The purpose of the paper is to study the synthetic effects of the negative quintic nonlinearity of optical fibers and the initial frequency chirps of optical pulses on the frequency chirps and spectra of Gaussian optical pulses. Utilizing the extended nonlinear Schr dinger equation including quintic nonlinearity and neglecting the chromatic dispersion of optical fibers

the frequency spectra and the whole chirps of chirped Gaussian optical pulses are calculated and analyzed. The results show that

when the pulses are initially unchirped

the negative quintic nonlinearity can make the shapes of chirps change from single ‘S’ to dual ‘S’shape and even make the chirps in the central regions of pulses change from positive to negative. In addition

the negative quintic nonlinearity can also make the effects of initial chirps on spectra of pulses change considerably. After overlapping with the chirps caused by nonlinearity

the initial chirps can greatly influence on the energy distribution among the spectral peaks while slightly influence on the number of peaks. For some values of maximum nonlinear phase shifts

it may even occur that

the decrease of the whole chirps makes the number of spectral peaks increase. This investigation will contribute theoretically to the deep development of the optical switching

pulse compression

optical fiber communications

and so on

to some degrees.