A novel efficient optimal design method for gain-flattened multiwavelength pumped fiber Raman amplifier

In this letter, it is revealed that there exits an approximate linear relation between the changes in input pump powers and the resulting changes in the pump-power integrals in multiwavelength pumped fiber Raman amplifiers (MW-FRAs). Based on this fact, a novel efficient optimal design method for gain-flattened MW-FRAs is proposed. First, the optimal integral pump spectrum is found by genetic algorithm. Then, the matrix denoting the linear many-to-many relation is calculated. By this matrix, the optimal input pump powers resulting in the optimal pump-power integrals can be easily calculated. The optimal pump spectrum is obtained without time consuming trial-error adjustments or many times numerical simulations. Compared to other existing optimal design methods, our method has a substantial improvement in the efficiency without any expense of accuracy.