Soliton-Based Physical-Layer Security: A Multi-Wavelength Nonlinear Probing Framework

Classical optical time-domain reflectometry (OTDR) and modern coherent reflectometryrely on linear pulse propagation, where small losses or covert taps may remain below thedetection threshold. Recent work has demonstrated that short-haul fiber monitoring canbe dramatically improved through full-wave inversion and 5σ backscatter analysis,extended with multi-wavelength sensing to achieve quantum-compatible linkdiagnostics. In this paper, we introduce a new paradigm for physical-layer securitybased on externally generated Kerr microcomb solitons. Rather than using solitons as datacarriers, we employ them as nonlinear probing waveforms whose stability, spectralsymmetry, and temporal area constraints ensure that even weak interactions—includingmicro-bend taps or mode-extracting couplers—leave deterministic, measurablefingerprints. We formalize a perturbation-sensitive security metric, derive a covariancemodel for soliton parameter shifts under tapping, and introduce an engineered “collapsethreshold” that makes probes intentionally fragile to unauthorized extraction. Thisenables a classical, quantum-ready, tamper-evident physical layer that complements andstrengthens emerging QKD and coherent security infrastructures.