Applications Of Fiber Optic Sensors Research Articles

Reflectometric and interferometric fiber optic sensor’s principles and applications

Fiber optic sensors have been widely used and studied in recent times. This paper presents operating principles and applications of fiber optic sensors namely reflectometric and interferometric fiber optic sensors. Majority of optical fiber sensors fall under these two broad categories. Both interferometric and reflectometric fiber optic sensors are becoming popular for their ease of use, flexibility, long distance sensing, and potentially noise free detection. Also, these sensors can easily be used in various applications such as structural health monitoring, perimeter intrusion detection, temperature monitoring, and other numerous applications. This paper broadly classifies fiber optic sensors into two subtypes. The paper further highlights different sensors based on their sensing resolution, range, spatial advantages, and applications.

Перспективы применения волоконно-оптических датчиков физических величин в качестве средств измерения в системах обнаружения утечек

Перспективы применения волоконно-оптических датчиков физических величин в качестве средств измерения в системах обнаружения утечек

1.9 μm laser and visible light emissions in Er3+/Tm3+ co-doped tellurite glass microspheres pumped by a broadband amplified spontaneous emission source

From Er3+/Tm3+ co-doped tellurite glass microspheres, simultaneous laser oscillation at 1.9 μm, and green and red fluorescence emissions with three photons upconversion luminescence were obtained. The microsphere was pumped by a low-cost 1550 nm broadband amplified spontaneous emission source instead of a bulky and expensive tunable laser. It as a non-polarized light provided a wide wavelength range and the multiple wavelengths resonant absorption was obviously observed from the transmission spectra. The use of broadband source made the entire microsphere laser more adaptively stable to withstand the vibration interference and temperature variations. The coupled threshold power was as low as 1.5 mW. It was demonstrated that the Er3+ ions acted as sensitizers to efficiently absorb the pump photons and transfer energy to Tm3+ ions. Therefore, this approach would have potential applications in optical fiber lasers, sensors and lighting devices.

A high-quality phase modulation scheme with strong noise-suppressing capability for interferometric fiber-optic sensor applications

For practical interferometric fiber-optic sensor applications, various kinds of noise sources exist and become one of the most significant factors that deteriorate the system performance. In this paper, aiming to suppress the noise, a new low-pass-filter (LPF)-assisted rectangular-pulse binary (RPB) phase modulation method is proposed. The LPF is applied directly in the light intensity domain, but interestingly when combined with the RPB method, this can lead to very strong resistance ability to the noise in the whole frequency range as will be proved in this paper. The low-frequency-filtering is accomplished by the RPB method naturally during the phase-demodulation process. The high-frequency-filtering is accomplished by using a low-pass filter with carefully chosen cut-off frequency. Both simulations and experiments are conducted to validate the effectiveness of the new modulation method, and significant signal-to-noise ratio (SNR) improvement (7.7 dB in the experiment) is obtained.

Femtosecond Laser Microprinting of a Polymer Optical Fiber Interferometer for High-Sensitivity Temperature Measurement.

Femtosecond laser induced multi-photon polymerization technique can be applied to fabricate an ultracompact polymer optical fiber interferometer which was embedded in a section of hollow core fiber. The production of the photoresin, used in this work, is described. Such a device has been used for temperature measurement, due to its excellent thermal properties. Transmission spectrum, structural morphology, and temperature response of the polymer optical fiber interferometer are experimentally investigated. A high wavelength sensitivity of 6.5 nm/°C is achieved over a temperature range from 25 °C to 30 °C. The proposed polymer optical fiber interferometer exhibits high temperature sensitivity, excellent mechanical strength, and ultra-high integration. More complex fiber-integrated polymer function micro/nano structures produced by this technique may result in more applications in optical fiber communication and optical fiber sensors.

