Ultrathin 25μm optical fibers with FBG sensors are manufactured and used as vibration sensors in glass-fiber reinforced composites. The use of ultrathin fibers is discussed, and their manufacture is described. © 2022 The Authors.

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.

Draw tower fabrication of a novel optical fibre with nanocomposite polymer coating is reported. Preliminary results show it is more robust to high-temperature ageing, and moisture-induced strain than standard polymer fibres when used for distributed sensing. 

The optical fibre coating is essential to ensure high performance and reliability of the optical fibre. Out of all polymer-coated fibres, polyimide coatings provide the highest temperature rating, typically rated for use in optical fibre sensing applications at 300˚C (in air), with short excursion to 350˚C. In this communication, we assess whether the inclusion of graphene-based nanoparticles, such as graphene and graphene oxide, in a polyimide coating can enhance the durability of optical fibres at high temperatures. Draw tower fabrication of optical fibres with nanocomposite polymer coating is described. Tensile strength tests, performed on aged nanocomposite-coated optical fibres, are used as an indication of their performance at harsh conditions. The results are validated and quantified by distributed temperature and humidity sensing tests performed using these fibres. The results show that this novel class of fibre is more robust to high-temperature ageing and moisture-induced strain than standard polyimide-coated fibres, when used for distributed sensing. The electrical conductivity of the nanocomposite coating is also used in a multi-sensing approach, together with distributed optical fibre sensing, to measure temperature in a reliable way using the same optical fibre. 

The cement industry is facing pressure to find technological solutions in reducing greenhouse gas emissions owing to the large amount of process emissions originating from the calcination of limestone. In this communication, an all-fibre gas monitoring system based on anti-resonant hollow-core fibres is proposed. An on-field test was performed in the harsh environment of a cement factory and it demonstrated the feasibility of using this system for low-concentration carbon dioxide and carbon monoxide monitoring in exhaust fumes

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 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.

The moisture content in concrete is a critical parameter for most of the degradation processes such as shrinkage and cracking. In this paper, we present the first kilometrerange thermo-hygrometer for monitoring the concrete curing. © 2022 The Author(s).

Fibre optics sensors have been identified as very good candidates for environmental monitoring inside the silicon detectors operated at CERN's Large Hadron Collider. In this study, we present the results from the first highly sensitive relative humidity distributed sensor with kilometres sensing range. The setup is a 70 cm spatial resolution phase-sensitive Optical Time Domain Reflectometry (OTDR) and is able to monitor fibre lengths up to 10 km. The coating effect is also evaluated, analysing different coating thicknesses, number of coating layers, different manufacturing and different materials. Relative humidity tests were performed at two different temperatures (25°C and 42°C). Polyimide coated fibres show in general a higher humidity sensitivity then a standard acrylate coated fibre, while acrylate fibres offer the fastest response and settling time. The system is able to resolve 0.1% RH and all tested fibres proved to be good candidates to be employed in a distributed relative humidity sensor. If the requirements are a fast time response and short settling time at room temperature, the standard acrylate coated fibres are the best candidates. However, if the requirements are high sensitivity and measurement stability at different temperatures, the polyimide-coated fibres offer advantages on several aspects.

An all-fiber setup to store and retrieve light pulses using electric control is presented. The experiment is based on a Sagnac interferometer with a phase modulator fabricated using a poled fiber with internal electrodes.