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Fiber Materials & Fabrication
Available at kalyan5.blogspot.in
OFC Unit 4
Kalyan AcharjyaE-mail: [email protected]
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Reference-Chapter 6
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Already Covered:
Fiber Materials Requirements (SiO2).
Important Desirable Characteristics of Fiber Materials.
Which Materials used for Doping
Oxide or Fluride
What is ZBLAN or ZHBLAN?
Active Fibers (Doped with rare earth elements, such as
Erbium & Neodymium)
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Fiber Materials Requirements
It must be possible to make long thin, flexible fibers from the
material
Material must be transparent at a particular optical wave length
in order for fiber to guide light efficiently
Physically compatible materials that have slightly different
refractive indices for core and cladding must be available
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Types of Fiber
Glass Fiber
Plastic Fiber
Photonic Crystal Fiber
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Methods to Manufacture:
Liquid Phased (or Melting ) Method
Chemical Vapour-phased oxidation Method
Optical Glass Fiber
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Liquid Phased (or Melting ) Method
Draw the fiber from molten glasses, which are placed in
two concentric crucibles (Double Crucible method)
or Draw from a glass rod called preform.
Fabrication of the Preform
Drawing the fiber from the Preform
Coating, Jacketing and labeling Process
Now a Days most fab foundry used Preform Method
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Liquid Phased (or Melting ) Method
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Liquid Phased (or Melting ) Method
Prefrom is fed into circular heater called drawing
furnace.
Preform end is softened to the point where it can be
drawn into a very thin filament which becomes optical
fiber
The speed of the drum at the bottom of draw tower
determines how fast and in turn how thick the fiber is
An elastic coating is applied to protect the fiber
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Liquid Phased (or Melting ) Method
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Double Crucible Method
Silica and halide glass fiber can all be made using a direct-
melt double crucible technique
Glass rods for the core and cladding materials are first
made separately by melting mixtures of purified powders
These rods are then used as feedstock for each of two
concentric crucibles
Advantage of this method is being a continuous process
Careful attention must be paid to avoid contaminants
during melting
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Vapour-phased oxidation Method
1. Modified ChemicalVapor Deposition (MCVD)
2. Plasma Modified ChemicalVapor Deposition (PMCVD)
3. Plasma ChemicalVapor Deposition (PCVD)
4. OutsideVapor Deposition (OVD)
5. Vapor-phase Axial Deposition (AVD)
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Chemical Vapor Deposition (CVD)
All these methods are based on thermal chemical vapor reaction that forms
oxides
They are deposited as layers of glass particles called soot
Starting materials are solutions of SiCl4, GeCl4, POCl3, and gaseous BCl3.
These liquids are evaporated within oxygen stream and form silica and other
oxides.
Chemical reactions proceed as follows:
SiCl4 + O2 -> SiO2 + 2 Cl2GeCl4 + O2 -> GeO2 + 2 Cl24 POCl3 + 3 O2 -> 2 P2O5 + 6 Cl24 BCl3 + 3 O2 -> 2 B2O3 + 6 Cl2
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Remember!
Germanium dioxide and phosphorus pentoxide increase
the refractive index of glass
Boron oxide decreases the refractive index of glass.
These oxides are known as dopants.
Changing composition of the mixture during the processinfluences refractive index profile of the preform
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Chemical Vapor Deposition (CVD)
Chemical Vapor Deposition is chemical reactions which
transform gaseous molecules, called precursor, into a
solid material , in the form of thin film or
powder, on the surface of a substrate .
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Modified Chemical Vapor Deposition (MCVD)
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For Detail Please Read: Chapter 6
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Fiber Cable:
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