Demonstration of symmetrical 25 Gbps TDM-PON with multilevel interleaving of users
01 January 2015
A cost effective symmetrical 25 Gbps TDM-PON utilizing a novel multilevel user-interleaving scheme based on PAM-4 in the downstream and 3-level duobinary modulation in the upstream is demonstrated without using any DSP. At the ONU we used a commercial off-the-shelf 10 Gbps EML-based transmitter and a 10 Gbps APD/TIA-based receiver to keep the cost low. It will be shown that 3-level duobinary and PAM-4 modulation are more tolerant to chromatic dispersion (CD) compared to NRZ, therefore it also offers a reach extension. The multilevel user-interleaving scheme enables the use of a half-rate CDR at the ONU as well as the use of a simple NRZ CDR/EDC to improve the optical receiver sensitivity for downstream transmission. We believe that using PAM-4 modulation for the downstream and NRZ to duobinary conversion for the upstream offers a good technical compromise for lowest cost at the ONU for 25 Gbps TDM-PON.