Optical Fiber Temperature Sensor Research Articles

Evaluation of Optical Fiber Macrobendings in Temperature Sensor Dedicated for Power Transformer Monitoring

Optical fiber sensing techniques are recognized as very promising in diagnostic and condition monitoring of power transformers. According to the IEC standard 60076-2, the winding hot-spot temperature can be designated with the optical fiber sensor. In this paper, the investigation of the influence of macrobending of the optical fiber temperature sensor on the sensing performance is presented. The obtained results prove that the optical fiber sensor wrapped six times around the 14 mm cylinder still provides temperature sensing abilities.

Room temperature fiber optic gas sensor technology based Zn3(VO4)2/PMMA hybrid composites via facile hydrothermal route

In this study, the authors present a simple hydrothermal method for obtaining Zn3(VO4)2 nanoparticles encapsulated in a polymethyl-metha-acrylate (PMMA) matrix. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and boron nitride zeta potential were used to determine the structural, topological, and porosity characteristics, respectively. The materials' gas-sensing properties were evaluated using a clad-modified optical fibre sensor. Ammonia, hydrogen sulphide, ethanol, and acetone were used to assess the detecting capabilities of the clad-modified sensing devices. Concentration ranges from 0 to 1000 ppm were tested at RT using both pure and Zn3(VO4)2/PMMA sensors. Zn3(VO4)2 nanopowder-modified fibre optic gas sensors show high sensitivity to ammonia gas at room temperature. The results show that nanocrystalline Zn3(VO4)2/PMMA has the fastest response time (22.4 min) and the longest recovery time (31.5 min) to ammonia (127 counts/Kpa). These results show that the Zn3(VO4)2/PMMA-based clad-removed sensors produced in this study are a highly efficient, potential choice for real-world ammonia sensing.

Fiber Optic Temperature Sensor Using Dual Air- Filled Fabry-Pérot Cavities With Variable Pressure

Fiber Optic Temperature Sensor Using Dual Air- Filled Fabry-Pérot Cavities With Variable Pressure

Ultraviolet-induced sensitivity enhancement of a fiber tip temperature sensor based on adhesive-TiO2 double-cavity composite Fabry-Perot interferometer

A composite fiber Fabry-Perot interferometer (FPI) -based optical fiber temperature sensor is theoretically proposed and practically demonstrated in this work, in which the composite FPI is formed by covering the end face of single-mode fiber with ultraviolet (UV) adhesive and nano-TiO2 coating using the dip-coating method. With the superior thermo-optic characteristic of UV adhesive and the UV absorption of nano-TiO2, the sensitivity of the composite FPI temperature sensor can be effectively enhanced by UV irradiation. After five times of TiO2 dip-coating processes, the composite FPI has a higher temperature sensitivity of 75.3 pm/°C (R2 = 0.9754) under 365 nm UV light, in which the measurement range is from 25 °C to 130 °C and the detection accuracy is 0.66 °C. The proposed sensor has a simple structure and preparation process, competitive sensitivity, high linearity, and satisfactory repeatability and stability, which can be an appropriate candidate to realize high-precision temperature sensing in industrial, chemical, biological, and environmental applications.

Highly Sensitive Temperature Sensor Based on Vernier Effect Using a Sturdy Double-cavity Fiber Fabry-Perot Interferometer.

Temperature measuring is a daily procedure carried out worldwide in practically all environments of human activity, but it takes particular relevance in industrial, scientific, medical, and food processing and production areas. The characteristics and performance of the temperature sensors required for such a large universe of applications have opened the opportunity for a comprehensive range of technologies and architectures capable of fulfilling the sensitivity, resolution, dynamic range, and response time demanded. In this work, a highly sensitive fiber optic temperature sensor based on a double-cavity Fabry-Perot interferometer (DCFPI) is proposed and demonstrated. Taking advantage of the Vernier effect, we demonstrate that it is possible to improve the temperature sensitivity exhibited by the polymer-capped fiber Fabry-Perot interferometer (PCFPI) up to 39.8 nm/°C. The DCFPI is sturdy, reconfigured, and simple to fabricate, consisting of a semi-spherical polymer cap added to the surface of the ferrule of a commercial single-mode fiber connector (SMF FC/PC) placed in front of a mirror at a proper distance. The length of the air cavity (Lair) was adjusted to equal the thickness of the polymer cap (Lpol) plus a distance δ to generate the most convenient Vernier effect spectrum. The DCFPI was packaged in a machined, movable mount that allows the adjustment of the air cavity length easily but also protects the polymer cap and simplifies the manipulation of the sensor head.

