Direct Phase Modulation for UDWDM ONU with Beat Signals

An ONU transmitter for UDWDM PONs based on direct phase modulated distributed feedback lasers (DFB) through digital beat signals is proposed and experimentally tested. The amplitude and duty cycle of the modulating signal are optimized for a DPKS signal. We achieved sensitivities of −50.5 dBm, and −45 dBm for bit rates of 2.5 Gb/s, and 5 Gb/s respectively at BER = 4×10
⁻³
with an intradyne coherent receiver.