A method of measuring dispersion in an optical fiber (50) without cutting the second end is disclosed. An optical measurement signal (20) comprising timed pulses is input into one end of the fiber, and a small loop (60) is formed at the point to which total dispersion is to be measured. In one embodiment the loop (60) is formed so as to increase the amount of light that escapes the fiber at the loop (60), and the escaping light pulses are monitored by a detector (70). The wavelength of the optical measurement signal is varied, and the change in timing of the detected optical pulses is measured, thus indicating the dispersion. In a second embodiment the loop (60) is formed so as to increase the amount of loss in the optical measurement signal, and an OTDR is utilized.