SU1130808A1 - Magnetic optical teslameter - Google Patents

Abstract

1. A magneto-optical teslameter containing a two-frequency laser, a beam splitter, two optical filters, two photodetectors, a magneto-optical probe consisting of a Farade cell and two quarter-wavelength devices, two fibers connected to a magneto-optical probe, characterized in that, in order to improve the measurement accuracy, A second beam splitter, two optical mixers, a third and a fourth light guide fibers and a phase meter, the first laser output through the first optical filter and the first beam splitter Through two optical fibers with opposite inputs of the magneto-optical probe, the first output of which through the third light guide and the first input of the first optical mixer is connected to the input of the first photodetector, the second output of the probe through the fourth light guide and the first input of the second photodetector, the second laser output through the second optical filter is optically connected to the input of the second beam splitter, the first output of which through the reflector is connected to the second input of the first mixer, the second the output of the second beam splitter is connected to the second input of the second mixer, and the outputs of the photodetectors are connected to the inputs of the differential phase meter. 2. A magneto-optical teslameter containing a two-frequency laser with opposite circular polarizations of the radiation component, two optical filters, two photodetectors, a magneto-optical probe, and The two optical fibers connected to the magneto-optical probe, which are different from the cell, are designed so that, in order to improve the measurement accuracy, differential phase meters and third and fourth optical fibers are introduced into it, and the outputs of the laser through two optical fibers are connected the inputs of the magneto-optical probe, the first and second outputs of which through the third and fourth light guides and optical filters are optically coupled to the inputs of the first and second photodetectors, respectively, the outputs of which are connected to the inputs of the differential phase meter.

Description

The invention relates to magnetic measurements and can be used to measure the magnetic induction of a constant magnetic field. A magneto-optical teslameter is known, containing a sequentially connected light source, a modulator, a polarizer-analyzer in the form of a Plan-Thompson prism, a Farade cell, a reflector, a beam splitter, two photodetectors, a synchronous detector and a recording device And, The disadvantages of the teslameter are a narrow dynamic measuring range due to the low modulation frequency that a mechanical modulator is capable of providing, as well as insufficient accuracy limited by low-frequency oscillations of the radiation intensity of the source The closest technical solution to the predicted one is a magneto-optical teslameter containing a source of light in the form of a two-frequency laser, a beam splitter, two optical (| Iltra, two photodetectors, a magneto-optical probe consisting of a Farade cell and two quarter-wave plates, two a fiber connected to a magneto-optical probe and a bridge circuit, the inputs of which are connected to the outputs of photodetectors zj. The disadvantages of the known teslameter are the high sensitivity to changes in transmittance otopriemnikov and to change parameters Faraday cell, which limits the accuracy of the order of magnitude of 0.3%. The purpose of the invention is to improve the measurement accuracy. The goal is achieved by the fact that, in a magneto-optical teslameter containing a two-frequency laser, a beam splitter, two optical filters, two photodetectors, a magneto-optical probe consisting of a Farad cell and two quarter-wave plates, two fibers connected to a magneto-optical probe, a second beam splitter, two an optical mixer, a reflector, a third and fourth optical fibers, and a differential phase meter, the first laser output through the first optical filter and the first optical beam splitter optically connected to the two optical fibers On the opposite inputs of the magneto-optical probe. the first output of which 4pt; ri is the third light guide and the first input of the first optical mixer connected to the input of the first photodetector, the second output of the probe through the fourth light guide and the first input of the second optical mixer connected by the input of the second photodetector, the second output of the laser through the second optical filter is optically connected with the input of the second beam splitter, the first output of which through the reflector is connected to the second M input of the first mixer, the second output of the second beam splitter is connected to the second input of the second mixer, and the outputs of the photodetectors connected to the inputs of the differential phase meter. The goal is also achieved by the fact that a magneto-optical teslameter containing a two-frequency laser with opposite circular polarization radiation component, two optical filters, two photodetectors, a magneto-optical probe consisting of a Farad cell, two fibers connected to a magneto-optical probe, are introduced a difference phase meter and a third and fourth light guide, the laser outputs being connected via two light guides to the inputs of a magneto-optical probe, the first and second outputs of which are through the third and fourth light guide and optical filters optically coupled to the inputs of the first and second photodetectors, respectively, whose outputs are connected to inputs of the differential phase meter. FIG. 1 shows a magneto-optical teslameter diagram, the first option; in fig. 2 - the same, the second option. The teslameter contains a dual-frequency laser I, the first output of which is through the first optical filter 2 and first of the beam splitter 3, where the beam is divided into two, optically coupled to two optical fibers 4 and 5, by means of which two opposite beams are fed to the magneto-optical probe 6; The magnet optical probe 6 consists of two quarter-wave plates 7 and 8 and a Farad cell 9. The outputs of the magneto-optical probe 6 through the optical fibers 10 and P are connected to the first inputs of optical mixers 12 and 13, from the output of which the rays are fed to the inputs of photodetectors 14 and 15. The second output of laser I is through the second optical filter 16, the second beam splitter 17 and the reflector 18 optically is connected with the second inputs of the optical mixers 12 and 13. The folded beams arrive at the photodetectors 14 and 15, the outputs of which are connected to the inputs of the differential phase meter 19.

