Integration Of Fiber Optic Sensors Research Articles

Distributed fiber optic sensors for structural health monitoring of composite pressure vessels

Abstract In this paper, we present a comprehensive overview of our research in the field of distributed fiber optic sensors for structural health monitoring of hydrogen composite pressure vessels. Specifically, we demonstrate how the integration of fiber optic sensors into composite pressure vessels enhances safety while simultaneously reducing maintenance costs. The small size of optical fibers enables their integration into composite structures during the manufacturing process, allowing continuous monitoring and precise detection and localization of structural damages during service life. We also discuss the potential of state-of-the-art signal processing methods and machine learning for advancing predictive maintenance. Our applications of fiber optic sensors demonstrate their potential to contribute significantly to the energy transition towards renewable sources.

Integrating fiber optic sensors into metallic components for sensing in harsh environments

The integration of fiber optic sensors into high-temperature materials is critical for real-time monitoring and autonomous operation of engineering systems. This study demonstrated a spark plasma sintering (SPS)-assisted embedding process for integrating sapphire fiber optic sensors into stainless steel components during part fabrication. Optical fibers were encapsulated in stainless steel 316L powders which were sintered at different fabrication conditions using SPS to investigate the effects of sintering parameters on the embedment. Measurements of optical transmittance, combined with microstructural analysis (X-ray computed tomography and scanning electron microscopy) and mechanical testing (tensile and microhardness), were conducted to examine the fiber functionality, fiber–matrix bonding quality, and properties of the sintered materials. The results show that under suitable fabrication conditions, intact optical fibers can be encapsulated in highly-densified (>98 % relative density) stainless steel components. These conditions also led to a good bond at the fiber–matrix interface with micron-sized material interdiffusion across the interface. The sintering parameters were observed to affect fiber optical attenuation, where high temperature, pressure, and hold time during SPS enhanced fiber–matrix bonding and adversely affected optical transmission. Tensile testing confirmed the superior tensile strength and ductility of the matrix fabricated by SPS. Furthermore, the materials exhibited limited strength reduction (∼70 MPa) upon the integration of fibers. This study demonstrates the effectiveness of SPS for fiber-material integration for high-temperature applications.

Temperature profile of ex-vivo organs during radio frequency thermal ablation by fiber Bragg gratings.

We report on the integration of fiber optic sensors with commercial medical instrumentation for temperature monitoring during radio frequency ablation for tumor treatment. A suitable configuration with five fiber Bragg grating sensors bonded to a bipolar radio frequency (RF) probe has been developed to monitor the area under treatment. A series of experiments were conducted on <italic<ex-vivo</italic< animal kidney and liver and the results confirm that we were able to make a multipoint measurement and to develop a real-time temperature profile of the area, with a temperature resolution of 0.1°C and a spatial resolution of 5 mm during a series of different and consecutive RF discharges.

Fiber Bragg Grating for Temperature Monitoring During Medical Radiofrequency Treatments

In this work, it is proposed the integration of fiber optic sensors with commercial medical instrumentation, for temperature monitoring during tumor radiofrequency thermal ablation (RFTA) treatments. The heat propagation over the area under treatment is measured by means of a specific configuration, consisting of several Fiber Bragg Grating (FBG) sensors properly bounded to the RFTA probe and being positioned close to the region reached by RF electrodes. Our ex-vivo experiments on ex vivo animal liver and kidney, confirm that we were able to monitor in real time the temperature increase during different and consecutive RF discharges performed with the laparoscopic bipolar device Habib 4x, with a temperature resolution of 0.1̊C and a spatial resolution of 5mm.

Integration Methods of Sensors in FRP Components

Structural health monitoring is an important research topic in the field of fiber reinforced plastics (FRP). An effective way to detect defects or overloads in these FRP has still not been found. One way to monitor the actual state of FRP components is via integrated sensors. Integrating current standard sensors negatively affects the flux of force. Therefore investigations about integration methods of sensors in FRP components have been made. The integration of an optical fiber sensor into FRP profiles via a pultrusion process was investigated. It could be shown that the pultrusion process is suitable method for the integration of fiber optic sensors for strain measurements. Another investigated sensor principle was the integration of piezoelectric polyvinylidene fluoride (PVDF) fibers via a vacuum assisted process. The PVDF fibers were integrated into 3-point bending specimen and the piezoelectric effect was tested with and without polarization. The investigation showed that it is possible to measure the piezoelectric effect of PVDF fibers integrated into a 3-point bending test specimen. It could also be shown that carbon fibers can be used as textile electrodes for the measurement of the generated charge on the PVDF surface.

Integration of fiber-optic sensors in measuring machines

In last years, optical metrology due to its capability in miniaturization and sensitivity became the primary solution in measurement of complex geometries and fragile pieces. Here, we propose a promising approach to perform highly accurate distance measurements using low-coherence fiber-optic sensors for quality inspection of nozzle orifices in fuel injection systems. In this effort, we develop an adaptive image processing algorithm in MATLAB and install the necessary hardware on a form tester to accelerate and simplify the aligning process. As a result, the repeatability of measurements is one order of magnitude improved while the standard deviation is almost 60% reduced.