叠加训练序列的最小二乘信道估计与最小均方误差均衡，QPSK调制，做了4次迭代估计的性能对比。-superimposed training, least squares (LS) channel estimation, MMSE equalizer, QPSK modulation, 4 times iteration.

通过迭代的方法来计算物质的光学性质，通过最小二乘法来设置收敛的条件，当结果小于收敛条件时，输出结果-Calculate liquid refractive index, using the iteration method, design the smallest error by the least squares method, to terminate the iteration convergence