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提出了一种测量长光纤微波光链路以及链路中某一器件残余相位噪声的方法。与以前传统的残余相位噪声测量方法相比,新提出的基于互相关的双音法抑制了不相关噪声源引入的噪声,而保留了待测器件的噪声。通过这种方法,测量了外调制长光纤微波光链路的残余相位噪声,一个6 km微波光纤链路的残余相位噪声在1 k Hz频偏处被测得为-130 d Bc/Hz,在10 k Hz频偏处被测得为-140 d Bc/Hz,相较于光纤长度为1 m的短微波光链路,残余相位噪声恶化了接近10 d B。另外,为了找出光电探测器的残余相位噪声与其非线性引起的射频功率压缩度之间的关系,还用这种方法测量了工作在不同条件下的光电探测器的残余相位噪声,实验结果表明:光电探测器的非线性会恶化它的残余相位噪声。
A method of measuring the residual phase noise of a long optical fiber microwave link and a device in the link is proposed. Compared with the traditional method of measuring residual phase noise, the newly proposed cross-correlation-based two-tone method suppresses the noise introduced by the uncorrelated noise source while preserving the noise of the device under test. In this method, the residual phase noise of an externally modulated fiber optical microwave link was measured. The residual phase noise of a 6 km microwave optical fiber link was measured as -130 d Bc / Hz at a frequency offset of 1 k Hz. Measured at -140 kBc / Hz at 10 k Hz offset, the residual phase noise worsened by nearly 10 d B compared to a short-momentary optical link with a fiber length of 1 m. In addition, in order to find out the relationship between the residual phase noise of the photodetector and the RF power compression caused by its non-linearity, this method is also used to measure the residual phase noise of photodetectors operating under different conditions. The experimental results show that : The non-linearity of a photodetector deteriorates its residual phase noise.