Introduction To Fso Technology

Wireless Product Division Introduction to FSO Technology By Itshak Kidouchim – Jan 2007

Introduction to FSO – Free Space Optics
FSO Communication is using the LASER light as the carrier.
Full Duplex, Full Speed AND No Delay.
Up to 1 Gbps Ethernet
Distances – up to 5km.
No License is required.
Easy to install and almost no maintenance is required.
I - What is FSO

II - Why Free Space Optics (FSO)? The “Last Mile” Bottleneck Problem Only about 10% of commercial buildings are lit with fiber
Wide Area Networks between major cities are extremely fast
Fiber based
>2.5 Gbps
Local Area Networks in buildings are also fast
>100Mbps
The connections in between are typically a lot slower
0.3-1.5 Mbps

Why Free Space Optics? Why Not Just Bury More Fiber?
Cost
Rights of Way
Permits
Trenching
Time
With FSO, especially through the window, no permits, no digging, no fees

Ground Lasercom Terminal Satellite Lasercom Terminal 1 Gbps 2000 km range Commercial Lasercom Examples of FSO Systems

Worldwide Installations USA Canada Mexico Brazil Argentina Uruguay China Singapore Japan India Philippines Taiwan S. Korea Australia Thailand Vietnam Malaysia Indonesia South Africa Nigeria Slovenia Croatia Latvia Czechoslovakia Gibraltar Luxemburg Netherlands France Norway Greece Germany England Switzerland Sweden Portugal Spain Italy Turkey Israel Saudi Arabia MRV Communications: More than 7000 links installed

Electromagnetic Spectrum Spread spectrum Microwave 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 14 10 15 10 16 Hertz kHz MHz GHz THz 10 7 10 6 10 5 10 4 10 3 10 2 10 1 0.1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 Frequency Wavelength Radio Waves Microwaves Infrared UV Power & Telephone Copper wire transmission km meter cm mm mm 10 -9 nm 10 17 Coaxial cable Fiber optic AM radio FM radio Laser communication Unlicensed III – The Technology Smaller carrier wavelength / Higher Bandwidth

Near Infrared Visible Spectrum 400 nm 500 nm 600 nm 700 nm 800 nm 900 nm HeNe 780 nm 810 nm 850 nm 1550 nm Near Infrared 1300 nm

How does it work? Fiber Optic Cable Laser Transmitter Receiver Network Network Lens Free space

How FSO works? Anything that can be done in fiber can be done with FSO 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 5
Reverse direction data transported the same way.
Full duplex
3 A receiver at the other end of the link collects the light using lenses and/or mirrors 4 Received signal converted back into fiber or copper and connected to the network

IV - Free Space Optics Positioning
High Bandwidth Wireless
Secure Wireless
Short distances
Within Urban areas
Eye safe

Bandwidth - Wireless ?
What is the fiber technology bandwidth limitation ?
Unlimited
What is the radio technology bandwidth limitation ?
Limited (only GHz frequencies)
What is the FSO technology bandwidth limitation ?
Unlimited
FSO ≡ Ultra Bandwidth Wireless Solutions MRV Leading the Gigabit Wireless Revolution

Access Technologies Positioning c 10 Gbps 1 Gbps 100 Mbps 10 Mbps 1 Mbps 200 m 50 m 500 m 1 km 5 km 15 km+ Fiber LMDS WiFi Optical Wireless T-1 DSL Future Performances

Security Wireless ?
Is Radio signal secure ? What is the RF signal spectrum ?
Very wide How many times did you see other Radio network in your area ?  FSO ≡ Most Secure Wireless Solutions Very narrow and directional mrad divergence Range = R = 1000 m = 1 km ~2 m
Is TereScope FSO signal secure ?

Beams only a few meters in diameter at a kilometer
Allows VERY close spacing of links without interference
No side lobes
Highly secure
Efficient use of energy
Ranges of 20m to more than 8km possible
Narrow Beam Advantages

Applications Point-to-Point Ring Secure Ultra Bandwidth Wireless Mesh

V - General Terms Beam Divergence - measure of angle or how much the beam spreads circle: 360° (degrees) = 2π radians 1 radian = 57° (degrees) 1 milliradian = 0.001 rad = 0.057° (degree) 80 µ radians = 0.00008 rad = 0.0046° (degree) (satellite) 2.5 mrad divergence 1 mrad divergence Range = R = 1000 m = 1 km 80 µrad divergence 1 radian Laser Communication System 2.5 m 1 m 8 cm STRV-2 Satellite Laser Communication System

Tx Tx High geometric loss. . . . . .good link stability. Narrow angle Tx . . .poor link stability. Wide angle Link stability – Depending on Beam divergence Tx

Geometric loss Beam Area Receiver Lens Area  d B
= divergence angle, d B =  R
GM (Geometric Loss) = 10 log (Rx lens Area/Beam Area)
= 10 log [d R /(  R )] 2
d R R (air transmission distance) Tx

