Multi-hydrogenated compounds monitoring in optical fibre manufacturing process by photoacoustic spectroscopy

Besson, J.; Schilt, Stéphane; Sauser, Florian; Rochat, Etienne; Hamel, Philippe; Sandoz, Frédéric; Niklès, Marc; Thévenaz, Luc

doi:10.1007/s00340-006-2361-4

Cited by 12 publications

(3 citation statements)

References 8 publications

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“…In this paper, we report the influence of molecular relaxation on hydrogen chloride (HCl) detection in different gas mixtures containing helium (He). HCl is an important indicator of gas purity in the manufacturing of the new zero-water-peak fibers used in optical telecommunication networks [7]. The manufacturing of the fiber preform is usually made by modified chemical vapor deposition and the carrier gas used in this process mainly consists of a mixture of oxygen (O 2 ) and helium.…”

Section: Introductionmentioning

confidence: 99%

Molecular relaxation effects in hydrogen chloride photoacoustic detection

Besson

Schilt²,

Thévenaz

2007

Appl. Phys. B

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A photoacoustic (PA) sensor has been developed to monitor hydrogen chloride at sub-ppm level in the 1740-nm region. The system was designed to control the process in the novel low-water-peak optical fiber manufacturing process. Relaxation effects in hydrogen chloride PA detection in oxygenhelium and nitrogen-helium gas mixtures are presented, showing that the generation of the PA signal is strongly affected by the ratio of these substances. In addition, the role of water vapor in the PA signal is investigated. Photoacoustic spectroscopy (PAS) is a widely recognized technique for its high performance in the detection of trace gases in various applications [1][2][3]. The main advantages of this technique are its intrinsically zero background nature and its achromaticity, which result in a very sensitive and simple setup arrangement suitable in a broad spectral region ranging from the ultraviolet to the mid infrared.The development of photoacoustic (PA) sensors operating in the near-infrared (NIR) range has strongly increased in recent years due to the excellent properties of the available diode lasers. Such laser sources provide single-mode emission (for instance distributed feedback (DFB) lasers) with narrow line width (typically a few MHz), an output power ranging from a few mW to several tens of mW, modulation capabilities and thousands of hours of operation. Moreover, their compact size and their fiber-coupled output make them easy to align with the PA cell.Despite its above-mentioned advantages, PAS is an indirect method since the optical energy absorbed by the molecules is detected through an acoustic wave generated in the gas due to thermal expansion resulting from the vibrationto-translation (V-T) relaxation of the excited molecules. Consequently, the conversion from optical to thermal energy depends on the physico-thermal properties of the gas, so that a calibration of the sensor is required. Whereas molecular re-

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Section: Introductionmentioning

confidence: 99%

Molecular relaxation effects in hydrogen chloride photoacoustic detection

Besson

Schilt²,

Thévenaz

2007

Appl. Phys. B

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“…PA detection has numerous applications [7] and in particular, the PA spectroscopy of gases at trace level [8][9][10] has gained popularity as evident by a steadily increasing number of publications. Previously, PA spectroscopybased sensors proved to be effective in gas concentration measurements under field and industrial circumstances [11][12][13][14][15]. A dual-channel PA system for on-line process monitoring of H 2 S concentration in NG streams was reported by Varga et al [4].…”

Section: Introductionmentioning

confidence: 99%

In situand wide range quantification of hydrogen sulfide in industrial gases by means of photoacoustic spectroscopy

Szabó

Mohácsi

Gulyas³

et al. 2013

Meas. Sci. Technol.

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This paper describes a photoacoustic spectroscopy-based detector of hydrogen sulfide (H2S) in biogas, natural gas and oil process technology. The instrument is capable of measuring H2S concentrations over four orders of magnitude (from a few ppm level up to several per cent) in changing gas mixtures. Problems caused by harsh industrial circumstances, contamination and widely varying composition of gases can be overcome by optimizing wavelength modulation, resonance frequency tracking and an easy-to-use method enabling in situ monitoring calibration. A diode laser emitting around 1.57 µm served as the excitation source; at this wavelength spectral overlap between H2S and CO2 is substantial. Spectral interference was eliminated by optimizing the amplitude of wavelength modulation; furthermore, a simplified calibration method was implemented taking advantage of a nearby absorption line of CO2 providing fast and economical measurements. Frequency dependence of the photoacoustic signal was determined by two methods to ensure accuracy. For 10 s integration time and 6800 Hz modulation frequency, the minimum detectable concentration was 6 ppm (3σ).

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“…In recent years, the increasing need and the more stringent requirements for multiple gas sensors in many fields such as environment, industry, military and so on [1][2][3][4][5][6][7]. All of these applications require high sensitivity, high selectivity, short response time and transportable instruments, which makes photoacoustic spectroscopy (PAS) a good candidate to full these needs.…”

Section: Introductionmentioning

confidence: 99%

Photoacoustic Resonant Cell Remodified from Helmholtz Cavity for Multi-Gas Sensing Using Infrared Lasers

Zhao

Zhao³

et al. 2013

KEM

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This paper presents method and performance of the photoacoustic resonant cell remodified from Helmholtz cavity that can be used to detect photoacoustic signal of multi-gas. This technique has its physical basis in a phenomenon called the photoacoustic effect. The experiment system is composed of a resonant Helmholtz cavity, a sensitive microphone and two infrared lasers with high adsorption capability and specificity to the analyte. In our experiments, the average optical power at the laser operating point is 200mW for the 972nm laser (H2O detection) and 800mW for the10.653um laser (CO2detection), which are modulated at two different frequencies f1=175Hz and f2=125Hz. The remodified Helmholtz resonant on-line and real time measurement of the water vapour (300ppm) and carbodioxide (300ppm) conducted at their respective resonant frequency shown large signals about 4.41mV and 19.77mV respectively. The result demonstrated this cell used to test multi-gas is also feasible.

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Multi-hydrogenated compounds monitoring in optical fibre manufacturing process by photoacoustic spectroscopy

Cited by 12 publications

References 8 publications

Molecular relaxation effects in hydrogen chloride photoacoustic detection

Molecular relaxation effects in hydrogen chloride photoacoustic detection

In situand wide range quantification of hydrogen sulfide in industrial gases by means of photoacoustic spectroscopy

Photoacoustic Resonant Cell Remodified from Helmholtz Cavity for Multi-Gas Sensing Using Infrared Lasers

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