Application of a self-sweeping self-pulsing laser for high-resolution spectral analysis of π-shifted FBGs has been demonstrated for the first time. It is shown that the self-sweeping laser generates nearly single-frequency radiation during a single pulse. This fact allows us to characterize the shift-induced dip of 14 MHz width in the FBG reflection spectrum. Nonlinear deformation of the measured ultranarrow spectral structure with increasing incident power is observed. Sampling interval during the scan is shown to be limited by pulse to pulse frequency shift, which is equal to the cavity mode spacing of 6 MHz. The main feature of the applied technique is its simplicity due to the absence of special elements for frequency scanning.
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