Selection measure of energy propagation in vibration diagnostic and modal analysis methods

1. Betz DC. Application of optical fibre sensors for structural health and usage monitoring. Dynamics Research Group, Department of Mechanical Engineering, The University of Sheffield. Sheffield 2004. Google Scholar

Polymer Optical Fiber Sensors in Wearable Devices: Toward Novel Instrumentation Approaches for Gait Assistance Devices

This paper presents the application of polymer optical fiber (POF) sensors in wearable devices for gait assistance. Intensity variation-based POF curvature sensor for the acquisition of joint angles and a POF insole based to detect gait events were developed. Three wearable devices were employed for the practical validation of the developed sensors: an active orthosis with one degree of freedom, a robotic exoskeleton, and a functional electrical stimulation (FES) system for gait assistance. POF is a viscoelastic material, which does not have a constant response to stress or strain and also can present hysteresis in dynamic measurements. In order to mitigate these effects, a compensation technique based on the polymer viscoelastic features was applied on both the curvature sensor and the instrumented insole. The results obtained for the POF curvature sensor on the knee joint angle measurement of the orthosis and the exoskeleton show root mean squared error of 3.7° and 3.8°, respectively. Regarding the POF insole results, it was used to identify five gait events in the FES system application. The reported results pave the way for new instrumentation approaches in wearable devices with flexible sensors that can be especially desirable in the rigid robots presented but also in soft robotics applications.

Sensores de fibra óptica tipo LPG aplicados a la determinación de tensiones y deformaciones en suelos

En este trabajo se muestra la aplicación de sensores de fibra óptica tipo LPG a la determinación del esfuerzo transmitido y deformación de una muestra de suelo confinado sometido a cargas superficiales. El esfuerzo transmitido fue medido por un sensor de presión LPG mecánico y la curvatura del suelo por sensores LPG permanentes enterrados a profundidades de 0,1m; 0,2m; 0,4m y 0,6m. Suelo arcilla-arenoso característico de la UNICAMP fue depositado en un cilindro de 0,8m de longitud y 0,305 m de diámetro. El suelo fue ligeramente compactado en capas de 0,2m instalándose sobre cada capa un sensor LPG. Cargas superficiales de hasta 227 KPa fueron aplicadas sobre la superficie del suelo midiéndose deformaciones axiales del suelo menores a 3mm por nuestros sensores con sensibilidades del orden de 0,22 mm/dB. Los valores de los módulos de elasticidad para este tipo de suelo fueron determinados a partir del ajuste de las ecuaciones de Bousinessq con los valores medidos por los sensores LPG enterrados. Un módulo de Young de 5,39 MPa y un coeficiente de Poisson ν=0,52 fueron determinados para este tipo de suelo.

Optical Detection of Ketoprofen by Its Electropolymerization on an Indium Tin Oxide-Coated Optical Fiber Probe.

In this work an application of optical fiber sensors for real-time optical monitoring of electrochemical deposition of ketoprofen during its anodic oxidation is discussed. The sensors were fabricated by reactive magnetron sputtering of indium tin oxide (ITO) on a 2.5 cm-long core of polymer-clad silica fibers. ITO tuned in optical properties and thickness allows for achieving a lossy-mode resonance (LMR) phenomenon and it can be simultaneously applied as an electrode in an electrochemical setup. The ITO-LMR electrode allows for optical monitoring of changes occurring at the electrode during electrochemical processing. The studies have shown that the ITO-LMR sensor’s spectral response strongly depends on electrochemical modification of its surface by ketoprofen. The effect can be applied for real-time detection of ketoprofen. The obtained sensitivities reached over 1400 nm/M (nm·mg−1·L) and 16,400 a.u./M (a.u.·mg−1·L) for resonance wavelength and transmission shifts, respectively. The proposed method is a valuable alternative for the analysis of ketoprofen within the concentration range of 0.25–250 μg mL−1, and allows for its determination at therapeutic and toxic levels. The proposed novel sensing approach provides a promising strategy for both optical and electrochemical detection of electrochemical modifications of ITO or its surface by various compounds.

