Simultaneous Measurement of Refractive Index and Temperature Using a Hybrid Fiber Bragg Grating/Long-Period Fiber Grating Configuration

Abstract

A fiber optic sensing system for simultaneous measurement of refractive index and temperature, based on a hybrid fiber Bragg grating/long-period grating arrangement is described. The experimental results show that this setup has a good performance in terms of linearity and sensitivity, the ratiometric output changes 4%/0.001 RIU and 3.6%/°C, respectively. The sensor resolution for the refractive index is ≈2 × 10^?5 RIU. The simultaneous measurement of the refractive index and temperature was demonstrated. The sensing configuration has the ability to be read-out in reflection and works in the telecommunications window.     

Remote Temperature Sensor Based on the Up-Conversion Fluorescence Power Ratio of an Erbium-Doped Silica Fiber Pumped at 975 nm

Abstract

This article presents experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the interval from 20°C to 200°C. The sensor is based on the change in the fluorescence intensity ratio of two spectral bands as a function of temperature. The green fluorescence signal was generated by up-conversion processes in the erbium-doped fiber pumped at 975 nm. A radiometric analysis was applied to the erbium-doped fiber to evaluate its performance as a temperature sensor, and the results from this analysis were compared against other rare-earth-doped fiber sensors that utilize the intensity ratio technique.     

Analysis of multimode BDK doped POF gratings for temperature sensing

We report a temperature sensor based on a Bragg grating written in a benzil dimethyl ketal (BDK) doped multimode (MM) polymer optical fiber (POF) for the first time to our knowledge. The thermal response was further analyzed in view of theory and experiment. In theory, with the order of the reflected mode increasing from 1st to 60th order, for MM silica fiber Bragg grating (FBG) the temperature sensitivity will increase linearly from 16.2 pm/°C to 17.5 pm/°C, while for MM polymer FBG the temperature sensitivity (absolute value) will increase linearly from ?79.5 pm/°C to ?104.4 pm/°C. In addition, temperature sensitivity of MM polymer FBG exhibits almost 1 order larger mode order dependence than that of MM silica FBG. In experiment, the Bragg wavelength shift will decline linearly as the temperature rises, contrary to that of MM silica FBG. The temperature sensitivity of MM polymer FBG is ranged from ?0.097 nm/°C to ?0.111 nm/°C, more than 8 times that of MM silica FBG, showing great potential used as a temperature sensor.     

Theoretical and Experimental Study of a Code-Division Multiplexing Fiber Bragg Grating Sensor System

Abstract

A novel scheme for a code-division multiplexing based fiber Bragg grating sensor system is theoretically analyzed and experimentally demonstrated. The results show that the proposed scheme enables an improved signal-to-noise ratio performance compared with the time-division multiplexing method and that spontaneous–spontaneous beating noise should be included in the analysis to avoid overestimation. The simple and effective setup provides a competitive approach for using fiber Bragg grating sensors in practical application systems.     

An all-fiber high resolution fiber grating concentration sensor

An all-fiber high resolution optical fiber grating concentration sensor has been studied theoretically and experimentally. A long period grating is used as the sensor head and a wavelength matched fiber Bragg grating is used as an interrogator to convert wavelength into intensity encoded information for interrogation. A concentration resolution of 0.104 g/L for NaCl solution is realized in experiment. The all-fiber sensor system, with the sensor head and the interrogator being all optical fiber components, is suitable for far-distance monitoring. The sensor system is with multifunction and can be used for temperature monitoring. A temperature resolution of 0.013 °C has realized in experiment.     

Multiplexing fiber bragg grating sensors

Abstract

Bragg reflection gratings and out-coupling taps for sensors can be written holographically within the core of many commercial fibers available today. The gratings appear to be permanent and have been tested to temperatures in excess of 500°C. Quasi-distributed temperature, strain, pressure, chemical, and interferometric sensors can be made with the wavelength selective, reflection gratings, and taps. The fiber gratings, and the different types of sensors they can make, conveniently lend themselves to (wavelength-division multiplexing) WDM, (time-division multiplexing) TDM, and (frequency-division multiplexing) FDM types of multiplexing schemes. Instrumentation to detect the multiple sensors and measure their spectral shift for localized and quasi-distributed sensing is currently under development.     

Simultaneous Measurement of Temperature and Refractive Index of Liquid Using Cladding-Etched Double-Core Fiber Bragg Grating

Abstract

This study proposed and demonstrated a fiber Bragg grating sensor for simultaneous detection of the temperature and refractive index of a liquid. The fiber Bragg grating is composed of three index layers: an inner core, an outer core, and a cladding. The cladding was etched for evanescent wave coupling between the outer core mode and an external liquid. The Bragg wavelength of the inner core mode is used for obtaining temperature data, while the refractive index for the liquid was determined by using the difference between the Bragg wavelength of the inner core mode and that of outer core mode.     

