Method for Modeling the Transmission of M-QAM Signals over a Fiber-Optic Path Using Optical OFDM Technology

A method for modeling the transmission of channel signals of the M-QAM modulation format using the CO-OFDM technology over a fiber-optic path operating in a nonlinear mode has been developed. Signal distortions at the receiving end for given parameters of the transmission system are modeled using the obtained normalized analytical expressions, and the signal quality indicator (Q factor) is calculated based on a statistical analysis of the signal and noise parameters. The model allows one to clearly represent the signal distortion in the constellation of signal points in the IQ diagram for given parameters of the transmission system. An example of modeling a system for transmitting an OFDM signal with a total rate of 4 Tbit s $${}^{-1}$$ over a standard single-mode optical fiber at 80, 160, and 240 km is given. Optimum optical signal power levels of $${+}5.5$$ , $${+}4$$ , and $${+}2.5$$ dBm are found to achieve the maximum signal quality indicator at such transmission distances.