This paper presents key operational elements which impact upon performance characteristics for terrestrial free-space laser communications systems within the 1550 nm window. These elements include; optical transmit and receive functionality of the telescope terminals, electro-optic components as well as atmospheric conditions affecting link performance.

We simultaneously transmit 16 separate 2.5 Gb/s wavelength data channels, with a 200 Ghz channel spacing, error-free, over a horizontal free space distance of 4.4 km. We believe this result represents the largest bandwidth transmitted at one time over such a distance, without the use of optical transmission fiber.

We present new performance results for a multi-gigabit terrestrial free-space laser communications system. The measured laser communication link performance parameters include: link bit-error-rate, received optical power, scintillation characteristics and atmospheric visibility.

Optical amplifiers are an enabling technology for free space laser communications. Transmission of four multiplexed 2.5 Gbps channels at 1550 nm over a 4.4 km terrestrial link is described and modeled.