Predicting Availability What is Link Availability Link availability
Predicting Availability What is Link Availability? Link availability is the percentage of time over a year that the an FSO link will be operational. • 5 Nines = 99. 999% = Down 5 min / year • 4 Nines = 99. 99% = Down 53 min / year • 3 Nines = 99. 9% = Down 8. 75 hrs / year • 99. 8% = Down 17. 5 hours per year The Primary Driver of FSO Availability is Weather Copyright © 2002 Terabeam Corporation. All rights reserved. 1
Predicting Availability Part 1: Clear Air Link Margin • Difference between the optical power received in clear air versus the minimum power level required for a given error rate. • Expressed in terms of “d. B” – 30 d. B of margin = 1 part in 1, 000 required – 50 d. B of margin = 1 part in 100, 000 required • Typical error rate 1 e-9 (1 in a billion) – 1 e-12 reduces margin by approximately 1 d. B – 1 e-6 increases margin by approximately 1 d. B Copyright © 2002 Terabeam Corporation. All rights reserved. 2
Predicting Availability Part 2: Weather Attenuation • Curves based upon surface visibility • Seattle 99. 99 attenuation = >212 d. B/km • Seattle 99. 9 attenuation = 98 d. B/km • Denver 99. 9 attenuation = 40 d. B/km • Phoenix 99. 9 attenuation = <5 d. B/km Copyright © 2002 Terabeam Corporation. All rights reserved. 3
Predicting Availability The Hard Part – Atmospheric Attenuation Curve The Inputs 1. Visibility information from nearby airport weather stations • 100 m visibility corresponds to 128 d. B/km at 1550 nm • 400 m visibility corresponds to 27 d. B/km at 1550 nm 2. Cloud ceiling information 3. Geographic location of airport vs. installation location 4. Urban heat island effects The Output • A four dimensional atmospheric model – Latitude – Longitude – Altitude – Time Visibility Sensor Copyright © 2002 Terabeam Corporation. All rights reserved. 4
Predicting Availability Examples of Visibility of 1 football field ~ 130 d. B/km Copyright © 2002 Terabeam Corporation. All rights reserved. 5
Predicting Availability Airport Surface Visibility Data September • Best – 3600 m • Average – 400 m • Worst – 200 m Copyright © 2002 Terabeam Corporation. All rights reserved. • Visibility measured at 550 nm 6
Predicting Availability Cloud Ceiling Impact Stockholm, Sweden, 1982 -97 Copyright © 2002 Terabeam Corporation. All rights reserved. 7
Predicting Availability Attenuation Vs. Percentage Time Occurrence Three Altitudes in Seattle At 99. 8 Availability • Surface = 60 d. B/km • 30 th fl = 85 d. B/km • 52 nd fl = 105 d. B/km A link capable of operating at 50 d. B/km • Surface = 99. 78% • 30 th fl = 99. 72% • 52 nd fl = 99. 58% Copyright © 2002 Terabeam Corporation. All rights reserved. 8
Predicting Availability Putting It All Together – A Link Budget Installation Characteristics: 1. 2. 3. 4. 5. 1550 nm Gigabit Ethernet link (1. 25 Gbps) Automatic pointing and tracking 5 d. B windows at each end 400 m range 10 m Altitude Budget: Transmit Power 1000 m. W Receive Sensitivity (-36 d. Bm) Geometric Loss w/o fog at 0. 4 km Window attenuation (2 x 5. 0 d. B) Mispoint Loss Total Optical System Losses Total Remainder for Weather 30 d. B 36 d. B -2. 0 d. B -10. 0 d. B -1. 0 d. B -9. 0 d. B 44. 0 d. B Therefore, the maximum allowed weather attenuation is: 44 d. B/ 0. 40 km = 110 d. B/km Copyright © 2002 Terabeam Corporation. All rights reserved. 9
Predicting Availability Final Result: Link Weather Availability • Best Year = 99. 995 • Average Year = 99. 94 • Worst Year = 99. 66 Copyright © 2002 Terabeam Corporation. All rights reserved. 10
Predicting Availability 99. 9% Attenuation Margins Attenuation margin (d. B/km) required for 99. 9% availability - City by City Notes: Data derived from surface visibility data (altitude effects not included) and Kruse formula Source: Terabeam Weather Group, Jan 2001 Copyright © 2002 Terabeam Corporation. All rights reserved. 11
Predicting Availability Variability w/ Location: Washington, DC 99. 9 99. 8 Dulles 99. 7 Copyright © 2002 Terabeam Corporation. All rights reserved. Washington National 99. 7 Relative link footprints 12
Predicting Availability Real World 99. 9% FSO Ranges 6000 m 4000 m 2000 m Copyright © 2002 Terabeam Corporation. All rights reserved. Phoenix Miami Dallas Denver New York Seattle 0 m 13
