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In the wake of the gradual maturation of the theory and devices of the space division multiplexing optical transmission systems, the coding modulation of the next-generation space division multiplexing systems have to be updated as well. Compared with classic single-core single-mode fiber transmission systems, space division multiplexing optical transmission systems have multiplied receiver complexity, making code modulation with low receiver complexity desirable. In this paper, we build a seven-core optical fiber transmission system to experimentally verify the performance of differential amplitude phase shift keying (DAPSK) orthogonal frequency division multiplexing (OFDM). Through the joint modulation of DAPSK and OFDM, DAPSK-OFDM modulation does not require redundant data for channel compensation and phase noise compensation compared to quadrature amplitude modulation (QAM)-OFDM. The code division multiplexing modulation is deployed for the data transmitted by different fiber cores to form orthogonalized channel data transmission, which can effectively reduce the crosstalk between the cores. A 2 km short-distance sevencore optical transmission experimental system was successfully carried out to test the signal transmission performance of different fiber cores. Experimental results indicate that the DAPSK-OFDM signal is not sensitive to frequency offset, so it can be free of frequency offset estimation and channel equalization. In terms of transmission performance, the performance of 16-QAM-OFDM is better than that of 16-DAPSK-OFDM.
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