The measurements of electro-optical discharge characteristics and concentration of produced ozone were performed to evaluate the efficiency of ozone production in an AC surface dielectric barrier discharge (SDBD) in pure oxygen at atmospheric pressure. The discharge was driven in an amplitude-modulated regime with a driving AC frequency of 1 kHz, variable discharge duty cycle of 0.01-0.8 and oxygen flow rate of 2.5-10 slm. We observed asymmetric SDBD behaviour as evidenced by the variation in the ratio of the O(I)/O(2) (+) emission intensities registered during the positive/negative half-periods and complemented by the transferred charge measurements through the Lissajous figures. We also found a strong dependence of O(3) concentration on the discharge duty cycle. The highest calculated ozone production yield reached 170 g/kWh with a corresponding energy cost of about 10 eV/molecule when combining the lowest inspected duty cycle with the lowest AC high voltage amplitude.