Structuring waveguide-grating routers with post-switching coding to secure optical CDMA network access

Optical code-division multiple-access (OCDMA) technique has been considered as a good candidate to provide optical layer security and regards as an important benefit to the enhanced security. In this paper, an enhanced security mechanism is structured over spectral-amplitude coding (SAC) scheme of OCDMA network coder/decoders (codecs). The network security is obtained through pseudo-noise (PN) type of shift register (SR) state switching to combat with eavesdropping. We construct the dynamic reconfigurable codec over arrayed-waveguide gratings (AWGs) by utilizing the cyclic properties of AWG routers and maximal-length sequence (M-sequence) codes. Signature code unique to each OCDMA network user is reconfigured in accordance with the memory cell state of the controlling electrical shift registers. Examples for both network user and eavesdropper are numerically illustrated. It is shown that, the eavesdroppers cannot accurately detect the cell-shift values of the shift register when the scheme is triggered. The proposed scheme thus makes the probability of achieving a correct detection result for the eavesdroppers become much lower. The degree of OCDMA network confidentiality is hence largely improved.