Effect of direct coupling of microrings on the gain bandwidth of cascade microring Raman amplifier

A combination of coupled microrings that are coupled to a bus waveguide is proposed as a wide-band microring Raman amplifier. This structure is called one channel coupled microrings (OCCM) Raman amplifier. It is shown analytically that the number of poles in the OCCM transfer function is greater than the square of microrings number (N). The gain bandwidth and gain ripple of the proposed amplifier are increased and decreased, respectively due to increasing the number of poles and zeros in the transfer function. An iterative matrix method is introduced to solve Raman equations in the amplifier with arbitrary number of microrings and Genetic algorithm is employed to maximize the gain flatness.