CN101504447B - Double-digital closed-loop optical fiber magnetometer for implementing working point control and magnetic zeroing feedback - Google Patents

Abstract

The invention discloses an even-number closed loop optical fiber magnetometer for achieving working point control and magnetism return-to-zero, which comprises a light source drive circuit, a light path sensing unit, a photoelectric conversion unit, an A/D conversion unit, a digital signal processing unit, a D/A conversion unit and the like, wherein the light path sensing unit comprises a DFB laser, a three-port optical circulator, an integrated optical phase modulator and the like, and has simple structure; the digital signal processing unit various control time sequences, low-frequency modulation square wave and a synchronous clock of a high-frequency sine modulation signal, completes relative demodulation of low-frequency phase drift and generates compensation phase shift digital quantity, secondarily demodulates a signal subjected to relative demodulation of the low-frequency phase drift to generate the magnetic field signal feedback quantity, forms the even-number closed loop detection, achieves the stable control and magnetism return-to-zero feedback of an interferometer orthogonal working point, improves the anti-jamming capability and the stability of the system, expands the dynamic range of measuring, and improves the sensitivity for measuring the magnetism.

Description

Realize the even numbers word closed-loop optical fiber magnetometer that working point control and magnetic make zero and feeds back

Technical field

The present invention relates to a kind of weak magnetic survey technology, relate in particular to a kind of even numbers word closed-loop optical fiber magnetometer of realizing that working point control and magnetic make zero and feeds back.

Background technology

Along with the development of science and technology and society, the weak magnetic survey technology in the application in fields such as national defense construction, national economy and biomedicine more and more widely.

In military field, along with the development of various countries' submarine noise reduction technology, traditional sonar is visited to dive and can not have been satisfied the needs of modern antisubmarine war, and various non-sound are visited the focus that the technology of diving becomes various countries' research.Magnetic anomaly detection is considered to target classification and improves the reliable means of attacking resolution to diving, and sensitive magnetic all is housed on present nearly all advanced anti-submarine patrol aircraft visits instrument.

Space magnetic field is one of space environment important physical parameter, the variation of space magnetic field reflects the notable feature that space environment changes, the high precision flux-gate magnetometer is carried on Aerospace Satellite as load in the world, carry out the monitoring of a series of spaces and terrestrial magnetic field, attitude of carrier measurement and the plan of controlling.Aspect geophysics, the terrestrial magnetic field is the intrinsic resource of the earth, for Aeronautics and Astronautics, navigation provide natural reference frame.Geomagnetic field measuring is the important means of navigation, geomagnetic method mine locating and earthquake forecast.Also there is important application directional tool and continuous inclinometer, the detection of subsea cable and the aspects such as independent navigation on identification and harbour naval vessel of weak magnetic survey in biological magnetic field and medicine equipment, petroleum pipe line nondestructive examination, petroleum drilling in addition.

At present, traditional Weak magentic-field sensor has fluxgate type magnetometer, proton precession magnetometer, optically pumped magnetometer and superconductive quantum interference magnetometer (SQUID) etc.Compare with traditional weak magnetic survey instrument, based on the interference-type optical fiber magnetometer of magnetostriction principle have highly sensitive, response speed fast, alternating current-direct current magnetic field all can be surveyed, volume is little, in light weight, advantages such as cost is low, anti-electromagnetic interference (EMI), can under the mal-condition that traditional magnetic measurement apparatus such as strong electromagnetic, High Temperature High Pressure, atomic radiation, inflammable and explosive, chemical corrosion can't be worked, use.

Optical fiber Weak magentic-field sensor of the prior art has multiple scheme: as based on the fibre optic magnetic field sensor of Fabry-Perot interferometer, based on the fibre optic magnetic field sensor of Mach-Zehnder interferometer, based on fibre optic magnetic field sensor of Michelson interferometer etc.

