Optical Fibre Production

Preform Manufacturing

Preforms are the layered cylinders of glass, made on lathes using chemical deposition vapor flows, burners for heating and melting glass and pressure control to retain the shape while it is being formed. Once complete, the preforms are stood upright in drawing towers and the lower end is drawn as a fibre, which is coated and taken up on a drum winder. Preforms incorporate both the core light transmission layers and the cladding, different layers of refractive density that keep the beam of light traveling down the fibre, instead of leaking out the sidewalls, even if the fibre bends and loops.

Manufacturers use MFCs to:

• Control fuel gas flows to burners – MFCs for H2, O2, Air, Acetylene, etc.
• Control flow of deposition gases – MFCs control carrier gases like N2. Ar and vapor of GeCl4, SiCl4, BoCl3, SF6
• Lay down process to compact layers against the core – MFCs for control of Cl2 and dual valve pressure controllers for pressure control to keep core from collapsing.

Fibre Drawing

Fibre drawing is the means of heating the end of a glass preform and shaping the melting end into a cone that creates a continuous stream of molten glass. This then descends and cools into a fibre which must then be guided in a way that will not break or alter it, while checking the thickness and adding layers to protect it.

In fibre draw processes, manufacturers use flow and pressure control to:

• Flow control in the furnace to prevent degradation of the element – MFCs to control Ar, N2
• Other curing processes in the system – MFCs to control the flow of N2, O2, Air, Ar
• Pressure control of the coating materials – PCs to control head pressure which determines thickness.

Ribbon Forming

Combining fibres into packaged strips of fibres for easy installation in groups, like ribbon cables of electrical wires.

• Mass flow controllers for control of process gases – N2, O2, Air. The gases control the cure rate of the polymers used to combine the individual fibres into the ribbon.
• Pressure controllers can be used to control head pressure of polymer dispensing system.

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