Asymmetric Coated Direction Recognition Fiber Optic Interferometric Curvature Sensor

The existing directional recognition fiber optic interferometric curvature sensor is usually based on special optical fiber or complex microfabrication, which has problems such as high cost and fragile structure. This article proposes an asymmetrically coated direction recognition fiber optic interferometric curvature sensor. An MSM type fiber optic interferometer is fabricated, the high refractive index UV adhesive is coated on the lower half of the sensing single-mode fiber segment by a U-shaped soft groove. Then concave and convex bending are applied to the sensor separately, the energy of the core mode field is distributed along the central axis of the fiber, and the energy of the cladding mode field is always distributed in UV coating zone, which is located in the stretching and compression areas of the sensor. The interference valleys are blue shifted and red shifted respectively, achieving bending direction recognition and curvature sensing. The experimental results indicate that the sensor has a sensitivity of −20.92 nm/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for concave bending and 20.70 nm/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for convex bending within the curvature detection range of 0-1 m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup>. This article provides a new idea for the structural design and manufacturing method of directional recognition fiber optic interferometric curvature sensor. The sensor has high mechanicashl strength, simple manufacturing, low cost, and good application prospect.