A directionally discriminable curvature sensor based on a chirped fiber Bragg grating Fabry–Perot interferometer (CFBG-FPI) is proposed and demonstrated by staggering two CFBGs in parallel in the fiber core with femtosecond laser point-by-point technology. The experimental results show that the light intensity of the interference dip tends to become stronger and weaker in two opposite bending directions, respectively, with a maximum sensitivity of 4.93 dB/m−1. This sensor has a temperature sensitivity of 2.31 × 10−4 dB/°C resulting in a cross-sensitivity as low as approximately 4.7 × 10−5 m−1/°C. The sensor is simple to manufacture, compact, and can be cascaded by multiple sensors to achieve multi-point detection, which is expected to play an important application in structural health detection.

In this work, a method is proposed and demonstrated for fabrication of chirped fiber Bragg gratings (CFBGs) in single-mode fiber by femtosecond laser point-by-point inscription. CFBGs with bandwidths from 2 to 12 nm and dispersion ranges from 14.2 to 85 ps/nm are designed and achieved. The sensitivities of temperature and strain are 14.91 pm/°C and 1.21 p m / µ ε , respectively. Compared to the present phase mask method, femtosecond laser point-by-point inscription technology has the advantage of manufacturing CFBGs with different parameter flexibilities, and is expected to be widely applied in the future.

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A novel high-sensitivity temperature sensor based on a chirped thin-core fiber Bragg grating Fabry–Perot interferometer (CTFBG-FPI) and the Vernier effect is proposed and demonstrated. With femtosecond laser direct writing technology, two CTFBG-FPIs with different interferometric cavity lengths are inscribed inside a thin-core fiber to form a Vernier effect system. The two FPIs consist of two pairs of CTFBGs with a full width at half maximum (FWHM) of 66.5 nm staggered in parallel. The interferometric cavity lengths of the two FPIs were designed to be 2 mm and 1.98 mm as the reference arm and sensing arm of the sensor, respectively. The temperature sensitivity of this sensor was measured to be −1.084 nm/°C in a range of 40–90°C. This sensor is expected to play a crucial role in precision temperature measurement applications.