Abstract: The present invention relates to a system for manufacturing fibres comprising a melting furnace, a crucible within said furnace comprising at least one orifice (6) and at least one induction coil (4) for heating the melting furnace and the crucible. In a typical system according to the invention, the crucible comprises at least a first part (1) made of graphite and comprising said at least one orifice (6). The invention also relates to the use of the system as well as to a method for manufacturing fibres and to said fibres.

Abstract: An optical multimode fiber including a graded index core and an extended gradient core which has a negative refractive index difference with respect to the cladding. The fiber improves the bandwidth, reliability and complexity of the telecommunication systems that are based on multimode fibers. The fiber reduces the differential mode delay among modes. The fiber thereby allows achieving large bandwidth even in the case when the highest order modes are excited. This has positive effects to the conditions that need to be fulfilled by the components such as optical sources, connectors, fiber couplers, other optical components, cables, etc. The fiber eliminates negative impact of the cladding that allows for reduction of fiber core size and the difference between the cladding and the core and thereby allows for achieving the larger bandwidth of optical fiber at lower fiber production cost.

Abstract: A preform, a head part for a preform and a method for manufacturing a fiber. The head part is adapted to be attached to a preform of a fiber. The head part has such a shape that a heat load directed to the preform will be distributed to the cross section of the bulk part in a predetermined manner, like evenly distributing the heat load to the cross section of the preform. When manufacturing a fiber from a preform including such a head part the heating of the preform is more controllable thus resulting in a fiber with a better quality.

Abstract: A heating apparatus for preparing an optical fiber from a preferably vertical fiber preform in a draw furnace, in which draw furnace the fiber preform is heated with the heating apparatus in the heating zone of the draw furnace in such a way that a molten, downwards tapering zone is formed in the preform, from which a thin fiber is produced by means of gravity and/or drawing the fiber downwards, which heating apparatus comprises at least a preferably tubular heating element, placed around the fiber preform in the draw furnace, for heating the fiber preform, and a heating means placed around the heating element in the draw furnace, for heating the heating element, as well as an insulator element around the heating element. The heating element and the insulator element are surrounded at least partly by a radiation shielding to reflect thermal radiation from the heating element to the insulator element back to the heating element.