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  • 1. Atmospheric Effects on Terrestrial Free-space Optical(FSO) Links Presented By Smith Michal Supervised By Prof. Dr. Tom Hason
  • 2. Presentation Outline  Introduction  Objective  Literature Review  Problem Statement  Simulation Results  Conclusion  Future Work  References
  • 3. Introduction  Free-space optical Wireless communication also refereed to as FSO is a growing technology in todays market place.  The information transmitted by optical means at the end of 18th century after the appearance of optical telegraph.  FSO has the great potential to solve problems for bridging the last mile access network gap and provide broadband internet access to rural areas .  The carrier frequencies is in range of 20 THz- 375 THz which allows very high data rates by optical links.
  • 4. Introduction (Cont....)  Currently, It can allow upto 2.5 Gbps in the range of 20 THz to 375 THz of data rate but can be increased to 10 Gbps using WDM  FSO is based on connectivity between two stations consisting of optical transceiver to achieve full duplex communication  It involves two FSO units (similar to BTS of wireless technology) each consisting of high power laser transmitters and receivers, a telescope is used in conjunction to guide the light and capture it at the receiving end. It is then typically interface with network switches, hub, bridge or router via multimode fiber .
  • 5. Introduction (Cont.…)  FSO enables similar bandwidth transmission abilities as fiber optics, using similar optical transmitters and receivers  License free communication , Easy Installation, Avoiding Electromagnetic Pollution and wire trapping safety are advantages of FSO.  FSO, especially through the window, no permits, no digging, no fees of spectrum, no tenching e.t.c
  • 6. How FSO Works 1 Network traffic converted into pulses of invisible light representing 1’s and 0’s 2 Transmitter projects the carefully aimed light pulses into the air 3 A receiver at the other end of the link collects the light using lenses and/or mirrors 4 Received signal converted into fiber or copper and connected to the network Anything that can be done in fiber can be done with FSO
  • 7. Objective  Considering the capabilities of Free Space Optical Communication, briefly discussed in previous slides, it is obvious that one of the major challenges in optical communication to Enhance the performance of Free space optical Communication.  The main theme of this work is to see the challenges of atmospheric effects that are observed during free space optical communication.  In this work we have emphasize the effects of Fog on Free space optical Communication.
  • 8. Review of Literature  Free Space Optics (FSO) or optical wireless systems provide high data rate solution for bandwidth hungry communication applications. Carrier class availability is a necessity for wide scale acceptability which is extremely difficult to achieve in the case of optical wireless links. FSO links are highly  weather-dependent and different weather effects reduce the link availability.  Line of sight optical wireless high-bandwidth transmission links have tremendous potential to serve for the future huge data transmission requirements.  Inherent high carrier frequency (in 20 THz - 375 THz range) enables FSO to provide communication with highest data rates. License free communication, easy installation, avoiding electromagnetic pollution and wiretapping safety are few other advantages. [7] E. Leitgeb & al.: "Weather effects on hybrid FSO/RF communication link,⋯" IEEE J. Select. Areas in Comm. VOL. 27, NO. 9, pp. 1687-1697, December 2009
  • 9. Problem Statement  Fog presents the biggest challenge to propagation of optical signals in free space causing severe attenuations reaching up to several hundred of dB/km..  To Predict the effects of fog attenuation on FSO link we have simulate the KIM, Kruse and Al-Naboulsi models. .  The Simulations are done at different wavelengths i.e 550 nm and 1550nm.  The choice for taking simulations at 550 nm is due to the reason that most of the setups for measurements uses this wavelength [9 ].  The 1550 nm is selected for simulation due to its importance in future application for communication and for eye safety concerns.
  • 10. Kim and Kruse Model(Cont.…)  In order to predict the fog attenuation due to visibility the specific attenuation coefficient for Kim and Kruse model is given by: 𝛼𝑓𝑜𝑔 = ( 10𝑙𝑜𝑔𝑉% 𝑉(𝑘𝑚) ) (𝜆/𝜆𝑜) − 𝑞 • Where V(km) stands for visibility in kilometers , V% stands for transmission of air drops to percentage of clear sky, λ in nm stands for wavelength and λ0 as visibility reference (550 nm) and q is the parameter related to size distribution of the droplet.
