversed back and forth over the length of the mandrel for getting sufficient numbers of silica layers. o After the process ends, the mandrel is removed and the porous mass of silica soot is sintered. 7
  7. 7. Vapor Axial Depositions (VAD) o Continuous technique for producing low loss optical fibers. o Vaporized constituents are injected from burners and react to form silica soot by flame hydrolysis and makes a solid porous glass preform. o The preform is pulled upwards. o Dehydrated by heating with SOCl2 using the reaction: Fig: The VAD Process 8
  8. 8. Modified Chemical Vapor Deposition (MCVD) o Vapor-phase reactants (halide and oxygen) pass through a hot zone. o Glass particles formed during this reaction travel with the gas flow and are deposited on the walls of the silica tube. o The hot zone is moved back and forth along the tube allowing the particles to be deposited on a layer-by-layer basis giving a sintered transparent silica film on the walls of the tube. o Vaporized GeCl4 and POCl3 are added to the gas flow. o The core glass is then formed by the deposition of successive layers of germane-silicate or phosphor-silicate glass. o After the deposition is completed the temperature is increased to between 1700 and 1900 °C. The tube is then collapsed to give a solid preform which may then be drawn into fiber. 9 Fig: a) Deposition; b) Collapse to produce a preform; c) Fiber drawing
  9. 9. The MCVD Process 10
  10. 10. Plasma-activated Chemical Vapor Deposition (PCVD) o PCVD is the stimulation of oxide formation by means of a non-isothermal plasma maintained at low pressure in a microwave cavity (2.45 GHz) which surrounds the tube. o Volatile reactants are introduced into the tube where they react heterogeneously. o The reaction zone is moved backwards and forwards along the tube by control of the microwave cavity and a circularly symmetric layer growth is formed. 11 Fig: The PCVD Process
  11. 11. General Optical Fiber Making Process Fig: Double Circle Method Fig: Rod-in-tube Method 12
  12. 12. General Optical Fiber Making Process 13
  13. 13. Summery o Both step index and graded index fibers are made with these processes. o Gives relatively similar performance for the fabrication of both multi-mode and single-mode fibers. o MCVD and VAD technique employed together as MCVD-VAD hybrid technique for producing polarization maintaining fiber. 14

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