scholarly journals Investigation of a Signal Demodulation Method based on Wavelet Transformation for OFDR to Enhance Its Distributed Sensing Performance

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2850 ◽  
Author(s):  
Kunpeng Feng ◽  
Jiwen Cui ◽  
Hong Dang ◽  
Xun Sun ◽  
Dong Jiang ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Wavelet Transformation ◽  
High Spatial Resolution ◽  
Morlet Wavelet ◽  
Distributed Sensing ◽  
Spatial Interval ◽  
Signal Demodulation ◽  
Short Time ◽  
Demodulation Method ◽  
Short Time Fourier Transformation

Optical fiber distributed sensing that is based on optical frequency domain reflectometer (OFDR) is a promising technology for achieving a highest spatial resolution downwards to several millimeters. An OFDR signal demodulation method that is based on Morlet wavelet transformation (WT) is demonstrated in detail to improve the resolution of distributed sensing physical quantity under a high spatial resolution, aiming at the trade-off between spatial and spectrum resolution. The spectrum resolution, spatial interval of the measured gauges, and spatial resolution can be manually controlled by adjusting the wavelet parameters. The experimental results that were achieved by the wavelet transformation (WT) method are compared with these by short time Fourier transformation (STFT) method and they indicate that significant improvements, such as strain resolution of 1 με, spatial resolution of 5 mm, average repeatability of 4.3 με, and stability of 7.3 με within one hour, have been achieved. The advantages of this method are high spatial and spectral resolution, robust, and applicability with current OFDR systems.

scholarly journals Distributed sensing technology of high-spatial resolution based on dense ultra-short FBG array with large multiplexing capacity

2017 ◽  
Vol 25 (23) ◽  
pp. 28112 ◽  
Author(s):  
Gui Xin ◽  
Li Zhengying ◽  
Wang Fan ◽  
Wang Yiming ◽  
Wang Changjia ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Distributed Sensing ◽  
Sensing Technology

scholarly journals High spatial resolution distributed sensing in optical fibers by Brillouin gain-profile tracing

2010 ◽  
Vol 18 (8) ◽  
pp. 8671 ◽  
Author(s):  
Tom Sperber ◽  
Avishay Eyal ◽  
Moshe Tur ◽  
Luc Thévenaz
Keyword(s):  
Spatial Resolution ◽  
Optical Fibers ◽  
High Spatial Resolution ◽  
Distributed Sensing ◽  
Gain Profile ◽  
Brillouin Gain

scholarly journals Monitoring of Snow Cover Ablation Using Very High Spatial Resolution Remote Sensing Datasets

2019 ◽  
Vol 11 (6) ◽  
pp. 699
Author(s):  
Remzi Eker ◽  
Yves Bühler ◽  
Sebastian Schlögl ◽  
Andreas Stoffel ◽  
Abdurrahim Aydın
Keyword(s):  
Remote Sensing ◽  
Time Series ◽  
Snow Cover ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Areal Extent ◽  
Very High Spatial Resolution ◽  
Short Time ◽  
Very High

This study tested the potential of a short time series of very high spatial resolution (cm to dm) remote sensing datasets obtained from unmanned aerial system (UAS)-based photogrammetry and terrestrial laser scanning (TLS) to monitor snow cover ablation in the upper Dischma valley (Davos, Switzerland). Five flight missions (for UAS) and five scans (for TLS) were carried out simultaneously: Four during the snow-covered period (9, 10, 11, and 27 May 2016) and one during the snow-free period (24 June 2016 for UAS and 31 May 2016 for TLS). The changes in both the areal extent of the snow cover and the snow depth (HS) were assessed together in the same case study. The areal extent of the snow cover was estimated from both UAS- and TLS-based orthophotos by classifying pixels as snow-covered and snow-free based on a threshold value applied to the blue band information of the orthophotos. Also, the usage possibility of TLS-based orthophotos for mapping snow cover was investigated in this study. The UAS-based orthophotos provided higher overall classification accuracy (97%) than the TLS-based orthophotos (86%) and allowed for mapping snow cover in larger areas than the ones from TLS scans by preventing the occurrence of gaps in the orthophotos. The UAS-based HS were evaluated and compared to TLS-based HS. Initially, the CANUPO (CAractérisation de NUages de POints) binary classification method, a proposed approach for improving the quality of models to obtain more accurate HS values, was applied to the TLS 3D raw point clouds. In this study, the use of additional artificial ground control points (GCPs) was also proposed to improve the quality of UAS-based digital elevation models (DEMs). The UAS-based HS values were mapped with an error of around 0.1 m during the time series. Most pixels representing change in the HS derived from the UAS data were consistent with the TLS data. The time series used in this study allowed for testing of the significance of the data acquisition interval in the monitoring of snow ablation. Accordingly, this study concluded that both the UAS- and TLS-based high-resolution DSMs were biased in detecting change in HS, particularly for short time spans, such as a few days, where only a few centimeters in HS change occur. On the other hand, UAS proved to be a valuable tool for monitoring snow ablation if longer time intervals are chosen.

scholarly journals A phase demodulation method for two-dimensional grating-based X-ray interferometry

2014 ◽  
Vol 372 (2010) ◽  
pp. 20130034 ◽  
Author(s):  
Kentaro Nagai
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Control Process ◽  
Two Dimensional ◽  
X Ray ◽  
Phase Stepping ◽  
Novel Approach ◽  
Spectral Components ◽  
Demodulation Method ◽  
Exposure Process

This paper presents a novel approach to achieving high spatial resolution in the demodulation of images produced by a two-dimensional X-ray Talbot interferometry (XTI) system. Currently, demodulation of XTI images is mainly performed by either phase-stepping (PS) or Fourier transform (FT) methods. However, the PS method for two-dimensional XTI demodulation requires a larger number of exposures and a more complex grating control process than that of one-dimensional XTI. On the other hand, although the FT method uses only a single-fringe image, it gives lower spatial resolution than the PS method. For practical application of two-dimensional XTI, a simpler exposure process with high spatial resolution is required. In this paper, we introduce a hybrid method combining the PS and FT methods. This method simplifies the exposure process in comparison with the PS method required in two-dimensional XTI while achieving higher spatial resolution than the FT method in the demodulation of images. The method works by using additional exposures to eliminate unnecessary spectral components that appear in the FT method. Furthermore, the proposed method is demonstrated by using actual two-dimensional XTI data and shown to achieve high spatial resolution in the demodulation of images for both the x - and y -differential phase components.

Sign in / Sign up

Export Citation Format

Share Document