  Free-space optical communication (FSO) can achieve fast, secure and
license-free communication without need for physical cables, making it a
cost-effective, energy-efficient and flexible solution when the fiber
connection is unavailable. To establish FSO connection on-demand, it is
essential to build portable FSO devices with compact structure and light
weight. Here, we develop a miniaturized FSO system and realize 9.16 Gbps FSO
between two nodes that is 1 km apart, using a commercial
single-mode-fiber-coupled optical transceiver module without optical
amplification. Using our 4-stage acquisition, pointing and tracking (APT)
systems, the tracking error is within 3 {\mu}rad and results an average link
loss of 13.7 dB, which is the key for this high-bandwidth FSO demonstration
without optical amplification. Our FSO link has been tested up to 4 km, with
link loss of 18 dB that is limited by the foggy weather during the test. Longer
FSO distances can be expected with better weather condition and optical
amplification. With single FSO device weight of only 9.5 kg, this result
arouses massive applications of field-deployable high-speed wireless
communication.
