In order to further improve the performance of orthogonal frequency division multiplexing （OFDM） in dense wavelength division multiplexing（DWDM） fiber optic communication systems, a multi-dimensional trellis coding modulation（TCM） constellation shaping phase conjugate twin waves （PCTW） scheme based on hexadecimal amplitude phase shift keying（16AP-SK） is proposed, and a multi-dimensional Huffman probability shaping（PS） method based on OFDM subcarriers is designed. By using Matlab and OptiSystem to build a simulation platform, the system performance before and after implementing constellation shaping is compared and analyzed. The simulation experiment results show that compared with the system without any constellation shaping technology, the introduction of multidimensional Huffman PS and geometric shaping strategy reduces the spectral efficiency of the system by 0.04, but significantly reduces the symbol error rate by 10.7 dB.