Ring core fibre as an optical amplifier

The ring shape of doped rare earth fibre (M-profile fibre) offers the possibility of stimulating luminescence from inside of the fibre with higher efficiency of coupling. In this type of fibre, the inner and outer claddings have lower than the ring core refraction index. The pump light is guided by the multimode inner cladding and the laser light is guided by the doped rare earth ions ring-core. The pump absorption is almost complete because of the geometry of that kind of fibre construction. In this paper, a ring coredoped Dy3+ ionsfibre is presented. In the first part of this report, an analysis of light transfer between inner cladding and ring-core optical fibre is presented. In the second part, the parameters of Dy3+ions doped ring core optical fibre manufactured by author are described. It seems that this kind of fibre may be used for optical amplifier construction.