Force sensing is a key enabler for getting haptic feedback, useful in a variety of applications, especially in the fields of robotics, automation, and health. Indeed, equipping machines, vehicles, robots, and even humans with force sensors provides controlled processes and production, safe and enhanced external interaction, and capability to perform efficient manipulation and precise movements. Aiming to develop an alternative solution to electrical force sensors, in this work a fiber Bragg grating (FBG) is embedded inside a patch made of silicone rubber. Such embedding strategy allows to make the FBG sensitive to the force variations, obtain a flexible patch having a moldable shape, and protect the most fragile areas of the optical fiber. Moreover, thanks to its high flexibility and stretchability, the sensing patch can be easily employed as portable and wearable device. Besides reporting fabrication process and results of the performed force tests, this work provides a systematic study of the FBG embedding in silicone matrix. Indeed, for this purpose, three sensing patches having different thickness are developed and tested in temperature, strain, and force, finding that the patch thickness influences the sensing performances of the device. The resulting force sensitivity varies in the range from 9.2 pm/N to 19.0 pm/N, based on the sensor thickness. Temperature sensitivity, instead, is comparable with respect to bare FBGs, while strain sensitivity is enormously reduced, obtaining a patch able to insulate the FBG from the strain variations.

This work reports on the use of Fiber Bragg Grating (FBG) sensors integrated with innovative composite items of aircraft landing gear for strain/stress monitoring. Recently, the introduction of innovative structures in aeronautical applications is appealing with two main goals: (i) to decrease the weight and cost of current items; and (ii) to increase the mechanical resistance, if possible. However, the introduction of novel structures in the aeronautical field demands experimentation and certification regarding their mechanical resistance. In this work, we successfully investigate the possibility to use Fiber Bragg Grating sensors for the structural health monitoring of innovative composite items for the landing gear. Several FBG strain sensors have been integrated in different locations of the composite item including region with high bending radius. To optimize the localization of the FBG sensors, load condition was studied by Finite Element Method (FEM) numerical analysis. Several experimental tests have been done in range 0–70 kN by means of a hydraulic press. Obtained results are in very good agreement with the numerical ones and demonstrate the great potentialities of FBG sensor technology to be employed for remote and real-time load measurements on aircraft landing gears and to act as early warning systems.

The employability of photonics technology in the modern era’s highly demanding and sophisticated domain of aerospace and submarines has been an appealing challenge for the scientific communities. In this paper, we review our main results achieved so far on the use of optical fiber sensors for safety and security in innovative aerospace and submarine applications. In particular, recent results of in-field applications of optical fiber sensors in aircraft monitoring, from a weight and balance analysis to vehicle Structural Health Monitoring (SHM) and Landing Gear (LG) monitoring, are presented and discussed. Moreover, underwater fiber-optic hydrophones are presented from the design to marine application.

Aim of this work is the analysis of the 3D printed patches embedding fiber Bragg gratings (FBGs) for deformation monitoring. In particular, the paper first describes the manufacturing process and the performances of FBGs embedded in PLA and ABS rectangular patches, showing that the sensitivity to temperature is strongly dependent on the material and on the dimension of the patches. Then, the deformation characteristics are, for the first time, explored showing that the thickness of the patch, influencing the neutral axis position, acts as gaining factor on the deformation sensitivity of the FBG sensor. Such results enable the application of FBG embedded in 3D-printed patches for deformation monitoring taking in proper consideration the dimension of the patches, in particular its thickness, that allows to enhance the wavelength shift of the applied FBG sensors.

In this work, the advantages of 3D printing technology are combined with fiber Bragg grating (FBG) sensors to implement an innovative 3D shape sensor embedded in a 3D printed patch. The system allows to obtain a sensing patch able to provide a direct measure of curvature and neutral axis position in the 3D space in a simple manner and without requiring numerical simulations or mathematical models of the structure of interest. The experimental tests assess the proposed novel approach showing an optimal agreement between the measurements of the proposed patch with respect to the reference sensors. Furthermore, both the curvature sensitivity and resolution can be modulated by changing the distances among the FBGs inside the patch, tailoring the performances and the dimensions with the application requirements.

This article proposes a hot-wire anemometer based on optical fiber embedding an FBG and having a D-shaped transversal section on whose flat surface a thin metallic layer has been deposited. Thanks to this geometrical structure, the optical power flowing through the fiber core can achieve the metallic layer and be converted in heat. The embedded FBG can measure the resulting temperature increase and the temperature fluctuation of the D-fiber caused by the wind flowing. Numerical simulations have been performed in order to select the appropriate design parameters, such as thickness of the metallic layer and its distance from the core. Then, the fabrication process of the device and the experimental results of its characterization in temperature and wind assess its working principle. The developed sensor can work at low power levels of the source and is characterized by small size and high accuracy. Furthermore, it shows high cost-effectiveness and the possibility to modulate its wind sensitivity by setting the source power.