We propose and analyze a novel (to our knowledge) approach to implement the spectral self-imaging effect of optical frequency combs. The technique is based on time-domain multilevel phase-only modulation of a periodic optical pulse train. The method admits both infinite- and finite-duration periodic pulse sequences. We show that the fractional spectral self-imaging effect allows one to reduce by an integer factor the comb frequency spacing. Numerical simulation results support our theoretical analysis. © 2011 Optical Society of America. ; Generalitat Valenciana [GV/2009/044] ; Vicerrectorado de Investigacion, Universidad Politecnica de Valencia [PAID-06-08/3276] ; Ministerio de Ciencia e Innovacion of Spain [TEC2007-68065-C03-02] ; Ministerio de Ciencia e Innovacion [BES-2006-12066] ; Caraquitena Sales, J.; Marta Beltrán; Roberto Llorente; Martí Sendra, J.; Muriel, MA. (2011). Spectral self-imaging effect by time-domain multilevel phase modulation of a periodic pulse train. OPTICS LETTERS. 36(6):858-860. doi:10.1364/OL.36.000858. ; Senia ; 858 ; 860 ; 36 ; 6