The nonlinear Fourier transform (NFT) can be utilized to characterize pulses in fiber lasers. For chirp-free sech pulse, NFT works great. However, the presence of chirp significantly affects the reliability of NFT characterization. By modifying the NFT methodology, we demonstrate its applicability for characterizing chirped pulses in dispersion-managed fiber lasers. Numerical simulations reveal that the modified NFT approach effectively captures the pulse dynamics within dispersion-managed cavities. The discrete spectral energy of the recovered solitons can be used to evaluate the credibility of the modified NFT.