Fibre fabrication techniques type

  Fibre Fabrication Techniques 

• Instant of directly drawing the optical cable first the perform is prepared. 
• The perform consists both core and cladding layers. 
• The perform is a cylindrical structure about 25 mm in diameter and it consist silica composition.
• Once the perform is is prepared then it is become easy to draw the fibre optics cable from it.
• initially pure silica is obtained in the form of small particles which is called as soot.
• The different layers of soot are deposited on the glass rod to from cladding layer.
• Different methods used to purpose of performs are following

1. Vapour phase axial deposition (VAD)
2. Modified chemical vapour deposition (MVCVD)

Vapour phase axial deposition 

Vapour phase axial deposition block diagram.

In this method SiO2 particles are formed by deposition of vapors. As these particles emerge from the torches, they are deposited on to the end surface of silica glass rod which acts as a seed. A porous preform is grown in the axial direction by moving the rod upward.

The rod is also continuously rotated to  maintain cylindrical symmetry. Of the particle deposition. As the porous preform moves upward, it is transformed into a solid, transparent rod preform by zone melting (heating in a narrow localized zone) with the carbon ring heater. The resultant preform can be drawn into a fiber by heating it in another furnace. Both step-index and graded-index fibers in either multimode or single- mode varieties can be made by the VAD method. The advantages of the VAD method are:

1) The preform has no central hole as occurs in OVPO process
2) The preform can be fabricated in continuous lengths which can affect the process
costs and product yields
3) The fact that deposition chamber and the zone-melting ring heater are tightly
connected to each other in the same enclosure allows achievement of clean
environment.

Modified chemical deposition (MCVD)

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