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: An optical fiber bend sensor (10) measures the degree and orientation of bending present in a sensor length (30) portion of a fiber assembly (26). Within a multicored fiber (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: An optical fiber bend sensor (10) measures the degree and orientation of bending present in a sensor length (30) portion of a fiber assembly (26). Within a multicored fiber (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: An optical fiber for transmitting radiation comprising two or more core regions, two or more core regions, each core region comprising a substantially transparent core material and having a core refractive index, a core length, and a core diameter, wherein said core regions are arranged within a cladding region, said cladding region comprising a length of first substantially transparent cladding material, having a first refractive index, wherein said first substantially transparent cladding material has an array of lengths of a second cladding material embedded along its length, wherein the second cladding material has a second refractive index which is less than said first refractive index, such that radiation input to said fiber propagates along at least one of said core regions. The cladding region and the core regions may be arranged such that radiation input to said optical fiber propagates along one or more said lengths of said core regions in a single mode of propagation.

Abstract: A sensor system (10) incorporating an interferometer operates as an optical strain gauge. The system (10) is arranged to generate interferograms characterised by an optical path difference between light traversing a sensor arm (12) of the interferometer and light traversing a reference arm (58). Each arm incorporates a highly birefringent optical fibre (38, 58) capable of supporting light propagation at two velocities in two different polarisation modes. A first interferogram is generated between light coupled into the fast eigenmodes of each fibre and a second is generated between light coupled into the slow eigenmodes. Mean optical group delay (.tau..sub.MGD) and differential optical group delay (.tau..sub.DGD) of these interferograms are affected differently by temperature and strain and thus provide a means of discriminating between these attributes of the sensor environment. Thus simultaneous measurement of strain and temperature is achieved.