CN102322964B - Optical phase lock tracking method based on four-channel laser frequency demodulation phase demodulation technology and apparatus realizing method - Google Patents
Optical phase lock tracking method based on four-channel laser frequency demodulation phase demodulation technology and apparatus realizing method Download PDFInfo
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Abstract
The invention provides an optical phase lock tracking method based on four-channel laser frequency demodulation phase demodulation technology and an apparatus realizing the method, belonging to the optical field. The invention is aimed at solving a problem that in present optical phase lock tracking technology a capture zone is small and carrying out pre-frequency-lock is in need. According to the invention, four-channel detection technology is utilized to track incident laser, the incident laser and emitting laser emitted by a laser module are directly subjected to optical frequency mixing to form a first route of beat frequency signal, simultaneously the incident laser is subjected to 90 degrees of phase delay to form a second route of beat frequency signal. A phase relationship of the two routes of beat frequency signals is subjected to ahead and delay determination by utilizing four subdivision sensing technology, a frequency size relation of the incident laser and the emitting laser is obtained, and combined with frequency measurement and arc tangent phase measurement on the two beat frequency signals, accurate measurement of frequency difference and phase difference between the incident laser and the emitting laser are realized. A frequency value and a phase value obtained by measurement are taken as control quantities of a control laser module, so emitting light can lock frequency and phase of incident light.
Description
Technical field
The present invention relates to a kind of based on four-way laser frequency discrimination phase demodulation technology optics phase locked track method and realize the device of this method, belong to optical field.
Background technology
In the precision optics field of measurement, need coherent laser to realize high-precision interferometry usually.Along with system under test (SUT) is complicated day by day to measuring the continuous increase of number of channels demand, only provide the multichannel coherent laser can't satisfy the needs of measuring system through beam split to light intensity by single laser instrument.In addition, in the overlength distance laser interferometry, the interferometry laser that is provided by the transmitting terminal laser instrument can constantly be dispersed and decays along with the growth of measuring light path, this to a great extent limit the raising of overlength distance laser interferometry precision.Optics phase locked track technology provides a kind of feasible technical scheme for solving above-mentioned technical barrier, its from last century the mid-80 just receive and pay close attention to and obtained development fast widely.
The optics phaselocked loop can be realized frequency and the Phase Tracking of target laser to reference laser; The composition structural similarity of the phaselocked loop in itself and the electricity field; But local oscillator is replaced by local laser instrument, and phase detector needs to realize high-precision laser interference phase demodulation simultaneously.The optics phase locked loop type of development in recent years mainly contains balance phaselocked loop, costas phase lock loop, decision drive phaselocked loop and synchronization bit phaselocked loop etc.
Counter lock phase eye is proposed in nineteen eighty-three by people such as the G.L.Abbas of masschusetts, u.s.a Polytechnics and V.W.S.Chan earlier.As the most basic optics phaselocked loop, it obtains people's understanding at first.The balance phaselocked loop uses the directional coupler of a 3dB that local laser and reference laser are carried out optical frequency mixing, is differed two beat frequency light signals of 180 ° again by the same model photodiode receiving phase of two series connection.This scheme has made full use of the light signal of two output terminals of coupling mechanism, and the DC current of two photodiode generations can be cancelled out each other under the phase locking state, and this can have been avoided laser power fluctuation to lock phase Effect on Performance to a certain extent.The beat frequency electric signal that the photodiode monitoring obtains is handled the local laser instrument of back FEEDBACK CONTROL through loop filter, finally realizes the phase locked track of local laser to reference laser.But, be the zero situation that can't judge the phase control direction for fear of average phase, the balance phaselocked loop need transmit residual carrier, and the local oscillator light signal just can be realized phase locking perpendicular to residual carrier.
Nineteen eighty-three, the people such as H.K.Philipp and A.L.Scholtz of Technical University of Vienna proposed section's Stas optics phaselocked loop; This phaselocked loop uses 90 ° of phase shifted light bridges that local laser and reference laser are carried out optical frequency mixing, and it has homophase passage and two signal output channels of quadrature phase passage.Wherein, the mixed frequency signal of homophase passage output is directly superposeed by two laser signals and forms, the mixed frequency signal of orthogonal channel output by phase delay 90 ° reference laser and local laser superpose and form.The output beat frequency light of these two mixing passages at first converts two path signal into by photodetector; Then two path signal is multiplied each other and calculate the phase differential of two signals; And the fm control signal of process low-pass loop filter generation local oscillator laser instrument, finally realize phase locking.The characteristics of this phaselocked loop are the lock phase current to be multiply by marking current obtain phase signal; Because photocurrent has been passed through this Nonlinear Processing in the lock phase front; Therefore the mean value of modulation back lock phase current can not be zero; Also just no longer need transmit residual carrier, this has alleviated the burden of signal Processing link to a great extent.
