INFLUENCE OF NONLINEAR PHASE NOISE ON QPSK AND M-QAM SIGNALS IN COHERENT OFDM FIBER OPTIC TRANSMISSION SYSTEMS
V.A. Vardanyan
Siberian State University of Telecommunications and Information Science, Novosibirsk, Russia
Keywords: fiber optic transmission systems, QPSK, M-QAM, OFDM, self-phase modulation (SPM), cross-phase modulation (XPM), Q-factor
Abstract
A coherent fiber optic transmission system for OFDM signals is considered. The channels are formed using spectrally efficient modulation formats - QPSK and M-QAM. It is shown that the nonlinear phase noise arising in the optical path is converted into the amplitude noise and, after mixing with the noise of optical amplifiers, leads to a decrease in the signal quality index. Evaluation formulas are given for determining the noise immunity of channel signals using the Q-factor.
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