Moon Sucbei, Chen Zhongping
Beckman Laser Institute, University of California, Irvine, Irvine, CA 92617, USA.
Department of Physics, Kookmin University, Seoul 02707, South Korea.
Biomed Opt Express. 2018 Oct 9;9(11):5280-5295. doi: 10.1364/BOE.9.005280. eCollection 2018 Nov 1.
Phase-resolved imaging of swept-source optical coherence tomography (SS-OCT) is subject to phase measurement instabilities involved with the sweep variation of a frequency-swept source. In general, optically generated timing references are utilized to track the variations imposed on OCT signals. But they might not be accurately synchronized due to relative time delays. In this research, we investigated the impact of the signal delays on the timing instabilities and the consequent deviations of the measured phases. We considered two types of timing signals utilized in a popular digitizer operation mode: a sweep trigger from a fiber Bragg grating (FBG) that initiates a series of signal sampling actions clocked by an auxiliary Mach-Zehnder interferometer (MZI) signal. We found that significant instabilities were brought by the relative delays through incoherent timing corrections and timing collisions between the timing references. The best-to-worst ratio of the measured phase errors was higher than 200 while only the signal delays varied. Noise-limited phase stability was achieved with a wide dynamic range of OCT signals above 50 dB in optimized delays. This demonstrated that delay optimization is very effective in phase stabilization of SS-OCT.
扫频源光学相干断层扫描（SS-OCT）的相位分辨成像受到与扫频源扫频变化相关的相位测量不稳定性的影响。一般来说，利用光学产生的定时参考来跟踪施加在OCT信号上的变化。但由于相对时间延迟，它们可能无法精确同步。在本研究中，我们研究了信号延迟对定时不稳定性以及所测相位的后续偏差的影响。我们考虑了一种流行的数字化仪操作模式中使用的两种定时信号：来自光纤布拉格光栅（FBG）的扫频触发信号，它启动由辅助马赫-曾德尔干涉仪（MZI）信号计时的一系列信号采样动作。我们发现，相对延迟通过非相干定时校正和定时参考之间的定时冲突带来了显著的不稳定性。在所测相位误差中，最佳与最差之比高于200，而此时仅信号延迟发生变化。在优化延迟条件下，对于动态范围超过50 dB的宽范围OCT信号，实现了噪声限制的相位稳定性。这表明延迟优化在SS-OCT的相位稳定方面非常有效。
