ing at the risks arising from the static keys in an orthogonal frequency division multiplexing passive optical network (OFDM-PON), this study proposes a physical-layer chaotic encryption scheme using channel phase information as dynamic keys. In the coherence time, the initial values of chaotic keys can be extracted from the uplink and downlink channel phases, which are estimated using communication sides. The downlink data is encrypted and decoded by applying XOR operations with the chaotic key stream generated by a one-dimensional chaotic system. The dynamic key obtained using the proposed scheme can be continuously updated with the change of time, further improving the security performance of the physical layer. The experimental results demonstrate that the keys of both communication sides have a good consistency subsequent to the 16-quadrature-amplitude-modulation (16QAM) optical OFDM signal with a speed of 3.625 Gb/s passing through the standard single-mode fiber (SSMF) with a length of 25 km. The key space of the proposed encryption scheme reaches 10 ¹⁵, enhancing the security of system transmission and effectively preventing illegal users from eavesdropping.