Photon Ranging for Upstream ONU Activation Signaling in TWDM-PON

This paper focuses on upstream signaling in TWDM-PON (one of the two systems specified in the new series of ITU-T G.989.x Recommendations for NG-PON2) for what concerns the discovery phase of a new ONU. The key idea is that a new ONU, that needs to be discovered by the OLT, would send a low bit rate signal that is set to a sufficiently low power level to not affect significantly the upstream transmission performance of already active ONUs. We properly dimension the key physical layer parameters of this technique and demonstrate it experimentally. We named this proposal as “photon ranging” due to its ultra-low power transmission and we experimentally demonstrate its feasibility. As a “side effect” of our present work, we had to deeply revise the power penalty generated by the optical interferometric crosstalk, the main impairment that impacts the proposed setup, obtaining new results that may be of interest also in areas not directly related to the specific framework of TWDM-PON.