Various structures are fabricated by a femtosecond laser to demonstrate the mechanism of proposed optical fiber sensors. The transmission spectra of square and ring resonators are detected, which proves the effectiveness of our sensor design, yet, with low Q-factors at this time. Surprisingly, significant coupling or interfering responses are detected for fiber trenches only (without a resonator) at a depth about 59 μm that just or barely overlaps the fiber core. A thinned-cladding zeolite long period fiber grating chemical sensor is presented. Also, a quantum multiscale model is proposed to investigate the femtosecond pulse and fiber interaction, which consists of the plasma model, improved two-temperature model first-principles calculation and molecular dynamics simulation for the free electron generation, electron-lattice heating, and phase change mechanism. Theoretic predictions are in agreement with the experimental results in terms of threshold fluence, ablation depth, size and profile.