The key technology in practical optical fiber quantum private communication is the co-fiber-transmission technology for quantum signal and classical optical signal. The cost of quantum private communication network construction can be decreased remarkably by the co-fiber-transmission technology. The co-fiber-transmission principles of propagating classical optical signal together with discrete-variable quantum signal and continuous-variable quantum signal are compared. The co-fiber-transmission of discrete-variable quantum signal, continuous-variable quantum signal and classical optical signal based on mode division multiplexing in few-mode fiber (FMF) is proposed to reduce nonlinear damage and noise. This new scheme can use the fiber resource efficiently. A stable and efficient quantum private communication network is established when we integrate the technical advantages of discrete-variable quantum key distribution and continuous-variable quantum key distribution.