High-sensitivity Temperature Sensor Research Articles

High-sensitivity temperature sensor based on a droplet-like fiber circle.

A low-cost yet high-sensitivity temperature fiber sensor is proposed and demonstrated in this paper. A single-mode fiber with coating is simply bent in a droplet-like circle with a radius of several millimeters. The strong bending induces mode interferences between the silica core mode and the excited modes propagating in the polymer coating. Many resonant dips were observed in the transmission spectra and are found to shift to a shorter wavelength with the increase of environmental temperature. Our linear fitting result of the experimental data shows that the proposed sensor presents high temperature sensitivity up to -3.102 nm/°C, which is even comparable with sensors based on selective liquid-filled photonic crystal fibers. Such high temperature sensitivity results from the large thermo-optical coefficient difference between the silica core and the polymer coating. The influence of a circle radius to the sensitivities is also discussed.

Research on high sensitivity temperature sensor based on Mach-Zehnder interferometer with waist-enlarged fiber bitapers

Optical fiber sensing technology is one of the very promising techniques in sensing fields. A high sensitivity high temperature sensor based on inline optical fiber Mach-Zehnder(M-Z) interferometer by using standard single mode fiber with two waist-enlarged bitapers is proposed in the present paper. The waist-enlarged bitapers are considered as couplers, the distance between the two bitapers is the sensing arm. The light in the lead-in fiber core couples into the sensing arms' fiber core and cladding by the first bitaper, and then propagate in them. The phase difference between core mode and cladding mode is produced when the light reaches the second bitaper. Then the second bitaper couples the light into the lead-out single-mode fiber to get the interference spectrum. The sensors with different length were fabricated. The relationship between the sensor length and interference period, and the temperature response of the.sensor were studied by experiments. The results show that the 35 mm long sensor has a high sensitivity of 0.115 nm x degrees C(-1) in the range of 30-400 degrees C. The transmission spectrum of the sensor was also analyzed by the fast Fourier transform. It shows that only LP01 mode and LP08 mode propagate in the sensor. Thesensor has advantages of small size, high precision, and immunity to electromagnetic inteference. In addition, it is of easy fabrication, high signal-to-noise ratio, light weight, and high sensitivity, and could be operated under high temperature. This kind of sensor is a good candidate for high temperature measurement of hot gas, oil and gas well logging and other areas.

A sensitivity enhanced temperature sensor based on highly Germania-doped few-mode fiber

An all-fiber high-sensitivity temperature sensor based on highly Germania-doped few-mode fiber (HGFMF) is presented. The sensor employs Mach–Zenhder interferometer configuration and fiber mode LP01 and LP11 are excited in HGFMF. Temperature sensitivity higher than 97pm/°C is demonstrated in experiment.

High sensitivity optical fiber temperature sensor based on the temperature cross-sensitivity feature of RI-sensitive device

Considerable part of optical fiber refractive index (RI) sensors suffer from the drawback of cross-sensitivity to temperature because of the thermo-optic effect of materials. In this paper, we propose a straightforward method to utilize the temperature cross-sensitivity feature of an optical fiber RI-sensitive device and thus got a high sensitivity temperature sensor. The sensor consists of a single mode fiber-multimode fiber core(MMFC)-single mode fiber structural refractometer encapsulated into a deionized water-filled cylindrical aluminum alloy shell. Benefiting from the larger thermo-optic coefficient difference between water and MMFC compared with the general cladding and core, the wavelength of transmitted spectrum presents enhanced shift when the ambient temperature change and thus get a higher temperature sensitivity. Experimental results show that the enhanced temperature sensitivity is about 358pm/°C, which is almost 30 times that of the inherent temperature sensitivity.

Optical Pump Induced Thermal Sensitivity Reduction in a Minimized Er/Yb-Codoped-Fiber Mach–Zehnder Interferometer

The intensity and wavelength dependent thermal characteristics of a minimized Er/Yb-codoped-fiber Mach–Zehnder interferometer are demonstrated theoretically and experimentally. It can be used as a high sensitivity temperature sensor if no pump is introduced. However, once a pump is launched into the interferometer, its thermal sensitivity is reduced. Under pump power of 59.4 mW, 3.1 pm/°C and 10.3 pm/°C reductions of its thermal sensitivities are achieved for the resonance dips at short and longer wavelength ranges, respectively. This suggests that its thermal sensitivity can be tuned by introducing into a pump, and its thermal stability can be improved with the pump.

A high sensitivity temperature sensor realized with cascaded long period fiber grating-based Sagnac loop

A novel cascaded structure which comprises long period fiber gratings inscribed in a single mode fiber and a Panda polarization maintaining fiber is proposed. A high sensitivity temperature sensor is obtained when the novel cascaded structure is inserted into Sagnac loop. Its response to temperature and polarization is investigated. The temperature sensitivity reaches up to −1.26nm/ °C. Furthermore, the experimental results show that notch 1 is almost immune to the state of polarization.