Eye Safety The Eye’s Response to Laser Light • Cornea – Wavelengths above 1400 nm almost completely absorbed by the cornea and not transmitted to the retina Cornea • Retina – Wavelengths below 1400 nm (close to visible light) focused onto the retina, so power levels must be lower to ensure safety Retina • Maximum Permissible Exposure (MPE) limits established by ANSI Copyright © 2002 Terabeam Corporation. All rights reserved. 14
Eye Safety Laser Standards Organization CDRH Center for Devices & Radiological Health ANSI American National Standards Institute IEC International Electrotechnical Commission Copyright © 2002 Terabeam Corporation. All rights reserved. Jurisdiction United States; Part of the FDA What they classify Product safety (labeling, installation, etc. ) United States; User safety Recognized by OSHA (maximum permissible exposure) Much of the world; Generally associated with the CE Mark Product and user safety 15
Eye Safety Laser Safety Standards Viewing Condition Class One Eye-Safe (all conditions) Eye-Safe w/o Optical Aids aided I 1 1 unaided -- 1 1 M aided II 2 2 unaided -- 2 2 M aided IIIa (visible only) 3 a 3 R unaided -- 3 a -- any IIIb 3 b 3 B any IV 4 Class Two (Visible only 400 to 700 nm) < 0. 25 sec (eye aversion) < 0. 25 sec Class Three “a” or “R” Minor Hazard (5 times Class 1) Class Three “b” - Eye Hazard Class Four Eye Hazard • Copyright © 2002 Terabeam Corporation. All rights reserved. 4 Most FSO systems are Class 1 or 1 M 16
Eye Safety Standards and FSO Use • Class 1 systems can be installed in Unrestricted locations • Class 1 M systems can be installed in Restricted areas • Class 3 B and above only in Controlled locations Copyright © 2002 Terabeam Corporation. All rights reserved. 17
Applications & Network Integration Emerging FSO Uses • “Sprinkler head” extensions of fiber • Closure of SONET/SDH metro rings • Spatial diversity • Emergency communications • Data outsourcing/mirroring/SANS • Wireless backhaul Copyright © 2002 Terabeam Corporation. All rights reserved. 18
Applications & Network Integration Deployments 2 3 1 5 6 4 1 Single customer access 2 Point-to-point connection 3 Campus connection 4 Diverse lateral 5 Backhaul or ring closure 6 Multi-tenant building 5 and more… • Mobile network extensions • Mobile network backhaul • Spatial diversity Copyright © 2002 Terabeam Corporation. All rights reserved. 19
Applications & Network Integration Disaster Recovery – After 9/11 • Merrill Lynch urgently needed additional connectivity to three locations. Jersey City Copyright © 2002 Terabeam Corporation. All rights reserved. Manhattan Merrill Lynch Office • Terabeam installed Gig-E FSO units to build a ring topology to back up the SONET network • Installation was completed within 7 days of first call Hudson River 2. 6 km 1. 8 km Merrill Lynch Office 1. 6 km Merrill Lynch Office 20
Applications & Network Integration Hybrid Solutions RF FSO Copper or Fiber Automatic protection switching between FSO, Millimeter Wave, and/or terrestrial fiber can approach 99. 999% availability Copyright © 2002 Terabeam Corporation. All rights reserved. 21
Applications & Network Integration Hybrid Solutions: Non-Correlated Failures MMW (60 GHz) FSO (30 -400 THz) Copyright © 2002 Terabeam Corporation. All rights reserved. 22
Applications & Network Integration Free-Space & 60 GHz MMW Hybrids FSO 60 GHz Radio Weather Works well in rain Works well in fog Licensing Unlicensed Interference No interference Minimal interference Range 20 m – 4 km 20 m – 1. 2 km Mounting Options Indoor, outdoor Outdoor Copyright © 2002 Terabeam Corporation. All rights reserved. 23
The Future of FSO Today • The high bandwidth of fiber with the speed and ease of installation of wireless • Unlicensed all over the world due to its inherent resistance to interference • Highly secure and safe • Allows through the window connectivity and single customer service • Fundamentally compliments fiber by accelerating the first and last mile Copyright © 2002 Terabeam Corporation. All rights reserved. 24
The Future of FSO What’s on the Horizon? • All optical – “Fiber through the air” • Lighter, smaller units • “Innocuous” form factors (e. g. , a pane of glass acting as a receive element) • Fundamentally the cheapest way to cross the street at 100 Mbps • Can be used to provision big bandwidth almost everywhere – Where fiber can’t offer an adequate ROI – Where 99. 9 is acceptable – To the home? Copyright © 2002 Terabeam Corporation. All rights reserved. 25
Thank You Copyright © 2002 Terabeam Corporation. All rights reserved. 26
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