Optical Fiber Thermometry Research Articles

Mn4+/Eu3+ co-doped fluoride toward a blue light-excited optical fiber thermometer.

The ongoing development of ratiometric optical thermometry is mainly trapped in thermally coupled levels of rare-earth ions and inefficient ultraviolet excitation. Herein, a new-type multiple sharp line emitting, blue light-excited K2NaInF6:Mn4+, Eu3+ fluoride phosphor has been reported as a ratiometric thermometer. The f-f transition of Eu3+ paves a steady reference to a highly temperature sensitive Mn4+d-d transition and enables high relative sensitivity of 1.65% K-1 at 573 K. An optical fiber thermometry on a household oven with a relative standard deviation of 0.11% surpasses the standard of precision measurement, showing great potential in practical application. This discovery offers a highly sensitive neotype blue light-excitable ratiometric temperature sensor, that is Mn4+-doped fluoride, promoting practical applications of optical thermometry.

Bandwidth-based flexible optical fiber thermometry based on sharp line emission regulation of Cr3+ ions

Bandwidth-based flexible optical fiber thermometry based on sharp line emission regulation of Cr3+ ions

Microwave heating and devolatilization characteristics of polyethylene particles in a fixed‐bed devolatilizer

AbstractA new method of microwave‐enhanced devolatilization has been proposed to solve the problem that volatiles of polyethylene particles are difficult to remove. Using water as microwave susceptor in a fixed‐bed devolatilizer, microwave heating characteristics were studied by optical fiber thermometry and infrared thermal imaging, and particle devolatilization characteristics were investigated by headspace gas chromatography. The results showed that bed temperature rose and particle devolatilization efficiency increased with heating time, moisture content, and input microwave power. The non‐uniform devolatilization at different positions existed due to the non‐uniform distribution of bed temperature in both radial and axial directions. The effective diffusion coefficient of volatiles under microwave irradiation increased with moisture content and input microwave power, and the microwave‐enhanced coefficient of water also increased with input microwave power. Microwave heating and devolatilization mechanism of moist polyethylene particles were proposed, in which the modes of mass and energy transfer were clarified. In view of the above, the feasibility of microwave‐enhanced polyethylene devolatilization has been confirmed.

Yb/Ho Codoped Layered Perovskite Bismuth Titanate Microcrystals with Upconversion Luminescence: Fabrication, Characterization, and Application in Optical Fiber Ratiometric Thermometry.

Optical thermometry has attracted great interest owing to its noncontact and fast responsive properties in practical applications. However, some sensing errors may occur in many optical ratiometric thermometers due to the overlap of emission peaks, suggesting the necessity of developing excellent luminescent materials. Here, we report the fabrication and characterization of Bi4Ti3O12:Yb/Ho for ratiometric thermometry. Bismuth titanate was selected as the matrix due to its low phonon energy, high machinability, and satisfactory thermal stability. The temperature sensing was constructed on the intensity ratio of the two upconversion emission bands with wide separation in Bi4Ti3O12:Yb/Ho under 980 nm excitation. The wide separation endows the materials with high signal discrimination for temperature detection. The developed materials were characterized in terms of crystal structure, reflectance, and emission spectra for thermometry application. The maximum relative sensitivity was shown to be as high as 2.11% K-1. More importantly, an optical fiber thermometry was developed based on the fabricated microcrystals, which can find its potential applications in harsh environments.

Simultaneous fat-referenced proton resonance frequency shift thermometry and MR elastography for the monitoring of thermal ablations.

