Fiber Temperature Sensor Research Articles

A preliminary study on wellbore flow interpretation of fiber optic vibration signals based on K-means clustering algorithm

The wellbore flow analysis of optical fiber vibration signal depends on distributed optical fiber logging. Distributed optical fiber logging technology identifies the fluid in the well through distributed optical fiber acoustic sensor (DAS) and distributed optical fiber temperature sensor (DTS). Distributed optical fiber sensor has the advantages of small underground interference, high efficiency and low cost. In this paper, the wellhead data extracted by the distributed optical fiber acoustic sensor is used to calculate the upper bound of the fluid sound frequency band in the pipe by nonlinear least squares fitting. The K-means clustering algorithm is used to cluster the optical fiber vibration signals in the low frequency band. According to the clustering results, the ratio of the optical fiber signal eigenvalues of each production layers is obtained, and the trend of the ratio of the optical fiber signal eigenvalues of each production layers is judged to be close to the trend of the water absorption intensity. Compared with traditional acoustic logging, the wellbore flow analysis using distributed optical fiber acoustic sensor can quickly determine the production contribution of each layer and the change of fluid phase state in the production cycle. Combined with traditional production logging technology, distributed optical fiber logging shows its reliability and accuracy in data collection, logging interpretation and production application. Starting from the principle of distributed optical fiber acoustic sensing technology, this paper briefly expounds the properties of distributed optical fiber acoustic sensor and the principle of injection profile logging, systematically introduces the processing of distributed optical fiber acoustic data, and emphatically introduces the accuracy of K-means clustering algorithm for analyzing distributed optical fiber acoustic signal and qualitative judgment of production layer, which provides a new idea for judging the accuracy of production layers.

An all-sapphire fiber temperature sensor for high-temperature measurement

An all-sapphire high-temperature optical fiber sensor with an extrinsic Fabry–Perot interferometer (EFPI) structure is proposed and experimentally demonstrated. The EFPI structure of the sensor is composed of a sapphire ferrule with a sapphire fiber and a polished solid sapphire crystal rod. The first reflection occurs on the left end of the sapphire ferrule, and the second reflection occurs on the right end of the sapphire rod, forming double-beam interference. The interference signal is picked up by the sapphire fiber and transmitted to the white light interferometric demodulator by the multimode fiber. The picked-up signal is demodulated by the Fourier transform and interference algorithms. Experimental results show that the temperature response of the sensor is quadratic, and that the sensitivity changes linearly with a temperature range from room temperature to 1500 °C. The first-order thermal expansion coefficient and the second-order thermal expansion coefficient are 5.4575 × 10−6 °C−1 and 7.3755 × 10−9 °C−2, respectively. The thermal expansion coefficient is linearly related to temperature. Due to its all sapphire structures, this sensor solves the problem of thermal expansion coefficient mismatch, which was observed in a previous sensor made of sapphire and ceramic materials. In addition, it improves the high-temperature resistance, so it can be fully qualified for long-term high-temperature measurements above 1000 °C–1500 °C.

High resolution polymer/air double-cavity Fabry–Perot fiber temperature sensor based on exposed core microstructured fiber

This study proposes a high-resolution optical fiber Fabry–Perot (FP) temperature sensor and it is based on an exposed-core microstructured optical fiber (ECF) coated by a ultraviolet curing polymer adhesive. Then, a small piece of multimode fiber (MMF) with large core diameter is spliced in front of ECF to expand the input light beam, and the parallel polymer/air double-cavity FP in such single-mode fiber (SMF)-MMF-ECF-SMF structure is constructed. Additionally, by employing a mobilized demodulation module, the interference signal is analyzed by phase demodulation method. The experimental results show that the temperature sensitivity of the sensor is 30.8 ℃−1 and the resolution is up to 1.6 × 10−4 ℃ in a range of 20 ℃–50 ℃, which can achieve high resolution temperature measurement. Furthermore, to alleviate the wavelength uncertainty of the demodulation device, a double-cavity self-reference differential phase modulation method is explored in the proposed parallel double-cavity FP. It shows that the stability could be improved to five times when system temperature is unstable, which offers an alternative method to further improve the temperature sensing resolution.

