One of the challenging real-world problems in the communication network is to secure the communication system that deals with a large data. Perhaps even a more challenging version of this scenario is when the channel that transmits the information is a wireless media. This thesis introduces a steganography technique to secure the physical layer of the communication system. It enhances the benefits by using optical communication rather than radio frequency (RF) communication, especially in terms of transmitting a large scale of data. This thesis demonstrates that we can transmit secure large information in free space (air) using steganography mechanism and free space optical (FSO) channel. In this work, we built a secure optical wireless communication prototype. We analyzed the performance of this system using eye diagram and bit-error rate (BER) measurements. The application of this work can be used in many applications such as monitoring enterprise and campus connectivity, smart sensors and internet of things networks.