Free Space Laser Communications

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Free Space Laser Communications

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1. Free Space Laser Communications Phillip Dykstra WareOnEarth Communications Inc. [email protected]

2. Introduction Free space laser communications a.k.a. Free Space Optics, Optical Wireless Basically a laser and a telescope Most are protocol independent Typical range < 4 km (.5, 1, 2, 4, 8km) Typical bandwidths: 10, 100, 1000 Mbps Lucent 10 Gbps DWDM (TeraBeam)

3. Example Systems

4. Transmitters LED (single or multiple) 1 mW typical Laser (single or multiple) 10-20 mW typical, up to 100 mW Usually 785 or 850 nm, some 1310 nm Eye safety limit: 1.5 mW/cm^2 at 785 nm Multiple transmitters boost power, may also reduce scintillation fades

5. Detectors PIN Diodes -43 dBm typical Avalanche Photo Diodes (APD) -53 dBm typical (also greater dynamic range) Single or multiple detectors Larger aperture increases receive power, reduces scintillation fades Design goal: BER < 10^-9 typical

6. Laser Link Geometry Critical Design Parameters

7. System Comparison (OC3 1km products)

8. Example Loss Budget Optical Access T1000X

18. Fog Event (19 June 01)

19. Fog Event (cont)

20. Packet Loss

21. Availability Availability = Prob (Visibility > Vmin)

22. For More Info

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