The photonic lantern is a mode multiplexer/ demultiplexer used to improve the transmission capacity. The SMF cluster is embedded into a low refractive index capillary for adiabatic tapering, and then the tapered end is spliced with a few-mode fibre, fundamental mode in SMF is converted into the specific modes in FMF to realize a mode conversion and multiplexing ,The photonic lantern utilizes the orthogonality among various modes arising in few-mode fibres to greatly increase the number of data transmission channels and improve the transmission capacity.