SE HA EMPLEADO EL MÉTODO DE PROPAGACIÓN DE HACES POR LA TRANSFORMADA RÁPIDA DE FOURIER PARA SIMULAR LA PROPAGACIÓN DE LA LUZ EN GUÍAS DE ONDA DE ÍNDICE DE GRADIENTE. ÉSTAS HAN SIDO FABRICADAS POR DIFUSIÓN DE IONES DE COBRE EN ESTADO SÓLIDO EN SUBSTRATOS DE VIDRIOS SÓDICO-CÁLCICOS. SE HAN SIMULADO DOS CASOS; EL PRIMERO, EL PERFIL DE LUZ DE ENTRADA, QUE ES GAUSSIANO, ES COLINEAL CENTRAO A CENTRO RESPECTO AL CENTRO DE LA GUÍA DE ONDAS; EL SEGUNDO, SE HA DADO UN PEQUEÑO CORRIMIENTO LATERAL Y UNA INCLINACIÓN ANGULAR. COMO CONSECUENCIA DE LOS CASOS ANTERIORES SE HA OBSERVADO EFECTOS DE BATIMIENTO MODAL. LOS RESULTADOS DE LA SIMULACIÓN SE HAN VALIDADO CON RESULTADOS EXPERIMENTALES.AbstractWE EMPLOYED THE FAST FOURIER TRANSFORM BEAM PROPAGATION METHOD TO SIMULATE THE PROPAGATION OF LIGHT IN GRADED INDEX CHANNEL WAVEGUIDES, THESE HAVE BEEN OBTAINED BY SOLID STATE DIFFUSION OF COPPER IONS IN SODA-LIME GLASS SUBSTRATES. LONGITUDINAL PROPAGATION HAS BEEN SIMULATED, THE INPUT LIGHT BEAM HAS A GAUSSIAN PROFILE. TWO CASES HAVE BEEN ANALYZED, IN THE FIRST, THE GAUSSIAN BEAM IS COLINEAR CENTER TO CENTER TO WITH RESPECT TO WAVEGUIDE; IN THE SECOND, A SMALL LATERAL OFFSET AND ANGULAR TILT HAVE BEEN INTRODUCED. MODAL BEATING AND BENDING EFFECTS HAVE BEEN FOUNDED. WE HAVE PROVEN THA VALIDITY OF OUR NUMERICAL RESULTS IN DETAILED COMPARISON WITH EXPERIMENTAL DATA.EMPLOYED THE FAST FOURIER TRANSFORM BEAM PROPAGATION METHOD TO SIMULATE THE PROPAGATION OF LIGHT IN GRADED INDEX CHANNEL WAVEGUIDES, THESE HAVE BEEN OBTAINED BY SOLID STATE DIFFUSION OF COPPER IONS IN SODA-LIME GLASS SUBSTRATES. LONGITUDINAL PROPAGATION HAS BEEN SIMULATED, THE INPUT LIGHT BEAM HAS A GAUSSIAN PROFILE. TWO CASES HAVE BEEN ANALYZED, IN THE FIRST, THE GAUSSIAN BEAM IS COLINEAR CENTER TO CENTER TO WITH RESPECT TO WAVEGUIDE; IN THE SECOND, A SMALL LATERAL OFFSET AND ANGULAR TILT HAVE BEEN INTRODUCED. MODAL BEATING AND BENDING EFFECTS HAVE BEEN FOUNDED. WE HAVE PROVEN THA VALIDITY OF OUR NUMERICAL RESULTS IN DETAILED COMPARISON WITH EXPERIMENTAL DATA.GR