Code-selective RF photonic mixing for use in optical CDMA demultiplexers

We demonstrate a technique that coherently frequency shifts a direct sequence encoded optical channel by mixing it with an identically encoded RF local oscillator in a dual-electrode Mach Zehnder modulator (DE-MZM). The spectral separation would reduce the effects of cumulative shot noise and speckle, and full code orthogonality is possible since the bipolar nature of the optical field is recognized by the frequency shifting process.