A Comprehensive Review of Optical Fiber Refractometers: Toward a Standard Comparative Criterion

Urrutia, Aitor; Villar, Ignacio Del; Zubiate, Pablo; Zamarreño, Carlos R.

doi:10.1002/lpor.201900094

Cited by 132 publications

(74 citation statements)

References 298 publications

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“…This small size feature, taking advantage of the diameter of a standard single mode fiber (SMF) being typically 125 µm, is especially attractive in chemical detection applications where, as will be shown, a much smaller sample volume can be used due to the small size optical fiber. Optical fiber methods are very effective when measuring refractive index (RI), a measurement which is important in many chemical and biological applications [13].…”

Section: Introductionmentioning

confidence: 99%

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

et al. 2020

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A novel sensing system based on single mode optical fiber in reflective configuration has been developed to measure the critical meniscus height (CMH) of low volumes of liquids, which is then used to calculate the contact angle. The sensing system has been designed especially for very low volumes of liquids (e.g. bioliquids) and the work has demonstrated that measurements are possible with a minimum liquid volume of 5 µL. The sensing system is based on monitoring the spectral variation induced by the difference in the refractive index regions surrounding the fiber tip, at the air-liquid or liquid-liquid interfaces. From the experiments performed in water, (by immersing and extracting the fiber sensor in the liquid sample), it can be concluded that the CMH forming on the fiber decreases as the temperature increases. The change of temperature (in this experiment from 22 to 60 ℃) does not influence the CMH of the sample used in the evaluation (P3 mineral oil), giving an indication of its thermal stability. In addition, a fixed fiber was used to measure the variation in the liquid level when another fiber is immersed in the liquid. The error in the liquid level obtained in the work was small, at 0.34 ± 0.04 %. Such a sensor, allowing accurate measurements with very small quantities is especially useful where liquid sample volumes are limited e.g. biologically sourced liquids or specialized, expensive industrial material in the liquid phase.

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Section: Introductionmentioning

confidence: 99%

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

et al. 2020

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“…Experimentally, transmitted light from the core and cladding would partially overlap and produce interference fringes that would shift in response to variations in the index of the gaseous samples filling the core. A single-period fringe shift accounts for a 2 π variation of ϕ in Equation (1). The fringe shifts are visualized by a camera.…”

Section: Sensing Mechanismmentioning

confidence: 99%

“…Recently, research and development of fiber-optic gas refractometers has drawn tremendous attention due to its potential applications in both scientific and industrial fields, such as gas composition detection, gaseous lasers, environmental protection, homeland security, and atmosphere pressure monitoring [1,2].…”

Section: Introductionmentioning

confidence: 99%

Ultrasensitive Gas Refractometer Using Capillary-Based Mach–Zehnder Interferometer

Chen

et al. 2020

Sensors

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In this paper, we report a capillary-based Mach–Zehnder (M–Z) interferometer that could be used for precise detection of variations in refractive indices of gaseous samples. The sensing mechanism is quite straightforward. Cladding and core modes of a capillary are simultaneously excited by coupling coherent laser beams to the capillary cladding and core, respectively. An interferogram would be generated as the light transmitted from the core interferes with the light transmitted from the cladding. Variations in the refractive index of the air filling the core lead to variations in the phase difference between the core and cladding modes, thus shifting the interference fringes. Using a photodiode together with a narrow slit, we could interrogate the fringe shifts. The resolution of the sensor was found to be ~5.7 × 10−8 RIU (refractive index unit), which is comparable to the highest resolution obtained by other interferometric sensors reported in previous studies. Finally, we also analyze the temperature cross sensitivity of the sensor. The main goal of this paper is to demonstrate that the ultra-sensitive sensing of gas refractive index could be realized by simply using a single capillary fiber rather than some complex fiber-optic devices such as photonic crystal fibers or other fiber-optic devices fabricated via tricky fiber processing techniques. This capillary sensor, while featuring an ultrahigh resolution, has many other advantages such as simple structure, ease of fabrication, straightforward sensing principle, and low cost.

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“…Fiber Bragg gratings (FBG) consist of periodic perturbations of the refractive index along a fiber (generally, a single mode fiber) formed by exposure of the core to an intense optical interference pattern [1,2]. These perturbations lead to the generation of resonances in the optical transmission and reflection spectrum by coupling of light from the core mode to another co-propagating or counter-propagating mode that might be guided in the core or in the cladding of the optical fiber [3].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Fiber Bragg Gratings Inscribed in Thin Films Deposited on D-Shaped Optical Fibers

Imas

Zamarreño

Villar

et al. 2021

Sensors

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A fiber Bragg grating patterned on a SnO2 thin film deposited on the flat surface of a D-shaped polished optical fiber is studied in this work. The fabrication parameters of this structure were optimized to achieve a trade-off among reflected power, full width half maximum (FWHM), sensitivity to the surrounding refractive index (SRI), and figure of merit (FOM). In the first place, the influence of the thin film thickness, the cladding thickness between the core and the flat surface of the D-shaped fiber (neck), and the length of the D-shaped zone over the reflected power and the FWHM were assessed. Reflected peak powers in the range from −2 dB to −10 dB can be easily achieved with FWHM below 100 pm. In the second place, the sensitivity to the SRI, the FWHM, and the FOM were analyzed for variations of the SRI in the 1.33–1.4 range, the neck, and the thin-film thickness. The best sensitivities theoretically achieved for this device are next to 40 nm/RIU, while the best FOM has a value of 114 RIU−1.

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A Comprehensive Review of Optical Fiber Refractometers: Toward a Standard Comparative Criterion

Cited by 132 publications

References 298 publications

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

Monitoring of the Critical Meniscus of Very Low Liquid Volumes Using an Optical Fiber Sensor

Ultrasensitive Gas Refractometer Using Capillary-Based Mach–Zehnder Interferometer

Optimization of Fiber Bragg Gratings Inscribed in Thin Films Deposited on D-Shaped Optical Fibers

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