There has been an increased interest in enhancing the security of optical communications systems and networks. All-optical cryptography methods have been considered as an alternative to electronic data encryption. In this paper we propose and verify the use of a novel all-optical scheme based on cryptographic keys applied on the spectral signal for encryption of the M-QAM modulated data with bit rates of up to 200 gigabits per second.

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The ever-growing demand for optical network security can be addressed by data encryption at different network layers. In this work, we consider all-optical cryptography technique that applies a spectral phase change and delay encoding on spectrum slices of a specified WDM channel. In this case we have investigated a novel approach where signals are double encrypted to achieve an enhanced degree of security. Simulation results indicate that such double cyphering scheme can be applied to high data-rate M-QAM signals propagating in metro/regional networks.

We investigate the application of a new all-optical cryptography technique to wavelength division multiplexing (WDM)-compatible differential phase-shift keying (DPSK) signals. The technique uses current optical band-pass optical filters with narrow bandwidths to divide a given input WDM-compatible signal into several spectral slices, which are submitted to two cryptographic key stages. The first one impresses amplitude encoding, whereas the second imposes delay variations to each spectral slice. The technique performance is assessed by evaluating the encrypted and decrypted signals bit error rates. Computer simulations suggest that encrypted DPSK signals may be properly recovered even after being propagated through typical metropolitan area network distances. 1