Opto-mechanical lab-on-fibre seismic sensors detected the Norcia earthquake

Abstract

We have designed and developed lab-on-fibre seismic sensors containing a micro-opto-mechanical cavity on the fibre tip. The mechanical cavity is designed as a double cantilever suspended on the fibre end facet and connected to a proof mass to tune its response. Ground acceleration leads to displacement of the cavity length, which in turn can be remotely detected using an interferometric interrogation technique. After the sensors characterization, an experimental validation was conducted at the Italian National Institute of Geophysics and Volcanology (INGV), which is responsible for seismic surveillance over the Italian country. The fabricated sensors have been continuously used for long periods to demonstrate their effectiveness as seismic accelerometer sensors. During the tests, fibre optic seismic accelerometers clearly detected the seismic sequence that culminated in the severe Mw6.5 Norcia earthquake that struck central Italy on October 30, 2016. The seismic data provided by the optical sensors were analysed by specialists at the INGV. The wave traces were compared with state-of-the-art traditional sensors typically incorporated into the INGV seismic networks. The comparison verifies the high fidelity of the optical sensors in seismic wave detection, indicating their suitability for a novel class of seismic sensors to be employed in practical scenarios.

2D materials coated on etched optical fibers as humidity sensor

“…The great advantages of optical sensors such as high speed, insensitive to electromagnetic interference, anti-explosion, small size, low weight, durable and chemically inert, and low transmission make them practical and affordable 1 , 2 . However, optical fiber sensors can be used to measuring different physical properties, such as measurements of RI, strain 3 , temperature 4 , 5 , and humidity 4 – 10 . The mechanism of these sensors is very dependent on changes in the refractive index 3 , 4 .…”

“…However, optical fiber sensors can be used to measuring different physical properties, such as measurements of RI, strain 3 , temperature 4,5 , and humidity [4][5][6][7][8][9][10] . The mechanism of these sensors is very dependent on changes in the refractive index 3,4 . Usually, these sensors are made by modifying the geometry of optical fiber such as sidepolished fiber, a long period fiber grating (LPG), and hollow-core fiber sensors that are very complicated [5][6][7][8][9][10][11][12][13] .…”

Sensors for Context-Aware Smart Healthcare: A Security Perspective

“…In recent years, this activity has being monitored using the inexpensive tri-axial accelerometer sensors that, in combination with machine learning techniques, allows detecting or predicting seismic events [ 242 , 243 , 244 ]. Additionally, opto-mechanical sensors based on optical fibre technology have already been assessed to monitor ground motions [ 245 ].…”

Lab-On-Fiber Technology: A Roadmap toward Multifunctional Plug and Play Platforms

“…As an example, a ferrule-top approach was recently used to integrate a complex micromechanical structure featuring a dual-beam cantilever with a properly designed mass onto an optical fiber tip. The innovative optomechanical structure was designed to act as a seismic accelerometer with competitive performance in seismic applications, when compared to that of commercial platforms [ 81 ]. Prototypes were fabricated, and their responsivity was preliminarily measured in the laboratory at resolutions down to 0.44 μg/√Hz, over a 3-dB frequency band of 60 Hz.…”

“…( d ) Wavelet coherence between the optical and episensor displacement signals over a 400-s window. Reproduced with permission from [ 81 ]. The article is licensed under a Creative Commons Attribution 4.0 International License: .…”