Four-core fiber-based bending sensor

Abstract

A novel four-core fiber-based bending sensor has been proposed. The four-core fiber is used as the sensing element, the four cores of the fiber act as a four-beam interferometer, and the far-field interferogram grids with periodical distributions are formed on the fiber output end. Since the phase difference is a function of the radius of curvature, the change of the radius of curvature shifts the far-field interferometric grid pattern. A low-coherence laser diode with wavelength of 650 nm is adopted to illuminate the fiber, and the interferogram pattern in the farfield is recorded by a CCD camera. The relationship between the far-field grid pattern intensity distribution and the radius of curvature is established theoretically and confirmed experimentally.

Three-dimensional phase step profilometry with a multicore optical fiber

“…A micrometer mount is used to bend a constrained section of the fiber. The light travels further on the outside core of the bend than on the inside core, resulting in a phase shift [9,10].…”

A sensor for the direct measurement of curvature based on flexoelectricity

“…In addition to fiber-optic curvature sensors, an inexpensive conductive ink sensor that can detect curvature with relatively lower measurement range was reported in [13]. The wavelength-shift technique and the light interferometric technique can also be used to measure bending curvature [14,15], but these systems are complex and expensive.…”

Fiber-optic curvature sensor with optimized sensitive zone

“…An inexpensive conductive ink sensor can detect the curvature, but its measurement range is very narrow, from 0.01 to 0.1 mm À 1 [5]. The wavelength-shift technique and the light interferometric technique can also be used to measure the bending deformation [6,7], but these systems are complex and require expensive spectrometers. Based on the principle that the light transmission loss will increase suddenly under large curvatures, a fiber-optic sensor was proposed to monitor respiratory chest circumference [8][9][10].…”