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Analysis of the swelling silicone coating on the optical sensor head has been calculated based on the time and length-different due to exposure. In initial state, cladding refractive index (n2) is higher than core refractive index (n1). This situation cause the light that propagate in fiber optic leak to atmosphere. In the exposed state, cladding refractive index will decrease and results in light propagating based on total internal reflection. This situation has been described and calculated from the beginning until the maximum value.
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Secondary Theoretical Analysis of Swelling Secondary Theoretical Analysis of Swelling Characteristic of Silicone Coating for Plastic Characteristic of Silicone Coating for Plastic
Optical Fiber Optical Fiber SensorSensor( SPECTECH Research Group ( SPECTECH Research Group -- Internal SeminarInternal Seminar
11 November 2011, FKAB Meeting Room)11 November 2011, FKAB Meeting Room)
Harry Harry RamzaRamza, , Mohd Hazwan Harun, Mohd Hazwan Harun, KhairulKhairul AnuarAnuar IshakIshak, , Mohammad Syuhaimi AbMohammad Syuhaimi Ab--RahmanRahman
Spectrum Technology Research GroupSpectrum Technology Research GroupDepartment Electrical, Electronic and System EngineeringDepartment Electrical, Electronic and System Engineering
UniversitiUniversiti KebangsaanKebangsaan MalaysiaMalaysiaBangiBangi, Selangor , Selangor DarulDarul EhsanEhsan
MALAYSIAMALAYSIA
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ContentContent1.1. Basic FOSBasic FOS..
2.2. Typical Fiber Optical Sensor MechanismTypical Fiber Optical Sensor Mechanism
3.3. Configuration of Fiber Optical SensorConfiguration of Fiber Optical Sensor..
4.4. Types of Fiber Optical SensorTypes of Fiber Optical Sensor..
5.5. Physical Design AnalysisPhysical Design Analysis..
6.6. EquationsEquations
7.7. Fiber Probe PropertiesFiber Probe Properties
8.8. Analytical ResultAnalytical Result
9.9. ConclusionConclusion..22
Basic FOSBasic FOS
FIBER OPTIC SENSOR :
• A sensor that measures a physical quantity based onits modulation on the intensity, spectrum, phase, orpolarization of light traveling through an opticalfiber.
Advantages :1. Compact size.2. Multi functional.3. Remote Accesible.
4. Multiplexing
5. Resistant to harsh environment.
6. Immunity to electro-magnetic interference
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Typical Fiber Optical Sensor MechanismTypical Fiber Optical Sensor Mechanism
Light source Focus lens
Photo-detector
Light source Focus lens
Reflection Measurement
Transmission Measurement
Coupler
Sensing element
Photo-detector
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Configuration of Fiber Optical SensorConfiguration of Fiber Optical SensorPoint sensor: detect measurand variation only in the vicinity of the sensor
Multiplexed sensor:Multiple localized sensors are placed at intervals along the fiber length.
Distributed sensor:Sensing is distributed along the length of the fiber
Opto-electronics
Output, M(t, Zi)
Opto-electronics
Output, M(t,z)
Opto-electronics
Sensing element
Output, M(t)
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Types of Fiber Optical SensorTypes of Fiber Optical Sensor
1.1. Intrinsic:Intrinsic:the effect of the the effect of the measurandmeasurand on the on the light being transmitted take place in light being transmitted take place in the fiberthe fiber
2.2. Extrinsic:Extrinsic:the fiber carries the light from the the fiber carries the light from the source and to the detector, but the source and to the detector, but the modulation occurs outside the fibermodulation occurs outside the fiber
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Types of Fiber Optical SensorTypes of Fiber Optical Sensor
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Types of Fiber Optical SensorTypes of Fiber Optical Sensor
IntensityIntensity--based: measure physic based: measure physic measurandmeasurand based on the intensity of the based on the intensity of the light detected through the fiber, e.g. fiber light detected through the fiber, e.g. fiber break, OTDRbreak, OTDR
InterferometricInterferometric (phase modulation): (phase modulation):
–– FabryFabry--perotperot Interferometer.Interferometer.
Grating Grating based (wavelength modulation)based (wavelength modulation)
–– Fiber Bragg Grating (FBG).Fiber Bragg Grating (FBG).