A Panda fiber temperature sensor up to 900°C

The use of Panda-type polarization-maintaining (PM) fiber for the localized sensing of high temperatures was analyzed with simulations and experiments up to 900°C. Accuracy and repeatability of the results started to decline above 800°C. Fused silica optical fiber melts at 1700°C, which sets an ultimate limit for measurable temperatures. In practice, optical fiber birefringence restricts the maximum temperature to 1060°C where PM fiber loses its ability to maintain polarization. Three sensor fibers (4, 5 and 10 cm long) were spliced at 45° angles to input/output fibers and calibrated in an oven from room temperature to 850–900°C temperature range. Two superluminescent light-emitting diodes (SLEDs) were coupled together as a broadband light source. Birefringence-induced change of the polarization in the sensor fiber was measured with a polarization splitter and an optical spectrum analyzer (OSA) as a function of the wavelength. Temperature-dependent birefringence generates a sinusoidal reflection spectrum from the input polarization mode to the orthogonal output polarization mode. Temperature changes could be concluded from variations in these spectra. Finally, a small fusion device, NORTH, at DTU, Denmark was successfully used as a testbed to make sure that the sensors can handle transportation and the instrumentation required for vacuum operation and still produce sensible data from a harsh environment.

D-Shaped Surface Plasmon Photonic Crystal Fiber Temperature Sensor

A D-shaped photonic crystal fiber (PCF) temperature sensor based on surface plasmon resonance (SPR) with high sensitivity and high figure of merit is presented in this paper. To enhance surface plasmon resonance, the gold film is deposited on the polished flat of D-shaped photonic crystal fiber. Ethanol and chloroform are employed as temperature-sensitive materials, which are placed on the outside of the fiber to detect temperature changes. When the phase-matching condition is met, the core mode couples with the surface plasma mode. The finite element method is used to perform all numerical simulations of sensor characteristics in the COMSOL software. The results show that the highest sensitivity of the sensor can reach 6.36 nm/°C and the maximum figure of merit (FOM) is 0.3440/°C in the range of −5 ~ 60 °C. To our knowledge, the achieved sensing characteristics are significantly better than those of the current PCF temperature sensors. Furthermore, excellent linearity with a polynomial fit R2 as high as 0.9981. The proposed sensor has exceptional performance in terms of temperature detection range, sensitivity, FOM, and fabrication, making it suitable for a wide variety of biochemical and medical applications.

Double-sided photonic crystal fiber (PCF) temperature and refractive index (RI) sensor based on surface plasmon resonance (SPR)

A double-sided photonic crystal fiber (PCF) temperature and refractive index (RI) sensor based on surface plasmon resonance (SPR) is reported to simultaneously measure temperature and RI. An arc groove covered with gold is filled with chloroform for temperature detection. The D-shaped plane coated with silver is in direct contact with the analyte to provide the RI. Two independent channels distinguish temperature and RI changes, thus completely solving the cross-sensitivity problem. The sensing characteristics of the plane coating, arc coating, and inner ring coating are discussed. The influence of gold film closure on the optimum RI measurement range was identified, and the best sensing structure of chloroform as a temperature-sensitive material is obtained. The sensing characteristics of different types of metal films are investigated. It is concluded that the band separation may be achieved by plating gold film and silver film in the arc groove and D-plane, respectively. The influence of the central angle of the arc groove on the sensor characteristics was investigated. High-order resonance may be avoided at a 180° center angle. The influence of the thickness of the metal film on the sensitivity of the sensor is studied numerically, and the optimal coating thickness is 50 nm. This work simplifies the selection of the RI range of sensing materials and provides a new approach to solve the high-order resonance and band interference in SPR multi-parameter sensors.

Mn2+-activated dual-wavelength emitting materials toward wearable optical fibre temperature sensor

Photothermal sensing is crucial for the creation of smart wearable devices. However, the discovery of luminescent materials with suitable dual-wavelength emissions is a great challenge for the construction of stable wearable optical fibre temperature sensors. Benefiting from the Mn2+-Mn2+ superexchange interactions, a dual-wavelength (530/650 nm)-emitting material Li2ZnSiO4:Mn2+ is presented via simple increasing the Mn2+ concentration, wherein the two emission bands have different temperature-dependent emission behaviours, but exhibit quite similar excitation spectra. Density functional theory calculations, coupled with extended X-ray absorption fine structure and electron-diffraction analyses reveal the origins of the two emission bands in this material. A wearable optical temperature sensor is fabricated by incorporating Li2ZnSiO4:Mn2+ in stretchable elastomer-based optical fibres, which can provide thermal-sensitive emissions at dual- wavelengths for stable ratiometric temperature sensing with good precision and repeatability. More importantly, a wearable mask integrated with this stretchable fibre sensor is demonstrated for the detection of physiological thermal changes, showing great potential for use as a wearable health monitor. This study also provides a framework for creating transition-metal-activated luminescence materials.

