Optimal pump wavelength in the /sup 4/I/sub 15/2/-/sup 4/I/sub 13/2/ absorption band for efficient Er/sup 3+/-doped fiber amplifiers

The authors report the measured gain of a highly efficient erbium-doped fiber amplifier pumped at wavelengths between 1.46 and 1.51 mu m. The optimal pump wavelength, lambda /sub opt/, was determined to be 1.475 mu m. At this wavelength, the maximum gain coefficients for signals at 1.531 and 1.544 mu m were 2.3 and 2.6 dB/mW, respectively. At lambda /sub opt/, high gains ranging from 32 dB at pump power P/sub p/=20 mW up to 40 dB at P/sub p/=80 mW were obtained. These modest pump powers are within the capabilities of currently available 1.48- mu m diode lasers. The width about lambda /sub opt/ for 3-dB gain variation exceeded 27 nm for P/sub p/=10 mW and 40 nm for P/sub p/>20 mW. With this weak dependence on pump wavelength, single-longitudinal-mode lasers do not have a significant advantage over practical Fabry-Perot multimode pump lasers.>