In this paper, we propose an optical transmission system of 128 quadrature amplitude\nmodulation for dense wavelength division multiplexing. In such a system, Gaussian optical\nfiltering is used to get an appropriate photonic carrier. Theoretical analysis and simulation\ncomputation show that the modulated multi-carrier photonic signals with the wavelength spacing\nof 0.7 nm can transmit for over 80 km with the standard single mode fiber. Using digital signal\nprocessing algorithms to compensate the transmission impairments, the transmission rate of the\nsingle-carrier photonic signal can reach up to 904 Gbps and the spectral efficiency of the\ntransmission can reach up to 10.33 bps/Hz. When this technology is applied to a dense wavelength\ndivision multiplexing system with N channels, the huge message capacity of N Ã? 904 Gbps can be\nrealized. Furthermore, we find that the bit error rate and the error vector magnitude are similarly\ninfluenced by the optical signal-to-noise ratio and the bandwidth of the Gaussian optical filter. The\ninfluence presents mostly a synchronization trend with the change of the optical signal-to-noise\nratio and the bandwidth of Gaussian optical filter.
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