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Sensitivity (${S}$) and drive mode are crucial issues for the vertical metal-oxide-semiconductor (MOS) type diode applied in temperature sensing. In this study, experimentally, we indicated that the ${S}$ values of the ${\mathrm {Ni}}_{(\text {50 nm})}$ - ${\mathrm {Au}}_{(\text {100 nm})}$ /Ga2O3/ ${p}$ -Si vertical MOS type diode, using the measured capacitance–voltage (${C}_{\text {m}}$ – ${V}$) outputs, are obtained with a novel drive mode. We applied the constant capacitance mode to drive the silicon thermo-diodes as well as constant current mode, and constant voltage mode, which are known as two different methods in the literature. Meanwhile, the ${S}$ value is 21.2 mV/K at 1 nF. This value is the highest value proven in the literature excepting the cryogenic temperature region, and near room temperature. This study provided an original structure for the silicon thermo-diodes and a novel way to drive them. [ABSTRACT FROM AUTHOR]

We study the influence of thermal expansion and thermo-optic effect on optical properties of finite 1-D three-periodic photonic crystals (PCs) of structure [(ab) $^{N}$ (cd) $^{M}$ ] $^{K}$ composed of four different nonmagnetic dielectric materials ${a}$ , ${b}$ , ${c}$ , and ${d}$. We calculate temperature dependencies and incidence angle dependencies of the transmittivity of TE- and TM-polarized electromagnetic waves, as well as the distribution of energy within these structures. The optimal adjustment of PC bandgap centers for obtaining the desired transmission characteristics of the temperature-governed photonic bandgap structures is found, and the peculiarities of the energy distributions inside the photonic system are investigated. We propose a sensitive thermal polarization TE/TM switch as well as angular and temperature sensors working at the intraband-mode frequencies exploiting temperature effects. [ABSTRACT FROM AUTHOR]

The emergence of planar metamaterials (PrMMs) has opened a gateway to unprecedented electromagnetic (EM) properties and functionality unattainable from naturally occurring materials, thus enabling a family of PrMM based devices. In this paper, a novel class of superconducting (SC) PrMM is presented and a series of THz reflectance spectral responses simulations reveals that these SC PrMM structures portend applications in a variety of temperature sensors, thermo-optical modulators, and magnetic switch devices. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an in-fiber Mach-Zehnder temperature sensor based on a dual-core fiber (DCF) in which one core, working as the sensing arm, is suspended in an embedded fluidic channel filled with silicone oil, while the other one, working as the reference arm, locates eccentrically in the DCF. Temperature variations would change the refractive index of silicone oil infiltrated as well as the effective index of the guided mode in the suspended core, thus shifting the interference spectra. Both experiments and numerical simulations were carried out to characterize the sensor. The spectrum shifts measured experimentally agreed well with the theoretical results. Experimental sensitivity of the sensor using a DCF infiltrated with ~20 cm-long silicone oil was found to be as high as −1.42 nm/°, comparable to those of the SPR fiber sensors and other interferometric sensors. The measuring range of the sensor was more than 120°. The proposed sensor could be easily fabricated with good robustness and stability, which makes the sensor promising for applications such as environment and architecture monitoring. [ABSTRACT FROM AUTHOR]

Due to the unique optical properties and good thermal stability, GeAsSeTe microstructured optical fiber (MOF) offers tremendous opportunity for applications in mid-infrared range (MIR). In this article, we design a CS2-filled GeAsSeTe MOF whose core, inner and outer cladding adopt Ge15As25Se15Te45, Ge20As20Se17Te43 and Ge20As20Se15Te45 glass, respectively. Highly efficient four-wave mixing (FWM) is realized and ultrabroadband optical parametric gain is obtained. By analyzing the central parametric gain bandwidth change with the temperature variation, this CS2-filled GeAsSeTe MOF is proved to be highly sensitive concerning temperature sensing, the sensitivity being as high as 2.32nm/°C from −80°C to 45°C. Such high temperature sensing property have key prominence for developing optical fiber temperature sensor in MIR region based on FWM. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on central parametric gain bandwidth of FWM change in a GeAsSeTe MOF. [ABSTRACT FROM AUTHOR]

