The polycycloaddition of azomethine ylides to dipolarophiles is described for the first time. Use of (cis,cis)-bis-aziridines as a source of azomethine ylides allows selective polyaddition to be realized, which leads to oligomers exclusively with trans-substituted pyrrolidine rings and modest molecular weights (ca. 5–10 kDa). The fluorescent, electrochemical, electrochromic, and non-linear optical properties of the main-chain free-base porphyrin oligomer, synthesized by the developed procedure, are studied. An enhancement of the optical power limiting effect in a porphyrin oligomer solution is registered against that of the monomer.