Direct phase modulation of a DFB laser for udWDM-PON

The response of a DFB was equalized with a simple RC network for modulating directly its phase and producing a BPSK signal. The system was tested with a heterodyne coherent detector at 1.25 Gb/s and 2.5 Gb/s showing a sensitivity penalty of around 1dB when compared with external phase modulation. The results indicate that the technique could be considered as a reliable low-cost ONU transmitter solution in udWDM-PONs.