Новые области применения систем волоконно-оптических датчиков

Новые области применения систем волоконно-оптических датчиков

Optical Monitoring of Electrochemical Processes With ITO-Based Lossy-Mode Resonance Optical Fiber Sensor Applied as an Electrode

In this paper, we discuss the application of optical fiber sensors based on lossy-mode resonance (LMR) phenomenon for real-time optical monitoring of electrochemical processes. The sensors were obtained by a reactive high power impulse magnetron sputtering of indium tin oxide (ITO) on a 2.5 cm long core of polymer-clad silica fibers. The LMR effect made monitoring of changes in optical properties of both ITO and its surrounding medium possible. Moreover, since ITO is electrically conductive and electrochemically active, it was used as a working electrode in a three-electrode cyclic voltammetry setup. The investigations have shown that the sensor's optical response strongly depends on the potential applied to the sensor, as well as on electrochemical modification of its surface. The obtained LMR effect can be applied in parallel to electrochemical measurements for real-time optical monitoring of the electrode conditions and properties of the surrounding medium.

全光纤电流传感器中传感光纤的温度特性研究

全光纤电流传感器中传感光纤的温度特性研究

Intensity modulated silver coated glass optical fiber refractive index sensor

Miniature optical fiber sensors with thin films as sensitive elements could open new fields for optical fiber sensor applications. Thin films work as sensitive elements and a transducer to get response and feedback from environments, in which optical fibers act as a signal carrier. A novel Ag coated intensity modulated optical fiber sensor based on refractive index changes using IR and UV-Vis (UV-visible) light sources is proposed. The sensor with an IR light source has higher sensitivity compared to a UV-Vis source. When the refractive index is enhanced to 1.38, the normalized intensity of IR and UV-Vis light diminishes to 0.2 and 0.8, respectively.

Multi-interface level in oil tanks and applications of optical fiber sensors

Abstract On the oil production also involves the production of water, gas and suspended solids, which are separated from the oil on three-phase separators. However, the control strategies of an oil separator are limited due to unavailability of suitable multi-interface level sensors. This paper presents a description of the multi-phase level problem on the oil industry and a review of the current technologies for multi-interface level assessment. Since optical fiber sensors present chemical stability, intrinsic safety, electromagnetic immunity, lightweight and multiplexing capabilities, it can be an alternative for multi-interface level measurement that can overcome some of the limitations of the current technologies. For this reason, Fiber Bragg Gratings (FBGs) based optical fiber sensor system for multi-interface level assessment is proposed, simulated and experimentally assessed. The results show that the proposed sensor system is capable of measuring interface level with a relative error of only 2.38%. Furthermore, the proposed sensor system is also capable of measuring the oil density with an error of 0.8 kg/m3.

A monolithically integrated butt-coupled 3D bulk CMOS Si photodetector array with a fiber couplers platform on a single-chip

A linear array of 55 butt-coupled three-dimensional (3D) photodetectors based on a silicon (Si) substrate is presented with a monolithically integrated tapered U-grooves platform for embedding strands of a fiber bundle into a Si chip. This structure enables a direct coupling of the fiber strands with a diameter of Ø30μm to the vertical photoactive areas of a Si detector array one by one. A vertically 3D large photoactive area ∼30μm×40μm+2(30μm×10μm) is formed separated from the n-i-p structure on the top side to achieve a high performance butt-coupled photodetector. The prototype is fabricated by employing 3D CMOS and MEMS technology on a p-type Si wafer. The implementation of 30μm-deep double-trench isolation with the formation of a shallow n+-p junction and SiO2-liner over the trench sidewalls as well as SU-8 filling of the trenches realizes a high efficiency detector isolation and a low dark current of 1.14nA at 2V reverse bias. The maximum photoresponsivities under illumination with 470nm, 525nm, and 631nm LEDs light are observed under the lowest incident light power. A low junction capacitance of ∼30+/−3fF at 2.4V reverse bias is measured at a frequency of 1MHz. Therefore, this approach brings outstanding features for non-telecom and high efficiency remote optical fiber sensor applications at the wavelengths of 470nm, 525nm, and 631nm in high electromagnetic field environments.

