激光器的弛豫振荡带来的强度噪声对分布反馈式光纤激光水听器的系统噪声有较大影响。分析了该强度噪声在NPS算法数字实现中的传递过程,发现求导运算的非理想特性是解调结果中引入强度噪声的原因。提出了一种改进的NPS算法,使强度噪声在进入求导运算前被抵消,消除了强度噪声传递到解调结果中的途径。实验结果表明,当弛豫振荡峰处相对强度噪声为-84dB·Hz-1时对解调相位噪声的抑制在1kHz处达到了30dB。将改进后算法与不需要求导运算的反正切法进行了对比,进一步验证了其可抑制求导所引入的强度噪声。 The intensity noise caused by the relaxation oscillation of the laser has a great influence on the system noise of the distributed feedback fiber laser hydrophone. The transmission of the intensity noise in the digital implementation of NPS algorithm is analyzed. It is found that the nonideal property of the derivation is the reason of introducing the intensity noise into the demodulation result. An improved NPS algorithm is proposed so that the intensity noise is canceled before entering the derivation and the way of transferring the intensity noise to the demodulation result is eliminated. The experimental results show that when the relative intensity noise at the relaxation oscillation peak is -84dB · Hz-1, the suppression of demodulation phase noise reaches 30dB at 1kHz. The improved algorithm is compared with the arc tangent method which does not need the derivation algorithm, which further verifies that it can suppress the intensity noise introduced by the derivation.