Inscription of Multiple Bragg Gratings in a Single-Mode Polymer Optical Fiber Using a Single Phase Mask and Its Analysis

Multiple Bragg gratings are inscribed in a photosensitive single-mode polymer fiber using phase mask method and also by applying strain to the fiber. Due to the large strain tuning range of the polymer fiber, multiple Bragg gratings are inscribed with a large peak wavelength separation between adjacent peaks. The effect of hysteresis of the polymer fiber is also considered and its influence on the fabrication of the grating is studied. From this paper, it is found that a fiber elongation up to 0.9% of the total fiber length can be used to inscribe multiple Bragg gratings and give a quality grating array. Fiber elongation >0.9% of the total length affects the grating reflectivity and bandwidth due to the creep and hysteresis developed in the polymer fiber from the large strain. Within the 0.9% elongation limit, multiple gratings can be inscribed with a maximum peak wavelength separation of 12 nm between adjacent fiber gratings. The fabricated single-mode polymer fiber Bragg grating array can be used in applications, where temperature and humidity compensations are required, while measuring the strain or as multipoint sensors.