A new all-optical cryptography technique applied to WDM-compatible DPSK signals

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.