CWDM12 semi-active central office line card for improving the efficiency of optical fiber core.  It is deployed in the DU office room of the fronthaul network to achieve CWDM1:12 single fiber bidirectional multiplexing transmission, supporting monitoring the optical power of branches in the upstream and downstream directions, also achieving 1+1 protection of the primary and standby optical cable routes between DU-AAU, ensuring that the 5G fronthaul solution meets the requirements of monitoring, management and convenient production.