The Decibel - dB
A logarithmic ratio between two values
In the optical world of Power in mW,
dB=10*Log(power2/power1)
3 dB = ratio of 2/1
6 dB = ratio of 4/1
10 dB = ratio of 10/1
20 dB = ratio of 100/1
50 dB= ratio of 100,000/1
Gain/Loss Multiplier +30 db +20 db +10 db 0 db -10 db -20 db -30 db 1000 100 10 1 .1 .01 .001

System Gain
Transmitter(s) power
Receiver sensitivity
Attenuation
Geometrical attenuation
Atmospheric attenuation
Scattering
Scintillation
Turbulence
System factors
Components and assemblies tolerances
System misalignment
Total available margins = System Gain - Attenuation Link Budget

Environmental factors Sunlight Building Motion Alignment Window Attenuation Fog Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor. Scintillation Range Obstructions Low Clouds Sunlight

Environmental effects – Rain, Scintillation & Haze Type of events

Fade Margin calculation

Effects of the atmosphere on laser beam propagation
Atmospheric attenuation
absorption
scattering
Atmospheric turbulence
laser beam wander
scintillation
VI – Effects of the weather on FSO com.

Scattering Major Factor – Haze, Fog, Smog
Scintillation Moderate Factor - Air shimmering off hot surfaces
Turbulence / Beam Wander Minor Factor – Different density air layers formed locally by temperature differences
Environmental effects – Scattering, Scintillation & Turbulence

Typical Scattering Attenuation Factors for Various Weather Conditions Scattering

Effective Link Range vs. Winter Visibility
For laser transmission, attenuation by fog is much greater than attenuation by rain (opposite for microwaves)
Fog droplet size (5 to 15 µm)  laser wavelength
Rain droplet size (200 to 2000 µm)  microwave wavelength
Effect of snow is between rain and fog
FOG RAIN SNOW

Scintillation & Turbulence Atmospheric turbulence (ie. wind) produce temporary pockets of air with different temperature thus different density thus different index of refraction. These air pockets and are continuously being created and then destroyed as they are mixed. The effect of these cells which lie along the laser beam path depends on the size of the cells. Laser Beam Wander if the cells are larger than the beam diameter Scintillation if the cells are smaller than the beam diameter. The wavefront becomes distorted due to constructive and destructive interference creating fluctuations in receive power, similar to the twinkling of a distant star.

Scintillation & Turbulence Power Time Power Time Laser Beam Wander Transmit power Receive power Power Time Power Time Scintillation Total Effect is the sum of both Power Time

Scintillation caused burst errors Serial bit stream Fluctuating received laser power Minimum receive power threshold Burst error Burst error

Link Bandwidth vs. Link Range @ various Atmospheric attenuation values * * TS5000/G TS5000/155 Ethernet/4E1 E1 Bandwidth 1 km 1.25Gbps 100Mbps 10Mbps 2Mbps 2 km 3 km 4 km 5 km * 30 dB/km 17 dB/km 10 dB/km 3 dB/km @ @ @ * @ For operation under light to medium rain, light snow, light haze. * For operation under medium to heavy rain – snow, thin fog. For operation under cloudburst, medium snow, light fog. For operation under blizzard, moderate fog. @ 6 km

VII - Competitive Technology
Spread Spectrum Disadvantages
Susceptible to RF interference in congested areas
Can be monitored easily
Limited actual bandwidth (throughput of 2-54 Mbps half duplex)
Microwave Disadvantages
Cost (the higher the bandwidth, the greater the cost)
Complex installations
Licensing required for higher frequencies

VIII - MRV TereScope™ Series - Matrix
The Most Comprehensive Free Space Optics Solutions
In The Industry

IX – TS Installation Examples TS5000 Datec

DisneyLand - France TS3303 with Fusion M6- France

Sofdit, 7m pole - France TS707/4E1, Yanisahra - Turkey

Vitrolles – France 10 links

X - TereScope Structure בס " ד A - TS155 BLOCK DIAGRAM 1-155Mbps Interface unit Control Panel Management Unit(optional) Air Link Transmitter Air Link Receiver AC / DC Power Supply Clock / Data Recovery RSM-DC (Option) Data Out Data In Interface

B - 4E1 BLOCK DIAGRAM E1/T1 Line Interface unit E1/T1 Line Interface unit E1/T1 Line Interface unit E1/T1 Line Interface unit 4 E1/T1 Multiplexer / Demultiplexer Device Clock/Data Recovery Control Panel Management Unit(optional) Air Link Transmitter Air Link Receiver AC / DC Power Supply

Advantages of Infrared Wireless links
Very high bandwidth (1.5GBps)
License free
Most secure wireless medium
RFI/EMI immunity
No cross-talk or cross interference
Safe, no health hazards
Easy to relocate links
Low maintenance
Fast deployment
XI - Summary

THANK YOU ww.mrv.com [email_address]

Introduction To Fso Technology

by Armando Cajahuaringa on Jul 14, 2008

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