A compact U-shaped interferometer with high refractive index (RI) sensitivity based on bent single-mode fiber is proposed and demonstrated experimentally. The sensor is fabricated by roasting a balloon-shaped single-mode optical fiber to form a U-shaped modal interferometer. Since the spectral dips show different sensitivities to both the surrounding RI and temperature, simultaneous measurement of RI and temperature can be achieved by demodulating the shifts of the different resonance dips without cascading additional components. The sensitivity of RI reaches up to −1705.66 nm/RIU in the range of 1.3330-1.3581, which is about 10 times as the reported arts. The proposed compact U-shaped interferometer is a potentially effective sensor for chemical and biological applications where an accurate RI measurement of a temperature-changing liquid is required. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the need for real-time temperature monitoring in battery packs used in automotive applications so to have an accurate estimation of battery life and performances. Advanced energy storage management systems should sense operating and ambient temperature of battery packs in order to implement proper strategies to improve the efficiency of charge and discharge processes and to extend battery life. The proposed evaluation technique is based on an innovative and dynamic circuital model, which allows to accurately represent the functioning of a battery pack (in charge and discharge) in the various operating conditions. Each circuital parameter of the model has a well-defined function which highlights its dependence on temperature, state of charge, state of health and number of cells. The model characterization has been made through tests on different battery sets. A climatic chamber has been used to simulate different operating conditions of ambient temperature. The analysis of the parameters evolution in time has led to the identification of an ideal ambient temperature range for the type of batteries under examination in order to improve their performances over time in terms of energy efficiency and extension of useful life. [ABSTRACT FROM AUTHOR]

A dual parameter optical fiber sensor for temperature and pressure discrimination has been proposed and experimentally realized. A tapered fiber Bragg grating (tapered-FBG) and an extrinsic Fabry–Perot interferometer with a ball shape (ball-EFPI) are the two main sensing structures. The taper is fabricated by elongating it during an arc-discharge provided by the fusion splicer. Then, the femtosecond laser is used to inscribe a first-order Bragg grating in the taper region, adopting the point-by-point direct-writing technique. The ball-EFPI is fabricated using the chemical etching and arc-discharge enlargement method. The test temperature range is 40 °–400°, and the test pressure range is 0–2 MPa on the basis of ambient pressure. Experimental results show that the tapered-FBG has good temperature response while the ball-EFPI is sensitive to pressure. By analyzing the sensitivity matrix, the temperature and pressure discrimination can be achieved using the proposed hybrid sensor. [ABSTRACT FROM AUTHOR]

Though the strain characteristics of fiber Bragg gratings (FBGs) inscribed in perfluorinated graded-index (PFGI) polymer optical fibers (POFs) have been reported, their temperature characteristics have not yet been detailed. In this paper, we experimentally investigate the temperature dependence of the Bragg wavelength of a PFGI-POF-FBG. With the increasing temperature, each peak of the FBG-reflected spectrum shifted to longer wavelength with different coefficients. The temperature coefficient of one of the clearest peaks was 0.09 nm/°C, which was eight times larger than those of FBGs in silica single-mode fibers and almost the same as those of FBGs in polymethyl methacrylate POFs. A temperature-independent but strain-dependent peak was also observed, which indicates the potential of discriminative sensing of strain and temperature. [ABSTRACT FROM AUTHOR]

