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US 6,845,204 B1Granted
Photonic band gap fiber
AssigneeCrystal Fibre A/S
InventorsJes Broeng, Stig Eigil Barkou, Anders Overgaard Bjarklev
Life of this patent
Estimating the term…
Abstract
An optical fiber having a periodical cladding structure providing an photonic band gap structure with superior qualities. The periodical structure being one wherein high index areas are defined and wherein these are separated using a number of methods. One such method is the introduction of additional low index elements, another method is providing elongated elements deformed in relation to a circular cross section. Also described is a cladding structure comprising elongated elements of a material having an index of refraction higher than that of the material adjacent thereto. Using this additional material, prior art structures may obtain much better qualities.
Claims54
An optical fibre with a waveguide structure having a longitudinal direction, said optical fibre having:
- a core region extending along the longitudinal direction,
- a cladding region extending along the longitudinal direction, said cladding region comprising an at least substantially two-dimensionally periodic structure comprising primary, elongated elements each having a centre axis extending in the longitudinal direction of the waveguide, the primary elements having a refractive index being lower than a refractive index of any material adjacent to the elongated elements,
- the periodic structure being defined, in a cross-section perpendicular to the longitudinal direction, by a unit cell, where the sum of all areas of elongated elements, which areas are comprised within the unit cell, is larger than 1.2 times the area of that primary element having its centre axis not positioned outside the unit cell and having the largest area;
- and
- wherein the periodic structure comprises secondary elongated elements having a refractive index being larger than that of any material adjacent thereto and to any material being adjacent to a primary element.
2 more elements
An optical fibre with a waveguide structure having a longitudinal direction, said optical fibre having:
- a core region extending along the longitudinal direction,
- a cladding region extending along the longitudinal direction, said cladding region comprising an at least substantially two-dimensionally periodic structure comprising primary, elongated elements each having a centre axis extending in the longitudinal direction of the waveguide, the primary elements having a refractive index being lower than a refractive index of any material adjacent to the primary elements,
- the periodic structure being, in a cross-section perpendicular to the longitudinal direction, defined by a unit cell, where, in each unit cell:
- ndΛ2>nudΛ1(√3)
- where
- nd is the largest index of refraction within a first circle which is defined as a largest circle possible having a centre not positioned outside the unit cell and not enclosing any part of any primary element,
- nud is a largest index of refraction not positioned outside the unit cell but outside any of the first circles of the unit cells,
- Λ1 is a smallest distance between centre axes of two primary elements within the periodic structure,
- Λ2 is a distance between the centre of the first circle of the unit cell and the centre of the first circle of an adjacent unit cell.
6 more elements
An optical fibre with a waveguide structure having a longitudinal direction, said optical fibre having:
- a core region extending along the longitudinal direction,
- a cladding region extending along the longitudinal direction, said cladding region comprising an at least substantially two-dimensionally periodic structure comprising primary, elongated elements each having a centre axis extending in the longitudinal direction of the waveguide, the primary elements each having a refractive index being lower than a refractive index of any material adjacent to the primary element,
- the periodic structure being, in a cross-section perpendicular to the longitudinal direction, defined by a unit cell, and where a polygon is defined:
- having centres of primary elements in its vertices,
- not enclosing any centres of other primary elements than those having their centres at the vertices of the polygon, and
- having an area less than or equal to that of the unit cell,
- the polygon being a regular, hexagonal polygon;
- and
- wherein the periodic structure further comprises one or more secondary elongated elements having a refractive index higher than that of any material adjacent thereto or adjacent to any primary elements, the secondary elements each has a centre axis extending in the longitudinal direction of the fibre.
6 more elements
An optical fibre with a waveguide structure having a longitudinal direction, said optical fibre having:
- a core region extending along the longitudinal direction,
- a cladding region extending along the longitudinal direction, said cladding region comprising an at least substantially two-dimensionally periodic structure comprising primary, elongated elements each having a centre axis extending in the longitudinal direction of the waveguide, the primary elements each having a refractive index being lower than a refractive index of any material adjacent to the primary element,
- the periodic structure further comprising secondary, elongated elements each having a refractive index being larger than that of any material adjacent thereto and any material adjacent to a primary element, each secondary element having a centre axis extending in the longitudinal direction of the fibre.
An optical fibre with a waveguide structure having a longitudinal direction, said optical fibre having:
- a core region extending along the longitudinal direction,
- a cladding region extending along the longitudinal direction, said cladding region comprising an at least substantially two-dimensionally periodic structure comprising primary, elongated elements each having a centre axis extending in the longitudinal direction of the waveguide, the primary elements each having a refractive index being lower than a refractive index of any material adjacent to the primary element,
- the periodic structure being, in a cross-section perpendicular to the longitudinal direction, defined by a unit cell, and where a polygon is defined:
- having centres of primary elements in its vertices,
- not enclosing any centres of other primary elements than those having their centres at the vertices of the polygon, and
- having an area less than or equal to that of the unit cell,
- the polygon being a regular, hexagonal polygon;
- wherein the core region comprises a first additional elongated element extending in the longitudinal direction of the fibre.
5 more elements
Dependencies are inferred from the claim text.