All Optical Fog_MI
Transcript of All Optical Fog_MI
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All-optical Fog Sensor for Determining the FogVisibility Range in Optical Wireless
Communication Links
Muhammad Ijaz, Zabih Ghassemlooy, SeniorMember, IEEE,Hoa Le-Minh, Sujan Rajbhandari,
Member, IEEEOptical Communication Research Group, School of computing, Engineering and
Information Sciences, Northumbria University, UK
Email: [email protected]
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Structure of the Talk
Motivations
Optical Wireless Communication
Why Fog Sensor
Design of the Fog Sensor
Fog Sensor and Visibility
Results
Conclusions
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Motivations
Free space Optical Communication (FSO) Link
Why Fog SensorThe meteorological definition of fogis when the link visibility is less than 1 km.1,2
The visibility is the prime parameter for investigating the affects of fog on outdoor FSOsystems performance and availability.
The visibility data is not available for real sites of the FSO links due to the high implementationcost of transmissometer. In this paper we introduced a laboratory optical fog sensor which hasbeen designed to characterise the link visibility for different fog channel conditions.
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1. H. Willebrand, and B. S. Ghuman, Indianapolis, IN: SAMS publishing, 2002.2. M. S. Awan, L. C-Horvath, S. S. Muhammad, E. Leitgeb, F. Nadeem, and M. S. Khan, J. of Communications, 4(8), pp. 53 -
545, 2009.
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Design of the Fog Sensor
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Figure 1. (a) Optical fog sensor, Distance between LEDand Receiver is 13 cm and (b) atmospheric chamber.The volume of atmospheric chamber is 5.50.30.3 m3.
Sound Card
Photo-DetectorTransmitter
=880nm
Amplification
Sound Card
Amplification
Computer
Figure 2. Block diagram of fog sensor.
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Fog Sensor and Visibility
Meteorological visibility V can be expressed as function of theatmospheric attenuation coefficient yusing the visual threshold Tth byKoschmieder Law:1
The attenuation coefficient can be calculated from the Beer-Lambert
law given by 1-3
I(f)andI(0) are the intensity of the optical signal with and without fog,respectively.
Note that the fog sensor output was normalized to 1 and 0 without fog andwith a dense fog, respectively. So, the value of fog sensor is calibrated between1 and 0 depending on the fog density within the chamber.
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1. A. Prokes, J. of Optical Engineering, 48(6), pp. 066001-10, 20.2. M. S. Awan, L. C-Horvath, S. S. Muhammad, E. Leitgeb, F. Nadeem, and M. S. Khan, J. of Communications, 4(8), pp. 53 - 545, 2009.3. M. A Naboulsi, F. de Fornel, H. Sizun, M. Gebhart, E. Leitgeb, S. S. Muhammad, B. Flecker and C. Chlestil, Proc. of SPIE, Optical
Engineering, 47(3), pp. 036001.1 - 036001.14, 2008.
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Results
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0 5000 10000 150000
1000
2000
3000
4000
5000
6000
Abs.
Magnitu
de
Frequency [Hertz]
Without fog
0 5000 10000 150000
1000
2000
3000
4000
5000
6000
Abs.
Magnitude
Frequency [Hertz]
with Fog
The received signals in frequency domain with and without fog are shown .The absolute magnitude level of the received signal without fog is 5500which is equal to 1 V, whereas with fog, the level is 2900 equal to 0.5304 V.
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Results-cont.
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00.10.20.30.40.50.60.70.80.910.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Transmittance
Visibility(Km)
Light Fog Moderate Fog
The transmittance (T) of the fog sensor versus the visibility in kmfrom light to moderate fog.
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Results-cont.
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0.4 0.5 0.6 0.7 0.820
25
30
35
40
45
Visibility(Km)
Attanuation(dB/Km)
0 0.2 0.4 0.6 0.8 120
25
30
35
40
45
Transmittance(T)
A
ttanuation(dB/Km)
(a) Experimental visibility versus attenuation (dB/km) and (b) transmittance of the optical fog
sensor versus the attenuation coefficient (dB/km).
The attenuation exceeds 45 dB/km as the visibility drops below 400 m, for moderatefog case. This is inline with the attenuation data reported in1,2for the visibility rangeless than 500 m.
(a) (b)
1. I. I. Kim, B. McArthur, and E. Korevaar, Proc. of SPIE, 4214(issue??), pp. 26 - 37, 20012. A. Prokes, J. of Optical Engineering, 48(6), pp. 066001-10, 2009.
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Conclusions
In this paper we have shown the application of an all optical fogsensor in an FSO system for measuring optical attenuation dueto light-to-moderate fog in a laboratory based atmosphericchamber.
Using the Koschmieder law, the fog sensor is used to determinethe visibility (and attenuation) in the range of 0.37 1 km andabove.
Work to develop the fog density measurement tool for allranges of visibility is in progress and the results will bepublished in due course.
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Special Thanks for
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Prof. Z. GhassemlooyDr. Hoa Le-MinhDr. Sujan Rajbhandari
All colleagues in OCRG&
Your Attention
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References
1. P. Mandl, P. Schrotter, and E. Leitgeb, Wireless synchronous broadband last mile access solutions formultimedia applications in license free frequency spectrums, 6th International Symposium onCommunication Systems, Networks and Digital Signal Processing, pp. 110 -113, 2008.
2. A. K. Majumdar, and J. C. Ricklin, Free-Space Laser Communications, Principles and Advantages, SpringerScience, LLC, 233 Spring Street, New York, NY 10013, USA, 2008.
3. O. Bouchet, H. Sizun, C. Boisrobert, F. de Fornel, and P. Favennec, Free-space optics, propagation andcommunication, ISTE, pp.87 - 127, 2006.
4. I. I. Kim, B. McArthur, and E. Korevaar, Comparison of laser beam propagation at 785 nm and 1550 nmin fog and haze for optical wireless communications, Proc. of SPIE, 4214(issue??), pp. 26 - 37, 2001.
5. H. Willebrand, and B. S. Ghuman, Free space optics: enabling optical connectivity in today's Network,Indianapolis, IN: SAMS publishing, 2002.
6. M. S. Awan, L. C-Horvath, S. S. Muhammad, E. Leitgeb, F. Nadeem, and M. S. Khan, Characterization offog and snow attenuations for free-space optical propagation, J. of Communications, 4(8), pp. 53 - 545,2009.
7. M. A Naboulsi, F. de Fornel, H. Sizun, M. Gebhart, E. Leitgeb, S. S. Muhammad, B. Flecker, and C. Chlestil,
Measured and predicted light attenuation in dense coastal upslope fog at 650, 850, and 950 nm for free-space optics applications, Proc. of SPIE, Optical Engineering, 47(3), pp. 036001.1 - 036001.14, 2008.
8. A. Prokes, Atmospheric effects on availability of free space optics systems, J. of Optical Engineering,48(6), pp. 066001-10, 2009.
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