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An optical fiber sensor based on Fabry-Pérot interferometer to measure the refractive index changes due to oxygenation level changes in hypoxic tumors for radiotherapy treatments is proposed. The sensors have an outer diameter of 220μm with a 20–30μm length air-cavity and a 30μm thickness end cap located at the tip of the sensor. The sensors are used to measure the phase change in the received optical...
We demonstrate a technique to mitigate the residual second-order non-local effects in Brillouin optical time-domain analysis (BOTDA) sensors in which the Brillouin frequency shift (BFS) profile is not uniform along the fiber. It is based on adding a wavelength modulation to the probe wave that makes it track the average BFS found along its way. Using this method we are able to inject a total probe...
We present recent developments in high temperature sensing using single material silica optical fibers. By using a single material fiber, in this case a suspended-core fiber, we avoid effects due to dopant diffusion at high temperature. This allows the measurement of temperatures up to the dilatometric softening temperature at approximately 1300°C. We demonstrate and compare high temperature sensing...
In this work, a preliminary study of the behavior of two different interferometric fiber optic sensors and two different wavelength selective fiber optic sensors is performed. A photonic cristal fiber Fabry-Pérot interferometer, a Sagnac interferometer, a commercial fiber Bragg grating (FBG) and a π-phase shifted fiber Bragg grating interrogated in a random distributed feedback fiber laser are analyzed...
A new structure sapphire fiber Fabry-Perot (F-P) high-temperature sensor based on sapphire wafer was proposed and fabricated. The sensor uses the sapphire fiber as a transmission waveguide, the sapphire wafer as an Fabry-Perot (F-P) interferometer and the new structure of "Zirconia ferrule-Zirconia tube" as the sensor fixing structure of the sensor. The reflection spectrum of the interferometer...
This paper presents a cascaded fiber interferometer sensor, which is fabricated by fusion splicing of single-mode fibers. The coupling and interference for the CFI were mathematically and experimentally studied. An equal model has been built for the CFI. Furthermore, the curvature sensitivity were explored in sensor application. The curvature sensitivity for the cascaded fiber interferometer is very...
A well-known structural health monitoring method used to detect and locate damage in civil engineering structures is vibration-based damage identification. It typically monitors the civil structure over time to spot slow or sudden changes in its natural frequencies, damping factors or modal displacements. This approach can prove very powerful, but the sensitivity of those properties to local damage...
The possibility of using polymer fiber as a refractive index sensor is presented. The sensor is based on a Fabry-Perot interferometer formed at the tip of the polymer fiber. The interference is granted due to reflections between a fiber Bragg grating and the fiber end-face. The sensor was characterized to refractive index changes at constant temperature using a fast Fourier transform analysis of the...
The extrusion nozzles of three low cost desktop 3D printers are characterised using optical fibre Bragg gratings. Temperature profiles show remarkably consistent distributions pointing to operation as good quality micro-furnaces potentially not only for 3D printing but also optical fibre drawing.
We report on the femtosecond laser inscription of a fibre Bragg grating array in multimode, gradient-index, CYTOP polymer optical fibre and its demonstration as a quasi-distributed sensor for cantilever health monitoring measurements. We exploit the key advantage of polymer optical fibres, having a significantly lower Young's modulus compared with silica fibres, for vibration measurements. We also...
Bridge shape is the important indicator to estimate the safety of the bridge. A bridge shape measurement system based on fiber optic gyroscope is builded up to survey the continuous shape of bridge. This measurement system comprises angular velocity sensor, linear velocity sensor, position sensor and etc. The bridge shape survey using the leveling measurement and bridge continuous shape measurement...
Polymer optical fibers (POF) have higher strain limits, fracture toughness and flexibility in bend if compared to glass optical fibers. These characteristics enable the application of POFs as curvature sensors. However, the polymer is a viscoelastic material, which does not have a constant response with stress or strain. For this reason, a curvature sensor based on POF may present high hysteresis...
We describe the fabrication and performance of a continuously grated twisted multicore fiber sensor array. The grated fiber sensor comprises nearly continuous Bragg gratings along its entire length. The gratings are inscribed over lengths in excess of 10m in fibers with UV transparent coating using a flexible and scalable reel to reel processing system. The arrays are tested using optical frequency...
An inline intermodal no core fiber (NCF) sensor based on direct ligand immobilization for detection of nickel ions (Ni2+) is proposed. Covalently immobilized nickel specific ligand, Meso-Tetra(4-carboxyphenyl)porphine, on the NCF surface serves as adsorption site for Ni2+ and can induce ambient refractive index (RI) change around the NCF on occurrence of binding events. The change in RI results in...
A new type of photodetector with an optical sensor is presented, which enables it to operate even in the presence of strong electro-magnetic interference. The optical sensor head consists of cascaded Fabry-Perot etalons coated with a new type of photo-thermal coating comprising of hydrogel-embedded copper-oxide micro-particles. For white-light irradiation, the photodetector exhibits a power sensitivity...
We demonstrate operation of an interferometric optical gyroscope that uses an on-chip 3m ultra-low-loss silicon nitride waveguide coil. The measured minimum waveguide loss of the waveguide coil fabricated using lithographic die stitching was 0.78 dB/m. The angle random walk and bias instability of the gyroscope were characterized to be 8.52 deg/hr1/2 and 58.7 deg/hr respectively.
A Brillouin optical correlation domain analysis (BOCDA) system using time-domain data processing for concurrently interrogating a plurality of sensing positions is proposed, where the time-domain data processing combined with differential measurement effectively enhances the measurement range and measurement time as much as the spatial resolution of the BOCDA system. In the experiment, the distribution...
A fiber-optic micro-electromechanical systems (MEMS) extrinsic Fabry-Perot interferometer (EFPI) pressure sensor exploiting microwave photonics filtering technique is firstly proposed and experimentally demonstrated. A single-bandpass microwave photonic filter (MPF) which mainly consists of a spectrum-sliced light source, a pressurized EFPI, a phase modulator (PM) and a length of dispersion compensating...
Radiation effects on the performances of TW-COTDR (Tunable Wavelength — Coherent Optical Time Domain Reflectometry) optical fiber sensors based on Rayleigh scattering have been studied online for Ge-doped and F-doped fibers. We confirm that the Rayleigh response is not affected by low radiation (dose ∼55 kGy). However we observed using the TW-COTDR technology, a radiation induced frequency shift increasing...
Defects in optical fibers can cause severe damage, and thus must be found and repaired/replaced early. Such defects in fibers and their coatings can be detected using an angle-resolved interrogator that exploits the contribution of different ray groups. This approach can also estimate the radial position of defects within the fiber. A demonstration is performed with a femtosecond-laser-induced internal...
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