Gain property analysis of a quantum dot doped inner cladding fiber

A quantum dot (QD) doped fiber amplifier (QDFA) was theoretically modeled by using a two-level system. Combining with the finite difference-beam propagation method (FD-BPM), the proposed numerical method can calculate the signal gain efficiently. In this fiber amplifier, the PbS QD was as an active inner cladding. With the unique cladding structure of the doubly clad optical fiber, we can get good transmission stability, pump utilization and big mode field of the signal light. After a proper structure design of the PbS QD inner-cladding doped fiber, the 160nm bandwidth of the gain spectra can be achieved, which covers the S-C-L band of the optical communication band. And the noise figure of the amplifier presents a very flat characteristic. The optimization of the inner cladding doped model is also presented in the paper.