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12 pages, 4756 KiB

Open AccessCommunication

A Fiber-Integrated CRDS Sensor for In-Situ Measurement of Dissolved Carbon Dioxide in Seawater

by Mai Hu, Bing Chen, Lu Yao, Chenguang Yang, Xiang Chen and Ruifeng Kan

Sensors 2021, 21(19), 6436; https://doi.org/10.3390/s21196436 - 27 Sep 2021

Cited by 20 | Viewed by 3331

Research on carbon dioxide (CO₂) geological and biogeochemical cycles in the ocean is important to support the geoscience study. Continuous in-situ measurement of dissolved CO₂ is critically needed. However, the time and spatial resolution are being restricted due to the challenges of very high submarine pressure and quite low efficiency in water-gas separation, which, therefore, are emerging the main barriers to deep sea investigation. We develop a fiber-integrated sensor based on cavity ring-down spectroscopy for in-situ CO₂ measurement. Furthermore, a fast concentration retrieval model using exponential fit is proposed at non-equilibrium condition. The in-situ dissolved CO₂ measurement achieves 10 times faster than conventional methods, where an equilibrium condition is needed. As a proof of principle, near-coast in-situ CO₂ measurement was implemented in Sanya City, Haina, China, obtaining an effective dissolved CO₂ concentration of ~950 ppm. The experimental results prove the feasibly for fast dissolved gas measurement, which would benefit the ocean investigation with more detailed scientific data. Full article

(This article belongs to the Special Issue Micro-/Nano-Fiber Sensors and Optical Integration Devices)

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10 pages, 4486 KiB

Open AccessArticle

Continuous-Wave Fiber Cavity Ringdown Pressure Sensing Based on Frequency-Shifted Interferometry

by Yiwen Ou, Chunfu Cheng, Zehao Chen, Zhangyong Yang, Hui Lv and Li Qian

Sensors 2018, 18(4), 1207; https://doi.org/10.3390/s18041207 - 16 Apr 2018

Cited by 16 | Viewed by 3667

Abstract

We present a continuous-wave fiber cavity ringdown (FCRD) pressure-sensing method based on frequency-shifted interferometry (FSI). Compared with traditional CRD or FCRD techniques, this FSI-FCRD scheme deduces pressure by measuring the decay rate of continuous light exiting the fiber ringdown cavity (RDC) in the spatial domain (i.e., the CRD distance), without the requirement for optical pulsation and fast electronics. By using a section of fiber with the buffer layer stripped in the fiber RDC as the sensor head, pressures were measured within the range from 0 to 10.4 MPa. The sensitivity of 0.02356/(km∙MPa) was obtained with a measurement error of 0.1%, and the corresponding pressure resolution was 0.05 MPa. It was found that the measurement sensitivity can be improved by enlarging the interaction length of the sensor head. The results show the proposed sensor has the advantages of simple structure, low cost, high sensitivity, and high stability in pressure detection. Full article

(This article belongs to the Section Physical Sensors)

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24 pages, 844 KiB

Open AccessReview

Frequency-Shifted Interferometry — A Versatile Fiber-Optic Sensing Technique

by Fei Ye, Yiwei Zhang, Bing Qi and Li Qian

Sensors 2014, 14(6), 10977-11000; https://doi.org/10.3390/s140610977 - 20 Jun 2014

Cited by 16 | Viewed by 8465

Abstract

Fiber-optic sensing is a field that is developing at a fast pace. Novel fiber-optic sensor designs and sensing principles constantly open doors for new opportunities. In this paper, we review a fiber-optic sensing technique developed in our research group called frequency-shifted interferometry (FSI). This technique uses a continuous-wave light source, an optical frequency shifter, and a slow detector. We discuss the operation principles of several FSI implementations and show their applications in fiber length and dispersion measurement, locating weak reflections along a fiber link, fiber-optic sensor multiplexing, and high-sensitivity cavity ring-down measurement. Detailed analysis of FSI system parameters is also presented. Full article

(This article belongs to the Special Issue State-of-the-Art Sensors in Canada 2014)

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27 pages, 1705 KiB

Open AccessReview

Chemical Sensing Using Fiber Cavity Ring-Down Spectroscopy

by Helen Waechter, Jessica Litman, Adrienne H. Cheung, Jack A. Barnes and Hans-Peter Loock

Sensors 2010, 10(3), 1716-1742; https://doi.org/10.3390/s100301716 - 2 Mar 2010

Cited by 111 | Viewed by 21814

Abstract

Waveguide-based cavity ring-down spectroscopy (CRD) can be used for quantitative measurements of chemical concentrations in small amounts of liquid, in gases or in films. The change in ring-down time can be correlated to analyte concentration when using fiber optic sensing elements that change their attenuation in dependence of either sample absorption or refractive index. Two types of fiber cavities, i.e., fiber loops and fiber strands containing reflective elements, are distinguished. Both types of cavities were coupled to a variety of chemical sensor elements, which are discussed and compared. Full article

(This article belongs to the Special Issue Laser Spectroscopy and Sensing)

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27 pages, 810 KiB

Open AccessReview

Fiber Loop Ringdown — a Time-Domain Sensing Technique for Multi-Function Fiber Optic Sensor Platforms: Current Status and Design Perspectives

by Chuji Wang

Sensors 2009, 9(10), 7595-7621; https://doi.org/10.3390/s91007595 - 28 Sep 2009

Cited by 98 | Viewed by 18318

Abstract

Fiber loop ringdown (FLRD) utilizes an inexpensive telecommunications light source, a photodiode, and a section of single-mode fiber to form a uniform fiber optic sensor platform for sensing various quantities, such as pressure, temperature, strain, refractive index, chemical species, biological cells, and small volume of fluids. In FLRD, optical losses of a light pulse in a fiber loop induced by changes in a quantity are measured by the light decay time constants. FLRD measures time to detect a quantity; thus, FLRD is referred to as a time-domain sensing technique. FLRD sensors have near real-time response, multi-pass enhanced high-sensitivity, and relatively low cost (i.e., without using an optical spectral analyzer). During the last eight years since the introduction of the original form of fiber ringdown spectroscopy, there has been increasing interest in the FLRD technique in fiber optic sensor developments, and new application potential is being explored. This paper first discusses the challenging issues in development of multi-function, fiber optic sensors or sensor networks using current fiber optic sensor sensing schemes, and then gives a review on current fiber optic sensor development using FLRD technique. Finally, design perspectives on new generation, multi-function, fiber optic sensor platforms using FLRD technique are particularly presented. Full article

(This article belongs to the Special Issue Laser Spectroscopy and Sensing)

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