As shown in Figure 1, the optical fiber Weak magentic-field sensor based on the Michelson interferometer comprises laser instrument LD, optoisolator ISO, photo-detector PD, faraday rotation mirror FRM, phase-modulator PZT etc.Adopt the catoptron in the faraday rotation mirror FRM replacement traditional Michelson fibre optic interferometer, can guarantee that the back light of interferometer two arms keeps identical polarization state, solve the polarization decay problem that exists in the general single mode fiber interferometer basically.

There is following shortcoming at least in above-mentioned prior art:

Introduce faraday rotation mirror FRM in the light path and eliminated the polarization decay phenomenon, but also introduced bigger reflecting background in the light path simultaneously, the light wave input/output terminal need add two optoisolator ISO to be eliminated, and complex structure, sensitivity are low; In addition, adopt PZT phase-modulator and faraday rotation mirror to be unfavorable for the miniaturization of light channel structure; Traditional optical fibre magnetometer adopts the analog closed-loop detection scheme, and system's antijamming capability is relatively poor.

Summary of the invention

The purpose of this invention is to provide the make zero even numbers word closed-loop optical fiber magnetometer of feedback of a kind of simple in structure, highly sensitive realization working point control and magnetic.

The objective of the invention is to be achieved through the following technical solutions:

The even numbers word closed-loop optical fiber magnetometer that realization working point control of the present invention and magnetic make zero and feeds back, comprise the sensing optical path unit, it is characterized in that, described sensing light path unit pack is drawn together laser instrument, interferometer, be connected with optical circulator between described laser instrument and the interferometer, described optical circulator is provided with first port, second port, the 3rd port;

The light wave that described laser instrument sends enters described interferometer through described first port, second port successively;

The interference signal of described interferometer output is through described second port, from described the 3rd port output.

As seen from the above technical solution provided by the invention, the even numbers word closed-loop optical fiber magnetometer that realization working point control of the present invention and magnetic make zero and feeds back, owing to be connected with optical circulator between laser instrument and the interferometer, effectively reduce the reflecting background that exists in the interferometer, simple in structure, highly sensitive.

Description of drawings

Fig. 1 is based on the optical fiber Weak magentic-field principle of sensors figure of Michelson interferometer in the prior art;

Fig. 2 realizes the make zero theory diagram of even numbers word closed-loop optical fiber magnetometer of feedback of working point control and magnetic for the present invention;

Fig. 3 is signal demodulation part synoptic diagram among the present invention;

Fig. 4 is the signal waveform synoptic diagram in the digital signal processing unit different step among the present invention;

The control timing figure that Fig. 5 produces for emulation of the present invention;

Fig. 6 is the generation process flow diagram of control timing among the present invention.

Embodiment

Realization working point control of the present invention and magnetic make zero the feedback its preferable embodiment of even numbers word closed-loop optical fiber magnetometer be, comprise the sensing optical path unit, described sensing light path unit pack is drawn together laser instrument, interferometer, be connected with optical circulator between described laser instrument and the interferometer, described optical circulator is provided with first port, second port, the 3rd port;

The light wave that described laser instrument sends enters described interferometer through described first port, second port successively;

The interference signal of described interferometer output is through described second port, from described the 3rd port output.

The input/output port of described interferometer is connected with the integrated optics phase-modulator;

After the light wave of described second port output is input to described integrated optics phase-modulator, be divided into two-way output, and enter two arms of described interferometer respectively;

The light wave that two arms of described interferometer return interferes at described integrated optics phase-modulator place, and interference signal is inputed to described second port.

Two arms of described interferometer adopt thin footpath polarization maintaining optical fibre to make respectively, and the end of described two arms forms catoptron by plated film.

Two arms of described interferometer are respectively signal arm, reference arm, and described signal arm is provided with magnetostrictive transducer.

Described laser instrument is a distributed feedback semiconductor laser.

