Review of Seawater Fiber Optic Salinity Sensors Based on the Refractive Index Detection Principle

Li, Gaochao; Wang, Yongjie; Shi, Ancun; Liu, Yuanhui; Li, Fang

doi:10.3390/s23042187

Cited by 27 publications

(11 citation statements)

References 97 publications

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“…In these noisy conditions and once compensation has been applied, the sensor’s bulk sensitivity is 98.9 nm/RIU or 0.19 nm/% salinity (see results in Figures S17 and S18) which is in agreement with recently reported photonic salinity sensor sensitivities in the range of 0.06–5 nm/%. − Its LOD is then 0.1% salinity or 2.3 × 10 –4 RIU. For reference, Figure b shows measurements obtained while the sensor was neither heated nor vibrated.…”

Section: Resultsmentioning

confidence: 99%

Noise Tolerant Photonic Bowtie Grating Environmental Sensor

Li,

Suliali,

Sahoo

et al. 2024

ACS Sens.

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Resonant photonic refractive index sensors have made major advances based on their high sensitivity and contact-less readout capability, which is advantageous in many areas of science and technology. A major issue for the technological implementation of such sensors is their response to external influences, such as vibrations and temperature variations; the more sensitive a sensor, the more susceptible it also becomes to external influences. Here, we introduce a novel bowtieshaped sensor that is highly responsive to refractive index variations while compensating for temperature changes and mechanical (linear and angular) vibrations. We exemplify its capability by demonstrating the detection of salinity to a precision of 0.1%, corresponding to 2.3 × 10 −4 refractive index units in the presence of temperature fluctuations and mechanical vibrations. As a second exemplar, we detected bacteria growth in a pilot industrial environment. Our results demonstrate that it is possible to translate high sensitivity resonant photonic refractive index sensors into real-world environments.

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Section: Resultsmentioning

confidence: 99%

Noise Tolerant Photonic Bowtie Grating Environmental Sensor

Li,

Suliali,

Sahoo

et al. 2024

ACS Sens.

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“…This refractive index measurement method was suitable for monitoring the temperature, humidity, pressure, and concentration of biological analytes in a laboratory environment [21]. In 2023, G. Li et al proposed a seawater salinity sensor array, based on a micro/nanofiber Bragg grating (MNFBG) structure, for which the salinity sensitivity for the two cascaded sensor arrays was 8.39 pm/‰ and 7.71 pm/‰, while the temperature sensitivity was 8.28 pm/ • C and 8.03 pm/ • C. This method was suitable for refractive index measurements of marine samples in a laboratory environment [22,23]. In 2023, Y. Wang proposed a sensor for the simultaneous measurement of seawater salinity and temperature, based on surface plasmon resonance (SPR) and Mach-Zehnder interference (MZI), with the sensitivity of seawater temperature being approximately 316.72 pm/ • C with the temperature changing from 20 • C to 45 • C, and the sensitivity of seawater salinity being 429.72 pm/‰ [24].…”

Section: Introductionmentioning

confidence: 99%

High-Sensitivity Seawater Refraction Index Optical Measurement Sensor Based on a Position-Sensitive Detector

Zhou,

Li,

Zhou

et al. 2024

Sensors

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The refractive index of seawater is one of the essential parameters in ocean observation, so it is necessary to achieve high-precision seawater refractive index measurements. In this paper, we propose a method for measuring the refractive index of seawater, based on a position-sensitive detector (PSD). A theoretical model was established to depict the correlation between laser spot displacement and refractive index change, utilizing a combination of a position-sensitive detector and laser beam deflection principles. Based on this optical measurement method, a seawater refractive index measurement system was established. To effectively enhance the sensitivity of refractive index detection, a focusing lens was incorporated into the optical path of the measuring system, and simulations were conducted to investigate the impact of focal length on refractive index sensitivity. The calibration experiment of the measuring system was performed based on the relationship between the refractive index of seawater and underwater pressure (depth). By measuring laser spot displacement at different depths, changes in displacement, with respect to both refractive index and depth, were determined. The experimental results demonstrate that the system exhibits a sensitivity of 9.93×10−9 RIU (refractive index unit), and the refractive index deviation due to stability is calculated as ±7.54×10−9 RIU. Therefore, the feasibility of this highly sensitive measurement of seawater refractive index is verified. Since the sensitivity of the refractive index measurement of this measurement system is higher than the refractive index change caused by the wake of underwater vehicles, it can also be used in various applications for underwater vehicle wake measurement, as well as seawater refractive index measurement, such as the motion state monitoring of underwater navigation targets such as AUVs and ROVs.

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“…The rapid advancement of modern technology and industry has led to an increased demand for accurate relative displacement measurements in various fields, including aerospace, precision engineering, and marine optical fiber sensing [1][2][3]. Laser ranging technology offers several advantages, such as noncontact * Author to whom any correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Frequency-modulated continuous-wave laser interferometry measurement method based on cross-correlation

Zhang,

Yan,

et al. 2024

Meas. Sci. Technol.

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Frequency-modulated continuous-wave (FMCW) laser interferometry technology holds significant potential for applications in the fields of ultraprecision manufacturing and high-precision sensing. This paper proposes a novel approach among current phase demodulation methods is based on cross-correlation to address the challenge of this technology. On the basis of nonlinear correction of a distributed feedback (DFB) laser, the intercepted beat frequency signal was first preprocessed with Z-score signal normalization and a smoothing filter. Subsequently, the interference beat signal was subjected to processing using a correlation method to derive the correlation function. Finally, the phase difference between adjacent beat signals was determined by pinpointing the maximum value of the cross-correlation function, enabling accurate displacement demodulation. Experimental validation was performed by constructing an FMCW laser interferometric displacement measurement system. The results indicated that the standard deviation of the displacement error for the cross-correlation method was 2.41 nm during static measurements. Compared to conventional maximum-point method, the static measurement error of the cross-correlation method has been reduced by 1.43 times. In dynamic measurements in the 500 µm range, The measurement error of the cross-correlation method has been reduced by 6.04 times, avoiding the dynamic measurement positioning problem of conventional feature point demodulation methods and making the measurement results more accurate. This advancement holds substantial practical value in the realm of phase demodulation in laser interferometry.

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Review of Seawater Fiber Optic Salinity Sensors Based on the Refractive Index Detection Principle

Cited by 27 publications

References 97 publications

Noise Tolerant Photonic Bowtie Grating Environmental Sensor

Noise Tolerant Photonic Bowtie Grating Environmental Sensor

High-Sensitivity Seawater Refraction Index Optical Measurement Sensor Based on a Position-Sensitive Detector

Frequency-modulated continuous-wave laser interferometry measurement method based on cross-correlation

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