Ultralow-Duty-Cycle Amplitude-Sampled LPFG Using Deep Tapering and Its Application to Cross-Sensitivity-Free Multiparameter Sensor

A novel amplitude-sampled long-period fiber grating with deep tapering (AS-LPFG-DT) is proposed and experimentally demonstrated, functioning as a multichannel LPFG that efficiently generates multiple parallel resonance dips with nearly identical channel spacing. Compared to previous methods, our approach achieves ultralow duty cycle and few numbers of sampling period due to the unparalleled coupling efficiency resulting from both refractive-index perturbation and geometric perturbation in the deep and symmetrical tapering structure. This significantly enhances effective channel count and covered bandwidth. Our configuration offers simplicity, ease of fabrication, flexibility, and high efficiency, making it highly promising for applications such as all-fiber multi-wavelength mode converters and wavelength division multiplexing sensors. As examples, we have successfully implemented 5-, 7-, and 15-channel AS-LPFGs-DT. Furthermore, we have demonstrated a strain and temperature sensor based on our proposed AS-LPFG-DT design that exhibits competitive sensing sensitivities while eliminating cross-sensitivity effects between these two parameters.