Two-dimensional vector accelerometer with single-channel measurement based on femtosecond laser direct-written cladding waveguides

This paper presents a novel two-dimensional (2D) vector accelerometer that utilizes cladding waveguides (CWGs) to couple a single-mode fiber (SMF) and a four-core fiber (FCF). By constructing the CWGs at the fusion point between an SMF and an FCF, the connection between the SMF core and the FCF cores is achieved. The symmetric CWGs are fabricated between the SMF and two orthogonal edge cores of an FCF using the slit beam shaping technique with a femtosecond laser. To detect bending and acceleration, two fiber Bragg gratings (FBGs) are inscribed in the FCF using the Plane-by-Plane (Pl-by-Pl) method. By monitoring the wavelength shifts of the FBGs on the two orthogonal edge cores, the required directional information can be measured simultaneously. The experimental results demonstrate a maximum acceleration sensitivity of 76.68 pm/g and 82.23 pm/g for the two orthogonal FBGs, respectively.