光纤Bragg光栅倾角传感器的标定与不确定度分析

实现光纤Bragg光栅倾角传感器的静态的测试和性能分析。设计了一种量程为5°的倾角传感器标定装置,对其进行校准实验。通过对光纤光栅解调仪的中心波长差和标定装置产生的倾角值进行最小二乘法拟合,求出静态标定系数,并对倾角传感器标定装置的不同不确定度分量进行分析以求出合成不确定度。实验结果表明,光纤传感器的灵敏度为0.17343nm/(°),线性度为99.993%,重复性误差为0.0552%,标定装置的合成不确定度为8.606×10-2°。     

Grating-Outcoupled Radiation in Second-Order Fiber Bragg Gratings

Abstract

The experimental results of the radiation for second-order fiber Bragg gratings, which are made of a single-mode photosensitive fiber (PS-1500; Fiber-Core Corp.) and a single-mode fiber (SMF-28; Corning Inc.), by a phase mask writing fabrication technique are explored. For PS-1500 fiber Bragg gratings, the maximum radiation efficiency of ?23.5 dB at resonance λ = 1,539.34 nm with a very narrow bandwidth (about 0.02 nm) are measured from a 10-mm-diameter photo-detector, while for SMF-28 fiber Bragg gratings, the maximum radiation efficiency is ?34.6 dB (λ = 1,538.03 nm) with a bandwidth of 0.06 nm. The total efficiencies of the radiation are about ?16.8 dB for PS-1500 fiber Bragg gratings and ?28.1 dB for SMF-28 fiber Bragg gratings.     

High pressure 1D and 2D NMR experiments on model biomembranes

Abstract

We developed a high-pressure high-resolution probe for NMR experiments on biological systems which enabled us to study the phase behaviour of model biomembranes by 1D and 2D NMR experiments at temperatures up to 65°C and at pressures up to 3000 bar.     

Microwave sea return at moderate to high incidence angles

Abstract

Bragg scattering is widely recognized as the dominant mechanism by which the ocean surface backscatters microwave radiation, but efforts to identify other, non-Bragg sources of this scattering have been pursued for many years. Non-Bragg backscattering from the sea surface is known to occur at incidence angles close to 0° and 90°. In this paper Bragg scattering is shown to explain most features of sea surface backscatter for incidence angles between about 20° and 80°, except when it predicts very small mean cross sections. The often-quoted evidence for non-Bragg scattering in this incidence angle range is that σ _o (HH) is occasionally found to be larger than or equal to σ _o (VV) for short integration times. We show that because of fading this is not evidence of non-Bragg scattering. For incidence angles up to about 50°, standard Bragg/composite surface scattering theory yields probabilities of finding σ _o (HH)>σ _o (VV) that are only slightly smaller than those found experimentally. As the incidence angle increases, greater differences between theoretical and experimental probabilities are found. The addition of Bragg scattering from bound, tilted waves brings theory into excellent agreement with experiment at incidence angles near 45° but still cannot account adequately for the probability of σ _o (HH)>σ _o (VV) or observed σ _o (HH) cross sections at higher incidence angles. We show that the addition of a small, non-Bragg cross section that is independent of the incidence angle and polarization, brings simulated cross sections and probability distributions into good agreement with data. A possible source of this small, non-Bragg sea return is sea spray just above the air/sea interface.     

A Stable and Compact Optical Module for Fiber-Optic Gyroscope Application

Abstract

This article introduces a new design for a bi-directional optical sub-assembly for fiber-optic gyroscope applications that integrates a super-luminescent light-emitting diode, a photodiode, a beam splitter, an isolator, a fiber receptacle, and a thermal electric cooler. It is less than 1.5 cm in diameter and 2.5 cm in height. As chip temperature was kept at 30°C under environment temperature of ?35°C, 25°C, and 75°C, the bi-directional optical sub-assembly reached stability at a center wavelength of 1,539 nm and a wavelength shift of 1.5 nm. A 3D simple model with the finite-element method was used to analyze thermal performance.     

Temperature self-compensation fiber-optic pressure sensor based on fiber Bragg grating and Fabry–Perot interference multiplexing

A high performance multiplexed fiber-optic sensor consisted of diaphragm-based extrinsic Fabry–Perot interferometer (DEFPI) and fiber Bragg grating (FBG) is proposed. The novel structure DEFPI fabricated with laser heating fusion technique possesses high sensitivity with 5.35 nm/kPa (36.89 nm/psi) and exhibits ultra-low temperature dependence with 0.015 nm/°C. But the ultra-low temperature dependence still results in small pressure measurement error of the DEFPI (0.0028 kPa/°C). The designed stainless epoxy-free packaging structure guarantees the FBG to be only sensitive to temperature. The temperature information is created to calibrate the DEFPI's pressure measurement error induced by the temperature dependence, realizing effectively temperature self-compensation of the multiplexed sensor. The sensitivity of the FBG is 10.5 pm/°C. In addition, the multiplexed sensor is also very easy to realize the pressure and the temperature high-precise high-sensitive simultaneous measurement at single point in many harsh environmental areas.     

