Time-division-multiplexed passive optical networks (TDM-PONs) have been successful solutions for providing the huge bandwidth needed for quadruple-play services in last-mile networks. In this paper, the effects of excess bandwidth provisioning applied to a reservation-based TDM are analyzed in detail, and noble adaptive excess timeslot provisioning (ETP) mechanisms are proposed in the interoptical network unit (ONU) and intra-ONU domain in the TDM-PONs. Using traffic load distribution information observed in an optical line termination (OLT), a proposed deficit reservation-based dynamic bandwidth allocation, called dr-DBA, controls the amounts of excess timeslot bandwidths in order to efficiently serve the burst traffic of heavy-loaded ONUs while guaranteeing strict fair link-sharing. The authors also introduce a service work-based ETP bandwidth reservation as well as an optimal reservation class selection mechanism to support prioritized service in an intra-ONU so that serious node light-load penalty and bandwidth overbooking can be minimized. The performance results achieved by numerical analysis and simulations prove that proposed ETP mechanisms provide fair and optimal excess bandwidths to the ONUs according to the changes in traffic load distribution, while compensating the systematic weakness of each mechanism in both ONU domains.