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1.
Fiber Bragg grating interrogator using edge filtering technique with microbend loss error mitigation
Navneet Singh Aulakh 《Optik》2011,122(9):796-798
This paper presents an edge filtering technique based interrogator for fiber Bragg grating sensors with microbend attenuation compensation system. The interrogator uses reference fiber along with the fiber in which the grating is inscribed to mitigate the effect of microbend attenuation in determining the Bragg wavelength of the sensor. 相似文献
2.
A distributed optical fiber sensor (DOFS) with the principle of microbend loss has been developed for concrete or rock-sliding damage measurement. The combination of multiple microbend sensors can form a sensor array for distributed sensing application in monitoring local slippage or deformation along the rock mass of the high slope, and the optical time-domain reflectometry (OTDR) can be conveniently used for interrogation of each sensor point. The sensor sensitivity can be obtained at a specific range according to the requirement of the model test condition. Connected with multiplexed sensing processing schemes, its sliding range of dynamic sensing response reached 0–3.6 mm and semi-empirical formula was fitted according to data from model tests. The DOFS array may find a potential application in real-time monitoring and damage detection of large and critical slope engineering structures. 相似文献
3.
Whispering gallery mode (WGM) based micro-optical sensors are known to have higher sensitivity than fiber Bragg grating, Fabry–Perot,
and microbend sensors. WGM sensors are created by optical coupling of a dielectric microparticle with an optical fiber. The
combination of a microparticle and an optical-fiber to create the sensor requires encapsulating them in a suitable material
so that the sensor can be used in practical applications. The sensitivity of the encapsulated sensors needs to be calibrated
before they can be used. The present study conducts a parametric study to understand the effect of variables such as particle
size and particle–fiber distance on the sensitivity of the encapsulated WGM sensors. Solid and hollow microparticle based
sensors are studied. In the case of hollow particles, their wall thickness effects are also characterized. Results show that
despite small strain, change in the index of refraction of the particle material due to the applied force contributes significantly
in determining the sensitivity of these sensors. 相似文献
4.
《Optik》2014,125(1):301-303
In this paper we report a simple microbend fiber optic sensor using a plastic fiber, LED and photodetector assembly for sensing minute variation of refractive index of chlorinated water. Chlorinated water has slightly higher refractive index and gradual release of chlorine from bleaching powder treated water causes a temporal decrease in refractive index of the solution. The evaporation of chlorine from water and the change in refractive index is found to follow a first order exponential decay function of time. Introducing microbends in an optical fiber is easier and less complex than etching of fiber cladding for traditional optical fiber sensors. 相似文献
5.
6.
Fiber-optic microbend sensor structure 总被引:2,自引:0,他引:2
We proposed and experimentally investigated a novel microbend sensor structure. The structure is composed of single-mode leads and multimode sensing fiber. The proposed structure exhibited a level of sensitivity as much as six times higher than that of the classical microbend sensor configuration when the same sensing fiber was used. Additionally, single-mode leads reduce lead noise and allow the use of more-coherent sources. The total loss of the proposed nondeformed structure is near 2 dB when the proper splicing method is used. 相似文献
7.
A Michelson-based fiber-optic low-coherence interferometric quasi-distributed sensing system permitting absolute length measurement in a sensor array is proposed. The main part of the sensing system is a fiberoptic 3 x 3 star coupler. The architecture of fiber-optic sensors can be easily realized as a linear sensor array, twin sensor arrays, or a loop sensor array. The proposed sensing scheme will be useful for the measurement of strain distribution. An important application could be deformation sensing in smart structures. A six-sensor array is demonstrated experimentally. 相似文献
8.
