We present a relay system which uses RF over Optical (RFoO) to provide wireless communications in RF sensitive areas. Different from other relay systems, we adopt RF band phase shift beamforming to adjust phases of RF signal before modulating it into an optical band. Benefitting from it, the energy of transmitted signal is able to be concentrated in desired areas. In the designed system, the relay station performs training towards mobile devices by sending training sequences from each of pre-defined transmit beam patterns, then mobile devices indicate training index to the relay station when the received signal strength is maximized. A cross layer design is proposed, which not only improves system transmission performance with a very short beamforming setup time, but also provides a safe propagation environment, which would open a new vista to solve the wireless communication in RF sensitive area.