01-03-2010, 03:27 PM
Free Space Laser Communications.ppt (Size: 985 KB / Downloads: 431)
Free Space Laser Communications
Introduction
¢ Free space laser communications
“ a.k.a. Free Space Optics, Optical
Presented By
Phillip Dykstra
WareOnEarth Communications Inc.
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)
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
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