An optimal power calibration process in which an OPC process is performed on the outer OPC area (12) of an optical disc (10) at a plurality of write speeds a, b and c, and an OPC process is also performed on the inner OPC area (14) at the write speed thereof. The optimal powers (and strategies) obtained by each OPC process for each speed is then used to create a function matching writing power level to speed. In order to create an accurate optimum laser power for all radii, two OPC power factors can be created: a media variation power factor a speed power factor In order to create the media variation power factor, Nx1 OPC information obtained from both the innermost and the outermost radii of the optical disc are used; whereas in order to create the speed power factor, the Nxl, Nx2,..., Nxm information obtained from the outermost radius of the disc is used. Using the above-mentioned two power factors, more accurate control of the required laser power for all radii can be achieved. |