20-nm signal bandwidth after 147-amplifier chain using long-period gain-equalizers

Summary form only given. Long-haul, large-capacity wavelength-division multiplexing (WDM) transmission systems require broad WDM signal bandwidth, which can be expanded with broadband erbium-doped fiber amplifiers (EDFAs), gain-equalizers (GEQs), and pre-emphasis of optical senders. Twenty-four WDM signals transmission over 2526 km with a 18.4-nm bandwidth and 16 WDM signals transmission over 6000 km with a 12-nm bandwidth have been reported. In this paper, we demonstrate a 20-nm WDM signal bandwidth after 147-amplifier chain (5958-km transmission) using high alumina co-doped EDFAs and long-period gain-equalizers (GEQs). The main GEQs have free-spectral-ranges (FSRs) of 48 nm, which are about two times as long as the wavelength difference between a 1558-nm EDFA gain peak and a 1536-nm EDFA gain valley.