Ytterbium-doped optical fiber preform, ytterbium-doped active optical fiber and preparation method thereof

The invention discloses an ytterbium-doped optical fiber preform, an ytterbium-doped active optical fiber and a preparation method of the ytterbium-doped optical fiber preform. Firstly, a quartz deposition tube with a loose core layer deposited on the inner surface is prepared by adopting an MCVD (modified chemical vapor deposition) process, after heating and pulling off a tail tube at one end, ytterbium-containing rare earth salt and a co-doping agent solution are injected into the quartz deposition tube, and after full soaking, drying and melting shrinkage are performed to obtain a rare earth-doped core rod; and in the fusion shrinkage stage of the liner tube, steam containing an ytterbium compound is introduced into the tube, so that loss caused by outward diffusion and volatilization of ytterbium oxide in the fusion shrinkage stage of the liner tube is reduced, and the uniformly-doped ytterbium-doped optical fiber preform is obtained. According to the prefabricated rod prepared by the method, the ytterbiu