| We report on the first experimental observation of spectral Bloch oscillations in an optical fiber system employing the interaction between a probe signal and a traveling-wave periodic potential. The spectrum of weak probe pulses is shown to oscillate owing to its group-velocity mismatch to the periodic field. The behavior of a continuous-wave probe spectrum reveals the actual discrete nature of the effect, and recurrences of the spectrum after one and two Bloch periods are demonstrated. |
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