Fig. 1. (a) Setup of the gain coefficient measurement at 915 nm of the Nd3+-doped silica fiber. (b) Net gains versus pump powers of a 4.5 cm Nd3+-doped silica fiber for different signal powers (P_s).

Fig. 2. (a) The experimental setup of 915 nm Nd3+-doped silica fiber laser. (b) 915 nm laser spectrum of Nd3+-doped silica fiber. The inset is the energy level of Nd3+. (c) The laser output power with different lengths of gain fiber versus pump power (CE: optical-to-optical conversion efficiency).

Fig. 3. Dependence of optical-to-optical conversion efficiency on the reflectivity of LR-FBG (70%, 83%, 90%) with a 5.1 cm fiber length.

Fig. 4. (a) Laser spectrum with a 0.02 nm OSA resolution. The inset is the output laser power versus the launched pump power. (b) The longitudinal-mode properties of DBR 915 nm fiber laser measured by FPI. (c) A brief schematic diagram of reducing the number of longitudinal modes in the DBR cavity.