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: A method for making an optical fiber fusion joint between two dissimilar single mode optical fibers (10,40) where the fibers have different core sizes and/or different refractive index profiles due to different patterns of dopant. One fiber may be a standard step-index communication fiber with a 9 &mgr;m core diameter and a numerical aperture (NA) of about 0.1, and the second fiber may be a dispersion compensating fiber (DCF) with a multiple layer refractive index profile. The second fiber alternatively may have a smaller core and a higher NA, up to about 0.3. A diffused dopant region, with a gradual longitudinal variation in diffusion, is included adjacent to the splice. The diameter of the communications fiber core increases gradually within the diffusion region as the splice joint is approached along this fiber. The diffusion of the various dopants in the second fiber tend to cause its refractive index profile to converge optically to that of the diffused step index communication fiber.