Anti-resonant reflecting optical waveguides (ARROW) have attracted much attention for their properties of low dispersion, low nonlinear response and high damage threshold since its first demonstration. In recent years, various structures of anti-resonant-based fibers have been extensively investigated, including photonic crystal fibers (PCFs), negative curvature fiber, hollow-core fiber (HCF) and Kagome fibers. The anti-resonant mechanism is in widespread use for single-point or single parameter measurement, such as liquid level sensing, magnetic field sensing, gas pressure sensing, and humidity sensing. However, to the best of our knowledge, there are few reports about the study of multi-point or multi-parameter multiplexing scheme for ARROW-based sensing network.
To address these problems, the optical fiber sensing research group of professor Li Xia in Huazhong University of Science and Technology recently proposed and experimentally demonstrated a novel multiplexing sensing network of anti-resonant reflecting optical waveguide. It has been found that the high refractive index ring cladding of the waveguide can be considered as an FP etalon (as shown in Fig. 1). The wavelengths which satisfy the resonant condition will result in sharp periodic anti-resonant peaks, and the positions of sharp periodic transmission dips are independent of the capillary length, but dependent on the refractive indexes and thickness of the waveguide ring cladding (as shown in Fig. 2). Thus, the multiple ARROW of different cladding thickness can be cascaded. The temperature responses from each ARROW can be distinguished in wavelength domain (as shown in Fig. 3). Furthermore, the merits of low strain cross-sensitivity, easy fabrication capability and high spectral extinction ratio make the proposed multiplexing scheme an excellent candidate for performing multi-point and multi-parameter measurements in harsh environments.
The research achievement “Multiplexing of anti-resonant reflecting optical waveguides for temperature sensing based on quartz capillary”, was published in Optics Express in Dec. 10, 2018 (vol. 26, no. 25, pp. 33501-33509). The work is supported by the National Natural Science Foundation of China (NSFC) (No. 61675078).
Fig. 1. Schematic diagram of (a) waveguide structure (b) optical pathways in waveguide. Mode field distribution at (c) the resonant wavelength and (d) the anti-resonant wavelength.
Fig. 2. Schematic diagram of the experimental setup for temperature measurements.
Fig. 3. Transmission spectra of the waveguide with different thickness and multiplexing structure.