活塞式菱形结构光纤布喇格光栅渗压传感器

为了适应矿井、大坝对渗压监测的需要,提出一种活塞和菱形传压结构相结合的光纤布喇格光栅渗压传感器,活塞把测试压力传递到菱形传压结构,菱形传压结构拉动其上下对称连接的弹性钢片,导致粘贴在弹性钢片上的光纤布喇格光栅中心波长产生变化.利用有限元方法在500kPa的测试环境中对顶角分别为90°、110°、130°、150°情况下菱形传压结构的应力特性进行分析,根据仿真参量研制了渗压传感器,并对该传感器进行了压力标定试验和温度补偿试验.实验结果表明:传感器对渗压的灵敏度为2.04nm/MPa,拟合度为0.997,重复性为0.9%,两个测压光栅温度灵敏度分别为0.023 33nm/℃、0.021 68nm/℃,温补光栅为0.009 916nm/℃.     

A non-contact FBG vibration sensor with double differential temperature compensation

This paper has presented a non-contact fiber Bragg grating (FBG) vibration sensor with double differential temperature compensation. Two FBGs and two states of the sensor have been employed to achieve double differential temperature compensation. Based on magnetic coupling and FBG sensing principle, it can be used to realize non-contact measurement of vibration of the rotating shaft. Experimental results show that the working band ranges are within 0–150 Hz; the sensitivity is ?0.67 pm/µm, and the linearity is 3.87 % within a range of 2–2.6 mm. The fitting equation of temperature compensation which is caused by structural inflation can be expressed as: Δλ ₁′ ? Δλ ₂′ = 1.51 × T ? 32.97. When used to amend a temperature error, the sensor’s temperature error will be reduced to 1.19 % in the range of 25–60 °C.     

Temperature characteristics of a core-mode interferometer based on a dual-core photonic crystal fiber

A core-mode Fabry–Perot (FP) interferometer is constructed by using a dual-core photonic crystal fiber (DCPCF). The FP cavity is formed by a single piece of DCPCF, which can also serve as a direct sensing probe without any additional components. We theoretically and experimentally studied its temperature responses in the range of 40–480 °C. The temperature sensitivity is 13 pm/°C which matches the theoretical results. Since the temperature sensitivity of the proposed sensor is independent on cavity length, precise control of the length of FP cavity or photonic crystal fiber is not required. The sensor size can be as short as 100–200 μm, and its fabrication only involves splicing and cleaving, which make the sensor production very cost-effective. The proposed FP interferometric sensor based on a DCPCF can find applications in high-temperature measurement especially those that need accurate point measurement with high sensitivity.     

Structural and Morphological Changes of Carbon Fiber Surfaces,Produced via Sputtering by Noble Gas Ions

SEM, laser goniophotometry, and Raman spectroscopy are used to analyze a modification of the carbon PAN fiber shell of KUP-VM composite upon irradiation with 30 keV Ne⁺ and Ar⁺ ions at normal incidence and temperatures of RT to 600°C. It is found that the formation of corrugated submicron structures in the composite upon irradiation at elevated temperatures (≥125°C for neon and ≥250°C for argon) displays certain features at temperatures of 400–500°C. The corrugated faces’ angles of inclination and the fraction of the corrugated structure on the fiber surface at these temperatures are minimal. Together with regularities established earlier, the observed patterns allow us to relate ion-induced corrugation to anisotropic radiation- induced plastic processes of dimensional changes in carbon materials affected by ion sputtering of their surfaces.     

SPECTROSCOPIC STUDY ABOUT THE KINETICS OF THE ANTHOCYANIN PIGMENTS EXTRACTION DURING THE MACERATION OF CHERRIES IN LIQUOR

ABSTRACT

An experimental study of the effect of temperature on the kinetics of anthocyanin pigments extraction during the maceration of cherries (Prunnus avium) into a hard spirit is reported. The analytical method used was UV-Vis spectrophotometry. The initial extraction rate showed an Arrhenius-type dependency, with an apparent energy activation of 18.7±1.2 kcal/mol. Furthermore, a study about the evolution of the color (from colorless to red-orange) during the soaking process was made by calculating the CIE tristimulus values (X, Y, Z) for illuminant C, until to reach the apparent stabilization of color, what occurs after about two weeks for temperatures of 5°C and 23°C, whereas it happens after about four weeks for the other studied temperature (30°C).     

New plastic optical fiber using polycarbonate core and fluorescence-doped fiber for high temperature use

This article describes the development of a plastic optical fiber composed of a polycarbonate core with a glass transition temperature of 150°C, and a cladding of newly developed poly-4-methyl penten-1, which softens at 173°C. This cladding is suitable for use at temperatures up to 130°C. The minimum optical attenuation is 0.8 dB/m at 765 nm in the near-infrared region. The cause of the attenuation of the PC-core fiber was analyzed and the intrinsic loss limit was estimated to be 0.4 dB/m at 765 nm. The fiber has excellent characteristics, including thermal stability up to 125°C, high flexibility, high strength, and self-extinguishing properties.

The polycarbonate core fiber, doped organic fluorescing materials, has also been developed for automotive uses such as light guide and illuminator. Light can be transmitted through this fiber with incident optical beam perpendicular to the fiber as well as the beam parallel to the fiber.