Fig. 1. Experimental setup of the all-fiber frequency-shifted laser. EDF: Erbium-doped fiber; GSA: graphene saturable absorber; WDM: wavelength division multiplexer; OC/ISO/WDM—output coupler/isolator/WDM hybrid component.

Fig. 2. SEM images of the fabricated HNLF.

Fig. 3. Measured dispersion characteristics of the HNLF and DCF fibers (dotted lines). Blue solid line represents the HNLF dispersion curve calculated based on the actual geometry of the fiber. Red solid line is the polynomial fitting of the measured DCF-2000 dispersion curve.

Fig. 4. Measured (blue line) and calculated (red dots) optical spectra at the DCF output for different pumping powers. Spectra between 1800–1920 nm are affected by water absorption lines.

Fig. 5. Average output power of the frequency-shifted soliton (filtered from the entire spectrum) at different central wavelengths.

Fig. 6. Measured pulse autocorrelations of the frequency-shifted solitons at different central wavelengths from 1700 to 2100 nm.

Fig. 7. Comparison between the (a) optical spectrum and (b) pulse duration of the soliton centered at 2050 nm before and after the DCF-2000 fiber.