The present invention also comprises photoelectric conversion unit, preposition amplification filtering unit, A/D converting unit, digital signal processing unit, D/A converting unit;

Pass through described photoelectric conversion unit, preposition amplification filtering unit, A/D converting unit successively from the interference signal of described the 3rd port output, input to described digital signal processing unit, and handle back output by described digital signal processing unit;

Described digital signal processing unit is by the solenoid-activated unit interactive information of described D/A converting unit and described integrated optics phase-modulator and described magnetostrictive transducer.

Described digital signal processing unit comprises that control timing produces part, digital correlation test section, feedback signal generation part;

Described digital signal processing unit produces the low frequency modulations square wave, and this low frequency modulations square wave put on described integrated optics phase-modulator, produce in described control timing under the control of part, by described digital correlation test section demodulation low frequency phase drift, produce the compensating phase shift digital quantity, with after-applied in the integrated optics phase-modulator after the above-mentioned low frequency modulations square wave stack, realize the stable control of interferometer quadrature working point through D/A converter and simulated cushioned amplifier.

Described interferometer is Mach-Zehnder interferometer or Michelson interferometer;

When described interferometer was the Mach-Zehnder interferometer, the amplitude of described low frequency modulations square wave was Corresponding integrated optics phase-modulator is introduced between interferometer two arms

Modulation voltage during phase shift;

When described interferometer was the Michelson interferometer, the amplitude of described low frequency modulations square wave was

Corresponding integrated optics phase-modulator is introduced between interferometer two arms

Modulation voltage during phase shift.

Control timing generating unit branch in the digital signal processing unit sends the synchronous clock of high-frequency modulation signal, produces synchronous high frequency modulated magnetic field by high frequency Sine Modulated field generator for magnetic;

The secondary correlation demodulation is carried out to the signal after the described low frequency phase drift demodulation in described digital correlation test section, obtain and treat the proportional phase information of measuring magnetic field, and generation feedback signal, feedback signal and the stack of bias magnetic field digital quantity are after after D/A and the amplifier, output to the solenoid-activated unit with the high frequency sinusoidal modulation signal by the totalizer stack and feed back to described magnetostrictive transducer.

The effect of bias magnetic field is to guarantee that magnetostriction materials are operated in the sensitiveest zone;

Demodulation is carried out to the described signal of measuring magnetic field for the treatment of in described digital correlation test section, under the control of described control timing, by described feedback signal, realizes that the clean D.C. magnetic field in the transducer is zero, i.e. the magnetic feedback that makes zero.

The present invention adopts optical circulator to replace original optoisolator on light channel structure, has effectively suppressed the reflecting background that exists in the interferometer; Adopt the integrated optics phase-modulator to replace original coupling mechanism and PZT phase-modulator, improved the signal to noise ratio (S/N ratio) of light path output, realized the full fiberize and the miniaturization of light channel structure; Sensor fibre adopts polarization maintaining optical fibre, and the optical fiber connector plated film replaces faraday rotation mirror, has avoided the polarization inducement signal fading problem that exists in the general single mode fiber sensor-based system; Adopt even numbers word closed loop detection technique to realize stable control and " magnetic makes zero " feedback of interferometer quadrature working point simultaneously, improved the antijamming capability and the stability of system, enlarged the dynamic range of measuring, improved the survey magnetic sensitivity.

Simultaneously, further simplify light channel structure, when guaranteeing the light path performance, more helped the design requirement of system's miniaturization.On detection scheme, the present invention adopts the digital correlation detection technique, has realized even numbers word closed loop detection scheme, has solved the random drift of interferometer working point and the hysteresis effect of material, improve the detection sensitivity and the stability of system, enlarged range of dynamic measurement.

