Fiber Bragg Grating Sensors for Measurement of Strain, Temperature, and Salinity

FIBER BRAGG GRATING SENSORS FOR MEASUREMENT OF STRAIN, TEMPERATURE, AND SALINITY Introduction  Fiber Bragg grating (FBG) sensors useful for measuring chemical, physical,biological parameters  Advantages over electrical sensors: compact, immune to electromagneticinterference, can work in extreme conditions Operating Principle  Bragg wavelength (λb) depends on grating period and effective refractiveindex  λb shifts with changes in temperature, strain, etc  Mathematical modeling relates λb shifts to changes in measurands Simulation and Design  Used Opti-grating and Opti-systems software  Gaussian apodized uniform grating gives high reflectivity, low delay, lowsidelobes Strain Sensor  0.12 nm wavelength shift per 100 microstrains  Linear response from 20-430 με  Sensitivity: 1.2 pm/microstrain Temperature Sensor  13.8 pm/°C sensitivity  Linear response from -10 to 150°C  Bragg wavelength increases with increasing temperature Salinity Sensor  Salinity simulated by changing surrounding refractive index  Sensitivity: 0.6 pm/(% concentration change)  Wavelength shifts with changing salinity Conclusion

 Single FBG sensor can measure strain, temperature, salinity  Simulation shows good linearity and sensitivity for all measurands  Potential for oceanography, structural health monitoring, etc