CN102788595A - Optical fiber gyroscope frequency characteristic elevating method and device based on Faraday effect - Google Patents
Optical fiber gyroscope frequency characteristic elevating method and device based on Faraday effect Download PDFInfo
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Abstract
The invention discloses an optical fiber gyroscope frequency characteristic elevating device based on a Faraday effect. An excitation current source comprises a signal generator, a conversion amplifying circuit and a current coil, wherein a sensitive light path comprises a light source, a circulator, a Y waveguide phase regulator, a polarization beam splitter, a polarization-maintaining fiber coil, a gamma/4 wave plate, a sensing optical fiber, a reflecting mirror and a detector; and an analog optical fiber gyroscope signal processing detection circuit comprises a front amplifying circuit, an A/D (Analog to Digital) converting circuit, a digital signal processing unit, a first D/A (Digital to Analog) converting unit, a second D/A converting circuit and a phase-locked amplifier. The Faraday effect applied in the invention is generated by exciting the sensitive light path with sinusoidal current, and a sinusoidal signal serving as an exciting signal can be output at a high frequency, so that the problem of limitation on the excitation signal output frequency during frequency characteristic test of an optical fiber gyroscope is solved, and evaluation of high bandwidth can be realized.
Description
Technical field
The present invention relates to a kind of optical fibre gyro frequency characteristic appraisal procedure and device, belong to the inertial technology field based on the Faraday effect.
Background technology
Optical fibre gyro is along with optical fiber technology develops rapidly and a kind of novel optical fiber rotation sensor of occurring; Because having the practicality of high sensitivity and exquisite and high mechanical properties, its phase modulation (PM) sensing mode will become the inertia member that has development prospect in the numerous areas such as space flight, aviation, navigation most; As a kind of important inertial sensor; Measuring the angular velocity of carrier, is the core devices that constitutes inertia system, has determined the performance of whole inertia system on the certain degree.
Outstanding advantages such as optical fibre gyro is based on the novel angular-rate sensor of Sagnac effect, and structure of whole solid state, the dynamic range with no-rotary part is big, bandwidth is big, low in energy consumption, anti shock and vibration, little, the no start-up course of volume, life-span are long.
Along with the middle low-precision optical fiber gyro successful Application these years and the raising of optical device performance, the high-precision optical fiber gyro that development is used for inertial navigation system becomes a development trend.The method of testing of optical fibre gyro is restricting the raising of optical fibre gyro precision to a certain extent.The dynamic perfromance of optical fibre gyro is the important performance indexes that characterizes its reliability and environmental suitability, and its quality has directly determined the range of application of gyro, and wherein, frequency-response analysis is the pith of dynamic perfromance.
Digital closed-loop optic fiber gyroscope is the major programme of middle high-precision optical fiber gyro, is representing international and domestic research direction.For reliability and the environmental suitability that improves optical fibre gyro; Improve the tracking characteristics of closed loop; The researchist of optical fibre gyro makes great efforts to improve dynamic perfromance through the control algolithm of improving close-loop feedback always, and the index that reaction improves dynamic perfromance is that the frequency characteristic enhancing is that bandwidth increases.
Traditional optical fibre gyro dynamic characteristic test method is to adopt plant equipment such as hang-up table and angle vibration table to measure the step response curve and the frequency response curve of gyro respectively.When adopting angle vibration table test gyro bandwidth, angle vibration table is with the angular speed motion of sinusoidal alternating, and it can provide the angular speed of different frequency, different amplitudes.Optical fibre gyro is born the sinusoidal signal input of different frequency, writes down corresponding input angle vibration amplitude and phase place, and the measuring optical fiber gyro is exported the amplitude and the phase place of signal, just can obtain the frequency characteristic of optical fibre gyro.
Owing to general angle vibration table designs to mechanical gyro; The output angle vibration frequency is general only has 200Hz to about the 300Hz; The at present domestic maximum operation frequency scope of advanced angle vibration table the most can only reach 500Hz; But the bandwidth of optical fibre gyro far can not satisfy the requirement of digital closed-loop optic fiber gyroscope dynamic characteristic test considerably beyond 500Hz.