–– Long Period Fiber Grating (LPFG)Long Period Fiber Grating (LPFG)
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IntensityIntensity--based Optical Fiber Sensorbased Optical Fiber Sensor
Advantages:
• Simple signal processing
• Inexpensive measurement instrument
Disadvantages:
• Susceptible to power fluctuation of the light source
• Susceptible to fiber bending losses
• Variation in modal power distribution in Multi-mode fiber (MMF).
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IntensityIntensity--based Optical Fiber Sensorbased Optical Fiber Sensor
ReferenceReference: “Split: “Split--spectrum intensityspectrum intensity--based optical based optical fiber sensors for measurement of fiber sensors for measurement of microdisplacement, strain, and pressure”, by Anbo microdisplacement, strain, and pressure”, by Anbo Wang et al.Wang et al.
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Physical Design AnalysisPhysical Design Analysis
Model of refractive index Model of refractive index changes in swelling changes in swelling
silicone rubber coatingsilicone rubber coating
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Physical Design AnalysisPhysical Design Analysis
Extrinsic FabryExtrinsic Fabry--Perot Perot Interferometer (EFPI)Interferometer (EFPI)
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EquationsEquations
cos21
cos12 RR
Ir
Intensity normalized recipient a Intensity normalized recipient a FabryFabry--Perot cavity in Perot cavity in reflection of light reflection of light
where where RR is power reflectivity of interface on core and cladding is power reflectivity of interface on core and cladding indexindex
cos1rI
Error In Determining Phase DifferenceError In Determining Phase Difference::
Lnclad 4
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EquationsEquationsTThehe maximummaximum errorerror isis influencedinfluenced byby phasephase differencedifference atat22(m+(m+11//22)),, wherewhere mm isis anan integerinteger.. WhileWhile mminimuminimumerrorerror occursoccurs inin thethe rangerange ofof //22 atat qq--pointpoint ..
FabryFabry--perot perot Interferometer Interferometer and two beam and two beam approximationapproximation
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EquationsEquationsLLight reflectioight reflection n RR and transmission and transmission TT::
R1 and R2 can be obtained from the calculation of R1 and R2 can be obtained from the calculation of equation:equation:
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Fiber Probe Properties
Model of refractive index changes Model of refractive index changes in swelling silicone rubber layerin swelling silicone rubber layer
the equation for the equation for ammonia concentration on xammonia concentration on x--position from the position from the surface surface
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Fiber Probe Properties
the initial state of and
the equation for the equation for ammonia concentration on xammonia concentration on x--position position from the surface is givenfrom the surface is given
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1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
Ab
sorp
tio
n C
oe
ffci
en
t (/
cm)
Wavelength (nm)
Fiber Probe Properties
Absorption Coefficient of Silicone Absorption Coefficient of Silicone 1818
Analytical ResultAnalytical Result
Reflectivity of Reflectivity of light beam on light beam on refractive index refractive index differences differences SiliconeSilicone
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Analytical ResultAnalytical Result
RREFPI and EFPI EFPI and EFPI normalization normalization intensity of intensity of receiver result receiver result with differences with differences silicone silicone refractive indexrefractive index
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The function of vapor concentrationThe function of vapor concentration (a) Ammonia vapor concentration based on (a) Ammonia vapor concentration based on variation of cladding thickness; (b) Ammonia vapor concentration based on variation of cladding thickness; (b) Ammonia vapor concentration based on exposure timeexposure time
Analytical ResultAnalytical ResultAA BB
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Analytical ResultAnalytical Result
Ammonia Ammonia vapor vapor concentration concentration based on long based on long exposure timeexposure time
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ConclusionConclusionTheThe resultsresults showsshows thatthat ddeaeaddbandband ofof ammoniaammonia vaporvapordetectiondetection isis 00 s/mms/mm22 untiluntil 33..33 s/mms/mm22 wherewhere thethe rresponsivityesponsivitydetermineddetermined byby usingusing
andand thethe responseresponse timetime couldcould reachreach 1010 secondsecondss.. InIn sensorsensorstructure,structure, thethe fiberfiber waswas straightenedstraightened andand consumesconsumes lowlow airairpressurepressure inin testtest containercontainer toto enhanceenhance measurementmeasurementresponseresponse raterate.. TheThe ttestest containercontainer hashas toto bebe freefree fromfromcontaminationcontamination ofof vesselvessel reactionreaction toto testedtested steamsteam.. SmallSmalldifferencesdifferences levellevel willwill occuroccur inin longlong--durationduration responseresponse..
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Thanks for your attention,,,,,
Wassalam…..
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