Secure Optical Communication Using Chaos

In this paper we demonstrate a way to secure optical communication. Chaos as a tool for information security is gaining wide acceptance for its inherent simplicity and ability to secure a communication link from the physical layer compared to other application layer-software encryption methods. Though they are lesser secured than the physical layer systems, the software techniques are still the order of the day. Since the physical layer techniques are still in the nascent stages of growth, this paper tries to go one step further, to utilise the chaotic scheme in securing optical communication. The idea is to generate a chaotic signal in the form of current and adding it to the message at the transmitter where the whole of this current drives an optical source-laser. At the receiver the same chaos signal is generated by prior synchronization. The received signal is photodetected to get the equivalent current. The difference between this current and the internally generated matched chaos yields the message. The efficiency of this technique is investigated for line of sight communication by modelling a free space optic channel (FSO) and accounting for attenuation caused by the same.