Cascaded Two-Wavelength Lasers and Their Effects on C-Band Amplification Performance for ${\hbox {Er}}^{3+}$-Doped Fluoride Fiber

In this paper, we report cascaded two-wavelength 853-nm (
⁴
S
_3/2
rarr
⁴
I
_13/2
transition) and 1533-nm (
⁴
I
_13/2
rarr
⁴
I
_15/2
transition) lasing from Er
³⁺
-doped fluoride fiber pumped at 974 nm. The cavity for cascaded two-wavelength lasing is composed of two fiber ends with 4% Fresnel reflection. Its optical-to-optical efficiency is up to 26.6%. Its effects on C-band fiber amplifiers and green upconversion fiber lasers are discussed. A new way to get high efficiency and low noise C-band amplifier is suggested, i.e., a fluoride-based Er
³⁺
-doped fiber amplifier including 853-nm lasing cavity. Our simulated results show that such a new amplifier can enhance the signal gain greatly and break the limit of the saturated gain intensity for a normal amplifier