Simultaneous Measurement Of Multiple Parameters Research Articles

Simultaneous measurement of refractive index and temperature based on tapered no-core fiber cascaded with a fiber Bragg grating

A Mach-Zehnder interference fiber-optic sensor for simultaneous measurement of temperature and refractive index (RI) is proposed and fabricated. In the sensing structure, no-core fiber (NCF) is cascaded with fiber Bragg grating (FBG), two enlarged tapers between NCF and the single-mode fiber serve as the light coupler, and the shrinked taper between two NCFs is used to enhance the interference effect. The different diameter influence of the shrinked taper on the sensing performance of RI and temperature has been evaluated, and the optimum diameter has been obtained. By monitoring the wavelength shift of FBG and the interference dip in the transmission spectra, the simultaneous measurement of temperature and RI is achieved. The maximum sensitivities of the attenuation peak to RI and temperature are 201.7157 nm/RIU and 87.4 pm/°C, respectively. The sensitivities of FBG to RI and temperature are 80.6 pm/RIU and 13.5 pm/°C, respectively. The transformation matrix has also been given. Own to the simple fabrication and high sensitivity, the sensor has the potential application in simultaneous measurement of multiple parameters.

Construction of multiple anti-resonant light guidance mechanisms in a hollow-core fiber structure for simultaneous measurement of multiple parameters.

The construction of multiple light guidance mechanisms in a hollow-core fiber (HCF) structure is a popular way to realize the simultaneous measurement of multiple parameters. In this work, a partial coating method to excite multiple anti-resonant light guidance mechanisms (ARLGMs) in an HCF structure for the simultaneous measurement of multiple parameters is proposed. As an example, a double ARLGM based on a partially polyimide (PI)-coated HCF structure for the simultaneous measurement of relative humidity (RH) and temperature is demonstrated theoretically and experimentally. The dip (dip II) produced by the PI-coated HCF section shifts linearly with surrounding RH changes with a sensitivity of circa 58.6 ± 0.77 pm/%RH, while the dip (dip I) produced by the bare HCF section (with an air coating layer) is insensitive to RH changes. In addition, both types of dips have linear responses to temperature variations, with similar sensitivities of ∼ 17 pm/°C. Hence, the proposed sensor structure can be used as an RH sensor that is also capable of compensating for local temperature fluctuations. More importantly, the simultaneous measurement of multiple parameters (such as biomarkers) is possible using the proposed method provided the proper sensing materials are partially coated onto the HCF surface.

Research and application of multi-channel SPR sensor cascaded with fiber U-shaped structure

Multi-channel fiber SPR sensor can realize the detection of multiple analytes and specific binding detection. In this paper, by controlling the curvature radius of U-shaped structure to adjust the working band of the sensor, a multi-channel fiber SPR sensor cascaded with fiber U-shaped structure was proposed and demonstrated. By employing the U-shaped structure with curvature radius of 1 mm and 5 mm, the dual-channel fiber SPR was fabricated and tested, the refractive index sensitivity is 1414 nm/RIU and 3687 nm/RIU, respectively. By using this dual-channel fiber SPR, glucose and sucrose were detected at the same time, the detection sensitivity is 0.172 nm/μg/ml and 0.738 nm/mg/ml, respectively. The proposed multi-channel fiber SPR sensor based U-shaped structure has the advantages of simple structure, convenient operation, and can be directly inserted into a narrow space for measurement, which has practical value for the simultaneous measurement of multiple parameters.

Multiparameter Sensing Based on Tunable Fano Resonances in MIM Waveguide Structure with Square-Ring and Triangular Cavities

In this paper, a metal–insulator–metal (MIM) surface plasmon waveguide structure is proposed and numerically investigated. It is composed of a square-ring cavity with a silver baffle, an isosceles triangle cavity, and a bus waveguide with a silver baffle. The results show that the structure can produce triple Fano resonances that can be independently tuned by changing the structural parameters. The detection of refractive indexes at different positions in the structure was also accomplished, with a maximum sensitivity of 2259.56 nm/RIU. On the basis of this, the simultaneous measurement of multiple parameters (plasma concentration and glucose concentration) was performed. The numerical simulation results are beneficial to the applications of MIM waveguide structure in nanosensing and biosensing with time-sharing or simultaneous measurement of multiple parameters.

