Lukasz Dziuda

Monitoring Respiration and Cardiac Activity Using Fiber Bragg Grating-Based Sensor

This paper shows the design of a fiber-based sensor for living activities in human body and the results of a laboratory evaluation carried out on it. The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities-breathing and cardiac rhythm. The device consists of a Bragg grating inscribed into a single mode optical fiber and operating on a wavelength of around 1550 nm. The fiber Bragg grating (FBG) is mounted inside a pneumatic cushion to be placed between the backrest of the seat and the back of the monitored person. Deformations of the cushion, involving deformations of the FBG, are proportional to the vibrations of the body leaning on the cushion. Laboratory studies have shown that the sensor allows for obtaining dynamic strains on the sensing FBG in the range of 50-124 μ strain caused by breathing and approximately 8.3 μstrain induced by heartbeat, which are fully measurable by todays FBG interrogation systems. The maximum relative measurement error of the presented sensor is 12%. The sensors simple design enables it to be easily implemented in pilots and drivers seats for monitoring the physiological condition of pilots and drivers.

Fiber Bragg Grating Strain Sensor Incorporated to Monitor Patient Vital Signs During MRI

This paper reports on results obtained from monitoring the respiration and cardiac activity of a patient during a magnetic resonance imaging (MRI) survey using an optical strain sensor based on a fiber Bragg grating. The sensor is proposed specifically to acquire ballistocardiographic signals from a patient exposed to high intensity electromagnetic radiation. A Bland-Altman analysis shows the measurements that have a satisfactory accuracy for monitoring purposes, and the relative error is . The method is both noninvasive and safe for the patient. In addition, the sensor does not affect the MRI imaging quality.

Performance analysis of the Fiber Bragg grating Interrogation system based on an arrayed waveguide grating

In this paper we analyze performance of the Fiber Bragg Grating (FBG) Interrogation System based on an Arrayed Waveguide Grating (AWG) device. The spectrum of light reflected from the FBG sensor is analyzed using an AWG which acts as a coarse spectrometer. Using measurement points from the AWG channels, the original spectrum of the sensing element is reconstructed by a means of curve fitting. The measurement system is modeled in LabView environment, which allows to modify the FBG and AWG parameters and to simulate the measurement process. This, in turn, allows quantifying the measurement errors resulting from the nonlinearity of the particular FBG/AWG configuration, and allows optimizing the system design for the particular measurement errors permitted. In addition to the simulations of the proposed measurement system, we provide details of the laboratory evaluation.

Hybrid fiber optic voltage sensor for remote monitoring of electrical submersible pump motors

We report on the design and experimental evaluation of the hybrid fiber Bragg grating (FBG) piezoelectric voltage sensor developed specifically for remote monitoring of electrical submersible pump (ESP) motors. Unlike a previously reported transducer based on a single piezo- electric element, the voltage rating of the presented device could be as low as 500 V due to the use of a multilayer piezoelectric stack as the primary voltage-to-strain transducer. This enables the use of such sen- sors across a wider range of ESP applications, which often have subki- lovolt voltage ratings. In addition to the design details, we present details of the full characterization of the device, including the hysteresis and temperature-dependence characteristics and discuss ways of eliminating or reducing these effects. We also demonstrate that the sensor can be used to simultaneously measure voltage and temperature.

Design and evaluation of a pre-prototype hybrid fiber-optic voltage sensor for a remotely interrogated condition monitoring system

In this paper we give details of the design and laboratory evaluation of the pre-prototype hybrid fiber Bragg grating piezoelectric voltage sensor for a remotely interrogated condition monitoring system, such as the measurement system used for monitoring of electrical submersible pump (ESP) motors. The proposed sensor design is directed towards the upper voltage rating (5 kV) of ESP motors.