Simplified relations for the changes in SAW velocity and attenuation due to thin polymer coatings and vapor sorption are presented by making analytic approximations to the complex theoretical model developed earlier by Martin et al. [Anal. Chem. 66 (14) (1994) 2201–2219]. The approximate velocity relation is accurate within 4% for the film thicknesses up to 20% of the acoustic wavelength in the polymer film, and is useful for analyzing the mass loading, swelling and viscoelastic effects in SAW vapor sensors. The approximate attenuation relation is accurate within 20% for very thin films, (less than 2% of the acoustic wavelength in the film). Based on these relations, a new procedure for determination of polymer viscoelastic properties is described that exploits the frequency dependence of the velocity and attenuation perturbations, and employs multifrequency measurement on the same SAW platform. Expressions for individual contributions from the mass loading, film swelling and viscoelastic effects in SAW vapor sensors are derived, and their implications for the sensor design and operation are discussed. Also, a new SAW comb filter design is proposed that offers possibility for multimode SAW oscillator operation over a decade of frequency variation, and illustrates feasibility for experimental realization of wide bandwidth multifrequency SAW platforms. 相似文献
9.
Based on the microbend effect of optical fiber, a distributed sensor for real-time continuous monitoring of intrusion in application to buried pipelines is proposed. The sensing element is a long cable with a special structure made up of an elastic polymer wire, an optical fiber, and a metal wire. The damage point is located with an embedded optical time domain reflectometry (OTDR) instrument. The intrusion types can be indicated by the amplitude of output voltage. Experimental results show that the detection system can alarm adequately under abnormal load and can locate the intrusion point within 22.4 m for distance of 3.023 km. 相似文献
10.
11.
Wook Jae Yoo Kyoung Won Jang Jeong Ki Seo Ji Yeon Heo Jin Soo Moon Jae Hoon Jun Jang-Yeon Park Bongsoo Lee 《Optical Review》2011,18(1):132-138
In this study, two types of nasal-cavity-attached fiber-optic respiration sensors have been fabricated for noninvasive respiratory
monitoring. One is a silver halide optical-fiber-based respiration sensor that can measure the variations of infrared radiation
generated by the respiratory airflow from a nasal cavity. The other is a thermochromic-pigment-based fiber-optic respiration
sensor that can measure the intensity of reflected light which changes owing to color variations of the temperature-sensing
film according to the temperature difference between inspiratory and expiratory air. We have demonstrated the similarities
of the respiratory signals using the fiber-optic respiration sensors and the temperature transducer of the BIOPAC? system.
In addition, we verified that respiratory signals without the deterioration of the MR image can be obtained using the fiber-optic
respiration sensors. It is anticipated that the proposed noninvasive fiberoptic respiration sensors will be highly effective
for respiratory monitoring of a patient during MRI procedures. 相似文献
12.
In view of laser-assisted medical applications, the construction of silica-based sol-gel fiberoptic sensors based on photolon (Ph) and protoporphyrin IX (PP IX) is discussed. Electron microscopy and AFM were used to characterize the silica sol-gel coatings. AFM measurements indicate a change in the surface porosity. The PP IX-based sensors were constructed as a one-layer optode as well as a multilayered structure. An additional hybrid sensor made up of alternate layers of PP IX-and Ph-doped sol-gel was also constructed and examined. Sol-gel matrices were prepared from silicate precursor tetraethylorthosilicate (TEOS) mixed with ethanol in acid-catalyzed hydrolysis. The carrier matrices of photosensitive dyes were produced with factor R = 20, where R denotes the ratio of solvent moles (ethanol) to the number of TEOS moles. A multilayered coating was built up using the reverse-dipping technique. The overall coating thickness was determined by electron microscopy. Doped sol-gels with different PP IX concentrations were used to produce fiberoptic coatings. The film optodes with a different number of layers were examined by fluorescence spectroscopy. It was found that photolon and protoporphyrin IX entrapped in sol-gel preserve their chemical reactivity and have contact with the external environment. The hybrid sensor demonstrated clear fluorescence and a reversible behavior in gaseous environments. 相似文献
13.
