For an accurate characterization of fiber dispersion,we propose a swept-frequency measurement of chromatic dispers ion based on the phase-intensity modulation conversion in a dispersive optical fiber.In principle,the fiber dis persion introduces additional phase shifts and causes the periodical fading of the phase-modulate d signal,which allows to determine the dispersion from the fading frequency.In practice,the f ading signals are very noisy and unstable due to close to the unavoidable noise floor,which makes it very difficult to precisely determine the notch frequencies.For an improved accuracy of charac teristic notch frequency,the polynomial fitting of the fading curve is adopted in our method. In the experiment, our method is verified by long and short fibers with different amounts of disp ersion.Experimental results show that our measurement holds a relative error of less than 0.22%.Mor eover,our method is applicable for the chromatic dispersion measurement at different operating wa velengths and dispersive fibers only by using a vector network analyzer and an optical phase m odulator,and it gives both the value and the sign of the chromatic dispersion with very simpl e configuration.