If a standard room is considered , the infra-red radiation is stopped (reflected or absorbed) by the walls. On the other hand, a part of this radiation can escape through the openings: glazing, open doors. Numerical simulations make it possible to study the light propagation in the room [Sizun 2002]. We wish to indicate some orientations of search that allow us to find solutions to limit or prohibit the escape of the photonic component of the communication through the windows . In particular, our work concerns the choice of the materials which constitute the windows and the wall lining .
The securisation of the openings can be made in various ways, principally while cutting the communication at the time of the opening of the doors: it is an effective and radical means but which we will not retain for this study. The other method consists in determining the optical properties of the walls and the glazing which will minimise the stray reflections which would result in an escape of light through openings when the doors are open. The confidentiality level can be affected by the furniture arrangement in the room. In our simulation, we will suppose that confidentiality is assured by the materials consisting the walls.
The securisation of the glazing is to be taken into account. Indeed, the glazed surface of the room can represent a surface higher than that of one of the walls. Under these conditions, it is necessary to find glazing which have the property to let pass all the light of the visible spectral, in order to ensure first visual comfort and second to reflect the signals of the wavelength chosen for the communications, here: 1,55 ¼ m.