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Relaxation Oscillations in Fiber-Grating-Tuned Erbium-Doped Fiber Lasers

Relaxation oscillations were studied experimentally and theoretically in a fiber-grating-tuned erbium-doped fiber laser with a doped fiber length of 7 to 9 m. Two regions of amplitudes in the relaxation oscillations were observed. For small-amplitude oscillations, the measured relaxation oscillation frequency agreed with that given by an approximate equation. For large-amplitude oscillations, chirping in the relaxation oscillation frequency was observed. A numerical analysis based on rate and propagation equations was performed to analyze this chirping. The results qualitatively agreed with those of the experiment. Wavelength tuning was also performed using a Peltier device. The tuning range was 2.1 nm for a grating in the 1.53–1.55 µ m region.