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.
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription