  The orbital angular momentum (OAM) has attracted widespread attention due to
its ability to carry information in multiple dimensions. However, a
high-dimensional entanglement carrying OAM can be affected by environment and
undergoes decoherence. Ensuring the stability and high fidelity of entangled
states after transmission is a crucial part of quantum communication. How to
control the entangled states are essential. In this paper, we produce the
polarization entangled photon pairs by type I BBO crystals by means of
spontaneous parametric down-conversion (SPDC), we achieve the polarization-OAM
hybrid entangled states by q-plate (QP) by means of manipulating the
multi-degrees of freedom of the quantum state after passing through the APD
communication channel. The polarization entangled photon pairs have the
characteristics of OAM. We use polarization degree of freedom to modulate OAM
degree of freedom, our polarization-OAM hybrid entangled states can slow down
the reduction of the fidelity in the during of transmission process. Our
quantum states exhibit a superior level of fidelity contrast with the
conventional situation. This method will provide a theoretical guidance for
improving the transmission fidelity of OAM states in fiber.
