Abstract
We proposed a novel sensor based on an ultracompact leaky-guided liquid core fiber Mach–Zehnder interferometer (LLCFMZI) for high modulation of an interference spectrum. The sensor structure is based on a micro-sized hollow-core fiber (HCF) splicing a tilt end face single-mode fiber (SMF) to create a miniature oblique gap for the effective access of different liquids. The liquid core with a relatively lower refractive index (RI) than the cladding can achieve a leaky-mode optical waveguide (LMOW) mechanism, and its volume is only approximately 7.85 pL. In addition, the utilized micro-length HCF can reduce the energy loss of core in the LMOW to obtain an acceptable extinction ratio (>30 dB) with high temperature (T) sensitivity in the interference spectra. Experimental results show that the interference spectra can be highly modulated within the wide measurement range of 1250–1650 nm with a steadily linear response for thermal effect. The measured temperature sensitivities (T-sensitivities) of various liquids of DI water, ethanol, and Cargille-liquid (nD = 1.305) are 0.8869, 4.4754, and 4.8229 nm/°C, and the corresponding measured thermal optics coefficient (TOC) are −4.16 × 10−5, −2.11 × 10−4, and −3.6 × 10−4 °C−1, respectively. Measurement results demonstrate that the used liquids with a higher TOC can obtain better T-sensitivity modulation. The highest experimental sensitivity of the liquid-core filled with Cargille-liquid (nD = 1.40) is up to +13.87 nm/°C with a corresponding TOC of −4.07 × 10−4 °C−1. Furthermore, the experimental and theoretical values are in good agreement according to FSR the measuring scheme that investigates the effectiveness of the proposed LLCFMZI.
Highlights
Accepted: 19 January 2022Fused silica fiber has intrinsic properties of low thermal optics coefficient (TOC), low thermal expansion coefficient (TEC), and high stiffness with low tensile, such that it is not sensitive to some sensing parameters.To achieve high sensitivity, numerous optical fiber sensors are combined with other materials by utilizing dispersion features to control the energy of the core and cladding in the optical waveguide, an approach which significantly changes the optical characteristics of the propagating core and cladding modes
The experimental and theoretical values are in good agreement according to Free spectral range (FSR) the measuring scheme that investigates the effectiveness of the proposed leaky-guided liquid core fiber Mach–Zehnder interferometer (LLCFMZI)
Numerous optical fiber sensors are combined with other materials by utilizing dispersion features to control the energy of the core and cladding in the optical waveguide, an approach which significantly changes the optical characteristics of the propagating core and cladding modes
Summary
Fused silica fiber has intrinsic properties of low thermal optics coefficient (TOC), low thermal expansion coefficient (TEC), and high stiffness with low tensile Numerous optical fiber sensors are combined with other materials by utilizing dispersion features to control the energy of the core and cladding in the optical waveguide, an approach which significantly changes the optical characteristics of the propagating core and cladding modes. The application of fiber-optic sensors combined with liquids entails changing the effective RI of the external surroundings [8], cladding modes [6,7,9], or core mode [4,12] for the FMZIs. In a section on changing the external surroundings of the fiber, the study of Zhu et al reported an FMZI based on tapered hollow optical fiber. The utilized micro-length liquid core fiber efficiently reduces the energy loss in the LMOW mechanism, as well as obtains a good extinction ratio (>30 dB) and high T sensitivity in the interference spectra.
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