CN113078548A - Laser frequency stabilizing device and method based on delay difference feedforward - Google Patents
Laser frequency stabilizing device and method based on delay difference feedforward Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
- H01S3/137—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity for stabilising of frequency
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5059—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input
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- H—ELECTRICITY
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- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5059—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input
- H04B10/50595—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input to control the modulator DC bias
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5059—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input
- H04B10/50597—Laser transmitters using external modulation using a feed-forward signal generated by analysing the optical or electrical input to control the phase of the modulating signal
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Abstract
The present disclosure provides a laser frequency stabilization device based on delay difference feedforward, including: an optical signal generating unit comprising: the optical coupler is used for dividing the optical carrier into two light beams; the delay difference unit is used for delaying and frequency shifting the first light beam and outputting an intermediate frequency signal through photoelectric conversion; the phase-locked control unit is used for carrying out phase discrimination, filtering and gain processing on the intermediate-frequency signal to obtain an error control signal; the optical signal generating unit further includes: the adjustable light delay line is used for delaying the second light beam so as to enable the delay of the second light beam to be matched with the path delay of the first light beam converted into the error control signal, and a delayed light wave signal is obtained; the voltage-controlled microwave source is used for generating a driving signal under the excitation of the error control signal; and the optical modulator is used for carrying out frequency shift processing on the delayed optical wave signal under the modulation of the driving signal to obtain a target optical signal. The disclosure also provides a laser frequency stabilization method based on the delay difference feedforward.
Description
Technical Field
The disclosure relates to the field of coherent communication and laser radar, in particular to a laser frequency stabilizing device and method based on delay difference feedforward.
Background
Today, the ever increasing internet traffic leads to a proliferation of demands for high speed optical fiber transmission systems at bit rates of 100Gbit/s and higher. Higher order modulation and digital coherent detection are considered promising techniques to improve next generation optical fiber network capacity and spectral efficiency. Thus, the requirements for high frequency stable light sources will become more stringent when denser constellations are applied. In addition, other applications such as fiber sensing, phased array antenna systems, and coherent lidar systems also require high frequency stability light sources.
Due to noise inside the laser, such as spontaneous emission noise, excitation power noise, and the like, and external influences, such as temperature, vibration, atmospheric changes, and the like, the cavity length inside the laser changes, and thus the frequency of the laser is unstable. The traditional frequency stabilization method comprises saturated absorption frequency stabilization, wavelength modulation frequency stabilization, modulation spectrum frequency stabilization, modulation transfer spectrum frequency stabilization, bicolor laser frequency stabilization, frequency voltage conversion frequency stabilization and the like, but the methods have the problems of additional noise introduction or complex and expensive link, and all use a feedback technology, so that real-time correction cannot be realized, the frequency stabilization of a single-frequency laser can be realized, the frequency stabilization and linearity improvement of linear frequency modulation light cannot be realized, and the miniaturization and integration cannot be realized easily.
Disclosure of Invention
In order to overcome the defects in the conventional laser frequency stabilizing device, the disclosure provides a laser frequency stabilizing device based on delay difference feedforward and a method thereof.
A first aspect of the present disclosure provides a laser frequency stabilization apparatus based on delayed differential feedforward, including: an optical signal generating unit comprising: the first optical coupler is used for dividing the optical carrier into two light beams; the delay difference unit is used for delaying and frequency shifting the first light beam and outputting an intermediate frequency signal through photoelectric conversion; the phase-locked control unit is used for carrying out phase discrimination, filtering and gain processing on the intermediate-frequency signal to obtain an error control signal; wherein, this optical signal produces the unit and still includes: the adjustable light delay line is used for delaying the second light beam so as to enable the delay of the second light beam to be matched with the path delay of the first light beam converted into the error control signal, and a delayed light wave signal is obtained; a voltage controlled microwave source for generating a drive signal under excitation of the error control signal; and the first optical modulator is used for carrying out frequency shift processing on the delayed optical wave signal under the modulation of the driving signal to obtain a target optical signal.
Further, the first optical modulator is an acousto-optic modulator or a dual polarization quadrature phase shift keying modulator.
Further, the first light modulator includes: a mach-zehnder modulator and an optical filter.
Further, the first optical coupler is a fiber coupler or a spatial optical coupler.
Further, the voltage-controlled microwave source is a voltage-controlled direct digital signal frequency synthesizer or a voltage-controlled oscillator.
Further, the error control signal is a dc control signal.