The semi-hardware type simulation test scheme all is on the fiber optic loop of optical fibre gyro, to add disturbing signal; The light that utilizes two bundles to propagate in opposite directions gets asynchronism(-nization) through disturbance place; Delay time T of difference; Thereby the generation phase differential, the Sagnac phase differential that has replaced input angular velocity to cause changes the frequency of disturbing signal and then measures frequency characteristic.
Be concrete implementation wherein:
Utilize PZT to apply modulation signal and realize the frequency characteristic evaluation scheme: according to the principle of work of optical fibre gyro; In the gyro fiber optic loop, introduce a PZT element; The angular speed of simulating a sinusoidal variations through the Sine Modulated that applies certain frequency to PZT; Thereby record the amplitude-frequency response of optical fibre gyro, and then confirm its bandwidth.Its structure principle chart is as shown in Figure 1.The principle of work of closed-loop fiber optic gyroscope: the light that is sent by the SLD light source is risen partially by the polarizer after through a coupling mechanism, becomes linearly polarized light and gets into the Y waveguide phase-modulator, and the place receives phase modulation (PM) at phase-modulator.Two-beam through fiber optic loop interferes, and is last, and the light that carries phase information gets into the Pin detector by coupling mechanism.The simulating signal entering A/D change-over circuit that the voltage signal to be measured that pre-amplification circuit is exported PIN/FET carries out after the amplification filtering disperses, quantizes; Convert digital signal to; Carry out the demodulation computing with the supplied with digital signal processing unit; When signal processing unit adds up the formation staircase waveform to demodulation result; Export a square-wave signal and be superimposed upon on the digital staircase waveform, superposed signal is modulated with
through the after-applied close-loop feedback that on the Y waveguide phase-modulator, realizes of D/A conversion.
Principle of work according to above closed-loop fiber optic gyroscope; In the gyro fiber optic loop, introduce a PZT element; Thereby the sine voltage signal through apply certain frequency to PZT is realized the angular speed that Sine Modulated is simulated a sinusoidal variations; Thereby record the amplitude-frequency response of optical fibre gyro, and then confirm its bandwidth.
Realize that through integrated optical modulator the digitizing dynamic testing method records the bandwidth scheme: the principle of utilizing the optical fibre gyro closed loop to detect; The required signal of superposition on the feedback staircase waveform, the Sagnac phase differential that the phase differential between the two-beam that causes with staircase waveform replaces input angular velocity to cause.It has successively proposed on the feedback staircase waveform, to add step signal, sinusoidal signal, pseudo random signal as 3 kinds of schemes of external signal.In addition; On the feedback staircase waveform, add pseudo random signal and use relative identifying method again as external signal; Digital closed loop output is carried out obtaining behind the related operation impulse response of gyro closed loop through the signal behind the wavelet filtering and pseudo random signal, obtain the amplitude versus frequency characte and the phase-frequency characteristic of gyro again through Fourier transform.Structure is as shown in Figure 2.The principle of work of closed-loop fiber optic gyroscope: the light that is sent by the SLD light source is risen partially by the polarizer after through a coupling mechanism, becomes linearly polarized light and gets into the Y waveguide phase-modulator, and the place receives phase modulation (PM) at phase-modulator.Two-beam through fiber optic loop interferes, and is last, and the light that carries phase information gets into the Pin detector by coupling mechanism.The simulating signal entering A/D change-over circuit that the voltage signal to be measured that pre-amplification circuit is exported PIN/FET carries out after the amplification filtering disperses, quantizes; Convert digital signal to; Carry out the demodulation computing with the supplied with digital signal processing unit; When signal processing unit adds up the formation staircase waveform to demodulation result; Export a square-wave signal and be superimposed upon on the digital staircase waveform, superposed signal is modulated with
through the after-applied close-loop feedback that on the Y waveguide phase-modulator, realizes of D/A conversion.
According to the principle of work of above closed-loop fiber optic gyroscope, be used for equivalent outside input angular velocity through stack sinusoidal signal on optical fibre gyro feedback staircase waveform, the gyro demodulated output signal is judged according to amplitude obtain the gyro bandwidth.
