Temperature Effects on a Fiber-Optic Evanescent Wave Absorption Sensor

1994 ◽  
Vol 48 (3) ◽  
pp. 387-393 ◽  
Author(s):  
G. L. Klunder ◽  
J. BÜrck ◽  
H.-J. Ache ◽  
R. J. Silva ◽  
R. E. Russo
Keyword(s):  
Absorption Spectra ◽  
Evanescent Wave ◽  
Near Infrared ◽  
Chemical Sensor ◽  
Fiber Optic ◽  
Absorption Bands ◽  
Wave Absorption ◽  
Influence Of Temperature On ◽  
Background Absorption ◽  
Cladding Material

A coiled fiber-optic chemical sensor has proven to be effective for the remote detection of volatile organic compounds, such as trichloroethylene (TCE), 1,1-dichloroethylene (DCE), and gasoline, in aqueous solutions. The analyte diffuses into the hydrophobic cladding and evanescent wave absorption spectra are measured in the near-infrared (1600–1850 nm) without the presence of the water absorption bands. In order for fiberoptic chemical sensors to operate effectively in remote environments, the influence of temperature on the sensor response must be known. The C-H bonds of the polysiloxane cladding material also have absorption bands in the near-infrared (NIR). Changes in temperature will change the density (i.e., concentration of C-H bonds) and refractive index of the cladding. Due to these effects, a temperature change of only 3°C from the reference has been shown to significantly alter the background absorbance. The temperature-dependent background absorption is found to be linear with the slope, and the values are proportional to the absorption coefficient of the cladding material. The intercept of the absorbance vs. temperature plot is found to follow the first derivative of the fiber sensor transmission spectrum. Evanescent wave absorption spectra of TCE solutions have been corrected for temperature.

New IR Fiber-Optic Chemical Sensor for in Situ Measurements of Chlorinated Hydrocarbons in Water

1993 ◽  
Vol 47 (9) ◽  
pp. 1484-1487 ◽  
Author(s):  
R. Krska ◽  
K. Taga ◽  
R. Kellner
Keyword(s):  
Evanescent Wave ◽  
Chemical Sensor ◽  
Fiber Optic ◽  
Silver Halide ◽  
Chlorinated Hydrocarbons ◽  
Sensor System ◽  
Absorption Bands ◽  
Relative Standard ◽  
Polycrystalline Silver

In this work the development and validation of a new MIR fiber-optic physicochemical sensor system for the continuous in situ analysis of chlorinated hydrocarbons (CHCs) in water is described. This study took advantage of the selectivity and sensitivity of fiber evanescent wave spectroscopy (FEWS) and the recent development of polycrystalline silver halide fibers. Since these fibers are transparent up to 20 μm, it was possible for the first time to develop a fiber-optic sensing system for CHCs, which have their strongest absorption bands > 10 μm. The silver halide fibers were coated with low-density polyethylene (LDPE) to enrich the CHC within the evanescent wave and to exclude the IR absorbing water from the measurement. For the quantitative in situ FEWS measurements, the coated silver halide fibers were coupled to a Fourier transform infrared (FT-IR) spectrometer using an off-axis parabolic mirror and a fiber-detector coupling system. This setup enabled the simultaneous in situ detection of the most common chlorinated hydrocarbons in concentrations between 1 to 50 mg/L in water by employing a fiber sensing part only 10 cm in length. A comparative analysis of waste water samples under participation of two experienced head space-gas chromatography (HSGC) laboratories showed good agreement of this continuous sensor system with the established standard techniques. The resulting working curve for tetrachloroethylene showed a correlation coefficient of r2 = 0.968 and a relative standard deviation of 17% in the range from 1 to 10 ppm.

scholarly journals Evanescent Wave Absorption Based S-shaped Fiber-optic Biosensor for Immunosensing Applications

2016 ◽  
Vol 168 ◽  
pp. 117-120 ◽  
Author(s):  
S. Chauhan ◽  
N. Punjabi ◽  
D. Sharma ◽  
S. Mukherji
Keyword(s):  
Evanescent Wave ◽  
Fiber Optic ◽  
Wave Absorption

Sapphire Fiber Evanescent Wave Absorption in Turbid Media

2009 ◽  
Vol 63 (8) ◽  
pp. 932-935 ◽  
Author(s):  
Jian Zhang ◽  
Feibing Xiong ◽  
Nicholas Djeu
Keyword(s):  
Glassy Carbon ◽  
Chemical Sensors ◽  
Evanescent Wave ◽  
Fiber Optic ◽  
Wave Interaction ◽  
Carbon Powder ◽  
Control Applications ◽  
Wave Absorption ◽  
Water Band ◽  
Sapphire Fiber

The influence of particulates on sapphire fiber evanescent wave absorption by water has been studied. Suspensions containing microsized graphite flakes and glassy carbon powder were used. Conventional free-space transmittance measurements of these samples showed strong absorption and scattering, which severely screened the absorption by water. However, the absorption on the water band determined from the evanescent wave interaction was unaffected by the presence of the graphite flakes. These results indicate that fiber-optic evanescent wave chemical sensors may be suitable for process control applications involving turbid reactor streams.