The concrete method of the stable control of interferometer quadrature working point and " magnetic makes zero " feedback is among the present invention:

The control of interferometer quadrature working point:, in light path, introduce by on phase-modulator (Y waveguide), adding the low-frequency square-wave modulation signal The biasing phase place, because the existence of low frequency phase drift, interferometer output signal becomes square-wave signal by cosine response, the amplitude of square-wave signal has reflected the size of low frequency phase drift, square-wave signal is as the error signal of working point FEEDBACK CONTROL, under the control of corresponding time sequence, the other side's wave error signal carries out correlation demodulation one time, obtain the size of low frequency phase drift, produce compensating phase shift, feed back to light path, offset low frequency phase drift by phase-modulator, make interferometer always work in the sensitiveest zone, realize the stable control of interferometer working point.

The magnetic feedback that makes zero: because the measuring object of optical fiber Weak magentic-field sensor is direct current and low frequency low-intensity magnetic field signal, in order to avoid low-frequency noise, improve signal to noise ratio (S/N ratio), generally on magnetostrictive transducer, add the high frequency modulation, to change to high frequency modulated frequency and sideband thereof on low frequency and the D.C. magnetic field signal, utilize the response squared of magnetostriction materials,, can obtain treating measuring magnetic field as long as detect the fundamental component amplitude of interferometer output signal medium-high frequency modulating frequency to externally-applied magnetic field.Based on this principle, treat that the digital correlation detection technique is still adopted in the demodulation of measuring magnetic field, under the control of corresponding time sequence, the interference signal through the low-frequency square-wave modulation is carried out twice coherent detection continuously, can demodulate measured signal; Produce feedback signal by certain algorithm, guarantee that the clean D.C. magnetic field in the transducer is zero, realize the magnetic feedback that makes zero.

Specific embodiment, as shown in Figure 2:

Comprise light source driving circuit, sensing optical path unit, preposition amplification filtering unit, photoelectric conversion unit, A/D converting unit, digital signal processing unit, modulation signal generating unit, D/A converting unit, solenoidal driver element etc.Wherein:

The sensing optical path unit mainly comprises DFB (distributed feed-back) laser instrument, three port photocirculators, integrated optics phase-modulator (Y waveguide), magnetostrictive transducer.

Concrete sensor mechanism is: under the control of light source driving circuit, the light wave that Distributed Feedback Laser sends, enter first port one of optical circulator, the light that comes out from second port 2 of optical circulator is through integrated optics phase-modulator (Y waveguide), the inclined to one side function that rises by Y waveguide becomes linearly polarized light, be divided into two then, enter two arms of interferometer, signal arm transmission light causes additional phase error through magnetostrictive transducer, after the mirror reflects of sensor fibre end, pass through transducer once more, signal phase doubles, and the light that returns with reference arm interferes after Y waveguide closes light, and the interference light signal that carries Magnetic Field to be measured arrives the 3rd port 3 through second port 2 of circulator, receive by photodetector assembly PIN-FET, be converted into voltage signal.

Distributed Feedback Laser is a narrow linewidth semiconductor laser; Three port photocirculators are polarization irrelevant single-mode fiber device, light wave enters from first port one of circulator, can only arrive second port 2, the light wave that enters from second port 2, can only arrive the 3rd port 3, played the effect of optoisolator, reduced in the interferometer because the reflecting background that FP chamber effect and Rayleigh scattering produce; Integrated optics phase-modulator (Y waveguide) has the function of the polarizer, coupling mechanism and phase-modulator simultaneously, because the optical fibre magnetometer in this programme is based on the principle of polarized light interference, therefore an inclined to one side analyzing function of Y waveguide can improve the signal to noise ratio (S/N ratio) of interferometer output, in addition, Y waveguide replaces coupling mechanism, the polarizer and three devices of phase-modulator simultaneously, simplify light channel structure, helped system's miniaturization Design; Y waveguide is the polarization maintaining optical fibre device, and interferometer two arms also adopt polarization maintaining optical fibre, and two arm optical fiber connector plated films replace faraday rotation mirror, has avoided the problem of polarization inducement signal decline in the general single mode fiber sensor-based system; Photodetector assembly PIN-FET is the single-mode fiber device, and interference light signal is changed into current signal earlier, and current signal changes into voltage signal and amplifies back output.

The voltage signal of photoelectric conversion unit output carries out amplification filtering through pre-amplification circuit, improves the signal to noise ratio (S/N ratio) that enters the A/D converter input signal.Interferometer output signal through the pre-amplification circuit conditioning is converted into digital signal by A/D converter, enters digital signal processing unit.

Digital signal processing unit is the core of whole detection system, comprises that generation part, digital correlation test section, the feedback signal of control timing produces part, digital efferent grades.

As shown in Figure 3, the function of digital signal processing unit mainly is to produce the low frequency modulations square wave, and the modulation methods wave frequency is chosen in a certain frequency outside the signal bandwidth; Adopt digital correlation detection method demodulation low frequency phase drift, produce compensating phase shift, realize the stable control of interferometer quadrature working point; Simultaneously the signal after the low frequency phase drift correlation demodulation is carried out the secondary correlation demodulation, obtain and treat the proportional phase information of measuring magnetic field, produce feedback signal, feed back to transducer by solenoid, solve the hysteresis effect of magnetostriction materials, simultaneously demodulation result is exported.

As shown in Figure 4, be the signal waveform synoptic diagram in the digital signal processing unit different step, among the figure: (a) be low frequency modulations square wave (Y waveguide); (b) be high frequency modulated sine wave (solenoid); (c) be interferometer output signal; (d) be low frequency phase drift demodulation sampling pulse; (e) be low frequency demodulation square wave h (t); (f) be the low frequency phase drift demodulation result; (g) be high-frequency signal demodulation square wave r (t); (h) be high-frequency signal demodulation sampling pulse SYRCC; (i) be the high-frequency signal demodulation result.

According to the relevant rotating model of Livingston, when surveying magnetic field hour, external magnetic field causes being changed to of phase of light wave in the sensor fibre:

$\mathrm{\Δ\φ}=C_{\mathrm{eff}}{H}_T^2---\left(1\right)$

In the formula: C _EffBe effective magnetostriction coefficient; H _TBe added total magnetic field on the transducer.

If D.C. magnetic field to be measured is H ₀, the high frequency modulated magnetic field that applies on transducer by solenoid is H _ωCos ω t, then the total magnetic field on the transducer is:

H _T＝H ₀+H _ωcosωt (2)

The output signal of the interferometer that detector receives is:

I＝A+Bcos[2(Δφ _s+φ _M)]

＝A+Bcos(2φ _FB+φ ₀+φ ₁cosωt+φ ₂cos2ωt)

In the formula: A is the constant relevant with luminous power; B=vA, v are the visibility of interference signal, 0≤v≤1;

φ _FBBe the low-frequency square-wave modulation signal outside the signal bandwidth that adds on the Y waveguide, the phase signal amplitude of introducing at this is

Low frequency phase drift for the environmental perturbation generation;

φ ₁＝4C _effH ₀H _ω；

${\mathrm{\φ}}_2=C_{\mathrm{eff}}{H}_{\mathrm{\ω}}^2.$

Hence one can see that, adds on transducer after the high frequency modulation, treats that measuring magnetic field is included in φ ₁In, and proportional with it, φ ₁=4C _EffH ₀H _ω, a demand gets φ ₁Just can obtain to treat measuring magnetic field.

Because interferometer output signal is a cosine function, be nonlinear response when surveying little phase signal, and sensitivity is not high, for making interferometer work in the sensitiveest zone, need add a phase bias, changes cosine signal into sinusoidal signal.

