No abstract

Optical networks are fast, robust and error free, however, there are nonlinear obstacles preventing from being perfect media. The performance of wavelength division multiplexing (WDM) in radio over fiber (RoF) systems is found to be strongly influenced by nonlinearity characteristics inside the fiber. The effect of four wave mixing (FWM) as one of the influential factors in the WDM for RoF. From the results obtained, it is found that the FWM effects have become significant at high optical power levels and have become even more significant when the capacity of the optical transmission line is increased, which has been done by either increasing the channel bit rate, and decreasing the channel spacing, or by the combination of both process. It is found that when the channel spacing is 0.1 nm, 0.2 nm and 0.5 nm the FWM power is respectively, becomes about -59 dBm, -61 dBm and -79 dBm. The simulation results obtained here are in reasonable agreement as compared with other numerical simulation results obtained, elsewhere, using different simulation tools.

Recent coherent optical communication systems address modulation and detection techniques for high spectral efficiency and robustness against transmission impairments. This paper demonstrates the generation and transmission of beyond 400Gb/s transmission system over the standard 50GHz ITU-T grid at a net spectral efficiency of 8.4b/s/Hz. Coherent detection employing QAM modulation formats along with DSP algorithm have become one of the most promising technologies for next generation high speed transmission systems due to the high power and spectral efficiencies. This paper shows that, the use of near ideal Nyquist pulse shaping, spectrally-efficient high-order modulation format, and distributed Raman amplification, coherent equalization may enable us to operate future 400G systems over the standard 50GHz-grid optical network. Keywords-Wave length division multiplexing (WDM); coherent detection; digital signal processing (DSP); QAM; Nyquist pulse.I.