A second aspect of the present disclosure provides a laser frequency stabilization method based on delayed differential feedforward, including: s1, splitting the optical carrier into a first beam and a second beam; s2, delaying and frequency shifting the first light beam, and outputting an intermediate frequency signal through photoelectric conversion; s3, performing phase discrimination, filtering and gain processing on the intermediate frequency signal to obtain an error control signal; s4, delay the second light beam to match the delay of the second light beam with the path delay of the first light beam converted into error control signal, to obtain delayed light wave signal; s5, generating a driving signal under the excitation of the error control signal by adopting a voltage-controlled microwave source; and S6, under the modulation of the driving signal, the delayed optical wave signal is subjected to frequency shift processing to obtain a target optical signal.
Further, S6 includes: s61, performing frequency shift processing on the delayed optical wave signal by adopting a Mach-Zehnder modulator under the modulation of the driving signal; and S62, filtering the optical wave signal after the frequency shift processing by using an optical filter to obtain a target optical signal.
Further, S2 includes: s21, splitting the first light beam to obtain a third light beam and a fourth light beam; s22, performing frequency shift processing on the third light beam to obtain a frequency-shifted third light beam; delaying the fourth light beam to obtain a delayed fourth light beam; s23, combining the frequency-shifted third light beam and the delayed fourth light beam to obtain an optical signal; and S24, performing photoelectric conversion and power amplification on the optical signal to obtain an intermediate frequency signal.
Further, S3 includes: s31, obtaining a phase error signal according to the intermediate frequency signal and the reference signal; s32, performing high-frequency filtering processing on the phase error signal to obtain a filtered phase error signal; and S33, performing gain processing on the filtered phase error signal to obtain an error control signal.
Compared with the prior art, the method has the following beneficial effects:
(1) the instantaneous frequency drift of the laser can be compensated in real time by a feed-forward method matched with delay, and the effect is better compared with the traditional delay feedback frequency locking method.
(2) The stability of the instantaneous frequency of the single-frequency laser and the linear frequency modulation laser is realized, so that the line width of the laser is narrowed, and the linearity and the coherence of the frequency modulation laser can be ensured.
(3) The device has simple link structure, is easy to operate, reduces the complexity of hardware, and is easy to miniaturize and integrate.
Drawings
For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
fig. 1 schematically shows a schematic structural diagram of a laser frequency stabilization device based on delayed differential feedforward according to an embodiment of the present disclosure;
FIG. 2 schematically illustrates a flow diagram of a method for laser frequency stabilization based on delayed differential feedforward according to an embodiment of the present disclosure;
FIG. 3 is a flow chart of frequency-shifting the delayed optical wave signal to obtain a target optical signal according to an embodiment of the present disclosure;
fig. 4 schematically illustrates a flow chart for obtaining an intermediate frequency signal according to an embodiment of the present disclosure;
fig. 5 schematically shows a flow chart for obtaining an error control signal according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
Fig. 1 schematically shows a structural diagram of a laser frequency stabilization device based on delayed differential feedforward according to an embodiment of the present disclosure.
As shown in fig. 1, the laser frequency stabilization device based on the delayed differential feedforward comprises:
the optical signal generating unit 10 includes: a laser 101 for generating an optical carrier; a first optical coupler 102, the input end of which is connected to the output end of the laser 101, for dividing the optical carrier into two light beams; a delay difference unit 20 for performing delay and frequency shift processing on the first light beam and outputting an intermediate frequency signal through photoelectric conversion; the phase-locked control unit 30 is configured to perform phase discrimination, filtering, and gain processing on the intermediate-frequency signal to obtain an error control signal, where the error control signal is a direct-current control signal; wherein, the optical signal generating unit 10 further includes: an input end of the tunable optical delay line 103 is connected to the first output end of the first optical coupler 102, and is configured to perform delay processing on the second light beam, so that a delay of the second light beam matches a path delay experienced by the error control signal output by the phase-locked control unit 30 when the first light beam is converted to the second light beam, and a delayed optical wave signal is obtained; a voltage-controlled microwave source 104, an input end of which is connected to an output end of the phase-locked control unit 30, for generating a driving signal D1 under excitation of the error control signal; and the input end of the first optical modulator 105 is connected to the input end of the tunable optical delay line 103, and is configured to perform frequency shift processing on the delayed optical wave signal under the modulation of the driving signal D1, so as to compensate the phase fluctuation of the second optical beam in real time by using the frequency phase information of the first optical beam, and obtain a target optical signal.
In the embodiment of the present disclosure, the laser 101 may be a single-frequency laser or a linear frequency-swept laser. The output laser wavelength can be slowly tuned through temperature or piezoelectric ceramic, the output laser wavelength range is 1534 nm-1564 nm, the laser line width is less than or equal to 400kHz, the side mode suppression ratio is greater than 46dB, the relative intensity noise is less than-130 dBc/Hz @10MHz, and when the frequency is required to be swept quickly, the frequency sweep bandwidth is greater than 10 GHz.