Therefore, add just like the square-wave modulation signal shown in Fig. 4 (a) by the integrated optics phase-modulator among the present invention, square-wave modulation signal is introduced between interferometer two arms

Phase shift because light path adopts the Michelson interferometer structure, twice of interferometer two arms transmission light wave is through phase-modulator, like this, the phase differential of introducing between the final two-beam ripple that participates in interfering is

Interference signal changes sinusoidal response into by cosine response, and interferometer is operated in the sensitiveest zone when surveying little phase signal, and its output is approximately linear relationship, and can distinguish the symbol of signal.Interferometer after the square-wave frequency modulation is output as:

$I({\mathrm{\&phi;}}_0,+\frac{\mathrm{\&pi;}}{4})=A-B\sin ({\mathrm{\&phi;}}_0+{\mathrm{\&phi;}}_1\cos \mathrm{\&omega;t}+{\mathrm{\&phi;}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="H2009100773884E00022.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})---\left(3\right)$

$I({\mathrm{\&phi;}}_0,-\frac{\mathrm{\&pi;}}{4})=A+B\sin ({\mathrm{\&phi;}}_0+{\mathrm{\&phi;}}_1\cos \mathrm{\&omega;t}+{\mathrm{\&phi;}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="H2009100773884E00022.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})---\left(4\right)$

The sensitivity of interferometric optical fiber sensor is high, but is vulnerable to the influence of environmental perturbation simultaneously, introduce the random phase drift because

Existence, interferometer departs from the quadrature working point, and interferometer output signal changes along with the variation of low frequency phase drift, even can complete obiteration, the phase fading phenomenon promptly occurs.When having low frequency phase drift, after the square wave modulation, interferometer output signal becomes square-wave signal, the high frequency cosine ripple signal that superposeed on the square wave, interferometer output signal as shown in Figure 4 (c).

Among the present invention, adopt the digital correlation detection technique from the square wave error signal after the modulation, to demodulate low frequency phase drift, and produce compensating phase shift, feed back in the light path by phase-modulator by certain algorithm, offset the influence of low frequency phase drift, make interferometer come back to the quadrature working point.Specific as follows:

The demodulation square wave (e) that is produced by control timing as shown in Figure 4 is as the reference square-wave signal in the correlation demodulation, under the effect of sampling pulse YRCC, shown in Fig. 4 medium and low frequency phase drift demodulation sampling pulse (d), A/D is transformed digital signal afterwards selectively enter full adder, finish the data accumulation of square wave error signal semiperiod;

Then, as shown in Figure 5, under the control of demodulated pulse YYCC, the data sum of the positive and negative half period of square wave error signal is subtracted each other, finish the digital correlation demodulation of low frequency phase drift, produce the digital quantity D of feedback phase shift step simultaneously _Nfb, shown in Fig. 4 medium and low frequency phase drift demodulation result (f); The effect of pulse YYRAC is, the data accumulation of demodulation semiperiod before full adder is finished (square wave semiperiod), and send into after next demodulation module, with the full adder zero clearing, carry out adding up of next semiperiod data.

The digital quantity of feedback phase shift step is carried out numeral with the modulated square wave signal add up, under the control of D/A sequential YDA, be converted into analog voltage signal, be added on two electrodes of phase-modulator the formation closed loop through behind the simulated cushioned amplifier.The effect of this digital closed loop is to offset the additional noise phase shift that environmental perturbation is introduced between interferometer two arms transmission light wave, and the quadrature working point of stablizing interferometer makes it always work in the sensitiveest zone, erasure signal fade-out, the stability of raising system.

Introduce below and adopt twice digital correlation demodulation to obtain the process of high-frequency signal continuously:

The generation synoptic diagram of control timing as shown in Figure 6, the generation unit of control timing is the major part of digital signal processing unit, control timing has determined the flow process of signal demodulation.

