In the last decades, fiber Bragg gratings (FBGs) have become increasingly attractive to medical applications due to their unique properties such as small size, biocompatibility, immunity to electromagnetic interferences, high sensitivity and multiplexing capability. FBGs have been employed in the development of surgical tools, assistive devices, wearables, and biosensors, showing great potentialities for medical uses. This paper reviews the FBG-based measuring systems, their principle of work, and their applications in medicine and healthcare. Particular attention is given to sensing solutions for biomechanics, minimally invasive surgery, physiological monitoring, and medical biosensing. Strengths, weaknesses, open challenges, and future trends are also discussed to highlight how FBGs can meet the demands of nextgeneration medical devices and healthcare system. INDEX TERMS biomechanics, biosensing, fiber Bragg grating sensors, minimally invasive surgery, physiological monitoring.

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This paper describes a study of the influence of strain measurement uncertainty on sensing curvature and bending direction, considering one of the most widely used fiber geometries for sensing applications (7-core Multicore Fiber) with different core spacings (distance between outer cores and fiber axis). The Monte Carlo method was proposed to simulate the real measurement process and 33 simulations with 10 6 iterations were performed to determine the laws of propagation of strain measurement uncertainty in calculating curvature and bending direction. The outcomes, which show the strong influence of strain uncertainty and core spacing on the accuracy of Multicore Fiber sensors, can be used to support the design of new sensors or new fiber geometry and to predict their achievable performance.

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Optical fiber sensors are now widely recognized as extremely reliable instruments to sense strain. Optical shape sensors consist of multiple single-core optical fibers or multicore optical fibers capable of sensing bending direction and curvature by comparing the longitudinal strain of different cores in an instrumented section and reconstructing the sensor shape.This paper describes a study on the effects of core position errors on the precision of optical shape sensors when measuring strain, bending direction and curvature, and identifies the role of measured curvature and core spacing (distance between section center and external cores), considering 7, 4, and 3-core fiber geometries, three of those most widely employed for sensing applications. The Monte Carlo technique was utilized to reproduce the measurement process. Forty-five simulations, including 3•10 6 trials, were carried out for each geometry with the aim of investigating the law of uncertainty propagation.The results of the analysis, applicable to both multiple single-core fibers and multicore optical sensors equipped with distributed or quasi-distributed strain-sensors, show the effects of core position uncertainty and will be useful for new sensor designs and user options by predicting the achievable performance of these devices.

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This paper presents a novel and simple temperatureinsensitive optical tilt sensor based on a single eccentriccore fiber Bragg grating (ECFBG). By partly inserting an ECFBG into a ceramic ferrule, the reflection spectrum of the ECFBG splits into two peaks as a result of the applied tilt angle. The magnitude and direction of inclination in one-dimension can be determined by monitoring the wavelength separation between both peaks, which is inherently insensitive to temperature. The proposed tilt sensor has a good linear response within a wide dynamic range of ±45°, with a sensitivity of 0.012 nm/°, resolution of 0.83° and accuracy of 0.41°. Being free from any inherent mechanical joint/ friction, along with the advantages of a compact structure, good repeatability and low cost, the proposed sensor is highly suitable for practical engineering applications.

Summary The structural health monitoring (SHM) of existing buildings, structures, and infrastructures has become increasingly important in recent years, while the interest of the scientific community is focused on the use of new high‐performance technologies. Fiber optic sensors have become particularly attractive, thanks to their potential for monitoring strain in smart structures. The performance of this new technology depends to a large extent on the bonding technique used for its manufacture. Although the related literature has identified a correlation between some efficiency issues and the geometrical parameters of the bonding and mechanical properties of the materials adopted, the phenomenon is still not completely understood. This paper describes an in‐depth study of the geometrical and mechanical parameters that influence the efficiency of optical fiber point sensors' surface bonding by synergistically related techniques such as computational simulation, experimental tests, sensor manufacturing, and data analysis. The paper's novelty is fourfold: (1) the investigation of the strain transfer mechanism of surface‐bonded fiber optic sensors by considering, for the first time, all the parameters influencing the phenomenon through a considerable number of finite element (FE) analyses (117 three‐dimensional FE models); (2) the development of a series of bonding efficiency predictive models; (3) the design of a specific laboratory test to validate the computational outcomes; and (4) the definition of useful guidelines for effective bonding manufacturing in order to maximize the performance of these sensors when acquiring monitoring data.