Influence of the spectrum width of a nonmonochromatic radiation source on blurring of ultrashort optical pulses in telecommunication single-mode optical fiber waveguides

We consider the influence of the spectrum width of a nonmonochromatic radiation source on blurring of ultrashort optical pulses when they propagate through single-mode optical telecommunication waveguides with very weak linear birefringence. This pulse widening is due to the presence of random irregularities of the dielectric permittivity tensor in such waveguides. The latter effect, in turn, influences the polarization mode dispersion of the radiation. The numerical simulation method was used to find the dependences of the envelope evolution of ultrashort optical pulses and their frequency spectra on the length of the single-mode optical fiber waveguide with random irregularities. It is shown that the pulse duration increases obeying the diffusion law, i.e., in proportion to the square root of the fiber length, and the proportionality coefficient depends significantly on the width of the frequency spectrum of the radiation source. The pulse duration is shown to increase with increasing length of the single-mode optical fiber waveguide significantly faster for the radiation source with a wider frequency spectrum, and the influence of the width of the spectral line of the source becomes noticeable when it is equal to the inverse pulse duration.