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: To form an optical element (20), in particular an interferometric sensor, an optical fiber (1) is placed tangent to a cylindrical supporting element (2); a straight portion (1a) of the optical fiber and the supporting element are surface fused; and a cavity (26) is formed in the optical fiber (1), the cavity being defined by facing surfaces (27,28) of the straight portion (1a) substantially perpendicular to the axis of the straight portion (1a). The optical fiber (1) and supporting element (2) 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.