European Atomic Energy Community (Euratom)

European Community Represented by Commission of the European Communities

Robert Patrick Kenny

Alfredo Carlo Lucia

Maurice Whelan

John Sheridan

Conleth Dennis Hussey

Paul F O'Sullivan

Elaine M O'Brien

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.

Fiberoptic coupler sensor and a measurement method

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.

Strain sensor with optical fibre Bragg gratings

To form an optical element ( ), in particular an interferometric sensor, an optical fiber ( ) is placed tangent to a cylindrical supporting element ( ); a straight portion ( ) of the optical fiber and the supporting element are surface fused; and a cavity ( ) is formed in the optical fiber ( ), the cavity being defined by facing surfaces ( ) of the straight portion ( ) substantially perpendicular to the axis of the straight portion ( ). The optical fiber ( ) and supporting element ( ) may be subjected to traction during surface fusion, to form a small cross-section portion close to the cavity, and which, when light is conducted by the optical element, provides for reducing the amount of light dispersed in the cavity.

Method of producing an optical fibre resonant cavity, in particular for an interferometric sensor, and optical fibre resonant cavity produced thereby

A luminous intensity sensor element having a flat disk-shaped element ( ) made of material with a high thermal expansion coefficient and of low thermal conductivity, and in turn having, on opposite faces ( ), an optically absorbent layer ( ) and a reflecting layer ( ). On receiving excitation radiation (R), the optically absorbent layer ( ) is heated and transmits heat to the flat disk-shaped ( ), which in turn is heated internally in spatially nonuniform manner and is deformed together with the superimposed reflecting layer ( ). The reflecting layer ( ) receives an incident reference layer beam (S) to generate a reflected light beam having optical characteristics (&Dgr;&phgr;) depending on the aforementioned deformation (&Dgr;d) and varying in response to the excitation radiation.

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Ispra, Italy

Robert Patrick Kenny