Semi-hardware type simulation test scheme key be exactly the light propagated in opposite directions of two bundles to get time difference through disturbance place be delay time T, but delay time T is generally very little, has only μ s magnitude; When measuring low frequency; The external signal frequency of adding is little, changes slowly, and variation is not obvious in the time of μ s magnitude; Because the reciprocity of optical fibre gyro light path; Disturbance when causing low frequency is not obvious to phase change, can only improve by the amplitude that increases disturbance, so be difficult for equivalent input measurement frequency characteristic in low-frequency range.
Summary of the invention
The objective of the invention is in order to address the above problem; A kind of optical fibre gyro frequency characteristic apparatus for evaluating and method based on the Faraday effect proposed; This device can the measuring optical fiber gyro full bandwidth in frequency characteristic, for the research of optical fibre gyro closed-loop control provides the checking means.In addition, can draw the closed-loop bandwidth of the optical fibre gyro of approved product, for the scope of application of optical fibre gyro environmental suitability provides foundation.
A kind of optical fibre gyro frequency characteristic apparatus for evaluating based on the Faraday effect comprises excitation current source, responsive light path and analog optical fiber gyro signal processing and detecting circuit;
Excitation current source comprises signal generator, converter amplifier circuit and current coil; Signal generator generates AC signal; AC signal exports converter amplifier circuit to, and converter amplifier circuit exchanges amplification to AC signal, exports exchange current to current coil then; Current coil is wrapped on the sensor fibre of responsive light path; Feed exchange current in the current coil, the magnetic field of generation makes the sensor fibre induction Faraday effect in the responsive light path, has realized that signal is delivered in the responsive light path by excitation current source; The exchange current of converter amplifier circuit output through a sampling resistor after, obtain sampled voltage, sampled voltage is exported to the reference port of lock-in amplifier;
Responsive light path comprises light source, circulator, Y waveguide phase-modulator, polarization beam apparatus, polarization-maintaining fiber coil, λ/4 wave plates, sensor fibre, catoptron and detector; Light source sends light, and light gets into the Y waveguide phase-modulator through behind the circulator; Play partially to receive phase modulation (PM) then for linearly polarized light at Y waveguide phase-modulator place, the polarized light after the modulation exports polarization beam apparatus to, after two tail optical fibers couplings of polarized light by polarization beam apparatus; Inject polarization-maintaining fiber coil, polarized light transmits along the X axle and the Y axle of polarization-maintaining fiber coil respectively, behind entering λ/4 wave plates; In λ/4 wave plates, polarized light becomes left-handed respectively and circularly polarized light dextrorotation, and gets into sensor fibre; The phase place of two bundle circularly polarized lights changes (F=2VNI), and wherein, F is a Faraday effect phase differential; V is the Verdet constant, and N is for twining the number of turn of lead, and I is a size of current.Two bundle circularly polarized lights transmit with different speed, export catoptron to, and after the reflection of the minute surface place of catoptron, the polarization mode of two bundle circularly polarized lights exchanges, and passes sensor fibre once more, and the phase place that two bundle circularly polarized lights are produced doubles (2F=4VNI); Two bundle circularly polarized lights revert to linearly polarized light once more through behind λ/4 wave plates, and two bunch polarized lights interfere then; The light that carries phase information gets into detector by circulator, and detector realizes that converting voltage signal into by light signal exports pre-amplification circuit to;
Analog optical fiber gyro signal processing and detecting circuit comprises pre-amplification circuit, A/D change-over circuit, digital signal processing unit, a D/A change-over circuit, the 2nd D/A change-over circuit and lock-in amplifier; Pre-amplification circuit carries out amplification filtering to the voltage signal to be measured of detector output, exports the A/D change-over circuit then to, and the A/D change-over circuit disperses, quantizes the voltage signal to be measured of simulation; Convert digital voltage signal to be measured to, export digital signal processing unit to, digital signal processing unit subtracts each other the digital signal in two adjacent time delay and carries out demodulation; Add up demodulation result and be thought of as staircase waveform; Simultaneously, the square-wave signal that on staircase waveform, superposes obtains superposed signal; Superposed signal is imported a D/A change-over circuit; The one D/A change-over circuit converts the superposed signal of numeral the superposed signal of simulation into, exports the Y waveguide phase-modulator to, realizes close-loop feedback modulation with
; Simultaneously; Digital signal processing unit also exports demodulation result to the 2nd D/A change-over circuit, and the 2nd D/A change-over circuit converts the digital demodulation result into the analog demodulator result, and the signalling channel port that exports lock-in amplifier to is measured; Lock-in amplifier is measured amplitude and phase differential size, has realized the frequency characteristic assessment.
