Liquid level sensor based on dynamic Fabry–Perot interferometers in processed capillary fiber

Abstract

In this work, a novel optical fiber sensor capable of measuring both the liquid level and its refractive index is designed, manufactured and demonstrated through simulations and experimentally. For this, a silica capillary hollow-core fiber is used. The fiber, with a sensing length of 1.55 mm, has been processed with a femtosecond laser, so that it incorporates four holes in its structure. In this way, the liquid enters the air core, and it is possible to perform the sensing through the Fabry–Perot cavities that the liquid generates. The detection mode is in reflection. With a resolution of 4 μm (liquid level), it is in the state of the art of this type of sensor. The system is designed so that in the future it will be capable of measuring the level of immiscible liquids, that is, liquids that form stratified layers. It can be useful to determine the presence of impurities in tanks.

Free-access optomechanical liquid probes using a twin-microbottle resonator

“…The estimated resolution for the water level, especially in the PLL measurement, is much better than the previously reported liquid level meter based on fiber-technologies whose resolution is the order of the optical wavelengths [31]- [37]. This high resolution originates from the combination of the small mode volume of the mechanical modes and the ultrasensitive displacement measurement of the cavity optomechanical setup.…”

All-Fiber In-Line Twist Sensor Based on a Capillary Optical Fiber

“…The capillary fiber, being the simplest structure among hollow fibers (or microstructure fibers), has received a lot of attention in recent years because of its benefits, such as its simple structure, flexibility, low invasiveness, and low cost of manufacture [19]. Capillary fibers are now being studied for different sensing domains, including the refractive index [20,21], temperature [22], liquid level [23,24], strain [25], pressure [26], and curvature [27]. However, the aforementioned capillary fiber applications necessitate that all fibers be aligned and twist-insensitive.…”

Sensing Using Light: A Key Area of Sensors

“…Can terms, concepts, methods, effects, approaches, techniques, technologies, etc., so disparate, as mentioned in [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], all be considered under the same sensing umbrella?…”