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分析了光栅色散抖动对有线电视信号的影响 ,估计出落在信号 5 0MHz～ 5 5 0MHz范围内互调产物功率约占所有互调产物功率的 10 %～ 5 0 %。为了抑制色散抖动幅度 ,光栅的折射率变化应该从初值零渐渐升到最大值。长度为 10cm、包络为升余弦与tanh(4z)的光栅都能满足有线电视系统的要求。此外还发现 ,长光栅对应的抖动周期小 ,因此对信号的影响也小 ;具有升余弦包络的光栅比tanh(4z)光栅更能有效地抑制色散抖动。
The influence of grating dispersion jitter on CATV signals is analyzed. It is estimated that the power of intermodulation products falling within the range of 50 MHz to 550 MHz is about 10% ~ 50% of the power of all intermodulation products. In order to suppress the amplitude of dispersion jitters, the refractive index of the grating should gradually change from the initial zero to the maximum. The length of 10cm, the envelope as raised cosine and tanh (4z) grating can meet the requirements of cable systems. In addition, it is also found that the long grating corresponds to a small period of jitter and thus has a small influence on the signal. The grating with a raised cosine envelope is more effective in suppressing the dispersion jitter than the tanh (4z) grating.