Advanced signal processing for dual comb interferometry

双梳光谱学是近年来发展比较成熟的一种光谱分析方法。它基本上是从一个由几个小组倡导并展示出潜力的实验室好奇心发展到实际找到“真实世界”的应用，例如在油气田中的泄漏检测。这项技术使用两个高精度激光器，每个激光器都发射控制良好的离散频率。激光梳子的辐射从一个方面控制(或已知)到另一个方面，精度惊人，小数位超过15位！这些梳子被用来探测物质，从远处检索几种化合物的独特特征。在光学光谱学中，频率梳提供了比经典方法更好的分辨率和灵敏度。梳状光谱在试图检测复杂混合物中的痕量成分时尤其闪耀。在广泛的光谱范围内的高分辨率使得能够区分独特的特征，确切地说，准确地读出丰富成分的“线之间”，而同时的高灵敏度允许检测到百万分之几或十亿分之几的污染物。第一个重要的应用是温室气体监测。有几种气体即使以微量存在，也是我们碳预算的重要贡献者。甲烷和乙烷的情况就是如此，它们的监测不仅对确保工业符合法规、各国遵守国际协议至关重要，而且还对减少资源浪费至关重要，因为大约2%的天然气因泄漏而损失。第二个应用是通过呼吸检测进行诊断。就像呼气分析仪可以量化你的血液酒精水平一样，类似的设备可以检测到不同的挥发性有机化合物，其呼气中的浓度可以指示几种疾病。例如，氨的痕迹表明肾脏有问题，而丁烷则标志着肺癌。对于给定的分辨率和测量时间，梳状光谱在可实现的灵敏度方面具有非常好的优点。然而，它在增加测量激光功率的可能性方面受到严重限制。检测链中的非线性和系统误差很快就会出现。这些都是十年前就知道的，但在采用这项技术方面并不是最严重的违法者，所以没有从纠正的角度适当地解决这些问题。现在他们限制了几种测量方法，该计划建议解决这些问题。这将允许更好地利用可用的激光功率、更好的检测灵敏度和更快的测量速度，为解锁实际应用做出贡献。加拿大在光学光谱学方面拥有雄厚的工业基础，几个省份的公司向不同的细分市场销售仪器：从食品和药品生产线的质量控制到用于安全和环境监测的遥感。加拿大的工业感受器已经到位。

Dual comb spectroscopy is a paradigm that has greatly matured in recent years. It basically went from a lab curiosity championed by a few groups and exhibiting potential to actually finding "real-world" applications such a leak detection in oil and gas fields. The technique uses two high precision lasers each emitting well controlled discrete frequencies. The radiation of the laser combs is controlled (or known) one respect to the other to astounding accuracy, over 15 decimal places! Those combs are used to probe matter retrieving, from a distance, unique signatures for several chemical compounds. In optical spectroscopy, frequency combs provide better resolution and sensitivity than classical approaches. Comb spectroscopy shines particularly when trying to detect trace constituents in complex mixes. The high resolution over a broad spectral range enables distinguishing between unique signatures, quite literally reading "between the lines" of abundant components while the simultaneous high sensitivity permitting parts per million or per billion detection of contaminants. A first important application is greenhouse gases monitoring. Several gases when present even in trace amounts are significant contributors to our carbon budget. This is the case for methane and ethane whose monitoring is essential not only to make sure that industries meet regulations, that countries respect international agreements but also to reduce waste of resources since around 2% of natural gas is lost through leaks. A second application is diagnosis through breath detection. Much like a breath analyser can quantify your blood alcohol level, a similar device could detect different volatile organic compounds whose concentration in breath is indicative of several diseases. For instance, traces of ammonia indicate renal issues while butane marks lung cancer. Comb spectroscopy has a very good merit factor in terms of achievable sensitivity for a given resolution and measurement time. It is however severely limited in the possibility of increasing measured laser power. Non-linearity in the detection chain and systematic errors quickly arise. These are known since a decade but were not the worst offenders in the adoption of the technique, so they were not properly addressed from a correction perspective. Now that they limit several measurements, this program proposes addressing these issues. This will allow better use of available laser power, better detection sensitivity and faster measurements, contributing in unlocking practical applications. Canada has a strong industrial base in optical spectroscopy, with companies in several provinces selling instruments worldwide to different market segments: from quality control in food and pharmaceutical production lines to remote sensing for security and environmental monitoring. Canadian industrial receptors are already in place.