Channel Pre-emphasis Equalization for a 270 km 40×40 Gbit/s WDM System with Cascaded EDFAs/Raman Amplifiers

Optical channel pre-emphasis equalization is experimentally researched for a 270 km 40×40 Gbit/s wavdength division multiplexing(WDM) transmission system with three Erbium-doped fiber amplifiers(EDFAs)and Raman amplifiers concatenated as booster amplifier.The channel imbalance of the overall system changes with different sets of power launched into EDFAs.By appropriately choosing the power input to concatenated EDFAs.the output spectrum of 40 channel signal can be equalized to the most extent.The merit of benefit can be around 5.5 dB by this pre-emphasis equalization.The requirement for the gain equalizer is therefore greatly released.Then the gain imbalance of the overall system and the power imbalance of 40 channels are compared and the two almost matches,but the significant difference lies on some channels.Finally,the pump power into Raman amplifier is also optimized,and another 1.3 dB improvement of channel equalization can be further achieved.