A Sensing Peak Identification Method for Fiber Extrinsic Fabry⁻Perot Interferometric Refractive Index Sensing.

A study of the correlation between the refractive index (RI) method adopted by the European Community (EC) and a reference pycnometric method for the measurement of alcoholic strength was undertaken. A new RI method with greater accuracy was also developed. Alcoholic strength measured by both RI methods presented a relatively constant negative bias compared with results by the pycnometric method. Differences found between the RI methods and the pycnometric method were 0.6-0.9% (v/v) when RI was measured by the EC method and 0.4-0.5% (v/v) when the new RI method developed in our laboratory was used. Statistical analysis of the results showed that differences between the 2 RI methods and the reference pycnometric method were statistically significant at the 95% confidence level. Correction factors are proposed for the accurate use of measurements of alcoholic strength obtained for small volume samples.

A reflective fiber-optic refractive index sensor based on multimode interference in a coreless silica fiber

In this article, we have proposed and experimentally demonstrated an optical fiber refractive index (RI) sensing interrogation system realized by extrinsic Fabry–Perot interferometer (EFPI) structure-based microwave photonic filter (MPF) technology. EFPI is considered as a sensing element, as well as a spectrum slicer of the MPF. The shift of the central frequency of the MPF’s passband caused by the change of the RI in the Fabry–Perot (FP) cavity can be monitored to demodulate the RI variation. In our experiment, four EFPI sensors with different FP cavity lengths have been applied for the RI sensing test. The experimental results show that the sensitivity can be tailored by adjusting the length of the FP cavity, and the longer the length of the FP cavity, the higher the sensitivity can be achieved. When the length of the FP cavity is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$960 ~\mu \text{m}$ </tex-math></inline-formula> , a high sensitivity of 1.2 GHz/RIU has been obtained. The proposed sensing system can transfer the changes of the interference pattern in the optical domain to the central frequency shift of the MPF’s passband in the electronic domain and thus avoid the limitation of measurement range induced by the periodic characteristics of the FP interference spectrum. The proposed sensing system also has the advantages of high sensitivity, the feasibility of multiplexing, temperature insensitivity, good repeatability and stability, simple fabrication, low cost, and so on.

To perform a high temperature strain measurements, the sapphire extrinsic Fabry-Perot interferometer (EFPI) sensor head was attached to a silicon carbide rod and placed in a RF induction heater mounted on an MTS load frame. The high-temperature ceramic adhesive is designed to withstand temperatures up to 4000° F. As a basis for comparison, a gold-coated silica EFPI sensor was attached along side the sapphire EFPI. Initially, strain data was recorded at room temperature as the silicon carbide rod was slowly loaded to 4500 lbs. When the temperature was stabilized at a maximum of 2000° F, the SiC rod was again loaded to determine the effects of temperature on strain. Although the sapphire sensor was capable of measuring strain at higher temperatures, die induction heater, being poorly insulated, was not able to further heat the test material. The purpose of the second experiment was to determine the survivability and repeatability of tiie sapphire EFPI due to high-cycle fatigue loading. The long-term survivability of the sensor, in both static and fatigue loading, has been demonstrated. Although the load frame was shutoff after 200,000 cycles, one would expect to be able to fatigue load tiie sensor for millions of cycles since the components of the EFPI sensing head are free to move inside the alignment tube. This is consistent widi data obtained for similar silica opdcal EFPI sensors diat were fadgue loaded to over 10 million cycles as compared to resistive strain gages that typically can be cycled only to 60,000 at 2000°F.

Optical fiber Bragg grating (FBG) sensors have significant potential for use as embedded devices to monitor the structural integrity of engineering materials. The main drawback of the FBG strain sensor is its cross-sensitivity to temperature. This paper reports a simple scheme for multiplexing a FBG and an extrinsic Fabry-Perot interferometric (EFPI) sensor to enable the decoupling of strain from temperature. The EFPI sensor was constructed using a precision bore quartz capillary tube which housed two cleaved optical fibers. The gap between the fiber end- faces served as the Fabry-Perot cavity. Since the coefficients of thermal expansion between the optical fiber and the capillary tube were similar, the EFPI sensor has a very low sensitivity towards temperature. Therefore, when both sensors are placed close together, the EFPI sensor can act as the strain sensor, and temperature can be determined from the FBG wavelength shift after taking out the strain effect. The signal processing for the EFPI sensor was based on a channelled spectrum method using a CCD spectrometer. The same CCD spectrometer was also used to determine the wavelength shift of the FBG. The cross-talk between the EFPI and FBG sensors was evaluated. The feasibility of conducting simultaneous strain and temperature measurements was demonstrated.

