Fiber Bragg Gratings (FBGs) were used to monitor the manufacturing process and the operation of high voltage bushings. During operation, temperatures at several points inside the bushing were monitored. In another test, during bushing manufacturing, FBGs monitored the filling and curing process of the epoxy in Resin Impregnated Paper (RIP) bushings. Traditionally, temperature measurements inside the bushing core have been performed using thermocouple probes and only in bushings for research, not final products. The use of appropriate FBGs was successfully tested in the harsh environments of operation (under high voltage) as well as in manufacturing (high curing temperature and stress). The results demonstrate the potential of fiber optics to study and improve production methods. The study also shows that fiber optics are suitable for long-term monitoring during bushing operation.

Windows are essential to let natural daylight into our buildings. Smart and dynamic glazing is an important technology for achieving sustainable and energy-efficient buildings with good indoor environment by reducing the need for air-conditioning. Electrochromic glazing is the commercial state-of-the-art for smart and dynamic glazing. In principle electrochromic glazing works like a thin film battery, whose lifetime is enhanced if the combination of elevated temperature and a high state-of-charge, or low light transmittance, are avoided. Therefore, a direct transmittance measurement is desirable. In this study, we have evaluated four different methods using optical fibers, whereof two methods were found to work well, both in initial testing and when compared to reference transmittance cycling measurements. Both methods relied on light from a light emitting diode, at 810 nm wavelength, that was propagated either through the electrochromic foil or along it. The latter shows most potential to be implemented in a manufacturing process of smart glazing. 

We present the design and fabrication of flexible, liquid-filled scintillating fibers for X-ray detection made from silica fibers and silica capillaries. The scintillating fibers were characterized using ultraviolet light exposure and we also performed an experiment demonstrating X-ray detection.

Fibre-optic based sensing technologies are becoming popular in the field of geophysics since enable long range and high spatial resolution acoustic measurements. In this work, we present preliminary results obtained using quasi-distributed Fibre-Bragg grating sensing and Distributed Acoustic Sensing (DAS) to monitor seismic activities in an operational underground mine. 12 FBGs and 800 metres of fiber optic cable was installed in the tunnel lining an operational mine and recorded mine seismicity such as production blasts and a small seismic activity of magnitude 1.41 in September 2022. 

A fiber optic health-monitoring system for refractory lining in steel-making processes is presented. Its applicability as an early-warning system for lining damage is demonstrated by the results obtained in a field trial, in which 240 m of fiber was embedded in the lining of an electric arc furnace. The system is based on Raman distributed sensing and polyimide coated fibers in metal tube. The results presented from temperature cycling and calibration at temperatures up to 600 °C show that adequate accuracy and stability for the application can be attained.

We present early design and simulation work on a novel X-ray imaging detector. The intent of the FleX-RAY project is to create a digital X-ray detector that is capable of producing high-resolution images, is flexible enough to produce an image on a curved surface, and is capable of self-reporting its final shape. The X-rays will be detected on a sheet of scintillating optical fibers, which will guide the scintillation light to single-photon avalanche photodiodes. This setup allows the electronics and hardware to be moved out of the path of the X-ray beam, limiting the need for additional shielding. Self-shape-reporting will be achieved using a flexible ultra-thin glass substrate with optical waveguides and Bragg gratings, processed by femtosecond laser point-by-point writing. The functionalized glass substrate allows precise measurement of strains, which can be used to calculate the shape. © 2022 The Author(s).

This work presents an on-field validation of an in-house built real-Time phase-OTDR for monitoring the status of roller bearings. The acoustic sensor prototype was designed and assembled at RISE and evaluated on a 1 m diameter bearing at SKF AB facilities in Göteborg, Sweden. A 0.24 numerical aperture single-mode optical fiber was installed in the bearing lubrication groove, which is 50 mm large and 5 mm deep. Tests were performed to verify the response of the phaseOTDR to acoustic emissions in the bearing such as hammer hits and running the rollers at different loads. The fiber optic sensor results agree with the measurements performed by a standard industrial high sensitivity electronic accelerometer used for comparison. Moreover, as opposed to the reference electronic sensor, the phase-OTDR proved to be insensitive to electrical disturbances present on the environment.

Lightweight Production Technology (LWPT) is today a well-established technology in the automotive industry. By introducing light weight fixtures manufactured from Carbon Fiber Reinforced Plastics (CFRP) in aeronautical applications, new challenges as well as possibilities of in-situ health monitoring emerges. The present paper present results from experimental investigations using optical fibers with multiplex Bragg gratings (FBG) as strain gauges in an industrial CFRP fixture. Fixtures were manufactured of laminates made from CFRP. Measurements have been performed on a single CFRP beam with dimensions (8000 × 500 × 500 mm), used as a structural part in a larger assembly (9000 × 4000mm). The optical fibers were placed in between two laminates on two sides of the beam. The measurement data from the FBGs were compared and correlated to the measured displacements of the beam and the applied loads. The results show that for an eight meter long CFRP beam, it is possible to measure and detect displacements of 0.12 mm (load = 36kg), and resolve a displacement of 0.02 mm (Δload = 4.75kg). The experimental results were also compared to FEM calculations on the displacement of the beams when subject to the same load. Here measurements and calculations showed very good agreement. Overall the results imply that FBGs show a high potential as a suitable in-situ health monitoring of lightweight fixtures for the aeronautic industry as well as other applications.

The steady progress in photonic components in terms of cost-to-performance ratio, maturity and robustness opens new avenues for the commercial deployment of photonic sensor systems in a wide range of industrial applications. Advanced sensing can be used to optimize complex processes and thereby enable significant savings in energy consumption. Three cases of robust photonic instrumentation for process optimization and quality control in manufacturing industries are presented: improved metal recycling with laser-induced breakdown spectroscopy, quality control in precision machining by white-light interferometry with optical fiber probes embedded in machining tools, and process optimization in steel foundries by stand-off temperature measurements in blast furnaces with optical fiber lances and spectral analysis techniques. Each of these methods utilizes a low-cost spectrometer, and requires dedicated calibration and signal processing methods to guarantee robust operation in industrial environments with varying conditions. Experimental results are presented, including on-line steel alloy analysis with correct classification rates in excess of 95%, distance measurements with axial resolution of +/- 2nm over a 75μm range, and continuous temperature monitoring of molten steel in oxygen blast furnaces with temperature measurement accuracy better than 1%.