Full-polarization Faraday magnetic field sensor based on Sagnac interference system and modulation method

Abstract

The invention discloses a full-polarization Faraday magnetic field sensor based on a Sagnac interference system and a modulation method. The full-polarization Faraday magnetic field sensor comprises alight source, an optical fiber coupler, a polarizer, a polarization beam splitter, a polarization controller, a magnetic field sensing unit, a detector and a polarization maintaining optical fiber. Alight signal is emitted by light source, and passes through an optical fiber coupler and a polarizer in sequence, and is divided into a clockwise path and an anticlockwise path by a polarization beamsplitter. A polarization controller and a polarization maintaining optical fiber ring are respectively arranged in the two light paths. Included angles between the fast axis directions of the two polarization maintaining optical fiber rings and the polarization direction of the polarizer are respectively clockwise 45 degrees and anticlockwise 45 degrees. The two polarization maintaining optical fiber rings are opposite in winding direction and equal in diameter and number of turns so as to counteract errors caused by the Sagnac effect. The magnetic field sensing unit is mainly composed of a coupling lens, a magnetic flux concentrator and a magneto-optical crystal, an external magnetic field influences the polarization state of an optical signal, and measurement of the magnetic field can be achieved by detecting the polarization interference result of the output optical signal.

Description

technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a fully polarized Faraday magnetic field sensor and a modulation method based on a Sagnac interference system. Background technique [0002] With the advancement of science and technology and the development of society, magnetic field measurement technology has occupied an increasingly important position in all aspects of scientific research and production and life, from mineral detection and medical equipment in the civilian field to anti-submarine warfare and auxiliary navigation in the military field. The requirements for magnetic field sensors are becoming increasingly stringent, and high precision, digitization, and miniaturization have become new trends. [0003] Traditional magnetic field sensors convert magnetic field signals into electrical signals for measurement, but they are easily disturbed by environmental electromagnetic fields, and the accuracy of th...

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Problems solved by technology

[0006] In order to solve the defects of poor stability and low detection accuracy of the existing magnetic field sensors, the present invention combines the Sagnac interference system with high stability and high precision and the magneto-optical crystal with high magneto-optical coefficient, and proposes a method based on Sagnac interference The fully polarized Faraday magnetic field sensor and modulation method of the system adopts an independent linearly polarized light transmission method, and performs specific modulation on the linearly polarized light transmitted on the fast axis (or slow axis) of the polarization-maintaining fiber through the polarization controller, and passes through the magnetic field sensing unit Afterwards, the polarization state of the linearly polarized light changes and polarization interference occurs at the output end, and the polarization state change is directly obtained by detecting the light intensity, thereby obtaining the information of the external magnetic field

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