Joachim Walewski - Academia.edu (original) (raw)
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Papers by Joachim Walewski
Social Science Research Network, 2024
SSRN Electronic Journal, 2021
We present a simple phenomenological theory of polarisation spectroscopy and apply it in an asses... more We present a simple phenomenological theory of polarisation spectroscopy and apply it in an assessing fashion to measurements and detailed theoretical calculations. Onr model serves also to intorproto polarisation spectroscopy measurements of relative OH concentrations.
Modern Spectroscopy of Solids, Liquids, and Gases, 1995
In this document we provide an overview of use-case specific requirements for (future) IoT applic... more In this document we provide an overview of use-case specific requirements for (future) IoT applications and direct the reader to the pertinent literature.
IEEE Photonics Technology Letters, Oct 1, 2009
Spectrally efficient data transmission with white light-emitting diodes (LEDs) is a topic of incr... more Spectrally efficient data transmission with white light-emitting diodes (LEDs) is a topic of increasing interest. In this letter, we report a visible light communication link operating at 200+ Mb/s net transmission rate (230+ Mb/s gross) with a bit-error ratio for uncoded data below 10 3. The link is based on a thin-film high-power phosphorescent white LED and offline signal processing of discrete multitone signals. Transmission at the brightness levels of about 1100 and 550 lx was investigated. Our results indicate that the achievable data rates are limited by detector noise.
Using a femtosecond fiber laser operating at 1560 nm, we have generated both longer and shorter w... more Using a femtosecond fiber laser operating at 1560 nm, we have generated both longer and shorter wavelengths in subsequent nonlinear fiber processes. These strategies provide a versatile and rugged light source for spectroscopic sensing.
Springer eBooks, 2013
This chapter addresses the question of how to generate concrete architectures with the IoT ARM, w... more This chapter addresses the question of how to generate concrete architectures with the IoT ARM, which is one of the many uses to which an architectural reference model can be put (see Chaps. 3 and 4). This topic was already touched upon in Section "Generation of Architectures" in Chap. 3, but it is covered in greater depth in this section. Note that we do not prescribe any specific architecting methodology for generating concrete architectures. Instead, this section outlines how and where
Springer eBooks, 2013
Views are used during the design and implementation phase of a concrete system architecture. They... more Views are used during the design and implementation phase of a concrete system architecture. They are defined in the following way: A view is a representation of one or more structural aspects of an architecture that illustrates how the architecture addresses one or more concerns held by one or more of its stakeholders (Rozanski and Woods 2011).
ABSTRACT Initial measurements of water vapor temperature by use of a Fourier-domain mode-locking ... more ABSTRACT Initial measurements of water vapor temperature by use of a Fourier-domain mode-locking laser were performed in a homogenous charge compression ignition engine. We assessed the potential of this FDML laser in combustion applications.
Applied Spectroscopy, Mar 1, 2006
A spatially resolved optical technique to measure gas temperature was assessed. The technique rel... more A spatially resolved optical technique to measure gas temperature was assessed. The technique relies on multiphoton absorption in inert gases. In contrast to laser-induced fluorescence, absorption is insensitive to collisional deactivation, and, in contrast to one-photon absorption, multiphoton absorption only occurs around the focus point of a typical laser beam. Multiphoton absorption features both the merits of being insensitive to quenching and of being a spatially resolved technique. In a case study we assessed two-photon absorption in xenon upon exciting the 5p 6 1 S 0 ! 5p 5 6p[5/2] 2 transition in xenon at a wavelength of 256 nm. The amount of light absorbed by xenon is related to the number density of the gas, and if the gas pressure is known then the gas temperature can be inferred from the number density. Two-photon absorbance was measured as a function of xenon number density and was used to validate a theoretical model of the absorption process. We discuss the circumnavigation of experimental challenges in applying this technique and analyze its precision in terms of the inferred gas temperature.
Applied Spectroscopy, Feb 1, 2008
Time-resolved spectroscopy can be compromised by optical beating, which is inherent to polychroma... more Time-resolved spectroscopy can be compromised by optical beating, which is inherent to polychromatic light sources and signals. For incoherent light sources, the random interference can partially or completely mask the spectroscopic signature of interest if the time dynamics of the interference are similar to or faster than that of the signature. Part I of this review focused on the theory of this process with an emphasis on thermal light sources, and in this part, four methods to mitigate or circumnavigate the detrimental impact of interference on time-resolved spectroscopy are reviewed: use of light with a controlled, non-stochastic phase, use of narrow-bandwidth light, averaging, and pulse referencing.
