使用互补码光脉冲作为光时域反射计的探测脉冲可以大幅提高光时域反射计的性能，在不影响距离分辨率的前提下提高有效测量距离、减少测量所需时间。基于此，介绍了该方法的理论基础并给出了具体的应用方法及仿真结果。An optical time domain reflectometer using correlation technique may has much better performance than conventional otdr . the autocorrelation of Golay sequence has low sidelobes, so we can use Golay sequence as the probe signal.This paper present the theoretical foundation of this method and tell the way to change bipolar codes to unipolar codes.