Affiliation:
1. Okinawa Institute of Science and Technology Graduate University
2. University of Limerick
3. Technological University Dublin
Abstract
In this Letter, we demonstrate a high-sensitivity vector bend sensor based on a fiber directional coupler. The fiber directional coupler is composed of two parallel waveguides inscribed within a no-core fiber (NCF) by a femtosecond laser. Since the two written waveguides have closely matched refractive indices and geometries, the transmission spectrum of the fiber directional coupler possesses periodic resonant dips. Such a fiber directional coupler exhibits a good bending-dependent spectral shift response due to its asymmetric structure. Experimental results show that bending sensitivities of −97.11 nm/m−1 and 58.22 nm/m−1 are achieved for the 0° and 180° orientations in the curvature range of 0–0.62 m−1, respectively. In addition, the proposed fiber directional coupler is shown to be insensitive to external humidity changes, thus improving its suitability in high-accuracy bending measurements.
Funder
National Natural Science Foundation of China
Natural Science Foundation of Heilongjiang Province
Fundamental Research Funds for the Central Universities
111 Project
Heilongjiang Touyan Innovation Team Program
Science Foundation Ireland
Subject
Atomic and Molecular Physics, and Optics