微波光链路和光电探测器残余相位噪声的测量

Residual phase noise measurements of microwave optical links and photo-electric detector

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 for measuring the residual phase noise(RPN) of long microwave optical links(MOLs)and individual components in the MOL was proposed in this paper. Compared with the previous RPN measurement methods, the two-tone correlation-based method suppressed the noise contributions of the uncorrelated noise sources except that of the device under test(DUT). By this method, the RPN of externally modulated long MOLs was measured, the RPN of a 6 km MOL was successfully measured to be-130 d Bc/Hz at 1 k Hz offset and-140 d Bc/Hz at 10 k Hz offset, compared with a 1 m short MOL,the RPN deteriorated about 10 d B. In addition, in order to find out the relationship between the RPN and the RF power compression due to the nonlinearity of the photo-electric detector(PD), the RPNs of the PD with different incident optical powers and bias voltages were also measured by this method. The experimental results reveal that the nonlinearity of PD can deteriorate its RPN.