On-Fiber Multiparameter Sensor Based on Guided-Wave Surface Plasmon Resonances

We report an ultracompact on-fiber multiparameter sensor that employs multiple guided-wave surface plasmon resonances (GWSPRs) and machine learning based signal processing. The sensor structure entails a gold plasmonic crystal cavity covered with a planar dielectric waveguide on the end-face of a single-mode fiber. Incident light on the gold gratings of the plasmonic crystal cavity excites surface plasmon resonances, which are coupled into the waveguide and induce multiple, high-Q GWSPRs. Due to the difference in the field distributions of these resonance modes, the resonance dips in the sensor reflection spectrum have distinctive responses to external stimuli, which enables simultaneous measurement of multiple parameters. To enhance the sensing accuracy, a neural network model is used to demodulate the sensor responses. A proof-of-concept sensor using a UV-curable polymer as a waveguide material is demonstrated for simultaneous measurement of temperature and salinity of salt solutions. Although we only demonstrate the measurement of two parameters, the proposed sensor has the capability to measure more parameters if a multilayer waveguide structure made of different functional materials is used. The proposed sensor can benefit multifunctional analysis in a broad range of biological, chemical, and environmental monitoring applications.

Highly Birefringent Microfiber Hybrid Interferometer Sensor

In this work, an optical microfiber-based hybrid interferometer is presented. A combination of two types of in-line interferometers is achieved by inserting a section of nonadiabatic tapered polarization maintaining microfiber into a Lyot filter. The hybrid interference spectrum shown as large spectrum envelope and fine fringes, corresponding to the polarized and modal interferences is obtained. We experimentally investigate the response characteristics of the two-interference system using both spectral interrogation and spatial frequency domain analysis. The refractive index sensitivities are 1150.0nm/RIU and 1779.8nm/RIU, and the temperature sensitivities are 190pm/°C and -12.7 pm/°C for two interferences, respectively. The proposed hybrid interferometer has the advantages of simple device and compact structure, and has the potential of simultaneous measurement of multiple parameters.

Simultaneous measurement of the refractive index and the pressure by mode splitting in concentric triple microring resonators with a single opening.

Concentric triple microring resonators with a single opening on the flexible SU-8 substrate are proposed and theoretically demonstrated for simultaneous detection of refractive index (RI) and pressure changes. Since an opening defect is introduced, the mode splitting occurs, which forms a symmetric and an asymmetric standing wave mode (SWM). The energy distribution of the two SWMs is quite different so that the sensitivities of the RI and pressure in the SWMs can be distinguished. The RI sensitivities of 186.37 nm/RIU and 107.69 nm/RIU and the pressure sensitivities of 1.42 pm/KPa and 1.07 pm/KPa are obtained corresponding to the symmetric and the asymmetric SWMs, respectively. By solving a second-order sensitivity inverse matrix, the change in RI and pressure can be measured simultaneously, thereby eliminating the influence of the strain-optical coupling effect in the field of biosensing application. The proposed structure has great potential in achieving simultaneous measurement of multiple parameters.

Distributed optical fiber sensing: Review and perspective

Over the past few decades, optical fibers have been widely deployed to implement various applications in high-speed long-distance telecommunication, optical imaging, ultrafast lasers, and optical sensors. Distributed optical fiber sensors characterized by spatially resolved measurements along a single continuous strand of optical fiber have undergone significant improvements in underlying technologies and application scenarios, representing the highest state of the art in optical sensing. This work is focused on a review of three types of distributed optical fiber sensors which are based on Rayleigh, Brillouin, and Raman scattering, and use various demodulation schemes, including optical time-domain reflectometry, optical frequency-domain reflectometry, and related schemes. Recent developments of various distributed optical fiber sensors to provide simultaneous measurements of multiple parameters are analyzed based on their sensing performance, revealing an inherent trade-off between performance parameters such as sensing range, spatial resolution, and sensing resolution. This review highlights the latest progress in distributed optical fiber sensors with an emphasis on energy applications such as energy infrastructure monitoring, power generation system monitoring, oil and gas pipeline monitoring, and geothermal process monitoring. This review aims to clarify challenges and limitations of distributed optical fiber sensors with the goal of providing a pathway to push the limits in distributed optical fiber sensing for practical applications.