Polarization Maintaining Fiber Temperature and Stress Gradient Sensitization Sensor Based on Semiconductor-Metal-Polymer Three-Layer Film Coating.

Increasing sensitivity, measuring points, and stability have always been the pursuit of sensors. ZnSe9:CO1 and Ag composite nano films were coated on polarization maintaining fiber (PMF). Then, the coated PMF was nested in capillary and hose which was encapsulated with polydimethylsiloxane (PDMS) and epoxy resin. The integrated capillary sensor and thermoplastic hose sensor were prepared. The gradient sensitization of various measurement parameters such as temperature, stress, and micro bending is realized. The temperature sensitivity is 1.49 nm/°C, the micro bending sensitivity is 1.72 nm/102 g, and the stress sensitivity is 6.27 nm/mε. The sensors maintain good linearity and instantaneous response while having high sensitivity. By adjusting the length of PMF, the number of troughs is increased in the same band range, and different troughs have different sensitivities, which solves the inherent problem of cross sensitivity and realizes multiparameter measurement. Capillary sensors are used for remote safe real-time monitoring of mechanical overheating, and hose sensors are used for real-time monitoring of bridge load and human joint bending. This work is of great significance to the extension of the application range of optical fiber sensor.

Ultrasensitive fiber-optic temperature sensor based on cascaded Sagnac interferometers with a nematic liquid crystal film

We demonstrated an ultrasensitive fiber-optic temperature sensor based on cascaded Sagnac interferometers (CSIs). One of the Sagnac interferometers (SIs) consisted of a panda polarization-maintaining fiber (PMF) as the reference arm, while the other one contained two single-mode patch cables in a ferrule matching sleeve as the sensing arm, where a nematic liquid crystal (NLC) film was infiltrated into the micron-scale gap of the sleeve. In the sensing SI, the orientation of NLC film was induced by just rotating the two single-mode patch cables without any orientation agent, electric, or magnetic devices. Vernier effect was acquired by adjusting the thickness of NLC film. Experimental results revealed that the temperature sensitivity of the CSIs was up to 43.13 nm/°C, which was enhanced about 5 times compared to the single NLC SI. The designed optical fiber temperature sensor possessed the merits of compact structure, high stability, ultrahigh sensitivity, low hysteresis effect and high resolution, showing a promising application prospect in some scientific filed requiring accurate temperature measurement, such as biomolecules, medicine and other filed.

Effect of fluorine substitution on the structure and spectral property of fluorotellurite glass for upconversion luminescence thermometry

A series of TeO2–ZnO–ZnF2–La2O3–Yb2O3–Er2O3 glasses (TZL) with different amount of ZnF2 were prepared by the melt quenching method. The effects of fluorine concentration on the density, refractive index, thermal behavior, and vibrational characteristic of TZL glasses were analyzed. The Judd-Ofelt (J-O) theory was employed to study the spectroscopic properties of Er3+ ions. By using the J-O intensity parameters the spontaneous radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of some concerned transitions of Er3+ were predicted. The potential of TZL glasses for the gain around 1.5 μm was briefly evaluated. Moreover, the upconversion luminescence was investigated under the excitation of 980 nm laser. The dependence of luminescence intensity on pump power revealed that the upconversion luminescence of Er3+ in TZL glasses are contributed by two-photon involved energy transfer processes. Furthermore, the adjacent upconversion green emissions of Er3+ ions were used to temperature sensing based on the fluorescence intensity ratio (FIR) technique. High absolute sensitivity and resolution have been obtained, which indicate that the TZL glasses are potential materials for optical fiber temperature sensors.

High-Resolution Optical Fiber Temperature Sensor Based on Draw Tower Grating Array.

