Using an accurate and comprehensive computer model, we study the pump wavelength dependence of amplifier performance in the 800 nm band in erbium-doped fiber amplifiers. A comparison is made for both forward and bidirectional pumping over a wide range of pump powers. It is shown that 800-810 nm pumping is more efficient if bidirectional pumping is used, while 810-820 nm pumping is more efficient if only forward pumping is carried out. As we show, this is due to the effects of excited state absorption (ESA), in the 800 nm pump band. In alumino-phosphate-silicate (APS) erbium-doped fiber amplifiers the detrimental effects of ESA can be reduced significantly by using bidirectional pumping. Further, if a “Band Optimum Length” (BOL) is selected, a near optimum small signal gain (SSG) can be constant over a broad pump wavelength region and this is due to the combined effects of ESA and ground state absorption (GSA). The results show that single-longitudinal-mode or multi-longitudinal-mode, high power, reliable and inexpensive GaAlAs laser diodes can be used as pumping sources for EDFAs having SSG > 40 dB, noise figures of < 4 dB and output signal powers approaching 100 mW and these could be used as line repeaters, preamplifiers and power amplifiers in different lightwave systems.
We also analyze the performance that can be expected in fluorophosphate glass erbium-doped fiber amplifiers (EDFAs), with 800 nm band pumping. Due to the smaller excited state absorption, the fluorophosphate host glass shows about a 4-6 dB advantage in small signal gain (SSG) over alumino-silicate EDFAs with bidirectional pumping, and nearly double the output signal power for power amplifiers under similar conditions.