Process of and apparatus for manufacturing optical fibres for operation in the medium infrared transmission range

Claim 2

Process of manufacturing optical fibres for operation in the medium infrared transmission range, wherein a preform is formed which is made from metal halide glasses obtained by vapour phase reaction between an organo-metallic compgund of the element whose halide is to be obtained and a gaseous reactant containing the halogen, characterized in that the rtction is started at ambient temperature by ultraviolet radiation, and the halides produced undergo a thermal treatment so as to meet thermophoretic deposition conditions and to obtain the subsequent preform consolidation and vitrification and the annealing thereof.

Claim 3

Process according to claim 1, characterized in that both the reaction producing the fibre core materials and that which produces the fibre cladding materials are started by UV radiation.

Claim 4

Process according to claim 1 or 2, characterized in that for the thermal treatment the material produced is brought to a first temperature, which is relatively high but lower than the vitrification temperature, to promote exhaust of the volatile products and to start the deposition; afterwards the material is passed into a zone where the temperature first progressively decreases so as to meet thermophoretic deposition conditions, then increases up to the melting point, and lastly sharply decreases for consolidation and vitreous matrix formation; and finally the material is passed into another zone with constant temperature equal to the vitreous tran- sistion temperature for the annealing.

Claim 5

Process according to claim 3, characterized in that during the fabrication of the vitreous matrix the deposited material is treated with an inert gas and a halogen to eliminate impurities.

Claim 6

Apparatus for manufacturing optical fibres for operation in the medium infrared transmission range, comprising means (36,38) for drawing a preform obtained from a matrix (100) composed of metal halide glasses obtained by vapour-phase reaction between an organo-metallic compound of the element whose halide is to be obtained and a gaseous reactant containing the halogen, characterized in that it comprises, upstream the drawing means (36-38): - a reaction chamber (1; 11, 21) at ambient temperature, into o which vapour-phase reactants are introduced, and which is associated with a system (2; 12, 22) for generating UV radiations and concentrating same in the reaction chamber; - a deposition and vitrification chamber (3; 6, 30) associated with means (4; 40, 41) for subjecting the halide produced by the reaction to the thermal treatments necessary to start and carry out the axial deposition and the consolidation and vitrification of the deposited material; - a chamber (35) for annealing the preform resulting from vitrification.

Claim 7

Apparatus for manufacturing optical fibres for operation in the medium infrared transmission range, comprising means (36,38) for drawing a preform obtained from a matrix (100) composed of metal halide glasses obtained by vapour-phase reaction between an organo-metallic compound of the element whose halide is to be obtained and a gaseous reactant containing the halogen, characterized in that it comprises, upstream the drawing means (36-38): - a reaction chamber (1; 11, 21) at ambient temperature, into o which vapour-phase reactants are introduced, and which is associated with a system (2; 12, 22) for generating UV radiations and concentrating same in the reaction chamber; - a deposition and vitrification chamber (3; 6, 30) associated with means (4; 40, 41) for subjecting the halide produced by the reaction to the thermal treatments necessary to start and carry out the axial deposition and the consolidation and vitrification of the deposited material; - a chamber (35) for annealing the preform resulting from vitrification.

Claim 8

Apparatus according to claim 5, characterized in that said reaction chamber comprises two coaxial rooms (11, 21) for the reactions intended to produce fibre-core and cladding material, each room being equipped with its own system (12, 22) for starting the reaction by UV radiation, and said second chamber (30) comprises two coaxial rooms separated by porous partitions (31, 32) defining two fixed paths for core and cladding material deposition and letting reaction volatile products pass to a sucking conduit (33).

Claim 9

Apparatus according to claim 5 or 6, characterized in that the means (40, 41) for thermal treatment define inside said deposition chamber (30) two axially subsequent zones, the first being at high and constant temperature, even though lower than vitrification temperature, while in the second chamber the temperature first gradually decreases to meet thermophoretic deposition conditions, hence it increases again up to the values corresponding to melting point and finally presents a sharp decrease down to values which can be lower than 0°C.

Claim 10

Apparatus according to claim 7, characterized in that in correspondence with said second zone the deposition chamber comprises a conduit (34) for introducing inert gas and halogen to eliminate impurities in the deposited material.