Ocean temperature monitoring is of great significance to marine fishing, aquaculture, and marine operations. Traditional electric sensors lack the potential to multiplex several sensors, and may suffer from electromagnetic interference. Meanwhile, fiber Bragg grating-based sensors have the advantages of high sensitivity, possibility for large-scale multiplexing, and immunity to electromagnetic interference. In this paper, we propose a Fabry–Pérot (FP) interferometer based on the draw tower grating array and combine it with the phase measurement method for demonstration and testing. In the sensor system, two adjacent fiber Bragg gratings (FBGs) are used as mirrors and an optical fiber connects them, forming a sensor unit. The signal was detected through the compensation of the optical path difference via two-arm path differences in an unbalanced interferometer. The sensor is calibrated in the range of 36.00–36.50 °C, and back to 36.00 °C, in steps of 0.10 °C. A thermocouple (DW1222) is used as a reference. Experimental testing demonstrates that under the thermal loop, the temperature and phase can be approximated as a linear relationship, the Pearson square correlation coefficient is 0.9996, and the temperature sensitivity is −9846 rad/°C. To prove that our experimental device can achieve a higher temperature resolution, we measured the background noise of the system. The experimental results indicate that the order of magnitude of our system temperature resolution can reach 10−5 °C. Thus, we believe that the sensor system is promising for the application of ocean temperature detection, and owing to the ultraweak reflection characteristics of the FBG, this method provides the possibility for large-scale multiplexing of the system.

MZI interferometric fiber optic temperature sensor based on MFC

AbstractFor biological embryo incubation, it is very important to monitor temperature accurately, so a new Mach–Zder interference (MZI) fiber temperature sensor is based on a microfiber coupler (MFC). It consists of a 3 dB fiber coupler and MFC forming an MZI structure. Since the MFC has strong evanescent field properties, higher sensitivity can be generated when fully acting with the external temperature environment. The experimental results show that the optical fiber sensor has good temperature response properties in the temperature range of 24–38°C, and the temperature sensitivity increases rapidly as the MFC waist diameter decreases. The maximum wavelength sensitivity of approximately 191.93 pm/°C and R2 = 0.98739, with the advantages of high sensitivity, simple manufacturing, and low cost can be applied in the field of bioincubation temperature monitoring.

Deep Learning Based Data Augmentation and Behavior Prediction of Photonic Crystal Fiber Temperature Sensor

A photonic crystal fiber (PCF) structure which offers exceptional research prospects to design sensors is eccentrically found applicable in wide variety of fields and thus have prompted a lot of interest among researchers. However, intending to determine PCF design configuration producing desired optical response for worthwhile application forcefully necessitates investigating vast search space with suitable topological structure variants. Moreover, the existing Finite Element Method (FEM) based numerical simulation software demands intensively long computation time for each set of design parameters with quite several repetitions and is a challenging task with reduced computational complexity. In this regard, use of Deep Neural Networks (DNN) paves way to predict the outcome in less time. One of the most significant challenges encountered while training a neural network is to generate an extensive data set. With the motive of compensating for the same issue, we propose the use of Autoencoder (AE) network to achieve data augmentation. In this research, a pioneering approach to predict optical parameters of PCF based temperature sensor using AE and DNN is presented. The proposed model is designed to make appropriate predictions of optical properties even for unknown design space parameters. The comparative metric analysis explores the efficient performance of the model with high values of R-squared ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$r^{2}$ </tex-math></inline-formula> ) score and less computation time in contrast to simulation run-time of FEM. Moreover, the proposed DNN model along with AE is proved to show very low collective mean squared error (MSE) in contrast to DNN without AE.

Fiber optic high temperature sensor based on ZnO composite graphene temperature sensitive material

The working temperature of the cable is particularly important for the safe operation of the power system, which requires high temperature detection for its working environment, but the sensitivity of the ordinary optical fiber temperature sensor in the high temperature state cannot meet this demand. For this purpose, an optical fiber high temperature sensor based on ZnO composite graphene temperature sensitive material is developed in this paper. MMF-TSCF-MMF temperature sensing unit is composed of two sections of multimode fiber (MMF) and a tapered seven core fiber (TSCF). Three different shapes of ZnO@Gr (ZnO composite graphene) temperature-sensitive materials were prepared by hydrothermal method. The experimental results show that the sensor has high stability and good interference effect. Meanwhile, the wavelength sensitivity reached 0.33268 nm/°C in a temperature measurement range of 89–98 °C. The fiber sensor is used for precision temperature measurement of cable temperature in fields such as electrical engineering due to its high temperature sensitivity, small size and low cost.