Liquid crystal-embedded fiber optic fabry perot temperature sensor based on Vernier effect

An optical temperature sensing method with ultra-high sensitivity and a wide measurement range is proposed. The performance enhancements come from the high thermos-optical coefficient of liquid crystal (LC) material, and the Vernier effect produced by LC birefringence characteristics. This paper proposes and demonstrates a method to enhance the measurement range of the LC temperature sensor. A miniature LC temperature sensor was made by using an optical fiber Fabry-Perot interferometer (FPI). To compensate for and attenuation of LC and improve the contrast of the FPI, silver films are coated on one end of the optical fiber. Due to the high birefringence of the LC in the interferometer, a Vernier spectrum can be observed in the reflection. The temperature measurement range of 20–32 °C and the temperature sensitivity of the Vernier peaks of a sensor sample is about 42.18 nm/°C, which is much higher than the sensitivity of the cascaded FBG in structure. The limited measurement range is due to the free spectral range (FSR) limitation. In this context, the FBG peak can be used as a temperature reference while switching the adjacent Vernier peaks. Hence, this LC temperature sensor exhibits high sensitivity as well as a wide measuring range, which would broaden the application scope of the LC temperature sensors.

Dual-Parametric Simultaneous Demodulation of Fiber Optic Seawater Temperature and Pressure Sensors Based on Machine Learning Methods

Dual-Parametric Simultaneous Demodulation of Fiber Optic Seawater Temperature and Pressure Sensors Based on Machine Learning Methods

Multi-tapered polarization-maintaining fiber-optic sensor for refractive index and temperature measurements

In this paper, a fiber-optic refractive index and temperature sensor based on Mach-Zehnder interferometer (MZI) is designed and fabricated. The sensor structure consists of a section of polarization-maintaining fiber (PMF) with multi-tapers and sandwiched by two sections of multi-mode fiber (MMF). Due to the changes of ambient refractive index and temperature, the effective refractive index of the core and cladding modes of the multi-tapered PMF will be changed, which will cause the interference spectral shift of core mode and cladding mode. The series experiments show that the structure has better repeatability, the maximum refractive index sensitivity is 250.861 nm/RIU, the maximum temperature sensitivity is −78 pm/°C. As the sensitivity matrix is used to realize the two-parameter distinguishing measurement, the resolutions of 1.2 × 10−5 RIU and 0.38 °C for refractive index and temperature are achieved. The structure has superior mechanical properties, and has broad application prospects in petrochemical industry, underwater exploration and other fields.

Temperature Demodulation for an Interferometric Fiber-Optic Sensor Based on Artificial Bee Colony–Long Short-Term Memory

Demodulation methods play a critical role in achieving high-performance interferometric fiber-optic temperature sensors. However, the conventional passive 3 × 3 coupler demodulation method overlooks certain issues, such as the non-1:1:1 splitting ratio of the coupler, resulting in a non-ideal phase difference in the three output interference signals. These problems significantly impact the measurement results of interferometric temperature sensors. In this paper, we propose a novel arc-tangent method based on a 3 × 3 coupler and a demodulation algorithm combining long short-term memory (LSTM) with an artificial bee colony (ABC). The arc-tangent method is employed to enhance the input phase signal of the ABC-LSTM network model and establish a nonlinear mapping between the phase signal and temperature, effectively preventing the influence of the spectral ratio and phase difference of the 3 × 3 coupler on temperature demodulation. The proposed ABC-LSTM method achieves high-resolution measurements with an interval of 0.10 °C, and the absolute error is below 0.0040 °C within the temperature range of 25.00–25.50 °C. To demonstrate the stability and adaptability of the proposed method under long-term constant temperature conditions, we conducted measurements for approximately three hours in a controlled temperature environment set at 25.00 °C. Experimental results indicate that the maximum error of LSTM-ABC method remains around 0.0040 °C, outperforming the conventional algorithm (0.0095 °C). Furthermore, when comparing the average error values of the conventional passive 3 × 3 coupler method (0.0023 °C), LSTM model (0.0019 °C), and ABC-LSTM model (0.0014 °C), it is evident that the demodulation results of the ABC-LSTM method exhibit the highest level of stability. Therefore, the ABC-LSTM method enhances the accuracy and reliability of interferometric fiber-optic temperature-sensing systems.

