Orbital Angular Momentum Nondegenerate Index Mapping for Long Distance Transmission

Abstract

Orbital Angular Momentum (OAM) has been considered as a new dimension against the traditional domains based on the electric field strength of Electro-Magnetic (EM) waves. For the long distance transmission more than 1 km, especially for the EM waves under 300 GHz, only a partial wavefront can be received. In this case, the orthogonality of OAM cannot be easily maintained as it does in the coaxial all phase plane receiving. In this paper, we introduce the concept of OAM nondegenerate index mapping in the partial phase plane receiving, in which the user information bits are mapped to the indices of the available OAM mode combinations (by adjusting the on–off status of available OAM modes). Then, besides the classical two-dimensional signal constellations in the traditional main channel, the OAM-based index mapping transmission scheme can be established and provide the additional index channel to convey information by the variation of OAM modes. Moveover, in order to confirm the validity and efficiency, a 30.6 km long distance transmission experiment with the proposed OAM index mapping scheme is also carried out.