Abstract: A sensor system includes a radiation source, an optical fiber, and a detection device. The radiation source is arranged to emit pulses of radiation. The optical fiber comprises a first end and a core. The first end is arranged to receive pulses of radiation output from the radiation source such that, in use, the pulses of radiation are coupled into the fiber. The core is arranged to support propagation of the pulses of radiation along the fiber. The core includes a plurality of reflectors each comprising a portion of the core having a refractive index which is different to the refractive index of adjacent regions of the core. Reflections of a pulse of radiation from adjacent reflectors output at the first end of the fiber are resolvable from each other in the time domain. The detection device is arranged to measure radiation output from the first end of the fiber and resolve radiation reflected at different locations in the core of the fiber.

Abstract: A method of fabricating a multi-core polymer optical fibre comprises arranging optical fibre preforms in a stack, the optical fibre preforms each comprising a polymer core and polymer cladding surrounding the polymer core; and drawing and bonding the stack to form the multi-core polymer optical fibre. Any contaminants or impurities which collect on outer surfaces of the preforms may be confined to boundaries between the preforms, which may avoid attenuation of signals passed through the cores while at the same time reducing crosstalk between cores of the final manufactured fibre. Also provided is a multi-core polymer optical fibre obtainable by the method.

Abstract: A method of fabricating a graded-index polymer optical fibre comprises preparing a cladding composition, the cladding composition comprising either a mixture of a cladding polymer and a dopant or a mixture of a cladding polymer precursor and a dopant; forming cladding from the cladding composition around a core, the core comprising a core polymer; and causing diffusion of the dopant into the core such that the dopant has a continuous concentration gradient, according to which concentration gradient the concentration of the dopant increases with radial distance from a centre of the core. The dopant is a compound having a refractive index which is lower than a refractive index of the core polymer. By distributing the dopant such that the dopant concentration is lowest at the centre of the core, the optical attenuation of the graded-index polymer optical fibre may be reduced. Also provided is a graded-index polymer optical fibre obtainable by the method.

Abstract: A multi-core optical fibre comprises a plurality of cores embedded in cladding. The cladding comprises a polymer. The cladding has an outer cross-sectional shape with an order of rotational symmetry of less than or equal to 4. By limiting the rotational symmetry of the multi-core optical fibre, rotational alignment of the cores with light sources/light detectors may be made easier. Also provided are optical cables and kits including the multi-core optical fibre, and a method of fabricating a multi-core polymer optical fibre.

Abstract: A method of fabricating a multi-core polymer optical fibre comprises arranging optical fibre preforms in a stack, the optical fibre preforms each comprising a polymer core and polymer cladding surrounding the polymer core; and drawing and bonding the stack to form the multi-core polymer optical fibre. Any contaminants or impurities which collect on outer surfaces of the preforms may be confined to boundaries between the preforms, which may avoid attenuation of signals passed through the cores while at the same time reducing crosstalk between cores of the final manufactured fibre. Also provided is a multi-core polymer optical fibre obtainable by the method.

Abstract: A magnetic field sensor comprises a magnetically responsive light propagating component configured to cause a polarization of light propagating inside the component to be rotated in response to an applied magnetic field, wherein the magnetically responsive light propagating component is formed of a bulk material doped with a dopant, the dopant including at least gadolinium, the dopant concentration being at a sufficiently low concentration such that the dopant is uniformly dispersed in the bulk material to provide a high Verdet constant. The magnetic field sensor also comprises a detector, and a polarization-maintaining light input device to couple the light into the magnetically responsive light propagating component. The detector is configured to measure a property of light output from the magnetically responsive light propagating component to determine a change in polarization of the light, the change caused by the presence of a magnetic field.

Abstract: A fused fibre coupler comprising: a single mode fibre, SMF, and an orbital angular momentum fibre, OAMF, the fibres having a coupling portion in which the fibres are longitudinally aligned side by side and fused at least over a coupling length in which the SMF and OAMF are tapered such that the diameter of the SMF and the diameter of the OAMF give the fibres matching effective refractive indices for a single mode of the SMF and an orbital angular momentum, OAM, mode of the OAMF for a coupled wavelength of light.

Abstract: A sensor system includes a radiation source, an optical fiber, and a detection device. The radiation source is arranged to emit pulses of radiation. The optical fiber comprises a first end and a core. The first end is arranged to receive pulses of radiation output from the radiation source such that, in use, the pulses of radiation are coupled into the fiber. The core is arranged to support propagation of the pulses of radiation along the fiber. The core includes a plurality of reflectors each comprising a portion of the core having a refractive index which is different to the refractive index of adjacent regions of the core. Reflections of a pulse of radiation from adjacent reflectors output at the first end of the fiber are resolvable from each other in the time domain. The detection device is arranged to measure radiation output from the first end of the fiber and resolve radiation reflected at different locations in the core of the fiber.

