Toward a Metadata Standard for Distributed Acoustic Sensing (DAS) Data Collection

With increasing geophysical applications using distributed acoustic sensing (DAS) technology, there is a need to implement a metadata standard specifically for DAS to facilitate the integration of DAS measurements across experiments and increase reusability. We propose a metadata standard intended primarily for the DAS research community, which fully describes the five key components of a DAS experiment: (1) interrogator; (2) data acquisition; (3) channels; (4) cable; and (5) fiber. The proposed metadata schema, which is the overall structure of the metadata, is hierarchical based, with a parent “overview” metadata block describing the experiment, and two main child branches describing the instrument (i.e., interrogator, photonics setup, and acquisition parameters) and the sensor locations (i.e., cable installation and fiber properties). The metadata schema is designed to be independent of the time-series data so that corrections and updates can be applied to the metadata without having to manipulate large volumes of time-series data. Unique identifiers are used as pointers that map different components within the metadata schema; they also provide a natural basis for the naming convention (i.e., source identifier) of the time-series data in which the time series can be described using identifiers defined by the metadata standard. We advocate for the metadata to be stored in a separate structure from the data itself. The metadata standard is successfully applied to four common scenarios: horizontal direct buried cable, dark fiber, borehole cable, and active survey, and two hypothetical scenarios: multiple interrogators to a single cable, and a single interrogator to multiple cables. Finally, we use GitHub to implement version control for the metadata standard, to enable community collaboration and facilitate sustainable development of the metadata standard, as the DAS technology and application continue to evolve.