DOUBLE SECURITY LEVEL IN A TELECOMMUNICATION SYSTEM BASED ON PHASE CODING AND FALSE DATA-TRANSMISSION

A new communication system exhibiting a double security level is demon strated. Information coding is based on relative phase changes between consecutive time intervals of the light emitted from a highly coheren t CW source. An imbalanced Mach-Zehnder interferometer whose time dela y matches the intervals duration is used to decode the data. The first security level is related to the constant optical power in the transm ission link. To further enhance the security, a low coherent source is used to send false data down the transmission link. Common mode rejec tion is used to separate the real signal from the false signal. This s ystem provides a high signal-to-noise ratio as well as a low crosstalk in a wavelength division multiplexing network.