Magnetic resonance fingerprinting of temporal lobe white matter in mesial temporal lobe epilepsy.

ObjectiveMesial temporal lobe epilepsy (MTLE) is a network disorder. We aimed to quantify the white matter alterations in the temporal lobe of MTLE patients with hippocampal sclerosis (MTLE‐HS) by using magnetic resonance fingerprinting (MRF), a novel imaging technique, which allows simultaneous measurements of multiple parameters with a single acquisition.MethodsWe consecutively recruited 27 unilateral MTLE‐HS patients and 22 healthy controls. Measurements including T1, T2, and PD values in the temporopolar white matter and temporal stem were recorded and analyzed.ResultsWe found increased T2 value in both sides, and increased T1 value in the ipsilateral temporopolar white matter of MTLE‐HS patients, as compared with healthy controls. The T1 and T2 values were higher in the ipsilateral than the contralateral side. In the temporal stem, increased T1 and T2 values in the ipsilateral side of the MTLE‐HS patients were also observed. Only increased T2 values were observed in the contralateral temporal stem. No significant differences in PD values were observed in either the temporopolar white matter or temporal stem of the MTLE‐HS patients. Correlation analysis revealed that T1 and T2 values in the ipsilateral temporopolar white matter were negatively correlated with the age at epilepsy onset.InterpretationBy using MRF, we were able to assess the alterations of T1 and T2 in the temporal lobe white matter of MTLE‐HS patients. MRF could be a promising imaging technique in identifying mild changes in MTLE patients, which might optimize the pre‐surgical evaluation and therapeutic interventions in these patients.

Development of a two-line DLAS sensor for liquid film measurement.

The simultaneous measurements of multiple parameters (film thickness, temperature, etc.) of the liquid films are crucial for the design and optimization of relevant industrial processes. Here, a sensor based on diode-laser absorption spectroscopy (DLAS) was developed to simultaneously measure liquid water film thicknesses and temperatures by combining two diode lasers at different wavenumber positions, 6718.2 cm-1 and 7040.8 cm-1. Serious beam steering effects can be avoided by adding an integrating sphere to improve the performance of the sensor for the investigations of dynamic films. The measurement accuracies of this sensor were firstly validated by a calibration tool with known film thicknesses and temperatures. It revealed that the averaged deviations between the measured film thicknesses/temperatures and the corresponding known parameters were 4.58% and 1.34%, respectively. The sensor was then employed to study liquid film evaporation processes on a horizontal quartz glass plate. The imaging method and the thermocouple were simultaneously employed to obtain the film thicknesses and temperatures to compare with the DLAS results. It showed that the average evaporation rates of the liquid films were 0.34/0.41/0.57 μm/s at different temperatures (340/360/390 K) of the heat gun outlet, respectively, and the evaporation rates increased with the increasing film temperatures. The whole evaporation process can be tracked with the sensor. Furthermore, the sensor was applied to simultaneously determine the variations of liquid film thicknesses and temperatures in a flow channel. It was found that the film temperatures remained almost constant during passage of low-amplitude surface waves at the film temperatures 308/315/323 K.

Simultaneous Measurement of Multiple Parameters of a Subwavelength Structure Based on the Weak Value Formalism.

A mathematical extension of the weak value formalism to the simultaneous measurement of multiple parameters is presented in the context of an optical focused vector beam scatterometry experiment. In this example, preselection and postselection are achieved via spatially varying polarization control, which can be tailored to optimize the sensitivity to parameter variations. Initial experiments for the two-parameter case demonstrate that this method can be used to measure physical parameters with resolutions at least 1000times smaller than the wavelength of illumination.

