Linear optical sampling (LOS) is a powerful technique to circumvent the electronic bottleneck arising in optical modulation analyzer (OMA). To extend the range of operation wavelength for the LOS-based OMA, the fiber optical frequency comb (FOFC) is proposed to replace the narrowband mode-locked fiber laser (NMFL) as an optical sampling source. However, this procedure reduces the signal-to-noise ratio (SNR), due to the constraints of the unideal response of balanced photodetector (BPD) and the limited power per FOFC tone. Here, we investigate the biased balance detection (BBD) scheme to overcome such issue. Our simulation results show that, the characterization performance of the FOFC-based LOS with the help of the BBD scheme is almost the same as that of the NMFL-based LOS, when the PDM-QPSK/16QAM/64QAM signals are set as the signal under test (SUT). Meanwhile, we find that the dynamic range of SUT input power is determined by the BPD imbalance and the FOFC power. By increasing either the average power of the FOFC from 4 to 10 mW or the imbalance of the BPD from 1.03 to 1.04, we can enhance the dynamic range of SUT input power by 8.8 mW and 6.6 mW, respectively. Finally, we develop the equipment and experimentally verify the BBD scheme by a precise characterization of 32 GBaud PDM-QPSK signal.

中文翻译：

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基于光纤频率梳的线性光学采样的偏置平衡检测


线性光学采样（LOS）是一种克服光学调制分析仪（OMA）电子瓶颈的强大技术。为了扩展基于LOS的OMA的工作波长范围，提出用光纤频率梳（FOFC）代替窄带锁模光纤激光器（NMFL）作为光学采样源。然而，由于平衡光电探测器 (BPD) 的不理想响应和每个 FOFC 音调的功率有限的限制，该过程降低了信噪比 (SNR)。在这里，我们研究了偏置平衡检测（BBD）方案来克服这个问题。我们的仿真结果表明，当将 PDM-QPSK/16QAM/64QAM 信号设置为信号时，借助 BBD 方案的基于 FOFC 的 LOS 的表征性能与基于 NMFL 的 LOS 的表征性能几乎相同。被测（SUT）。同时，我们发现SUT输入功率的动态范围是由BPD不平衡和FOFC功率决定的。通过将 FOFC 的平均功率从 4 mW 增加到 10 mW 或将 BPD 的不平衡性从 1.03 增加到 1.04，我们可以将 SUT 输入功率的动态范围分别提高 8.8 mW 和 6.6 mW。最后，我们开发了设备并通过 32 GBaud PDM-QPSK 信号的精确表征来实验验证 BBD 方案。