32×10 Gbit/s transmission over 8000 km using hybrid Raman-Erbium doped fiber optical amplifiers

摘要

Wavelength Division Multiplexing (WDM) has been now widely used to demonstrate the transmission of high capacity based on 10 Gbit/s modulation per wavelength [1-4]. Increasing the number of wavelengths however raises in particular the problems of signal-to-noise ratio reduction and optical amplifier gain equalization. One solution is to take benefit fr6m the Raman amplification features to improve the optical amplifier n6ise figure and to provide active gain equalization. Signal-to-noise ratio (S NR) improvement has been already reported in a long-haul transmission experiment using only Raman amplification [5]. This technique however requires very high pump power and the low gain compression of Raman amplifiers can induce unstable system performance. Therefore, if Raman amplification is combined with erbium doped fiber amplifier, the SNR can be improved while still keeping the high gain compression and output power provided by the erbium doped fiber amplifier. To demonstrate the efficiency of this kind of hybrid amplifier configuration, a 32×10 Gbit/s transmission experiment over 8000 km has been conducted on a recirculating loop. The system performances obtained with the Raman gain turned on and off are compared and analysed with regard to theoretical predictions. In addition, active gain equalization through Raman gain control is demonstrated as an efficient technique to compensate for the gain tilt due to span loss increase induced by system ageing in case of an industrial submarine transmission system.