A kind of optical fibre gyro frequency characteristic appraisal procedure based on the Faraday effect comprises following step:
Step 1: the light that is sent by light source gets into the Y waveguide phase-modulator after through a circulator, is modulated to linearly polarized light at Y waveguide phase-modulator place and receives phase modulation (PM); Polarized light injects polarization-maintaining fiber coils by two tail optical fibers coupling back of polarization beam apparatus, respectively along the X axle and the transmission of Y axle of polarization maintaining optical fibre, through behind λ/4 wave plates, becomes left-handed and circularly polarized light dextrorotation and entering sensor fibre respectively; Because the excitation exchange current produces magnetic field, in sensor fibre, produce the Faraday magneto-optic effect, make the phase place of this two bundles circularly polarized light change (F=2VNI; Wherein, F is a Faraday effect phase differential, and V is the Verdet constant, and N is for twining the number of turn of lead; I is a size of current) two bundle circularly polarized lights transmit with different speed, and after catoptron place reflection, the polarization mode of two bundle circularly polarized lights exchanges; Pass sensor fibre once more, and the phase place that experience Faraday effect produces two-beam doubles 2F=4VNI; Two-beam through behind λ/4 wave plates, reverts to linearly polarized light once more, and two bunch polarized lights interfere then; At last, the light that carries phase information gets into detector by circulator, and the light of return detector has only carried because the non-reciprocal phase that the Faraday effect produces is poor;
Step 2: the simulating signal entering A/D change-over circuit that the voltage signal to be measured that pre-amplification circuit is exported photodetector carries out after the amplification filtering disperses, quantizes; Convert digital signal to; Carry out the demodulation computing with the supplied with digital signal processing unit; When signal processing unit adds up the formation staircase waveform to demodulation result; Export a square-wave signal and be superimposed upon on the digital staircase waveform, superposed signal realizes close-loop feedback and ± pi/2 modulation through D/A change-over circuit conversion is after-applied on the Y waveguide phase-modulator; Simultaneously, through the 2nd D/A change-over circuit conversion back output, measure by the signalling channel port that gets into lock-in amplifier demodulation result output for signal processing unit; Utilize lock-in amplifier measuring-signal amplitude and phase place extent, change the frequency of exciting current signal and then realized the frequency characteristic assessment.
The invention has the advantages that:
(1) the Faraday effect of the present invention's application is to adopt sinusoidal current to encourage responsive light path to produce; Wherein the sinusoidal signal as pumping signal can realize high-frequency output; Solved the limited problem of pumping signal output frequency of the frequency characteristic test of optical fibre gyro, so can realize the assessment of high bandwidth;
What (2) adopt in this device is the sensing light path responsive to the Faraday effect, can produce the Faraday effect by better responsive electric current, has improved the signal to noise ratio (S/N ratio) of sensitive signal;
(3) circuit of this device is the signal deteching circuit of having simulated optical fibre gyro, can come the analog optical fiber gyro through forward gain in the regulating device and feedback gain, thereby realizes the accurate assessment of frequency characteristic;
(4) fiber optic loop of 4 different lengths has been installed in this device,, so just can have assessed the optical fibre gyro frequency characteristic of different length fiber optic loop, increased the applicability of this apparatus for evaluating as long as can connect fiber optic loop through wire jumper;
(5) appraisal procedure of this device is to adopt lock-in amplifier, can accurately assess the bandwidth of optical fibre gyro.
Description of drawings
Fig. 1 is the HWIL simulation schematic diagram that utilizes PZT in the background technology;
Fig. 2 is the HWIL simulation schematic diagram that utilizes integrated optical modulator in the background technology;
Fig. 3 is a structural representation of the present invention.