This paper presents the development of a wireless low power reconfigurable self-calibrated multi-sensing platform for gas sensing applications. The proposed electronic nose (EN) system monitors gas temperatures, concentrations, and mixtures wirelessly using the radio-frequency identification (RFID) technology. The EN takes the form of a set of gas and temperature sensors and multiple pattern recognition algorithms implemented on the Zynq system on chip (SoC) platform. The gas and temperature sensors are integrated on a semi-passive RFID tag to reduce the consumed power. Various gas sensors are tested, including an in-house fabricated $4\times 4$ SnO2based sensor and seven commercial Figaro sensors. The data is transmitted to the Zynq based processing unit using a RFID reader, where it is processed using multiple pattern recognition algorithms for dimensionality reduction and classification. Multiple algorithms are explored for optimum performance, including principal component analysis (PCA) and linear discriminant analysis (LDA) for dimensionality reduction while decision tree (DT) and k-nearest neighbors (KNN) are assessed for classification purpose. Different gases are targeted at diverse concentration, including carbon monoxide (CO), ethanol (C2H6O), carbon dioxide (CO2), propane (C3H8), ammonia (NH3), and hydrogen (H2). An accuracy of 100% is achieved in many cases with an overall accuracy above 90% in most scenarios. Finally, the hardware/software heterogeneous solution to implementation PCA, LDA, DT, and KNN on the Zynq SoC shows promising results in terms of resources usage, power consumption, and processing time. [ABSTRACT FROM PUBLISHER]

In this paper, a fiber-optic sensing interrogation system for simultaneous measurement of temperature and transversal loading based on a single-passband RF filter has been proposed and experimentally demonstrated. This sensing interrogation system consists of a fiber Mach–Zehnder interferometer (FMZI) as the sensing device and a dispersive medium. The FMZI also acts as the spectrum slicer to induce continuous sampling, which results in the single-passband frequency response together with the dispersive medium. Two arms of the FMZI are used to measure the temperature and transversal loading respectively. The temperature change on one arm introduces the variation of fiber refractive index, which will change the central frequency of the RF filter’s passband, while the transversal loading induces the change of polarization state of the light, and thus, the amplitude of the RF filter’s passband will be changed accordingly. By tracking the central frequency and amplitude changes of the passband, temperature, and transversal loading can be monitored simultaneously. With the proposed fiber-optic sensing interrogation system, the temperature and transversal loading variation-induced optical spectra changes can be converted to the variation of frequency and amplitude of the RF filter’s passband in electronic domain, which greatly facilitates the measurement. [ABSTRACT FROM PUBLISHER]

Localized temperature sensing and control on a micron-scale have diverse applications in biological systems. We present a micron-sized hydrogel pillar array as potential temperature probes and actuators by exploiting sensitive temperature dependence of their volume change. Soft lithography-based molding processes were presented to fabricate poly N-isopropyl acrylamide (p-NIPAAm)-based hydrogel pillar array on a glass substrate. Au nanorods as light-induced heating elements were embedded within the hydrogel pillars, and near-infrared (NIR) light was used to modulate temperature in a local area. First, static responses of the micro-pillar array were characterized as a function of its temperature. It was shown that the hydrogel had a sensitive volume transition near its low critical solution temperature (LCST). Furthermore, we showed that LCST could be readily adjusted by utilizing copolymerizing with acrylamide (AAM). To demonstrate the feasibility of spatiotemporal temperature mapping and modulation using the presented pillar array, pulsed NIR light was illuminated on a local area of the hydrogel pillar array, and its responses were recorded. Dynamic temperature change in water was mapped based on the abrupt volume change characteristics of the hydrogel pillar, and its potential actuation using NIR light was successfully demonstrated. Considering that the structure can be arrayed in a two-dimensional pixel format with high spatial resolution and high sensitive temperature characteristics, the presented method and the device structure can have diverse applications to change and sense local temperatures in liquid. This is particularly useful in biological systems, where their physiological temperature can be modulated and mapped with high spatial resolution.

This paper explores the near infrared (NIR) to visible frequency upconversion emissions in the Er3+−Tm3+−Yb3+ tri-doped Gd2O3 phosphors prepared by the combustion technique. The cubic phase formation and crystalline structure of the prepared materials has been examined with the help of X-ray diffraction study. The multicolour upconversion emission capability of the prepared materials has been confirmed under the excitation with 980-nm NIR laser source. The relative intensity variation corresponding to the transitions from the thermally coupled energy levels ( ^2\textH11/2 , ^4\textS3/2 ) to the ground level ( ^4\textI15/2 ) of Er3+ ions with pump power and temperature has been studied to investigate the optical temperature sensing ability of the prepared material. The maximum sensor sensitivity of the synthesized material reaches the value 0.0073 \textK^-1 at 443 K. The laser-induced heating capacity of the prepared material caused by laser excitation at different pump powers has been analyzed. The observed results support the utility of the prepared materials in optical temperature sensing and laser-induced heating along with additional capability for being used in making NIR to visible upconverter. [ABSTRACT FROM PUBLISHER]

