Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD

Shimose, Y.; Okamoto, Tohru; Maruyama, A.; Aizawa, Masao; Nagai, Haruo

doi:10.1109/68.68057

Cited by 58 publications

(15 citation statements)

References 6 publications

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“…The processing method includes direct measurement of the signal magnitude from the bandpass filter while the laser wavelength is locked to a gas absorption line by use of a reference gas cell 9,12 and measurement of the variation in the signal amplitude when the laser wavelength is scanned across a gas absorption line. 7 In this section we examine the use of a wavelength-modulation spectroscopy technique in which the laser wavelength is modulated sinusoidally at a relatively higher frequency while the average wavelength is locked to or scanned across a gas absorption line.…”

Section: Wavelength-modulation Spectroscopy In the Frequency-modulatementioning

confidence: 99%

Multiplexing of optical fiber gas sensors with a frequency-modulated continuous-wave technique

Yu¹,

Jin²,

Ho³

et al. 2001

Appl. Opt.

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We report on the use of a frequency-modulated continuous-wave technique for multiplexing optical fiber gas sensors. The sensor network is of a ladder topology and is interrogated by a tunable laser. The system performance in terms of detection sensitivity and cross talk between sensors was investigated and found to be limited by coherent mixing between signals from different channels. The system performance can be improved significantly by use of appropriate wavelength modulation-scanning coupled with low-pass filtering. Computer simulation shows that an array of 37 acetylene sensors with a detection accuracy of 2000 parts in 10 6 for each sensor may be realized. A two-sensor acetylene detection system was experimentally demonstrated that had a detection sensitivity of 165 parts in 10 6 for 2.5-cm gas cells ͑or a minimum detectable absorbance of 2.1 ϫ 10 Ϫ4 ͒ and a cross talk of Ϫ25 dB.

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Section: Wavelength-modulation Spectroscopy In the Frequency-modulatementioning

confidence: 99%

Multiplexing of optical fiber gas sensors with a frequency-modulated continuous-wave technique

Yu¹,

Jin²,

Ho³

et al. 2001

Appl. Opt.

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“…For fiber gas sensor applications, the value of f is usually of the order of a few tens of kilohertz. 2,3,5,7 When the modulated laser light is passing through a gas sample with an ͑amplitude͒ absorption coefficient ␣͑͒, the output light intensity may be written as…”

Section: Wavelength Modulation Spectroscopy Based On Current Modulatimentioning

confidence: 99%

“…Because the average wavelength of the laser is locked to the center of the gas line ͑i.e., L0 ϭ g ͒ by the use of a reference loop and feedback control, 2,3,5,7 I͑t͒ may be written as…”

Section: Wavelength Modulation Spectroscopy Based On Current Modulatimentioning

confidence: 99%

“…[1][2][3][4][5] The advantages of fiber sensors include remote detection capability, safety in hazardous environments, immunity to electromagnetic fields, and so forth. The possible gases that can be detected include methane, acetylene, hydrogen sulfide, carbon dioxide, and carbon monoxide.…”

Section: Introductionmentioning

confidence: 99%

“…The frequency ͑wavelength͒ of the laser is modulated sinusoidally through the modulation of the injection current, while its average wavelength is locked at the center of the gas absorption line with a separated reference cell and feedback control electronics. 2,3,5,7 The modulated light signal from the source passes through a gas cell that contains a gas sample to be measured and is subsequently converted to an electric current through a photodiode. A lock-in amplifier is used to detect both the first-and the second-harmonic signals and either the secondharmonic signal or the ratio of the two harmonic signals may be used as a system output.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of interferometric noise in fiber-optic gas sensors with use of wavelength modulation spectroscopy

Jin

Demokan

et al. 1997

Appl. Opt.

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We report on interferometric noise limitation of fiber-optic gas sensors with highly coherent lasers and wavelength modulation spectroscopy. Interference between signal wave and reflected waves causes signal fluctuation in the output, which limits the performance of the sensing system. Sensor resolution limited by interferometric noise is calculated for a fiber-optic gas sensor with the Q͑6͒ absorption line of methane gas at approximately 1650 nm. The results are useful for system designers of this particular type of gas sensor.

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Fibre optic sensors

Stewart¹

1997

Sensor Systems for Environmental Monitoring

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Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD

Cited by 58 publications

References 6 publications

Multiplexing of optical fiber gas sensors with a frequency-modulated continuous-wave technique

Multiplexing of optical fiber gas sensors with a frequency-modulated continuous-wave technique

Investigation of interferometric noise in fiber-optic gas sensors with use of wavelength modulation spectroscopy

Fibre optic sensors

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