Chuanxu Liu

In this paper, a novel hybrid-dual-microcavity (h-DMC) structure is proposed for the first time in order to achieve simultaneous salinity and temperature measurement with high sensitivity and high discrimination. The h-DMC structure is completed by proper arc-discharged large lateral-offset splicing and full-filling the temperature sensitive polymer. Based on the shared cladding, two parallel micro-cavity Mach-Zehnder interferometers are formed and respectively used to monitor the salinity and temperature variations of solution. The obtained superimposed transmission spectra are easily decoupled and precisely re-constructed due to the obvious spatial frequency difference. The average sensitivities of h-DMC can reach −2.34 nm/‰ and 5.26 nm/°C with high linearity and low measured errors, which correspond to the detection limit of 0.0085 ‰ and 0.0038 °C, respectively. Due to the merits of low cost and high yield, such an integrated fiber-optic dual-parameter sensor is very competitive and promising to high-precision marine environment monitoring.

In this paper, a novel fiber-optic curvature sensor is proposed and demonstrated based on the taper-assisted micro-cavity (T-MOC) structure. The fabrication parameters are experimentally compared and optimized, and the comprehensive tests are performed in terms of curvature and temperature. The results show that the curvature response is effectively improved through reducing the diameter of taper waist. The maximum sensitivity reaches -7.92 nm/m ^-1 when the diameter is ~30 μm, with a cross-sensitivity of 0.0137 °C/m ^-1 . Moreover, encapsulated by polydimethylsiloxane, the T-MOC structure is used as a wearable point of care device to monitor the health status of human body. Owing to the ultralow threshold detection of 0.067m ^-1 , both large bending change and weak neck pulse can be precisely measured with high signal-to-noise ratio and rapid time response.

In this paper, a cascaded all-fiber structure is proposed and demonstrated, which includes sensing Mach-Zehnder interferometer (SMZI) based on a joint-assisted open-cavity and referencing Fabry-Perot interferometer (RFPI) based on hollow-core fiber. The temperature sensitivity of SMZI is well guaranteed and greatly improved by the Vernier effect, while the axial-strain crosstalk is obviously compressed by lengthening the open-cavity to ~2600 μm. Experimental results show that, with magnification factor of 19.04, the temperature response reaches 1.525 nm/°C and the cross sensitivity is smaller than 0.02 °C/με. Additionally, rapid time responses of less than 0.8 s are verified in the field-tests of respiratory and gas lighter. The proposed scheme presents the capability to achieve the high-precision temperature-related engineering sensing and monitoring.

In this paper, we report a novel fiber-optic axial-strain sensor based on the bias-tapered micro-open -cavity structure. The comprehensive investigations of axial -strain response are theoretically and experimentally conducted with respects to the diameter and position of taper waist. The results show that the intensity variation is strongly related to the location of taper. When the diameter is ~30 μm, highly sensitive and linear intensity modulation (~0.043 dB/με) is gained by the bias position of ~210 μm. And for a small bias state, the wavelength response reaches 17 pm/με flatly and can be increased to 313.14 pm/με with the aid of Vernier effect. As a result, the detection resolution of ~0.2 με can be achieved in both intensity and wavelength modulated schemes. With the merits of compactness, repeatability and low cost, our sensor is very promising and potential in the high-precision axial-strain related engineering measurements.

In this paper, we report a tapered thin-core fiber based in-line Mach-Zehnder interferometer to improve the response of axial-strain. With the varied diameters of taper waist, the light field distributions are studied by beam propagation method, and the structures are fabricated by arc-discharged lateral offset splicing and tapering techniques. The comprehensive tests are then conducted and compared in terms of axial-strain and temperature. The experimental results show that, by reducing the diameter of taper waist, more than 400% enhancement of wavelength sensitivity can be gained, and the maximum reaches 4.07 pm/µε with the measured error of 3.6%. Moreover, owing to high consistency of temperature response, the near-zero crosstalk is presented by differential compensation method. Furthermore, owing to the merit of high repeatability and stability, our sensor is very practical and promising in the high-precision measurement and engineering monitoring.

In this paper, to enhance practicality, a novel tapered thin-core fiber (t-TCF) based modal interferometer is proposed and demonstrated experimentally. The light field distribution of t-TCF structure is investigated by a beam propagation method, and the quantitative relationship is gained between light intensity loss and waist diameter. Under ~30 μm waist diameter, multiple t-TCF based sensor heads are fabricated by arc-discharged splicing and taper techniques, and comprehensive tests are performed with respects to axial strain and temperature. The experimental results show that, with near-zero wavelength shift, obvious intensity strain response is exhibited and negative-proportional to the reduced length of TCF. Thus, the maximum sensitivity reaches 0.119 dB/με when the TCF length is equal to 15 mm, and a sub-micro-strain detection resolution (about 0.084 με) is obtained. Besides, owing to the flat red-shifted temperature response, the calculated cross-sensitivity of our sensor is compressed within 0.32 με/°C, which is promising for high precision strain related engineering applications.