High-precision inter-core skew measurement for multi-core fiber using incoherent interferometry based on sliced-ASE noise

We propose and experimentally demonstrate an inter-core skew measurement method for multi-core fibers (MCFs) based on broadband incoherent interferometry of spectrum-sliced amplified spontaneous emission (ASE) noise. The technique avoids the need for narrow-linewidth lasers and tolerates the random power fading due to coherent coupling among neighboring cores. By utilizing a calibrated interference spectrum to extract the delay value through cascaded filtering and fitting, the proposed technique achieves sub-picosecond measurement accuracy. Both the back-to-back and 41-km MCF experiments demonstrate stable performance with root mean square errors of <60 fs, comparable to the typical measurement scheme based on a vector network analyzer. The simplicity, robustness, and sub-picosecond precision make the proposed scheme an ideal solution for non-intrusive, online inter-core skew monitoring in multi-core fibers.