A detailed analysis is presented of the possibility of an Er3+ and Pr3+ codoped fiber as an amplifier for 1.3 and 1.5 μm transmission windows. The numerical models with 1010/1480 nm and 986/1480 nm pump lasers are proposed, the rate and power propagation equations are solved numerically, and the dependence of the gains at 1310, 1530, and 1600 nm windows on pump wavelength and power, active ion concentrations, and signal wavelength are calculated. The results show that with 1010/1480 nm pumps of 200/100 mW and with fixed Pr3+ and Er3+ concentrations at 8.0×1024 and 2.0×1024 ions/m3, the signals at 1310 and 1530 nm windows may be equally amplified with a gain of 26.0 dB in the active fiber with a length of 7.0 m, and with a 1480/986 nm pump power of 100/300 mW and Pr3+ and Er3+ ion concentrations of 2.0×1024 and 2.0×1024 ions/m3, the signals at 1310 and 1530 nm may be nearly equally amplified with a gain of 8.0 dB in a 10.0 m long active fiber.