Fig. 1. Experimental setup. DCF, dispersion compensated fiber; TDFL, thulium-doped fiber laser; TDFA, thulium-doped fiber amplifier; SMF, single-mode fiber; GCF, germania core fiber.

Fig. 2. Characteristics of seed pulses. (a) Measured spectra of mode-locked output and after DCF. (b) Autocorrelation trace. (c) Temporal profile after DCF.

Fig. 3. Dispersion and loss profiles of GCF and silica. Inset shows cross profile of GCF. ZDW, zero dispersion wavelength.

Fig. 4. Spectral comparison at different positions.

Fig. 5. Spectral evolutions of SC laser measured after GCF.

Fig. 6. Power evolution of SC laser at different positions with respect to pump power of TDFA2.