The PhD thesis focuses on the optical fiber sensors of FBG (Fiber Bragg Grating) and LPFG (Long Period Fiber Grating) types. New techniques and methods of analysis and synthesis will be examined and applied on special types of inscription. Novel interrogation topologies and devices will be proposed and will be experimentally evaluated. Applications on the structural health monitoring using FBG sensors and the detection of green house gases through the LPFG sensors will be developed. Apart from the phase mask inscription technique, the fs-Laser method of inscription will be applied on both silica and polymer fibers.