Previous researchers have simulated strain transfer and spectrum of normal fiber Bragg grating (FBG) sensors with a polymer coating bonded on the structure. They only considered the shear stress in a polymer coating for the simulation. However, for metal-coated FBG sensors, not only shear stress but also axial stress in the metal coating should be reflected into the calculation because its axial stiffness is no longer negligible. Thus, the author investigated the strain transfer and reflected spectra of metal-coated FBG sensors by considering both shear stress and axial stress. The strain transfer analysis involved evaluating the strain profiles along the sensor by plotting an analytical solution, and validating the evaluated profiles with the results obtained by a finite element analysis (FEA). The solution was also verified by the experiments that used aluminum-coated FBG sensors bonded on a carbon fiber reinforced polymer (CFRP) composite specimen. A transfer-matrix (T-matrix) formulation and coupled mode theory were used to simulate the reflected spectra of metal-coated FBG sensors for the evaluated strain profile. In addition, the effect of mechanical and geometric parameters of the sensor was examined. The findings revealed that the strain transfer characteristics and reflected spectra deteriorated with increases in the thickness and Young's modulus of the metal coating due to the consideration of axial stress. It is the opposite results for the normal FBG sensor with a polymer coating. Furthermore, the results also indicated that the decrease in bonding thickness resulted in improved strain transfer and signal characteristics. Moreover, a bonding length of 14 mm was suitable in suppressing an asymmetric shape of the reflected spectrum and in achieving an accurate measurement. The results of the parametric study are expected to contribute to improve the measurement accuracy of metal-coated FBG sensors in actual applications. The analytical methodology can be usefully employed in the design of a metal-coated FBG sensor system. 相似文献
14.
Periodic microbending has been studied to develop an insight into the loss behavior of single-mode microbend sensors by using the finite-difference beam propagation method. Loss sensitivity variations with wavelength are examined, as well as the optical loss dependence on the number of microbends and the modal field perturbations caused by the microbending. 相似文献
15.
K. Arshak E. Moore C. Cunniffe M. Nicholson A. Arshak 《Superlattices and Microstructures》2007,42(1-6):479
During the last 10 years, a large interest has developed in the preparation of nanocomposite structures by embedding inorganic nanoparticles into polymeric materials. These materials combine the properties of the inorganic fillers with the processability and flexibility of polymers. The versatility of polymer nanocomposite systems is of special interest to the gas sensor industry where arrays of polymer/carbon black composites have been used to identify gases and odours. These polymer gas sensors provide selectivity based on their chemical structures and operate at room temperature, which provide advantages over thick-film metal oxide gas sensors. ZnFe2O4 and ZnO have excellent stability, high sensitivity, low fabrication complexity and moderate operating temperatures, which are ideal properties for a gas sensing material. In this work, the development of a thick-film ZnFe2O4/ZnO sensor, which operates at room temperature and a drop-coated conducting polymer composite sensor containing 30 w/w% ZnFe2O4/ZnO nanoparticles is discussed. The sensors were tested in a fully automated test rig and showed promising results for the detection of alcohol vapours. 相似文献
16.
Jun-Kyu Seo 《Optics Communications》2010,283(7):1307-1310
Optical temperature sensors consisting of low-loss polymer waveguides with a glass lower cladding are demonstrated. The refractive index of the optical polymer is precisely controlled to have a certain initial refractive index contrast with the glass substrate used for lower cladding. Depending on the initial index contrast, the operating temperature ranges of the sensors are determined. The polymer devices are fabricated by spin-coating and UV curing, which could be replaced by the cost-effective imprinting or injection molding process. The sensor exhibits a monotonic decrease of the transmission intensity corresponding to the temperature increase, which enables straightforward reading of temperature from the measured optical power. 相似文献
17.
