Abstract: Sensors and sensing apparatus are described, based on fused tapered fiber optic couplers with the taper waist portion formed into a loop or cleaved to provide a reflecting end. Light is typically input to the taper waist portion along a single input fiber, and bending of the loop or cleaved taper waist portion causes changes in the coupling ratio between the output fibers. The taper waist portion may be formed into a loop with a small bend radius without loss, and sensors embodying the claimed invention are particularly suitable for in-vivo measurement of pressure, the taper waist portions advantageously being arranged in contact with a membrane which deflects according to surrounding pressure. Further embodiments are described which are suitable for measurement of fluid flow velocity and/or acceleration.

Abstract: Strain sensors, and in particular strain rosettes, are described and claimed, in which the strain sensing elements are fiber Bragg gratings. Strain sensors in accordance with the described invention comprise first and second fiber Bragg gratings, and a length of optical fiber connecting the gratings in series, each grating being substantially straight and the two gratings being non-parallel and having different nominal Bragg wavelengths, the connecting length of optical fiber having a bend, characterised in that a portion of the connecting length is tapered, the tapered portion including an elongate waist portion having a reduced cross sectional area and said bend is formed in the waist portion.

Abstract: The present invention is concerned with a fuel cell comprising: a chamber suitable for holding an electrolyte therein; a mechanism which enables rotation of the electrolyte about an axis of rotation of the chamber; one or more structures which define one or more inlets for introducing an oxidant and/or a fuel into the chamber, which one or more inlets are spaced from the axis of rotation of the chamber; at least one electrode contactable with the electrolyte and the oxidant and at least one electrode contactable with the electrolyte and the fuel. It also provides a method for improving the efficiency and performance of fuel cells.