As the emerging access architecture, NGPONs feature enhanced PON configurations, metro-access integration, and bimodal fiberwireless (FiWi) networks. The moving landscape of NG-PONs provides opportunities for applying novel and promising technologies such as network coding (NC). In this work, we introduce the basic principles of NC and discuss their applicability to NG-PONs, with a focus on layer 2 design. Our example illustrations and simulations demonstrate significant potential performance improvements in various NG-PON scenarios while clarifying some underlying topological constraints of NC.