The L.G.Kazovsky at the Navesing of bell communication research company research engineering center in 1985 has proposed decision drive optics phaselocked loop; This phaselocked loop is same to use 90 ° of phase shifted light bridges to produce the mutually orthogonal beat signal of two-way; But different is; The output of homophase passage is after decision circuitry is handled, and multiplying each other with the quadrature phase passage obtains phase signal again.Temporal synchronously for realizing two channel signals, in the quadrature phase passage, be provided with chronotron usually.The characteristics of this phaselocked loop are that the output current that the lock phase current multiply by decision circuitry is obtained phase signal, and it has carried out Nonlinear Processing to photocurrent equally, therefore need not transmit residual carrier.Comparatively speaking, the decision drive phase-locked loop performance is superior to balance phaselocked loop and costas phase lock loop, and the variance yields of its phase error is littler than costas phase lock loop, but the requirement of laser linewidth is higher than costas phase lock loop.
The synchronization bit phaselocked loop is developed by costas phase lock loop; It utilizes the homophase passage of costas phase lock loop and the characteristics that the quadrature phase passage is not worked simultaneously; In feedback control loop, be provided with a switch, the closure through switch realizes homophase passage and quadrature phase passage at times.Like this, just only need a cover balance detection device and an AC coupling front end circuit, not only structure is simplified greatly, and the detection circuit of homophase passage and quadrature phase passage is identical, has reduced owing to the different lock phase errors that cause of device.Most of the time feedback control loop switch breaks off, and accomplishes the in-phase branch of costas phase lock loop.To realize loop feedback, accomplish quadrature phase branch in the gap switch closure of every Bit data.The synchronization bit phase-locked loop structures is simple, but bandwidth and signal to noise ratio (S/N ratio) are relatively poor.In addition, the synchronization bit phaselocked loop needs extra data pre-service and aftertreatment, can only transmission of digital signals, and the requirement of laser linewidth also is higher than costas phase lock loop.
But all there is a common defective in above-mentioned phaselocked loop: its phase detector that only constitutes by phase shifted light bridge and balance power detector to a great extent limit the pull-in range of phaselocked loop, the pull-in range maximum that above-mentioned phaselocked loop can be realized is merely the MHz magnitude.But for frequency up to 10
14The free laser of two bundles of magnitude, its difference on the frequency is seldom in MHz, even the frequency stability of single beam laser all is difficult to reach the MHz magnitude.Therefore, realize above-mentioned optics phaselocked loop, need carry out preparatory frequency locking and realize the high accuracy frequency stabilization local laser instrument based on reference laser usually that this has improved the realization difficulty of system undoubtedly.
Summary of the invention
The present invention seeks in order to solve the problem that existing optics phase locked track technology capture zone is less, need carry out preparatory frequency locking, provide a kind of based on four-way laser frequency discrimination phase demodulation technology optics phase locked track method and realize the device of this method.
A kind of optics phase locked track method according to the invention based on four-way laser frequency discrimination phase demodulation technology, this method may further comprise the steps:
Step 1, the outside incident laser as frequency and phase reference that provides of reception are designated as L with this incident laser
1, open laser module simultaneously, get into steady-working state through this laser module behind the warm, the shoot laser of laser module is designated as L
2
Step 2, utilize 1/2nd wave plates and polarization splitting prism adjustment incident laser L
1With laser module shoot laser L
2Polarization state, will adjust the mutually perpendicular two bundle laser of rear polarizer direction and close light and form and to close the light light beam, utilize the adjustment of 1/2nd wave plates to close incident laser L in the light light beam again
1With shoot laser L
2The polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;
Step 3, utilize the depolarization Amici prism will close the light light beam to be divided into reflection and to close the light light beam and light light beam two parts are closed in transmission; The light light beam forms 180 ° of two-way phase phasic differences through polarization splitting prism beat frequency light signal is closed in reflection; Converted into the beat frequency electric signal and sent into the signal condition module by two high-speed photodetectors respectively, the light light beam is closed in transmission at first will close incident laser L in the light light beam through optical phase delay device
190 ° of phase delays, form the beat frequency light signal of 180 ° of two-way phase phasic differences then through polarization splitting prism, convert the beat frequency electric signal into and send into the signal condition module by two other high-speed photodetector respectively;
Step 4, with incident laser L
1With shoot laser L
2Frequency be designated as v respectively
1And v
2, the incident laser L in the light light beam is closed in reflection
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in reflection
2The phase place that arrives photodetector is designated as
The signal condition module is closed the corresponding two-way beat frequency electric signal of light light beam with reflection and is subtracted each other and obtain closing light reflection beat signal,
Then work as v
1=v
2The time, close light reflection beat signal and do
Work as v
1＞v
2The time, close light reflection beat signal and do
Work as v
1＜v
2The time, close light reflection beat signal and do
