A method for studying the temperature dependence of the effective refractive index of optical waveguides was proposed and tested. The samples were heated using a Peltier thermo-optic module. This technique is simple and easy and improves the measurement accuracy and capabilities of temperature studies of optical waveguides and the materials from which they are made. Obtained dependences can be used to determine the thermo-optic coefficient of film materials. The method was tested on optical waveguides using SiO2-TiO2 films produced by sol-gel technology. © 2013 Allerton Press, Inc.