High sensitivity optical fiber liquid level sensor based on a compact MMF-HCF-FBG structure

Abstract

An ultra-high sensitivity fiber liquid level sensor based on wavelength demodulation is proposed and demonstrated. The sensor is composed of a segment of multimode fiber and a large aperture hollow-core fiber assisted by a fiber Bragg grating (FBG). Interference occurs due to core mismatching and different modes with different effective refractive indices. The experimental results show that the liquid level sensitivity of the sensor is 1.145 nm mm−1, and the linearity is up to 0.996. The dynamic temperature compensation of the sensor can be achieved by cascading an FBG. Considering the high sensitivity and compact structure of the sensor, it can be used for real-time intelligent monitoring of tiny changes in liquid level.

Ultrasensitive liquid level sensor based on slice-shaped composite long period fiber grating

“…It is a latent candidate in the field of high-precision liquid level measurement or sensing. SMF-MMF-HCF-SMF/FBG with aligned spliced [21] 22 10 1145 (1.333 RI) 7.86 SRI-based etched chirped FBG [22] 7 5.6 1214 6.5…”

“…In the research of high-sensitivity liquid level measurement, some people proposed the MMF cascading hollow-core fiber (HCF) and FBG (SMF-MMF-HCF-SMF/FBG) with an aligned spliced structure [21] , surrounding RI (SRI)-based etched chirped FBG structure [22] , and MMF-HCF-FBG structure [23] . MMF has many modes and strong RI modulation ability, which can effectively shorten the grating length.…”

Multi-Parameter Sensors Based on Optical Reflective Coupler Probe

“…Kang et al proposed a novel in-fiber modal interferometer for liquid level sensing based on the cascaded quasi-microfiber and double-cladding fiber with a response of -0.972 dB/mm and a temperature sensitivity of 0.164 nm/°C [6]. The composite schemes with embedded FBGs are utilized to eliminate the inaccuracy of the measured liquid level caused by temperature crosstalk [10], [14]. Camilo et al proposed an OFLLS based on a FBG embedded into an epoxy resin diaphragm with a liquid level sensitivity of 2.8 pm/mm and a lower temperature crosstalk of 1.04 mm/°C [10].…”

All-Fiber Liquid-Level Sensor Based on In-Line MSM Fiber Structure

“…Another well-known liquid-level measurement method, mechanical method, suffers from its shortcomings of big size, low accuracy, and unsafety [3]. To date, there are many efforts devoted to the development of fiber-optic liquid-level sensors owing to their excellent features, such as high sensitivity, small size, immunity to electromagnetic interference, and resistance to harsh environments [4][5][6]. Recently, a number of fiber grating sensing structures, including fiber Bragg gratings (FBGs) [7,8], long period gratings (LPGs) [9,10], and tilted fiber Bragg gratings (TFBGs) [11,12], have been demonstrated for liquid-level measurement.…”