Measurement of distributed Brillouin shift frequency using a novel Brillouin loop amplification circuit

2000 ◽  
Author(s):  
I. Yamashita
Keyword(s):  
Shift Frequency

scholarly journals Detailed Analysis of the Acoustic Mode Shapes of an Annular Combustion Chamber

1999 ◽  
Author(s):  
Günther Walz ◽  
Werner Krebs ◽  
Stefan Hoffmann ◽  
Hans Judith
Keyword(s):  
Boundary Conditions ◽  
Acoustic Mode ◽  
Mode Shapes ◽  
Maximum Deviation ◽  
Minor Importance ◽  
Velocity Of Sound ◽  
Fe Method ◽  
Shift Frequency ◽  
Space Dependence ◽  
Eigenfrequency Spectrum

To get a better understanding of the formation of thermoacoustic oscillations in an annular gasturbine combustor, an analysis of the acoustic eigenmodes has been conducted using the Finite Element (FE) method. The influence of different boundary conditions and a space dependent velocity of sound has been investigated. The boundary conditions actually define the eigenfrequency spectrum. Hence, it is crucial to know e.g. the burner impedance. In case of the combustion system without significant mixing air addition considered in this paper, the space dependence of the velocity of sound is of minor importance for the eigenfrequency spectrum leading to a maximum deviation of only 5% in the eigenvalues. It is demonstrated that the efficiency of the numerical eigenvalue analysis can be improved by making use of symmetry, by splitting the problem into several steps with alternate boundaries conditions, and by choosing the shift frequency ωs in the range of frequencies one is interested in.

A novel approach to estimating the Doppler shift frequency from quadrature mixer output

2017 ◽  
Vol 88 (7) ◽  
pp. 073503 ◽  
Author(s):  
M. Y. Wang ◽  
A. D. Liu ◽  
C. Zhou ◽  
J. Q. Hu ◽  
H. Li ◽  
...  
Keyword(s):  
Doppler Shift ◽  
Novel Approach ◽  
Shift Frequency

scholarly journals Using Open-Source Components to Process Interferometric TerraSAR-X Spotlight Data

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Michael Jendryke ◽  
Timo Balz ◽  
Houjun Jiang ◽  
Mingsheng Liao ◽  
Uwe Stilla
Keyword(s):  
Satellite Images ◽  
High Spatial Resolution ◽  
Las Vegas ◽  
Beam Steering ◽  
Object Oriented ◽  
Research Community ◽  
The Usa ◽  
Integrated Processing ◽  
Shift Frequency ◽  
Processing Steps

We address the processing of interferometric TerraSAR-X and TanDEM-X spotlight data. Processing steps necessary to derive interferograms at high spatial resolution from bi- and monostatic satellite images will be explained. The spotlight image mode is a beam steering technique focusing the antenna on a specific ground area. This results in a linear Doppler shift frequency in azimuth direction, which has to be matched to the master image. While shifting the interpolation kernel in azimuth during resampling, the frequency spectrum of the slave image is aligned to the master image. We show how to process bistatic TanDEM-X images and propose an integrated processing option for monostatic TerraSAR-X data in the Delft Object-oriented Radar Interferometric Software (DORIS). The paper focuses on the implementation of this algorithm for high-resolution spotlight InSAR in a public domain tool; hence, it becomes available to a larger research community. The results are presented for three test areas: Uluru in Australia, Las Vegas in the USA, and Lüneburg in Germany.

scholarly journals The Influence of Laser Linewidth on the Brillouin Shift Frequency Accuracy of BOTDR

2018 ◽  
Vol 9 (1) ◽  
pp. 58 ◽  
Author(s):  
Qing Bai ◽  
Min Yan ◽  
Bo Xue ◽  
Yan Gao ◽  
Dong Wang ◽  
...  
Keyword(s):  
Probe Pulse ◽  
Measurement Accuracy ◽  
Signal To Noise Ratio ◽  
Gain Spectrum ◽  
Laser Source ◽  
Laser Linewidth ◽  
Optical Time Domain Reflectometer ◽  
Brillouin Gain ◽  
Optical Time ◽  
Shift Frequency

This paper analyzes the influence of laser linewidth on the measurement accuracy of a frequency-scanning Brillouin optical time domain reflectometer (FS-BOTDR), allowing for both the width of Brillouin gain spectrum and the signal-to-noise ratio (SNR) of the BOTDR system. The measurement accuracy of the Brillouin frequency shift (BFS) is theoretically investigated versus the duration of the probe pulse and the linewidth of the laser source, by numerically simulating how a FS-BOTDR works and evaluating the Brillouin gain spectrum (BGS) width and the system SNR. The simulation results show that the BFS accuracy is improved as the laser linewidth becomes narrower when the probe pulse width is fixed. We utilize five types of lasers with respective linewidths of 1.05 MHz, 101 kHz, 10.2 kHz, 3.1 kHz, and 98 Hz to compare the BFS measurement accuracy over a ~10 km optical sensing fiber. The experimental results demonstrate that the root-mean-square error (RMSE) of BFS decreases with the laser linewidth narrowing from 1.05 MHz to 3.1 kHz, which is in good agreement with the numerical simulation. However, the RMSE of BFS increases when the laser linewidth is less than 3.1 kHz, which may arise from the coherent Rayleigh noise due to a too narrow laser linewidth. The results can provide a theoretical basis and experimental guidance for choosing the appropriate laser linewidth in BOTDR.

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