Crosstalk in a two-channel coherent fiber optic ASK system using an optical amplifier and non-negligible linewidth lasers.

We present BER measurements and crosstalk penalties in a two- channel ASK system using 1.55microns DFB lasers and a semiconductor laser amplifier. The amplifier was operated at P sub (in) = (-30) dBm, well below the gain saturation of P sub (sat) = (-15) dBm. No additional receiver sensitivity penalty due to the amplifier was observed for single channel operation. However, in a two-channel experiment with P sub (in) = (-33) dBm for each channel, the additional crosstalk in the amplifier necessitates a 10% increase of the channel spacing compared to the spacing in the non-amplifier system.