The cardiovascular health of the human population is a major concern for medical clinicians, with cardiovascular diseases responsible for 48% of all deaths worldwide, according to the World Health Organization. The development of new diagnostic tools that are practicable and economical to scrutinize the cardiovascular health of humans is a major driver for clinicians. We offer a new technique to obtain seismocardiographic signals up to 54 Hz covering both ballistocardiography (below 20 Hz) and audible heart sounds (20 Hz upward), using a system based on curvature sensors formed from fiber optic long period gratings. This system can visualize the real-time three-dimensional (3-D) mechanical motion of the heart by using the data from the sensing array in conjunction with a bespoke 3-D shape reconstruction algorithm. Visualization is demonstrated by adhering three to four sensors on the outside of the thorax and in close proximity to the apex of the heart; the sensing scheme revealed a complex motion of the heart wall next to the apex region of the heart. The detection scheme is low-cost, portable, easily operated and has the potential for ambulatory applications.
Cardiovascular health of the human population is a major concern for medical clinicians, with cardiovascular diseases responsible for 48% of all deaths worldwide, according to the World Health Organisation. Therefore the development of new practicable and economical diagnostic tools to scrutinise the cardiovascular health of humans is a major driver for clinicians. We offer a new technique to obtain seismocardiographic signals covering both ballistocardiography (below 20Hz) and audible heart sounds (20Hz upwards). The detection scheme is based upon an array of curvature/displacement sensors using fibre optic long period gratings interrogated using a variation of the derivative spectroscopy interrogation technique.
An array of in-line curvature sensors on a garment is used to monitor the thoracic and abdominal movements of a human during respiration. The results are used to obtain volumetric changes of the human torso in agreement with a spirometer used simultaneously at the mouth. The array of 40 in-line fiber Bragg gratings is used to produce 20 curvature sensors at different locations, each sensor consisting of two fiber Bragg gratings. The 20 curvature sensors and adjoining fiber are encapsulated into a low-temperature-cured synthetic silicone. The sensors are wavelength interrogated by a commercially available system from Moog Insensys, and the wavelength changes are calibrated to recover curvature. A three-dimensional algorithm is used to generate shape changes during respiration that allow the measurement of absolute volume changes at various sections of the torso. It is shown that the sensing scheme yields a volumetric error of 6%. Comparing the volume data obtained from the spirometer with the volume estimated with the synchronous data from the shape-sensing array yielded a correlation value 0.86 with a Pearson's correlation coefficient p<0.01.
Eight re-configurable, synchronized resonant cavity time-division-multiplexed FBG sensor interrogators provide 16,800 high-resolution measurements-per-second from 280 axially embedded strain sensors, for the analysis of vortex-shedding-induced vibration and bending in a composite oil riser pipe.
We report for the first time the design, implementation and commercial application of a hand-held optical time division multiplexed, distributed fibre Bragg grating sensor system. A unique combination of state-of-the art electronic and optical components enables system miniaturization whilst maintaining exceptional performance. Supporting more than 100 low-cost sensors per channel, the battery-powered system operates remotely via a wireless GSM link, making it ideal for real-time structural health monitoring in harsh environments.
Driven by highly configurable timing electronics, an off-the-shelf telecommunications semiconductor optical amplifier performs combined amplification and gating. This novel optical configuration boasts a spatial resolution of less than 20cm and an optical signal to noise ratio of better than 30dB, yet utilizes sensors with reflectivity of only a few percent and does not require RF speed signal processing devices.
This paper highlights the performance and cost advantages of a system that utilizes TDM-style mass manufactured commodity FBGs. Created in continual lengths, these sensors reduce stock inventory, eradicate application-specific array design and simplify system installation and expansion.
System analysis from commercial installations in oil exploration, wind energy and vibration measurement will be presented, with results showing kilohertz interrogation speed and microstrain resolution.
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