Abstract
In this thesis, we propose a temperature-insensitive Fiber Bragg Grating strain sensor, using the new method of detecting the optical power to determine the level of stresses. We achieve temperature insensitivity by using two optical fiber Bragg gratings with similar reflection spectra.We can exploit stresses at this system to independently detect different status of various stresses at different positions. Furthermore, this system has zero-cross talk property. Our prototype, indeed, were able to detect, separately, the changes of stresses at different positions. This detection scheme is essential in multi-point systems. Because this system is also temperature insensitive, we can utilize it for stress detection in the environments with wide temperature variations.As for the effects of power fluctuation, we also provide a solution in this thesis. We used a division circuit to reduce power fluctuations .In the strain measurement scheme, we used an EDFA to be a broadband light source and then amplify light signals in order to achieve higher sensitivity of the detector. In practice, we can use a less expensive optical detector to detect changes in strain the fiber Bragg grating experiences, thus reducing cost associated with convention wavelength monitoring instruments. We can use the method to build a highly sensitive, highly accurate and temperature-insensitive multi-point fiber Bragg grating strain sensor. Because this sensor is well suited in different environment and is of low cost, this research has tremendous value in practice.