<title>Polygonal Faraday effect current sensor with polarization-preserving dielectric mirrors</title>

Abstract

A new type of Faraday effect current sensor consisting of a single SF57 glass block having dielectric multilayer mirrors coated to have polarization-preserving perfect reflection and containing no parasitic field sensitive parts is developed. A good isolation froffi the external current and field is demonstrated.

Linearization of chromatic change in a polychromatic current transformer

“…To completely enclose the conductor, it is therefore necessary for light to make a minimum of two reflections around the conductor; this type of configuration has no magnetic circuit and is completely optical. Alternatively, the Faraday element may be placed within the gap of a magnetic field concentrator with sensitivity being increased via multiple reflections [1], [12]. Although the use of a magnetic concentrator introduces a compromise in terms of the possibility of saturation it reduces costs related to sensing medium material volume.…”

“…For a Faraday sensor, the output polarization state may be described using Jones matrices where the relation between input and output field vectors is where is the Jones matrix representing the combined optical elements. For a sensor employing reflections, this may be written as (11) This may be extended so that the definition includes the effects of crossed polarizers, the quartz rotator (wavelength encoding element), and Faraday rotator, so that (12) where…”

Fiber Optic Sensors Based on the Faraday Effect

“…Current sensing differs from magnetometry because it is necessary to suppress all the magnetic field sources but one, a conductor, the current of which we wish to measure. This can be achieved in two ways: by a closed optical loop around the conductor [ 72 , 73 , 74 ], (a) and (b) in Figure 2 , or by a magnetic ring concentrator encircling the conductor [ 35 , 75 , 76 , 77 ], (c) in Figure 2 . FR and current are connected through Ampere’s law.…”

Sensitivity improvement of an optical current sensor with enhanced Faraday rotation

“…For practical optical current sensors, their Faraday rotation angle is usually limited to 2 to satisfy the high sensitivity requirements of the power industry [19] and as a result they should have a reasonably small reflection-induced polarization distortion. Note also that such a distortion is generally very small for well designed optical current sensors where precautions are often taken for its reduction or even elimination [30]. Consequently, the analytical formulation of device sensitivity from (12) to (14) should be applicable approximately to practical devices.…”