Digital, phase-sensitive detection for in situ diode-laser spectroscopy under rapidly changing transmission conditions

Fernholz, T.; Teichert, H.; Ebert, Volker

doi:10.1007/s00340-002-0962-0

Cited by 124 publications

(54 citation statements)

References 2 publications

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“…processing both simulated and measured laser intensities with the same digital lock-in amplifier and low pass filter, which eliminates the need for the Fourier series formalism to simulate the WMS signals, and facilitates multi-harmonic detection [30,31]. In WMS, the laser current is varied by both a low frequency scan and a high frequency sinusoidal modulation, so that the frequency of the laser light, ν(t), is given by…”

Section: Calibration-free Wavelength Modulation Spectroscopy Schemementioning

confidence: 99%

In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

Schmidt

2015

Appl. Phys. B

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Section: Calibration-free Wavelength Modulation Spectroscopy Schemementioning

confidence: 99%

In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

Schmidt

2015

Appl. Phys. B

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“…Fourier-based signal retrieval is in principle equivalent to lock-in based signal retrieval, but much more flexible. A detailed description is outside the scope of this paper and can be found elsewhere [20][21][22]. Briefly, a complex time representation of the desired WMS harmonic is retrieved by selecting only the positive harmonic component with a window function in the Fourier plane (see Fig.…”

Section: Signal Processing-harmonic Detectionmentioning

confidence: 99%

Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm

et al. 2011

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High-sensitive multi-species detection around 1550 nm using a modulated grating Y-branch, MG-Y, diode laser tunable between 1529 nm and 1565 nm is presented. The MG-Y diode laser is based on the Vernier effect of two modulated gratings, and exhibits quasi-continuous tuning over 36 nm. Multi-species detection is achieved by fast sequential scanning of single absorption lines of CH 4 , CO, C 2 H 2 , and CO 2 distributed over the tuning range of the diode laser. The laser wavelength is scanned about 10 GHz around each absorption line for 5 ms and this is followed by a discrete large jump in operating wavelength to the next line.The MG-Y diode laser has a good repeatability in output frequency between sequential scan segments (<10 MHz) enabling averaging of the scans. The setup employs digital wavelength modulation spectroscopy, dWMS, with Fourier-

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“…Traditionally, WMS relies on analog function generators for laser modulation, lock-in amplifiers for detection of signal harmonics, and oscilloscopes for data acquisition. By synchronizing data acquisition with function generators for laser modulation, it is possible to simultaneous record multiple WMS harmonics without the need of lock-in amplifiers [13]. The WMS system can be further simplified by employing a single plug-in board with synchronized outputs and inputs for laser modulation and data acquisition [14].…”

Section: Introductionmentioning

confidence: 99%

Clinical system for non-invasive in situ monitoring of gases in the human paranasal sinuses

Lewander¹,

Guan²,

Svanberg³

et al. 2009

Opt. Express

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We present a portable system for non-invasive, simultaneous sensing of molecular oxygen (O 2 ) and water vapor (H 2 O) in the human paranasal cavities. The system is based on high-resolution tunable diode laser spectroscopy (TDLAS) and digital wavelength modulation spectroscopy (dWMS). Since optical interference and non-ideal tuning of the diode lasers render signal processing complex, we focus on Fourier analysis of dWMS signals and procedures for removal of background signals. Clinical data are presented, and exhibit a significant improvement in signal-to-noise with respect to earlier work. The in situ detection limit, in terms of absorption fraction, is about 5 × 10 −5 for oxygen and 5 × 10 −4 for water vapor, but varies between patients due to differences in light attenuation. In addition, we discuss the use of water vapor as a reference in quantification of in situ oxygen concentration in detail. In particular, light propagation aspects are investigated by employing photon time-of-flight spectroscopy. 4971-4975 (1988). 24. R. Engelbrecht, "A compact NIR fiber-optic diode laser spectrometer for CO and CO 2 : analysis of observed 2f wavelength modulation spectroscopy line shapes," Spectrochim. Acta A 60, 3291-3298 (2004).

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Digital, phase-sensitive detection for in situ diode-laser spectroscopy under rapidly changing transmission conditions

Cited by 124 publications

References 2 publications

In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

In situ H2O and temperature detection close to burning biomass pellets using calibration-free wavelength modulation spectroscopy

Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm

Clinical system for non-invasive in situ monitoring of gases in the human paranasal sinuses

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