Orthogonal coding methods for increasing the number of multiplexed channels in coherent beam combining

Abstract

We introduce orthogonally coded modulations for active coherent beam combining (CBC), and show how using Walsh codes enables the increase of the number of combined channels. Analytical, numerical, and experimental results are presented and compared to the standard multifrequency dithering technique, demonstrating that at least 5 times more fibers can be combined using the same modulation frequency. The modulation format excluded, no particular changes in the system need to be introduced and the benefits of active coherent beam combing, such as atmospheric turbulence compensation capability, are kept unchanged. Finally, we point out that this approach can be applied in partially CBC.