Monitoring Soil Water Content by Vertical Temperature Variations

The availability of high sensitivity temperature sensors (0.001 K sensitivity platinum resistors), which can be positioned at intervals of a few centimeters along a vertical profile in the unsaturated zone, allows short-term in situ determinations-one day or even less-of the thermal diffusivity. The development of high data storage capabilities also makes this possible over long periods and the relative variations in thermal diffusivity allow the monitoring of the variations in water content. The processing of temperature measurements recorded at different depths is achieved by solving the heat equation, using the finite elements method, with both conductive and convective heat transfers. A first set of measurements has allowed this approach to be validated. Water content variations derived from thermal diffusivity values are in excellent agreement with TDR measurements carried out on the experimental site at Boissy-le-Châtel (Seine et Marne, France).

High-sensitivity temperature sensor using the ultrahigh order mode-enhanced Goos-Hänchen effect

A high-sensitivity temperature sensor based on the enhanced Goos-Hänchen effect in a symmetrical metal-cladding waveguide is theoretically proposed and experimentally demonstrated. Owing to the high sensitivity of the ultrahigh-order modes, any minute variation of the refractive index and thickness in the guiding layer induced by the thermo-optic and thermal expansion effects will easily give rise to a dramatic change in the position of the reflected light. In our experiment, a series of Goos-Hänchen shifts are measured at temperatures varying from 50.0 °C to 51.2 °C with a step of 0.2 °C. The sensor exhibits a good linearity and a high resolution of approximately 5×10(-3) °C. Moreover, there is no need to employ any complicated optical equipment and servo techniques, since our transduction scheme is irrelevant to the light source fluctuation.

Design of High Sensitive Pressure and Temperature Sensor Using Photonic Crystal Fiber for Downhole Application

Permanent monitoring of two important parameters, pressure and temperature, plays an important role in reservoir engineering to increase the production rates of oil wells. The numerous advantages of photonic crystal fiber (PCF) sensors make them a proper choice as a sensor in the hostile environment of well. In this paper, we propose short length, high sensitive pressure, and temperature sensor based on hollow-core PCF. The validation of the proposed design is carried out by employing the 3-D finite-difference time domain (FDTD) method. Our sensor mechanism is based on the transmission peak wavelength shift caused by the temperature/pressure changes, with special emphasis on geometric parameters of the structure of PCF. We show that the proposed design provides a sensitivity about 480 nm/RIU with a linear dependence of the resonance wavelength on the refractive index of the ambient and PCF holes at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\lambda = 1.55\ \mu\hbox{m}$</tex></formula> .

Optimization design of high-sensitivity temperature sensor based on Bragg grating in liquid-filled photonic crystal fibers

A high-sensitivity temperature sensor based on fiber Bragg gratings (FBGs) in liquid-filled photonic crystal fibers (PCFs) is proposed. PCF is designed using the full-vector finite-element method. To achieve the maximum difference of the core-mode effective index of PCF as the temperature change, the structural parameters of PCF are optimized via genetic algorithms. The calculated Bragg wavelength shift (BWS) value of FBGs in liquid-filled PCF is 263 pm/°C as the temperature changes from −15°C to 65°C.

Numerical simulation of photonic crystal fiber Bragg gratings filled with liquid

The plane-wave expansion method and coupled-mode theory were used to calculate the reflection spectra of photonic crystal fiber (PCF) Bragg gratings (BGs) filled with liquids (PCF-BGs-liquids). The simulated reflection spectra of the PCF-BGs-liquids agree well with the reported experimental results. The simulated Bragg wavelength shift of the PCF-BGs filled with optical index matched liquid is 100 pm/ °C as the temperature changes from 25 °C to 65 °C. Therefore, PCF-BGs-liquids can be used as high sensitivity temperature sensors.

Monitoring Thermal Effect in Femtosecond Laser Interaction With Glass by Fiber Bragg Grating

Measurement of the local temperature in transparent materials irradiated by femtosecond laser pulses is important for deep insight into light-matter interaction physics and for proper laser micronanomachining, which is, however, technically challenging. We solve the problem in this paper by using a femtosecond laser-written fiber Bragg grating that can stably work up to 1000 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C as a high-sensitivity temperature sensor to monitor the thermal effect. The peak temperature of the thermal impulse is estimated as around 4800 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, which decays to around 500 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C in the pulse interval for irradiation of 1.1 mJ under repetition rate of 1 kHz under 40 mm lens focusing.

High-sensitivity temperature sensor based on an alcohol-filled photonic crystal fiber loop mirror

A compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled high-birefringence photonic crystal fiber (PCF) is proposed and experimentally demonstrated. The output of the FLM is an interference spectrum with many resonant dips, of which the wavelengths are quite sensitive to the change of the refractive index of the filled alcohol for the interference of the FLM. Simulation analysis predicts a high temperature sensitivity, and experimental results show it reaches up to 6.6 nm/°C for the 6.1-cm-long PCF used in the FLM.

