Broadband Raman amplifier for WDM

We have developed the design procedure of multi-wavelength pumped Raman amp lifiers, introducing superposition rule and account for pump-to-pump energy transfer. It is summarized with respect to the pumping wavelength and powe r allocation. The comparisons between simulated and experimental results ar e presented. Section 2 reviews the fundamentals of Raman amplifier. In this section, Raman gain spectra measured for different fibers are presented an d the difference among the spectra is discussed. Section 3 describes the wa y to determine the pumping wavelength allocation by introducing superpositi on method. By means of this design method, some optimized design examples a re presented, where the peak levels of Raman gain are fixed to 10 dB for th e wavelength range from 1525 nm to 1615 nm (C- plus L-band) in all cases. F rom these results, it is confirmed that better gain flatness can be obtaine d by using the larger number of pumps. Section 3 explains how the pump-to-p ump energy transfer changes the gain profile by experimental and simulated results. In this section, simulation modeling to perform precise numerical simulation is also presented. From the above discussion, the design procedu re can be simplified: (1) one determines pump wavelengths with which a desi red composite Raman gain can be obtained by adding in logarithmic scale ind ividual Raman gain spectra shifted by the respective wavelength differences with adequate weight factors. And (2), one predicts how much power should be launched in order to realize the weight factors through precise numerica l simulations. Section 5 verifies the superposition rule and the effect of pump-to-pump energy transfer by comparing a measured Raman gain with a supe rposed one. The agreement of two gain profiles shows that the multi-wavelen gth pumped Raman gain profile contains only the individual gain profiles cr eated by the respective pump wavelengths. Section 6 concludes this paper.