Extreme-dispersion-resistant optical true time delay line enabled by phase-domain pre-compensation

Optical true time delay lines (OTDLs) based on dispersion tuning suffer from dispersion-induced signal distortion, which in turn restricts the delay extension. In this work, we present an extreme-dispersion-resistant OTDL architecture employing a novel, to the best of our knowledge, phase-domain pre-compensation. The dispersion distortions are transformed into power-fading-immune phase shift and pre-compensated via polarization-diversity modulation, exhibiting enhanced resistance to signal degradation. Experimental validation in an OTDL link with -2021.7 ps/nm of dispersion at 1550 nm demonstrates significant signal quality improvements. Compared with traditional OTDL, our approach reduces mean EVM from 17.47% to 10.93% for a 2.5Gbaud 16QAM and from 16% to 8.86% for a 1Gbaud 64QAM, approaching back-to-back levels. The proposed scheme promises high-fidelity signal transmission in dispersion-challenged OTDLs.