40-Gb/s Upstream Transmitters Using Directly Modulated 1.55-μm VCSEL Array for High-Split-Ratio PONs

We propose and demonstrate a 40-Gb/s symmetric passive optical network with a high split-ratio of 64. The upstream 4 x 10 Gb/s signal is produced by using a directly modulated, uncooled 1.55-μm monolithic integrated vertical-cavity surface-emitting laser array. The downstream signal is a single-channel 40-Gb/s dark-return-to-zero (DRZ) data, broadcasting information to different optical networking units (ONUs). As the ONU is cost-sensitive, we also demonstrate, by means of simulations, using a 12-Gb/s receiver at the ONU to receive the 40-Gb/s DRZ downstream signal.