Patent ID: 11906603
Assignee: SHANGHAI UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A system for measuring a magnetorefractive effect of an optical fiber, comprising a laser (1), a coupler A (2), a sensing optical fiber (3), a reference optical fiber (4), a carrier generator (5), a coupler B (6), a photoelectric detector (7) and a data acquisition and processing module (8), wherein
an output port of the laser (1) is connected with a first port (21) of the coupler A (2), a second port (22) of the coupler A (2) is connected with a first port (31) of the sensing optical fiber (3), and a third port (23) of the coupler A (2) is connected with a first port (41) of the reference optical fiber (4); a second port (32) of the sensing optical fiber (3) is connected with a second port (62) of the coupler B (6), and a second port (42) of the reference optical fiber (4) is connected with a third port (63) of the coupler B (6); a first port (61) of the coupler B (6) is connected with an input port of the photoelectric detector (7); an input port of the data acquisition and processing module (8) is connected with an output port of the photoelectric detector (7), the optical signal output by the laser (1) being divided into two beams of light transmitted by the sensing optical fiber (3) and the reference optical fiber (4) through the coupler A (2), the two beams of light interfering with each other at the coupler B (6), and the intensity of the interference optical signal being detected by the photoelectric detector (7);
the sensing optical fiber (3) is arranged in a magnetic field environment and used for modulating a magnetic field signal into a refractive index signal; and
the carrier generator (5) is formed by winding piezoelectric ceramic on the reference optical fiber (4), and the piezoelectric ceramic is connected with signal generators and used for generating phase carrier signals;
during direct-current magnetic field measurement, a direct-current magnetic field is applied to the sensing optical fiber (3), wherein the magnetic field changes the refractive index of the sensing optical fiber (3), so that the optical path difference of optical signals in the sensing optical fiber (3) and the reference optical fiber (4) is changed, the output interference optical signal intensity of the coupler B (6) is changed, the interference light intensity is converted into interference voltage by the photoelectric detector, and the refractive index change of the sensing optical fiber (3) under the action of the direct-current magnetic field is measured by detecting the interference voltage; and
during alternating-current magnetic field measurement, an alternating-current magnetic field is applied to the sensing optical fiber (3), and a phase carrier signal is applied to the reference optical fiber (4) through the carrier generator (5), wherein the coupler B (6) outputs the interference optical signal modulated by the alternating-current magnetic field, the interference optical signal is converted into an interference voltage signal by the photoelectric detector (7), the interference voltage signal is acquired to the data acquisition and processing module, and data processing is carried out on the interference voltage signal to restore phase change caused by the magnetorefractive effect of the sensing optical fiber (3); and
aiming at direct-current magnetic field measurement, according to the interference voltage detected under each magnetic field, the corresponding refractive index of the sensing optical fiber (3) under the magnetic field is calculated through an interference formula, and the refractive index change measurement of the sensing optical fiber (3) under the action of the direct-current magnetic field is realized; and aiming at alternating-current magnetic field measurement, the interference voltage signal and the fundamental frequency carrier signals and the frequency doubling carrier signals are respectively mixed to obtain two paths of mixing signals, the high-frequency signals in the two paths of mixing signals are filtered by the low-pass filters to obtain two paths of filtering signals, differential cross multiplication operation on the two paths of filtering signals are carried out to obtain a first path of signals and a second path of signals, and a subtraction operation, integral operation and band-pass filtering are sequentially carried out on the first path of signals and the second path of signals to obtain phase change caused by the magnetorefractive effect of the optical fiber, and the refractive index change measurement of the sensing optical fiber (3) under the action of the alternating-current magnetic field by demodulating the phase is realized.