Optical Wireless Communication (OWC) has been always regarded as a technology guaranteeng a strong immunity to Radio Frequency electromagnetic interference. However, as a matter of fact, no accurate studies have been realized in low cost practical implementations of this technology. For the establishment of the OWC in real scenarios it is paramount to have an electromagnetic characterization of the environment, considering the effects of Radio Frequency interference on system performance. A proper analysis of interference prevents Electromagnetic Compatibility issues between a Visible Light Communication system (VLC) and the other components of the architecture and, overall, underline critical frequencies that could be potentially exploited by electromagnetic attacks. Based on these premises, an extended analysis of the effects caused by electromagnetic radiations on a typical VLC Tx-Rx pair has been realized in this work. In particular, two optical prototypes have been developed and tested in a controlled environment. Plane waves, generated at different power levels and in a wide frequency range, represent the intentional interference sources. The effects on data communication, considering Pulse Position Modulated (PPM) as useful optical signal, have been measured and shown. Effects on time domain and Bit Error Rate (BER) have been reported. In order to reduce the effects of the disturbing EM fields on the VLC system, we have integrated an electromagnetic shield and we have evaluated its impact through extensive measurements.