Microtapered long period gratings: Non-destructive fabrication, highly sensitive torsion sensing, and tunable broadband filtering
A promising technology for non-destructive fabricating microtapered long period fiber gratings (MT-LPFGs) is demonstrated by periodically slight tapering single-mode fiber. Owing to the optimized microtapering technique, high-quality LPFGs with dip attenuations of about 40 dB, insertion loss <0.5 dB are easily fabricated by precisely controlling the slightly tapering process. In addition, based on the characteristics of the MT-LPFG, not only highly strain, bending and torsion sensing are investigated experimentally, but also all-fiber broadband and extremely deep (-70 dB) band-rejection filters are proposed and demonstrated. The performances of the sensors and filters are significantly improved several times compared with conventional technology.