Sometimes signals can be stubbornly non-periodic. This can make digital signal processing so much more annoying. The supposedly simple act of plotting the spectrum ends up being a game of trial-and-error, or requires making a decision that involves prior knowledge of what one would actually like to know in the first place. We’ll have a …
Scalar Diffraction - Fourier
In an earlier post we had a look at various diffraction formalisms that either originated in the Huygens-Fresnel principle or led to essentially the same results. The principle modeled a field distribution in a aperture (or on a surface) as a source of infinitely many spherical waves whose amplitudes and phases were prescribed by the …
Nature Photonics
After what seems (to me) to have been several eons worth of experimenting, writing, re-writing, re-experimenting, more re-writing and then some more re-writing (all of which mostly by others), the all-optical FFT idea that was used at the IPQ department at KIT finally made it into Nature Photonics. When I got there in late ’09, …
MATLAB anonymous functions
MATLAB is a programming environment I’ve been using for maybe eight or nine years. For most of this time I made use of anonymous functions, but I have to admit without really knowing what I was doing. I just copy-paste-modified the examples in the fzero and quad documentation and hoped they would somehow work. Which, …
Scalar Diffraction - Imagery
In this post on the principles of scalar diffraction there were quite a number of integral expressions for diffraction of light, starting from the Huygens-Fresnel principle and applying various degrees of approximation. Integral formulations are usually very abstract and not very illustrative. However, with today’s available computer power we can turn these integrals into…
Bausparrechnen
Früher dachte ich, Bausparen ist nur was für Spießer. Aber früher hat Benzin auch nur ‘ne Mark gekostet. Heute bin ich Bausparer. Die richtige Bausparkasse zu finden ist aber alles andere als leicht. Auch wenn z.B. Finanztest gerne mal ein paar Beispiele durchrechnet [1], passen deren Musterfälle nie so richtig. Wie man das als Wissenschaftler …
Scalar Diffraction - Huygens, Fresnel, Fraunhofer
One can work years in fiber optic communications and not really have to care about diffraction, but when working with free-space light propagation and/or illuminated surfaces it’s better to know the difference between your Fresnel and your Fraunhofer diffraction, and what the heck the Huygens-Fresnel principle is all about.
homodyne versus heterodyne
The merits of homodyne versus heterodyne detection is somewhat of a crossover topic since it applies to both optical communication and interferometry. In this post we will start by deriving the detected signals for homodyne, heterodyne and intradyne detection.
the Epic Fail of Nyquist WDM
More or less the final act of my career as an academic researcher, I put the ideas of the post the Art of Nyquist WDM into a submission to Photonics Technology Letters – with a few extra simulations and figures that I thought showed the advantages and drawbacks of the concept quite well. Alas, I …
Memento
Letztens beim Aufräumen bin ich über eine alte Zeitkarte für den ÖPNV in Potsdam gestoßen – müsste so aus den frühen 80ern stammen. Für sechs Mark fuffzich konnte man unbegrenzt auf der Linie Hauptbahnhof–Fontanestraße und der Buslinie F (die fuhr auch vom Hauptbahnhof irgendwohin) fahren…