Short erbium doped phosphate fiber amplifiers

Spectroscopic properties of high concentration Er3+-doped phosphate glasses and performance of short Er3+-doped phosphate fiber amplifiers were studied and characterized.;Systematic studies of cooperative upconversion of Er3+ ions in 4I13/2 level and energy transfer from Yb 3+ to Er3+ in phosphate glasses were performed by a rate equation formalism. The cooperative upconversion coefficient for an Er 3+ concentration of 4 × 1020 ions/cm3 was found to be 1.1 × 10−18 cm 3/s. An energy transfer coefficient of 1.1 × 10−16 cm3/s was found for an Yb3+ concentration of 6 × 1020 ions/cm3 and an Er 3+ concentration of 2 × 1020 ions/cm3 . Energy transfer efficiencies from 2F5/2 level of Yb3+ ions to 4I13/2 level of Er3+ ions higher than 95% were determined from our measurements under weak excitation.;The performance of high concentration Er3+-doped phosphate fiber amplifiers were characterized in terms of gain, noise figure, and signal saturation for a series of active fiber lengths, pump powers, signal input powers, and signal wavelengths. A net gain of 21 dB were achieved in a 71 mm Er3+-doped phosphate fiber with a noise figure of ∼5.3 dB by a 980 nm pump power of 244 mW. In addition, a 10 dB net gain can be obtained with a pump power of 110 mW. Performance of short Er 3+-doped phosphate fiber amplifiers demonstrates the potential for device applications.