Demonstration of Wavelength-Set Division Multiplexing for a Cost Effective PON with up to 80 Gbit/s Upstream Bandwidth

A periodic wavelength plan allows for a cost-effective WDM solution in PON. Using simple DFB lasers with integrated heaters we demonstrated an 8*10 Gbit/s upstream capacity with 512 ONTs in a hybrid TDM/WDM configuration. 1. Introduction Passive optical networks (PONs) are currently rolled out as GPON with a down stream bandwidth of 2.5 Gbit/s and upstream bandwidth of 1.25 Gbit/s [1]. The first XG-PON1 products are coming into the market offering a down stream of 10 Gbit/s and an upstream bandwidth of 2.5 Gbit/s [2]. 

For EPON based systems a similar evolution to 10G-EPON took place. From 2015 on it is expected that even higher bandwidth will be needed for the optical access systems. FSAN is currently studying such systems under the name NG-PON2, which will provide a bandwidth of at least 40 Gbit/s, a passive reach of more than 20 km and more than 64 ONTs per feeder line. There are several contenders for these NG-PON2 systems. The pure TDM/TDMA solution for bitrates higher than 40 Gbit/s suffers from increased penalties from chromatic and polarisation mode dispersion. 

Pure WDM with a relatively low bitrate of 1 Gbit/s needs complex fully tunable lasers in the OLT and ONTs. Due to the logical point to point architecture of WDM, there will be no aggregation gain in the network and the OLT will get relatively costly and bulky. OFDM [3] offers, in contrast to WDM, the ability to flexibly allocate bandwidth to the users depending on demand just like TDMA, but requires currently very costly electronics and in case of coherent detection also costly optical modules.