On the Use of Reflective Measurements for Modal Dispersion Analysis in SDM Fibers

We present an investigation into the use of reflectometric measurements for characterizing modal dispersion in optical fibers that support space-division multiplexing. A theoretical framework is provided to relate the dispersion characteristics observed in round-trip propagation to those measured in standard forward transmission. The proposed model is experimentally validated using a reflective configuration of an optical vector network analyzer, which enables single-ended access to the fiber. Improved experimental data are obtained with a stabilized laser source, significantly enhancing the signal quality and confirming the theoretical predictions with higher accuracy. In addition, we discuss practical considerations related to system calibration, including the compensation of temporal skew introduced by optical circulators and receiver-side polarization imbalance. The results highlight the potential of reflectometric techniques for accurately characterizing quasi-distributed advanced fiber links.