Impact Of Four Wave Mixing On FSK DWDM System

AS DWDM technology develops, nonlinearity of fibers shows more and more badly influence on its transmission properties. Quantitative analysis of nonlinear effect in DWDM system is of great significance. In recent years, FSK becomes a hot research area in optical transmission technology by virtue of its high receiver sensitivity, high tolerance for nonlinearity of fibers and the advantage in optical label switching. This paper will study one kind of the nonlinear effects, four wave mixing effect in FSK DWDM system, the main content and research results are as follows:(1) Ignoring dispersion-managed, a calculation model applied to evaluate the variance of nondegenerate FWM noise for DWDM system is deduced by spectrum analysis theory. The model is based on FSK modulation and the launched pulses are assumed to be chirped Gaussian pulses. Walk-off effect between channels and random bit sequence in each channel is included. Then Matlab is used to calculate the standard deviation of four-wave mixing noise, influence of multiple channels to the detection channel is included. The results of calculation show that, the optimal value of modulation deviation frequency can reduce four wave mixing effect in DWDM system. The value of characteristic width will not affect the selection of the optimal value.(2) Considering dispersion-managed, with a similar derivation presented in (1), a calculation model applied to evaluate the variance of degenerate and nondegenerate FWM noise for dispersion and loss-managed DWDM system is deduced. Walk-off effect between channels and random bit sequence in each channel is included. The model is based on FSK modulation and the launched pulses are assumed to be chirped Gaussian pulses.(3) Matlab is used to calculate the standard deviation of four-wave mixing noise in (2). Influence of multiple channels to the detection channel is included. The results of calculation show that, smaller four wave mixing noise standard deviation can be obtained when modulation deviation frequency and local dispersion coefficient absolute value take optimal values.