Sm. Hwang et Ae. Willner, GUIDELINES FOR OPTIMIZING SYSTEM PERFORMANCE FOR 20 WDM CHANNELS PROPAGATING THROUGH A CASCADE OF EDFAS, IEEE photonics technology letters, 5(10), 1993, pp. 1190-1193
We analyze 20 wavelength-division-multiplexed (WDM) channels propagati
ng through a cascade of erbium-doped fiber amplifiers (EDFA's) coverin
g megameter distances. Optimal operating conditions are found for achi
eving a high signal-to-noise ratio (SNR), with as small an SNR differe
ntial between channels as possible without resorting to external equal
ization methods. Issues considered are the link loss between amplifier
s, the small-signal gain per amplifier, the wavelength and power of th
e pump, and the input signal power. We find that the link loss is the
most critical parameter for narrowing the SNR differential among the 2
0 channels. Furthermore, 20-dB small-signal gain for each amplifier pr
ovides the highest overall SNR for the 20 channels transmitted across
4500 km. Additionally, either 0.98 or 1.48 mum pump wavelength can be
equivalently used, and the cascade performs well with moderate pump an
d signal powers.