Simultaneous fat-referenced proton resonance frequency shift (FRPRFS) thermometry combined with MR elastography (MRE) is proposed, to continuously monitor thermal ablations for all types of soft tissues, including fat-containing tissues. Fat-referenced proton resonance frequency shift thermometry makes it possible to measure temperature even in the water fraction of fat-containing tissues while enabling local field-drift correction. Magnetic resonance elastography allows measuring the mechanical properties of tissues that are related to tissue structural damage. A gradient-echo MR sequence framework was proposed that combines the need for multiple TE acquisitions for the water-fat separation of FRPRFS, and the need for multiple MRE phase offsets for elastogram reconstructions. Feasibility was first assessed in a fat-containing gelatin phantom undergoing moderate heating by a hot water circulation system. Subsequently, high intensity focused ultrasound heating was conducted in porcine muscle tissue ex vivo (N = 4; 2 samples, 2 locations/sample). Both FRPRFS temperature maps and elastograms were updated every 4.1 seconds. In the gelatin phantom, FRPRFS was in good agreement with optical fiber thermometry (average difference 1.2 ± 1°C). In ex vivo high-intensity focused ultrasound experiments on muscle tissue, the shear modulus was found to decrease significantly by 34.3% ± 7.7% (experiment 1, sample 1), 17.9% ± 10.0% (experiment 2, sample 1), 55.1% ± 8.7% (experiment 3, sample 2), and 34.7% ± 8.4% (experiment 4, sample 2) as a result of temperature increase (ΔT = 22.5°C ± 4.2°C, 14.0°C ± 2.8°C, 14.7°C ± 3.7°C, and 14.5°C ± 3.0°C, respectively). This study demonstrated the feasibility of monitoring thermal ablations with FRPRFS thermometry together with MRE, even in fat-containing tissues. The acquisition time is similar to non-FRPRFS thermometry combined with MRE.

Er3+/Yb3+ co-doped tellurite glasses for optical fiber thermometry upon UV and NIR excitations

Tellurite glasses of TeO2BaF2−REF3 (RE = La, Gd, and Y) co-doped with Er3+/Yb3+ were prepared and investigated comparatively for optical fiber temperature sensors. For this purpose, their thermal and optical properties were examined in detail. The J-O theory was adopted to estimate the transition properties based on absorption spectra. The dominant green emissions were observed in both of the downshifting and upconversion luminescence. The optical temperature sensing abilities based on the FIR of Er3+ green emissions were studied under both of the UV (380 nm) and NIR (980 nm) excitations. Results show that these three tellurite glasses, especially for the TBG glass, should be very qualified for the design of optical fiber temperature sensors under different excitation modes.

Sensitivity-enhanced Tm3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on upconversion emissions

Optical thermometry based on Y3Al5O12 (YAG) single crystal optical fiber with end Tm3+/Yb3+ co-doped is presented. The YAG crystal fiber with end Tm3+/Yb3+ co-doped was grown by laser heated pedestal growth (LHPG) method. Under a 976 nm laser diode excitation, the upconversion (UC) emissions, originating from 3F2,3→3H6 and 3H4→3H6 transitions of Tm3+ ions, were investigated in the temperature range from 333 K to 733 K. Interestingly, the UC emission intensity of 3F2,3→3H6 transition was significantly enhanced with increase of temperature, as compared with the other Tm3+/Yb3+ co-doped materials. The temperature dependence of fluorescence intensity ratio (FIR) of these two emission bands (3F2,3/3H4→3H6) suggests that this doped YAG crystal fiber can be used as a highly sensitive optical thermal probe, which demonstrates a high absolute sensitivity with the maximum value of 0.021 K−1 at 733 K. In addition, due to the compact structure, strong mechanical strength and high thermal stability, such thermal probe may be a more promising candidate for temperature sensor with a high spatial resolution.

Compact and sensitive Er3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on up-conversion luminescence

Compact and sensitive Er3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on up-conversion (UC) luminescence is presented. The thermal probe is a YAG single crystal fiber with end Er3+/Yb3+ co-doped grown by laser heated pedestal growth method. Excited by a 976nm laser diode, the UC fluorescence intensity ratio (FIR) of the Er3+ ions in two emission bands (2H11/2,4S3/2→4I15/2) was investigated in the temperature range from 298K to 723K. The results indicate that the maximum temperature sensitivity is approximately 0.00486K−1 at 577K. Thus, the Er3+/Yb3+ co-doped YAG single crystal fiber has potential application in optical thermometry by the FIR technique. Furthermore, the thermal probe has compact structure and high thermal stability, making it a more convenient and effective optical fiber temperature sensor.

An inexpensive high-temperature optical fiber thermometer

An optical fiber thermometer consists of an optical fiber whose tip is coated with a highly conductive, opaque material. When heated, this sensing tip becomes an isothermal cavity that emits like a blackbody. This emission is used to predict the sensing tip temperature. In this work, analytical and experimental research has been conducted to further advance the development of optical fiber thermometry. An inexpensive optical fiber thermometer is developed by applying a thin coating of a high-temperature cement onto the tip of a silica optical fiber. An FTIR spectrometer is used to detect the spectral radiance exiting the fiber. A rigorous mathematical model of the irradiation incident on the detection system is developed. The optical fiber thermometer is calibrated using a blackbody radiator and inverse methods are used to predict the sensing tip temperature when exposed to various heat sources.

