&lt;title&gt;Distributed measurement of chemicals using fiber optic evanescent wave sensing&lt;/title&gt;

Buerck, Jochen; Sensfelder, Elke; Ache, Hans J.

doi:10.1117/12.260599

Cited by 5 publications

(3 citation statements)

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“…This method is obviously not applicable to field applications. In later investigations, fluorophores were excited by the evanescent field of excitation light propagating inside the core, as shown in Figure 12b, making distributed sensing more practical [69]. Distributed fluorescence measurement was also demonstrated in exposed-core MOFs [70].…”

Section: Overview Of Sensing Mechanisms For Dcsmentioning

confidence: 99%

A Review of Methods for Fibre-Optic Distributed Chemical Sensing

Thomas

Hellevang

2019

Sensors

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Chemical sensing is of great importance in many application fields, such as medicine, environmental monitoring, and industrial process control. Distributed fibre-optic sensing received significant attention because of its unique feature to make spatially resolved measurements along the entire fibre. Distributed chemical sensing (DCS) is the combination of these two techniques and offers potential solutions to real-world applications that require spatially dense chemical measurements covering large length scales. This paper presents a review of the working principles, current status, and the emerging trends within DCS.

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Section: Overview Of Sensing Mechanisms For Dcsmentioning

confidence: 99%

A Review of Methods for Fibre-Optic Distributed Chemical Sensing

Thomas

Hellevang

2019

Sensors

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“…Changes in the backscatter signal can be induced by a local increase the refractive index (RI), or by changing the absorption properties in the fiber cladding due to the extracted chemical species. These optical changes lead to a distinct pattern in the OTDR response function, namely a step drop signal, which can be clearly separated, from signals originating, e.g., from mechanical defects in the fiber 9,10 .…”

Section: Introductionmentioning

confidence: 99%

Distributed fiber optical HC leakage and pH sensing techniques for implementation into smart structures

Buerck

Vogel²,

Roth

et al. 2004

SPIE Proceedings

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Interaction of target molecules with the evanescent wave of light guided in optical fibers is among the most promising sensing schemes for building up smart chemical sensor technologies. If the technique of optical time domain reflectometry (OTDR) is combined with silicone-clad quartz glass fibers distributed chemical sensing is possible. Hydrocarbon (HC) detection and location is done by automated identification of the position of the corresponding step drop (light loss) in the backscatter signal induced by local refractive index increase in the silicone cladding due to a penetrating HC compound. A commercially available mini-OTDR was adapted to sensing fibers of up to nearly 2-kilometer length and location of typical HC fuels could be demonstrated. The instrument is applicable for fuel leakage monitoring in large technical installations such as tanks or pipelines with spatial resolution down to 1 m. A similar technique using measurements in the Vis spectral range is being developed for health monitoring of large structures, e.g., for early detection of corrosion caused by water ingress and pH changes in reinforced concrete. Here, a pH indicator dye and a phase transfer reagent are immobilized in the originally hydrophobic fiber cladding, leading to a pH induced absorption increase and a step drop signal in the backscatter curve. The configuration of the distributed sensing cables, the instrumental setups, and examples for HC and pH sensing are presented.

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“…Higher concentrations about 500 ppm lead to immediate and serious irritation of the neck and nose. Concentrations in the range 5000 -10000 ppm cause human´s death in 5 -10 minutes [2,3] . From these reasons, rapid and trustworthy detection of ammonia gas leaks is an important element of security systems at many industrial facilities.…”

Section: Introductionmentioning

confidence: 99%

Development of absorption fiber optic sensor for distributed measurement of ammonia gas

Aubrecht

Kalvoda

2013

Optical Sensors 2013

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Polymer-clad silica optical fibers are employed for development of different absorption optic fiber sensors of gaseous analytes. In our case, the physical principles of the detection are combined with a chemical reaction between analyte and suitable opto-chemical absorption reagents. Selected organometallic complex reagents with different lengths of lateral aliphatic chains are studied with respect to the type of central ions and their coordinative conditions to surrounding ligands. The effect of solvent type on solubility and the long-term stability of the prepared reagents in solid matrix are presented and discussed. Various methods are also tested in order to achieve an effective reagent immobilization into the polymer matrix, which creates optical fiber cladding. The chemical reaction of the reagents with ammonia based on ligand exchange process is accompanied by changes of visible-near-infrared optical absorption influencing via evanescent field on the guided light intensity. Experimental results suggest that the selected reagents provide optical properties suitable for practical sensing applications and that the sensitized PCS optical fibers could be used for detection of ammonia gas.

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<title>Distributed measurement of chemicals using fiber optic evanescent wave sensing</title>

Cited by 5 publications

References 0 publications

A Review of Methods for Fibre-Optic Distributed Chemical Sensing

A Review of Methods for Fibre-Optic Distributed Chemical Sensing

Distributed fiber optical HC leakage and pH sensing techniques for implementation into smart structures

Development of absorption fiber optic sensor for distributed measurement of ammonia gas

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