A dual-core photonic crystal fiber coupler based on the heavily G e O 2 -doped-silica-air cladding and composite-liquid ( C S 2 and C 2 C l 4 ) core is proposed to obtain the saturable absorber (SA). It is demonstrated by numerical simulations that the SA with appropriate parameters can exhibit the normal dispersion, high nonlinearity, and flat profile of the linear coupling lengths in the wavelength range from 1500 to 2000 nm. The input pulses with durations > --> 2 p s exhibit relatively high transmissions and low saturable powers mainly because of the strong effect of stimulated Raman scattering in the SA. Consequently, the SA with the G e O 2 concentration ratio of 80 mol% can be employed in both the erbium- and thulium-doped fiber mode-locked lasers with all-normal or large net-normal dispersion. The dissipative soliton pulses with tunable wavelengths can be obtained in both cases.