Onland and Offshore Extrinsic Fabry–Pérot Optical Seismometer at the End of a Long Fiber

Pascal Bernard; Romain Feron; Guy Plantier; Alexandre Nercessian; Julien Couteau; Anthony Sourice; Mathieu Feuilloy; Michel Cattoen; Han‐cheng Seat; Patrick Chawah; Jean Chéry; Christophe Brunet; Frederick Boudin; Daniel Boyer; Stéphane Gaffet; Louis Geli; Pascal Pelleau

doi:10.1785/0220190049

Article dans une revue

Onland and Offshore Extrinsic Fabry–Pérot Optical Seismometer at the End of a Long Fiber

Pascal Bernard ¹ Romain Feron ^{2, 3} Guy Plantier ^{2, 3} Alexandre Nercessian ¹ Julien Couteau ¹ Anthony Sourice ^{2, 3} Mathieu Feuilloy ^{2, 3} Michel Cattoen ⁴ Han‐cheng Seat ⁴ Patrick Chawah Jean Chéry ⁵ Christophe Brunet ¹ Frederick Boudin ⁵ Daniel Boyer ⁶ Stéphane Gaffet ⁶ Louis Geli ⁷ Pascal Pelleau ⁸

1 IPGP - Institut de Physique du Globe de Paris

2 GSII - ESEO-GSII

ESEO-Tech

3 LAUM - Laboratoire d'Acoustique de l'Université du Mans

4 LAAS-OSE - Équipe Optoélectronique pour les Systèmes Embarqués

LAAS - Laboratoire d'analyse et d'architecture des systèmes

5 Géosciences Montpellier

6 LSBB - Laboratoire Souterrain à Bas Bruit

7 LIRIGM - Laboratoire Interdisciplinaire de Recherche Impliquant la Géologie et la Mécanique

8 IFREMER Centre de Bretagne - Institut Français de Recherche pour l'Exploitation de la Mer - Brest

Abstract : We report here the design, performance, and in situ demonstration, on‐land and offshore, of an innovative high‐resolution low‐cost optical (laser) seismometer. The instrument was developed within the Laser Interferometry for Earth Strain project (French Agence Nationale de la Recherche [ANR] program), and first tested at the low‐noise underground laboratory Laboratoire Souterrain à Bas Bruit (LSBB, France). It is based on Fabry–Pérot optical interferometry between the extremity of a probing optical fiber and a reflecting mirror secured to the mobile mass of a passive 2 Hz geophone. The detection technique is based on the wavelength modulation of the laser diode (1310 nm), which allows the separation of the optical power into two signals in quadrature, thanks to an heterodyne technique. The relative displacement of the mobile mass is retrieved in real time by the phase unwrapping of these two signals. At LSBB, the fiber was 3 km long. It recorded many teleseismic earthquakes and a few regional ones, and resolves the low‐seismic noise of the Earth for periods up to 6 s, presenting an acceleration noise floor lower than 1 ng/Hz in the 0.3–5 Hz range. A three‐component version of this fiber‐based interferometric 2 Hz geophone has been recently constructed, shielded in a hyperbaric container, and installed offshore for test in Brittany (France) in April 2018, with an improved control system. Its record of the marine ambient noise matches those of a collocated commercial broadband seismometer for periods up to 50 s. This opens promising perspectives for large‐scale ocean bottom instrumentation with up to 50‐kilometer‐long optical lines; an installation is planned for 2020, off Guadeloupe, with a 5‐kilometer‐long fiber cable. It may also prove useful for installations in other challenging and exposed environments, such as deep hot boreholes, active volcanoes, unstable landslides, for real‐time monitoring in regions with high natural hazard, but also for seismic monitoring of geoindustries.

Type de document :

Article dans une revue

Domaine :

Sciences de l'ingénieur [physics] / Traitement du signal et de l'image [eess.SP]

Sciences de l'ingénieur [physics] / Electronique

Planète et Univers [physics] / Sciences de la Terre / Géophysique [physics.geo-ph]

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https://hal.archives-ouvertes.fr/hal-02380162
Contributeur : Anne-Flore Jarry <>
Soumis le : mercredi 31 mars 2021 - 16:57:26
Dernière modification le : mercredi 7 avril 2021 - 18:13:00

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