采用正交光功率比值的光子型微波频率测量方案设计

Photonic Approach Using Quadrature Optical Power Ratios for Microwave Frequency Measurement

通过构建两个正交的光功率比值,以光子技术实施微波频率测量。首先,待测微波信号经外调制器加载到连续光源上,在单边带载波抑制调制下仅得到单个光边带;以光学梳状滤波器对其进行滤波处理,在输出端检测得到随微波频率增大而呈现余弦函数和正弦函数变化趋势的两个光功率;将这两个光功率与参考光功率进行比较后,进而得到余弦函数型和正弦函数型两个光功率比值,即正交光功率比值。基于这两个正交光功率比值,可以在整个梳状滤波响应的自由频谱区内检测出唯一的频率值。进而设计了两种具体方案来实现这一测频思路:两个连续光源和单个光学梳状滤波器的组合;或者单个连续光源和两个光学梳状滤波器的组合,并从实验上验证了方案二的可行性。与已报道的类似方案相比,设计的测频方案扩大了测频范围,尤其是在级联或并联型测频结构设计中具有潜在应用前景。

A photonic approach using two quadrature optical power ratios is proposed to peerform microwave frequency measurement.First,under the carrier-suppression and single-sideband modulation,a microwave signal is applied to modulate a cont;nuous-wave（CW） laser source,leading to the generation of a single sideband.,Then optical comb filters are adopted to process the sideband and two optical powers presenting sine-form and cosine-form distributions are detected as the microwave frequency increases.After comparing the two optical powers to the reference power,two optical power ratios of sine-form and cosine-form are obtained,namely quadurature optical power ratios.Based on the two optical ratios,the frequency is unambiguously estimated within the full free spectral range（FSR） of the comb filtering responses.Two setups are designed to verify the proposed approach,one consisting of two laser sources and a single comb filter,and the other including a single laser source and two comb filters.The latter setup is experimentally demonstrated.Compared with other reported approach,the proposed approach provides a larger measurement range and a promising way to design cascaded or parallel configurations.