1. Copyright © 2002 Terabeam Corporation. All rights reserved. 1 Predicting Availability What is Link Availability? 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 Link availability is the percentage of time over a year that the an FSO link will be operational.

2. Copyright © 2002 Terabeam Corporation. All rights reserved. 2 Difference between the optical power received in clear air versus the minimum power level required for a given error rate. Expressed in terms of “dB” –30dB of margin = 1 part in 1,000 required –50dB of margin = 1 part in 100,000 required Typical error rate 1e-9 (1 in a billion) –1e-12 reduces margin by approximately 1 dB –1e-6 increases margin by approximately 1 dB Predicting Availability Part 1: Clear Air Link Margin

3. Copyright © 2002 Terabeam Corporation. All rights reserved. 3 Predicting Availability Part 2: Weather Attenuation Curves based upon surface visibility Seattle 99.99 attenuation = >212 dB/km Seattle 99.9 attenuation = 98 dB/km Denver 99.9 attenuation = 40 dB/km Phoenix 99.9 attenuation = <5 dB/km

4. Copyright © 2002 Terabeam Corporation. All rights reserved. 4 Predicting Availability The Hard Part – Atmospheric Attenuation Curve The Inputs 1.Visibility information from nearby airport weather stations 100m visibility corresponds to 128 dB/km at 1550nm 400m visibility corresponds to 27 dB/km at 1550nm 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

5. Copyright © 2002 Terabeam Corporation. All rights reserved. 5 Visibility of 1 football field ~ 130 dB/km Predicting Availability Examples of Visibility

6. Copyright © 2002 Terabeam Corporation. All rights reserved. 6 Predicting Availability Airport Surface Visibility Data Visibility measured at 550nm September Best – 3600m Average – 400m Worst – 200m

7. Copyright © 2002 Terabeam Corporation. All rights reserved. 7 Stockholm, Sweden, 1982-97 Predicting Availability Cloud Ceiling Impact

8. Copyright © 2002 Terabeam Corporation. All rights reserved. 8 Predicting Availability Attenuation Vs. Percentage Time Occurrence Three Altitudes in Seattle At 99.8 Availability Surface = 60 dB/km 30 th fl = 85 dB/km 52 nd fl = 105 dB/km A link capable of operating at 50 dB/km Surface = 99.78% 30 th fl = 99.72% 52 nd fl = 99.58%

9. Copyright © 2002 Terabeam Corporation. All rights reserved. 9 Installation Characteristics: 1.1550nm Gigabit Ethernet link (1.25 Gbps) 2.Automatic pointing and tracking 3.5 dB windows at each end 4.400m range 5.10m Altitude Budget: Transmit Power 1000 mW 30 dB Receive Sensitivity (-36 dBm) 36 dB Geometric Loss w/o fog at 0.4 km -2.0 dB Window attenuation (2 x 5.0 dB) -10.0 dB Mispoint Loss-1.0 dB Total Optical System Losses -9.0 dB Total Remainder for Weather44.0 dB Therefore, the maximum allowed weather attenuation is: 44 dB/ 0.40 km = 110 dB/km Predicting Availability Putting It All Together – A Link Budget

10. Copyright © 2002 Terabeam Corporation. All rights reserved. 10 Best Year = 99.995 Average Year = 99.94 Worst Year = 99.66 Final Result: Link Weather Availability Predicting Availability Final Result: Link Weather Availability

11. Copyright © 2002 Terabeam Corporation. All rights reserved. 11 Predicting Availability 99.9% Attenuation Margins Attenuation margin (dB/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

12. Copyright © 2002 Terabeam Corporation. All rights reserved. 12 Predicting Availability Variability w/ Location: Washington, DC Washington National Dulles Relative link footprints 99.7 99.8 99.9 99.7 99.8 99.9

13. Copyright © 2002 Terabeam Corporation. All rights reserved. 13 New York 0m 2000m 4000m 6000m Seattle Denver Dallas Miami Phoenix Predicting Availability Real World 99.9% FSO Ranges

