As the deployment of wireless networks becomes more and more intensive, the scale of large-capacity distributed base stations is also expanding. The deep coverage of base stations requires the location of the deployment to be closer to users. The passive optical fiber expander utilizes the characteristics of a single optical fiber that can transmit multiple optical carriers of different wavelengths at the same time. It effectively solves the problem of the lack of optical fiber cable resources between BBU and RRU/DU and AAU in the C-RAN architecture, and meets the requirements for deep coverage and flexible expansion of carrier base stations.