Interrogation of extrinsic Fabry-Perot interferometric sensors using arrayed waveguide grating devices

In this paper we present details of a solid state interrogation system based on a 16-channel arrayed waveguide grating (AWG) for interrogation of extrinsic Fabry-Perot interferometric (EFPI) sensors. The sensing element is configured in a reflecting mode and is illuminated by a broad-band light source through an optical fiber. The spectrum of light reflected from the sensor is analyzed using an AWG device acting as a coarse spectrometer. Using measurement points from the AWG channels, the original spectrum of the sensing element is reconstructed by a means of curve fitting. This allows sufficient information for the position of the reflection peak (or inverted peak) to be uniquely determined and the value of a measurement quantity obtained. In addition to the theoretical simulations of the proposed measurement system, we provide details of the laboratory evaluation using an EFPI strain sensor.

Dynamic strain measurement using an extrinsic Fabry-Perot interferometric sensor and an arrayed waveguide grating device

In this paper, we demonstrate an interrogation system, based on an arrayed waveguide grating, capable of monitoring dynamic strain in a cantilever beam at frequencies up to 5 kHz (limited by the actuator) with a similar precision to resistive strain gauges.

Hysteresis compensation for a piezoelectric fiber optic voltage sensor

We present details of numerical techniques developed to compensate the effects of hysteresis experienced by a hybrid piezoelectric fiber optic voltage sensor. The techniques, implemented using a real-time signal processing system, are tested and their effectiveness evaluated experimentally. The best of the proposed algorithms provides phase error compensation from approximately 7 to nearly 0 deg, and allows us to perform sensor calibration to achieve accuracy better than 0.5% (full scale output).

A Method of Detecting Heartbeat Locations in the Ballistocardiographic Signal From the Fiber-Optic Vital Signs Sensor

We present a flexible, easy-to-expand digital signal processing method for detecting heart rate (HR) for cardiac vibration signals of fiber Bragg grating (FBG) sensor. The FBG-based method of measuring HR is possible to use during the magnetic resonance imaging procedure, which is its unique advantage. Our goal was to design a detection method with plurality of parameters and to subject these parameters to genetic algorithm optimization technique. In effect, we arrived at a method that is well able to deal with much distorted signals with low SNR. We proved that the method we developed allows automatic adjustment to the shape of the waves of signal carrying useful information about the moments of heartbeat. Thus, we can easily adapt our technique to the analysis of signals, which contains information on HR, from sensors employing different techniques of strain detection. The proposed method has the capabilities of analyzing signals in semi-real-time (online) with beat-to-beat resolution, significantly low delay, and negligible computational power requirements. We verified our method on recordings in a group of seven subjects. Verification included over 6000 heartbeats (82 min 47 s of recordings). The root-mean-square error of our method does not exceed 6.0 bpm.

Preliminary Results of the LF/HF Ratio as an Indicator for Estimating Difficulty Level of Flight Tasks

INTRODUCTION The main aim of this study was to differentiate the magnitude of a pilots heart rate variability (HRV) when performing assisted and unassisted flights, as well as simple and complex flight tasks. METHODS Cardiac monitoring in flights was carried out using a compact, mobile ECG recorder. A frequency analysis of the heart rate (HR) signal was performed to determine the ratio of low-frequency spectral power (LF) to high-frequency spectral power (HF). RESULTS The LF/HF ratio observed in the zone (M=1.047, SD=0.059) was significantly different than the LF/HF calculated preflight (M=0.877, SD=0.043) and postflight (M=0.793, SD=0.037). There was no main effect of the flight type (unassisted zone flight vs. zone flight with an instructor) on the LF/HF parameter. However, greater psychophysiological load of a pilot was observed in the training zone flights when compared to simple circle flights (main effect of the flight type). CONCLUSIONS As the LF/HF ratio turned out to be significantly higher in the zone than pre- and postflight, this parameter can be useful for predicting the risk of excessive stress and arousal of pilots during flights. Based on the LF/HF ratio we can also estimate difficulty level of flight tasks, because our research has shown higher values of this parameter in the training zone flights than in simple circle flights.