A computer program stored on a computer readable storage medium for carrying out a method for calculating a bandwidth of a laser source and a multimode fiber optic cable, wherein the method accounts for both modal and chromatic dispersion effects within the multimode fiber optic cable, the method comprising: measuring temporal responses of the multimode fiber optic cable, U(r,t), using spectrally narrow and temporally short pulses of light, R( t), with a central wavelength, λ c, injected into a core of the multimode fiber optic cable at series of radial offsets, r from the core; computing a plurality of fiber chromatic dispersion transfer functions, H cd (f,r); computing temporal responses of the multimode fiber optic cable, U cd (r,t) after effects of chromatic dispersion by first convolving a Fourier Transform of the temporal responses of the multimode fiber optic cable with the plurality of fiber chromatic dispersion transfer functions and then taking an inverse Fourier Transform of the convolution to convert the temporal responses of the multimode fiber optic cable back to time domain; computing chromatically dispersed weighted responses of the multimode fiber optic cable, D cd (r,t,n), with n DMD weighting functions, W(r,n); computing a chromatically dispersed resultant output pulse, P cd (t,n), by summing the weighted response, U cd (r,t) across all radii, r; computing a total fiber transfer function, H fiber (f,n), and a total calculated bandwidth, CB(n), the total fiber transfer function, H fiber (f,n), being by deconvolving the injected pulse, R(t), from the output pulse, P cd (t,n), according to: H fiber f, n = FT P cd t / n / FT R t and outputting the total calculated bandwidth, CB(n) which was computed using the plurality of fiber chromatic dispersion transfer functions, H cd (f,r), on a display. measuring temporal responses of the multimode fiber optic cable, U(r,t), using spectrally narrow and temporally short pulses of light, R( t), with a central wavelength, λ c, injected into a core of the multimode fiber optic cable at series of radial offsets, r from the core; computing a plurality of fiber chromatic dispersion transfer functions, H cd (f,r); computing temporal responses of the multimode fiber optic cable, U cd (r,t) after effects of chromatic dispersion by first convolving a Fourier Transform of the temporal responses of the multimode fiber optic cable with the plurality of fiber chromatic dispersion transfer functions and then taking an inverse Fourier Transform of the convolution to convert the temporal responses of the multimode fiber optic cable back to time domain; computing chromatically dispersed weighted responses of the multimode fiber optic cable, D cd (r,t,n), with n DMD weighting functions, W(r,n); computing a chromatically dispersed resultant output pulse, P cd (t,n), by summing the weighted response, U cd (r,t) across all radii, r; computing a total fiber transfer function, H fiber (f,n), and a total calculated bandwidth, CB(n), the total fiber transfer function, H fiber (f,n), being by deconvolving the injected pulse, R(t), from the output pulse, P cd (t,n), according to: H fiber f, n = FT P cd t / n / FT R t and outputting the total calculated bandwidth, CB(n) which was computed using the plurality of fiber chromatic dispersion transfer functions, H cd (f,r), on a display.