Step 5, signal condition module are closed the corresponding two-way beat frequency electric signal of light light beam with transmission and are subtracted each other and obtain closing the transmittance beat signal, because the effect of optical phase delay device, the incident laser L in the light light beam is closed in transmission
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in transmission
2The phase place that arrives photodetector is designated as
Then work as v
1=v
2The time, close the transmittance beat signal and do
Work as v
1＞v
2The time, close the transmittance beat signal and do
Work as v
1＜v
2The time, close the transmittance beat signal and do
v
meas＝|v
1-v
2|，
When closing light reflection beat signal phase place when closing 90 ° of transmittance beat signals in advance, show v
1＞v
2, frequency measurement this moment result does
v
meas＝v
1-v
2，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝v
meas，
When closing 90 ° of transmittance beat signals, light reflection beat signal phase lag shows v when closing
1＜v
2, frequency measurement this moment result does
v
meas＝v
2-v
1，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝-v
meas；
Step 8, laser module finish the back in its optical frequency control procedure and get into lock and controls the stage mutually, at first get to close light reflection beat signal and close the transmittance beat signal and carry out the arc tangent phase measurement, obtain incident laser L
1With shoot laser L
2Identified result do
With the phase value that measures
As phase-locked closed-loop control signal input digit controller, through the PZT drive control module cavity length is carried out meticulous quick adjustment, the output light phase of FEEDBACK CONTROL laser module
Make
Be tending towards 0, when
The time, the lock phase control procedure of laser module is accomplished, its shoot laser L
2Phase locking be incident laser L
1Phase place, promptly
Step 9, when optics phase locked track system losing lock, repeating step six to eight, the shoot laser L of laser module
2Can be to incident laser L
1Carry out phase locked track again.
Realize above-mentioned a kind of device based on the technological optics phase locked track method of four-way laser frequency discrimination phase demodulation; It comprises the 1/1st wave plate; First polarization splitting prism; The 1/2nd wave plate; The depolarization Amici prism; Second polarization splitting prism; First high-speed photodetector; Second high-speed photodetector; Optical phase delay device; The 3rd polarization splitting prism; The 3rd high-speed photodetector; The 4th high-speed photodetector; The signal condition module; The frequency measurement module; Quadrature phase demodulation module; Digitial controller; Temperature control modules; The PZT drive control module; Laser module; The 1/3rd wave plate and the 4th polarization splitting prism
Incident laser is transmitted through first polarization splitting prism through the 1/1st wave plate,
The shoot laser that laser module sends is transmitted through the 4th polarization splitting prism through the 1/3rd wave plate; The folded light beam of the 4th polarization splitting prism be transmitted to first polarization splitting prism incident laser form close the light light beam; The said light light beam that closes is transmitted through the depolarization Amici prism through the 1/2nd wave plate
The reflection of depolarization Amici prism is closed the light light beam and is incident to second polarization splitting prism, and the folded light beam of second polarization splitting prism is incident to first high-speed photodetector, and the transmitted light beam of second polarization splitting prism is incident to second high-speed photodetector,
The transmission of depolarization Amici prism is closed the light light beam and is incident to optical phase delay device; Optical phase delay device postpones light beam and is incident to the 3rd polarization splitting prism; The folded light beam of the 3rd polarization splitting prism is incident to the 3rd high-speed photodetector; The transmitted light beam of the 3rd polarization splitting prism is incident to the 4th high-speed photodetector
The electric signal of the collection of first high-speed photodetector, second high-speed photodetector, the 3rd high-speed photodetector and the 4th high-speed photodetector is exported to four signal input parts of signal condition module respectively; The folded light beam difference signal output terminal of signal condition module links to each other with the input end of frequency measurement module and the input end of quadrature phase demodulation module simultaneously; The transmitted light beam difference signal output terminal of signal condition module links to each other with the input end of frequency measurement module and the input end of quadrature phase demodulation module simultaneously; The output terminal of frequency measurement module links to each other with the first input end of digitial controller; The output terminal of quadrature phase demodulation module links to each other with second input end of digitial controller; The control temperature signal output terminal of digitial controller links to each other with the input end of temperature control modules; The output terminal of temperature control modules links to each other with first control end of laser module; The PZT drive signal output terminal of digitial controller links to each other with the input end of PZT drive control module, and the output terminal of PZT drive control module links to each other with the PZT drive signal control end of laser module.
Advantage of the present invention:
(1) compare with existing optics phase-lock technique, the optics phase locked track method that the present invention designed had increased optical frequency locking control procedure before advancing horizontal lock.This makes when local laser and incident laser frequency differ big; Can at first make local Laser Tracking incident laser frequency; Thereby expanded the acquisition bandwidth of phase locked track greatly, the anti-interference of system has also obtained significantly promoting, and this is one of innovative point that is different from prior art.
