Robust Design for Reconfigurable Coder/Decoders to Protect Against Eavesdropping in Spectral Amplitude Coding Optical CDMA Networks

This paper presents an enhanced security mechanism to protect spectral-amplitude-coding optical code-division multiple-access networks against eavesdropping. This study proposes an alternative to huge code-space size techniques such as wavelength hopping/time spreading or spectral-phase coding for network protection against eavesdropping by exploiting the cyclic properties of arrayed-waveguide-grating routers and maximal-length sequence code (M-sequence code). In addition, the network is protected using a dynamic reconfigurable coding/decoding scheme based on optical switches and a dynamic code matrix assignment scheme implemented using simple electrical shift registers. The signal-to-beat noise ratio is evaluated for various data bit rates to provide an indication of the confidentiality of the power level for a specified bit error rate (P_e<10^-9). To further verify the effectiveness of the proposed scheme, this paper investigates a weighted load balance problem based on the power distribution of each transmitted wavelength under various eavesdropping abilities. A dynamic codeword modification is proposed which identifies the code matrix assignment that minimizes the degree of weighted load balance (DWLB). The evaluation results show that the reconfiguration policy outperforms one class of static policies in terms of two performance metrics, namely, the DWLB and the number of register shifts required to reconfigure the code matrix assignment.