We report and demonstrate a single-mode asymmetric tapered fiber as a refractive index (RI) sensor based on evanescent field sensing. The proposed setup managed to sense the changes of RI when the tapered region was exposed to different concentrations of Sodium chloride (NaCl). This was possible due to the output interference spectrum shifting in response to the changes of RI. Different environmental sensitivities were achieved by manipulating the transition lengths of the tapered fiber. Experimental results depict RI sensitivities of 3914.7 nm/RIU (refractive index unit) and 3395.7 nm/RIU for taper profiles with down-taper transition lengths of 2 mm and 8 mm, respectively, which is higher than previously reported asymmetric taper RI sensors. Such findings may find itself beneficial in low cost, reliable and simplified sensors.

In this work, we present an ultra-high sensitivity (S) refractive index (RI) sensor for biological applications. Silicon on insulator (SOI) ring resonator (RR) based RI sensors have been extensively investigated. Light propagation is studied in the small SOI RRs based on sub-wavelength grating (SWG) waveguides with aqueous claddings. For the device analysis, the two-dimensional conformal transformation method is jointly used with the effective index method. Furthermore, FEM simulations of this structure have been also performed in both the air and water claddings. These good-matched results are further compared with experimental and FDTD results in other valid references. Having found a high data matching between our results and experimental results, we repeat our calculation for different side-widths (d=150-225 nm) and ring radii (7-10 µm). For each ring radius, the best amount of side-width is found. Then bulk refractive index sensing experiments are simulated using changing cladding RI in the range of nc=1.332-1.350 RIU. These RI changes correspond to concertation changes of glucose-water solutions in the cladding. Finally, we obtain the highest sensitivity of 24946 nm/RIU in the case of a radius 7 µm, 500 nm width, 220 nm height, 150 nm side-width, and T of 50 nm between the grating arrays on the RR. It is worth noting that this proposed structure shows 150 times sensitivity enhancement compared to a standard SOI RR-based biosensor with the same radius, w, and h. In addition, the RI sensor suggested in this work shows ultra-high sensitivity in a dynamic range of 1.332-1.352 RIU. This range of RI variation covers almost all the RI variations of the blood components. These results show excellent potential for employing the proposed SOI RR based on SWG waveguides in a liquid-biopsy analysis of patients with cancer. These might pave the way toward the early detection of cancers.

Surface plasmon resonance refractive index sensor based on photonic crystal fiber covering nano-ring gold film

A liquid level optical fiber sensor with refractive index compensation through cascading double multi-mode interferences

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTHigh-Q Optical Sensors for Chemical and Biological AnalysisMatthew S. Luchansky and Ryan C. Bailey*View Author Information Department of Chemistry, University of Illinois at Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States*E-mail: [email protected]. Address: 44 Roger Adams Lab 600 South Mathews Avenue, Urbana, IL, 61801. Phone: (217) 333-0676.Cite this: Anal. Chem. 2012, 84, 2, 793–821Publication Date (Web):November 23, 2011Publication History Published online23 November 2011Published inissue 17 January 2012https://pubs.acs.org/doi/10.1021/ac2029024https://doi.org/10.1021/ac2029024review-articleACS PublicationsCopyright © 2011 American Chemical SocietyRequest reuse permissionsArticle Views6236Altmetric-Citations223LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Assays,Crystals,Nanoparticles,Quantum mechanics,Sensors Get e-Alerts

