Fiber Bragg Grating Based Sensors and Systems

This book is a collection of papers that originated as a Special Issue, focused on some recent advances related to fiber Bragg grating-based sensors and systems. Conventionally, this book can be divided into three parts: intelligent systems, new types of sensors, and original interrogators. The intelligent systems presented include evaluation of strain transition properties between cast-in FBGs and cast aluminum during uniaxial straining, multi-point strain measurements on a containment vessel, damage detection methods based on long-gauge FBG for highway bridges, evaluation of a coupled sequential approach for rotorcraft landing simulation, wearable hand modules and real-time tracking algorithms for measuring finger joint angles of different hand sizes, and glaze icing detection of 110 kV composite insulators. New types of sensors are reflected in multi-addressed fiber Bragg structures for microwave–photonic sensor systems, its applications in load-sensing wheel hub bearings, and more complex influence in problems of generation of vortex optical beams based on chiral fiber-optic periodic structures. Original interrogators include research in optical designs with curved detectors for FBG interrogation monitors; demonstration of a filterless, multi-point, and temperature-independent FBG dynamical demodulator using pulse-width modulation; and dual wavelength differential detection of FBG sensors with a pulsed DFB laser

Optimizing Linearity and Sensitivity of 3D-Printed Diaphragms with Chirped FBGs in CYTOP Fibers

We report the development of an optimization approach for diaphragm-embedded optical fiber sensors, which was applied on the pressure, force and liquid level assessment using chirped fiber Bragg gratings (CFBGs) inscribed in cyclic transparent optical polymer (CYTOP) fibers. The inscription was performed using the plane-by-plane method with a femtosecond laser, whereas the diaphragm optimization was performed through the multi-objective particle swarm optimization (MOPSO). The objective functions for the optimization were obtained from numerical simulation using the finite element method of diaphragms with different thickness and diameters. The MOPSO resulted in a set of solutions with thickness and diameter aiming the optimization of sensitivity and linearity of diaphragm-embedded CFBG sensors. Three configurations were chosen with different values sensitivity and linearity. Experimental analysis was performed in each configuration for temperature and pressure variations, where the results confirmed the different sensitivity and linearity levels for each chosen configuration. Two applications were analyzed for the proposed configurations with higher sensitivity and linearity: one for force estimation over a 200-N range and the other for sub-millimeter assessment of liquid level over a 50-cm range. In order to obtain a highly reliable and accurate system, a novel data integration method for chirped FBGs was proposed. In this case, the estimation of force, pressure or liquid level was performed considering the contributions of both wavelength shift and full width half maximum (FWHM) variations. The proposed approach resulted in error improvement of 60% for all cases and for all parameters analyzed