FWM behavior in 2-D time-spreading wavelength-hopping OCDMA systems

A new formula for the signal-to-four-wave mixing (FWM) crosstalk in 2-D time-spreading wavelength-hopping (TW) optical code division multiple access (OCDMA) systems is derived. The influence of several system parameters on the signal-to-FWM crosstalk ratio (SXR) is analyzed, including transmitted power per chip, code length, the number of active users, code weight, wavelength spacing, and transmission distance. Furthermore, for the first time, a closed-form expression for the total number of possible FWM products employing symmetric TW codes with equal wavelength spacing is investigated. The results show that SXR is sensitive to minor variations in system parameters, especially the launched power level and the code length while the wavelength spacing has a less impact on the level of the generated FWM power.