  • 11. Kim and Kruse Model(Cont.…) 
  • 12. Al Naboulsi Model (Cont.…) 
  • 13. Al Naboulsi Model(Cont.…) 
  • 14. Simulations and results  The kim, kruse and Al Naboulsi models for the fog attenuation based on visibility range estimation are simulated.  For FSO link we have simulate fog attenuations values predicated by kim, Kruse and Al Naboulsi models which are simulated at different wavelengths that are 550 nm and 1550 nm [13] .  The choice for taking simulations at 550 nm is due to the reason that most of the setups for measurements uses this wavelength [9 ].  The 1550 nm is selected for simulation due to its importance in future application for communication and for eye safety concerns.
  • 15. Simulations (Cont.…)  All the simulations have been made in MATLAB 7.8.0 (R2009a  The simulation
  • 16. Simulation Results for Kim model  The simulation results for Kim model at wavelength(visibility range reference)55o nm and visibility range of 20okm for different values of q are as: 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 visibility in meters SpecificattanuationindB/Km Figure IV-1: Simulation For Kim Model at q=1.6 if V> 50 Km
  • 17. Simulation Results (Cont.…) 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 visibility in meters SpecificattanuationindB/Km Figure IV-2: Simulation For Kim Model at q=1.3 if 6km < V< 50 Km
  • 18. Simulation Results (Cont.…) 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 visibility in meters SpecificattanuationindB/Km Figure IV-3: Simulation For Kim Model at q=0.16 V + 1.34 if 1km < V< 6 Km
  • 19. Simulation Results (Cont.…)  Figure IV-4: Simulation For Kim Model at For q= V - 0.5 if 0.5km < V< 1 Km 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 visibility in meters SpecificattanuationindB/Km
  • 20. Simulation Results (Cont.…)  Figure IV-5: Simulation For Kim Model at q= 0 if V< 0.5 Km 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 visibility in meters SpecificattanuationindB/Km
  • 21. Simulation Results (Cont.…)  Figure IV-6: Comparison of kim model at different values of q for Wavelength 550nm 0 20 40 60 80 100 120 140 160 180 200 0 0.5 1 1.5 2 2.5 3 3.5 4 visibility in meters SpecificattanuationindB/Km
  • 22. Simulation Results (Cont.…)  The simulation results for Kim model at wavelength(visibility range reference)155o nm and visibility range of 20okm for different values of q are as: 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 18 20 visibility in meters SpecificattanuationindB/Km FigureIV-7:SimulationForKimModelatq=1.6ifV>50Kmat1550nm
  • 23. Simulation Results (Cont.…)  Figure IV-8: Simulation For Kim Model at For q=1.3 if 6km < V< 50 Km at 1550nm 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 18 20 visibility in meters SpecificattanuationindB/Km
  • 24. Simulation Results (Cont.…)  Figure IV-9: Simulation For Kim Model at q=0.16 V + 1.34 if 1km < V< 6 Km at 1550nm 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 18 20 visibility in meters SpecificattanuationindB/Km
  • 25. Simulation Results (Cont.…)  Figure IV-10: Simulation For Kim Model at q= 0 if V< 0.5 Km at 1550nm 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 18 20 visibility in meters SpecificattanuationindB/Km
  • 26. Simulation Results (Cont.…)  Figure IV-11: Simulation For Kim Model at q= V - 0.5 if 0.5km < V< 1 Km at 1550nm 0 20 40 60 80 100 120 140 160 180 200 0 2 4 6 8 10 12 14 16 18 20 visibility in meters SpecificattanuationindB/Km
  • 27. Simulation Results (Cont.…)  Figure IV-12: Simulation For Kim Model Comparison at 1550nm 0 20 40 60 80 100 120 140 160 180 200 0 5 10 15 20 25 visibility in meters SpecificattanuationindB/Km
  • 28. Simulation Results for Kruse model  The simulation results for Kruse model at wavelength(visibility range reference)155o nm and visibility range of 20okm for different values of q are as: 10 0 10 1 10 2 10 3 0 10 20 30 40 50 60 70 80 90 Visibility in meters SpecificattanuationindB/Km q=1.6 if V>50*1000m
