Next Generation Passive Optical Network Stage 2 (NG-PON2) features multiple wavelength channels. Channel bonding combines multiple NG-PON2 wavelength connections in parallel to increase the access network throughput beyond the capacity of a single connection. It enhances the access network peak rate provisioning. Channel bonding is actively studied in the ITU Telecommunication Standardization Sector (ITU-T) as a key enhancement to NG-PON2 recommendations. In this paper, we propose a channel bonding scheme by reusing the ITU-T PON data units of XG-PON encapsulation method (XGEM). The bonding system structure is investigated, and the bonding problem is formulated by using integer linear programming (ILP) formulation. A heuristic algorithm is proposed to control data transmission in the bonded channels. Performance is evaluated via network simulations. Simulation results are further analyzed to provide guidance on packet delay control and algorithm key parameter configuration.