  Because of the unlimited range of state space, orbital angular momentum (OAM)
as a new degree of freedom of light has attracted great attention in optical
communication field. Recently there are a number of researches applying deep
learning on recognition of OAM modes through atmospheric turbulence. However,
there are several limitations in previous deep learning recognition methods.
They all require a constant distance between the laser and receiver, which
makes them clumsy and not practical. As far as we know, previous deep learning
methods cannot sort vortex beams with positive and negative topological
charges, which can reduce information capacity. A Multidimensional Information
Assisted Deep Learning Flexible Recognition (MIADLFR) method is proposed in
this letter. In MIADLR we utilize not only the intensity profile, also spectrum
information to recognize OAM modes unlimited by distance and sign of
topological charge (TC). As far as we know, we first make use of
multidimensional information to recognize OAM modes and we first utilize
spectrum information to recognize OAM modes. Recognition of OAM modes unlimited
by distance and sign of TC achieved by MIADLFR method can make optical
communication and detection by OAM light much more attractive.
