White-Light Interferometer Based on a High-Precision Chromatic Dispersion Measurement Method

We report a high-precision chromatic dispersion measurement method for very short optical fibers by using interference spectra of a Mach-Zehnder interferometer with a white-light source or a broad-band light source. This method is a modified version of the spectral white-light interferometry reported by J. Y. Lee and D. Y. Kim and is very effective for measuring the dispersion of short single-mode fibers (SMFs) whose lengths are less than a few tens centimeters. Our new method utilizes phase changes of the interference spectrum of the interferometer with a fiber-under-test (FUT) compared to that with no FUT to eliminate the background effect caused by the optical path itself of the interferometer. Our measured results show that the background effect becomes significant as the length of the FUT is shortened close to 10 cm for both standard SMFs and dispersion-shifted fibers (DSFs). This measurement method can be used to investigate the dispersion parameters of very small-sized waveguides or optical samples, such as nanophotonic devices and of any other optical materials of short lengths.