AbstractBecause of the progress in optical communication technology, understanding the propagation characteristic of optical fibers has become very important. In particular, since optical networks have been used widely, the evaluation of optical fibers in the field is essential.This paper describes the measurement of the chromatic dispersion of optical fibers and a system suitable for the measurement in the field. The approach is based on the baseband phase‐comparison method. First, the conditions required for this measurement system will be clarified. Then the measurement of wavelengths and wavelength separation satisfying the requirements will be obtained by simulation. The source of each wavelength must be modulated.However, to increase the fiber length and to improve measurement precision, a modulation method based on multiple sinusoidal waves will be proposed, and the upper and lower limit of the optimum modulation frequency will be clarified. The measurement system will be constructed from these results. The technical problems in realizing the system will be shown.Finally, an example of data measured by the constructed system will be shown, and it will be demonstrated that a resolution of 0.01 ps/nm/km and measurement precision of ± 0.3 ps/nm/km can be achieved at wavelengths of 1.3 and 1.55