使用BDK掺杂光敏聚合物光纤布拉格光栅的高灵敏度温度传感器的研究

A single-mode polymer optical fiber (POF) with highly photosensitive core doped with benzil dimethyl ketal (BDK) is fabricated and used for writing Bragg grating through the two-beam interference method. The Bragg wavelength of the grating is about 1570 nm, while the full-width at half-maximum (FWHM) of the reflection peak is 0.3 nm. The temperature response of POF Bragg grating is theoretically analyzed and experimentally measured in contrast to silica optical fiber Bragg grating (FBG). The result shows that the temperature character of POF Bragg grating is negative, which is opposite to the silica optical FBG. The absolute value of the temperature response of POF Bragg grating is one order of magnitude higher than that of the silica optical FBG, making POF Bragg grating appear to be very attractive for constructing temperature sensors with high resolution.

High-sensitivity temperature sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

High-sensitivity temperature sensor based on Bragg grating in BDK-doped photosensitive polymer optical fiber

High Sensitive Fiber Optic Temperature Sensor Based on a Side-polished Single-mode Fiber Coupled to a Tapered Multimode Overlay Waveguide

A high sensitivity fiber optic temperature sensor based on a side-polished fiber (SPF) coupled to a tapered multimode overlay waveguide (MMOW) is proposed and studied. Both tapered and non-tapered MMOW were considered to study the effect of tapering of MMOW on the characteristics of the device and to investigate the criticality of the uniformity of the multimode overlay waveguide over the SPF. Present study shows that tapering of the MMOW can be used to tune the desired wavelength range without any loss in the sensitivity. Sensitivity up to 9 nm/ $^{\circ}C$ within the temperature range of 25 to $100^{\circ}C$ can be achieved with the proposed sensor, almost 6 times higher compared even to state-of-the-art high-sensitivity grating-based fiber optic temperature sensors.

Optimal design and fabrication of SMS fiber temperature sensor for liquid

Single-mode/multi-mode/single-mode (SMS) fiber sensors are optimally designed and used as high sensitivity temperature sensors in special temperature range. It is shown that the width of multi-mode fiber is a key factor influencing the performance of as-fabricated temperature sensors, which can be effectively controlled in the fabrication process by monitoring the output power of SMS fiber during wet acid etching process. As-fabricated temperature sensors show promising potential applications for precisely monitoring chemical reaction temperature in chemistry and biomedicine fields.

Temperature Dependence of the Resistance of AlGaN/GaN Heterostructures and Their Applications as Temperature Sensors

AlGaN/GaN heterostructures with a two-dimensional electron gas (2DEG) exhibit unique transport properties that could potentially be used for novel applications that are not related to conventional modulation-doped field effect transistor devices. Here, we describe the fabrication of high sensitivity temperature sensors exploiting temperature induced resistance changes of AlGaN/GaN-2DEG heterostructures. We observed a monotonous change in the resistance of the 2DEG from 3 to 1000 K. The temperature dependence of the resistance above 180 K fitted the Callender–Van Dusen equation. The sensitivity of the AlGaN/GaN temperature sensors was more than 2 times higher than conventional resistance temperature detectors near room temperature and 5 times higher at about 900 K. These new AlGaN/GaN temperature sensors may find niche applications in extreme environments, such as space exploration, as well as where high sensitivity is required over wide temperature ranges.

High sensitivity temperature sensor based on a long, suspended single-walled carbon nanotube array

Considering the electron–phonon scattering mechanisms as well as the number of conduction channels, the long single-walled carbon nanotube (SWCNT) has larger temperature coefficient of resistivity than that of the short SWCNT or that of the multi-walled carbon nanotube (CNT). A tens of micrometres length, suspended SWCNT array-based temperature sensor was proposed, and its fabrication technique was presented. The theoretical analysis and the experimental results showed that the long SWCNT array device had high sensitivity and low power consumption than ordinary platinum thermal resistor. The long SWCNT array sensor also featured a simple and application-oriented process and was easier to use than a single CNT-based device. Thus, it has the potential to be applied in high sensitivity temperatures or flow measurements in an ultra small scale.

High Sensitive Temperature Sensor Using a Liquid-core Optical Fiber with Small Refractive Index Difference Between Core and Cladding Materials.

An intensive temperature sensor based on a liquid-core optical fiber has been demonstrated for the measuring the temperature of the environment. The core of fiber is filled with a mixture of toluene and chloroform in order to make the refractive index of the liquid-core and the cladding of the fiber close. The experiment shows that a temperature sensitivity of about 5 dB/K and a tunable temperature range (from 20 oC to 60 oC) can be achieved. Based on the dielectric-clad liquid core fiber model, a simulation was carried out and the calculated results were in good accord with the experimental measurement.