15-dB Differential Link-Loss UDWDM-PON With Direct Beat Phase Modulated DFBs

A 15 dB differential link-loss ultra-dense wavelength division multiplexing passive optical network (UDWDM-PON) with two optical network units (ONU) spectrally spaced 6.25 GHz is experimentally implemented and tested. The ONU transmitters consist of direct phase modulated distributed feedback lasers through a digital beat signal, whose amplitude and duty cycle are optimized for maximum phase variations, avoiding the need for an analogue equalizer. We achieved receiver sensitivities of -53, -50.5, and -45 dBm for bit rates of 1.25, 2.5, and 5 Gb/s, respectively, at BER = 4 · 10
^-3
with an intradyne coherent receiver.