1. Researchers successfully developed and demonstrated a full-optical free-space optical (FSO) communication system operating at 1550 nm capable of transmitting data at 10 Gbps over 1 km. 2. They also developed an innovative dense wavelength division multiplexing (DWDM) radio-over-FSO (RoFSO) link to transmit multiple radio frequency signals for heterogeneous wireless services. 3. Experiments were conducted to characterize atmospheric effects like turbulence on the FSO system. Measurements of the refractive index structure parameter were obtained and correlated with signal quality metrics.

1. RoFSO: An Enabling Technology for Heterogeneous Broadband Networks Kamugisha KAZAURA 1 ,Edward MUTAFUNGWA 1 , Pham DAT 1 , Alam SHAH 1 , Toshiji SUZUKI 1 , Kazuhiko WAKAMORI 1 , Mitsuji MATSUMOTO 1 , Takeshi HIGASHINO 2 , Katsutoshi TSUKAMOTO 2 and Shozo KOMAKI 2 1 GITS/GITI, Waseda University, Honjo 2 Osaka University, Osaka kazaura@toki.waseda.jp

4. Wireless communication systems 2 Global Suburban Macro-Cell Urban Micro-Cell In-Building Pico-Cell Home-Cell Personal-Cell Wireless systems are not only limited to mobile phone technology!

5. Wireless communication systems 3 UWB Full-optical FSO system 10 Gbps MM wave communication 1 Gbps 100 Mbps 10 Mbps 1 Mbps 100 Kbps 1 km 100 m WiMAX 10 m 10 km 1 m Bluetooth ZigBee WLAN a/b/g Optical fiber communication Communication distance Personal area Communication Optical WLAN IrDA PAN Long distance communication Data rate Visible light communications 100 km FSO communication

9. Evaluation of FSO/RoFSO systems FSO/RoFSO performance Internal parameters (design of FSO/RoFSO system) External parameters (non-system specific parameters) Visibility Atmospheric attenuation Scintillation Deployment distance Pointing loss Optical power Wavelength Transmission bandwidth Divergence angle Optical losses BER Receive lens diameter & FOV RF efficiency Dynamic range SNR Performance related parameters

10. Reduces the optical beam power at the receiver point and causes burst errors Atmospheric turbulence has a significant impact on the quality of the free-space optical beam propagating through the atmosphere. Other effects include: - beam broadening and - angle-of-arrival fluctuations Mitigation techniques include: - Aperture averaging - Diversity techniques - Adaptive optics - Coding techniques Deployment environment characteristics Beam wander Intensity fluctuations (Scintillation ) Time Time Transmit power Received power Combined effect Time Time Time

11. Experiment devices and setup beacon beam output windows fiber connection port primary mirror secondary mirror FPM collimation mirror QAPD/QPD (a) Optical antenna internal structure BERT Power meter Weather data recording PC Scintillation data recording PC Fiber amplifier CCD monitor Remote adjustment & monitor PC Optical clock/data receiver & transmitter (d) Experimental hardware setup Bldg. 55 Waseda University Okubo Campus Bldg. 14 Waseda University Nishi Waseda Campus 1 km (b) Experiment filed RF-FSO Canobeam DT-170 antenna Atmospheric effects measurement antenna (c) Rooftop setup

12. Experimental results 1 Communication system performance evaluation setup Transmission quality performance evaluation 2.5 Gbps transmission 10 Gbps transmission

13. Experimental results 2 C n 2 September 2005 (Summer) Strongest C n 2 (noon): 3.35 • 10 -13 m -2/3 Minimum C n 2 (sunrise): 1.10 • 10 -16 m -2/3 C n 2 January 2006 (Winter) Most C n 2 values less than 1 • 10 -13 m -2/3 Noon maximum value of C n 2 changed by a factor of 2.3 Typical C n 2 values – measured for one month (different seasons) Refractive-index structure constant parameter, C n 2 The most critical parameter along the propagation path in characterizing the effects of atmospheric turbulence

14. Experimental setup for RF signal transmission RF-FSO antenna specification WCDMA signal tx test parameters RF-FSO antenna RF-FSO antenna Bldg. 14 Nishi Waseda Campus Bldg. 55S Okubo Campus 1 km Signal generator (Agilent E4438C) Signal analyzer (Anritsu MS2723B ) Atmospheric turbulence RF-FSO Canobeam DT-170 antenna Atmospheric effects measurement antenna Weather measurement device Bldg. 14 Nishi Waseda campus Bldg. 55S Okubo campus Automatic tracking Tracking method ± 0.5 μrad Beam divergence 100 mm Transceiver aperture 785 nm Operating wavelength Specification Parameter Test Model 1 w/64 DPCH WCDMA test model 30 kHz Resolution bandwidth 120 MHz Center frequency - 5 dBm Input power Specification Parameter

16. Evaluation of RF signal transmission quality 2 WCDMA received signal spectrum ACLR variation during rainfall Clear weather Presence of rainfall

18. Ahsanteni sana kwa kunisikiliza. This work is supported by a grant from the Acknowledgement: Supported by

19. Backup slides

20. Comparisons of RF and FSO based systems Eye safety limits No Possible Health issue Interference No Yes Side lobes Up to –120 dB/km Fog Rain Weather effects LMDS easier with RF - 40 dBm - 60 dBm Threshold Limits range Background Other users Dominant noise No Yes Propagation through obstacles Delays No Yes Subject to regulations Unlimited Limited Max bandwidth Implications IR (FSO) RF Parameter

21. DWDM RoFSO antenna Optical system components showing optical paths Antenna specifications BS1 Si PIN QPD InGaAs PIN QPD FPM BS2 Fiber collimator 5 dB Coupling losses 80 mm Antenna aperture 850 nm Beacon wavelength 1550 nm Communication wavelength Value Parameter Photo of new DWDM RoFSO antenna

22. C n 2 measurement Where: σ I 2 scintillation index (normalized variance of irradiance fluctuations) I optical wave irradiance C n 2 (m -2/3 )index of refraction structure parameter k optical wave number ( k =2π/λ) (785 nm) L (m) propagation path length (1,000 m) Scintillation theory The variance of the log-amplitude fluctuations, σ A 2 can be related to the C n 2 . For horizontal path considering a spherical wave the following relations are applicable in determining C n 2 : Normalized intensity variance

23. Results and analysis 3 Cumulative frequency of occurrence Less than 2% Jan. ‘06 71.88% 28.12% Sept. ’05 1 • 10 -14 < C n 2 < 1 • 10 -13 C n 2 > 1 • 10 -13 Measured C n 2 values (in m -2/3 ) - Midday Month 21:00 ~ 24:00 Night: 11:00 ~ 13:00 Midday: 04:30 ~ 06:30 Sunrise:

24. Results and analysis 4 Cumulative frequency of occurrence Selection based on availability of measured data which could be evaluated collected on days which have no overcast (no clouds or rain) and an average of more than 6 hours of sunlight. Increased occurrence of higher C n 2 values in Sept & Mar as compared to Nov & Jan is due to higher solar radiation 42.48% 4.98% Nov. ‘05 44.83% 2.91% Jan. ‘06 41.67% 14.42% Mar. ‘06 41.06% 16.12% Sept. ’05 6•10 -15 < C n 2 < 6•10 -14 C n 2 > 6•10 -14 Measured C n 2 values (in m -2/3 ) Month