As one of the candidate solutions for 5G optical backhaul, Orthogonal Frequency Division Multiplexing Passive Optical Network (OFDM-PON) is expected to support not only the regular services but also the futuristic applications, e. g., haptic communication. However, OFDM-PON has not yet been standardized, particularly Dynamic Bandwidth Allocation (DBA) protocol remains as an open issue in OFDM-PON. In this paper, we focus on the design of DBA protocol for OFDM-PON supporting multi-service. A DBA mechanism is proposed under the MAC framework of the widespread Ethernet PON, such that OFDM-PON can be compatible with the existing PON. A DBA algorithm is further proposed to guarantee the ultra-low latency of haptic communication and achieve the fair transmission of regular services. Performance results show that the proposed mechanism is effective in guaranteeing the round-trip latency of haptic communication with less impact on the regular services.