Ultrashort Pulses Amplification In Er-Yb Composite Fiber

A comparison of ultrashort pulses with a central radiation wavelength of $1.53\ \mu \mathrm{m}$ amplification in standard silica-based and composite active fibers was made. We have shown that pulse shape distortion in a composite fiber with Er/Yb co-doped phosphate glass core and silica cladding occurs at large values of the signal gain coefficient.