(2) used high-precision integrated laser phase frequency detector in the optics phase locked track device that the present invention designed; Laser frequency discrimination link wherein is when recording two bundle laser frequency difference absolute values; Also according to two-way close photo-beat frequently the lead lag relationship of signal confirmed the frequency magnitude relationship of two bundle incident lasers really to have realized accurate measurement to two bundle incident laser difference on the frequencies; Laser phase demodulation link then through the arc tangent phase measurement and the signal sensing of the two-way quadrature beat signal that detection channels generated to four, has realized high-precision phase measurement.The balance detection of its four passages makes laser power fluctuation obtain good restraining to the influence of measurement result, this be different from prior art innovative point two.
Description of drawings
Fig. 1 is the structural representation of apparatus of the present invention;
Fig. 2 is incident laser L
1Frequency v
1Greater than shoot laser L
2Frequency v
2The time, close light reflection beat signal S
1With transmission beat signal S
2The phase relation synoptic diagram;
Fig. 3 is incident laser L
1Frequency v
1Less than shoot laser L
2Frequency v
2The time, close light reflection beat signal S
1With transmission beat signal S
2The phase relation synoptic diagram.
Embodiment
Embodiment one: below in conjunction with Fig. 1 to Fig. 3 this embodiment is described, the said a kind of optics phase locked track method of this embodiment based on four-way laser frequency discrimination phase demodulation technology, this method may further comprise the steps:
Step 1, the outside incident laser as frequency and phase reference that provides of reception are designated as L with this incident laser
1, open laser module simultaneously, get into steady-working state through this laser module behind the warm, the shoot laser of laser module is designated as L
2
Step 2, utilize 1/2nd wave plates and polarization splitting prism adjustment incident laser L
1With laser module shoot laser L
2Polarization state, will adjust the mutually perpendicular two bundle laser of rear polarizer direction and close light and form and to close the light light beam, utilize the adjustment of 1/2nd wave plates to close incident laser L in the light light beam again
1With shoot laser L
2The polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;
Step 3, utilize the depolarization Amici prism will close the light light beam to be divided into reflection and to close the light light beam and light light beam two parts are closed in transmission; The light light beam forms 180 ° of two-way phase phasic differences through polarization splitting prism beat frequency light signal is closed in reflection; Converted into the beat frequency electric signal and sent into the signal condition module by two high-speed photodetectors respectively, the light light beam is closed in transmission at first will close incident laser L in the light light beam through optical phase delay device
190 ° of phase delays, form the beat frequency light signal of 180 ° of two-way phase phasic differences then through polarization splitting prism, convert the beat frequency electric signal into and send into the signal condition module by two other high-speed photodetector respectively;
Step 4, with incident laser L
1With shoot laser L
2Frequency be designated as v respectively
1And v
2, the incident laser L in the light light beam is closed in reflection
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in reflection
2The phase place that arrives photodetector is designated as
The signal condition module is closed the corresponding two-way beat frequency electric signal of light light beam with reflection and is subtracted each other and obtain closing light reflection beat signal,
Then work as v
1=v
2The time, close light reflection beat signal and do
Work as v
1＞v
2The time, close light reflection beat signal and do
Work as v
1＜v
2The time, close light reflection beat signal and do
Step 5, signal condition module are closed the corresponding two-way beat frequency electric signal of light light beam with transmission and are subtracted each other and obtain closing the transmittance beat signal, because the effect of optical phase delay device, the incident laser L in the light light beam is closed in transmission
190 ° of the phase delays of arrival photodetector, incident laser L
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in transmission
2The phase place that arrives photodetector is designated as
Then work as v
1=v
2The time, close the transmittance beat signal and do
Work as v
1＞v
2The time, close the transmittance beat signal and do
Work as v
1＜v
2The time, close the transmittance beat signal and do
v
meas＝|v
1-v
2|，
When closing light reflection beat signal phase place when closing 90 ° of transmittance beat signals in advance, show v
1＞v
2, frequency measurement this moment result does
v
meas＝v
1-v
2，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝v
meas，
When closing 90 ° of transmittance beat signals, light reflection beat signal phase lag shows v when closing
1＜v
2, frequency measurement this moment result does
v
meas＝v
2-v
1，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝-v
meas；
Step 8, laser module finish the back in its optical frequency control procedure and get into lock and controls the stage mutually, at first get to close light reflection beat signal and close the transmittance beat signal and carry out the arc tangent phase measurement, obtain incident laser L
1With shoot laser L
2Identified result do
With the phase value that measures
As phase-locked closed-loop control signal input digit controller, through the PZT drive control module cavity length is carried out meticulous quick adjustment, the output light phase of FEEDBACK CONTROL laser module
Make
Be tending towards 0, when
The time, the lock phase control procedure of laser module is accomplished, its shoot laser L
2Phase locking be incident laser L
1Phase place, promptly
Step 9, when optics phase locked track system losing lock, repeating step six to eight, the shoot laser L of laser module
2Can be to incident laser L
1Carry out phase locked track again.
