Abstract: A method of transmitting data in a wireless power transmission system comprising a power transmitter including a first and a second light source and means for directing the emitted light. The second light source is used for transmitting, parallel and as low-intensity pulses, light arranged around the light emitted by the first light source, data bits being encoded in the pulses so as to determine a maximum time interval between two successive pulses. At least one power receiver of the system comprises a first and a second photo-detector for receiving the emitted light and for converting it into electric current. The second photo-detector is used for indicating light pulses and data included therein and time between successive light pulses. A control signal indicating disturbance-free reception of data is transmitted to the transmitter if the time between successive light pulses does not exceed a predetermined maximum time interval.