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: 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: Improved photonic band-gap optical fibre The present invention relates in particular to improved photonic band-gap optical fibres that can confine light to a core region of the fibre by the action of both a photonic band-gap cladding and an antiresonant core boundary, at the interface between the core and cladding.

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: Novel preforms and methods of making novel preforms are described. The preforms are suitable for being drawn into photonic bandgap optical fibres. In one form, the preform comprises a stack of elongate members having, in transverse cross section, a triangular close-packed arrangement of circular cross section capillaries, which define interstitial regions containing solid rods. The stack is supported around a relatively large capillary, which defines an inner region of the stack. The stack may be adapted by varying the number of rods in any given interstitial region, in order to generate various different configurations of cladding structure, which can be made into optical fibres having surprising operational characteristics, such as a split gap.

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 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 nonlinear optical device, comprises a source of input light having a first spectrum and an optical fibre 10 arranged so that in use the light propagates through the fibre 10, the optical fibre 10 comprises a tapered region including a waist 30, the waist 30 having a diameter smaller than 10 microns for a length of more than 20 mm, wherein the propagating light is converted by nonlinear optical processes into output light having a spectrum different from the first spectrum.

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: An optical fibre bend sensor (10) measures the degree and orientation of bending present in a sensor length (30) portion of a fibre assembly (26). Within a multicored fibre (30, 32,34), cores (62, 66) are grouped in non-coplanar pairs. An arrangement of optical elements (28, 36, 38) define within each core pair (62, 66) two optical paths (122, 124) which differ along the sensor length (30): one core (62) of a pair (62, 66) is included in the first path (122), and the other core (66) in the second path (124). A general bending of the sensor region (30) will lengthen one core (62, 66) with respect to the other. Interrogation of this length differential by means of interferometry generates interferograms from which the degree of bending in the plane of the core pair is extracted. Bend orientation can be deduced from data extracted from multiple core pairs.

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: A composite material for supporting propagation of light of a wavelength &lgr;, comprising a plurality of cylinders each having a longitudinal axis, the cylinders being separated from each other by regions of a matrix material and the cylinders having their longitudinal axes substantially parallel to each other, and each cylinder having a diameter, in the plane perpendicular to the longitudinal axis, that is small enough for the composite material to be substantially optically homogeneous in respect of light of wavelength &lgr;.