We investigate the changes in the transmission spectrum of long period fibre gratings and tilted short-period fibre Bragg gratings versus the refractive index of the surrounding medium. The metrological characteristics of tilted short-period fibre Bragg gratings and an analytical method enabling their potential use in accurate refractometry are discussed.

We present a study aimed at developing a label-free optical fiber biosensor for detection and quantification of biomolecules in real-time. The biosensor based on a Tilted Fiber Bragg Grating (TFBG) transduces a binding event between the probe and target molecules into a change in the refractive index of the medium surrounding the fiber. This work describes the experimental results obtained with three methods for immobilizing biomolecular probes on a TFBG silica cladding surface. Bovine serum albumin (BSA) and anti-BSA are used to assess the performances of the TFBG based biosensor in each configuration.

We present a photosensitive three-hole microstructured optical fiber specifically designed to improve the refractive index sensitivity of a standard fiber Bragg grating (FBG) sensor photowritten in the suspended Ge-doped silica core. We describe the specific photowriting procedure used to realize gratings in such a fiber. We then determine their spectral sensitivity to the refractive index changes of material filling the holes surrounding the core. The sensitivity is compared with that of standard FBGs photowritten in a six-hole fiber with a larger core diameter. We demonstrate an improvement in the sensitivity by two orders of magnitude and reach a resolution of 3 x 10(-5) and 6 x 10(-6) around mean refractive index values of 1.33 and 1.40, respectively.

An embedded Fiber Bragg Grating (FBG) strain sensor and an FBG temperature sensor have been shown to be able to accurately monitor the industrial composite cure process of a glass/ epoxy plate devoted to aeronautical applications. The internal absolute strain level in the plate was determined, free of temperature effect thanks to a differential method. After curing, a residual compression strain of about -0.22% was observed, which represents a short part of the range in compression for a single mode fiber. Later on, the embedded FBG strain sensor could be used as a smart sensor for the health monitoring of composite structures, e.g. for impact or layer delamination detection.