A Novel Distributed Optical Fiber Temperature Sensor Based on Raman anti-Stokes Scattering Light

In this paper, a novel distributed optical fiber temperature sensor based on Raman anti-Stokes scattering light is proposed and experimentally demonstrated. The Raman anti-Stokes scattering light is sensitive to temperature parameters that are detected by the fiber under test conditions (FUT), and this allowed the temperature demodulation algorithm to be obtained through the relationship between the temperature and the power of the back-scattered Raman anti-Stokes light. In addition, we propose a new temperature calibration method to ensure accurate temperature measurement, which is greatly affected by the stability of a pulse laser. The experimental system is constructed with an optical fiber length of approximately 3.5 km. The proposed system obtains a 24 dB dynamic range with a pulse width of 20 ns and temperature testing ranges of 30.0 °C to 80.0 °C. The results demonstrate that the maximum temperature deviation range is −1.5 °C to +1.6 °C and the root mean square (RMS) error of the whole temperature range is 0.3 °C, which means it has the potential for practical engineering applications. More importantly, it avoids the walk-off effect that must be corrected in commonly used temperature demodulation schemes adopting both Raman Stokes light and anti-Stokes light. It also saves a signal channel, which is more suitable for the integration of hybrid distributed optical fiber sensing systems for multi-parameter monitoring.

PANDA Fiber Sagnac Interferometer for Temperature Sensor Application

Fiber Sagnac loop mirror has great potential for use in various application such as multi-wavelength laser source, strain and temperature sensors. This paper demonstrates an optical fiber temperature sensor based on two lengths of PANDA polarization maintaining fibers (PMFs) in a fiber Sagnac interferometer. The temperature sensing is based on the change of spectral spacing of the generated optical comb with the temperature difference between two PMFs. The performance of the system was characterized numerically and experimentally by measuring the spectral spacing when raising the temperature of one of the PMFs. A high temperature sensitivity up to 0.36 nm/°C is obtained, with detuning range of 43 nm. This makes it a good candidate for various in-field sensing application.

Investigation of the influence of external factors on the operation of a fiber-optic dielectric temperature sensor

The article presents the design and test results of a fiber-optic dielectric temperature sensor intended for use under the influence of external electromagnetic field and aggressive environment.

Fiber-optic temperature sensor based on glass Fabry–Perot interferometer

The paper presents a theoretical and experimental study of a fiber-optic all-glass microthermometer based on a Fabry–Perot interferometer. The interferometer is fabricated by applying borosilicate glass to the cleaved end of a standard telecom single-mode optical fiber using a microforge. According to the results of experimental studies, the spectral sensitivity of the fabricated interferometer was about 40 pm/°C. A mathematical model of the Fabry–Perot interferometer based on the method of scattering and transfer matrices is presented and verified, which makes it possible to calculate the spectral response of an interferometer with arbitrary structure parameters.

Fiber-optic temperature sensor based on glass Fabry – Perot interferometer

In this work, analytical expressions are obtained that allow one to determine the shift of the central wavelength of a four-component addressable fiber Bragg structure (FAFBS). The computer simulation of the use of CHAVBS in the problems of measuring the temperature of the windings of power transformers has been carried out. Simulation showed that more accurate temperature measurement results are obtained when the circuit operates in reflection, i.e. at an additional address frequency. With the use of FAFBS, there is no need to install additional frequency filters. It is not required to use address component recovery schemes compared to the three-component AFBS option. This fact is a significant difference between the developed systems based on AFBS and systems based on two- and three-component AFBS.

Active Thermostatting of the Reference Optical Fiber Section Method in a Distributed Fiber-Optical Temperature Sensor

Active Thermostatting of the Reference Optical Fiber Section Method in a Distributed Fiber-Optical Temperature Sensor

High-Sensitivity Temperature Sensor Based on Fiber Fabry-Pérot Interferometer with UV Glue-Filled Hollow Capillary Fiber.

