PERFORMANCE OF A DISTRIBUTED ERBIUM-DOPED DISPERSION-SHIFTED FIBER AMPLIFIER

Continued improvements in the performance of a multi-kilometer, low-erbium concentration fiber amplifier made by the MCVD "seed" fiber method are discussed. Transparency for a -20-dBm signal at 1.55-mu-m and fiber length of 11.8 km was achieved with 20 mW of 1.48-mu-m copropagating pump power. The wavelength dependence of the gain for this signal level is also reported and the distribution in small signal gain along a 22-km length using an optical time domain reflectometer (OTDR) was measured. Simulations are also presented to show the effect of erbium concentration, input signal level, and pump power required for transparency of a 50-km span.