Improving dynamic response of a temperature-only FBG sensor

Inrecentyears,fiberBragggrating(FBG)sensinghasattractedextremelyhighattentioninbothscientific researchcommunityandindustry.FBGsensingprovides uniqueadvantagesoverconventionalelectricalsensorsandcanbeusedinapplicationswhereelectricalsensors arelimited[14].…     

Influence of stress birefringence on the performance of a FBG pressure sensor

No matter designing and manufacturing a FBG pres-sure sensor ,or monitoringthe strain on material surfaceby using FBGas a pressure sensor ,the difficult technicalproblems to be solved are as follows :first ,howto effec-tively couple and propagatethe external stresstothe ax-ial direction of FBGthrough the underlay material ;sec-ond,howto make the FBGpressure sensor achieving aneffect of enhancing sensitivity;third,how to ensure alinear relationship between FBG′s reflection wavelengthand t…     

Influence of coupling agent＇s self-assembly upon performance of polymer coated FBG pressure sensors

Based on super-molecule self-assembly and entropy-driven self-assembly mechanisms,the coupling agent was evolved into colloid spheres with average diameter of 2-2.3 μm on the fiber Bragg grating （FBG） with silicon substrate, and the coupling mechanism among polymer, coupling agent and FBG was analyzed. The polymer coated FBG pressure sensors was capsulated by uniform coupling mode and self-assembly coupling mode of the coupling agent respectively, and their performance parameters were tested. It was shown, adopting the self-assembly coating of coupling agent and with the same other capsulated technologies,that the measuring range of the sensor expanded from 0.6 MPa to 1.6 MPa,the repeated times for coupling failure increased from 54 to 125 times and the pressure sensitivity coefficient enhanced from 1.09 to 2.98. By controlling the diameter of the spheres and the line density,the measuring range and the sensitivity of the FBG pressure sensors can be obviously improved.     

Adaptive optical design in surface plasma resonance sensor

A double-prism adaptive optical design in surface plasma resonance （SPR） sensor is proposed,which consists of two identical isosceles right-triangular prisms. One prism is used as a component of Kretschmann configuration, and the other is for regulation of the optical path. When double-prism structure is angle-scanned by an immovable incident ray, the output ray will be always parallel with the incident ray and just has a small displacement with the shift of output point. The output ray can be focused on a fixed photodetector by a convex lens. Thus it can be avoided that a prism and a photodetector rotate by 8 and 28 respectively in conventional angular scanning SPR sensor. This new design reduces the number of the movable components, makes the structure simple and compact, and makes the manipulation convenient.     

Novel simulation method for fiber Bragg grating under inhomogeneous strain fields

The spectra of fiber Bragg grating （FBG） in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method can be employed for exact simulation of the spectrum of Bragg grating in such field, but the convergence speed is slow. On the other hand, although the transfer matrix method could be used with higher convergence speed, the precision is poor because of the neglect of the grads of strain change. By improving the FBG equivalent period, a novel simulation method based on a modified transfer matrix method is proposed, which has the advantage of quick-convergence as well as good accuracy.     

Double-theodolite measurement system used in the image calibration of space photographic instrument

Space photographic instrument has been widely usedin aerial andastronavigationsurvey.Image calibrationisa veryi mportantjobfor theinstrument beforeit was ap-plied to measurement .When the i mage surface can becalibrated correctly, the instrument will operate at agood status and obtain high qualityi mage.The purposeof characterizing the i mage of instrument is to gain theinterdependence of both coordinate systems in i magesurface and instrument . The two coordinate systemswill keepinthe same di…     

Novel video coding algorithm based on 3D-binDCT

In this paper we propose a three dimensional multiplierless discrete cosine transform（DOT） with lifting scheme called 3D-binDCT. Based on 3D-binDCT, a novel video coding algorithm without motion estimation/compensation is proposed. It uses the 3D-binDCT to exploit spatial or temporal redundancy. The computation of binDOT only needs shift and addition operations, thus the computational complexity is minimized. DO coefficient prediction, modified scan mode and arithmetic coding techniques are also adopted. Extensive simulation results show that the proposed coding scheme provides higher coding efficiency and improves visual aualitv, and it is easy to be realized by software and hardware.     

