RESUMEN
Making use of digital filtering, drop RF signal-driven intensity modulation and passive optical coupling, DSP-enabled flexible ROADMs, termed soft-ROADMs, are experimentally demonstrated in real-time, which are free from both optical filters and O-E-O conversions and are inherently transparent to major network design characteristics. In a 4-channel IMDD optical network node incorporating FPGA-based orthogonal digital filter multiplexing, fully real-time soft-ROADM dynamic add and drop operations at both sub-wavelength and spectrally overlapped orthogonal sub-band levels are extensively, experimentally explored, along with their performance robustness against condition variations of practical networks associated with low-cost optical/electrical components. It is shown that the soft-ROADMs introduce optical power penalties as low as 1.4dB for add operation and 2dB for drop operation. For received optical powers fixed at -10dBm, the add operation can tolerate a differential optical input dynamic range of 6.5dB (1.5dB) for sub-wavelength (sub-band) add operation. On the other hand, robust drop operation performances are obtainable over a ~5dB (16°) drop RF signal amplitude (phase) variation range. This work is a significant milestone in demonstrating the technical feasibility of utilising soft-ROADMs to create a programmable networking environment capable of addressing elastic 5G slicing and the SDN paradigm.
RESUMEN
A DSP-based cross-channel interference cancellation (CCIC) technique with initial condition-free, fast convergence and signal modulation format independence, is experimentally demonstrated in a two-channel point-to-point digital filter multiple access (DFMA) PON system based on intensity-modulation and direct-detection (IMDD). The CCIC-induced transmission performance improvements under various system conditions are fully investigated for the first time. It is shown that with one iteration only the CCIC technique can achieve a reduction in individual OFDM subcarrier BERs of more than 1000 times, an increase in transmission capacity by as much as 19 times and an increase in optical power budget by as much as 3.5dB. The CCIC technique thus has the potential to drastically improve the transmission performance of DFMA PONs.