Research of DC Current Transformer Based on Optical Fiber Thermometry

Research of DC Current Transformer Based on Optical Fiber Thermometry

Research of DC Current Measurement Technology Based on Optical Fiber Thermometry

Thin film sensor has the advantages of small size and low cost, which has become a research hotspot in recent years. A measurement system of passive optical fiber DC current sensor based on the thin film sensors is designed in this article. Designs of electric-heating converter, heating-light converter and low-voltage measurement display system are introduced in detail. Experimental results indicate that the general linear correlation between the time constant of fluorescent lifetime and the voltage across the thin film resistor. The feasibility of measurement system is verified via the results of the experiment.

Review on an Advanced High-Temperature Measurement Technology: The Optical Fiber Thermometry

Optical fiber thermometry technology for high-temperature measurement is briefly reviewed in this paper. The principles, characteristics, recent progresses and advantages of the technology are described. Examples of using the technology are introduced. Many blackbody, infrared, and fluorescence optical thermometers are developed for practical applications.

Inversion of spectral emission measurements to reconstruct the temperature profile along a blackbody optical fiber thermometer

A blackbody optical fiber thermometer consists of an optical fiber whose sensing tip is given a metallic coating. The sensing tip of the fiber forms an isothermal cavity, and the emission from this cavity is approximately equal to the emission from a blackbody. Standard two-color optical fiber thermometry involves measuring the spectral intensity at the end of the fiber at two wavelengths. The temperature at the sensing tip of the fiber can then be inferred using Planck's law and the ratio of the spectral intensities. If, however, the length of the optical fiber is exposed to elevated temperatures, erroneous temperature measurements will occur due to emission by the fiber. The results presented in this article show it is possible to use additional spectral measurements to account for emission by the fiber and accurately measure the tip temperature. In addition, the proposed technique can be used to obtain an estimate of the temperature profile along the fiber.

LiCAF crystal-based optical fiber thermometry

Experiments are reported on a LiCAF crystal-based optical fiber thermometer, and results given for the performance over the region from 300 to 550 K for two crystal samples, of different doping levels. The system is simple to implement and offers good measurement potential over this important temperature region.

Ripple Technique; a Novel Non-Contact Wafer Emissivity and Temperature Method for RTP

AbstractA novel wafer temperature and emissivity measurement technique for rapid thermal processing (RTP) is presented. The ‘Ripple Technique’ takes advantage of heating lamp AC ripple as the signature of the reflected component of the radiation from the wafer surface. This application of Optical Fiber Thermometry (OFT) allows high speed measurement of wafer surface temperatures and emissivities. This ‘Ripple Technique’ is discussed in theoretical and practical terms with wafer data presented. Results of both temperature and emissivity measurements are presented for RTP conditions with bare silicon wafers and filmed wafers.

Thermal Effects During Microwave Plasma Sintering of Ceramics

ABSTRACTA variety of ceramic materials have been heated in various microwave excited plasmas at reduced pressures. Temperatures were measured by optical fiber thermometry. Specimen heating was accomplished by direct contact with the plasma, as well as direct coupling withthe microwave energy, although the latter was screened heavily by the plasma. Higher specimen temperatures were achieved in polyatomic gases which have greater reactional enthalpy. In general, insulating materials achieved higher temperatures than semiconducting or covalently bonded materials.

Temperature oscillations in silicon melts

Optical fiber thermometry has been used to study temperature oscillations in silicon melts contained in quartz crucibles of standard design. Fourier analyses of the time-temperature data show the temperature oscillations to be extremely dependent on location in the crucible and crucible rotation speed. A single frequency was observed near the crucible edge at 1 RPM rotation while the temperature fluctuation measured at the crucible center at 8 RPM was composed of over twenty discrete Fourier components. This complex spectrum was the result of combinations of three or four fundamental frequencies which were stable over several crucible rotations. The data suggest that in-situ monitoring of the temperature fluctuations during crystal growth may be useful in improving crystal quality.