Er3+/Yb3+/Ho3+ tri-doped no-core fiber temperature sensor based on fluorescence intensity ratio technology: towards high stability and accurate measurements.

In this paper, the green upconversion (UC) fluorescence emission from E r 3+/Y b 3+/H o 3+ tri-doped tellurite glass is investigated for temperature sensing. The doping of H o 3+ ions not only enhances the chance of energy level transition but also avoids the influence of the thermal effect caused by the proximity of 2 H 11/2 and 4 S 3/2 energy levels. The luminescence characteristics at different Y b 3+ and H o 3+ ion concentration doping molar ratios were investigated, and the strongest luminescence characteristics were exhibited when the Y b 3+ ion concentration was at 5 mol% and H o 3+ at 0.2 mol%. Based on this, a tri-doped T e O 2-Z n O-B i 2 O 3 (TZB) no-core fiber was fabricated and connected with multimode fibers (MMFs) to form a temperature sensor. The temperature sensing performance of the tri-doped TZB temperature sensor was evaluated in detail over the temperature range of 255-365 K. The repeatability and stability of the temperature sensor was experimentally verified. The E r 3+/Y b 3+/H o 3+ tri-doped sensor can be used for noninvasive optical temperature sensing in the fields of environmental monitoring, biological sensing, and industrial process temperature control, etc.

Transmissive fluorescent temperature sensor based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber for real-time thermal monitoring of motors using the FIR technique.

In this paper, we fabricate a transmissive fluorescent temperature sensor (TFTS) that based on Er3+/Yb3+/Mo6+ tri-doped tellurite fiber, which has the advantages of compactness and simplicity, corrosion resistance, high stability and anti-electromagnetic interference. The doping of Mo6+ ions will enhance the up-conversion (UC) fluorescence emission efficiency of Er3+ ions, thus improving the signal-to-noise ratio of TFTS. Using the fluorescence intensity ratio (FIR) technique, the real-time thermal monitoring performance of TFTS is evaluated experimentally. Apart from good stability, its maximum relative sensitivity is 0.01068 K-1 at 274 K in the measured temperature range. In addition, it is successfully used to monitor the temperature variation of the stator core and stator winding of the motor in actual operation. The results show that the maximum error between the FIR-demodulated temperature and the reference temperature is less than 1.2 K, which fully confirms the effectiveness of the TFTS for temperature monitoring. Finally, the FIR-based TFTS in this work is expected to provide a new solution for accurate and real-time thermal monitoring of motors and the like.

Multimode interferometric sensor based on the no-core tellurite optical fiber for cryogenic temperature detection.

In this paper, a no-core tellurite optical fiber (NCTOF)-based sensor was proposed for cryogenic temperature detection in refrigeration process. The ultraviolet adhesive (UVA) dual-curing method was operated to stablish a sandwich-like composite structure, in which a section of NCTOF was compactly sandwiched between two segments of silica fiber to form multimode interference. The temperature sensing characteristics in cryogenic range were experimentally investigated by monitoring the transmission spectral movement, where a high sensitivity of 105.6 pm/°C was achieved in the range of -20-0 °C and 51.6 pm/°C in the range of -20-25 °C. The excellent performance was consistent with the simulation analysis. The maximum repeatability standard deviation and stability wavelength error of the sensor are 0.9799 pm/°C and 0.1676 nm, respectively. To the best of our knowledge, this is the first report on using tellurite optical fibers for cryogenic temperature detection, and the UVA dual-curing method provides a reliable solution for the integration and practical application of tellurite optical fiber. The proposed sensor is simple in structure, easy in fabrication, low in cost and excellent in performance. It can be expected to be used in food refrigeration, air-conditioning engineering, medical and health, industrial production, etc.

Plug-in tip sensor based on upconversion fluorescence in Er3+/Yb3+ co-doped tellurite glass for thermal monitoring of a miniature winding coil.

We demonstrate a plug-in tip sensor with a maximum cross section diameter of only 1 mm for real-time thermal monitoring of a high-density miniature winding coil, which can meet the miniaturization development needs of electromagnetic actuators. Due to the high upconversion luminescence efficiency, tellurite glass with an optimized Er3+/Yb3+ doping ratio is adhered to the end face of silica fiber for a temperature-sensitive tip. Temperature information is demodulated using the fluorescence intensity ratio technique, yielding a nonlinear response with R2 up to 0.9978. Within a wide temperature range of 253.55-442.45 K, the tip sensor exhibits good repeatability, excellent stability, high sensitivity of 52.7 × 10-4 K-1, small absolute error within ±1 K, and fast time response of 2.03 s. It has been successfully proven to be a miniaturized device with strong anti-interference ability for the health management of high-density winding coils.