Demonstration of Stealthy and Encrypted Optical Transmission Below Adjacent 50 GHz DWDM Channels

A stealthy and encrypted transmission is demonstrated in a dense-WDM network. The residual gap between two neighboring commercial channels is utilized for the transmission of the secured channel, hidden below the amplifier noise at negative −10 dB/0.1nm OSNR. The stealthy and encrypted channel is generated by a digital replication of the baseband signal together with a digital spectral phase mask. This technique provides encryption and steganography as it exclusively allows the eligible user to obtain a considerable processing-gain, and to recover extremely low OSNR signals. In this work the secured channel is explored under stringent network conditions. A stealth transmission was tested between two high OSNR public channels, separated 50 GHz apart: Unshaped 25 Gbps NRZ channel and digitally shaped coherent PM-QPSK 112 Gbps channel. Although it is significantly overlapped by adjacent channels and covered by the ASE noise, we demonstrate error-free detection of the secured channel, without significant effect on the commercial channels.