  • 29. Simulation Results (Cont.…) 10 0 10 1 10 2 10 3 0 10 20 30 40 50 60 70 80 90 Visibility in meters SpecificattanuationindB/Km q=1.3 if 6*1000m<V<50*1000m Figure IV-18: Simulation For Kruse Model at q=1.3 if 6km < V< 50 Km at 1550nm
  • 30. Simulation Results (Cont.…) 10 0 10 1 10 2 10 3 0 10 20 30 40 50 60 70 80 90 Visibility in meters SpecificattanuationindB/Km q=0.585V1 /3 if V<6*1000m
  • 31. Simulation Results (Cont.…) Figure IV-20: Simulation For Kruse Model Comparison at 1550nm 10 0 10 1 10 2 10 3 0 10 20 30 40 50 60 70 80 90 Visibility in meters SpecificattanuationindB/Km Comparsion
  • 32. Simulation Results Al-Naboulsi Fog Model(Cont.…) In the figure IV-21 we have taken the wavelength of 1000 nm and 1550 nm visibility range of 10 to 250 meters 0 50 100 150 200 250 0 2 4 6 8 10 12 AlNaboulsi Model at Lambda=1000 & Visibility 10 to 250 meters
  • 33. Conclusion  The major focus of the whole work in this thesis was to confine ourself on the utility of a performance of FSO links at different models.  The results indicate that Kim model is providing better results at 1550nm wavelength for specific attenuation. The main difficulties towards theoretical characterization of the free- space atmospheric channel are  the unavailability of extensive and accurate weather parameters database  the need to identify main influencing parameters of the meteorological effects and study of their impact on the propagation of optical signals in free-space  the unavailability of enough experimental data of optical attenuations
  • 34. Future Work  There are several possible directions of future work.  The Channel modeling of Free Space optical links.  Optimization of FSO links.
  • 35. References  References:  [1] A. K. Majumdar and J. C. Ricklin. Free-Space Laser Communications, Principles and Advantages. Springer Science, LLC, 233 Spring Street, New York, NY 10013, USA, 2008.  [2] A. Sana, H. Erkan, S. Ahmed, and M. A. Ali. Design and performance of hybrid fso/rf architecture for next generation broadband access networks. SPIE Proceed ings, 6390:63900A.1–63900A.8, 2006.  [3] B. Flecker, E. Leitgeb, M. Gebhart, S. Sheikh Muhammad, C. Chlestil, E. Duca, and V. Corrozzo. Measurement of Light Attenuation in Fog and Snow Conditions for Terrestrial FSO Links. 2006.  [4] C. F. Bohren and D. R. Huffman. Absorption and Scattering of Light by Small Particles. Wiley-Interscience, first edition, 1998.  [5] D. Giggenbach, J. Horwath, and M. Knapek. Optical data downlinks from earth observation platforms. SPIE Proceedings, 7199:719903.1–719903.14, 2009.  [6] E. Leitgeb, M. Gebhart, and U. Birnbacher, "Optical networks, last mile access and applications," Journal of Optical and Fiber Communications Research, vol. 2, pp. 56-85, 2005  [7] E. Leitgeb & al.: "Weather effects on hybrid FSO/RF communication link,⋯" IEEE J. Select. Areas in Comm. VOL. 27, NO. 9, pp. 1687-1697, December 2009
  • 36. References (Cont.…)  [8] F. Nadeem & al.: "Comparison of different models for prediction of attenuation from visibility data", International Workshop on Satellite and Space Communications (IWSSC 2009) 10th-11th September 2009, Siena-Tuscany, Italy.  [9] F. Nadeem, V. Kvicera, M. S. Awan, E. Leitgeb, S. Sheikh Muhammad, and G. Kandus. Weather effects on hybrid fso/rf communication link. IEEE JSAC, 27(9):1687–1697, 2009.  [10] H. Hemmati (Edited). Near-Earth Laser Communications. CRC Press, Taylor and Francis Group, 6000 Broken Sound Parkway NW, Suite 300, 2009.  [11] H. C. van de Hulst. Light Scattering by Small Particles. Dover Publications, Leiden Observatory, 1981.  [12] I. I. Kim and E. Korevaar. Availability of free space optics (fso) and hybrid fso/rf systems. SPIE Proceedings, 4530:84–95, 2001.  [13] I. Kim, B. McArthur, and E. Korevaar. Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications. SPIE Proceedings, 4214, 2001.  [14] J. Llorca, A. Desai, E. Baskaran, S. Milner, and C. Davis. Optimizing perfor- mance of hybrid fso/rf networks in realistic dynamic scenarios. SPIE Proceedings,5892:52– 60, 2005.