Abstract: A magnetic field sensor comprises a magnetically responsive light propagating component configured to cause a polarization of light propagating inside the component to be rotated in response to an applied magnetic field, wherein the magnetically responsive light propagating component is formed of a bulk material doped with a dopant, the dopant including at least gadolinium, the dopant concentration being at a sufficiently low concentration such that the dopant is uniformly dispersed in the bulk material to provide a high Verdet constant. The magnetic field sensor also comprises a detector, and a polarization-maintaining light input device to couple the light into the magnetically responsive light propagating component. The detector is configured to measure a property of light output from the magnetically responsive light propagating component to determine a change in polarization of the light, the change caused by the presence of a magnetic field.

Abstract: A fused fibre coupler comprising: a single mode fibre, SMF, and an orbital angular momentum fibre, OAMF, the fibres having a coupling portion in which the fibres are longitudinally aligned side by side and fused at least over a coupling length in which the SMF and OAMF are tapered such that the diameter of the SMF and the diameter of the OAMF give the fibres matching effective refractive indices for a single mode of the SMF and an orbital angular momentum, OAM, mode of the OAMF for a coupled wavelength of light.

Abstract: Using sol-gel techniques, an optical gain medium has been fabricated comprising a glass ceramic host material that includes clusters of crystalline oxide material, especially tin oxide, and that is doped with active ions concentrated at the clusters. The active ions are preferentially located at the nanoclusters so that they experience the relatively low phonon energy of the oxide and are insensitive to the phonon energy of the host. A host with a high phonon energy, such as silica, can therefore be used without the usual drawback of reduced carrier lifetimes through enhanced nonradiative decay rates.

Abstract: Using sol-gel techniques, an optical gain medium has been fabricated comprising a glass ceramic host material that includes clusters of crystalline oxide material, especially tin oxide, and that is doped with active ions concentrated at the clusters. The active ions are preferentially located at the nanoclusters so that they experience the relatively low phonon energy of the oxide and are insensitive to the phonon energy of the host. A host with a high phonon energy, such as silica, can therefore be used without the usual drawback of reduced carrier lifetimes through enhanced nonradiative decay rates.

Abstract: Optical waveguides having a waveguide channel of photosensitive silica glass with a modified refractive index optically written therein, wherein the photosensitive glass comprises oxides of silicon, tin and at least one Group I element, where such optical waveguide devices include optical fiber gratings, optical fiber dispersion compensators, optical fiber sensors, optical fiber lasers, and planar waveguide devices.

Abstract: Using sol-gel techniques, an optical gain medium has been fabricated comprising a glass ceramic host material that includes clusters of crystalline oxide material, especially tin oxide, and that is doped with active ions concentrated at the clusters. The active ions are preferentially located at the nanoclusters so that they experience the relatively low phonon energy of the oxide and are insensitive to the phonon energy of the host. A host with a high phonon energy, such as silica, can therefore be used without the usual drawback of reduced carrier lifetimes through enhanced nonradiative decay rates.

Abstract: A photosensitive glass made of a ternary compound SiO2:SnO2:R2O where R is a Group I element such as Na, K or Li. The addition of an oxide of a Group I element increases the solubility of tin oxide in a silica matrix and produces a glass which is highly photosensitive and in which optically written refractive index modulations have remarkable temperature stability (solid circles) at least as good as that of the binary glass SiO2:SnO2 (open circles) and much superior to that of conventional germanosilicate glass (solid triangles) or borogermanosilicate glass (open triangles). The inclusion of the Group I oxide effectively increases the solubility of tin oxide in the non-crystalline silica matrix well above the 1% limit of SiO2:SnO2 photosensitive glass, at which Sn would normally crystallize in the oxide.

Abstract: A method of fabricating an optical fiber incorporating a volatile constituent, involving: (a) providing a preform comprising a cladding glass having an axial aperture and a core glass arranged in the axial aperture, wherein the working temperature of the core glass lies below the working temperature of the cladding glass; and (b) drawing the preform into an optical fiber at a drawing temperature that lies between the working temperatures of the core and cladding glasses and above the softening temperature of the cladding glass, wherein the core glass prior to drawing includes a dioxide or higher oxide compound of the volatile constituent having a Gibbs free energy of disassociation into a monoxide compound of the volatile constituent that is negative at the drawing temperature, whereby the dioxide or higher oxide compound tends to disassociate into the monoxide compound during drawing. The volatile constituent may be Sn or Pb. The method may also be adapted for incorporating P as the volatile constituent.