Optical devices and methods of manufacture thereof
First Claim
1. An optical fibre having a core, a photosensitive inner cladding and a further cladding surrounding the photosensitive inner cladding, the core being arranged to permit a light beam to travel therethrough, the fibre having a first end zone in which the inner cladding has a plurality of refractive indices along a longitudinal axis of the fibre, the fibre further having a second end at which it is compatible with a standard fibre, said refractive indices being such that in use the light beam travels along the fibre, the refractive indices defining a taper such that at a free-space end of the fibre the diameter of the core is increased to a enlarged core diameter equal to that of the core plus the inner cladding;
- and whereby at said free-space end the fibre has a V number greater than that of the standard fibre, wherein the outer dimension of the fibre is unchanged along its length.
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Accused Products
Abstract
An optical fiber (12), which presents a beam expanding feature, has a core, an inner cladding, an outer cladding and a sheath. The inner cladding is doped with a photosensitive material like germanium. By using ultra-violet radiation (16) from a copper laser (18) having a Gaussian energy distribution, a refractive index taper may be created inside the fiber. Therefore the tapered fiber has a larger effective area in the coupling region (20), and insertion losses are reduced.
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Citations
8 Claims
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1. An optical fibre having a core, a photosensitive inner cladding and a further cladding surrounding the photosensitive inner cladding, the core being arranged to permit a light beam to travel therethrough, the fibre having a first end zone in which the inner cladding has a plurality of refractive indices along a longitudinal axis of the fibre, the fibre further having a second end at which it is compatible with a standard fibre, said refractive indices being such that in use the light beam travels along the fibre, the refractive indices defining a taper such that at a free-space end of the fibre the diameter of the core is increased to a enlarged core diameter equal to that of the core plus the inner cladding;
- and whereby at said free-space end the fibre has a V number greater than that of the standard fibre, wherein the outer dimension of the fibre is unchanged along its length.
- View Dependent Claims (2, 3, 4, 8)
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5. A method of increasing the offset coupling tolerance of an optical fibre, comprising
providing said optical fibre having first and second ends, wherein said fibre has a core, a photosensitive inner cladding and an outer cladding, wherein the refractive index of the core is greater than that of the inner cladding and that of the outer cladding, wherein at least at one end the fibre is compatible with a standard fibre; illuminating the optical fibre with electromagnetic radiation on the end face at the other end of the fibre, whereby the refractive index of the photosensitive inner cladding increases along the fibre to said end face such that at the end face the index of the inner cladding matches onto that of the core, whereby the core diameter at said end face is raised to that of the core plus the inner cladding, wherein the V number at the end face is greater than that of a standard fibre, the increased V number and core diameter increasing the spot size and the coupling tolerance. - View Dependent Claims (7)
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6. A method of increasing the offset coupling tolerance of an optical fibre, comprising:
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providing said optical fibre having first and second ends, wherein said fibre has a core, a photosensitive inner cladding and an outer cladding, wherein the refractive index of the core is greater than that of the inner cladding and that of the outer cladding, wherein at least at one end the fibre is compatible with a standard fibre;
illuminating the optical fibre in the other end region thereof with electromagnetic radiation transverse the length of the fibre, whereby the refractive index of the photosensitive inner cladding increases along the fibre to said end such that at the end the index of the inner cladding matches onto that of the core, whereby the core diameter at said end face is raised to that of the core plus the inner cladding, wherein the V number at the end face is greater than that of a standard fibre, the increased V number and core diameter increasing the spot size and the coupling tolerance.
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Specification