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. 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 reported measurements show that the path loss of a non-directed optical link can be reduced by employing a properly designed holographic diffuser. The results also show another advantage of using the proposed holographic diffuser which is the added tolerance (robustness) of the transmission to shadowing