Patent ID: 7062942

Claim:
A method of making an optical fibre comprising the steps of: a) providing an increased diameter portion on a glass rod, said glass rod including an outer longitudinal surface and a predetermined diameter; b) positioning said rod within a glass tube defined by a peripheral glass wall having an internal and an external surface, respectively, wherein said glass tube has an internal diameter which is greater than said predetermined diameter of said rod and, at least in a portion thereof, smaller than the diameter of said increased diameter portion of the rod, thereby causing said increased diameter portion of the rod to be in engagement with said tube; c) vertically positioning and mechanically supporting said tube to provide a vertically oriented rod and tube assembly including an upper end zone and a lower end zone, wherein said mechanically supporting of said tube and said engagement of said increased diameter portion of the rod with said tube are carried out in a respective portion of the upper end zone of said assembly, thereby causing said rod to be vertically supported within said tube by said increased diameter portion engaging said tube and to define an annular gap between the outer surface of said rod in the non-increased diameter portion thereof and the internal surface of said tube; d) providing a passage in said upper end zone of the assembly, below said increased diameter portion of the rod, in order to allow a fluid contained in said gap to flow out from said gap wherein said passage in said upper end portion of the assembly is provided on the wall of said tube, said passage having a first end opening on the internal surface of said tube into said annular gap and a second end opening on the external surface thereof towards the outside of said assembly; e) thermally collapsing said tube onto said rod at the lower end zone of the rod and tube assembly, such that at least a portion of said tube fuses to said rod; and f) drawing an optical fibre from said collapsed portion of said rod and tube assembly.