Ultra-broadband gain spectra of Co2+-doped fiber pumped at 1200 nm

• We present the energy level transitions and numerical model of Co2+-doped fiber.
• A quasi-three-level system is employed to model the gain spectra of fiber.
• The rate and power propagation equations are solved to analyze the effect of fiber.
• When pumped at 1200 nm, the fiber has ultra-broadband gain spectra in 1.25–2.00 μm.

This work investigates the energy levels, transition configuration and numerical model of Co2+-doped glass–ceramics fiber. A quasi-three-level system is employed to model the gain spectra of the doped fiber, and the rate and the power propagation equations are solved to analyze the effect of the fiber length, active ion concentration, pumping power as well as ambient temperature on the spectra. It is shown that the fiber has ultra-broadband gain spectra in 1.25–2.00 μm range via the 1200 nm pump, which is promising for full-band fiber amplifiers.