The MDM transmission system uses the limited orthogonal modes in few mode fibre（FMF） as the independent channels to carry out information transmission in order to multiply the transmission capacity of the system. The few mode optical fibre uses different modes in the fibre as a new degree of freedom, the spectrum efficiency of the system can be improved successfully by FMF. As FMF has large mode field areas, its nonlinear tolerance is always better than that of SMF. It not only improves the capacity of optical transmission system, but also avoid the nonlinear effects. The MDM system based on FMF can solve the future single mode fibre bandwidth crisis. YOFC FMFs taking advantages of PCVD process which is able to manufacture complex index-profile accurately , can get various types of core layer structure, such as Step-Index, Graded-Index etc.According to different design, 2-mode, 4-mode, 6-mode, 9-mode FMFs and even Ultra-low-loss(ULL) FMFs can be realized.