Optical channel pre-emphasis equalization is experimentally researched for a 270 km 40×40 Gbit/s wavelength 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.
The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems.It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers.The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated.It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured.Considering the practically available optical sampling pulse sources,the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method.
