High-Temperature Vector Accelerometer Based on Eccentric Fiber Bragg Grating

Addressing the urgent need for high-temperature vector vibration monitoring in extreme environments such as aerospace and oil exploration, this paper proposes and develops a novel accelerometer based on femtosecond laser-engraved eccentric fiber Bragg gratings (FBGs) and nickel-coated reflectors. This sensor employs a highly localized FBG with a 10 mm length and 1μm eccentricity fabricated within a single-mode fiber. It utilizes asymmetric refractive index modulation to achieve direction-sensitive cladding mode coupling. Simultaneously, a 30-nm-thick nickel film is sputter-deposited onto the fiber end-face to form a single-ended reflection structure. This design eliminates complex processes like fiber taper drawing and eccentric fusion splicing, overcoming the stability limitations of existing vector sensors at elevated temperatures. Experimental results demonstrate spectral stability across the 25 ℃–1020 ℃ temperature range and effective vibration measurement at 800 ℃. At the room temperature and 800 ℃, the acceleration sensitivities are 0.169 V/g (R2=0.993) and 0.0743 V/g (R2=0.989), respectively, with a common frequency response range of 15 Hz–25 Hz. The maximum angular response sensitivities are 2.4 V/g and 1.2 V/g, respectively, fully validating its reliable vector detection capability across a wide temperature range. This study provides a compact, mechanically robust, and high-temperature-resistant solution for vibration monitoring in extreme environments.