The voice is the main means of communication for human beings. If, due to the presence of a pathology, the voice is negatively influenced, their dayto- day life is affected. It is estimated that around 10% of the population has some speech pathology which, with an early detection, can be treated. Therefore, this work aimed to develop photonic solutions to evaluate parameters related to voice. For this, the work started with a brief introduction to the anatomy and physiology of the vocal apparatus, and of the pathologies associated with the voice. Research was also carried out on the various methods used for voice assessment, with greater focus on acoustic analysis, in order to understand the different acoustic parameters and technologies used in this area of investigation, reported in the literature. After that, devices for analysis of voice parameters were designed, simulated, and developed. After the first two models, which revealed not having adequate sensitivity for the acquisition of the optical signal, a third one was developed, based on an optical fiber Bragg grating encapsulated in a flexible material, with which the work was carried out. Two versions of this model were tested, differing in the devices’ width value. The response of these last devices to the vocalization of Portuguese vowels was tested in different regions of the larynx, in a group of volunteers. From the data obtained, it was possible to identify the regions in which the sensors had the best performance for signal acquisition. The results of the acoustic parameters, namely the fundamental frequency, Shimmer, and Jitter, obtained by optical fiber-based sensors, were compared with the data acquired with the Praat software. The developed sensors, being a non-invasive and small sized, prove to be an easy-to-use solution for the fundamental frequency acquisition.

In this study, the implementation of an optical accelerometer unit based on fiber Bragg gratings, suitable to monitor structures with frequencies up to 45 Hz, is reported. The developed optical system was used to estimate the structure eigenfrequencies of a steel footbridge, with a total length of 300 m, over the Sao Pedro Creek, located at University of Aveiro Campus, in Portugal. The acceleration records measured with this solution are compared with those obtained by traditional commercial electronic devices, revealing a root-mean-square error of 2.53 x 10(-5) G.

In this paper, we propose a spectral correlation-based technique for tracking the wavelength shift of a fiber Bragg grating. We compared this approach, by means of a Monte Carlo numerical simulation, to the typical peak tracking techniques applied in classic interrogation systems. As result, we obtained a considerable gain in terms of noise tolerance (about 20 dB), which can be further incremented by selecting large-bandwidth gratings. This permits to increase the power budget of a fiber Bragg grating interrogator without changing the optical layout, overcoming classical limitations of commercial and custom systems. Penalties due to the non-idealities have been evaluated through the same Monte Carlo approach. Finally, we discuss a practical application of the peak tracking techniques to a fiber Bragg grating-based weight sensor, in which we applied the spectral correlation to track both the Bragg wavelength position, spectral deformations due to high strain, and spectral non-linearity.

This paper presents a photonic system based on Fiber Bragg Gratings (FBGs) for application to wearable garments. The objective is spanning the FBGs over the whole area of the garments for acting as sensing elements. The FBGs are embedded on a polychloroethanediyl (polyvinyl chloride, commonly abbreviated as PVC) carrier in order to increase their sensitivity to strains and for improving the simultaneous acquisition of respiratory and cardiac frequencies with only one FBG sensor. The global structure comprising FBGs and carrier allow high strain cycles and at the same time present linear behavior with the temperature, 17 pm º C -1. The measurements show a stable structure for temperatures up to 100 º C. This brings excellent perspectives for measuring the temperature with high accuracy and range. A set of tests were done by subjecting the FBG/carrier structure (with FBG stretched and no curves) to strains up to 1.2 mm, and it was also observed a linear behaviour: e.g., displacements of 0.8 pm εμ-¹. Behind its sensing enhancement operation, the carrier makes easy to mount the sensing structures.

Electronic products, including sensors, are often used in harsh environments. However, many parameters, such as severe weather conditions, high electronic noise, or dangerous chemical compounds in situ, may compromise the required high reliability. Therefore, development of a reliable sensing solution for monitoring those extreme conditions may become a very challenging task. This paper presents a smart skin foil developed to meet this specific need. Fiber Bragg grating sensors, one of the most reliable sensor solutions nowadays, were embedded in a thin foil made of polyvinyl chloride, giving rise to a smart structure with high durability and high resistance, and a dimensional stability above 99%. In addition, the fabrication processes used are based on a technology that allows the development of large sensing areas. The sensing foil shows a linear stretching profile, with a slope of 7.8 nm per 1% elongation. After submitting the developed structure to temperature cycles, it revealed a thermal behavior of 0.1 nm/°C. Since the smart sensing structure was fabricated using available industrial fabrication processes, it is a feasible and ready-to-market solution.