Chip-based microheaters have been widely used in many applications, including gas sensors, flow meters, mass sensors, and polymerase chain reaction chambers, where accurate monitoring of temperature is critical. The temperature measurement is conventionally done with the aid of a separate sensor, which may add to the cost and inaccuracy. In this paper, a built-in temperature sensing method is provided for the microheaters. The resistor-based microheater relies on Joule heating mechanism and its resistance is dependent upon its own body temperature, implying that the microheater has an inherent temperature sensing mechanism. It is found that an intermittent temperature sampling in the middle of the heating cycle does not disturb the body temperature if the temperature sampling voltage and pulsewidth are sufficiently low and short, respectively. The built-in temperature sensing is attributed to the electrical time constant being few orders of magnitude smaller than the thermal time constant. The temperature estimation results using the built-in method show excellent agreement with the benchmark measurements from an infrared pyrometer. [ABSTRACT FROM PUBLISHER]

We present a fiber sensing for temperature with two different mode interferences. The sensor consists of a single mode-multimode-single mode (SMS) fiber with a specifically designed and synthesized thermo-optic polymer cladding, forming a leaky mode fiber interferometer and a guided one at different temperatures. A maximum temperature sensitivity of 1.4 dB/°C below 61°C and of 15 nm/°C above 72°C have been achieved. The high temperature sensitivity is mainly attributed to the high thermo-optic coefficient of the polymer cladding. The phenomenon of the fiber temperature sensing around the transformation point can be observed and studied using the proposed fiber sample. It is found that the SMS fiber sensor is more sensitive to temperature for both of the mode interferences when the refractive index (RI) of the polymer is closer to that of the multimode fiber core, and the measurement range is relatively wide. [ABSTRACT FROM PUBLISHER]

In this paper, inexpensive single-mode silica optical fibers were interrogated with Luna Innovations' optical backscatter reflectometer to perform distributed temperature measurements at temperatures up to 1000 °C. Measurements of the Rayleigh backscattered signal were taken continuously to determine the amount of light that is backscattered as a function of temperature and position along the length of the fiber. These data were post-processed to determine the spectral shift in the Rayleigh backscatter signature. The spectral shift data were then calibrated to a change in temperature. This paper determines an upper operational temperature limit of 650 °C for the distributed measurement technique based on Rayleigh backscatter using Corning's SMF-28e+ commercially available single-mode fiber. [ABSTRACT FROM PUBLISHER]

Smart materials with integrated sensing capabilities are now ubiquitous in many structures and devices manufactured from composite materials and they offer enhanced safety, reliability and efficiency in such smart devices. This paper explores the application of embedded sensors to components manufactured using additive layer manufacturing (ALM) technology. ALM offers the ability to create physical parts with little or no restriction in shape and complexity. In this paper, optical fiber sensors incorporating fiber Bragg gratings are embedded inside a component made by, and during a powder-bed-based, layer-by-layer, additive manufacturing process. A commercial EOS P730 system is used, where a laser is employed to sinter the polymeric powder into a 3D component. The fiber embedding approach is based upon insertion of a “fiber-carrier” component, which replaces a removable “place-holder” component during an interruption of the ALM build process. Tensile test specimens fabricated this way are subjected to extended cyclic tensile loading trials at low strain levels of up to 580 \mu\varepsilon. The test specimens demonstrate stable and reproducible responses over a period in excess of 720 days and 311000 load cycles. Polyimide and acrylic jacketed fibers are trialled, and the resulting deformations of the component through internal stresses depending on the fiber jacket type are discussed. [ABSTRACT FROM PUBLISHER]

