Coherent Nyquist UDWDM-PON with 2.5 Gb/s/user and 15 dB differential link-loss

Coherent ultra-dense wavelength division multiplexing (UDWDM) architecture constitutes an approach to serve hundreds of users in a passive optical network (PON) with high spectrum efficiency. We propose and experimentally test a directly phase modulated distributed feedback (DFB) laser with a Nyquist shaped beat signal. An Rx sensitivity of -44 dBm at BER=10e-3 is achieved for dedicated 2.5 Gb/s/user in only 6.25 GHz spaced. Even more, the proposed technique tolerates a differential link-loss of 15 dB.