The Fiber-Optic Rotational Seismograph—Laboratory Tests and Field Application

Self Cite

Interest in measuring displacement gradients, such as rotation and strain, is growing in many areas of geophysical research. This results in an urgent demand for reliable and field-deployable instruments measuring these quantities. In order to further establish a high-quality standard for rotation and strain measurements in seismology, we organized a comparative sensor test experiment that took place in November 2019 at the Geophysical Observatory of the Ludwig-Maximilians University Munich in Fürstenfeldbruck, Germany. More than 24 different sensors, including three-component and single-component broadband rotational seismometers, six-component strong-motion sensors and Rotaphone systems, as well as the large ring laser gyroscopes ROMY and a Distributed Acoustic Sensing system, were involved in addition to 14 classical broadband seismometers and a 160 channel, 4.5 Hz geophone chain. The experiment consisted of two parts: during the first part, the sensors were co-located in a huddle test recording self-noise and signals from small, nearby explosions. In a second part, the sensors were distributed into the field in various array configurations recording seismic signals that were generated by small amounts of explosive and a Vibroseis truck. This paper presents details on the experimental setup and a first sensor performance comparison focusing on sensor self-noise, signal-to-noise ratios, and waveform similarities for the rotation rate sensors. Most of the sensors show a high level of coherency and waveform similarity within a narrow frequency range between 10 Hz and 20 Hz for recordings from a nearby explosion signal. Sensor as well as experiment design are critically accessed revealing the great need for reliable reference sensors.

Section: Introductionmentioning

confidence: 99%

Rotation, Strain, and Translation Sensors Performance Tests with Active Seismic Sources

Bernauer

Behnen

Wassermann

et al. 2021

Self Cite

“…Rotational sensors (gyroscopes) measuring rotational velocity are finding their application in more and more fields. To name only a few, one can mention seismology [ 1 , 2 , 3 ], structural health monitoring (SHM) [ 4 , 5 , 6 ], military [ 7 ], automotive [ 8 ], or in posture control [ 9 , 10 ]. In civil engineering, microelectromechanical system (MEMS) gyroscopes are getting particular attention because of their miniaturization and lower cost compared with the other systems [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Application of Rotation Rate Sensors in Modal and Vibration Analyses of Reinforced Concrete Beams

Bońkowski

Bobra

Zembaty

et al. 2020

The recent rapid development of rotation rate sensor technology opens new opportunities for their application in more and more fields. In this paper, the potential of rotational sensors for the modal analysis of full-scale civil engineering structural elements is experimentally examined. For this purpose, vibrations of two 6-m long beams made of ultra-high performance concrete (UHPC) were measured using microelectromechanical system (MEMS) rotation rate sensors. The beams were excited to vibrations using an impact hammer and a dynamic vibration exciter. The results of the experiment show that by using rotation rate sensors, one can directly obtain derivatives of mode shapes and deflection shapes. These derivatives of mode shapes, often called “rotational modes”, bring more information regarding possible local stiffness variations than the traditional transversal and deflection mode shapes, so their extraction during structural health monitoring is particularly useful. Previously, the rotational modes could only be obtained indirectly (e.g., by central difference approximation). Here, with the application of rotation rate sensors, one can obtain rotational modes and deflection shapes with a higher precision. Furthermore, the average strain rate and dynamic strain were acquired using the rotation rate sensors. The laboratory experiments demonstrated that rotation rate sensors were matured enough to be used in the monitoring and modal analyses of full-scale civil engineering elements (e.g., reinforced concrete beams).

“…It is based on our previous construction [27] and contains a light source-superluminescent diode (Exalos AG, Zürich, Switzerland), isolator (FCA, Niepołomice, Poland), two depolarizers (Phoenix Photonics, Birchington, UK), photodetector APD-1310 (Opotway, Taiwan), coupler (Phoenix Photonics, Birchington, UK), integrated optic chip (MIOC, IdealPhotonics Ltd., Shanghai, China), as well as 5 km of a single optical fiber SMF-28e+ (Corning Inc., New York, NY, USA) as a fiber coil wound as a quadrupole bifilar structure. MIOC is fabricated as a lithium niobate wafer by a high-temperature proton exchange technique [28], and it has two functions.…”

Section: Construction Of the Applied Fosrem Type Fos5mentioning

confidence: 99%

Measurements of Rotational Events Generated by Artificial Explosions and External Excitations Using the Optical Fiber Sensors Network

Kurzych

Jaroszewicz

Dudek

et al. 2020

Self Cite

Measurements of artificial events can substantially confirm the data validity of constructed rotational sensors, as well as provide methods for simplifying the measurement process. The above task, especially with international cooperation, can provide full-field measurement results of the target object, which can deliver more significant data and sensor properties. The paper presents vertical rotational velocity recordings gathered during an international experiment that took place at the Geophysical Observatory of the Ludwig Maximilian University of Munich in Fürstenfeldbruck, Germany. Data were obtained during artificial explosions, as well as external excitations induced by a VibroSeis truck. The authors present data recorded by two prototypes of optical fiber rotational sensors. They have been specially designed for rotational seismology needs and are characterized by a theoretical sensitivity equal to 2 × 10−8 rad/s/√Hz and a wide measuring range both in amplitude even up to 10 rad/s, and a frequency from DC to 1000 Hz. Their self-noise investigation during the aforementioned experiment showed that both sensors have precision no worse than 2 × 10−6 rad/s/sqrt (Hz) in all desired frequency range from 0.01 to 100 Hz. A down-sampling and a spectral analysis of the recorded signals are also presented. The recorded data and their analysis confirmed the performance and reliability of the applied optical fiber rotational sensors. Moreover, the presented international experiment underlines a special necessity for specifying the sensors’ performance test methodologies in the rotational seismology.