Structure-Modulated Long-Period Fiber Gratings (SM-LPFGs) represent an advancement in fiber optic sensor technology, moving beyond traditional photosensitivity-based fabrication to achieve enhanced performance through the direct physical modification of the geometry of the fiber. This review. This study presents a simple Mach–Zehnder interferometer (MZI) to obtain the bimodal characteristics that realize simultaneous measurement of strain and temperature through cascading an ultra-long-period fiber grating and a knob-shaped taper. Study found that the ULPG can be used as both a mode-locker for pulse shaping and a comb filter for.