Twist measurement based on the transmission of fixed wavelength of a helical long-period fiber grating is studied. The single-mode fiber is spiraled by a welding machine. There are two resonance dips near 1473 nm and 1517 nm, with the pitch length around 782 μm. The experimental results show that the transmission near 1473 nm decreases along with contra-direction twist and increases along with co-direction twist. In contrast, the transmission near 1517 nm decreases along with co-direction twist and increases along with contra-direction twist. The relationships between the twist and the resonance wavelength, the twist and the transmission of resonance dips, the twist and the transmission of fixed wavelengths are studied, respectively. They all show linear relationship with the twist, and the slopes are about 100 nm·mm/rad, 36 dB·mm/rad, and 46 dB·mm/rad, respectively. The dual-wavelength ratio is studied, and the ratio also shows linear relationship with the twist. The twist sensitivity of I_1463.3 nm/I_1526.5 nm is about 0.79 each 0.01 rad/mm. This has great potential application in twist sensors.

研究了基于螺旋长周期光纤光栅固定波长传输的扭曲测量。单模光纤通过焊接机盘绕。在 1473 nm 和 1517 nm 附近有两个共振下降，节距长度约为 782 μm。实验结果表明，1473 nm附近的透射率随着反向扭曲而减小，随着同向扭曲而增加。相比之下，1517 nm 附近的透射率随着同向扭曲而减少，随着反向扭曲而增加。分别研究了扭曲与谐振波长、扭曲与谐振波谷的透射、扭曲与固定波长的透射之间的关系。它们都与扭曲呈线性关系，斜率约为 100 nm·mm/rad，36 dB·mm/rad，和 46 dB·mm/rad，分别为。研究了双波长比，该比值与扭曲也呈线性关系。I 的扭曲灵敏度_{1463.3 nm} /I _{1526.5 nm}约为 0.79，每 0.01 rad/mm。这在扭曲传感器中具有巨大的潜在应用。