In order to meet the increasing bandwidth requirements, the next generation access network is required to support each wavelength transmission speed exceeding 50 Gb/s, while ensuring the coexistence of traditional network in an economical and efficient manner. Advanced modulation and detection technologies based on digital signal processing is a powerful support to achieve this goal, which can provide good support for large-scale, multi-scene and multi-service access. The principle and main characteristics of several new multi-carrier modulation technologies are discussed in this paper, and their research status and existing problems in passive optical network（PON） are reviewed. What’s more, the suggestions on research direction based on the appeal of the next generation PON are put forward.