A simple, robust method for real time monitoring of Bragg reflector layer thickness is described. The method is based on the choice of the appropriate ellipsometric measurement wavelength to control the deposition of the top layer. This method requires no information on the underlying structure. To evaluate the method, Bragg reflectors were developed with SiO2 and SiNx stacks grown by electron cyclotron resonance plasma chemical vapor deposition. Reflectivity measurements performed on these reflectors confirm the reproducibility and accuracy of the method.