Due to the limitations of measurement equipment and the influence of factors such as the environment and target, measurement errors may occur during the data acquisition process of airborne LiDAR bathymetry (ALB). The refractive index of water is defined as the propagation ratio of the speed of light waves in a vacuum to that in water; this ratio influences not only the propagation speed of the laser pulse in water but also the propagation direction of the laser pulse entering water. Therefore, the influence of refractive index changes in water on the ALB errors needs to be analyzed. To this end, the principle of ALB is first briefly introduced. Then, the calculation method for the refractive index of water is described with Snell’s law and an empirical formula. Finally, the influence of refractive index changes on ALB errors is analyzed using the derived formula at the water–air interface and in the water column. The experimental results showed that in a constant elevation of 50 m for a bathymetric floor, the refractive index changes in water caused by temperature, salinity, and depth are less than 0.001. The maximum bathymetric error and maximum planimetric error caused by the refractive index changes at the water–air interface are 0.036 m and 0.015 m, respectively. The ALB errors caused by refractive index changes in the water column are relatively low, and the water column does not need to be layered to calculate the ALB errors. The influence of refractive index changes in water on the ALB error is minimal, accounting for only a small proportion of all bathymetric errors. Thus, it is necessary to determine whether the effect of the ALB error due to refractive index changes in water needs to be corrected based on the accuracy requirements of the data acquisition. This study and analysis can provide a reference basis for correcting ALB errors.

An ultra high-sensitivity temperature and refractive index (RI) sensor based on surface plasmon resonance (SPR) effect in D-shape high birefringence photonic crystal fiber (PCF) is presented and discussed by the finite element method (FEM). The designed PCF is polished to enhance the interaction of the evanescent field with the external medium, ultimately improving the sensing performance. The influence of three different plasma materials, gold, silver and aluminum, on the sensing performance was investigated. Finally, the chemically stable plasma material gold is selected to coat on flat surface of D-shape PCF for SPR sensing, realizing the sensitive real-time monitoring of RI and temperature. The sensing performance was greatly improved, with a wide RI (1.43 to 1.50) and temperature (36 °C to 86 °C) detection range, and the corresponding maximum sensitivity was 44850 nm/RIU and -16.875 nm/°C, respectively. Furthermore, the sensitivity is not particularly sensitive to the sizes of the designed air holes, which leads to a sensor with high structure tolerance. Numerical results show that the coating thickness not only affects the sensitivity but also the detection range of the sensor, so we can tune the RI and temperature detection range by adjusting the gold film thickness to meet specific detection requirements. The sensor with enhanced sensitivity, tunable detection range, and high fabrication tolerance has a wide application prospect in the field of life science research, chemical production, and environmental monitoring.

A compact and ultra high sensitive RI sensor using modal interference in an integrated optic waveguide with metal under-cladding

A sensitivity-enhanced optical fiber refractive index sensor based on inline Mach-Zehnder interferometer is proposed. The sensor head is formed by splicing a tapered thin-core diameter fiber between two sections of single mode fibers. The taper (less than 1 mm) plays an important role in improving the sensitivity of the sensor. The sensitivity of refractive index is measured to be 0.447 nm for a 1% change of refractive index in the typical refractive index range of 1.333- 1.3725. The whole fabrication process (including splicing and tapering) can be operated by a commercial fiber splicing machine. The proposed sensor also shows the merits of simple structure, low cost, and easy fabrication.

In this paper we investigate the performance of a SCS-6/Ti-15-3 composite system, a carbon/SiC woven composite system, and an AS4/3501-6 composite system, subjected to long term mechanical fatigue, with an extrinsic Fabry-Perot interferometric (EFPI) fiber optic strain sensor. Both stiffness reduction and the degradation of thermal expansion coefficient (TEC) are monitored. The obtained results show that the EFPI sensor provides reliable data during long term fatigue loading up to 1 million cycles. The results suggest that the EFPI sensor is a viable means to monitor current and proposed characteristic damage metrics for various composite systems. We also monitor the TEC degradation during the thermal fatigue of celion G30-500/PMR-15 woven cross-ply composite system, and present a simple micromechanical model, that employs a shear lag approach, utilized to predict the effect of matrix cracking on the TEC of the composite. Results show that good agreement between experimental data and theoretical results is obtained, and that this parameter changed by as much as 80% over the fatigue life of the composite.