The principle and performance of optical stealth communication technique is summarized and its applications to smart sensor networks are proposed. Optical stealth communication, which is also known as optical steganography, hides information in wide band analog noise. The wide band and fast changing noise protects the stealth information from being detected and recorded by an eavesdropper. If the matching condition cannot be achieved when receiving the stealth information, the information is permanently lost and cannot be recovered by post-processing techniques. The optical stealth communication technique is proposed to protect the sensing information in smart sensor networks. Private information in both the fronthaul connections and the communications between the sensor nodes and the wireless stations can be hidden in the optical stealth communication channels.