We present a method for high-resolution optical frequency domain reflectometry by de-embedding group-velocity dispersion in the device under test. The method is shown to provide an accurate estimation of the wavelength-dependent group refractive index, and provides a spatial resolution of 5.3 ± 1.7 μm for intra-chip reflections. We applied this method to characterize localized reflections from a number of waveguide crossings. The minimum distance of 30 μm between two crossings could easily be resolved. The reflection of waveguide crossings was analyzed to be (2.5 ± 1.2)·10-6.
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Zhao et al. (2017) studied this question.