Two-dimensional vector bending sensor based on seven-core fiber Bragg gratings

Abstract

We demonstrated a two-dimensional vector-bending sensor by use of fiber Bragg gratings (FBGs) inscribed in a homogeneous seven-core fiber. Seven FBGs were simultaneously inscribed in each of all seven cores using a modified Talbot interferometer and a lens scanning method. The vector bending response of six outer-core FBGs was investigated at all 360° directions with a step size of 15°. The bending sensitivities of the six outer-core FBGs display six perfect '8'-shaped patterns in a polar-coordinate system. That is, they exhibit strong bending-direction dependence with a maximum sensitivity of 59.47 pm/m. The orientation and amplitude of the vector bending can be reconstructed using measured Bragg wavelength shifts of any two off-diagonal outer-core FBGs. So, the six outer-core FBGs have 12 combinations for bend reconstruction, which can be averaged across multiple reconstructions to develop an accurate two-dimensional vector bending sensor. The average relative error was lower than 4.5% for reconstructed amplitude and less than 2.8% for reconstructed orientation angle θ. Moreover, the seven-core FBGs offer several advantages such as a compact structure, fabrication flexibility, and the temperature compensating ability of central-core FBG.

Two-dimensional vector accelerometer based on Bragg gratings inscribed in a multi-core fiber

“…2, it is evident that there is a slight difference in the central wavelengths of these cores, where λ i (i = 1, 2, 4) for each core is 1542.14, 1542.52 and 1541.98 nm, respectively. This may result from the non-uniform UV exposure caused by the different spatial distribution of the cores [18,19]. During the vibration process, the outer cores of the MCF, indicate a red shift in the Bragg wavelength when the fiber is stretched.…”

Reflected power-based 2D bending sensor using femtosecond laser FBG inscription in multicore fiber

“…The experimental setup consists of two XYZ platforms separated an initial distance d. A fiber rotator is located on each platform [4]. As shown in Figure 4a, one platform is fixed, while the other moves on the X axis.…”

“…Moreover, bend sensing is improved from a fiber with multiple cores that incorporate FBGs, since bend causes stretching in one core and compression in the opposite [4]. In this way, with four cores it is possible to discern bending in a two-dimensional plane.…”

Highly Compact Vector Bending Sensor With Microfiber-Assisted Mach– Zehnder Interferometer

“…n recent decades, the demand for high precision curvature measurement has been consistently growing in the fields of mechanical engineering, crack monitoring, and aerospace detection, etc. Due to their distinguished advantages such as high sensitivity, fast response, structure flexibility, and immunity to electromagnetic interference, and thanks to the revolutionized development of optical fiber technology, a good variety of fiber-optic devices, such as fiber gratings [1][2][3], Fabry-Pérot cavity [4], and Mach-Zehnder interferometers (MZIs) [5][6][7], have been proposed for bending sensing applications in the past decades.…”