Among the figure:
The responsive light path 3-of 1-excitation current source 2-analog optical fiber gyro signal processing and detecting circuit
101-signal generator 102-converter amplifier circuit 103-current coil
201-SLD light source 202-circulator
204-Y Waveguide Phase Modulator 205-polarization beam apparatus 206-polarization-maintaining fiber coil
207-λ/4 wave plate 208-sensor fibre 209-catoptrons
The 210-detector
301-pre-amplification circuit 302-A/D change-over circuit 303-digital signal processing unit
304-the one D/A change-over circuit 305-the 2nd D/A change-over circuit 306-lock-in amplifier
Embodiment
To combine accompanying drawing and embodiment that the present invention is done further detailed description below.
The present invention is a kind of optical fibre gyro frequency characteristic apparatus for evaluating based on the Faraday effect, and is as shown in Figure 3, comprises excitation current source 1, responsive light path 2 and analog optical fiber gyro signal processing and detecting circuit 3.
Excitation current source 1 is realized frequency sweep for this device provides pumping signal through the frequency that changes pumping signal, accomplishes the assessment of frequency characteristic.Excitation current source 1 comprises signal generator 101, converter amplifier circuit 102 and current coil 103.
Excitation current source 1 is to adopt triode to exchange conversion to amplify.Amplifying ultimate principle is: at input signal is 0 o'clock, and amplifying circuit is being operated in magnifying state, and suitable dc point is arranged.After AC signal adds amplifying circuit, cause that base current does corresponding variation on the basis of original direct current, base current changes the variation that makes collector current thereupon become β (β is for exchanging enlargement factor), realizes the amplification of electric current.For the requirement of satisfying above AC great current output and working long hours; And elimination intermodulation distortion; Adopt the form of the push-pull type triode of the complementary symmetry of dual power supply to the pipe amplification; Realize that push-pull two triodes amplify respectively, have solved the problem of intermodulation distortion in the positive negative cycle of sinusoidal signal.
Responsive light path 2 comprises SLD light source 201, circulator 202, Y waveguide phase-modulator 204, polarization beam apparatus 205, polarization-maintaining fiber coil 206, λ/4 wave plate 207, sensor fibre 208, catoptron 209, detector 210.
SLD light source 201 sends light, light through a single mode circulator 202 after, get into Y waveguide phase-modulator 204, play partially receiving phase modulation (PM) for behind the linearly polarized light at Y waveguide phase-modulator 204 places; Polarized light after the modulation exports polarization beam apparatus 205 to, after two tail optical fiber couplings of polarized light by polarization beam apparatus 205, injects polarization-maintaining fiber coil 206, and polarized light transmits along the X axle and the Y axle of polarization-maintaining fiber coil 206 respectively; After getting into λ/4 wave plates 207, in λ/4 wave plates 207, polarized light becomes left-handed respectively and circularly polarized light dextrorotation, and gets into sensor fibre 208; Because the excitation exchange current produces magnetic field, in sensor fibre 208, produce the Faraday magneto-optic effect, make the phase place of this two bundles circularly polarized light (F=2VNI that changes; Wherein, F is a Faraday effect phase differential, and V is the Verdet constant; N is for twining the number of turn of lead, and I is a size of current), two bundle circularly polarized lights transmit with different speed; Export catoptron 209 to, after the reflection of the minute surface place of catoptron 209, the polarization mode of two bundle circularly polarized lights exchanges; Pass sensor fibre 208 once more, and experience Faraday effect, the phase place that two bundle circularly polarized lights are produced doubles (2F=4VNI).This two bundles circularly polarized light reverts to linearly polarized light once more through behind λ/4 wave plates 207, and two bunch polarized lights interfere then.At last; The light that carries phase information gets into detector 210 by single mode circulator 202; Detector 210 realizes that converting voltage signal into by light signal exports pre-amplification circuit 301 to, and the present invention has realized that through photodetector signal is by being delivered in the circuit in the responsive light path 2.
Be provided with the fiber optic loop of 4 different lengths in the described polarization-maintaining fiber coil 206; Be respectively 570m, 350m, 100m and 200m; When needs use the light ring of one of them length, the light ring of choosing is connected with polarization beam apparatus 205, λ/4 wave plates 207 respectively through wire jumper, form polarization-maintaining fiber coil 206; So just can assess the optical fibre gyro frequency characteristic of different length fiber optic loop, increase the applicability of this apparatus for evaluating.