In the second variant, the magneto-optical teslameter contains a two-frequency laser 1 and an optical filter.

2. The outputs of the laser 1 through the optical fibers 4 and 5 are fed to the inputs of the magneto-optical probe 6 consisting of a Farad cell 9. The outputs of the magneto-optical probe through the optical fibers 10 and 11 and optical filters optically connected to the inputs of the corresponding photodetectors 14 and 15, while

An optical filter 16 is connected to the input of the photoreceiver 14. The outputs of the photoreceivers 14 and 15 are connected to the inputs of the differential phase meter 19, the output of which is the information output of the device.

The teslameter (Fig. L) works as follows.

Laser 1 generates two-mode radiation, which is two linearly polarized mutually orthogonal waves, the frequency difference of which can be set in interCO

shaft 10-10 Hz. Naturally, conventional measures are taken to ensure the stability of the radiation characteristics (stabilization of frequencies and power). . The beam from the first output of laser 1 passes an optical filter 2, which also, like filter 16, can simply be an analyzer that passes one of the two orthogonal modes and hits the beam splitter

3, which is, for example, a translucent mirror. On delimiter 3, the first laser beam is split into two beams, which

using the light guides 4 and 5, they are led to opposite sides of the magneto-optical probe 6 and form a pair of opposing rays. The rays passing through the magneto-optical probe 6 are transmitted through the optical fibers 10 and 11 to the optical mixers 12 and 13, respectively, which, like the beam splitter 17, can be made in the form of translucent mirrors. The beam from the second output of laser 1 passes through the second optical ({illtr 16 and eg a08084

It is located at the beam splitter 17, where the beam is divided into two. One of the separated rays is fed to the optical mixer 12, and the second through the reflector 18 to the optical mixer 13. The reflector 18 may be, for example, a blind mirror or a prism of total internal reflection. The filter 16 selects Qet a second mode, which on optical mixers 12 and 13 is mixed with the opposing rays of the first mode. These mixed beams fall on the photodetectors 14 and 15, respectively, where they are converted into an electrical beat signal.

Phase meter 19 selects the phase difference between two electrical signals of the same frequency. When the device is turned on, the magneto-optical probe 6 is shielded and the initial value of the phase shift is set, for example, zero. When a magneto-optical probe 6 is placed in a magnetic field, an optic appears. the chests path difference of the opposing rays, which leads to a phase shift

wed 2VdB. where V is constant Verde;

d is the thickness of the active layer of the Farade cell;

B - magnetic induction. In this case, the following occurs in the magneto-optical probe. A linearly polarized beam, having traversed a quarter-wave plate, acquires a circular polarization. The rotation of the plane of polarization due to the effect .. Farad., The oncoming beam has different signs, acceleration of one beam and brake of the second. Having passed the second quarter-wave plate, the beam again becomes linearly polarized. The intensity of the beam at the output of the light guide 10 is described by the expression

5, b) 4cf D) 4 q, oli) ipelt) q (B) l,

where is the radiation frequency;

Cf, (t) is a random phase caused by laser instability 1 {

(li HlHtp lt) - random phases caused by instabilities of the optical shield in the corresponding optical fibers from influencing factors (temperature, pressure, etc.);

