The paper presents a recursive method for evaluating the impulse response of indoor free-space optical channels with Lambertian reflectors, accounting for multiple reflections of any order. This method enables accurate analysis of multipath dispersion effects on high-speed indoor optical communication systems. The authors describe the implementation of the technique and present computer simulation results for both line-of-sight and diffuse transmitter configurations. They find that multiple-order reflections are significant sources of intersymbol interference (ISI). Experimental measurements of optical multipath are also reported to verify the accuracy of the simulations. The results highlight the impact of multipath dispersion on system design, particularly in terms of power penalty and bandwidth. The study concludes that careful consideration of multipath response is essential for the design of high-speed indoor communication links using infrared.The paper presents a recursive method for evaluating the impulse response of indoor free-space optical channels with Lambertian reflectors, accounting for multiple reflections of any order. This method enables accurate analysis of multipath dispersion effects on high-speed indoor optical communication systems. The authors describe the implementation of the technique and present computer simulation results for both line-of-sight and diffuse transmitter configurations. They find that multiple-order reflections are significant sources of intersymbol interference (ISI). Experimental measurements of optical multipath are also reported to verify the accuracy of the simulations. The results highlight the impact of multipath dispersion on system design, particularly in terms of power penalty and bandwidth. The study concludes that careful consideration of multipath response is essential for the design of high-speed indoor communication links using infrared.