An energy supply system for implantable medical devices generates an energy supply by a photovoltaic converter which transforms the light coming from outside of the body. The light is carried to the converter by an optical fiber. This system allows the implanted devices to work without the time restrictions of batteries and opens the door to the development of new devices with much higher power ratings. The system includes a light source (1) external to the patient's body, an optical fiber (3) which runs from a point on the surface of the patient to the implantable device (4) and a photovoltaic converter (5) placed inside the device where the optical fiber ends. Finally, a power conditioning stage (6) ensures that the electrical power generated suits the needs of the other components (7) of the implantable device.