Specifically, as shown in fig. 1, the delay difference unit 20 includes: a second optical coupler 201 for splitting the second light beam into two light beams to obtain a third light beam and a fourth light beam; a first signal source 202 for generating a driving signal D2; the input end of the second optical modulator 203 is connected to the first output end of the second optical coupler 201, and is configured to perform frequency shift processing on the third light beam to obtain a frequency-shifted third light beam; an input end of the optical delayer 204 is connected to the second output end of the second optical coupler 201, and is configured to perform delay processing on the fourth light beam to obtain a delayed fourth light beam; a third optical coupler 205, a first input end and a second input end of which are respectively connected to the output ends of the second optical modulator 203 and the optical delay 204, and configured to combine the frequency-shifted third light beam and the delayed fourth light beam to obtain an optical signal; an input end of the optical detector 206 is connected to an output end of the third optical coupler 205, and is configured to perform photoelectric conversion on the optical signal to obtain an optical signal after the photoelectric conversion; and an electrical amplifier 207, an input end of which is connected to an output end of the optical detector 206, for performing power amplification on the optical signal after the electro-optical conversion to obtain an intermediate frequency signal.
Specifically, as shown in fig. 1, the phase-lock control unit 30 includes: a second signal source 301 for generating a reference signal R; a digital phase discriminator 302, a first input terminal of which is connected to the output terminal of the second signal source 301, and a second input terminal of which is connected to the output terminal of the electrical amplifier 207, for obtaining a phase error signal according to the intermediate frequency signal and the reference signal R; a low-pass filter 303, an input end of which is connected to an output end of the digital phase discriminator 302, and configured to perform high-frequency filtering processing on the phase error signal to obtain a filtered phase error signal; and an input end of the gain controller 304 is connected to the output end of the low-pass filter 303, and is configured to perform gain processing on the filtered phase error signal to obtain an error control signal. Wherein the output terminal of the low pass filter 303 is connected to the input terminal of the voltage controlled microwave source 104.
In an embodiment of the present disclosure, the optical retarder 204 may be a fiber retarder formed of an optical fiber. Because the loss of the optical fiber is very low, the long delay difference is easy to realize, the phase discrimination sensitivity in the device can be improved, and the phase locking performance is improved. In addition, different signal delays can be realized by different optical fiber lengths, and the optical fiber length design can be set according to specific practical application.
In an embodiment of the disclosure, the first optical modulator and the second optical modulator are acousto-optic modulators or dual-polarization quadrature phase shift keying modulators. Wherein, use acousto-optic modulator (AOM) as first optical modulator 105 and second optical modulator 203, because AOM has very high extinction ratio, can suppress the signal of light carrier frequency by a wide margin to reduce the spurious power who produces the signal, promote the in-band spurious suppression ratio. The first optical modulator 105 and the second optical modulator 203 are dual-polarization quadrature phase shift keying optical modulators, which operate in a single-sideband modulation mode of carrier suppression by adjusting a bias point, but the device has a case where suppression of the carrier and the sideband is incomplete, an in-band spurious suppression ratio of a corresponding generated signal is seriously deteriorated, and an operation is complicated.
In other embodiments, the first optical modulator 105 and the second optical modulator 203 may also be equivalently formed by a mach-zehnder modulator in combination with an optical filter, wherein the carrier-suppressed single sideband modulation is achieved by adjusting the minimum bias point to achieve carrier-suppressed double sideband modulation, and then filtering one of the optical carriers through the optical filter.
In the embodiment of the present disclosure, the first optical coupler 101, the second optical coupler 201, and the third optical coupler 205 may be fiber couplers or spatial optical couplers, and the splitting ratio is 1: 1, insertion loss is below 1 dB.
In the disclosed embodiment, the voltage controlled microwave source 104 is a voltage controlled direct digital signal frequency synthesizer or a voltage controlled oscillator. A voltage-controlled direct digital signal frequency synthesizer is adopted as the voltage-controlled microwave source 104, and the voltage-controlled direct digital signal frequency synthesizer has the advantages of stable signal frequency, low phase noise and easy realization of high-frequency stable low-phase noise optical carrier. The voltage-controlled oscillator is used as the voltage-controlled microwave source 104 to realize the feedforward control of the laser frequency error signal, but the voltage-controlled oscillator has poor frequency stability and high phase noise, which affects the performance of the target optical carrier, and has the advantage lower than the voltage-controlled direct digital signal frequency synthesizer.
In the embodiment of the disclosure, the first signal source 202 and the second signal source 301 need to be kept synchronous, so that the signals generated by the two signal sources have a definite phase relationship, and it is ensured that the optical carrier of the laser is coherent with the phase of the signal source after normal operation, thereby realizing the stability of the optical carrier frequency and the locking of the phase. When the laser 101 is a single-frequency laser, the signal frequencies of the first signal source 202 and the second signal source 301 are kept consistent, but the phase orthogonality of the intermediate frequency signal and the reference signal R is ensured; when the laser 101 is a linear swept-frequency laser, the signal frequencies of the first signal source 202 and the second signal source 301 are different, and the parameter of the reference signal R needs to be adjusted to make the intermediate frequency signal and the reference signal R have the same frequency and orthogonal phase, where the frequency of R to be changed is the product of the frequency modulation rate k of the laser and the delay difference τ of the third beam and the fourth beam.
