1.28 Terabit/s (32×40 Gbit/s) WDM transmission over a double-pass free space optical link

1.28 Terabit/s (32×40 Gbit/s) is transmitted over a double pass free space optical link between two buildings (2×210m), transparently connected to optical fibers. Limited penalty on all 40 Gbit/s channels and high stability is obtained.