Demonstration of 540-dB loss compensation over 52 nm gain bandwidth with wideband erbium-doped fiber amplifiers

To increase the transmission capacity of a wavelength-division multiplexed (WDM) system, numerous works concentrated on the extension of erbium-doped fiber amplifier (EDFA) bandwidths. Recent reports showed that ultra-wide bandwidths, wider than 80nm were possible by using both the C-band (1550nm band) and L-band (1580nm band). System experiments showed the possibility of their application to real systems. In spite of the large bandwidth of the single ultra-wideband EDFA, bandwidth-distance products on the demonstrations limited to less than 24K nm-km (55.6nm/spl times/400km, 40nm/spl times/600km). The key issues are how to maintain the flat gain with transmission distance increase and how to achieve low noise figure for L-band EDFAs. In the work, we demonstrate a 124K nm-km (52nm/spl times/ 2400nm) transmission of 51 channels at 17dB of the optical signal to noise ratio (OSNR), by employing a low-noise wideband amplifier in conjunction with an all-fiber acousto-optic tunable filter. We have employed a re-circulating EDFA loop which consists of acousto-optic modulators, a single mode fiber, an attenuator, an isolator, a polarization scrambler, and an wideband EDFA (WEDFA).