In 5 G forward network

single fiber bidirectional technology is one of the important characteristics. Compared with single-fiber bidirectional technology in 4 G and Fiber To The X（FTTx） networks

single-fiber bidirectional technology in 5 G forward network is more complex. In this paper

several schemes to realize single-fiber bidirectional transmission in 5 G forward network are first introduced. Then the key optical devices to realize single-fiber bidirectional transmission and the crosstalk problem of single-fiber bidirectional system are analyzed. The comparison result shows that the single-fiber bidirectional scheme based on a single Dense Wavelength Division Multiplexing（DWDM） device has more advantages than the single-fiber bidirectional scheme based on an optical ring device.