When starting working, receive the outside incident laser as frequency and phase reference is provided, open laser module 18 simultaneously and make it get into warm, final laser module 18 gets into steady-working states and also exports shoot laser.
Utilize the polarization direction of the 1/1st wave plate 1 adjustment incident laser, make its horizontal polarization component light intensity maximum, by the horizontal polarization component of first polarization splitting prism, 2 transmission incident lasers.Shoot laser utilizes the 4th polarization splitting prism 20 that the vertical polarized component reflection of shoot laser is got into first polarization splitting prism 2 at first through the 1/3rd wave plate 19 adjustment polarization directions again, realizes the light that closes of incident laser and shoot laser.This closes incident laser horizontal polarization component and the vertical polarized component of shoot laser in the light, and its vibration equation can be expressed as respectively:
Closing the incident laser horizontal polarization component that comprises in the light and the vertical polarized component of shoot laser rotates to respectively after through the 1/2nd wave plate 3 and becomes 45 ° direction with level.Depolarization Amici prism 4 is divided into two parts that light intensity equates with the postrotational light light beam that closes of polarization state, and its reflection and transmissive part are designated as L respectively
rAnd L
t, it is each other vertical and become the incident laser and the shoot laser of 45 ° of angles with level all to comprise the polarization direction in every part.
Close photo-emission part and divide L
rBeat frequency light signal through 180 ° of second polarization splitting prism, 5 formation two-way phase phasic differences is converted into the beat frequency electric signal by first high-speed photodetector 6 and second high-speed photodetector 7 respectively.
For eliminating the direct current biasing of introducing with laser power fluctuation in the beat signal, signal condition module 12 is subtracted each other this two-way beat frequency electric signal, and the light reflection beat signal that closes that obtains is designated as S
1, its frequency magnitude relationship according to two incident lasers is represented as follows:
Work as v
1＞v
2The time,
Work as v
1＜v
2The time,
Work as v
1=v
2The time,
Close transmittance part L
tAt first pass through optical phase delay device 8 with 90 ° of incident laser phase delays, close transmittance part L this moment
tThe vibration equation of middle incident laser becomes:
Close transmittance part L
tGet into the beat frequency light signal that the 3rd polarization splitting prism 9 forms 180 ° of two-way phase phasic differences, it is converted into the beat frequency electric signal through the 3rd high-speed photodetector 10 and the 4th high-speed photodetector 11 respectively.Two-way beat frequency electric signal is transferred to signal condition module 12 equally and obtains closing the transmittance beat signal, is designated as S
2, its frequency magnitude relationship according to two incident lasers is represented as follows:
Work as v
1＞v
2The time,
Work as v
1＜v
2The time,
Work as v
1=v
2The time,
After this get into optical frequency locking control procedure, close light reflection beat signal S
1With close transmittance beat signal S
2Be transferred to frequency measurement module 13, the difference on the frequency that utilizes synchronous frequency measuring method of multicycle to measure two bundle laser is v
MeasAt this moment, the just incident laser that measures and the absolute value of shoot laser difference on the frequency can not confirm that two restraint the frequency magnitude relationship of laser, i.e. v
Meas=| v
1-v
2|.
By above-mentioned formula, corresponding incident and shoot laser frequency v
1With v
2Different magnitude relationship, close light reflection beat signal S
1With close transmittance beat signal S
2Phase place lead-lag state also different thereupon.Therefore, utilize four segmentation sensing technology to judge and close light reflection beat signal S
1With close transmittance beat signal S
2The phase place lead lag relationship just can confirm first and second incident laser frequency v
1With v
2Magnitude relationship.