Applied Spectroscopy, Feb 1, 2008
Optical beating of polychromatic light is reviewed and its potential impact on time-resolved spec... more Optical beating of polychromatic light is reviewed and its potential impact on time-resolved spectroscopy is analyzed. In particular, the dependence of the quasi-random beating of thermal light on quantities including average power, spectral shape, and spectral width are reviewed.
Optics Letters, Oct 11, 2006
A dispersive grating compressor was included in a fiber ring laser to generate an unequally space... more A dispersive grating compressor was included in a fiber ring laser to generate an unequally spaced frequency comb spanning approximately 1549-1552 nm. Beating of nearby modes in the comb naturally assigns unique amplitude modulation frequencies to each spectral component emitted. The source contains no moving parts. The single-mode fiber-coupled output is directed through hydrogen cyanide gas and detected by a photodiode. A Fourier transform of a 1 ms record yields a spectrum that agrees with results from a grating spectrometer at 0.06 nm resolution. By engineering stable, broadband combs, the technique could result in a universal and simple approach for spectroscopy at almost arbitrary measurement speeds and spectral resolutions limited only by Fourier principles.
In this paper, we present experimental results on optical wireless transmission using commerciall... more In this paper, we present experimental results on optical wireless transmission using commercially available phosphorescent white-light LEDs. To the best of our knowledge, we demonstrate for the first time visible-light links operating at transmission rates up to 200 Mb/s over typical room distances and at reasonable bit-error-ratios. The experiments were performed using optical filtering at the receiver and on-off-keying as
Applied Spectroscopy, 2004
The potential of polarization spectroscopy for the detection of trace constituents in sooting com... more The potential of polarization spectroscopy for the detection of trace constituents in sooting combustion was investigated. It was demonstrated that the directionality of the polarization spectroscopy signal can be exploited to efficiently suppress incoherent interferences, e.g., Rayleigh scattering at soot particles. We also show how polarization spectroscopy compares with laser-induced fluorescence in this type of environment by applying both techniques to atmospheric-pressure, premixed propane/oxygen flames. The acquired signals were spatially resolved along the centerline of the flame, and measurements were conducted at several heights above the burner head and for medium to very high fuel-to-oxidizer ratios. Through our work we found that polarization spectroscopy can be applied even in the presence of large soot fractions. For most conditions, where laser-induced fluorescence suffered from interferences like elastic scattering, spatially filtered polarization spectroscopy signals were virtually background-free, and only for high soot loads did a noticeable background on the latter signal appear. This background likely stems from Mie scattering at very large soot particles.
Social Science Research Network, 2024
SSRN Electronic Journal, 2021
We present a simple phenomenological theory of polarisation spectroscopy and apply it in an asses... more We present a simple phenomenological theory of polarisation spectroscopy and apply it in an assessing fashion to measurements and detailed theoretical calculations. Onr model serves also to intorproto polarisation spectroscopy measurements of relative OH concentrations.
Modern Spectroscopy of Solids, Liquids, and Gases, 1995
In this document we provide an overview of use-case specific requirements for (future) IoT applic... more In this document we provide an overview of use-case specific requirements for (future) IoT applications and direct the reader to the pertinent literature.
IEEE Photonics Technology Letters, Oct 1, 2009
Spectrally efficient data transmission with white light-emitting diodes (LEDs) is a topic of incr... more Spectrally efficient data transmission with white light-emitting diodes (LEDs) is a topic of increasing interest. In this letter, we report a visible light communication link operating at 200+ Mb/s net transmission rate (230+ Mb/s gross) with a bit-error ratio for uncoded data below 10 3. The link is based on a thin-film high-power phosphorescent white LED and offline signal processing of discrete multitone signals. Transmission at the brightness levels of about 1100 and 550 lx was investigated. Our results indicate that the achievable data rates are limited by detector noise.
Using a femtosecond fiber laser operating at 1560 nm, we have generated both longer and shorter w... more Using a femtosecond fiber laser operating at 1560 nm, we have generated both longer and shorter wavelengths in subsequent nonlinear fiber processes. These strategies provide a versatile and rugged light source for spectroscopic sensing.
Springer eBooks, 2013
This chapter addresses the question of how to generate concrete architectures with the IoT ARM, w... more This chapter addresses the question of how to generate concrete architectures with the IoT ARM, which is one of the many uses to which an architectural reference model can be put (see Chaps. 3 and 4). This topic was already touched upon in Section "Generation of Architectures" in Chap. 3, but it is covered in greater depth in this section. Note that we do not prescribe any specific architecting methodology for generating concrete architectures. Instead, this section outlines how and where
Springer eBooks, 2013
Views are used during the design and implementation phase of a concrete system architecture. They... more Views are used during the design and implementation phase of a concrete system architecture. They are defined in the following way: A view is a representation of one or more structural aspects of an architecture that illustrates how the architecture addresses one or more concerns held by one or more of its stakeholders (Rozanski and Woods 2011).