Analog optical fiber gyro signal processing and detecting circuit 3 comprises pre-amplification circuit 301, A/D change-over circuit 302, digital signal processing unit 303, a D/A change-over circuit 304, the 2nd D/A change-over circuit 305 and lock-in amplifier 306.
The voltage signal to be measured of 301 pairs of detectors of pre-amplification circuit, 210 outputs carries out amplification filtering; Export A/D change-over circuit 302 then to, the voltage signal to be measured of 302 pairs of simulations of A/D change-over circuit disperses, quantizes, and converts digital voltage signal to be measured to; Export digital signal processing unit 303 to; The digital signal of digital signal processing unit in 303 pairs two adjacent time delay subtracted each other and carried out demodulation, and adding up demodulation result is thought of as staircase waveform, simultaneously; Square-wave signal superposes on staircase waveform; Obtain superposed signal, superposed signal is imported the superposed signal that a D/A change-over circuit 304, the one D/A change-over circuits 304 convert the superposed signal of numeral into simulation; Export Y waveguide phase-modulator 204 to; Realize close-loop feedback modulation with
, simultaneously, digital signal processing unit 303 also exports demodulation result to the 2nd D/A change-over circuit 305; The 2nd D/A change-over circuit 305 converts the digital demodulation result into the analog demodulator result; The signalling channel port that exports lock-in amplifier 306 to is measured, and lock-in amplifier 306 is measured amplitude and phase differential size, and then has realized the frequency characteristic assessment.
Being connected between excitation current source 1 and the responsive light path 2 is to realize through being wrapped in coil on the sensor fibre 208, being connected through photodetector 210 realizations of the testing circuit of handling at responsive light path 2 and analog optical fiber gyro signal 3.
The present invention is that the alternating current excitation magnetosensitive sensitization road of the frequency adjustable of employing produces the Faraday effect; The phase differential that the Faraday effect produces substitutes the phase differential of Sagnac effect; Because the sinusoidal current that exchanges can be realized high frequency output; Just can realize the frequency characteristic assessment test in low frequency and the high band through the phase differential that detects the Faraday effect; Especially realize the assessment of high band, promptly solved classic method and assessed the limited shortcoming of frequency and the unconspicuous defective of the reaction in low-frequency range of HWIL simulation scheme.
The present invention can the measuring optical fiber gyro frequency characteristic, also just can measure the bandwidth of gyro.Its meaning: one,, the checking means can be provided for the research of optical fibre gyro closed loop control algorithm through important function for of research.Two, through to the assessment of algorithm test, can draw the closed-loop bandwidth of the optical fibre gyro of approved product, for the scope of application of optical fibre gyro environmental suitability provides foundation.
The present invention is a kind of optical fibre gyro frequency characteristic appraisal procedure based on the Faraday effect, comprises following step:
Step 1: the light that is sent by SLD light source 1 is become linearly polarized light and gets into Y waveguide phase-modulator 204 partially by 203 of the optical fiber polarizers through a single mode circulator 202 back, and 204 places receive phase modulation (PM) at the Y waveguide phase-modulator.Polarized light injects polarization-maintaining fiber coils 206 by two tail optical fibers coupling back of polarization beam apparatus 205, respectively along the X axle and the transmission of Y axle of polarization maintaining optical fibre, through behind λ/4 wave plates 207, becomes left-handed and circularly polarized light dextrorotation and entering sensor fibre 208 respectively.Because the excitation exchange current produces magnetic field, in sensor fibre 208, produce the Faraday magneto-optic effect, the phase place of this two bundles circularly polarized light is changed (F=2VNI, wherein; F is a Faraday effect phase differential, and V is the Verdet constant, and N is for twining the number of turn of lead, and I is a size of current) and transmit with different speed; After the reflection of catoptron 209 places, the polarization mode of two bundle circularly polarized lights exchanges, and passes sensor fibre 208 once more; And the phase place that experience Faraday effect produces two-beam double (2F=4VNI, wherein, F is a Faraday effect phase differential; V is the Verdet constant, and N is for twining the number of turn of lead, and I is a size of current).This two-beam through behind λ/4 wave plates 207, reverts to linearly polarized light once more, and two bunch polarized lights interfere then.At last, the light that carries phase information is by single mode circulator 202 entering detectors 210.Because the two-beam that interferes; In the optic path process; All passed through the left-handed and dextrorotation pattern of X axle and the Y axle and the sensor fibre of polarization maintaining optical fibre respectively, difference slightly in time only, so the light of return detector 210 has only carried because the non-reciprocal phase that the Faraday effect produces is poor.
