An interferometric fiber sensor was developed and used to detect polarization changes resulting from varying the amplitude and frequency of an acoustic signal. The sensor was designed to be suited to geological activities such as seismic tomography, detection of sink holes, and early warning earthquake detection. The fiber sensor and a commercial geophone were subjected to the same tests to compare their characteristic response to different vibrations. The average signal sensitivities were 9.15 a.u./mJ and 8.37 a.u./mJ for the fiber sensor and geophone, respectively. The ability of each sensor to distinguish between short, successive events showed that the fiber sensor has superior sensitivity and resolution. This is attributed to the short recovery time of the optical fiber sensor. The geophone is limited in this regard by its inherent Faraday magnet and coil damping mechanism. The bandwidth of the optical fiber sensor is shown to be 3.349 kHz, more than 20 times that of the commercial geophone.
We describe an optical fibre-based method to estimate impact force and collision duration using time measurements recorded from acoustic signals of a table tennis ball bouncing on a table. The technique combines measurements obtained from a polarisation dependent optical fibre sensor with graphical analysis and kinetics through numerical calculations. The presented coefficient of restitution, collision time, impact force, and elastic deformation during each bounce of the table tennis ball were obtained using corresponding time series measurements and numerical analysis. A peak impact force of 38.4N was estimated for a ball of mass 2.83g and 39.7mm diameter dropped from a height of 31.5cm. The impact duration for the associated bounce was 0.68ms with a centre of gravity shift of 0.40mm and coefficient of restitution of 0.88. While the observed results are unique to the ball and table surface, the approach is an attempt to fully quantify collision parameters from basic measurement and instrumentation applicable to undergraduate students. The sensor developed in this paper finds application in sports performance monitoring, infrastructural health early warning systems and pressure sensitive manufacturing processes.
Innovation and advancement in technologies such as self-driving cars, machine learning, remote health and factory floor automation have led to extremely stringent next-generation communication requirements. For instance, in a self-driving car, sensor data may be streamed to a cloud-based computer. Decentralized machine learning relying on augmented data may be used to control the vehicle. Large amounts of sensor data, along with the real-time nature of the applications, demand requirements on the 5G networks needed to support applications such as this. Specifications for 5G networks require extremely low end-end latency <2020
<p>Geophones are essential for monitoring seismic activity to study the structure of the earth for ground surveys, mineral exploration and early warning detection of geo-hazards. Traditional electromagnetic based geophones are fairly effective in detecting micro-seismic activity and ambient signals. Their induction based mass-spring sensing mechanism can however be somewhat performance limiting. Limitations include reduced frequency response, resolution and recovery times between successive activities. This ultimately impacts the sensitivity and performance of the device. In this paper, we present a novel optical fiber geophone sensor that addresses these issues through superior sensitivity, performance and ease of deployment. Our optical fiber geophone is polarization based, single ended and operates on a Michelson interferometric principle. Tests were performed to compare the performance of our optical fibre geophone to that of a commercial electromagnetic geophone. Vibrations of varying magnitude were remotely generated at 1.065 m from both devices. Sensor signal responses to disturbances of energy lower than 1.1 mJ were plotted and analysed. Observed traces from the sensor responses were compared, showing that the fiber geophone has significantly shorter response and recovery times. As a result, the resolution between rapidly succeeding signals is considerably greater for the optical fiber geophone. Sensitivity plots of the amplitude response to the vibration energy gave a scatter of points depicting a higher degree of precision and accuracy for the fiber geophone. Response slopes of 11.70 a.u/mJ and 10.31 a.u/mJ respectively were obtained for the sensitivity of the optical fiber geophone versus the electromagnetic geophone. While the typical spurious frequency is close to 150 Hz for the traditional geophone, the bandwidth of the optical fiber geophone is an order of magnitude greater.</p><p>Keywords- Geophone<strong>,</strong> Optical fibre, Polarisation, Michelson Interferometer</p>
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