Intrinsic, multiplexable sensors for electric field strength using structural slow light in phase-shifted fibre Bragg gratings

In this paper we demonstrate through simulation the potential for phase-shifted fibre Bragg gratings incorporating structural slow light to enable intrinsic reflection-mode point sensors for electric field or voltage. It is shown that lo-bi FBGs incorporating multiple phase shifts yield large enhancements in group index (group delay) at resonance, thus amplifying and localizing time-dependent non-reciprocal effects. A relative, multiplexable measurement of electric field by comparison of the phase unbalance between linear modes on and off resonance is proposed, yielding static resolutions of 24 V and 18 mV respectively in unpoled (dc Kerr effect) and poled (Pockels effect) fibres

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

Concept level evaluation of the optical voltage and current sensors and an arrayed waveguide grating for aero-electrical system applications

In this paper we present, for the first time, the hybrid fiber-optic voltage and current sensors interrogated using an arrayed waveguide grating (AWG) device. Due to the excellent dynamic capabilities of an AWG-based interrogator and its improved robustness, the proposed system would be suitable for voltage and current monitoring within an aircraft electrical system. The voltage sensor comprises a multilayer piezoelectric stack, acting as a voltage-to-strain transducer, and a fiber Bragg grating (FBG) used to convert voltage induced strain changes within the stack into wavelength shifts. These wavelength shifts are then analysed by an AWG. To measure current, the same sensor type is used to monitor a specially designed ferrite-core current transformer. It is shown that the system is capable of measuring variable frequency of voltage and current waveforms, typical of those anticipated in the next generation aero-electric power systems. It is also demonstrated that the system can be used for voltage and current harmonic analysis and power quality measurement in such networks

Temperature characterisation of an optically-interrogated Rogowski coil

An investigation into the performance of an optically-interrogated Rogowski coil over temperatures up to 80 °C is presented. Preliminary thermal tests reveal that the sensor response is temperature-dependent and the measurement errors are increased at higher temperatures. Compensation of temperature effects is, therefore, necessary in order for the sensors to meet the requirements of protection and metering classes specified by relevant IEC standards over the considered operating temperature range. This can, however, only be achieved when the utilised sensor interrogator is adapted to ensure sufficient resolution and accuracy from a generally low-output transducer. As such, the design of a new multiplexing, interferometric interrogation platform is also proposed in this paper

Interferometric time division FBG interrogator and multiplexer with static, dynamic, and absolute wavelength measurement capabilities

We report on the design and preliminary testing of an interferometric interrogator capable of large-scale time-division multiplexing of FBG sensors. The scheme employs a passive algorithm for phase demodulation, allowing changes in FBG sensor reflected wavelengths to be calculated instantaneously upon arrival, and incorporates a technique for identification of initial absolute sensor wavelengths in order to overcome the measurement ambiguity associated with interferometric schemes. The proposed system will allow for high-speed interrogation of large-scale FBG sensor arrays with interferometric resolution and the capability for dynamic, static, and absolute FBG wavelength measurement

Pion production within the hybrid relativistic plane wave impulse approximation model at MiniBooNE and MINERvA kinematics

The hybrid model for electroweak single-pion production (SPP) off the nucleon, presented in [Gonz\'alez-Jim\'enez et al., Phys. Rev. D 95, 113007 (2017)], is extended here to the case of incoherent pion-production on the nucleus. Combining a low-energy model with a Regge approach, this model provides valid predictions in the entire energy region of interest for current and future accelerator-based neutrino-oscillation experiments. The Relativistic Mean-Field model is used for the description of the bound nucleons while the outgoing hadrons are considered as plane waves. This approach, known as Relativistic Plane-Wave Impulse Approximation (RPWIA), is a first step towards the development of more sophisticated models, it is also a test of our current understanding of the elementary reaction. We focus on the charged-current $\nu$($\bar\nu$)-nucleus interaction at MiniBooNE and MINERvA kinematics. The effect on the cross sections of the final-state interactions, which affect the outgoing hadrons on their way out of the nucleus, is judged by comparing our results with those from the NuWro Monte Carlo event generator. We find that the hybrid-RPWIA predictions largely underestimate the MiniBooNE data. In the case of MINERvA, our results fall below the $\nu$-induced 1$\pi^0$ production data, while a better agreement is found for $\nu$-induced 1$\pi^+$ and $\bar\nu$-induced 1$\pi^0$ production.Comment: 13 pages, 10 figure

Solid-state interferometric interrogator and multiplexer for high-speed dynamic and absolute FBG wavelength measurement

We present a solid-state FBG array interrogator and multiplexer capable of determining absolute FBG wavelengths and of providing high-speed, high-resolution static and dynamic measurements. Using a described procedure, deployable on multiplexing passive-interferometric schemes, the system is able to determine initial sensor wavelengths and thereafter track wavelength changes with interferometric resolution. The scheme allows high-resolution interrogation of FBG sensor arrays to be applied to many industrial applications, where previously the lack of combined absolute and quasi-static wavelength measurement precluded the use of interferometric techniques. Using a preliminary laboratory embodiment, we demonstrate a wavelength determination accuracy of <0.3 nm and a measurement resolution of 10 fm/√Hz, and propose pathways to improved performance and miniaturisation

All-optical differential current detection technique for unit protection applications

In this paper we demonstrate a novel, all-optical differential current protection scheme. By monitoring the optical power reflected from two matched hybrid fiber Bragg grating current sensors and using a simple optoelectronic threshold detector, an immediate response to an increase in differential current is achieved. A preliminary laboratory embodiment is constructed in order to characterize the performance of the scheme. The proposed technique does not require a complex sensor interrogation scheme, usually characterized by a limited sampling frequency, and thus will be capable of facilitating inexpensive and fast-acting differential protection over long distances

High-speed interferometric FBG interrogator with dynamic and absolute wavelength measurement capability

A passive, interferometric wavelength demodulation technique has been extended to measure the absolute wavelengths of a multiplexed array of fiber Bragg grating sensors. The scheme retains its original strain resolution of 10 nε/√{Hz}. A proof-of-concept interrogation system was able to determine the absolute wavelength of Bragg peaks to within 20 pm (17 με). Static and dynamic Bragg grating strains were accurately demodulated in both absolute and relative wavelength measurement modes. This demonstration indicates that interferometric techniques are able to provide absolute, static and dynamic measurements of strain within a single platform