Densely spaced FDM coherent optical star network using monolithic widely frequency-tunable lasers

The authors present the results obtained with a densely spaced FDM coherent optical network using monolithic widely frequency-tunable lasers. The system consists of four channels transmitted around 1.53 mu m, FSK-modulated at 200 Mbit/s and spaced by 2.45 GHz. A 16*16 fibre star coupler combines the four optical signals. Demultiplexing is performed by a heterodyne FM receiver at an IF frequency of 850 MHz. The minimum received optical power needed to obtain a BER of 10/sup -9/ is -55.5 dBm or 109 photons/bit, which is 3.4 dB from the shot noise limit. >