The coherent ultra-dense wavelength division multiplexed passive optical network (UDWDM-PON) has been widely studied recently, in which the envelop detection based coherent reception of on-off keying (00K) signal has been shown to possess both high receiver sensitivity and tolerance against laser linewidth/chirp. In order to increase the spectral efficiency (SE) to 2 bit/s/Hz, researchers formulated a hybrid DBPSK/ASK-2 modulation using the silicon Mach-Zehnder modulator (MZM), where both amplitude and phase modulation are employed. The experimental result shows that the proposed DBPSK/ASK-2 m...
