When other dimensions of optical fiber transmission cannot be broken through, space division multiplexing technology provides a new development direction for improving the capacity of optical fiber transmission systems. Through the multi - dimensional multiplexing of space and mode, space division multiplexing technology can increase the transmission capacity of a single fiber by tens of times on the original basis, and is expected to solve the future data transmission capacity crisis. It represents the development trend of ultra - large - capacity optical fiber technology, a major innovation in the field of optical fiber communication technology, and the direction of the next-generation optical communication technology.