Chromatic dispersion is a wavelength dependence of a group velocity of an optical fiber, and is an important fiber characteristic in fabricating pulse fiber lasers because it affects spectrum and pulse width. One of the chromatic dispersion measurement methods is a phase shift technique, which measures a relative phase shift between intensity-modulated lasers with different wavelengths. A disadvantage of this measurement method is that fiber lengths of several hundred meters or more are required to obtain high time resolution. Therefore, specialty fiber with short production lengths and amplification fiber that absorbs light of a specific wavelength, used for pulse fiber lasers, is difficult to measure with the method.


This study aims to develop a chromatic dispersion measurement method that can evaluate specialty fiber and amplification fiber using a short fiber under test of a few meters. The measurement light source used is a broadband light of high brightness and fiber optics that we developed. The feature of this study is that the fiber under test constitutes a Fabry-Perot resonator using the Fresnel reflections at both endfaces of the fiber. Enables measurement with the short fiber under test because it is measured from a standing wave of the resonator. The wavelength dependence of reflection characteristics from the standing wave is measured to obtain a relative group delay. Chromatic dispersion can be obtained by measuring the group delay difference at different wavelengths. Also, the fiber under test is the resonator, therefore measurement can be done without connectors and end face polishing.