Erbium-doped mode-locked fiber lasers emitting ultra-short pulses (USP) of pico- and femtosecond durations are well-elaborated commercially available devices offering great flexibility in design, regimes of operation and output characteristics . These sources usually referred to as frequency combs are widely employed in different fields of science and industry . However, many efforts have been already put on comb stabilization systems development [1,2] as well as understanding their potential stability limitations , while less activity is aimed to study fundamental principles standing for repetition (fr) and carrier-to-envelope offset (fceo) response behaviour upon different perturbations such as pump power or temperature variations. Recently, a theory of femtosecond frequency comb from an Erbium fiber laser has been proposed  identifying a number of physical mechanisms including spectral shift, third-order dispersion (TOD), resonant gain, self-steepening (SS) and chirp-assisted frequency dependent loss (FDL) responsible for pump-induced changes in pulse repetition frequency. In this work, we have shown for the first time a decisive contribution from Nonlinear Polarization Evolution (NPE) mode-locking mechanism to pump-induced repetition frequency response dynamics via frequency dependent loss term in the stretched-pulse Erbium-doped all-fiber ring oscillator with distributed polarizer.
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