14. Copyright © 2002 Terabeam Corporation. All rights reserved. 14 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 Retina –Wavelengths below 1400 nm (close to visible light) focused onto the retina, so power levels must be lower to ensure safety Maximum Permissible Exposure (MPE) limits established by ANSI Retina Cornea

15. Copyright © 2002 Terabeam Corporation. All rights reserved. 15 Eye Safety Laser Standards Organizations OrganizationJurisdictionWhat they classify CDRH Center for Devices & Radiological Health United States; Part of the FDA Product safety (labeling, installation, etc.) ANSI American National Standards Institute United States; Recognized by OSHA User safety (maximum permissible exposure) IEC International Electrotechnical Commission Much of the world; Generally associated with the CE Mark Product and user safety

16. Copyright © 2002 Terabeam Corporation. All rights reserved. 16 Eye Safety Laser Safety Standards Class One Eye-Safe (all conditions)aidedI1 1 Eye-Safe w/o Optical Aidsunaided --1 1 M Class Two (Visible only 400 to 700 nm) < 0.25 sec (eye aversion)aidedII2 2 < 0.25 sec unaided--2 2 M Class Three “a” or “R” Minor Hazard aidedIIIa (visible only)3a 3 R (5 times Class 1)unaided--3a -- anyIIIb3 b3 B Class Four Eye HazardanyIV44 Viewing Condition Class Three “b” - Eye Hazard Most FSO systems are Class 1 or 1M

17. Copyright © 2002 Terabeam Corporation. All rights reserved. 17 Eye Safety Standards and FSO Use Class 1 systems can be installed in Unrestricted locations Class 1M systems can be installed in Restricted areas Class 3B and above only in Controlled locations

18. Copyright © 2002 Terabeam Corporation. All rights reserved. 18 “Sprinkler head” extensions of fiber Closure of SONET/SDH metro rings Spatial diversity Emergency communications Data outsourcing/mirroring/SANS Wireless backhaul Applications & Network Integration Emerging FSO Uses

19. Copyright © 2002 Terabeam Corporation. All rights reserved. 19 Applications & Network Integration Deployments 1 Single customer access Multi-tenant building Campus connection Diverse lateral Backhaul or ring closure Point-to-point connection 2 3 4 5 6 2 3 4 5 6 5 1 and more… Mobile network extensions Mobile network backhaul Spatial diversity

20. Copyright © 2002 Terabeam Corporation. All rights reserved. 20 Jersey CityManhattan Hudson River Merrill Lynch Office 2.6 km 1.8 km 1.6 km Merrill Lynch urgently needed additional connectivity to three locations. 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 Applications & Network Integration Disaster Recovery – After 9/11

21. Copyright © 2002 Terabeam Corporation. All rights reserved. 21 Applications & Network Integration Hybrid Solutions Automatic protection switching between FSO, Millimeter Wave, and/or terrestrial fiber can approach 99.999% availability FSO RF Copper or Fiber

22. Copyright © 2002 Terabeam Corporation. All rights reserved. 22 Applications & Network Integration Hybrid Solutions: Non-Correlated Failures MMW (60 GHz) FSO (30-400 THz)

23. Copyright © 2002 Terabeam Corporation. All rights reserved. 23 Applications & Network Integration Free-Space & 60 GHz MMW Hybrids FSO60 GHz Radio WeatherWorks well in rainWorks well in fog LicensingUnlicensed InterferenceNo interferenceMinimal interference Range20m – 4 km20m – 1.2 km Mounting Options Indoor, outdoorOutdoor

24. Copyright © 2002 Terabeam Corporation. All rights reserved. 24 The Future of FSO 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

25. Copyright © 2002 Terabeam Corporation. All rights reserved. 25 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?

26. Copyright © 2002 Terabeam Corporation. All rights reserved. 26 Thank You