Step 2: the simulating signal entering A/D change-over circuit 302 that the voltage signal to be measured of 301 pairs of photodetectors of pre-amplification circuit, 210 outputs carries out after the amplification filtering disperses, quantizes; Convert digital signal to; Carry out the demodulation computing with supplied with digital signal processing unit 303; When signal processing unit 303 adds up the formation staircase waveform to demodulation result; Export a square-wave signal and be superimposed upon on the digital staircase waveform, superposed signal realizes close-loop feedback and ± pi/2 modulation through a D/A change-over circuit 304 conversion is after-applied on Y waveguide phase-modulator 204.Simultaneously, through the 305 conversion back outputs of the 2nd D/A change-over circuit, measure by the test port that gets into lock-in amplifier 306 demodulation result output for signal processing unit 303.Utilize lock-in amplifier 305 measuring-signal amplitudes and phase place extent, change the exciting current signal and then realized the frequency characteristic assessment.
Claims (5)
1. the optical fibre gyro frequency characteristic apparatus for evaluating based on the Faraday effect is characterized in that, comprises excitation current source, responsive light path and analog optical fiber gyro signal processing and detecting circuit;
Excitation current source comprises signal generator, converter amplifier circuit and current coil; Signal generator generates AC signal; AC signal exports converter amplifier circuit to, and converter amplifier circuit exchanges amplification to AC signal, exports exchange current to current coil then; Current coil is wrapped on the sensor fibre of responsive light path; Feed exchange current in the current coil, the magnetic field of generation makes the sensor fibre induction Faraday effect in the responsive light path, has realized that signal is delivered in the responsive light path by excitation current source; The exchange current of converter amplifier circuit output through a sampling resistor after, obtain sampled voltage, sampled voltage is exported to the reference port of lock-in amplifier;
Responsive light path comprises light source, circulator, Y waveguide phase-modulator, polarization beam apparatus, polarization-maintaining fiber coil, λ/4 wave plates, sensor fibre, catoptron and detector; Light source sends light, and light gets into the Y waveguide phase-modulator through behind the circulator, after Y waveguide phase-modulator place rises partially for linearly polarized light, receives phase modulation (PM); Polarized light after the modulation exports polarization beam apparatus to, after two tail optical fiber couplings of polarized light by polarization beam apparatus, injects polarization-maintaining fiber coil, and polarized light transmits along the X axle and the Y axle of polarization-maintaining fiber coil respectively; After getting into λ/4 wave plates, in λ/4 wave plates, polarized light becomes left-handed respectively and circularly polarized light dextrorotation, and gets into sensor fibre; The phase place of two bundle circularly polarized lights changes, F=2VNI, and wherein, F is a Faraday effect phase differential; V is the Verdet constant, and N is for twining the number of turn of lead, and I is a size of current; Two bundle circularly polarized lights transmit with different speed, export catoptron to, after the reflection of the minute surface place of catoptron; The polarization mode of two bundle circularly polarized lights exchanges, and passes sensor fibre once more, and the phase place that two bundle circularly polarized lights are produced doubles 2F=4VNI; Two bundle circularly polarized lights revert to linearly polarized light once more through behind λ/4 wave plates, and two bunch polarized lights interfere then; The light that carries phase information gets into detector by circulator, and detector realizes that converting voltage signal into by light signal exports pre-amplification circuit to;
Analog optical fiber gyro signal processing and detecting circuit comprises pre-amplification circuit, A/D change-over circuit, digital signal processing unit, a D/A change-over circuit, the 2nd D/A change-over circuit and lock-in amplifier; Pre-amplification circuit carries out amplification filtering to the voltage signal to be measured of detector output, exports the A/D change-over circuit then to, and the A/D change-over circuit disperses, quantizes the voltage signal to be measured of simulation; Convert digital voltage signal to be measured to, export digital signal processing unit to, digital signal processing unit subtracts each other the digital signal in two adjacent time delay and carries out demodulation; Add up demodulation result and be thought of as staircase waveform; Simultaneously, the square-wave signal that on staircase waveform, superposes obtains superposed signal; Superposed signal is imported a D/A change-over circuit; The one D/A change-over circuit converts the superposed signal of numeral the superposed signal of simulation into, exports the Y waveguide phase-modulator to, realizes close-loop feedback modulation with
; Simultaneously; Digital signal processing unit also exports demodulation result to the 2nd D/A change-over circuit, and the 2nd D/A change-over circuit converts the digital demodulation result into the analog demodulator result, and the signalling channel port that exports lock-in amplifier to is measured; Lock-in amplifier is measured amplitude and phase differential size, has realized the frequency characteristic assessment.
