We report that the Tm:Ho-doped fiber can be utilized to improve the frequency stabilization of the Er-doped fiber comb. This rare-earth doped fiber provides photon absorption at 1.2 microm and 1.7 microm wavelengths together with emission at wavelengths between 1.8 microm to 2.1 microm. This unique combination of the absorption and emission regions constructively redistributes the spectral power of the supercontinuum generated by a highly nonlinear fiber to detect the carrier-envelope-offset frequency (f(ceo)) via a self-referencing f-2f interferometer. As a result, the signal to noise (S/N) ratio of the detected f(ceo) signal increases by 10 dB, thereby increasing the potential of enhancing the long-term frequency stability of the fiber frequency comb.