1. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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

2. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Introduction FSO and RoFSO technology FSO system performance consideration Experiment setup and results Summary Contents

3. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Kenya Tanzania Uganda Rwanda Burundi 10,292,000 6,720,072 2,872,000 422,700 347,000 Mobile phone users in EA The telecommunication landscape if dominated by mobile phone users who account for almost 20.7 million users in the region– source the mobile world as of June 2007. Technologies include: GSM, GPRS/EDGE 3 G, WCDMA, Ev-DO (CDMA2000) 3.5 G HSDPA and/or HSUPA ??? 4 G WiMAX ??? Convenient technology for rapid provision of ICT and services to rural communities. Wireless communication systems 1

4. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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! Wireless communication systems 2

5. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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 m10 km1 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

6. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Overview of FSO/RoFSO communications FSO is the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain broadband communications. RoFSO contains optical carriers modulated in an analogue manner by RF sub-carriers. Cosmic radiation T radiation V radiation IR radiation Communications radiation X ray radiation Microwave, radar TV VHF SW Frequency (Hz) 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 250 THz (1 THz) (1 GHz) (1 MHz) (1 pm) (1 nm) (1 μm) (1 mm) (1 m) (100 m) Wavelength (m) 10 -12 10 -9 10 -6 10 -3 10 0 10 2 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 μm 670 780 850 1300 1550 1625 nm Visible light Fiber transmission wavelength range λ = wavelength f = frequency C 0 = 300 000 km/s C = λ x f Visible light Electromagnetic spectrum Merits Secure wireless system not easy to intercept Easy to deploy, avoid huge costs involved in laying cables License free Possible for communication up to several kms Can transmit high data rate De merits High dependence on weather condition (rain, snow, fog, dust particles etc) Can not propagate through obstacles Susceptible to atmospheric effects (atmospheric fluctuations)

7. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 FSO technology application scenarios Mountainous terrain Backhaul (~5 km) FSO transceiver and remote base station Metro network extension Remote located settlements FSO link Optical fiber link RF based links FSO transceiver Areas with no fiber connectivity Internet Space station Inter-satellite link Data relay satellite Ground station with adaptive optics Fiber optic link Demonstration of 2.5 Gbps link High-speed (10Gbs) optical feeder link Terrestrial Metro network extension Last mile access Enterprise connectivity Fiber backup Transmission of heterogeneous wireless services Space Inter-satellite communication (cross link) Satellite to ground data transmission (down link) Deep space communication

8. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Conventional FSO system Operate near the 800nm wavelength band Uses O/E & E/O conversion Data rates up to 2.5 Gbps Bandwidth and power limitations New full-optical FSO system Uses 1550nm wavelength Seamless connection of space and optical fiber. Multi gigabit per second data rates (using optical fiber technology) Compatibility with existing fiber infrastructure Protocol and data rate independent Advanced DWDM RoFSO system Uses 1550nm wavelength Transport multiple RF signals using DWDM FSO channels Realize heterogeneous wireless services e.g. WLAN, Cellular, terrestrial digital TV etc FSO technology Optical fiber O/E E/O module FSO FSO antenna (a) Conventional FSO system Direct coupling of free-space beam to optical fiber WDM FSO Optical fiber FSO antenna (b) New full-optical FSO system Heterogeneous wireless service signals RoF DWDM RoFSO channel Direct connection between RoF and optical free-space RoFSO antenna DVB WiFi WiMAX Cellular (c) Advanced DWDM RoFSO system

9. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Reduces the optical beam power at the receiver point and causes burst errors Beam wander Intensity fluctuations (Scintillation ) Time Transmit power Received power Combined effect Time 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

11. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Experimental results 1 2.5 Gbps transmission 10 Gbps transmission Communication system performance evaluation setup Transmission quality performance evaluation

13. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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 ParameterSpecification Operating wavelength785 nm Transceiver aperture100 mm Beam divergence± 0.5 μrad Tracking methodAutomatic tracking ParameterSpecification Input power- 5 dBm Center frequency120 MHz Resolution bandwidth30 kHz WCDMA test modelTest Model 1 w/64 DPCH Experimental setup for RF signal transmission RF-FSO antenna specification WCDMA signal tx test parameters

15. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Evaluation of RF signal transmission quality 1 Measure and log WCDMA signal quality metrics like ACLR, EVM and PCDE. Correlate performance with weather conditions and atmospheric effects related characteristics like C n 2. This work is ongoing. Example performance related characteristics during rain event 30 th Sept

16. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Evaluation of RF signal transmission quality 2 Clear weatherPresence of rainfall WCDMA received signal spectrum ACLR variation during rainfall

17. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Summary Successfully developed and demonstrated a full- optical FSO communication system operating at 1550 nm capable of offering stable and reliable transmission at 10 Gbps. This technology is suitable for rapid provisioning of broadband access technology in remote and underserved areas. Measured, characterized and quantified the effects of atmospheric turbulence in the deployment environment necessary for design, evaluation and comparison of FSO systems in actual operational settings. Develop a innovative DWDM RoFSO link for heterogeneous wireless services transmission (multiple RF signals)

18. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Ahsanteni sana kwa kunisikiliza. This work is supported by a grant from the Acknowledgement: Supported by

19. KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Backup slides

20. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Comparisons of RF and FSO based systems ParameterRFIR (FSO)Implications Max bandwidthLimitedUnlimited Subject to regulationsYesNoDelays Propagation through obstacles YesNo Dominant noiseOther usersBackgroundLimits range Threshold- 60 dBm- 40 dBmLMDS easier with RF Weather effectsRainFogUp to –120 dB/km Side lobesYesNoInterference Health issuePossibleNoEye safety limits

21. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 DWDM RoFSO antenna BS1 Si PIN QPD InGaAs PIN QPD FPM BS2 Fiber collimator ParameterValue Communication wavelength1550 nm Beacon wavelength850 nm Antenna aperture80 mm Coupling losses5 dB Optical system components showing optical paths Photo of new DWDM RoFSO antenna Antenna specifications

22. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 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. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Results and analysis 3 Month Measured C n 2 values (in m -2/3 ) - Midday C n 2 > 1 10 -13 1 10 -14 < C n 2 < 1 10 -13 Sept. 0528.12%71.88% Jan. 06Less than 2% Sunrise:04:30 ~ 06:30 Midday:11:00 ~ 13:00 Night:21:00 ~ 24:00 Cumulative frequency of occurrence

24. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Results and analysis 4 Month Measured C n 2 values (in m -2/3 ) C n 2 > 610 -14 610 -15 < C n 2 < 610 - 14 Sept. 0516.12%41.06% Nov. 054.98%42.48% Jan. 062.91%44.83% Mar. 0614.42%41.67% 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

25. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Link budget estimation using experimental data and simulation Determining RF-FSO system link budget Required Canobeam OPTRX/CNR for satisfying W-CDMA quality metric Require CNR > 110 for ACLR of 45 dB The link margin can be determined from this. Ongoing work

26. Supported by KRK/OpenAccess2007 - Bagamoyo/14th Nov 2007 Collaborating entities Waseda University Osaka University Hamamatsu Photonics K.K. Olympus Corporation NICT Canon