A femtosecond laser-inscribed fine-core long-period grating with low temperature sensitivity

In order to reduce crosstalk caused by temperature during refractive index and strain testing, the temperature, refractive index and strain response characteristics of fine-core long-period fiber gratings were studied. A long-period fiber grating with a period of 50 mu m was successfully prepared on a single-mode fiber with a core diameter of 6 mu m using the femtosecond laser direct writing method. The results show that long-period fiber gratings processed with low laser energy in fine-core fibers have lower temperature sensitivity, and maintain a larger extinction ratio and better spectral quality. The loss peak of this fine-core long-period fiber grating drifts only 1.7 nm in the 20 similar to 700 degrees C temperature range. The grating is also highly responsive to changes in the refractive index. when ambient refractive index is in the range of 1.406 5 similar to 1.426 5, its sensitivity reaches 882.51 nm/RIU, and its strain sensitivity is -2.2 pm/mu epsilon. This fine-core long-period fiber grating can better reduce crosstalk caused by temperature in the refractive index and strain tests.