scholarly journals NIR Absorbance Characteristics of Deoxynivalenol and of Sound and Fusarium-Damaged Wheat Kernels

2009 ◽  
Vol 17 (4) ◽  
pp. 213-221 ◽  
Author(s):  
Kamaranga H.S. Peiris ◽  
Michael O. Pumphrey ◽  
Floyd E. Dowell
Keyword(s):  
Absorption Spectra ◽  
Near Infrared ◽  
Peak Height ◽  
Second Derivative ◽  
Absorption Bands ◽  
Derivative Spectra ◽  
Nir Absorption ◽  
Second Derivative Spectra ◽  
Food Reserves ◽  
Wheat Kernels

The near infrared (NIR) absorption spectra of deoxynivalenol (DON) and single wheat kernels with or without DON were examined. The NIR absorption spectra of 0.5–2000 ppm of DON in acetonitrile were recorded in the 350–2500 nm range. Second derivative processing of the NIR spectra and spectral subtractions showed DON absorption bands at 1408 nm, 1904 nm and 1919 nm. NIR spectra of sound and Fusarium-damaged kernels were also acquired using two instruments. Subtraction of average absorption spectra and second derivative spectra were evaluated to identify different NIR signatures of the two types of kernel. Differences in peak height and positions of the NIR absorption bands of the kernels were noted. At 1204 nm, 1365 nm and 1700 nm, the differences were in the heights of the absorption peaks. Such differences may be attributed to changes in the levels of grain food reserves such as starches, proteins and lipids and other structural compounds. Shifts in absorption peak positions between the two types of kernels were observed at 1425–1440 nm and 1915–1930 nm. These differences may arise from other NIR active compounds, such as DON, which are not common for the two types of kernel. Since the NIR absorption of DON may have contributed to the shifts between sound and Fusarium-damaged kernels, this study indicates the potential for NIR spectrometry to evaluate Fusarium damage in single kernels based on the DON levels.

Evanescent Wave Absorption Spectroscopy by Means of Bi-Tapered Multimode Optical Fibers

1998 ◽  
Vol 52 (4) ◽  
pp. 546-551 ◽  
Author(s):  
Anna Grazia Mignani ◽  
Riccardo Falciai ◽  
Leonardo Ciaccheri
Keyword(s):  
Optical Fiber ◽  
Optical Fibers ◽  
Absorption Spectroscopy ◽  
Evanescent Wave ◽  
Fiber Optic ◽  
Fiber Optic Sensors ◽  
Experimental Results ◽  
Multimode Optical Fiber ◽  
Wave Absorption ◽  
Reproducible Technique

This paper discusses the theoretical and experimental implications of tapering a multimode optical fiber with a view to its use in evanescent wave absorption spectroscopy. Good experimental results are obtained, showing the possibility of quadruplicating the absorbance efficiency. This easy and reproducible technique for taper fabrication is suitable for the implementation of both probes for spectroscopy and chemically assisted fiber-optic sensors.

Study of Analyte Diffusion into a Silicone-Clad Fiber-Optic Chemical Sensor by Evanescent Wave Spectroscopy

1995 ◽  
Vol 49 (11) ◽  
pp. 1636-1645 ◽  
Author(s):  
Dianna S. Blair ◽  
Lloyd W. Burgess ◽  
Anatol M. Brodsky
Keyword(s):  
Diffusion Coefficients ◽  
Evanescent Wave ◽  
Near Infrared ◽  
Chemical Sensor ◽  
Optical Element ◽  
Constant Diffusion ◽  
Infrared Spectral ◽  
Diffusion Rates ◽  
Two Parameter ◽  
Infrared Data

The diffusion rates of various polar and nonpolar analytes in dimethylsiloxane were examined with the use of a commercially available 200-μm silica-core/300-μm silicone-clad fiber as the optical element for evanescent wave spectroscopy in the near-infrared spectral region. An analytical solution to Fick's second law was used to model the time-dependent analyte concentration at the core/cladding interface. Successful fit of the analytical solutions to infrared data verifies the assumption of constant diffusion coefficients that is necessary to solve the equation. Transport rates of polar analytes in silicone can be estimated with the use of a single-parameter model that results in diffusion coefficients of 3.2 × 10−1, 1.6 × 10−1, 8.1 × 10−7, and 3.9 × 10−7 cm2/s for methanol, ethanol, 2-propanol, and n-butanol, respectively. Estimating the transport of larger nonpolar analytes in the silicone cladding requires a two-parameter model that includes a diffusion coefficient and an interfacial conductance term. For pentane, hexane, heptane, and cyclohexane the resultant diffusion coefficients and interfacial conductance parameters are 6.9 × 10−7, 4.6 × 10−7, 4.4 × 10−7, and 2.3 × 10−7 cm2/s and 2500, 2000, 2000, and 600 μm−1, respectively.

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