  • 37. References (Cont.…)  [15] K. W. Fischer, M. R. Witiw, J. A. Baars, and T. R. Oke. Atmospheric laser communication: New challenges for applied meteorology. Bulletin of the American Meteorological Society, 85(5):725–732, May 2004.  [16] L. Castanet. Influence of the Variability of the Propagation Channel on Mobile,Fixed Multimedia and Optical Satellite Communications. Shaker Verlag GmbH., 2008.  [17] M. Achour. Simulating atmospheric free-space optical propagation: Part i, rainfall attenuation. SPIE Proceedings, 4635:192–201, 2002.  [18] M. Al Naboulsi, F. de Fornel, H. Sizun, M. Gebhart, E. Leitgeb, S. Sheikh 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. SPIE Proceedings, Optical Engineering, 47(3):036001.1–036001.14, 2008.  [19] M. Al Naboulsi, H. Sizun, F. de Fornel, M. Gebhart, and E. Leitgeb. Availability prediction for free space optical communication systems from local climate visibilitydata. COST 270 Short Term Scientific Mission Report, pages 1–30, 2004.  [20] M. S. Awan, R. Nebuloni, C. Capsoni, L. Csurgai-Horvath, S. Sheikh Muhammad, E. Leitgeb, F. Nadeem, and M. S. Khan. Prediction of drop size distribution parameters for optical wireless communications through moderate continental fog. International Journal on Satellite Communications and Networks, 28(05), 2010.  [21] M. S. Awan, E. Leitgeb, S. Sheikh Muhammad, Marzuki, F. Nadeem, M. Saeed Khan, and C. Capsoni. Distribution function for continental and maritime fog environments for optical wireless communication. CSNDSP 2008, 2009.
  • 38. References (Cont.…)  [22] M. Gebhart. Optical Space Communication, Masters Thesis, Department of Space Science, Graz University, 2007.  [23] M. Gebhart, E. Leitgeb, S. Sheikh Muhammad, B. Flecker, C. Chlestil, M. Al  Naboulsi, F. de Fornel, and H. Sizun. Measurement of light attenuation in dense  fog conditions for fso applications. SPIE Proceedings, 5891:58910K.1–58910K.12,  2005.  [24] M. S. Awan, E. Leitgeb, F. Nadeem, and C. Capsoni. A new method of predicting continental fog attenuations for terrestrial optical wireless link. NGMAST 2009.  [25] M. Toyoshima. Trends in satellite communications and the role of optical free-space communications. Journal of Optical Networking, 4 (6):300–311, 2005  [26] M. S. Awan, C. Capsoni, O. Koudelka, E. Leitgeb, F. Nadeem, and M. S. Khan.Diurnal variations based fog attenuations analysis of an optical wireless link. IEEE Photonics Global 2008, 2008.  [27] M. S. Awan, C. Capsoni, O. Koudelka, E. Leitgeb, F. Nadeem, and M. S. Khan.Evaluation of fog attenuations results for optical wireless links in free space. IWSSC 2008, 2008.  [28] M. S. Awan, E. Leitgeb, R. Nebuloni, F. Nadeem, and M. S. Khan. Optical wireless ground- link attenuation statistics of fog and snow conditions. WOCN 2009, 2009.
  • 39. Thanks A lot
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