Novel Er and Ce codoped fluoride fiber amplifier for low-noise and high-efficient operation with 980-nm pumping

We demonstrate the low-noise and high-gain operation of a fluoride Er/sup 3+/ and Ce/sup 3+/ codoped fiber (F-ECDF) amplifier with 980-nm pumping. A 980-nm-pumped F-ECDF with a length of only 45 cm exhibits a noise figure of <4.5 dB in the entire C-band and a small signal gain of >20 dB with a gain ripple of <1 dB without any gain-flattening filter in the 1525-1560-nm range. Excitation spectra for the gain and noise figure of an F-ECDF exhibit flat shapes in the 974-982-nm range. We also demonstrate that the gain coefficient reaches 1.4 dB/mW and the power conversion efficiency is 27.4% at 1532 nm for a 2.25-mlong F-ECDF.