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Atmospheric Effects on Terrestrial Free-space
Optical(FSO) Links
Presented By
Smith Michal
Supervised By
Prof. Dr. Tom Hason

Presentation Outline
 Introduction
 Objective
 Literature Review
 Problem Statement
 Simulation Results
 Conclusion
 Future Work
 References

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.

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 .

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

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

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.

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

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.

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.

Kim and Kruse Model(Cont.…)


Al Naboulsi Model (Cont.…)


Al Naboulsi Model(Cont.…)


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.

Simulations (Cont.…)
 All the simulations have been made in MATLAB 7.8.0 (R2009a
 The simulation

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

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
Figure IV-2: Simulation For Kim Model at q=1.3 if 6km < V< 50 Km

0 20 40 60 80 100 120 140 160 180 200
0
0.5
1
1.5
2
2.5
3
3.5
Figure IV-3: Simulation For Kim Model at q=0.16 V + 1.34 if 1km < V< 6 Km

 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

 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

 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

 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
FigureIV-7:SimulationForKimModelatq=1.6ifV>50Kmat1550nm

 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

 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

 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

 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

 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

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
q=1.6 if V>50*1000m

10
0
10
1
10
2
10
3
0
10
20
30
40
50
60
70
80
90
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

10
0
10
1
10
2
10
3
0
10
20
30
40
50
60
70
80
90
q=0.585V1
/3 if V<6*1000m

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
Comparsion

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

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

Future Work
 There are several possible directions of future work.
 The Channel modeling of Free Space optical links.
 Optimization of FSO links.

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

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 performance of
hybrid fso/rf networks in realistic dynamic scenarios. SPIE Proceedings,5892:52–
60, 2005.

 [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.

 [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.

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