Holographic Diffusers for Indoor Infrared Communication Systems

Diffused infrared transmission is one of the preferred techniques used in indoor wireless communications. Tolerance to shadowing and a lack of alignment requirements are among the many advantages offered by this technique compared to the line-of-sight techniques. However, it has its disadvantages, namely high path loss and multipath dispersion. The limitation imposed by eye-safety requirements restricts the transmitted power. Therefore, efficient use of transmitted optical power is the key for practical broadband infrared systems. In this paper, we report on using a holographic diffuser for shaping of infrared radiation pattern in an indoor infrared transmission system. The holographic diffusers have the advantage of light weight and added flexibility in the system design. The reported measurements show that employing a properly designed holographic diffuser can reduce the path loss of a nondirected optical link. The results also show another advantage of using the proposed holographic diffuser, which is additional tolerance of the transmission to shadowing.