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Sub-picosecond inter-core skew characterization in multicore fibers via Hong-Ou-Mandel interference
Optics Express
|August 14, 2026
Summary
We developed a high-precision method using two-photon interference to measure inter-core skew in multicore fibers. This technique significantly improves accuracy for characterizing fiber optic networks used in classical and quantum communications.
Area of Science:
- Photonics and Optical Communications
- Quantum Information Science
- Fiber Optics Metrology
Background:
- Inter-core skew (ICS) is crucial for multicore fiber (MCF) performance in classical and quantum networks.
- Existing methods like C-OTDR lack precision for long, installed fibers due to path fluctuations.
Purpose of the Study:
- To present a high-precision measurement technique for ICS in MCFs.
- To characterize ICS across various fiber lengths and deployment scenarios.
- To establish a practical platform for timing uniformity assessment in MCF networks.
Main Methods:
- Utilized two-photon Hong-Ou-Mandel (HOM) interference with spontaneous parametric down-conversion (SPDC) and weak-coherent-state sources.
- Employed a fiber-integrated 4x4 multiport beam splitter for measuring differential group delay.
- Extracted ICS values by analyzing HOM interference fringe positions across all core-pair combinations.
Main Results:
- Achieved a precision of ±0.11 ps for two-photon interference, a ~180-fold improvement over C-OTDR.
- Demonstrated ICS scaling consistent with random-walk behavior (στ(L) = κL + c) with κ = (39.80 ± 0.003) ps/km.
- Successfully measured ICS in a 1300m field-deployed fiber with >10 dB loss using a weak-coherent-state source.
Conclusions:
- HOM interference offers superior precision and robustness against path fluctuations for ICS measurement in MCFs.
- The developed method is suitable for both laboratory and field applications, advancing MCF network characterization.
- This technique supports the development of next-generation classical and quantum communication systems.
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