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采用聚焦法测量光纤预制棒折射率分布时,无法直接得到折射率分布曲线,只能测得光强分布曲线p(y)这一间接数据。再由定积分公式t(y)=integral from n=0 to y p(y)dy算出t(y),最后由以下定积分公式算出所需的折射率分布差n(r)-n_0: n(r)-n_0=n_0/(πaL)integral from n=r to a (t-y(t))/((t~2-r~2)(1/2))dt 因此,没有计算机就无法进行光纤预制棒测试。为使AppleII微机完成上述运算,首先利用宰普生(simpson)数值积分近似方法给出数学模型。该方法具有收敛速度为线性、可利用递推公式等特点。其次根据数学模型制定相应程序,最后编制打印格式和绘图程序。
When using the focusing method to measure the refractive index distribution of optical fiber preform, it is impossible to directly obtain the refractive index distribution curve, and only the indirect data of light intensity distribution curve p (y) can be measured. Then the t (y) is calculated from the definite integral formula t (y) = integral from n = 0 to yp (y) dy, and finally the required refractive index distribution difference n (r) -n_0 is calculated by the following definite integral formula: Therefore, the optical fiber can not be prefabricated without a computer Stick test. In order for the Apple II microcomputer to complete the above calculation, the mathematical model is first given by a simpson numerical integral approximation method. The method has the characteristics of linear convergence rate and recursive formula. Followed by the mathematical model to develop the corresponding procedures, the final preparation of the print format and drawing procedures.