2. a kind of optical fibre gyro frequency characteristic apparatus for evaluating based on the Faraday effect according to claim 1 is characterized in that, regulates the frequency of AC signal through signal generator.
3. a kind of optical fibre gyro frequency characteristic apparatus for evaluating based on the Faraday effect according to claim 1 is characterized in that described light source is the SLD light source.
4. a kind of optical fibre gyro frequency characteristic apparatus for evaluating according to claim 1 based on the Faraday effect; It is characterized in that; Be provided with the fiber optic loop of 4 different lengths in the described polarization-maintaining fiber coil, be respectively 570m, 350m, 100m and 200m, when needs use the light ring of one of them length; The light ring of choosing is connected with polarization beam apparatus, λ/4 wave plates respectively through wire jumper, forms polarization-maintaining fiber coil.
5. optical fibre gyro frequency characteristic appraisal procedure based on the Faraday effect comprises following step:
Step 1: the light that is sent by light source gets into the Y waveguide phase-modulator after through a circulator, is modulated to linearly polarized light at Y waveguide phase-modulator place and receives phase modulation (PM); Polarized light injects polarization-maintaining fiber coils by two tail optical fibers coupling back of polarization beam apparatus, respectively along the X axle and the transmission of Y axle of polarization maintaining optical fibre, through behind λ/4 wave plates, becomes left-handed and circularly polarized light dextrorotation and entering sensor fibre respectively; Because the excitation exchange current produces magnetic field, in sensor fibre, produce the Faraday magneto-optic effect, make the phase place of this two bundles circularly polarized light change F=2VNI; Wherein, F is a Faraday effect phase differential, and V is the Verdet constant, and N is for twining the number of turn of lead; I is a size of current, and with the different speed transmission, after the reflection of catoptron place, the polarization mode of two bundle circularly polarized lights exchanges; Pass sensor fibre once more, and the phase place that experience Faraday effect produces two-beam doubles 2F=4VNI; Two-beam through behind λ/4 wave plates, reverts to linearly polarized light once more, and two bunch polarized lights interfere then; At last, the light that carries phase information gets into detector by circulator, and the light of return detector has only carried because the non-reciprocal phase that the Faraday effect produces is poor;
Step 2: the simulating signal entering A/D change-over circuit that the voltage signal to be measured that pre-amplification circuit is exported photodetector carries out after the amplification filtering disperses, quantizes; Convert digital signal to; Carry out the demodulation computing with the supplied with digital signal processing unit; When signal processing unit adds up the formation staircase waveform to demodulation result; Export a square-wave signal and be superimposed upon on the digital staircase waveform, superposed signal realizes close-loop feedback and ± pi/2 modulation through D/A change-over circuit conversion is after-applied on the Y waveguide phase-modulator; Simultaneously, through the 2nd D/A change-over circuit conversion back output, measure by the test port that gets into lock-in amplifier demodulation result output for signal processing unit; Utilize lock-in amplifier measuring-signal amplitude and phase place extent, change the exciting current signal and then realized the frequency characteristic assessment.
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