This dataset contains the data associated with the paper "Asymptotically single-mode small-core terahertz Bragg fibre with low loss and low dispersion". Further details of the methods and results can be found in the paper: Hong, B., Swithenbank, M., Somjit, N., Cunningham, J., Robertson, I., Asymptotically single-mode small-core terahertz Bragg fibre with low loss and low dispersion, Journal of Physics D: Applied Physics. (in press) The title of each data file indicate the correlation betweent the data file and the figure in the paper. There are some brief descriptions about the data in each file providing some hints for the readers. The author use Matlab to produce these data and plot figures based on them. Some data associated with three-demensional figures in the paper are shown in three separate sheets but in a same file. They can be simply ploted by using Matlab command surf(x,y,z).