Marta?Klanj?ek?Gunde Nina?Hauptman Marijan?Ma?ek Matja??Kunaver 《Applied Physics A: Materials Science & Processing》2009,95(3):673-680
SU8, the near-UV photosensitive epoxy-based polymer was used as a sensor layer in the capacitive chemical sensor, ready for
integration with a generic double-metal CMOS technology. It was observed that the response of the sensor slowly increases
with the temperature applied in hard-baking process as long as it remains below 300°C. At this temperature the response of
the sensor abruptly increases and becomes almost threefold. It was shown that fully crosslinked structure of the sensor layer
becomes opened and disordered when the sensor is hard-baked at temperatures between 300°C and 320°C, that is, still well below
the degradation temperature of the polymer. These changes in chemical structure were analyzed by Fourier-transform infrared
spectroscopy. The temperature-dependent changes of the sensor layer structure enable one to prepare a combination of capacitive
chemical sensors with good discrimination between some volatile organic compounds. 相似文献
18.
V.P. Garitchev M.A. Golub S.V. Karpeev S.G. Krivoshlykov N.I. Petrov I.N. Sissakian V.A. Soifer W. Haubenreisser J.-U. Jahn R. Willsch 《Optics Communications》1985,55(6):403-405
The results are described of an experimental investigation of mode coupling in a multimode graded-index fiber as a function of the periodic microbend amplitude. Computer-generated holograms were used as mode selecting spatial filters for measurements of the modal power distribution. The experimental data are in a good qualitative agreement with theoretical predictions. The results obtained may be helpful in the development of amplitude-type graded-index fiber sensors with high sensitivity. 相似文献
19.
Sodium chloride methanol solution spin-coating process for bulk-heterojunction polymer solar cells
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The sodium chloride methanol solution process is conducted on the conventional poly(3-hexylthiophene)(P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester(PC_(61)BM) polymer bulk heterojunction solar cells. The device exhibits a power conversion efficiency of up to 3.36%, 18% higher than that of the device without the solution process. The measurements of the active layer by x-ray photoelectron spectroscopy(XPS), atomic force microscopy(AFM), and ultraviolet photoelectron spectroscopy(UPS) indicate a slight phase separation in the vertical direction and a sodium chloride distributed island-like interface between the active layer and the cathode. The capacitance–voltage(C–V) and impedance spectroscopy measurements prove that the sodium chloride methanol process can reduce the electron injection barrier and improve the interfacial contact of polymer solar cells. Therefore, this one-step solution process not only optimizes the phase separation in the active layers but also forms a cathode buffer layer, which can enhance the generation, transport, and collection of photogenerated charge carriers in the device simultaneously. This work indicates that the inexpensive and non-toxic sodium chloride methanol solution process is an efficient one-step method for the low cost manufacturing of polymer solar cells. 相似文献
20.
Magnetic natural films composed of alginate and maghemite nanoparticles are studied. A surface treatment by citrate ions of the magnetic nanoparticles is first required to limit interactions with carboxylate functions of alginate and to stabilize them in neutral pH. Sodium alginate films, with or without nanoparticles, are immersed in a calcium chloride bath to convert them into mixed sodium/calcium alginate films. The ion exchange process is quantified by the degree of substitution (DS) deduced from sodium and calcium content obtained by atomic absorption spectroscopy. The magnetic nanoparticles content is also analysed to correlate the release of the particles to the amount of calcium present in the film. Nanoparticles do not significantly change the ion exchange process. Water insoluble films, which do not release magnetic nanoparticles, are obtained for a complete conversion of sodium alginate into calcium alginate (DS value is thus close to the stoechiometric ratio equal to 0.5). Such increase in water resistance of alginate films is caused by the formation of a dense network by crosslinking of the alginate polymer with Ca ions which prevents the alginate from going out of the film. Swelling properties of the mixed films are then investigated as a function of calcium concentration and nanoparticles content. It is found that the swelling ability in water of the films decreases by increasing the immersion time in CaCl2 bath, the swelling ratio is thus a measure of the extent of crosslinking 相似文献