CSj, (t) -cause phase, due to the influence of external factors on the magneto-optical probe 6; CP (B) phase increment due to the Farad effect. The intensity of the beam at the output of the fiber I1 is described by the expression I ,, a ,, 46ttVt 6Wvcp ,, (t) -4 (B), where the trial is the initial value of the phase difference of the opposing rays, due to different optical paths; CpyCt) and Cf ,, (t) are random phases. The intensity of the beam at the output of the splitter 17 is equal to /, t + (i (t) (3) where Cp, (t) is a random phase corresponding to the instability of the second mode; 2 the emission frequency of the second mode. The intensity of the beam at the output of the reflector 18 is 1 , 2, 0,2sinfrt + fi b M; (where (horn is the initial value of the phase difference of the separated beams of the second mode) At the output of the photodetector 15 there will be a signal V, a, 6; n (,, lt) 4cf (t) Cf, git) +% W + tf (Bl-tp2W, (5) at the output of the photodetector 14 M2 ajSin (-3i-2Vtvq, (, tCf5 (t)) +% W-4 tebtp7W-4oOSb) at the output of the phase meter 19, (t) + c, o (t) -46W 4 "(t) (8 () 2Ч (8), 4o% 2-% oq with Wt), U) 4Cf, (t) -q, 5 (t)). Magneto-optical teslameter (FIG 2) works as follows Laser I is an isotropic Zeeman laser, the rays from the outputs of which are polarized in a circle.At the same time, the beam coinciding with the direction of the magnetic field consists of two components, -6, where is the frequency of the laser without a magnetic field; A - - laser frequency shift caused by the Zeeman effect: the first component has right circular polarization, and the second, left. On the second pin of laser 1, the radiation component with a frequency of -0 has the left circular polarization, and the component with the frequency is right-handed. Passing through the Farad правой cell, the radiation components with right and left circular polarizations receive phase increments with opposite signs. Optical filters 2 and 16, which are from themselves, for example, simply analyzers, are extracted from. the radiation transmitted by the optical fibers through the Farad cell, the interfering components of the radiation, which at the corresponding photodetectors 14 and 15 are converted into electrical signals of the difference frequency. A phase meter 19 measures the phase difference of two electrical signals of the same frequency. The basic relationships are as follows. The intensity of the beam at the output of the optical filter consists of two components and 1.2 which are described by the following expressions: I ,, a ,, 5; n, l + t, U) 4 (, (tl4c 6aHty ,,);, i, rci ,, sin -32iitp2W4 (iH4; Ubcp; jt) -cf {B): where C, (t) and cp2 (t) are random phases due to instability of the parameters of laser 1; q4 W, tfi 1.4-6 W, 4-6 W a% (t} (t) are random phases due to the influence of external factors on the optical fibers 4 and 11 and probe 6 with respect to the first component; (|| (c) - phase increment due to the Farad effect. The intensity of the beam at the input of the optical filter 16 consists of components 12J and which are described by the expressions I ,, a2, btf, lt,), Porqle)) l22 a2. ,, ltl4lf (t) 4C | itlf4 i (tlt.), where and cf (32 are the initial phases of the components of the second laser output relative to the phases of the corresponding components of the first 1a, 1 laser output 1. The signal at the output of the I5 photodetector is V, a; 5; "(, 4cp, U ) -7 |, (ihq) (i) -cf (t) ... / | Л) | Ъ / IIt ,. I / i. . and ..I% W - (,, (t) -cf;, (i) 42 (f Ol, (10) 7 13 SIGNS1 on and, at the photo input of the 14, has the form M, j (V 2litc, li) + 4 ) (tl-cf5lt)) - tt4feli) -4UtUtp, U) (i) fq ,,, (.. (The phase difference, separated by phase meter 19, is described by the expression i 4-tPo2-c, t4ltl4 - nW 4 ,, (t ) + 45 - 5W 4loW-4, aUl44tf (B) (o4q, t) 4cf (8l where the initial phase difference of the phases; (j ,, (t) is a random component due to the nonentical change in the optical paths in the optical fibers under the influence of external factors. The dynamic range of the prearranged devices is determined by the carrier frequency (differential frequency of the radiation. In this case, the upper frequency of the change of the magnetic field must be by one or two orders of magnitude ni7 ";. f carrier frequency Predpagaemy magneto teslametr allows to expand the measurement range and improve the performance compared with the serial -According tes-, Lamettrie GW1 -1 performance increases by more than 2 times..

Ajnru

fig 2

Claims (2)

1. A magneto-optical teslameter containing a two-frequency laser, a beam splitter, two optical filters, two photodetectors, a magneto-optical probe, consisting of a Faraday cup and two quarter-wave plates, two optical fibers connected to a magneto-optical probe, characterized in that, in order to increase the accuracy of measurements, a second beam splitter is introduced; two optical mixers, a reflector, a third and fourth optical fiber with an azometer, the first laser output through the first optical filter and the first beam splitter optically coupled through two optical fibers with opposite inputs of the magneto-optical probe, the first output of which through the third optical fiber and the first input the first optical mixer is connected to the input of the first photodetector, the second output of the probe through the fourth fiber and the first input of the second, optical mixer is connected to the input of the second photodetector, the second output EPA through the second optical filter is optically coupled with the input of the second beamsplitter, - a first outlet through which reflector is connected with the second input of the first mixer, the second output of the second splitter is connected to a second input of the second mixer, and the outputs of the photodetectors are connected to the inputs of the differential phase meter. 2. A magneto-optical teslameter containing a two-frequency laser with opposite circular polarizations of the radiation components, two optical filters, two photodetectors, a magneto-optical probe, consisting of a Faraday cage, two optical fibers connected to a magneto-optical probe, characterized in that, in order to increase the measurement accuracy , a difference phase meter and a third and fourth optical fiber are introduced into it, and the laser outputs through two optical fibers are connected to the inputs of the magneto-optical probe, the first and second outputs of which are through the third and h tverty fiber and optical filters optically coupled to the inputs of the first and second photodetectors, respectively, whose outputs are connected to inputs of the differential phase meter.