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Measuring Instrument Response and Self-Noise Level of Telecommunication-Fiber-Optic DAS Arrays

Description: 

Distributed acoustic sensing (DAS) is an emerging technology that converts an optical fiber into a dense array of strain sensors. It is essential to quantify its technical performance to ensure the accuracy of DAS recorded phase and amplitude information. Recent studies show that the accuracy of phase information (e.g., travel time measurements) recorded by DAS is comparable to broadband stations. However, DAS's amplitude response and self-noise level have not been fully quantified, especially for dark fiber experiments which use pre-existing telecommunication cables with less available fiber-ground coupling information. Without the coupling information, it is a challenge to calculate the amplitude response of DAS theoretically. Using the co-located conventional seismometers, we empirically measure the amplitude response of telecommunication-fiber-optic DAS arrays. We systematically perform the measurements on multiple DAS arrays using the body wave and surface wave of teleseismic and local earthquakes spanning the 0.01 to 10 Hz frequency range. Our preliminary results based on the DAS arrays in Ridgecrest and Long Valley show that the array-average amplitude response is around 0dB with about 10 dB fluctuation depending on frequency. The amplitude response information will help determine the ground motion's absolute amplitude and earthquake magnitude. In addition, we also quantify the self-noise level of these DAS arrays. The noise level information is essential for evaluating the detection ability of DAS for weak signals. The methodology proposed in this study can be used to quantify the instrument performance of future DAS experiments.

Session: Understanding Earth Systems with Fiber-optic Cables

Type: Oral

Date: 4/19/2023

Presentation Time: 09:00 AM (local time)

Presenting Author: Qiushi Zhai

Student Presenter: No

Invited Presentation: 

Authors