Full text can be accessed at http://www.tandfonline.com/doi/abs/10.1080/002072198134959There have been numerous reports on the distortions suffered by gaussian-shaped pulses transmitted through dispersive optical fibres. Such distortions are in the form of pulse broadening due to second-order fibre dispersion and the breakdown of the transmitted pulses into multiple pulses due to third-order dispersion. In this paper, the distortions suffered by square-shaped pulses transmitted through dispersive optical fibres are investigated. It is shown that square-shaped pulses suffer the same kinds of distortions as gaussian-shaped pulses.