Fig. 1. (a) ASE measurement setup. (b) The ASE spectra in different diameters of bent fiber circles.

Fig. 2. Relationship between the curvature loss and the diameter of the bent fiber circle.

Fig. 3. Experimental setup of the proposed all-PM fiber laser. PM LD, polarization-maintaining laser diode. PM WDM, polarization-maintaining wavelength division multiplexer. PM Yb401, polarization-maintaining ytterbium-doped fiber.

Fig. 4. Intensity dynamics of bidirectional all-PM self-sweeping Yb-doped fiber: (a) the microsecond pulse, (b) the zoomed view.

Fig. 5. Relationship between the diameter of the bent fiber circle and both threshold power and initial wavelength.

Fig. 6. Iconic spectral dynamics of self-sweeping regimes in different diameters of bent fiber circles: (a1) and (a2) 65 mm; (b1) and (b2) 18 mm; (c1) and (c2) 14 mm; (d1) and (d2) 10 mm; (e1) and (e2) 9 mm; (f1) and (f2) 8 mm.

Fig. 7. (a) Relationship of start and stop wavelengths and (b) sweeping rate and selected pump power varying with the bent diameter.