Broadband edge filter based on a helical long-period fiber grating and its application to a power-interrogated torsion sensor

A broadband edge filter with linear dynamic ranges of 40 n m in wavelength and 93 % in transmission loss has been demonstrated both theoretically and experimentally, which is achieved by using a helical long-period fiber grating (HLPG) operating near the dispersion turning point (DTP) of the L P 1 , 10 mode. To take full advantage of the wide dynamic ranges, the fabricated edge filter has been successfully used as a power-interrogated torsion sensor, and the torsion responsivity presented is about 0.501 nm/(rad/m), which is higher than most conventional HLPG-based torsion sensors. The results indicate that the proposed edge filter may find applications in any other kinds of power-interrogated sensors as well.