Efficient optical duobinary transmission for high-speed next generation passive optical networks

In TDM PONs the reduced signal to noise ratio and chromatic dispersion tolerance makes it challenging to increase the serialized bitrates beyond 10 Gb/s in a cost effective and within in a needed optical power budget. To combat these challenges, we investigated a 25 Gb/s TDM PON, with reduced drive voltage using Duobinary modulation in the downstream link without compensation. The study improved the conventional ODB modulation scheme to enhance the receiver sensitivity in NG-PON2 downstream link. A 25 km fiber transmission reach, 1:512 power split for a BER of 10 –9 for − 26.6 dBm received power at a bit rate of 25 Gb/s per wavelength was achieved in this study without compensation. The proposed scheme shows better performance in terms of receiver sensitivity with reduced power budget while keeping the system complexity low enough to be justified as an implementation option for PON. The enhanced performance was achieved by controlling the duobinary zero-bit ripple through drive voltage reduction and the amplitude jitters per bit by increasing the duobinary generating LPF without requiring any dispersion compensation module. The simulation results show the suitability of the proposed system to be used as an upgrade option for NG-PON2 with bit rates of 25 Gb/s on a single wavelength.