Classifying Algorithm Based on a Fuzzy Neural network for the control of a Network Attached Optical Jukebox

In our previous work[1-3],we established a new ap-proach which has mass disk buffer in optical jukeboxand can be accessed directly from network in a massstorage system,and namedthis systemas network atta-ched optical jukebox (NAOJ) .In order to i mprove i…     

Box-like spectral response of a series-coupled microring resonant filter in a parallel channel

Inthelast decades ,microring resonator( MRR) wave-lengthfilters are developed rapidly because of their po-tential applications in wavelength division multiplexing( WDM) communicationsystems andtheir excellent fea-tures includingfunctionality,compactness a…     

Gradient descent approach for minimizing dissimilarity measure in log-polarimagery

The information received by the visual cortex is theresult of a log-polar conformal mapping of the retinalsti mulus[1].Indeed,the log-polar transformation hasbeen adoptedin numerous applications andisthe subjectof current research interest[2].Log-polar i …     

Principles and realizations of FBG wavelength tuning with elastic beams

FiberBragggrating(FBG)isasignificanttechnology thatisusedtodesignkeydevicesorcomponentsinthesystemsoffibercommunicationandfibersensing[1], suchastunablefiberlasers[2],WDW/DM[3],WADM[4],tunablefiberfilter[5],fiberdispersioncom pensation[6],gainflattingofEDFA[7],FBG typeinter ferometer[8]andfibergratingsensors[9,10].OneofthekeyresearchissuesonFBGdevicesistomakethetun ingwavelengthdeviceswhichhavegoodcharacteristics ofwidetunablewavelengthrange,stableoutput,goodmultiplexingcapability. …     

Coherent confocal microscope with a phase-only filter in its extended source

Inpractice,afinitesourceisnecessaryanditssize playsanimportantroleintheimagingofconfocalscan ningopticalmicroscope.Therefore,thedependenceofits3DOTFonthesourcesizehasbeeninvestigatedfora coherent[1]confocalscanningopticalmicroscope.The resultshowsthatther…     

Coupling constant of triple-clad long-period fiber grating

Because of its high sensitivity to external refractiveindex,the long-period fiber grating(LPFG) has beenused as chemical sensor1-3.Now the multi-clad LPFGwiththe fil ms coated on cladding area of the fiber grat-ing has drawn much attention[4].It cani mpro…     

New real-time image processing system for IRFPA

Infraredfocal plane array(IRFPA) is a kind of infra-red detector array whichis sensitive toinfraredradiationandintegrated with signal processing circuits .The IRF-PAi maging systemhas advantages of si mple configura-tion,high reliability,high sensitivity …     

Optical-fiber distributed temperature sensor: design and realization

Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering, a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared, and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1℃ and 2 m, respectively, and that the system response time is about 180 s with a sensing range of 5 km and with a temperature measurement range of 0-100℃.     

Research on fuzzy neural network algorithms for nonlinear network traffic predicting

Neural networks provide massive parallelism,robust-ness ,and approxi mate reasoning,which are i mportantfor dealing with uncertain,inexact ,and ambiguous data,withill-defined problems and sparse data sets[1].It hasbeen proved that a neural network system …     

Rapid calibration for line structured light vision sensors

Withthe development of electronics ,i mage processingand computer techniques ,structured light 3D vision in-spection has gained wide acceptance.It is due tofast ac-quisition,very si mple optical arrangement ,low cost ,large field of viewandits robust natu…     

Wavelet method for processing white light interferogram from optical fiber interferometer

The precise determination of the ZOPDfor the whitelight interferometryis essential toits applicationsinthefield of measurements of surface profile,height ,anddepth,and quality control[1-5].The ZOPDis a positionininterferogram with the highest envelope pea…     

Geometry constraints and matching algorithm for lunar rover stereo vision

China has started the lunar exploration project inclu-ding alunar satelliteto belaunchedin2007 .Inthe nextstep alunar rover will be requiredto move onthe lunarsurfacein alarge range for scientific goals . Vision sys-temis a crucial part of alunar rover sinceit isin chargeof building quantitative models of terrain geometry andmaking the spatial layout of the environment explicit .Many direct terrain-mapping techniques ,such as laserranging,have been developed for mobile robots on theearth andso…     

Novel measurement scheme of peak separation of side-hole fiber grating

Theside holefiberisanewkindofpolarizationmain tainingfiberwithastrangestructure[1].Becauseofthe existenceoftheintrinsicbirefringence[2],therearetwo peaksofdifferentpolarizationsinthereflectionspectrumoftheside holefibergrating,whichisproducedbywrit inggra…