用于产生的相位噪声的源码，绘制ber曲线-add_phase_noise.m ,generate phasenoise

用速率方程，数值计算SG-DBR半导体激光器和Y-Branch激光器的相位噪声，并将结果与理论公式对比，结果符合良好。(By using the rate equation, the relative intensity noise and phase noise of the ordinary single mode semiconductor laser are calculated, and the results are compared with the theoretical for