Lab-on-Fiber Nanoprobe with Dual High-Q Rayleigh Anomaly-Surface Plasmon Polariton Resonances for Multiparameter Sensing

Surface plasmon resonance (SPR) based sensing is an attractive approach for realizing lab-on-fiber nanoprobes. However, simultaneous measurement of multiple parameters (e.g., refractive index and temperature) with SPR-based nanoprobes, although highly desirable, is challenging. We report a lab-on-fiber nanoprobe with dual high-Q Rayleigh anomaly (RA)-surface plasmon polariton (SPP) resonances for multiparameter sensing. To achieve high-Q RA-SPP resonance the nanoprobe employs a plasmonic crystal cavity enhanced by distributed Bragg reflector (DBR) gratings on the end-face of a single-mode optical fiber. By tailoring the grating periods of the plasmonic crystal cavity and DBRs, two spatially separated high-Q RA-SPP resonance modes are designed within a 50 nm spectral range in C + L band. The fabricated nanoprobe demonstrates two RA-SPP resonances near 1550 nm with high Q-factors up to 198. These two high-Q resonances are further showed to exhibit distinctive responses to the changes of refractive index and temperature, which enables simultaneous measurements of both parameters. The proposed lab-on-fiber nanoprobes will pave the way for realizing compact multiparameter sensing solutions compatible with optical communication infrastructures.

Antiresonant Reflecting Guidance and Mach-Zender Interference in Cascaded Hollow-Core Fibers for Multi-Parameter Sensing.

We propose and demonstrate a cascaded hollow-core fiber (HCF) device for multi-parameter sensing based on the combination of antiresonant reflecting guidance (ARRG) and Mach-Zender interference (MZI). The device was fabricated by splicing two sections of HCF together. Two sets of fringes, which have different free spectral ranges, were generated from ARRG and MZI, respectively, and were aliasing in the transmission spectrum. The two sets of fringes were then separated using a band pass filter and a Gaussian fitting technique. The wavelengths at two transmission loss dips formed by ARRG and MZI exhibit a temperature sensitivity of 14.1 and 28.5 pm/°C, and a strain sensitivity of 0.4 and −0.8 pm/με, respectively. By using a crossing matrix with differences sensitivities, the cross-sensitivity between temperature and strain can be solved. The gas pressure response of the cascaded HCF device was also tested up to 300 °C, and linear relationships between the gas pressure sensitivities and temperature were found, which can be used in gas pressure application in various temperatures. Moreover, the proposed cascaded HCF sensor is compact, low cost, and simple for fabrication, and hence offers a promising way for the simultaneous measurement of multiple parameters, such as temperature, strain, and gas pressure.

Real-time multiparameter study of mitochondrial functions: Instrumental and analytical approaches

In modern biomedical science, a descriptive study is no longer the major focus of many fields. More researchers are now seeking approaches that will help them obtain maximum information from a single sample or model, which will allow them to make more detailed conclusions than previously about mechanisms that underlie certain phenomena. Clearly, simultaneous measurement of multiple parameters will provide more useful information compared to that which can be assessed through parallel studies with multiple single-parameter measurements. Mitochondria are actively involved in the regulation of a number of biochemical processes that are vitally important for normal cell functioning. Dysregulation of cell metabolism occurs under multiple pathological conditions. While changes in mitochondrial and cellular functioning are related to each other, understanding of the details of most mechanisms underlying these relationships are still unknown. It would be appropriate to have an instrument that will help to uncover sequences of events and temporal links among the parameters that involve functional mitochondrial and cellular integration. The current review is focused on the analysis of these technological limitations, and, based on the combined approach, provides hypothetical suggestion on how possibly to create such an instrument.

Simultaneous measurement of refractive index and temperature based on SPR in D-shaped MOF.

A surface plasmon resonance (SPR) sensor based on D-shaped microstructured optical fiber (MOF) is proposed to realize the simultaneous measurement of refractive index (RI) and temperature. The D-shaped flat surface coated with a gold layer is in direct contact with analyte as a sensing channel of RI, and one of the air holes near the fiber core is filled with chloroform to detect temperature. Two separate channels and birefringence caused by the asymmetric structure can distinguish the variations of RI and temperature independently, thus completely solving the cross-sensitivity problem. This is the first time to realize the simultaneous measurement of multiple parameters without matrix equations, to the best of our knowledge. Results show that the y-polarized peak supported by channel I only shifts with RI variation and is unaffected by the temperature floating. Similarly, the x-polarized peak supported by channel II is only influenced by the change of temperature in the external environment. The effect of gold layer thickness is investigated numerically, and the sensor sensitivity is identified both in wavelength and amplitude interrogations. This work is very helpful for the design and implementation of a highly sensitive, real-time, and distributed SPR sensor for multi-parameter measurement applications.

