Simple and effective solutions for low-cost coherent WDM-PON

This paper presents the most significant results achieved in the last two years by our group in coherent ultra-dense-WDM PON for λ-to-the-user access. Here we mostly focus on the architectures based on simple OOK-NRZ modulation format. We demonstrated the real-time implementation of our coherent receiver and we proved its compatibility with direct modulated laser (DML). Receiver sensitivities as low as -48 dBm at BER=1·10-3 for 1.25 Gb/s has been observed, showing the feasibility of a coherent ONU receiver based on devices commonly available and with limited cost. The system support quite high ODN losses and allows the λ-to-the-user approach.