Signatures reconfigurations over waveguide-gratings-based optical CDMA network codecs

To combat with multiple-users interference and malicious eavesdropping, this talk presents a double signatures scrambling scheme over wavelength/time for a cryptographic optical code-division multiple-access (OCDMA) network data transmissions. Optical switches and fiber delay lines are placed with arrayed-waveguide grating (AWG) coder/decoders (codecs) to realize wavelength-spreading and time-hopping. On the transmitter side, user data bits are sliced into spectral chips, coded into pseudo-noise (PN) signature codes, and conducted with different PN-code units of time-delay. In the receiver side, complementary delay lines first reverse the summed spectral chips back into the same time basis, then optical switches follow the associated signatures to turn on-off spectral chips into balanced detector for the final data decoding. By changing signature codes frequently, the eavesdroppers cannot catch on the changing code speed and have little chance to detect the channel waveform to solve the code. With such wavelength/time scrambling scheme, data transmission reliability in OCDMA network can be greatly enhanced.