A distributed reception based method for identifying vortex beams

Abstract

After the vortex beam is transmitted in the space laser communication scene for hundreds of kilometers, the spot diameter will expand to several meters or even tens of meters, and the existing detection methods that require receiving the whole spot are no longer applicable. In order to address this problem, a distributed detection scheme is proposed in this paper for demultiplexing two L-G beams. We choose two specific points on the light spot to receive two optical signals. Then the two optical signals are interfered with a designed optical fiber path which use the cross-coupling of the coupler. Then the demultiplexing is achieved according to the interference results at two ports. This scheme is suitable for demultiplexing intensity-modulated optical signals. The feasibility of this scheme is theoretically analyzed, and the demultiplexing of L-G beams with multiple combinations of topological charge numbers is realized.