Abstract

In dense wavelength-division-multiplexed (DWDM) optical networks containing concatenated chains of optical amplifiers, maintaining an adequate signal-to-noise ratio (SNR) over the range of wavelengths occupied by the WDM channels is a major issue because of the nonuniform wavelength-dependent gain profile and saturation characteristics of erbium-doped fiber amplifiers (EDFAs). Previous studies of gain equalization^2-4 have dealt with EDFAs pumped at 1480 nm. Another possible solution, which would be much simpler, would be to pump at 980 nm. Because the inversion in 980-nm-pumped EDFAs is generally more complete, the gain spectra should be relatively flatter. We present here measurements for a chain of four EDFAs pumped at 980 nm in which, without any other form of gain equalization, the gain and optical SNR spectra are relatively flat from 1540 to 1562 nm, covering the range of likely channels to be used in many DWDM applications.

© 1994 Optical Society of America