Method for manufacturing a primary preform for optical fibres
AssigneeDraka Comteq B.V.
InventorsJohannes Antoon Hartsuiker, Igor Milicevic, Mattheus Jacobus Nicolaas Van Stralen, Eric Aloysius Kuijpers
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Abstract
A method for manufacturing a primary preform for optical fibers including surrounding at least part of a hollow substrate tube with a furnace set at a temperature T0, supplying doped or undoped gases to the inside of the tube, creating a reaction zone to promote deposition, and moving the zone back and forth along the length of the tube between to form at least one preform layer, wherein the temperature of the furnace is varied linearly as a function of the thickness of the at least one preform layer to compensate for temperature increases of the tube during deposition.
Claims14
A method for manufacturing a primary preform for optical fibres using an internal vapour deposition process, comprising the steps of:
- i) providing a hollow glass substrate tube having a supply side and a discharge side;
- ii) surrounding at least part of the hollow substrate tube with a furnace set at a temperature T0,
- iii) supplying doped or undoped glass-forming gases to the interior of the hollow glass substrate tube via the supply side;
- iv) creating a reaction zone with conditions such that deposition of glass on the inner surface of the hollow glass substrate tube takes place;
- and
- v) moving the reaction zone back and forth along the length of the hollow glass substrate tube between a reversal point located near the supply side and a reversal point located near the discharge side to form a first preform layer on the inner surface of the hollow glass substrate tube, the first preform layer comprising several glass layers;
- and
- vi) depositing at least a second preform layer comprising several glass layers on the first preform layer of step v) to form radially adjacent preform layers;
- wherein:
- a refractive index layer profile is generated between radially adjacent preform layers by varying temperature of the furnace surrounding the hollow glass substrate tube linearly as a function of preform layer thickness in the radial direction during at least part of step v) and/or step vi) during the deposition process and
- adding a refractive index altering material selected from the group consisting of a refractive index-increasing dopant, refractive index-decreasing dopant, or a combination thereof thereby increasing doping efficiency while compensating for temperature increase of the hollow glass substrate tube during deposition to obtain a constant refractive index in at least one preform layer in a radial direction when generating the refractive index layer profile between the radially adjacent preform layers.
Dependencies are inferred from the claim text.