Effect of Faraday mirror imperfections in a fiber optic current sensor dedicated to ITER

Abstract

Plasma current measurements in ITER are safety-related and must therefore satisfy a very demanding specification. In this paper, the use of the Fiber Optics Current Sensor (FOCS) operating in the reflection mode with a Faraday mirror to perform plasma current measurements is analyzed. Based on the Jones matrix formalism, we performed numerical simulations to investigate the impact of the Faraday mirror detuning on the measurement accuracy. We show that the use of standard commercial components does not allow to satisfy the ITER requirements for the whole plasma current range. A simple solution to the problem is proposed, which consists in taking into account a mirror calibration in the current estimator. We show that the achievable mirror calibration accuracy is sufficient to fulfill the ITER requirements.

Influence of Imperfect Faraday Rotation Mirror on All-Fiber Optic Current Sensor

“…is the uncertain angle from π/4 rad. The range of Δθ T is usually from −0:5 deg to 0:5 deg for commercial products [10]. The number of turns of sensing fiber is 100, and the Verdet constant is 1:1 × 10 −6 rad/A.…”

“…As a potential substitute for the traditional electromagnetic current transformer in power industry, the all-fiber optic current sensor (AFOCS) has many advantages, e.g., immunity against electromagnetic interference, high sensitivity, wide dynamic range, measuring AC and DC simultaneous, light weight, and small size [6,7]. Due to these intrinsic advantages, AFOCS has been widely used in many electric current measurement fields, such as the electrolytic aluminium industry [8], high voltage direct current transmission system [9], international thermonuclear experimental reactor [10], and ship leakage current measurement [11].…”

Abnormal handling mechanism and improvement measures of optical DC current transformer in smart grid environment

“…All-FOCT generally use two beams of polarized light that are always transmitted in two orthogonal modes on the same sensing fiber, and in the sensing fiber, the two beams of circularly polarized light are transmitted at different speeds due to the Faraday magneto-optical effect of the magnetic field generated by the current in the wire, resulting in the Faraday phase difference ( Karabulut et al, 2019 ; Wu et al, 2021 ; Mihailovic & Petricevic, 2021 ). Therefore, the two beams carrying the Faraday effect phase information will interfere at the starter and then be coupled by the 3 dB coupler into the photodetector, and the interferometric light intensity information arriving at the photodetector is equationed as…”