ABSTRACT Initial measurements of water vapor temperature by use of a Fourier-domain mode-locking ... more ABSTRACT Initial measurements of water vapor temperature by use of a Fourier-domain mode-locking laser were performed in a homogenous charge compression ignition engine. We assessed the potential of this FDML laser in combustion applications.
Applied Spectroscopy, Mar 1, 2006
A spatially resolved optical technique to measure gas temperature was assessed. The technique rel... more A spatially resolved optical technique to measure gas temperature was assessed. The technique relies on multiphoton absorption in inert gases. In contrast to laser-induced fluorescence, absorption is insensitive to collisional deactivation, and, in contrast to one-photon absorption, multiphoton absorption only occurs around the focus point of a typical laser beam. Multiphoton absorption features both the merits of being insensitive to quenching and of being a spatially resolved technique. In a case study we assessed two-photon absorption in xenon upon exciting the 5p 6 1 S 0 ! 5p 5 6p[5/2] 2 transition in xenon at a wavelength of 256 nm. The amount of light absorbed by xenon is related to the number density of the gas, and if the gas pressure is known then the gas temperature can be inferred from the number density. Two-photon absorbance was measured as a function of xenon number density and was used to validate a theoretical model of the absorption process. We discuss the circumnavigation of experimental challenges in applying this technique and analyze its precision in terms of the inferred gas temperature.
Applied Spectroscopy, Feb 1, 2008
Time-resolved spectroscopy can be compromised by optical beating, which is inherent to polychroma... more Time-resolved spectroscopy can be compromised by optical beating, which is inherent to polychromatic light sources and signals. For incoherent light sources, the random interference can partially or completely mask the spectroscopic signature of interest if the time dynamics of the interference are similar to or faster than that of the signature. Part I of this review focused on the theory of this process with an emphasis on thermal light sources, and in this part, four methods to mitigate or circumnavigate the detrimental impact of interference on time-resolved spectroscopy are reviewed: use of light with a controlled, non-stochastic phase, use of narrow-bandwidth light, averaging, and pulse referencing.
Applied Spectroscopy, Feb 1, 2008
Optical beating of polychromatic light is reviewed and its potential impact on time-resolved spec... more Optical beating of polychromatic light is reviewed and its potential impact on time-resolved spectroscopy is analyzed. In particular, the dependence of the quasi-random beating of thermal light on quantities including average power, spectral shape, and spectral width are reviewed.
Optics Letters, Oct 11, 2006
A dispersive grating compressor was included in a fiber ring laser to generate an unequally space... more A dispersive grating compressor was included in a fiber ring laser to generate an unequally spaced frequency comb spanning approximately 1549-1552 nm. Beating of nearby modes in the comb naturally assigns unique amplitude modulation frequencies to each spectral component emitted. The source contains no moving parts. The single-mode fiber-coupled output is directed through hydrogen cyanide gas and detected by a photodiode. A Fourier transform of a 1 ms record yields a spectrum that agrees with results from a grating spectrometer at 0.06 nm resolution. By engineering stable, broadband combs, the technique could result in a universal and simple approach for spectroscopy at almost arbitrary measurement speeds and spectral resolutions limited only by Fourier principles.
In this paper, we present experimental results on optical wireless transmission using commerciall... more In this paper, we present experimental results on optical wireless transmission using commercially available phosphorescent white-light LEDs. To the best of our knowledge, we demonstrate for the first time visible-light links operating at transmission rates up to 200 Mb/s over typical room distances and at reasonable bit-error-ratios. The experiments were performed using optical filtering at the receiver and on-off-keying as
Applied Spectroscopy, 2004
The potential of polarization spectroscopy for the detection of trace constituents in sooting com... more The potential of polarization spectroscopy for the detection of trace constituents in sooting combustion was investigated. It was demonstrated that the directionality of the polarization spectroscopy signal can be exploited to efficiently suppress incoherent interferences, e.g., Rayleigh scattering at soot particles. We also show how polarization spectroscopy compares with laser-induced fluorescence in this type of environment by applying both techniques to atmospheric-pressure, premixed propane/oxygen flames. The acquired signals were spatially resolved along the centerline of the flame, and measurements were conducted at several heights above the burner head and for medium to very high fuel-to-oxidizer ratios. Through our work we found that polarization spectroscopy can be applied even in the presence of large soot fractions. For most conditions, where laser-induced fluorescence suffered from interferences like elastic scattering, spatially filtered polarization spectroscopy signals were virtually background-free, and only for high soot loads did a noticeable background on the latter signal appear. This background likely stems from Mie scattering at very large soot particles.