: In recent years, the usage of fiber optic sensors, especially fiber grating sensors, have been increased. Long period fiber grating, or LPFG, has been one of the fiber sensor types that has received much of interests. Early publications in this field has been focused on feasibility studies and writing of gratings with different methods. More recent ones, however, have been on improving and adopting new writing methods, as well as introducing new applications. The main applications of LPFG are temperature strain sensing, vibration measurement, level and velocity of liquid measurement and etc. This thesis focuses on simulation, design, fabrication, and evaluation of long-period fiber grating sensors. In this regard, after first describing the LPFG, the equations governing the behavior of LPFG was driven. Using MATLAB for solving the equations, the behavior of the LPFG as a temperature sensor was predicted. In addition OptiGrating software was used to simulate LPFG sensors and the results were compared with previous analysis. On the experimental section, a LPFG sensor was fabricated using a micro-positioning system and a 10W CO 2 laser. The results showed that the predicted results by equation solving and software simulation was close to the experiment. Finally, the effects of different parameters on the behavior of the sensor was discussed. Keywords: Fiber optics, Long-Period Fiber Grating, LPFG, LPFG sensor, Simulation