Quadrature amplitude modulation (QAM) is an excellent modulation format for realizing optical communication systems with a high spectral efficiency aiming at 10bit/s/Hz. We describe a three-channel frequency division multiplexed (FDM) and polarizationmultiplexed 1 Gsymbol/s, 64 QAM coherent transmission over a 160 km SMF with a 1.4 GHz spacing. The total capacity for each channel reaches 36Gbit/s in an optical bandwidth of 4.2 GHz, resulting in a spectral efficiency of 8.6bit/s/Hz.
- Coherent transmission
- Frequency division multi-plexing
- Frequency-stabilized laser
- Polarization multiplexing