Secondary theoretical analysis of swelling


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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

  1. 1. Secondary Theoretical Analysis of Swelling Characteristic of Silicone Coating for Plastic Optical Fiber Sensor ( SPECTECH Research Group - Internal Seminar 11 November 2011, FKAB Meeting Room) Harry Ramza, Mohd Hazwan Harun, Ramza, Khairul Anuar Ishak, Mohammad Syuhaimi Ab-Rahman Ishak, Ab- Spectrum Technology Research Group Department Electrical, Electronic and System Engineering Universiti Kebangsaan Malaysia Bangi, Bangi, Selangor Darul Ehsan MALAYSIA1
  2. 2. Content 1. Basic FOS. FOS. 2. Typical Fiber Optical Sensor Mechanism 3. Configuration of Fiber Optical Sensor. Sensor. 4. Types of Fiber Optical Sensor. Sensor. 5. Analysis. Physical Design Analysis. 6. Equations 7. Fiber Probe Properties 8. Analytical Result 9. Conclusion. Conclusion.2
  3. 3. Basic FOS FIBER OPTIC SENSOR : • A sensor that measures a physical quantity based on its modulation on the intensity, spectrum, phase, or polarization of light traveling through an optical fiber. Advantages : 1. Compact size. 4. Multiplexing 2. Multi functional. 5. Resistant to harsh 3. Remote Accesible. environment. 6. Immunity to electro- magnetic interference3
  4. 4. Typical Fiber Optical Sensor Mechanism Transmission Measurement Photo-detector Light source Focus Sensing lens element Reflection Measurement Coupler Light source Focus lens Photo-detector4
  5. 5. Configuration of Fiber Optical Sensor Point sensor: detect Opto- electronics measurand variation Sensing element only in the vicinity of the Output, M(t) sensor Multiplexed sensor: Opto- Multiple localized sensors are electronics placed at intervals along the Output, M(t, Z ) i fiber length. Distributed sensor: Opto- electronics Sensing is distributed along the length of the fiber Output, M(t,z)5
  6. 6. Types of Fiber Optical Sensor 1. Intrinsic: the effect of the measurand on the light being transmitted take place in the fiber 2. Extrinsic: the fiber carries the light from the source and to the detector, but the modulation occurs outside the fiber6
  7. 7. Types of Fiber Optical Sensor7
  8. 8. Types of Fiber Optical Sensor Intensity-based: measure physic Intensity- measurand based on the intensity of the light detected through the fiber, e.g. fiber break, OTDR Interferometric (phase modulation): – Fabry-perot Interferometer. Fabry- Grating based (wavelength modulation) – Fiber Bragg Grating (FBG). – Long Period Fiber Grating (LPFG)8
  9. 9. Intensity-based Optical Fiber Sensor Intensity- 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).9
  10. 10. Intensity-based Optical Fiber Sensor Intensity- Reference: “Split-spectrum intensity-based optical Reference: “Split- intensity- fiber sensors for measurement of microdisplacement, strain, and pressure”, by Anbo Wang et al.10
  11. 11. Physical Design Analysis Model of refractive index changes in swelling silicone rubber coating11
  12. 12. Physical Design Analysis Extrinsic Fabry-Perot Fabry- Interferometer (EFPI)12
  13. 13. Equations Intensity normalized recipient a Fabry-Perot cavity in Fabry- reflection of light 1  cos  Ir  1  R  2 R cos  2 where R is power reflectivity of interface on core and cladding index I r  1  cos  Error In Determining Phase Difference: Difference: 4 nclad L   13
  14. 14. Equations The maximum error is influenced by phase difference at 2(m+1 2(m+1/2), where m is an integer. While minimum integer. error occurs in the range of /2 at q-point . Fabry-perot Fabry- Interferometer and two beam approximation14
  15. 15. Equations Light reflection R and transmission T: reflection R1 and R2 can be obtained from the calculation of equation:15
  16. 16. Fiber Probe Properties Model of refractive index changes in swelling silicone rubber layerthe equation for ammonia concentration on x-position from the x-surface16
  17. 17. Fiber Probe Properties the initial state of and the equation for ammonia concentration on x-position x- from the surface is given17
  18. 18. Fiber Probe Properties 1.E+07 1.E+06 1.E+05 1.E+04 Absorption Coeffcient (/cm) 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 1.E-08 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 Wavelength (nm)Absorption Coefficient of Silicone18
  19. 19. Analytical ResultReflectivity oflight beam onrefractive indexdifferencesSilicone19
  20. 20. Analytical ResultREFPI and EFPInormalizationintensity ofreceiver resultwith differencessiliconerefractive index20
  21. 21. Analytical Result A BThe function of vapor concentration (a) Ammonia vapor concentration based onvariation of cladding thickness; (b) Ammonia vapor concentration based onexposure time21
  22. 22. Analytical Result Ammonia vapor concentration based on long exposure time22
  23. 23. Conclusion The results shows that deadband of ammonia vapor ead detection is 0 s/mm2 until 3.3 s/mm2 where the responsivity determined by using and the response time could reach 10 seconds. In sensor seconds structure, the fiber was straightened and consumes low air pressure in test container to enhance measurement response rate. The test container has to be free from rate. contamination of vessel reaction to tested steam. Small steam. differences level will occur in long-duration response. long- response.23
  24. 24. Thanks for your attention,,,,, Wassalam…..24