Applications of Fiber Optic Sensors in Space Engineering R&D Activities

Applications of Fiber Optic Sensors in Space Engineering R&D Activities

배관 변형 및 처짐 감시를 위한 광섬유 센서의 활용

배관 변형 및 처짐 감시를 위한 광섬유 센서의 활용

Influence of fiber bending on wavelength demodulation of fiber-optic Fabry-Perot interferometric sensors.

In practical applications of fiber optic sensors based on Fabry-Perot interferometers (FPIs), the lead-in optical fiber often experiences dynamic or static bending due to environmental perturbations or limited installation space. Bending introduces wavelength-dependent losses to the sensors, which can cause erroneous readings for sensors based on wavelength demodulation interrogation. Here, we investigate the bending-induced wavelength shift (BIWS) to sensors based on FPIs. Partially explicit expressions of BIWSs for the reflection fringe peaks and valleys have been derived for sensors based on low-finesse FPI. The theoretical model predicts these findings: 1) provided that a fringe peak experiences the same modulation slope by bending losses with a fringe valley, BIWSs for the peak and valley have opposite signs and the BIWS for the valley has a smaller absolute value; 2) BIWS is a linear function of the length of the bending section; 3) a FPI with higher visibility and longer optical path length is more resistant to the influence of bending. Experiments have been carried out and the results agree well with the theoretical predictions.

IMPROVING OPTICAL FIBER SENSING BY MIMO SIGNAL PROCESSING

Optical fiber sensors have reached a high state of maturity. Besides the high number of sensor groups, multi-mode fiber evanescent field sensors can be found in a lot of applications. Here, the signal source commonly excites many optical modes under steady-state conditions. Perturbations of the fiber then produce leaky modes. Thus, a simple intensity detector measures the degree of perturbation. In some cases also restricted mode launching conditions have been applied. They resulted in higher sensitivity but showed a narrower measurement range. Considering the individual modes as carriers of information we adapted multiple-input multiple-output (MIMO) signal processing which is well studied in the telecommunications community, for improvements on both the sensor sensitivity and its measurement range. In this paper MIMO signal processing is investigated for fiber optic sensor applications. A (2x2) MIMO implementation is realized by using lower-order and higher-order mode groups of a gradient-index multi-mode fiber as separate transmission channels. A micro-bending pressure sensor changes these separate transmission characteristics and introduces additional crosstalk. By observing the layer specific weight-factors of the MIMO system the amount of load applied was determined. Experiments verified a good correlation between the change of the MIMO weight coefficients and the load applied to the sensor and thus verified that MIMO signal processing can beneficially be used for fiber optic sensor applications. The experimental results also verified the superior sensitivity and measurement range when MIMO signal processing is utilized.

Review on Optical Fiber Sensors Based on the Refractive Index Tunability of Ferrofluid

Ferrofluid is a novel kind of functional materials, which possesses both the magnetism of solid magnetic material and fluidity of liquid material. Due to its unique optical properties, especially the refractive index tunability under magnetic field, ferrofluid has been widely utilized for magnetic field and current sensing combined with various optical fiber structures. Hence, in this paper, the refractive index tunability of ferrofluid, which is mainly applied into the optical fiber sensors, is first reviewed and illustrated in detail. Then we mainly introduce our work on the applications of ferrofluid in optical fiber sensors based on the refractive index tunability of ferrofluid, including the whole physical configurations, the operating principles, and the performances of these optical fiber sensors. At last, the deficiencies of ferrofluid in the applications of optical fiber sensors as well as valuable potential prospects in further research are analyzed and presented. From all the above reviews and discussions, it can be foreseen that the characteristics of ferrofluid will be improved and the applications of ferrofluid-based optical fiber sensors will be developed rapidly and maturely.