Pawel Niewczas

A Fiber-Bragg-Grating-Based Sensor for Simultaneous AC Current and Temperature Measurement

In this paper, a sensor that is capable of measuring both ac current and temperature using a single fiber Bragg grating (FBG) is described. The device consists of a magnetically biased magnetostrictive alloy bonded to an FBG. The magnetic field generated by the current in a specially designed coil produces internal strains in the magnetostrictive alloy which can be detected by the FBG. The temperature at the sensing point is determined through averaging of the sensor output signal. The measurement range of the sensor can be varied by altering the design of the sensor coil. A prototype sensor that is capable of measuring ac currents up to 1 A has been constructed while simultaneously measuring temperatures of up to 100 degC

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.

Temperature compensation for optical current sensors

An analysis of an optical current transducer (OCT) considering in particular the influence of temperature induced variations in the Verdet constant is presented. The analysis is supported by an experimental evaluation of a prototype OCT over a range of operating temperatures and current values and concludes with a laboratory demonstration of a temperature compensation scheme that improves the measurement precision to better than 0.7%.

A fibre Bragg grating based sensor for simultaneous AC current and temperature measurement

In this paper, we describe a sensor capable of measuring both AC current and temperature using a single fibre Bragg grating (FBG). The device consists of a magnetically biased magnetostrictive alloy bonded to an FBG. The magnetic field generated by the current in a specially designed coil produces internal strains in the magnetostrictive alloy which can be detected by the FBG. The temperature at the sensing point is determined through averaging of the sensor output signal. The measurement range of the sensor can be varied by altering the design of the sensor coil. A prototype sensor has been constructed capable of measuring AC currents up to 1 A while simultaneously measuring temperatures up to 100/spl deg/C.

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.

High-Speed, Solid State, Interferometric Interrogator and Multiplexer for Fiber Bragg Grating Sensors

We report on the design and prototyping of a robust high-speed interferometric multiplexer and interrogator for fiber Bragg grating sensors. The scheme is based on the combination of active WDM channel switching and passive, instantaneous interferometry, allowing the resolution of virgin interferometric interrogators to be retained at MHz multiplexing rates. In this article the system design and operation are described, and a prototype scheme is characterized for three sensors and a multiplexing rate of 4 kHz, demonstrating a noise floor of 10 nε/√Hz and no cross-sensitivity. It is proposed that the system will be applicable to demanding monitoring applications requiring high speed and high resolution measurements across the sensor array.

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.

Magnetic cross-talk compensation for an Optical Current Transducer

In this paper we analyse the errors associated with magnetic cross-talk within point type, or unlinked, Optical Current Transducers (OCTs) working in the three-phase electric current transmission systems. It is shown that, for most practical conductor arrangements, the magnetic cross-talk is sufficient to introduce errors unacceptable for the accuracy requirements demanded front the OCT. A solution to this problem is devised around a unique compensation method which solves, in real time, a set of linear equations, each representing the instantaneous output signal from one phase current sensor. The equations are created using calibration factors which can be evaluated for the particular conductors arrangement using experimental or analytical methods. The solution of the above set of equations may be implemented using Digital Signal Processing (DSP), which provides the number of sought instantaneous values of currents in the considered conductors arrangement.

Effects of Neutron-Gamma Radiation on Fiber Bragg Grating Sensors: A Review

Fiber Bragg grating (FBG) sensing is currently one of the leading measurement technologies, but has made only minor inroads into nuclear diagnostics due, for the most part, to insufficient proof of survivability in these environments. This paper aims to review the current knowledge in this area, incorporating reviews of radiation-induced darkening of silica, shifts in Bragg peak, and changes to mechanical properties, while taking into account core/cladding chemistry, structure, and coating materials. In doing so, this review not only highlights the achievements of the scientific community up to the present, but more importantly, the key areas in which knowledge is still lacking and further concentrated investigation would be beneficial.