(optimum-power-calibratio, opc) OPC is found in the newerd 8X CD-R drives. 4X drives, for example, calibrate the laser at the beginning of the CD and then use the fixed laser power across the entire CD surface. The OPC circuit allows the laser outp8ut power to continuously adjust to the CD surface throughout burning. CD-Rs produced with OPC show the lowest BLER rates ever - less than 5 on most CDs.