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MODULATION METHOD 2: WAVELENGTH MODULATED SENSORS (Fiber Optics Corrosion…
MODULATION METHOD 2: WAVELENGTH MODULATED SENSORS
Types of sensors
Physical sensors
Chemical sensors
FBG sensors
Basic setup:
Principle
A broadband source sends the input spectrum to the FBG's via a 2x2 coupler
the transmission spectrum missing wavelengths corresonding to Bragg's wavelength of the FBG's
refelection spectrum contains missing wavelengths
Variation in measurands at each FBG, shifts the refelected wavelengths accordingly
Commeercial FBG :
Transsmission and Reflection curve:
Theoretical background
Bragg wavelength :
The changes in strain/ temperature will cause the expression:
Strain Measurement
Wavelength shift:
Effective strain-optic constant:
Strain Sensitivity:
Temperature Measurement
Fractional Bragg wavelength shift for temperature change:
Fiber Optic Chemical Sensor (FOCS)
Spectroscopic parameters
Absorbance
Reflectance
Luminescence
Scattering
Fiber Optic probe
Y-extrinsic probe
Evanescent probe
Fiber Optics Corrosion Sensors
Corrosion Model for steel in concrete :
Expected reflected power output:
Experiment setup:
Experimental result:
FOCos Design
UMMI SHOBIRAH BINTI ALI