The interferometer output signal of realizing stabilization of operating point control is:

$I(+\frac{\mathrm{\&pi;}}{4})=A-B\sin ({\mathrm{\&phi;}}_1\cos \mathrm{\&omega;t}+{\mathrm{\&phi;}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="H2009100773884E00022.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})---\left(5\right)$

$I(-\frac{\mathrm{\&pi;}}{4})=A+B\sin ({\mathrm{\&phi;}}_1\cos \mathrm{\&omega;t}+{\mathrm{\&phi;}}_2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="H2009100773884E00022.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&omega;t})---\left(6\right)$

The present invention adopts double coherent detection to finish the extraction of high-frequency signal, and the sampling pulse that adopts in this twice coherent detection is SYRCC, shown in Fig. 4 medium-high frequency signal demodulation sampling pulse SYRCC (h).Under the control of sampling pulse SYRCC, optionally digital signal and low frequency demodulation square-wave signal after the A/D conversion are multiplied each other, data after will multiplying each other then multiply each other with high frequency demodulation square wave again, send into full adder then, under the control of demodulated pulse SYYCC, finish the correlation demodulation of high-frequency signal, produce the magnetic feedback signal that makes zero, shown in Fig. 4 medium-high frequency signal demodulation result (i).Feedback signal is converted into simulating signal under the control of clock SYDA, by the D.C. magnetic field to be measured on the solenoid counteracting transducer, finish another close-loop feedback.The effect of this closed loop is that to keep the clean D.C. magnetic field in the transducer be zero, eliminates the hysteresis effect of material and because the magnetic noise that hysteresis effect produces, improves the accuracy of detection and the stability of system, enlarges the dynamic range of measuring.

Control timing produces the synchronous clock of a high-frequency modulation signal in the digital signal processing unit, and synchronous clock control high-frequency modulation signal generating means produces synchronous high frequency Sine Modulated field signal;

For guaranteeing that magnetostriction materials are in the sensitiveest zone, digital signal processing unit is when producing the feedback magnetic field digital quantity, a bias magnetic field digital quantity superposes, through simulating stack with the high frequency sinusoidal modulation signal behind D/A converter and the simulated cushioned amplifier, by the solenoid-activated unit, feed back to magnetostrictive transducer;

Adopt two isolators of optical circulator replacement light input/output port in the light path of the present invention, reduced the reflecting background of light path; The integrated optics phase-modulator has had partially simultaneously, beam split and phase modulation (PM) function, adopt the integrated optics phase-modulator to replace photo-coupler and PZT phase-modulator, improve the signal to noise ratio (S/N ratio) of interferometer output signal, realized the full fiberize of light channel structure, helped the miniaturization Design of system.

The present invention adopts the digital correlation detection technique, finished even numbers word closed loop design, the stable control of interferometer quadrature working point and effective inhibition of material hysteresis effect have been realized simultaneously, effectively improve the signal to noise ratio (S/N ratio) of system output signal, enlarged the range of dynamic measurement of system, improve the survey magnetic sensitivity and the long-time stability of system, helped promoting the practicability of optical fiber Weak magentic-field sensor.

The present invention is directed to existing Michelson interfere type polarization irrelevant optical fiber Weak magentic-field sensor, on light path, carried out optimal design, the combination of adopting optical circulator to add the integrated optics phase-modulator has replaced the array mode that two optoisolators, coupling mechanism in the former scheme add the PZT phase-modulator, and increase the function of the polarizer, improve the signal to noise ratio (S/N ratio) of light path output, helped the design requirement of system's miniaturization;

Integrated optics phase-modulator and interferometer two arms adopt polarization maintaining optical fibre among the present invention, dfb semiconductor laser instrument, optical circulator and PIN-FET photodetector assembly adopt the single-mode fiber device, when taking into account cost and performance, avoided the polarization decay problem in the single-mode fiber sensor-based system;

The present invention adopts the digital correlation detection technique, invented even numbers word loop detector, realize the stable control of interferometer quadrature working point and effective inhibition of magnetostriction materials hysteresis effect, improved the survey magnetic sensitivity and the stability of system, enlarged the range of dynamic measurement of system;

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims (3)

