Abstract

A broadband edge filter with linear dynamic ranges of 78.1 nm in wavelength and 91.54% in transmission loss has been demonstrated both theoretically and experimentally, which is achieved by using a helical long period fiber grating written in a graded-index few-mode fiber (GI-FMF-HLPG). As a typical application example of the proposed edge filter, a power-interrogated sensor was successfully proved. Benefited from the ultra-low value of group dispersion difference between the coupled modes in the graded-index few-mode fiber, the sensor not only achieves characteristics of ultra-wide linear dynamic ranges, but also has ultra-high sensing sensitivity. The maximum torsion sensitivity is 0.501 nm/(rad/m) under the torsion ranging from −22.4 to 22.4 rad/m and the maximum strain sensitivity is −4.05 pm/µε under the strain ranging from 0 to 2000 µε, which are much higher than those of conventional fiber-based sensors.

© 2023 The Author(s)