Investigation of long-period gratings for sensor applications

201 p.Long period fiber grating or LPG sensor has been gaining popularity due to its sensitivity to numerous perturbations such as temperature, strain and refractive index. The LPG has an advantage over other optical fiber sensors for refractive index sensing since the cladding region of the optical fiber, with LPG, is not required to be etched away in order to gain access to the evanescent field. Since the cladding modes propagates in the cladding within the LPG region of the optical fiber. The advantage is that the structural integrity of the optical fiber remains intact as compared to other optical fiber refractive index sensors with cladding etched away. Currently, a LPG sensor converts a measurand into wavelength. To interrogate the information would require expensive and complicated wavelength interrogation system. This will increase the overall system cost for industrial applications. In addition, other perturbations such as temperature and strain will affect the LPG wavelength, compromising the accuracy of the results. The aim of this research was the investigation of LPG for sensing applications such that the output from the LPG sensors is intensity-based instead of wavelength-based.DOCTOR OF PHILOSOPHY (EEE