<italic>LC</italic> Passive Wireless Sensors Toward a Wireless Sensing Platform: Status, Prospects, and Challenges

Inductor–capacitor ( $LC$ ) passive wireless sensors use a transformer with loose coupling between an external readout coil and an inductor that receives power through this inductive coupling. Changes in the sensor are wirelessly and remotely detected by the readout coil, which makes them highly useful in applications that require the sensor to be powered remotely and to occupy a small volume, such as harsh and sealed environments, where physical access to the sensor is difficult. Although the sensor to accomplish this function dates from the 1960’s, its rapid extension over the past decades has benefited from microelectromechanical systems. This paper provides an overview of the status and challenges in the $LC$ passive wireless sensor toward a wireless sensing platform. The basic sensing principles are first categorized into detecting changes of the sensor in response to the capacitance, resistance, inductance, or coupling distance due to the parameter of interest through monitoring the impedance magnitude and phase spectrum. The present state of the art in sensor applications for pressure, strain, temperature, humidity, biochemical, gas, and so on is then reviewed and compared. For emerging applications from many Internet of Things scenarios, geometrical constraints, such as small and non-invasive coils, reduce the magnetic coupling between the sensor and the readout coil, resulting in a limited interrogation distance. Furthermore, an increasing number of applications also require the simultaneous measurement of multiple parameters. Recent efforts to increase the interrogation distance and to extend the measurement of single parameter to multiple parameters are finally outlined. [2016-0093]

Multiple Modes of a Photonic Crystal Cavity on a Fiber Tip for Multiple Parameter Sensing

Measuring resonant wavelengths of different modes of a luminescent semiconductor photonic crystal cavity placed on the tip of an optical fiber is proposed and demonstrated for simultaneous measurement of multiple parameters, and is applied to the measurement of temperature and refractive index in the temperature range of 77-370 K. The operation principle is supported by the finite-element method simulations. The robustness of a simple mounting scheme without adhesives is proven experimentally. The simplicity, extremely small size, and high sensitivity to both refractive index and temperature makes this concept an ideal fiber-optic sensor for a multitude of applications.

Characterization of Temperature and Strain Using a Tilted Fiber Bragg Grating

The simultaneous measurement of multiple parameters by tilted fiber Bragg grating is an emerging area of research. The tilted fiber Bragg grating is a special short-period fiber grating in which the plane of the grating is intentionally tilted with respect to the fiber axis. The angle between the grating plane and fiber axis enables the transmission spectrum of the fiber to contain both core and cladding mode information which is a unique advantage. This article describes simultaneous measurements of temperature and strain using a tilted fiber Bragg grating.

Simultaneous Measurements of Multiple Parameters at Elevated Temperature Using a Frequency-Division Multiplexing Scheme with Tunable Diode Lasers

A multiplexed diode-laser sensor system based on second harmonic detection of wavelength modulation spectroscopy (WMS) is developed for application at elevated temperatures with two near-infrared diode lasers multiplexed using a frequency-division multiplexing scheme. One laser is tuned over a H(2)O line pair near 7079.176 and 7079.855 cm(-1), and another laser is tuned over a pair of CO(2) and CO lines near 6361.250 and 6361.344 cm(-1). Temperature and concentrations of H(2)O, CO(2), and CO could be measured simultaneously by this system. In order to remove the need for calibration and correct for transmission variation due to beam steering, mechanical misalignments, soot, and windows fouling, the WMS-1f normalized 2f method is used. Demonstration experiments are conducted in a heated static cell. The precision of temperature and the concentrations for H(2)O, CO(2), and CO are found to be 1.57%, 3.87%, 3.01%, and 3.58%, respectively. These results illustrate the potential of this sensor for applications at high temperatures.

Multivariate sensing and wireless data communication for process monitoring in RF-shielded environment

Online process metrology is critical to ensuring manufacturing quality and productivity. This paper presents the design and modelling of a multivariate sensor that enables the simultaneous measurement of multiple parameters from within an RF shielded environment, e.g. an injection mold. A coded wave modulation scheme is developed for wirelessly transmitting the parameters through the mold. The design of the modulator is optimized through a coupled field analysis for noise reduction. The effectiveness of the sensing method is demonstrated in the online measurement of melt pressure, temperature, viscosity, and velocity. This sensing method is applicable to various process monitoring scenarios.