As shown in Figure 2, if close light reflection beat signal S
1Phase place close transmittance beat signal S in advance
290 °, according to S
1With S
2Expression formula can judge v
1＞v
2, this moment v
Meas=v
1-v
2, then finally calculate the accurate difference on the frequency Δ v of incident laser and shoot laser
1-2=v
1-v
2=v
MeasAs shown in Figure 3, if close light reflection beat signal S
1Phase lag transmission beat signal S
290 °, according to S
1With S
2Expression formula can judge v
1＜v
2, this moment v
Meas=v
2-v
1, then finally calculate the accurate difference on the frequency Δ v of incident laser and shoot laser
1-2=v
1-v
2=-v
Meas
With incident and shoot laser frequency-splitting Δ v
1-2 Input digit controller 15, it is calculated controlled quentity controlled variable and is transferred to temperature control modules 16 and PZT drive control module 17 respectively by control algolithm.The both realizes the control to the shoot laser frequency through the cavity length of adjustment laser module 18, but concrete implementation is different.Temperature control modules 16 is according to the positive and negative of controlled quentity controlled variable and big or small laser module 18 is carried out in various degree heating or refrigeration, through changing its resonator cavity temperature cavity length is adjusted, though the slow range of adjustment of this mode response speed is big.17 of PZT drive control modules directly use piezoelectric ceramics (PZT) that the cavity length of laser module 18 is adjusted, this mode response speed fast and regulate meticulous, but adjustable extent is very little.Through being used of temperature control modules 16 and PZT drive control module 17, after having realized the precise frequency locking of shoot laser to incident laser, optical frequency locking control procedure finishes, at this moment v
1=v
2
System gets into lock phase control procedure immediately, will close light reflection beat signal S
1With close transmittance beat signal S
2Be transferred to quadrature phase demodulation module 14.By v
1=v
2The transmission beat frequency AC signal S of state
2Divided by reflection beat frequency AC signal S
1:
By following formula;
carried out arctangent cp cp operation can record two the bundle laser phase difference value
with this phase difference value
input digit controller 15, it is calculated controlled quentity controlled variable and is transferred to PZT drive control module 17 by control algolithm.Directly the cavity length of laser module 18 is carried out meticulous adjusting fast by PZT drive control module 17; And accurately control with this phase place to shoot laser; Up to having realized shoot laser the phase locking of incident laser is followed the tracks of; The phase locking control procedure finishes,
at this moment
When optics phase locked track system losing lock, repeat optical frequency locking control stage and phase locked track control stage, can realize laser module shoot laser L
2To incident laser L
1Phase locked track again.
Embodiment two: this embodiment is described below in conjunction with Fig. 1; Realize the device of the described a kind of laser frequency discrimination phase detecting method based on the four-way Detection Techniques of embodiment one; It comprises the 1/1st wave plate 1; First polarization splitting prism 2; The 1/2nd wave plate 3; Depolarization Amici prism 4; Second polarization splitting prism 5; First high-speed photodetector 6; Second high-speed photodetector 7; Optical phase delay device 8; The 3rd polarization splitting prism 9; The 3rd high-speed photodetector 10; The 4th high-speed photodetector 11; Signal condition module 12; Frequency measurement module 13; Quadrature phase demodulation module 14; Digitial controller 15; Temperature control modules 16; PZT drive control module 17; Laser module 18; The 1/3rd wave plate 19 and the 4th polarization splitting prism 20
Incident laser is transmitted through first polarization splitting prism 2 through the 1/1st wave plate 1,
The shoot laser that laser module 18 sends is transmitted through the 4th polarization splitting prism 20 through the 1/3rd wave plate 19; The folded light beam of the 4th polarization splitting prism 20 be transmitted to first polarization splitting prism 2 incident laser form close the light light beam; The said light light beam that closes is transmitted through depolarization Amici prism 4 through the 1/2nd wave plate 3; The reflection of depolarization Amici prism 4 is closed the light light beam and is incident to second polarization splitting prism 5; The transmitted light beam that the folded light beam of second polarization splitting prism 5 is incident to first high-speed photodetector, 6, the second polarization splitting prisms 5 is incident to second high-speed photodetector 7
The transmission of depolarization Amici prism 4 is closed the light light beam and is incident to optical phase delay device 8; Optical phase delay device 8 postpones light beam and is incident to the 3rd polarization splitting prism 9; The folded light beam of the 3rd polarization splitting prism 9 is incident to the 3rd high-speed photodetector 10; The transmitted light beam of the 3rd polarization splitting prism 9 is incident to the 4th high-speed photodetector 11
The electric signal of the collection of first high-speed photodetector 6, second high-speed photodetector 7, the 3rd high-speed photodetector 10 and the 4th high-speed photodetector 11 is exported to four signal input parts of signal condition module 12 respectively; The folded light beam difference signal output terminal of signal condition module 12 links to each other with the input end of frequency measurement module 13 and the input end of quadrature phase demodulation module 14 simultaneously; The transmitted light beam difference signal output terminal of signal condition module 12 links to each other with the input end of frequency measurement module 13 and the input end of quadrature phase demodulation module 14 simultaneously; The output terminal of frequency measurement module 13 links to each other with the first input end of digitial controller 15; The output terminal of quadrature phase demodulation module 14 links to each other with second input end of digitial controller 15; The control temperature signal output terminal of digitial controller 15 links to each other with the input end of temperature control modules 16; The output terminal of temperature control modules 16 links to each other with first control end of laser module 18; The PZT drive signal output terminal of digitial controller 15 links to each other with the input end of PZT drive control module 17, and the output terminal of PZT drive control module 17 links to each other with the PZT drive signal control end of laser module 18.
