Optical CDMA Code Wavelength Conversion Using PPLN to Improve Transmission Security

We demonstrate optical code-division multiple access (OCDMA) code conversion in the wavelength domain using periodically poled LiNbO₃ for enhanced transmission security. The number of possible OCDMA codes in the channel is greatly increased and randomized dynamic code conversion is feasible, thus making it more difficult for an eavesdropper to intercept and decode the code. A 2.5-dB power penalty is reported at a bit-error rate of 10^-9 after two back-to-back wavelength conversions.