Method of manufacturing a fibre-optical coupling element

Claim 1

A method of manufacturing a fibre-optical coupling element comprising at least two monomode fibres fused together over a given length and each comprising a fibre core of core glass and a fibre cladding of cladding glass, in which fibres are used the cladding glass of which has a refractive index and a softening temperature lower than the refractive index and the softening temperature of the core glass, the two fibres are positioned so that their parts to be fused contact each other, are pressed against each other and are then heated at the part to be fused in a manner such that the cladding glass softens, the spacing between the fibre cores is reduced and the two fibres are fused together without softening of the fibre cores, whereupon the fibres thus fused are fixed to form a coupling element by cooling to room temperature, characterized in that fibres are chosen, the fibre core of which is made of a core glass the American softening temperature of which is at least 80°C higher than the American softening temperature of the cladding glass of which the fibre cladding is made, and in that the fibres are heated to a temperature lying between 520 and 560°C, at which the cladding glass has a viscosity between 10 8.6 and 10 6.7 Paes, whereas the core glass has a viscosity between 10 10.5 and 10 8.7 Pa.s.

Claim 2

A method of manufacturing a fibre-optical coupling element comprising at least two monomode fibres fused together over a given length and each comprising a fibre core of core glass and a fibre cladding of cladding glass, in which fibres are used the cladding glass of which has a refractive index and a softening temperature lower than the refractive index and the softening temperature of the core glass, the two fibres are positioned so that their parts to be fused contact each other, are pressed against each other and are then heated at the part to be fused in a manner such that the cladding glass softens, the spacing between the fibre cores is reduced and the two fibres are fused together without softening of the fibre cores, whereupon the fibres thus fused are fixed to form a coupling element by cooling to room temperature, characterized in that fibres are chosen, the fibre core of which is made of a core glass the American softening temperature of which is at least 80°C higher than the American softening temperature of the cladding glass of which the fibre cladding is made, and in that the fibres are heated to a temperature lying between 520 and 560°C, at which the cladding glass has a viscosity between 10 8.6 and 10 6.7 Paes, whereas the core glass has a viscosity between 10 10.5 and 10 8.7 Pa.s.