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.
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.
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.
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.
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.
Nowadays, space-borne differential absorption lidar (DIAL) instruments are under investigation by space agencies to monitor the integrated column density or the atmospheric density profile of gaseous species from space to ground.
Chirped-pulse phase-sensitive optical time domain reflectometry has shown a remarkable performance when applied to dynamic measurements of strain and temperature, recently reaching ranges of several kilometers while interrogating the fiber at acoustic frequencies. In this work, its sensitivity, fast response, and high spatial resolution are exploited to implement a proof-of-concept of a selective distributed chemical sensor based on the photothermal effect. The presented scheme is able to perform distributed spectroscopic measurements of acetylene presence along a 10 m-long holey fiber. This potentially gives rise to a new kind of distributed chemical sensors capable of tracking the concentration of chemical species over kilometres.
A spider uses up to seven different types of silk, all having specific functions, to build its web. For scientists, native silk - directly extracted from spiders - is a tough, biodegradable and biocompatible thread used mainly for tissue engineering and textile applications. Blessed with outstanding optical properties, this protein strand can also be used as an optical fibre and is, moreover, intrinsically sensitive to chemical compounds. In this communication, a pioneering proof-of-concept experiment using spider silk, in its pristine condition, as a new type of fibre-optic relative humidity sensor will be demonstrated and its potential for future applications discussed.
In this communication, a novel compact fibre Bragg grating-based thermometer for on-line temperature monitoring of drill bits is reported. Our proposed technique can potentially be used to optimize any drilling process, requiring the use of small drill bits, through direct temperature measurement at the drill bit instead of relying on indirect parameters (speed of rotation, applied force) in order to avoid an overheating as it is currently done nowadays.
Whilst being thoroughly used in the textile industry and biomedical sector, silk has not yet been exploited for fibre optics-based sensing although silk fibres directly obtained from spiders can guide light and have shown early promises to being sensitive to some solvents. In this communication, a pioneering optical fibre sensor based on spider silk is reported, demonstrating for the first time the use of spider silk as an optical fibre sensor to detect polar solvents such as water, ammonia and acetic acid.
We report for the first time a multiplexed array of 12 distributed feedback fiber lasers (DFB FLs) on a single
optical fiber, separated by only 100 GHz (0.8 nm) in the C-band. These lasers are pumped by a 200 mW laser
diode at 1480 nm with no apparent impact on the sensor noise floor despite the fact that the residual reflections
from adjacent gratings may be enhanced due to the smaller wavelength separation. Each DFB FL, especially
developed for serial multiplexing, exhibits low lasing threshold typically between 1 and 2 mW, low intensity
noise and very low frequency noise (less than 30 dB re 1 Hz2/Hz at 1 kHz from optical carrier). From these
experimental results, extension to 32 DFB FLs array (on 100 GHz ITU grid) multiplexed on one fiber will be
discussed.
In this paper, an all-fiber Brillouin laser ring cavity using a 3-m-long suspended-core chalcogenide As38Se62 fiber
is reported for the first time to our knowledge. For a nonresonant ring cavity with no servo-locking, a laser
threshold power of 37 mW and an efficiency of 26 % were obtained for a fiber having a core diameter of 5 μm.
The linewidth of the Brillouin fiber laser and the pump laser were respectively measured to be below 4 kHz,
the resolution of our autocorrelator, and 250 kHz, thus showing the linewidth-narrowing nature of the Brillouin
laser. This result paves the way to compact Brillouin lasers with low threshold power and good spectral purity.
A full experimental Brillouin characterization is also reported. We measured a Brillouin gain spectrum of 14.2
MHz, a Brillouin gain coefficient of 5.6x10-9 m/W and a Brillouin frequency shift of 7.95 GHz in our fiber.
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