Abstract

Type II fiber Bragg gratings (FBGs) inscribed with femtosecond (fs) laser possess significant potential for high temperature sensing. In this work, we propose and demonstrate a method for fabricating a parallel-integrated ultra-short type II FBG (PI-US-FBG) by using an fs laser point-by-point technology. The PI-US-FBG, featuring by an ultra-short grating length of 80 µm, consists of six identical FBGs parallel-inscribed into a fiber core at different radial positions in the same cross section. The fabricated PI-US-FBG exhibits a broadband Gaussian-shape spectrum with a low reflectivity of ∼10%, an ultra-low out-of-band insertion loss of 0.01 dB, and a large full width at half maximum bandwidth of 9.4 nm. Moreover, this PI-US-FBG could be used as a high temperature sensor with a wide measurement range from 25 to 1000 °C, and an excellent linearity was achieved with a dual-wavelength differential detection. The temperature sensitivity could be increased from 0.00316 to 0.00945 (dB/ °C) by enlarging the wavelength spacing of the tunable laser. In addition, two cascaded PI-US-FBGs were used to precisely measure the temperature field distribution in a CO₂ laser spot with a very high spatial resolution of 100 µm. Hence, the proposed PI-US-FBGs could be used for a large-scale fiber sensor network, especially in future distributed temperature measurement with a high spatial resolution.

High thermal stability of ultra-low insertion loss type II cladding fiber Bragg grating based on femtosecond laser point-by-point technology

Dan Su and Xueguang Qiao
Opt. Express 30(6) 9156-9164 (2022)

Interrogation of weak Bragg grating sensors based on dual-wavelength differential detection

Rui Cheng and Li Xia
Opt. Lett. 41(22) 5254-5257 (2016)

Strain and high-temperature discrimination using a Type II fiber Bragg grating and a miniature fiber Fabry–Perot interferometer

Yajun Jiang, Dexing Yang, Yuan Yuan, Jian Xu, Dong Li, and Jianlin Zhao
Appl. Opt. 55(23) 6341-6345 (2016)

High-resolution interrogation of tilted fiber Bragg gratings using an extended range dual wavelength differential detection

François Ouellette, Jianfeng Li, Zhonghua Ou, and Jacques Albert
Opt. Express 28(10) 14662-14676 (2020)

Type IIa Bragg grating based ultra-short DBR fiber laser with high temperature resistance

Yang Ran, Fu-Rong Feng, Yi-Zhi Liang, Long Jin, and Bai-Ou Guan
Opt. Lett. 40(24) 5706-5709 (2015)