Abstract: A method of manufacturing a microstructured fiber, includes: providing a preform having a plurality of elongate holes; mating at least one, but not all, of the holes with a connector to connect the hole(s) to an external pressure-controller; drawing the preform into the fiber while controlling gas pressure in the hole(s) connected to the pressure-controller.

Abstract: A method of manufacturing a microstructured fibre, includes: providing a preform having a plurality of elongate holes; mating at least one, but not all, of the holes with a connector to connect the hole(s) to an external pressure-controller; drawing the preform into the fibre whilst controlling gas pressure in the hole(s) connected to the pressure-controller.

Abstract: A birefringent elongate waveguide for guiding light, comprises: a core region (110), comprising an elongate region of relatively low refractive index; and a cladding region (100), comprising elongate regions (105) of relatively low refractive index interspersed with elongate regions (117,120) of relatively high refractive index. In a transverse cross-section of the waveguide, a (5) relatively high refractive index boundary region (115) is provided that surrounds the core region and has either (1) at most two-fold rotational symmetry or (2) a rotational symmetry that reduces the rotational symmetry of the waveguide to at most two-fold rotational symmetry. The symmetry of the boundary region (115) results at least in part from azimuthal variations therein, which are substantially uncharacteristic of the cladding region (100).

Abstract: An elongate waveguide for guiding light including a core having an elongate region of relatively low refractive index; a microstructured region around the core comprising elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index; and a boundary at the interface between the core and the microstructured region, the boundary including, in the transverse cross-section, a region of relatively high refractive index, which is connected to the microstructured region at a plurality of nodes, and at least one relatively enlarged region around the boundary, the enlarged region having a major dimension and a minor dimension, wherein the length of the major dimension divided by the length of the minor dimension is more than 3.0.

Abstract: An elongate waveguide for guiding light including a core having an elongate region of relatively low refractive index; a microstructured region around the core comprising elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index; and a boundary at the interface between the core and the microstructured region, the boundary including, in the transverse cross-section, a region of relatively high refractive index, which is connected to the microstructured region at a plurality of nodes, and at least one relatively enlarged region around the boundary, the enlarged region having a major dimension and a minor dimension, wherein the length of the major dimension divided by the length of the minor dimension is more than 3.0.

Abstract: An elongate waveguide for guiding light includes a core having an elongate region of relatively low refractive index; a microstructured region around the core having elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index; and a boundary at the interface between the core and the microstructured region, the boundary including in the transverse cross-section, a region of relatively high refractive index, which is connected to the microstructured region at a plurality of nodes, at least one relatively enlarged region around the boundary (and excluding a boundary having twelve nodes and six enlarged regions substantially at a mid-point between six pairs of relatively more-widely-spaced apart neighboring nodes).

Abstract: Photonic crystal fibers that guide light by virtue of a photonic band gap. Fibers that are formed from materials having higher refractive indices than silica are provided using an optical waveguide including a core with a relatively low refractive index and a photonic band gap structure that can substantially confine light to the core. The structure includes elongate regions of relatively low refractive index interspersed with elongate regions of relatively high refractive index, with the band gap residing above the fifth photonic band of the band gap structure.

Abstract: A holey optical fibre for supporting propagation of light of a wavelength ?,comprises a plurality of cylinders (10) each having a longitudinal axis, the cylinders (10) being separated from each other by regions of a matrix material (20) and having their longitudinal axes substantially parallel to each other. Each cylinder (10) has a diameter, in the plane perpendicular to the longitudinal axis, that is small enough for the composite material of the ensemble of cylinders and matrix material to be substantially optically homogenous in respect of light of wavelength ?.

Abstract: A method of joining a first optical fiber (110) to a second optical fiber (130) comprises the steps of: (i) providing a preform element (10) comprising material defining a primary elongate cavity (40); (ii) inserting the first optical fiber (110) into the primary cavity (40) to form a preform (125); and (iii) drawing the second optical fiber (130) from the preform (125); wherein, the second optical fiber (130) includes a core region comprising material that has been drawn from the first optical fiber (110).