A modal interferometer made of a short ethanol-filled photonic crystal fiber (PCF) combined with a fully collapsed splicing with single-mode fibers (SMFs) is proposed for temperature measurement. Two fully collapsed splicing regions between the ethanol-filled PCF and SMFs excite and recombine two interfering modes in the ethanol-filled PCF. The interference spectrum of the ethanol-filled PCF is more sensitive to temperature than that of original PCF. By monitoring one peak wavelength shift of the ethanol-filled PCF modal interference spectrum, the temperature sensitivity reaches up to -0.35 nm/°C for a 3.25-cm long ethanol-filled PCF. [ABSTRACT FROM PUBLISHER]

A new scheme of highly birefringent fiberized slot waveguide (FSW) by post-processing a non-birefringent circular microfiber is proposed for polarimetric interference sensors with ultrasmall sensor heads (tens of micrometers). The different sensing properties of an FSW polarimetric interferometer based on a typical fiber loop mirror are investigated and discussed in detail for refractive index, temperature, and strain measurement. The sensitivity can achieve a high level of >;5×104 nm/refractive index unit (RIU), >;5 nm/°C, and ~1 pm/με for refractive index, temperature, and strain sensing, respectively. Moreover, its strain sensitivity has a large tuning range from negative to positive, and can be used as an ultracompact and highly efficient strain compensator. Together with its high birefringence, unique geometry, and extremely small size, FSW presents wide potential applications in physical, biological and/or chemical sensing areas. [ABSTRACT FROM PUBLISHER]

This paper presents a novel approach to better reducing the dimensions of sensor packages for specific applications to enable the simultaneous measurement of strain and temperature using fiber Bragg grating (FBG)-based sensors. This approach is demonstrated through comparing three packaging designs, in which there is either a nonuniform height or width to vary the response of two co-located FBGs to strain and temperature. In this way, the measurement of the shift in their respective Bragg wavelengths will allow the accurate determination of both the strain and temperature from their dissimilar strain and temperature coefficients. In addition to providing the necessary protection for the sensors, this type of packaging design also allow better control over the differences between the coefficients thus, in turn, maximizing the sensitivity to which strain and temperature values can be determined. [ABSTRACT FROM PUBLISHER]

A low-cost high-resolution wavelength-division-multiplexing (WDM) interrogation system operating around 800 nm region with operational bandwidth up to 60 nm and resolution of 12.7 pm utilizing a tilted fiber Bragg grating (TFBG) and a CCD-array detector has been implemented. The system has been evaluated for interrogating fiber Bragg grating based strain, temperature sensors, giving sensitivities of 0.59 pm/muepsiv and 5.6 pm/degC, which are in good agreement with previously reported values. Furthermore, the system has been utilized to detect the refractive index change of sample liquids, demonstrating a capability of measuring index change as small as 10-5. In addition, the vectorial expression of phase match condition and fabrication of TFBG have been discussed. [ABSTRACT FROM PUBLISHER]

We have successfully demonstrated a one-step laser process of fabricating fiber Bragg grating arrays directly through fiber buffer. A new polysiloxane-based buffer provides high 244-nm transmission and showed no degradation due to UV irradiation or thermal annealing as verified by Weibull analysis of tension tests. The FBG array can withstand over 400-kpsi tension tests and 220degC temperature. The spectral quality of the FBG is compatible with the FBGs currently used by the sensing industry and, therefore, can be interrogated with existing instruments. The laser fabrication process is robust with no coating, stripping, or recoating required [ABSTRACT FROM PUBLISHER]

Sensitive and versatile evanescent wave-sensing systems featuring polished optical fiber-based sensor designs with low-cost light sources have been developed for temperature, relative humidity, and pH measurements. The work herein contained describes the fabrication of three types of sensors based on standard silica, single-mode fibers previously subjected to a lateral polishing of the cladding. Temperature sensing through oils whose refractive index varied linearly with temperature showed applicability with up to 5 dB/°C for a 5° range. Polyvinyl alcohol films on the fibers showed almost 10-dB linear variation from 70% to 90% relative humidity. Sol-gel trapped dyes as thin films on the polished surface were capable of performing 15-dB output variation (although not linearly) for pH ranging from 2 to 11. [ABSTRACT FROM PUBLISHER]