Embodiment three: this embodiment is described further embodiment two, and optical phase delay device 8 is wave plate phase delay device, reflective phase delay mirror, liquid crystal phase delay device or electric light phase shifter.
Optical phase delay device 8 only carries out phase delay to incident laser.
More than combine the accompanying drawing specific embodiments of the invention to be illustrated; But according to law stipulates that these explanations can not limit rights protection scope of the present invention; Protection scope of the present invention is limited the claims of enclosing, and the change that any that on claim of the present invention basis, carry out, these those skilled in the art can make according to existing knowledge is all in protection scope of the present invention.
Claims (3)
1. optics phase locked track method based on four-way laser frequency discrimination phase demodulation technology is characterized in that this method may further comprise the steps:
Step 1, the outside incident laser as frequency and phase reference that provides of reception are designated as L with this incident laser
1, open laser module simultaneously, get into steady-working state through this laser module behind the warm, the shoot laser of laser module is designated as L
2
Step 2, utilize 1/2nd wave plates and polarization splitting prism adjustment incident laser L
1With laser module shoot laser L
2Polarization state, will adjust the mutually perpendicular two bundle laser of rear polarizer direction and close light and form and to close the light light beam, utilize the adjustment of 1/2nd wave plates to close incident laser L in the light light beam again
1With shoot laser L
2The polarization direction, make two the bundle laser the polarization direction all from the horizontal by 45 ° of angles;
Step 3, utilize the depolarization Amici prism will close the light light beam to be divided into reflection and to close the light light beam and light light beam two parts are closed in transmission; The light light beam forms 180 ° of two-way phase phasic differences through polarization splitting prism beat frequency light signal is closed in reflection; Converted into the beat frequency electric signal and sent into the signal condition module by two high-speed photodetectors respectively, transmission is closed the light light beam and at first transmission is closed incident laser L in the light light beam through optical phase delay device
190 ° of phase delays, form the beat frequency light signal of 180 ° of two-way phase phasic differences then through polarization splitting prism, convert the beat frequency electric signal into and send into the signal condition module by two other high-speed photodetector respectively;
Step 4, with incident laser L
1With shoot laser L
2Frequency be designated as v respectively
1And v
2, the incident laser L in the light light beam is closed in reflection
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in reflection
2The phase place that arrives photodetector is designated as
The signal condition module is closed the corresponding two-way beat frequency electric signal of light light beam with reflection and is subtracted each other and obtain closing light reflection beat signal,
Then work as v
1=v
2The time, close light reflection beat signal and do
Work as v
1＞v
2The time, close light reflection beat signal and do
Work as v
1＜v
2The time, close light reflection beat signal and do
Step 5, signal condition module are closed the corresponding two-way beat frequency electric signal of light light beam with transmission and are subtracted each other and obtain closing the transmittance beat signal, because the effect of optical phase delay device, the incident laser L in the light light beam is closed in transmission
1The phase place that arrives photodetector is designated as
The shoot laser L in the light light beam is closed in transmission
2The phase place that arrives photodetector is designated as
Then work as v
1=v
2The time, close the transmittance beat signal and do
Work as v
1＞v
2The time, close the transmittance beat signal and do
Work as v
1＜v
2The time, close the transmittance beat signal and do
Step 6, laser module get into the optical frequency locking control stage, at first get to close light reflection beat signal and close the transmittance beat signal and carry out frequency measurement, and the frequency measurement result is designated as v
Meas,
v
meas＝|v
1-v
2|，
When closing light reflection beat signal phase place when closing 90 ° of transmittance beat signals in advance, show v
1＞v
2, frequency measurement this moment result does
v
mead＝v
1-v
2，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝v
meas，
When closing 90 ° of transmittance beat signals, light reflection beat signal phase lag shows v when closing
1＜v
2, frequency measurement this moment result does
v
meas＝v
2-v
1，
The frequency discrimination result who obtains first incident laser and second incident laser does
Δv
1-2＝v
1-v
2＝-v
meas；
Step 7, with the frequency values Δ v that measures
1-2As optical frequency locking signal input digit controller; Corresponding relation according to local laser frequency and laser module cavity length; Adjust laser module resonator cavity temperature to realize adjusting on a large scale through temperature control modules to cavity length; Through the PZT drive control module cavity length is directly regulated fast the output light frequency v of FEEDBACK CONTROL laser module simultaneously
2Make Δ v
1-2Be tending towards 0, as Δ v
1-2=0 o'clock, the optical frequency locked stage of laser module finished, its output laser L
2Frequency lock be incident laser L
1Frequency, i.e. v
2=v
1
Step 8, laser module finish the back in its optical frequency control procedure and get into lock and controls the stage mutually, at first get to close light reflection beat signal and close the transmittance beat signal and carry out the arc tangent phase measurement, obtain incident laser L
1With shoot laser L
2Identified result do
With the phase value that measures
As phase-locked closed-loop control signal input digit controller, through the PZT drive control module cavity length is carried out meticulous quick adjustment, the output light phase of FEEDBACK CONTROL laser module
Make
Be tending towards 0, when
The time, the lock phase control procedure of laser module is accomplished, its shoot laser L
2Phase locking be incident laser L
1Phase place, promptly
Step 9, when optics phase locked track system losing lock, repeating step six to eight, the shoot laser L of laser module
2Can be to incident laser L
1Carry out phase locked track again.
