Liquid Core Fiber Interferometer for Simultaneous Measurement of Refractive Index and Temperature

In this review paper some recent advances on optical sensors based on photonic crystal fibres are reported. The different strategies successfully applied in order to obtain feasible and reliable monitoring systems in several application fields, including medicine, biology, environment sustainability, communications systems are highlighted. Emphasis is given to the exploitation of integrated systems and/or single elements based on photonic crystal fibers employing Bragg gratings (FBGs), long period gratings (LPGs), interferometers, plasmon propagation, off-set spliced fibers, evanescent field and hollow core geometries. Examples of recent optical fiber sensors for the measurement of strain, temperature, displacement, air flow, pressure, liquid-level, magnetic field, and hydrocarbon detection are briefly described.

Section: Coated Pcf Sensorsmentioning

confidence: 99%

Advances on Photonic Crystal Fiber Sensors and Applications

Portosi

Laneve

Falconi

et al. 2019

“…Consequently, extensive research combines various materials with photonic crystal fiber [ 1 , 2 ], hollow-core fiber (HCF) [ 3 , 4 ], twin-core fiber [ 5 ], and D-shaped fiber [ 6 ] for the fabricated FMZIs. The silica-based fibers combined with the other materials, including liquids [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], nanoparticles [ 13 , 14 ], and 2D materials (graphene) [ 15 , 16 , 17 , 18 , 19 ], would generate much higher sensitivity to external parameters than that of the intrinsic silica fibers. Various configurations for the FMZIs have been proposed in the literature and have been demonstrated their effectiveness [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”

Section: Introductionmentioning

confidence: 99%

“…The silica-based fibers combined with the other materials, including liquids [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], nanoparticles [ 13 , 14 ], and 2D materials (graphene) [ 15 , 16 , 17 , 18 , 19 ], would generate much higher sensitivity to external parameters than that of the intrinsic silica fibers. Various configurations for the FMZIs have been proposed in the literature and have been demonstrated their effectiveness [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Examples include an FMZI with anti-resonance based on an multi-mode fiber (MMF)-HCF-MMF structure for sensing application [ 21 ], tapered fiber-based FMZI for the refractive index (RI) and temperature (T) measurement [ 22 ], core-offset in-line FMZI [ 23 ], an in-line FMZI with thin-core fiber (TCF)-thin fiber-TCF [ 24 ], and SMF-HCF-SMF structures [ 12 , 20 , 28 , <...>…”

Section: Introductionmentioning

confidence: 99%

Highly Modulated In-Fiber Mach–Zehnder Interferometer Based on an Ultracompact Leaky-Guided Liquid Core

Lee

Zhuo

Liu

2022

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.

“…For these cases, it is quite important to systematically relate the changes observed in the reflected spectrum with the physical variables to be measured. To perform the measurements, some authors have proposed to establish linear relationships between the physical variables and either the dip position of some fringes [12] or the intensity or the shift of a resonant dip wavelength [5]. Other authors have proposed to use the Fourier transform to determine the harmonic components of a FPI's reflection spectrum and relate them with a physical variable [10].…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, they showed that the contrast of their spectral fringes was minimum when the refractive index of the exit medium was around 1.45. Another example of a dual sensor is the proposed in [12] which was implemented by splicing an isopropanol infiltrated hollow core fiber between two single-mode fibers. In that work, authors traced a dip of the spectrum to perform the temperature and refractive index measurements for operating dynamic ranges of 25-80°C and 1.333-1.376, respectively.…”

Section: Introductionmentioning

confidence: 99%

Optical Fiber FP Sensor for Simultaneous Measurement of Refractive Index and Temperature Based on the Empirical Mode Decomposition Algorithm

Rodríguez

Guzmán-Chávez

Baeza-Serrato

et al. 2020

In this work, a dual refractive index and temperature sensor based on an interferometric system and on the empirical mode decomposition (EMD) algorithm is presented. Here, it is shown that the EMD provides a comprehensive way to analyze and decompose complex reflection spectra produced by an interferometric filter build at the tip of an optical fiber. By applying the EMD algorithm, the spectrum can be decomposed into a set of intrinsic mode functions (IMF) from which the temperature and the refractive index can be easily extracted. Moreover, the proposed methodology provides a detailed insight of the behavior of this type of interferometric sensors and allows widening of the dynamic measurement ranges of both variables. Here, for proof of principle purposes, a filter based on a stack of three layers (two of them were thermo-sensitive) was fabricated. Finally, it is shown that the proposed methodology can decompose the experimental measured spectra and to determine the refractive index and the temperature, supporting the mathematical model.