1. One kind realize working point control and magnetic make zero the feedback even numbers word closed-loop optical fiber magnetometer, comprise the sensing optical path unit, it is characterized in that, described sensing light path unit pack is drawn together laser instrument, interferometer, be connected with optical circulator between described laser instrument and the interferometer, described optical circulator is provided with first port, second port, the 3rd port;

   The light wave that described laser instrument sends enters described interferometer through described first port, second port successively;

   The interference signal of described interferometer output is through described second port, from described the 3rd port output;

   The input/output port of described interferometer is connected with the integrated optics phase-modulator;

   After the light wave of second port output of described optical circulator is input to described integrated optics phase-modulator, be divided into two-way output, and enter two arms of described interferometer respectively;

   The light wave that two arms of described interferometer return interferes at described integrated optics phase-modulator place, and interference signal is inputed to second port of described optical circulator;

   Two arms of described interferometer are respectively signal arm, reference arm, and described signal arm is provided with magnetostrictive transducer;

   This magnetometer also comprises photoelectric conversion unit, preposition amplification filtering unit, A/D converting unit, digital signal processing unit, D/A converting unit, simulated cushioned amplifier;

   Pass through described photoelectric conversion unit, preposition amplification filtering unit, A/D converting unit successively from the interference signal of described the 3rd port output, input to described digital signal processing unit, and handle back output by described digital signal processing unit;

   Described digital signal processing unit is by the solenoid-activated unit interactive information of described D/A converting unit and described integrated optics phase-modulator and described magnetostrictive transducer;

   Described digital signal processing unit comprises that control timing produces the generation part of part, digital correlation test section, feedback phase shift;

   Described digital signal processing unit produces the low frequency modulations square wave, produce in described control timing under the control of part, demodulate low frequency phase drift by described digital correlation test section, produce the compensating phase shift digital quantity, and after the compensating phase shift stack with this low frequency modulations square wave and low frequency phase drift, put on described integrated optics phase-modulator through described D/A converting unit and simulated cushioned amplifier, realize the stable control of interferometer quadrature working point;

   Described interferometer is Mach-Zehnder interferometer or Michelson interferometer;

   When described interferometer was the Mach-Zehnder interferometer, the amplitude of described low frequency modulations square wave was

   

   Corresponding integrated optics phase-modulator is introduced between interferometer two arms

   

   Modulation voltage during phase shift;

   When described interferometer was the Michelson interferometer, the amplitude of described low frequency modulations square wave was

   

   Corresponding integrated optics phase-modulator is introduced between interferometer two arms

   

   Modulation voltage during phase shift;

   Control timing in the described digital signal processing unit produces the synchronous clock that part produces high-frequency modulation signal, produces synchronous high frequency Sine Modulated field signal by high frequency Sine Modulated field generator for magnetic;

   The secondary correlation demodulation is carried out to the signal after the described low frequency phase drift demodulation in described digital correlation test section, obtains and treat the proportional phase information of measuring magnetic field, and produces feedback signal;

   Described digital signal processing unit is when producing the feedback magnetic field signal, a bias magnetic field digital quantity superposes, behind described D/A converting unit and simulated cushioned amplifier, superpose by totalizer with described high frequency Sine Modulated field signal, output to described solenoid-activated unit, and feed back to described magnetostrictive transducer;

   Demodulation is carried out to described field signal to be measured in described digital correlation test section, produces in described control timing under the control of part, by described feedback signal, realizes that the clean D.C. magnetic field in the transducer is zero, i.e. the magnetic feedback that makes zero.
2. 2. the even numbers word closed-loop optical fiber magnetometer that realization working point control according to claim 1 and magnetic make zero and feeds back is characterized in that, two arms of described interferometer adopt thin footpath polarization maintaining optical fibre to make respectively, and the end of described two arms forms catoptron by plated film.
3. 3. the even numbers word closed-loop optical fiber magnetometer that realization working point control according to claim 1 and magnetic make zero and feeds back is characterized in that described laser instrument is a distributed feedback semiconductor laser.

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