中文说明：
利用牛顿法数值计算光纤的传播常数，这样利用传播常数与色散的关系，就可以画出光纤的色散曲线
English Description：
The propagation constant of optical fiber is numerically calculated by Newton method. In this way, the dispersion curve of optical fiber can be drawn by using the relationship between propagation constant and dispersion