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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

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Rofso an enabling technology for heterogeneous broadband networks l.jpg

RoFSO: An Enabling Technology for Heterogeneous Broadband Networks

Kamugisha KAZAURA1,Edward MUTAFUNGWA1, Pham DAT1, Alam SHAH1,

Toshiji SUZUKI1, Kazuhiko WAKAMORI1, Mitsuji MATSUMOTO1,Takeshi HIGASHINO2, Katsutoshi TSUKAMOTO2 and Shozo KOMAKI2

1GITS/GITI, Waseda University, Honjo2Osaka University, Osaka

[email protected] 

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Contents Networks

  • Introduction

  • FSO and RoFSO technology

  • FSO system performance consideration

  • Experiment setup and results

  • Summary

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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10,292,000 Networks










Wireless communication systems 1

  • 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:


    • 3 G, WCDMA, Ev-DO (CDMA2000)

    • 3.5 G HSDPA and/or HSUPA ???

    • 4 G WiMAX ???

Mobile phone users in EA

Convenient technology for rapid provision of ICT and services to rural communities.

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Wireless communication systems 2 Networks

Wireless systems are not only limited to mobile phone technology!










KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Wireless communication systems 3 Networks

Data rate

Full-opticalFSO system

Optical fiber communication

FSO communication

10 Gbps

Visible light communications

MM wave communication

1 Gbps

Optical WLAN

Long distance communication


100 Mbps





10 Mbps

Personal areaCommunication


1 Mbps


100 Kbps

1 km

100 km

1 m

10 m

100 m

10 km

Communication distance

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

Overview of fso rofso communications l.jpg

Visible light Networks

Cosmic radiation T radiation V radiation IR radiation Communications radiation

X ray radiation Microwave, radar TV VHF SW

Frequency (Hz) 1020 1018 1016 1014 1012 1010 108 106

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 10-3 100 102

λ = wavelengthf = frequency

C0 = 300 000 km/sC = λ x f

Visible light

Fiber transmissionwavelength range

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

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.


  • 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)

Electromagnetic spectrum

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Data relay satellite Networks

Inter-satellite link

Space station

High-speed (10Gbs) optical feeder link

Demonstration of 2.5 Gbps link

Ground stationwith adaptive optics

Fiber optic link

FSO technology application scenarios


Mountainous terrain

Metro network extension

FSO transceiver andremote base station


  • Metro network extension

  • Last mile access

  • Enterprise connectivity

  • Fiber backup

  • Transmission of heterogeneous wireless services


  • Inter-satellite communication (cross link)

  • Satellite to ground data transmission (down link)

  • Deep space communication

Backhaul(~5 km)

Areas with nofiber connectivity

FSO link

Optical fiber link

RF based links

FSO transceiver

Remote locatedsettlements

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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FSO technology Networks

FSO antenna



Optical fiber


Direct coupling of free-space beam to optical fiber

(a) Conventional FSO system

FSO antenna

Optical fiber


(b) New full-optical FSO system

Direct connection between RoF and optical free-space


RoFSO antenna






Heterogeneous wireless service signals

DWDM RoFSOchannel

(c) Advanced DWDM RoFSO system

  • 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

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Evaluation of FSO/RoFSO systems Networks

Performance related parameters

Optical powerWavelengthTransmission bandwidthDivergence angleOptical lossesBERReceive lens diameter & FOVRF efficiencyDynamic rangeSNR

Internal parameters(design of FSO/RoFSO system)


VisibilityAtmospheric attenuationScintillationDeployment distancePointing loss

External parameters(non-system specific parameters)

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Transmit power Networks

Received power

Beam wander





Intensity fluctuations (Scintillation)

Combined effect


Deployment environment characteristics

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

Reduces the optical beam power at the receiver point and causes burst errors

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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beacon beam Networksoutput windows

primary mirror

Bldg. 14 Waseda University Nishi Waseda Campus

collimation mirror

Weather data recording PC


Optical clock/data receiver & transmitter

Power meter

Fiber amplifier

1 km

(b) Experiment filed

(a) Optical antenna internal structure

secondary mirror


fiber connection port

CCD monitor


Bldg. 55 Waseda University Okubo Campus

Remote adjustment & monitor PC

Scintillation data recording PC

RF-FSO Canobeam DT-170 antenna

Atmospheric effects measurement antenna

(c) Rooftop setup

(d) Experimental hardware setup

Experiment devices and setup

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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2.5 Gbps transmission Networks

10 Gbps transmission

Experimental results 1

Transmission quality performance evaluation

Communication system performance evaluation setup

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Experimental results 2 Networks

Refractive-index structure constant parameter, Cn2

The most critical parameter along the propagation path in characterizing the effects of atmospheric turbulence

Typical Cn2 values – measured for one month (different seasons)

Cn2 September 2005 (Summer)Strongest Cn2(noon): 3.35•10-13 m-2/3Minimum Cn2 (sunrise): 1.10•10-16 m-2/3

Cn2 January 2006 (Winter)Most Cn2 values less than 1•10-13 m-2/3

Noon maximum value of Cn2 changed by a factor of 2.3

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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RF-FSO Networksantenna


Bldg. 14 Nishi Waseda campus

Weather measurement device

Atmospheric turbulence

1 km

Signal generator(Agilent E4438C)

Signal analyzer(Anritsu MS2723B)

Bldg. 14 Nishi Waseda Campus

Bldg. 55S Okubo Campus

RF-FSO Canobeam DT-170 antenna

Atmospheric effects measurement antenna

Bldg. 55S Okubo campus

Experimental setup for RF signal transmission

RF-FSO antenna specification

WCDMA signal tx test parameters

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Evaluation of RF signal transmission quality 1 Networks

  • Measure and log WCDMA signal quality metrics like ACLR, EVM and PCDE.

  • Correlate performance with weather conditions and atmospheric effects related characteristics like Cn2.

  • This work is ongoing.

Example performance related characteristics during rain event 30th Sept

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Clear weather Networks

Presence of rainfall

Evaluation of RF signal transmission quality 2

WCDMA received signal spectrum

ACLR variation during rainfall

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Summary Networks

  • Successfully developed and demonstrateda 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)

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Supported by Networks

Ahsanteni sana kwa kunisikiliza.


This work is supported by a grant from the

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Backup slides Networks

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Comparisons of RF and FSO based systems Networks

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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BS1 Networks



Fiber collimator



Photo of new DWDM RoFSO antenna

DWDM RoFSO antenna

Optical system components showing optical paths

Antenna specifications

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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C Networksn2 measurement

Scintillation theory

The variance of the log-amplitude fluctuations, σA2 can be related to the Cn2.For horizontal path considering a spherical wave the following relations are applicable in determining Cn2:

Where:σI2 scintillation index (normalized variance of irradiance fluctuations)I optical wave irradianceCn2 (m-2/3)index of refraction structure parameterk optical wave number (k=2π/λ) (785 nm)L (m) propagation path length (1,000 m)

Normalized intensity variance

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Results and analysis 3 Networks

Cumulative frequency of occurrence

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Results and analysis 4 Networks

Cumulative frequency of occurrence

Increased occurrence of higher Cn2 values in Sept & Mar as compared to Nov & Jan is due to higher solar radiation

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.

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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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

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007

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Collaborating entities simulation

  • Waseda University

  • Osaka University

  • Hamamatsu Photonics K.K.

  • Olympus Corporation

  • NICT

  • Canon

KRK/OpenAccess2007 - Bagamoyo/14thNov 2007