Optical fiber Fabry-Pérot (FP) interferometer sensors have long been the focus of researchers in sensing applications because of their simple light path, low cost, compact size and convenient manufacturing methods. A miniature and highly sensitive optic fiber temperature sensor using an ultraviolet glue-filled FP cavity in a hollow capillary fiber is proposed. The sensor is fabricated by fusion splicing a single-mode fiber with a hollow capillary fiber, which is filled with ultraviolet glue to form a FP cavity. The sensor has a good linear response in the temperature testing and high-temperature sensitivity, which can be increased with the length of the FP cavity. The experimental results show that the temperature sensitivity reaches 1.174 nm/°C with a high linear response in the range of 30-60 °C. In addition, this sensor is insensitive to pressure and can be highly suitable for real-time water temperature monitoring for ocean research. The proposed ultraviolet glue-filled structure has the advantages of easy fabrication, high-temperature sensitivity, low cost and an arbitrary length of capillary, which has broad application prospects for marine survey technology, biological diagnostics and environmental monitoring.

Fiber Optical Temperature Sensor Based on 980nm Excitation of CaWO4: Yb3+, Er3+ with Up-conversion Fluorescence Intensity Ratio

The Yb3+, Er3+ co-doped calcium tungstate materials were prepared. The temperature-sensitive fiber optic probes made from CaWO4:Yb3+, Er3+ were prepared by the high-temperature solid-phase sintering method. The XRD lattice structure of CaWO4: Yb3+, Er3+ was tested. The fluorescence spectra of the probe under 980nm excitation were tested, and the variable temperature profile of the probe was analyzed to derive its two-photon absorption process. The temperature characteristics of the up-conversion fluorescence intensity ratio (FIR) of the probe in the temperature range of 303-673K were investigated, and the results showed that this optical fiber probe can be used as a fiber optic temperature sensor with a linearity of 5.8% and a temperature measurement return difference of only 1.5%; it was found that the temperature characteristic curve of FIR of this fiber optic probe was reproducible. These properties show that CaWO4: Yb3+, Er3+ is feasible to be made into a fiber optic sensor.

Optical Fiber Temperature and Humidity Dual Parameter Sensing Based on Fiber Bragg Gratings and Porous Film.

A porous anodic alumina film is proposed to construct an optical fiber temperature and humidity sensor. In the sensor structure, a fiber Bragg grating is used to detect the environment temperature, and the porous film is used to detect the environment humidity. The proposed porous anodic alumina film was fabricated by anodic oxidation reaction, and it is suitable for the use of humidity detection due to its porous structure. Experimental results show the temperature sensitivity of the proposed sensor was 10.4 pm/°C and the humidity sensitivity of the proposed sensor was 185 pm/%RH.

Design of Surface Plasmon Resonance-Based D-Type Double Open-Loop Channels PCF for Temperature Sensing.

Here, we document a D-type double open-loop channel floor plasmon resonance (SPR) photonic crystal fiber (PCF) for temperature sensing. The grooves are designed on the polished surfaces of the pinnacle and backside of the PCF and covered with a gold (Au) film, and stomata are distributed around the PCF core in a progressive, periodic arrangement. Two air holes between the Au membrane and the PCF core are designed to shape a leakage window, which no longer solely averts the outward diffusion of Y-polarized (Y-POL) core mode energy, but also sets off its coupling with the Au movie from the leakage window. This SPR-PCF sensor uses the temperature-sensitive property of Polydimethylsiloxane (PDMS) to reap the motive of temperature sensing. Our lookup effects point out that these SPR-PCF sensors have a temperature sensitivity of up to 3757 pm/°C when the temperature varies from 5 °C to 45 °C. In addition, the maximum refractive index sensitivity (RIS) of the SPR-PCF sensor is as excessive as 4847 nm/RIU. These proposed SPR-PCF temperature sensors have an easy nanostructure and proper sensing performance, which now not solely improve the overall sensing performance of small-diameter fiber optic temperature sensors, but also have vast application prospects in geo-logical exploration, biological monitoring, and meteorological prediction due to their remarkable RIS and exclusive nanostructure.

Optical fiber temperature sensor based on beat frequency and Vernier effect of fiber ring resonator composite cavity

A fiber temperature sensing scheme based on beat frequency and Vernier effect of fiber ring resonator (FRR) with composite cavity is proposed and experimentally demonstrated. The optical FRR as a sensor is put into the linear cavity fiber laser, and Vernier effect is generated when the resonance spectrum of the optical FRR and the longitudinal mode of the laser are superimposed. The beat frequency envelope spectrum corresponding to the longitudinal mode Vernier spectrum is used to realize fiber ring sensing in electrical domain, and the sensing information is obtained by tracing the envelope of beat frequency signal, which has the advantages of stable system, simple structure, low cost and high sensitivity.