Linear and nonlinear optical susceptibilities of poled guest-host polymer systems are calculated, using structures simulated by molecular dynamics. Three systems are investigated, each consisting of a poly(methyl methacrylate) (PMMA) matrix and doped with either of the one-dimensional nonlinear optical (NLO) chromophores N,N-dimethyl p-nitroaniline (DPNA) and 4-(dimethylamino)-4'-nitrosilbene (DMANS) or the two-dimensional NLO chromophore N,N'-di-n-propyl-1,5-diamino-2,4-dinitrobenzene (DPDADNB). The electrical properties of the NLO chromophores are computed at the ab initio level, including correlation at the second-order Moller-Plesset (MP2) theory and frequency dispersion at the restricted Hartree-Fock (RHF) level, and with density functional theory (DFT). The permanent local fields in the bulk are small; however, their effects on the first hyperpolarizabilities are comparably large. Refractive indices and second-order susceptibilities corresponding to second harmonic generation (SHG) are calculated using a rigorous local-field (RLF) approach. The system DPNA/PMMA is well-described by the single point-dipole approach, whereas for DPDADNB/PMMA and DMANS/PMMA, only distributed molecular response models yield reasonable results. The Lorentz local field approximation, modified to take partial poling order into consideration, is shown to be approximately consistent with both the experimental results and those of the RLF approach.