Two Regimes, One Model: Unifying Breathing Soliton Dynamics in Fiber Lasers

We present a unified theoretical framework for fibre lasers in the breathing-soliton regime, revealing distinct formation mechanisms governed by cavity dispersion. Under net-normal dispersion, breathing solitons arise from the interplay of Q-switching and soliton shaping, whereas near zero net dispersion they are driven by Kerr nonlinearity and dispersion. These mechanisms underpin the markedly different experimental behaviours observed across the two regimes—including excitation conditions, oscillation periods, spectral features, and synchronisation properties—all accurately reproduced by the model.