Myth: Light Travels to and from the Sample in a Fibre-Optic Cable without Problems

NIR news ◽  
2014 ◽  
Vol 25 (6) ◽  
pp. 25-26 ◽  
Author(s):  
Kim H. Esbensen ◽  
Paul Geladi ◽  
Anders Larsen
Keyword(s):  
Fibre Optic ◽  
Fibre Optic Cable

scholarly journals Fibre-Optic Cable Types and Installations

Photonics ◽  
2017 ◽  
pp. 513-528
Author(s):  
Abdul Al-Azzawi
Keyword(s):  
Fibre Optic ◽  
Fibre Optic Cable

Wave-selective beamforming with Distributed Acoustic Sensing

2021 ◽  
Author(s):  
Daniel C. Bowden ◽  
Sara Klaasen ◽  
Eileen Martin ◽  
Patrick Paitz ◽  
Andreas Fichtner
Keyword(s):  
Real Data ◽  
Primary Sources ◽  
Seismic Sources ◽  
Fibre Optic ◽  
Wave Type ◽  
Matched Field Processing ◽  
Fibre Optic Cable ◽  
Secondary Scattering ◽  
Distributed Acoustic Sensing ◽  
Beamforming Algorithm

<p>As fibre-optic DAS deployments become more common, researchers are turning to tried-and-true methods of locating or characterizing seismic sources such as beamforming. However, the strain measurement from DAS intrinsically carries its own sensitivities to both wave type and polarization (Martin et al. 2018, Paitz 2020 doctoral thesis). Additionally, a measurement along a conventional fibre-optic cable only provides one component of motion, and so certain azimuths may be blind to certain types of seismic sources, unless the cable layout can be designed to be oriented in multiple directions.</p><p>In this work, we explore the development and application of a beamforming algorithm that explicitly searches for multiple wavetypes. This builds on 3-component beamforming or Matched Field Processing (MFP) algorithms by Riahi et al. (2013), and Gal et al. (2018), where in addition to gridsearching over possible source azimuths, a distinct gridsearch is performed for each possible wavetype of interest. This does not solve the problem that a given cable orientation might be less sensitive to certain directions, but at least an array-response function can be robustly defined for each type of seismic excitation. This might help further distinguish whether beamforming observations are dominated by primary sources or by secondary scattering (van der Ende and Ampuero, 2020 preprint).</p><p>Much of this work uses analytic theory and synthetic examples. Time permitting, the enhanced algorithm will also be applied to data from the Mt. Meager experiment to explore its feasibility and efficacy with real data (EGU contribution from Klaasen et. al, 2021).</p>

Fibre-optic cable for CO and CO2 laser power transmission

1985 ◽  
Vol 17 (4) ◽  
pp. 213-214 ◽  
Author(s):  
V.S. Alejnikov ◽  
V.G. Artjushenko ◽  
V.P. Belyaev ◽  
V.V. Vojtsekhovsky ◽  
E.M. Dianov ◽  
...  
Keyword(s):  
Co2 Laser ◽  
Laser Power ◽  
Power Transmission ◽  
Fibre Optic ◽  
Fibre Optic Cable

Danish earthquake recorded by distributed acoustic sensing (DAS)

2020 ◽  
Author(s):  
Camilla Rasmussen ◽  
Peter H. Voss ◽  
Trine Dahl-Jensen
Keyword(s):  
Field Test ◽  
Signal To Noise Ratio ◽  
Field Tests ◽  
Small Subset ◽  
Fibre Optic ◽  
Data Set ◽  
Acoustic Sensing ◽  
Arrival Times ◽  
Fibre Optic Cable ◽  
Distributed Acoustic Sensing

<p>On September 16th 2018 a Danish earthquake of local magnitude 3.7 was recorded by distributed acoustic sensing (DAS) in a ~23 km long fibre-optic cable. The data are used to study how well DAS can be used as a supplement to conventional seismological data in earthquake localisation. One of the goals in this study is extracting a small subset of traces with clear P and S phases to use in an earthquake localisation, from the 11144 traces the DAS system provide. The timing in the DAS data might not be reliable, and therefore differences in arrival times of S and P are used instead of the exact arrival times. <br>The DAS data set is generally noisy and with a low signal-to-noise ratio (SNR). It is examined whether stacking can be used to improve SNR. The SNR varies a lot along the fibre-optic cable, and at some distances, it is so small that the traces are useless. Stacking methods for improving SNR are presented.</p><p>A field test at two location sites of the fibre-optic cable was conducted with the purpose of comparing DAS data with seismometer data. At the field sites, hammer shots were recorded by a small array of three STS-2 sensors located in a line parallel to the fibre-optic cable. The recordings generally show good consistency between the two data sets. <br>In addition, the field tests are used to get a better understanding of the noise sources in the DAS recording of the earthquake. There are many sources of noise in the data set. The most prominent are a line of windmills that cross the fibre-optic cable and people walking in the building where the detector is located. Also, the coupling between the fibre-optic cable and the ground varies along the cable length due to varying soil type and wrapping around the fibre-optic cable, which is also evident in field test data. Furthermore, the data from the field tests are used to calibrate the location of the fibre-optic cable, which is necessary for using the DAS data in an earthquake localisation. <br>Data processing is done in Matlab and SEISAN.</p>

Design and Development of Redeployable Underwater Data Communication Link for Defence Application

2017 ◽  
Vol 68 (1) ◽  
pp. 111
Author(s):  
Arun Kumar ◽  
L. Anjaneyulu
Keyword(s):  
High Speed ◽  
Data Communication ◽  
Video Camera ◽  
Physical Parameters ◽  
Communication Link ◽  
Fibre Optic ◽  
Time Data ◽  
Design And Development ◽  
Design Data ◽  
Fibre Optic Cable

<p class="p1">Testing of underwater system for defence application is carried out from submersible platform at specified depth. The underwater platform houses the article under test, equipment and instruments required to conduct the test and to control the platform. During development phase of defence systems, large numbers of sensors are mounted on the test article and data is collected to validate the design. Data acquisition system, video camera and high speed video cameras are positioned on the platform to record physical parameters and observe visually the performance of the article under evaluation. Since the data and video signals are parallely recorded on ship, the bandwidth demand for real-time data communication from underwater platform to control station is very high. The existing technology presently used for underwater communication has limitation of bandwidth and not suitable for defence application. This paper describes in detail the design and development of a re-deployable data communication link by laying a specially designed negatively buoyant fibre optic cable in high-sea from ship to underwater platform to provide higher bandwidth required for defence application. The link has been successfully used for sea state less than one during evaluation of underwater defence system. The availability of bandwidth from underwater platform to control system can be increased significantly by laying fibre optic cable in high sea. It also provides unlimited bandwidth for the above requirement.<span class="Apple-converted-space"> </span></p>

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