The common problem of the OFDM systems is the high sensitivity to frequency offset caused by tuning oscillator instabilities and Doppler shifts induced by the channel. Time variances of the channel during one OFDM symbol interval destroy the orthogonality of different subcarriers and generate power leakage among subcarriers, known as Inter-Carrier Interference (ICI). ICI in OFDM systems degrade...

The linear Doppler shift is widely used to infer the velocity of approaching objects, but this shift does not detect rotation. By analyzing the orbital angular momentum of the light scattered from a spinning object, we observed a frequency shift proportional to product of the rotation frequency of the object and the orbital angular momentum of the light. This rotational frequency shift was stil...

Inhomogeneous broadening is ubiquitous in light-matter interactions [1]. When a laser beam interacts with a gas, the dominant broadening is typically due to the Doppler effect, which causes atoms to experience different laser frequencies depending on their velocities. For atoms embedded in crystals, the inhomogeneous broadening is a result of the shifts in the energy levels due to local variati...

A swept source based Fourier domain optical Doppler tomography (FDODT) system was developed. The technique is based on a phase-resolved method where phase information was retrieved from the reconstructed complex fringe signals. The aliasing effects and artifacts caused by lateral scanning and sample movement were removed with a signal processing technique. The standard deviation of the phase sh...

Under typical discharge conditions, atoms or molecules excited by electrons have a unique velocity component along the plasma electric field direction. This component results in Doppler shifts that can be observed and measured by a high resolution Fourier transform spectrometer. We show theoretically that if the upper state of a given transition suffers radiation trapping, its Doppler shift wil...

Optical Doppler shift demonstration experiments are not a simple task since the light source cannot usually be moved in a sufficiently smooth and uniform manner to keep the level of noise well below of that of the signal. For that reason most demonstration experiments are usually performed with sound or with microwaves. Previous works have been reported using a moving mirror in order to produce...

We demonstrate a technique to reduce first-order Doppler shifts in crossed atomic/molecular and laser beam setups by aligning two counterpropagating laser beams as part of a Sagnac interferometer. Interference fringes on the exit port of the interferometer reveal minute deviations from perfect antiparallelism. Residual Doppler shifts of this method scale with the ratio v/(4d) of the typical ato...

Measurements of the transverse Doppler effect have provided important confirmatory evidence for the validity of Einstein’s theory of special relativity (SR) as it pertains to time dilation. However, these investigations fall into two distinct categories depending on whether the light source or the detector is accelerated relative to the rest frame of the observer. In their original work employi...

The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source an...