Abstract-Long period gratings (LPGs) were written into a D-shaped single-mode fiber. These LPGs were subjected to a range of curvatures, and it was found that as curvature increased, there was increasingly strong coupling to certain higher order cladding modes without the usual splitting of the LPGs stopbands. A bend-induced stopband yielded a spectral sensitivity of 12.55 nm m for curvature and 2 2 10 2 nm C 1 for temperature. It was also found that the wavelength separation between adjacent bend-induced stopbands varied linearly as a function of curvature. Blue and red wavelength shifts of the stopbands were observed as the sensor was rotated around a fixed axis for a given curvature; thus, in principle, this sensor could be used to obtain bending and orientational information. The behavior of the stopbands was successfully modeled using a finite element approach.Index Terms-Curvature measurement, D-shaped optical fiber, long-period fiber gratings, optical fiber devices, temperature measurement.

We present the implementation of optical load sensors utilizing mechanically induced reversible sampled fiber Bragg gratings (SFBGs). The load is measured by the reflectivity of the first-order Fourier component of the induced SFBGs. The theoretical and experimental characterization indicates that such SFBGs can be tailored to realize load sensors with high sensitivity of near-linear response and free of influence from environmental and system noises.

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A novel sensor is demonstrated to allow a real-time measurement of the physical wear applied to the surface of an object. Two different measurement methods are presented, both utilizing the reflected power from a sacrificial chirped fibre Bragg grating to give the wear measurement. The measurement systems are simple to implement with the possibility of low cost designs depending on the application. The sensor can measure wear with a resolution of 120 µm.