2. realize the described a kind of device of claim 1 based on the technological optics phase locked track method of four-way laser frequency discrimination phase demodulation; It is characterized in that; It comprises the 1/1st wave plate (1); First polarization splitting prism (2); The 1/2nd wave plate (3); Depolarization Amici prism (4); Second polarization splitting prism (5); First high-speed photodetector (6); Second high-speed photodetector (7); Optical phase delay device (8); The 3rd polarization splitting prism (9); The 3rd high-speed photodetector (10); The 4th high-speed photodetector (11); Signal condition module (12); Frequency measurement module (13); Quadrature phase demodulation module (14); Digitial controller (15); Temperature control modules (16); PZT drive control module (17); Laser module (18); The 1/3rd wave plate (19) and the 4th polarization splitting prism (20)
Incident laser is transmitted through first polarization splitting prism (2) through the 1/1st wave plate (1),
The shoot laser that laser module (18) sends is transmitted through the 4th polarization splitting prism (20) through the 1/3rd wave plate (19); The folded light beam of the 4th polarization splitting prism (20) be transmitted to first polarization splitting prism (2) incident laser form close the light light beam; The said light light beam that closes is transmitted through depolarization Amici prism (4) through the 1/2nd wave plate (3); The reflection of depolarization Amici prism (4) is closed the light light beam and is incident to second polarization splitting prism (5); The folded light beam of second polarization splitting prism (5) is incident to first high-speed photodetector (6), and the transmitted light beam of second polarization splitting prism (5) is incident to second high-speed photodetector (7)
The transmission of depolarization Amici prism (4) is closed the light light beam and is incident to optical phase delay device (8); Optical phase delay device (8) postpones light beam and is incident to the 3rd polarization splitting prism (9); The folded light beam of the 3rd polarization splitting prism (9) is incident to the 3rd high-speed photodetector (10); The transmitted light beam of the 3rd polarization splitting prism (9) is incident to the 4th high-speed photodetector (11)
The electric signal of the collection of first high-speed photodetector (6), second high-speed photodetector (7), the 3rd high-speed photodetector (10) and the 4th high-speed photodetector (11) is exported to four signal input parts of signal condition module (12) respectively; The folded light beam difference signal output terminal of signal condition module (12) links to each other with the input end of frequency measurement module (13) and the input end of quadrature phase demodulation module (14) simultaneously; The transmitted light beam difference signal output terminal of signal condition module (12) links to each other with the input end of frequency measurement module (13) and the input end of quadrature phase demodulation module (14) simultaneously; The output terminal of frequency measurement module (13) links to each other with the first input end of digitial controller (15); The output terminal of quadrature phase demodulation module (14) links to each other with second input end of digitial controller (15); The control temperature signal output terminal of digitial controller (15) links to each other with the input end of temperature control modules (16); The output terminal of temperature control modules (16) links to each other with first control end of laser module (18); The PZT drive signal output terminal of digitial controller (15) links to each other with the input end of PZT drive control module (17), and the output terminal of PZT drive control module (17) links to each other with the PZT drive signal control end of laser module (18).
3. a kind of implement device according to claim 2 based on the technological optics phase locked track method of four-way laser frequency discrimination phase demodulation; It is characterized in that optical phase delay device (8) is wave plate phase delay device, reflective phase delay mirror, liquid crystal phase delay device or electric light phase shifter.
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| CN1584535A (en) * | 2004-05-31 | 2005-02-23 | 中国科学院物理研究所 | Method and apparatus for measuring beat frequency of low light level light source |
| JP2007212427A (en) * | 2006-01-16 | 2007-08-23 | Tokyo Univ Of Agriculture & Technology | Optical frequency detecting apparatus, optical spectrum analyzer and optical signal processor |
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| CN1584535A (en) * | 2004-05-31 | 2005-02-23 | 中国科学院物理研究所 | Method and apparatus for measuring beat frequency of low light level light source |
| JP2007212427A (en) * | 2006-01-16 | 2007-08-23 | Tokyo Univ Of Agriculture & Technology | Optical frequency detecting apparatus, optical spectrum analyzer and optical signal processor |
| CN101216314A (en) * | 2008-01-14 | 2008-07-09 | 浙江大学 | Resonance type optical gyroscope digital closed loop system frequency feedback and tracking locking apparatus and method |
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