Distributed fibre-optic sensing

In plain language

An optical fibre is a thin strand of glass that carries light, and the same strand used for internet traffic can also act as a sensor. A laser sends light pulses down the fibre, and a tiny amount of light scatters back from every section along the way. If the ground shakes, or something presses on the cable, the fibre stretches or vibrates slightly, and the pattern of the returning light changes at that exact spot.

By timing the returning light, the instrument can work out where along the cable each change happened. One fibre can therefore act like thousands of microphones or seismometers in a line. Researchers have used unused, or dark, telecom fibre to record earthquakes and other ground vibrations, and the same idea could help watch pipelines and power lines, although the cost and the quality of the signal still limit wider use.

Technical explanation

Most systems described as distributed acoustic sensing (DAS) use phase-sensitive optical time-domain reflectometry (phi-OTDR). A coherent laser pulse travels down the fibre, and the light Rayleigh-backscattered from randomly placed scattering points interferes with itself. External disturbances change the relative positions of these scattering points, which alters the interference at each fibre position. Gorshkov and colleagues describe this mechanism in their 2022 review in Sensors, and the signal is read as a time series for each position along the cable.

The approach has been applied to existing cables. Ajo-Franklin and colleagues (2019) used unlit, or dark, telecom fibre for near-surface characterisation and broadband seismic event detection. Williams and colleagues (2019) reported microseisms and teleseisms recorded on submarine dark fibres. Earlier, Marra and colleagues (2018) showed that terrestrial and submarine cables could detect earthquakes using ultrastable laser interferometry, a related but different optical method. Lindsey and Martin (2021) reviewed this wider field of fibre-optic seismology.

DAS is sensitive to strain along the cable, so response depends on the direction of the fibre and on how well the cable is coupled to the ground. Gorshkov and colleagues describe recent gains in phase noise and polarisation fading, note that spectral response and processing speed still need improvement for some uses such as sound engineering, and identify cost as the main obstacle to integration into scientific fields.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• Cost is named as the main obstacle to wider use in scientific fields (Gorshkov and colleagues, 2022).
• Phase noise and polarisation fading have been key performance issues, and recent work has reduced both (Gorshkov and colleagues, 2022).
• Some DAS uses, such as sound engineering, need better spectral response and faster signal processing (Gorshkov and colleagues, 2022).
• Much of the published work uses dark fibre that telecom operators make available. The sources reviewed here do not describe general access terms, so wide use depends on agreements with cable owners.
• Different scattering methods measure different quantities and have different range, resolution and update-rate trade-offs.
• DAS responds to strain along the fibre, so a vibration arriving in an unfavourable direction can produce a weak or null signal.
• Poor coupling between fibre and its surroundings, Rayleigh fading, reflections and reverberation can distort or hide measurements.
• The 2022 blind beamforming result was evaluated on one 8.63 km geothermal survey and 50 source positions; field performance depends on local geometry and propagation conditions.
• Long sensing distances can reduce signal-to-noise ratio, particularly for Raman temperature sensing.

Possible future uses

Timeline

1. 3 Aug 2018Marra and colleagues report earthquake detection with terrestrial and submarine cables using ultrastable laser interferometry in Science. Sources: [1]
2. 4 Feb 2019Ajo-Franklin and colleagues publish a study of distributed acoustic sensing on dark telecom fibre for near-surface characterisation and seismic event detection in Scientific Reports. Sources: [2]
3. 18 Dec 2019Williams and colleagues report microseisms and teleseisms recorded with submarine dark fibres in Nature Communications. Sources: [3]
4. 30 May 2021Lindsey and Martin publish the review 'Fiber-Optic Seismology' in the Annual Review of Earth and Planetary Sciences. Sources: [4]
5. 28 Jan 2022Gorshkov and colleagues publish a state-of-the-art review of scientific applications of distributed acoustic sensing in Sensors. Sources: [5]
6. 7 May 2022An open-access review surveys Raman distributed fibre-optic sensing physics and engineering applications. Sources: [6]
7. 11 Jul 2022Researchers report blind near-field processing of DAS measurements to improve signal quality and estimate acoustic source positions in a geothermal survey. Sources: [7]
8. 24 Feb 2026A perspective describes a proposed distributed fibre sensor concept in which the sensing fibre forms a laser cavity. Sources: [8]

Futures this could help bring about

How far away?

Bridge sensors that flag possible damage

Pilots · 3 of 5 steps done

Related breakthroughs

• Leeds researchers record seismic signals along a fibre cable in boreholes up to 250 m deep (28 May 2025)

Glossary

Distributed acoustic sensing (DAS)

A method that uses a single optical fibre as a long line of vibration sensors, reporting changes at many points along its length.

Rayleigh backscatter

Light scattered by tiny, random density variations in glass, sent back towards the source along the fibre.

Dark fibre

Optical fibre installed in a cable but not lit or used for live data traffic.

Microseism

A continuous, low-level ground motion caused mainly by ocean waves and weather, recorded by seismometers.

Gauge length

The effective length of fibre over which a distributed measurement is averaged.

Sources

1. peer reviewed paper
   Ultrastable laser interferometry for earthquake detection with terrestrial and submarine cables
   Giuseppe Marra, Cecilia Clivati, Richard Luckett et al.. Science, 3 Aug 2018. DOI: 10.1126/science.aat4458. Accessed 21 Oct 2026.
2. peer reviewed paper
   Distributed Acoustic Sensing Using Dark Fiber for Near-Surface Characterization and Broadband Seismic Event Detection
   Jonathan B. Ajo-Franklin, Shan Dou, Nathaniel J. Lindsey et al.. Scientific Reports, 4 Feb 2019. DOI: 10.1038/s41598-018-36675-8. Accessed 21 Oct 2026.
3. peer reviewed paper
   Distributed sensing of microseisms and teleseisms with submarine dark fibers
   Ethan F. Williams, María R. Fernández-Ruiz, Regina Magalhaes et al.. Nature Communications, 18 Dec 2019. DOI: 10.1038/s41467-019-13262-7. Accessed 21 Oct 2026.
4. review article
   Fiber-Optic Seismology
   Nathaniel J. Lindsey, Eileen R. Martin. Annual Review of Earth and Planetary Sciences, 30 May 2021. DOI: 10.1146/annurev-earth-072420-065213. Accessed 21 Oct 2026.
5. review article
   Scientific Applications of Distributed Acoustic Sensing: State-of-the-Art Review and Perspective
   Boris G. Gorshkov, Kivilcim Yüksel, Andrei A. Fotiadi et al.. Sensors (Basel), MDPI, 28 Jan 2022. DOI: 10.3390/s22031033. Accessed 21 Oct 2026.
6. review article
   Physics and applications of Raman distributed optical fiber sensing
   Jian Li, Mingjiang Zhang. Light: Science & Applications, 7 May 2022. DOI: 10.1038/s41377-022-00811-x. Accessed 22 Oct 2026.
7. peer reviewed paper
   Enhancing fibre-optic distributed acoustic sensing capabilities with blind near-field array signal processing
   Felipe Muñoz, Marcelo A. Soto. Nature Communications, 11 Jul 2022. DOI: 10.1038/s41467-022-31681-x. Accessed 22 Oct 2026.
8. peer reviewed paper
   Towards lasing systems for distributed fibre sensing
   Luc Thévenaz. Light: Science & Applications, 24 Feb 2026. DOI: 10.1038/s41377-026-02217-5. Accessed 22 Oct 2026.

Revision history

5 changes since this profile was created.