A diffusion process controlled modelling of Titanium-indiffused Lithium Niobate (Ti: LiNbO3) channel waveguides (of μm dimension) for Mach-Zehnder Interferometer (MZI) switch has been presented. The effect of various indiffusion process parameters e.g. dopant strip thickness, lateral and vertical diffusion length on the insertion loss has been taken care of, to reduce the switch losses. Transition losses in the curved waveguides of the structure are also minimized by selecting low less bend structures to increase overall performance of the switch. The computed results for switch performance are in good agreement with the published data. © 2011 SPIE.