Multi-Carrier 5G-Compliant DML-Based Transmission Enhanced by Bit and Power Loading

The introduction of 5G enhanced mobile broadband (eMBB) services has brought unprecedented bit-rate demands to the optical transport infrastructure, which can hardly be supported through cost-effective digital fronthauling solutions. This opens up a whole new opportunity for bandwidth-efficient radio-over-fiber (RoF) analog fronthaul transmission, which avoids the well-known bandwidth multiplication issue associated with the digitization of radio signals. Using a low-cost directly-modulated laser (DML) with less than 3 GHz bandwidth and a standard PIN photodetector, we demonstrate the transmission of a carrier-aggregated 5G downlink signal over up to 25 km of single-mode fiber (SMF). Resorting to the use of intermediate-frequency-over-fiber (IFoF), we enable the transmission of 5G-compatible signals composed of up to 12 aggregated 400 MHz component carriers (CCs), resulting in a total radio bandwidth of 4.8 GHz, corresponding to >300 Gbps CPRI-equivalent downlink data-rate. 5G-compliant EVM performance across all CCs is achieved through the optimization of power and bit loading between component carriers, enabling an aggregated end user data-rate of 15.6 Gbps.