Abstract: A photonic crystal fiber comprising a bulk material having an arrangement of longitudinal holes, the fiber including a cladding region and a guiding core (280), the cladding region having an effective-refractive-index which varies across the fiber's cross section, wherein, in use, the effective-refractive-index variation causes light propagating in the fiber to have a different transverse profile from the profile that it would have if the cladding region were of a substantially uniform effective refractive index.

Abstract: A photonic crystal fiber comprising a bulk material having an arrangement of longitudinal holes (130, 140) and a guiding core (135), wherein the fiber has at-most-two-fold rotational symmetry about a longitudinal axis and as a result of that lack of symmetry, the fiber is birefringent.

Abstract: In a method of producing a photonic crystal fibre, a preform (300) that includes holes is formed and the preform (300) is drawn into a fibre. The method includes the step of applying a pressure differential to certain of the holes to control changes in the fibre structure during the draw.

Abstract: A photonic crystal fiber comprising: a core (20) having a refractive index; and a cladding region (10) at least substantially surrounding the core (20) and comprising a bulk material having a second refractive index that is higher that the first refractive index, the bulk material containing an arrangement of elongate, longitudinal holes that comprise hole material of a third refractive index that is lower than the first refractive index; such that an electromagnetic mode guided in the core (20) has an evanescent wave that becomes more closely confined to the vicinity of the core (20) as the wavelength of the electromagnetic mode is increased over a first range of wavelengths.

Abstract: A method of joining a first optical fibre (110) to a second optical fibre (130) comprises the steps of: (i) providing a preform element (10) comprising material defining a primary elongate cavity (40); (ii) inserting the first optical fibre (110) into the primary cavity (40) to form a preform (125); and (iii) drawing the second optical fibre (130) from the preform (125); wherein, the second optical fibre (130) includes a core region comprising material that has been drawn from the first optical fibre (110).

Abstract: A holey optical fibre for supporting propagation of light of a wavelength &lgr;,comprises a plurality of cylinders (10) each having a longitudinal axis, the cylinders (10) being separated from each other by regions of a matrix material (20) and having their longitudinal axes substantially parallel to each other. Each cylinder (10) has a diameter, in the plane perpendicular to the longitudinal axis, that is small enough for the composite material of the ensemble of cylinders and matrix material to be substantially optically homogenous in respect of light of wavelength &lgr;.

Abstract: In a method of producing a photonic crystal fibre, a preform (300) that includes holes is formed and the preform (300) is drawn into a fibre. The method includes the step of applying a pressure differential to certain of the holes to control changes in the fibre structure during the draw.

Abstract: A photonic crystal fiber including a plurality of longitudinal holes (220), in which at least some of the holes have a different cross-sectional area in a first region (200) of the fiber, that region having been heat-treated after fabrication of the fiber, from their cross-sectional area in a second region of the fiber (190), wherein the optical properties of the fiber in the heat-treated region (200) are altered by virtue of the change in cross-sectional area of holes (230) in that region (200).

Abstract: A photonic-crystal fibre comprises a core (20) and a cladding (10) with longitudinal holes. The refractive index of the core is lower than that of the cladding bulk material, e.g. by fluorine doping of the core material. The holes are air-filled cavities extending along the longitudinal direction of the fibre. One property of the fibre is that a guided mode having longer wavelength is more confined in the core than a mode with a shorter wavelength. Such a fibre may have a cut-off wavelength &lgr;c? such that the fibre is unable to guide in its core light of wavelengths shorter than &lgr;c.

Abstract: A photonic crystal fibre comprising a bulk material having an arrangement of longitudinal holes, the fibre including a cladding region and a guiding core (280), the cladding region having an effective-refractive-index which varies across the fibre's cross section, wherein, in use, the effective-refractive-index variation causes light propagating in the fibre to have a different transverse profile from the profile that it would have if the cladding region were of a substantially uniform effective refractive index.

Abstract: An optical device comprises an optical fiber directional coupler having at least a first optical fiber optionally coupled at a coupling region to a second optical fiber such that light can propagate in the coupling region in at least two possible electromagnetic transmission modes; and means for transferring energy between the modes by a spatially periodic perturbation of at least a part of coupling region.