Packaging and Functionalization of Fiber Bragg Grating Sensors for Various Sensing Applications.

Abstract

In our world, numerous sensors are found everywhere, making our lives simpler and more comfortable. Among these sensors, optical sensors have undergone expeditious development, providing good performance. In particular, Fiber optic sensors (FOSs) are known for their inherent advantages over traditional sensors, such as small footprint, light weight, higher sensitivity, immunity to Electro Magnetic Interference, etc. Fiber Bragg grating (FBG) is one such sensor that has gone through tremendous growth and development in the current years. FBGs, in their basic form, can sense strain and temperature. However, recently, several newer sensing applications of FBGs have been explored, and the present thesis is an attempt in this direction. It is known that FBG is very fragile to handle; Hence packaging plays a vital role in the proper functioning of the sensor by securing the device from external perturbations and breakage and further enhancing its performance and prolonging its life. In this thesis work, FBG sensor-based devices have been developed for certain biomedical applications; Novel packaging methods are designed and developed, which transduce the measured parameter to a secondary parameter that the FBG can sense. For example, an FBG based device has been developed, capable of effectively acquiring real-time, continuous, beat-to-beat radial arterial pulse pressure waveform in a clinical environment. In addition, this thesis explores the functionalization of clad etched FBG (e-FBG), sensors for water quality monitoring. The functionalization involves modifying the e-FBG surface and selecting the functional material to be coated on the eFBG, followed by ligand attachment concerning the target compound. As an experimental validation of the efficacy of functionalized e-FBGs, a few chemical sensing which includes sensing lead and arsenic in water and certain bio-sensing applications have been demonstrated. The sensor performance in detecting a particular analyte has been characterized by reproducibility, selectivity, dynamic range, sensitivity, and long-term stability.