Abstract: Atmospheric optical turbulence is fractal. In this article, a high quality fiber optical turbulence sensing system is proposed to obtain time series of air refractive index fluctuations in optical turbulence under three conditions, i.e. , 0.48 meter above water, 1.8 meters and 23 meters above grassland on the Science Island in Hefei. With the time series data the Hurst exponent and fractal dimension of optical turbulence can be estimated using the method of R/S analysis. Diurnal variations and probability distributions of the two parameters are provided and analyzed. The results show that the fractal dimension under the three conditions varies with time in a day and becomes stable at noon. The dynamic range of fractal dimension is from 1.3 to 1.4, and its most probable value is about 1.35. Comparatively, the average value of fractal dimensions at the 1.8 meters above the grassland is the largest, and the value at the 23 meters above the grassland is the smallest. At last, the dependences of fractal dimension and intermittency exponent on the development of boundary layer atmospheric optical turbulence are briefly discussed.