Sensitivity improvement of an optical current sensor with enhanced Faraday rotation

The Faraday effect optical magnetic field sensor has broad application prospects in power systems, and the temperature stability of the sensor has always been the focus of research. Existing researches mostly focus on the influence of temperature on the Verdet constant of the magneto-optical material, but there are other temperature factors that are not taken into account, which limits the improvement of the temperature stability of the sensor. In this paper, the effect of magneto-optical crystal (TGG) temperature on the optical rotation coefficient and static operating point of the sensor’s sensing function was studied. It was found that the crystal temperature has a significant effect on the optical rotation coefficient and static operating point in the sensing function. The optical rotation coefficient and static operating point fluctuate periodically with the change of crystal temperature. Through the theoretical analysis of the influence mechanism of temperature, it was found that the interference of multiple reflected light in the magneto-optical crystal has a significant influence on the optical rotation coefficient and static operating point. The mechanism of temperature affecting the sensing function was proposed: temperature affects the phase of reflected light through thermo-optical effect and thermal expansion effect, changes the interference state of reflected light, and then affects the optical rotation coefficient and static operating point. Quantitative calculations were carried out on the influence of temperature using the theoretical model. The calculation results are in good agreement with the experimental data. This article provides a theoretical basis for the optimal design of such sensors.

Section: Introductionmentioning

confidence: 99%

Research on the influence of temperature on the sensing function of Faraday effect optical magnetic field sensor

Li¹,

Wen²,

Fan³

et al. 2022

“…OCSs have several advantages over conventional CTs, such as non-contactness, good insulation, insensitivity to electromagnetic interference, large dynamic range, high-speed measurements and operation in harsh environments. A popular configuration of OCSs is to use bulk glass as a magnetic field sensor and an air-gapped core surrounding the conductor as a field concentrator [3,4]. The major advantages of this type of OCSs are simple structure, low cost and fast response.…”

Section: Introductionmentioning

confidence: 99%

Magneto-optical electric-current sensor with enhanced sensitivity

Chu

Chiang

2002

In this design note, an air-gapped ring core type Faraday-effect optical current sensor using a new sensing element design is described. The sensing element is a finely polished glass prism with highly reflective coatings on the two end surfaces, which is designed in such a way that the light beam propagating through it undergoes 20 critical-angle reflections at the glass-air interfaces. The current sensitivity of this new design is almost three times higher than that of a previous design based on a similar principle.

“…Examples of bulk glass sensor configurations of novel design include a glass loop [1][2][3][4] whereby the current-carrying conductor passes through the centre of the glass, the path traversed by the light totally enclosing the conductor being in accordance with Ampère's circuital law B = H dl. Another form utilizes a linear glass block within a gap in an iron ring used to concentrate the B field produced by a current-carrying conductor passing through its centre [5][6][7]. These bulk sensors involve the multiple reflection of light within the sensor element and such reflections affect the polarization state of the light in addition to any Faraday-rotation-induced effects.…”

Section: Introductionmentioning

confidence: 99%

Elliptical polarization effects in a chromatically addressed Faraday current sensor

Li¹,

Aspey²,

Kong³

et al. 1999

Optical polarization processes in a parallel-sided glass element used in a Faraday rotation current sensor have been considered. In such sensors the path length necessary to produce sufficient rotation of the plane of polarization is produced by a multiplicity of reflections within the glass element. It is shown that such reflections induce ellipticity of polarization and that this affects the current-sensing performance of the sensor. Two reflection cases, corresponding to total internal reflections at a glass-air interface and reflections by aluminium-coated surfaces, are considered. The latter are shown to produce higher optical attenuation but a lower degree of elliptical polarization. The implications of the induced elliptical polarization in relation to chromatically modulated polychromatic light are considered. It is shown that the resolution of the Faraday sensing is improved by minimizing the ellipticity of the polarization with the aluminium-coated reflections. However a greater dynamic range and signal strength may be achievable with the total internal reflection element.