Material characterisation for optical wireless communication combining measurement and Monte Carlo simulations

A method is proposed for optical characterisation of materials, which is a very important input for realistic channel simulation based on Monte-Carlo Ray-Tracing algorithms. This original approach consists first of all in carrying out some measurements of the optical power received after propagation in the environment containing the materials sought, using a simple and low-cost experimental setup. In a second step, this approach is based on an optimization algorithm. It takes as input the optical power measurements made, associated with the parameters of the measurement environment, such as the positions or properties of the sensors. This algorithm searches for the parameters of the material reflection models, minimising the difference between the optical measurement and the simulation. Two cost functions are studied to perform this search and showed that the correlation measure is the more robust one. To avoid uncertainties in the real input data, this approach is discussed using only a virtual configuration with well-controlled input data and thus a virtual measurement obtained by simulation. The results show that this method produces a correct estimate of the Bidirectional Reflectance Distribution Function (BRDF) albedos, provided that the chosen BRDF models correspond well to the reflection behaviour of the materials, and that the materials have a significant influence on the measured optical power.