Sparse code division multiple access (SCMA) technology is one of the main technologies of 5G (5th Generation Mobile Communication Technology). Applying SCMA technology to the field of optical communication has broad prospects, which solves the access problem of a large number of users in optical access network. In this paper, a transmission system based on SCMA over multi-core fiber is proposed. The SCMA coding signal transmission at 30 Gb/s is successfully implemented on a seven-core fiber, which four of seven-core is only used. Its bit error rate (BER) can achieve forward error correction (FEC) limit (BER is 3.8 × 10-3) when the received optical power is -10 dBm. And this experiment verifies the performance of the proposed scheme. In addition, we propose a scheme to reduce the complexity of message passing algorithm (MPA) at the receiver by using the core of fiber dimension. Compared with original MPA, this scheme reduces the number of users superimposed on the same resource block. From the second experiment, for a BER of FEC limit the SNR penalty is∼1 dB for the proposed MPA compared to original MPA. The research of this paper provides a feasible scheme for the next generation of optical access network.