An improved model for estimating the impact of FWM in coherent optical systems

• An accurate analytical FWM model for coherent optical systems is proposed.
• This model can be used both in uncompensated and dispersion managed systems.
• The FWM accumulation between the spans seems to be rather incoherent than coherent.
• The inaccuracy of the model is less than 1 dB in almost any of the examined points.
• This model calculates the optimum channel power with a mismatch of less than 0.2 dB.

Four Wave Mixing is the main source of nonlinearity in coherent optical OFDM systems that degrades the system performance. In this paper, based on a previously introduced model, we derive a closed form expression that calculates the FWM power. This model can be used for a fast estimation of system performance within a broad range of system parameters and/or can be also used as an integral part of physical layer aware algorithms. The proposed model is in very good agreement with the exact model as well as with numerical results and provides significant lower mismatch than the previously published model. Moreover, this expression is also expanded in Nyquist-WDM systems showing very good accuracy with numerical results while is modified to take into account dispersion compensation, something that was neglected in the previous work.