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 energ y transfer. It is summarized with respect to the pumping wavelength and pow er allocation. The comparisons between simulated and experimental results a re presented. Section 2 reviews the fundamentals of Raman amplifier. In thi s section, Raman gain spectra measured for different fibers are presented a nd the difference among the spectra is discussed. Section 3 describes the w ay to determine the pumping wavelength allocation by introducing superposit ion method. By means of this design method, some optimized design examples are presented, where the peak levels of Raman gain are fixed to 10 dB for t he wavelength range from 1525 nm to 1615 nm (C- plus L-band) in all cases. From these results, it is confirmed that batter gain flatness can be obtain ed by using the larger number of pumps. Section 4 explains how the pump-to- pump 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 proced ure: can be simplified: (1) one determines pump wavelengths with which a de sired composite Raman gain can be obtained by adding in logarithmic scale i ndividual Raman gain spectra shifted by the respective wavelength differenc es with adequate weight; factors. And (2), one predicts how much power shou ld be launched in order to realize the weight factors through precise numer ical simulations. Section 5 verifies the superposition rule and the effect of pump-to-pump energy transfer by comparing a measured Raman gain with a s uperposed one. The agreement of two gain profiles shows that the multi-wave length pumped Raman gain profile contains only the individual gain profiles created by the respective pump wavelengths. Section 6 concludes this paper .