A Surface Plasmon Resonance Optical Fiber Sensor for Simultaneous Measurement of Relative Humidity and Temperature

In this work, a new method was explored for developing temperature and relative humidity (RH) optical fiber sensors based on surface plasmon resonance (SPR). A SPR optical fiber sensor coated with carboxymethyl cellulose (CMC) and polydimethylsiloxane (PDMS) was proposed for the simultaneous measurement of RH and temperature. The sensor was fabricated by connecting two no-core optical fibers (NCFs) using multimode optical fibers (MMFs). Metal films were deposited on the surface of NCFs and further coated with CMC and PDMS. CMC coating was used for RH sensing based on the change of refractive index (RI) caused by water absorption; PDMS coating was used for temperature sensing based on its RI change with temperature. Univariate analysis showed that there was very weak interaction between RH and temperature measurement. For RH sensing, the sensitivities were &#x2212;1.230 nm/RH&#x0025;, &#x2212;2.932 nm/RH&#x0025; and &#x2212;0.431 nm/RH&#x0025; when RH were 50&#x0025;&#x007E;65&#x0025;, 65&#x0025;&#x007E;70&#x0025; and 70&#x0025;&#x007E;80&#x0025;, respectively; for temperature sensing, the sensitivity was &#x2212;2.213 nm/&#x00B0;C at 10 &#x00B0;C&#x007E;50 &#x00B0;C. The proposed sensor can not only respond to both temperature and RH variation, but also compensate the cross sensitivity between the two parameters. It is simple in structure, easy to manufacture and efficient in the simultaneous detection of temperature and RH, which promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

Micro-Tapered Fiber Few-Mode Interferometers Incorporated by Molecule Self-Assembly Fiber Grating for Temperature Sensing Applications

We demonstrate fiber few-mode interferometers based on a self-assembly surface corrugated grating using charged nano-particles. Initially, an abrupt taper (AT) was first created using a micro flame. The AT was then further outwardly stretched to make an elongated uniformed taper until the tapered diameter achieved a micron scale. The high order core modes (HOCMs) were excited at the AT and the optical path difference (OPD) among the modes was enlarged through the uniformed taper to achieve the few-mode interference effects seen. However, to significantly enhance the interference effects with higher extinction ratios (ER) over such a short length of interferometer, an external assisted grating was made using charged nanoparticles to form surface corrugated grating with a period, Λ, of approximately 14 μm. This intermediate period of the fiber grating was helpful in scattering and attenuating some unwanted high-order modes to change the optical characteristics of the few-mode interferometer (FMI). This FMI with a self-assembly fiber grating (SAFG) was further used to make fiber temperature sensors, with a maximum resonant wavelength shift of 4.6 nm, over a temperature range from 20–60 °C. The temperature sensitivity achieved was 112.6 pm/°C and the coefficient of determination, R2, was as high as 0.99, which revealed the high linearity of the results.

Cost-efficient and reliable annular optical fiber temperature sensor.

In this paper, an annular winding structure made of single-mode optical fiber is proposed as the core of a cost-efficient and reliable annular optical fiber temperature sensor (AOFTS). The sensor is mainly due to the multi-mode interference effect to achieve real-time response to external temperature changes. The experimental results show that the average temperature sensitivity of the sensor is about 255.5 pm/°C in the temperature range of -20∘C-110∘C; it has higher sensitivity at low temperatures. At -20∘C, the sensitivity of the AOFTS reaches 450 pm/°C. The sensor has the advantages of simple fabrication, low fabrication cost, strong stability, and good reproducibility and repeatability. It has great application prospects in the field of low-temperature detection.

D-Shaped Optic Fiber Temperature and Refractive Index Sensor Assisted by Tilted Fiber Bragg Grating and Pdms Film

D-Shaped Optic Fiber Temperature and Refractive Index Sensor Assisted by Tilted Fiber Bragg Grating and Pdms Film

High-Precision Optical Fiber Temperature and Pressure Sensor and Its Application in Production Wells

High-Precision Optical Fiber Temperature and Pressure Sensor and Its Application in Production Wells

Optical fiber temperature sensor of Er3+/Yb3+ codoped LaGaO3 microcrystals with high reliability and stability

Er3+/Yb3+ codoped LaGaO3 microcrystals with excellent upconversion luminescence and temperature sensing were prepared. And an optical fiber temperature sensor with high accuracy and stability is constructed with the phosphor.