4/spl times/2.5 Gb/s 4.4 km WDM free-space optical link at 1550 nm

We describe a new world's record for free-space optical communications realized with a 4-channel, 2.5 Gb/s per channel system, operating error-free over a free-space horizontal distance of 4.4 km. This is made possible by three key developments: (1) specialized optical telescope-transceiver terminals, (2) multimode fiber DWDMs and (3) high power 1550 nm Er/Yb optical amplifiers.