In the embodiment of the disclosure, the amplitude value influences the final output resultTo a small extent, neglecting the amplitude in the following theoretical derivation, in the optical signal generating unit 10, taking the linear frequency-modulated laser 101 as an example, the optical carrier at the output point of the linear frequency-modulated laser 101 is divided into the first optical beam OC by the first optical coupler 10211And a second light beam OC12Which satisfies the following relation:
wherein f is1And
respectively, the frequency and the phase of the output signal of the chirped laser 101, k represents the frequency modulation rate of the output signal of the chirped laser 101, j is an imaginary number, and t is time.
First light beam OC11The third light beam and the fourth light beam are obtained by splitting through the second optical coupler 201, and the third light beam and the fourth light beam pass through the optical link and then are output as an optical signal OC from the third optical coupler 2053The following relationship is satisfied:
OC3(t)＝OC11(t-τ)+OC11(t)×exp(j2πfRF1t) (2)
wherein f isRF1Representing the frequency of the driving signal of the second optical modulator 203, τ represents the delay time of the optical delayer, and it can be obtained that the electro-optically converted optical signal output by the optical detector 206 satisfies the following relationship:
wherein, d.c. represents the dc component outputted after the photoelectric conversion, which can be filtered by the band-limited electrical amplifier 207, the optical signal after the photoelectric conversion gets the intermediate frequency signal after passing through the electrical amplifier, in the phase-locked control unit 30, the frequency of the reference signal R generated by the second signal source 301 is set as f1+ k τ, the same frequency as the intermediate frequency signal; when k is 0, the phase lock of the single-frequency laser 101 is set,the phase error signal P output by the digital phase detector 302 can be expressed as:
wherein the content of the first and second substances,
representing the constant phase of the phase error signal P by setting the initial phase of the reference signal R
Wherein m is 0, ± 1, ± 2, ± 3, ….
When the delay τ is small, equation 4 can be approximated as:
thus, the second light beam OC12Enters the first optical modulator 105 after matching delay and is modulated by a driving signal D1 to obtain a modulated target optical signal OCm2The following relationship is satisfied:
wherein f isRF2For the initial frequency of the voltage controlled direct digital signal frequency synthesizer 104, g is the loop gain, k, provided by the gain controller 304vFor voltage controlled slew rates of the direct digital signal frequency synthesizer 104, it can be seen that 2 π k is satisfiedvWhen g τ is 1, the phase error of the laser 101 will be eliminated, so as to stabilize the instantaneous frequency of the laser 101.
According to the laser frequency stabilizing device based on the delay difference feedforward, instantaneous frequency jitter of a laser is compensated in real time through a feedforward method, and therefore a target optical carrier signal with stable frequency is obtained.
Fig. 2 schematically illustrates a flow chart of a method for laser frequency stabilization based on delayed differential feed forward according to an embodiment of the present disclosure.
As shown in fig. 2, the method for stabilizing the frequency of the laser based on the delayed differential feedforward includes:
s1, the optical carrier is divided into a first beam and a second beam.
S2, the first beam is delayed and shifted, and an intermediate frequency signal is output by photoelectric conversion.
And S3, performing phase discrimination, filtering and gain processing on the intermediate frequency signal to obtain an error control signal.
S4, the second light beam is delayed to match the delay of the second light beam with the path delay experienced by the first light beam converted into the error control signal, so as to obtain a delayed lightwave signal.
And S5, generating a driving signal under the excitation of the error control signal by using a voltage-controlled microwave source.
And S6, under the modulation of the driving signal, the delayed optical wave signal is subjected to frequency shift processing to obtain a target optical signal.
In the embodiment of the present disclosure, as shown in fig. 3, S6 specifically includes:
and S61, performing frequency shift processing on the delayed optical wave signal under the modulation of the driving signal by using the Mach-Zehnder modulator.
And S62, filtering the optical wave signal after the frequency shift processing by using an optical filter to obtain a target optical signal.
In the embodiment of the present disclosure, as shown in fig. 4, S2 specifically includes:
s21, the first light beam is split to obtain a third light beam and a fourth light beam.
S22, performing frequency shift processing on the third light beam to obtain a frequency-shifted third light beam; and performing delay processing on the fourth light beam to obtain a delayed fourth light beam.
And S23, combining the frequency-shifted third light beam and the delayed fourth light beam to obtain an optical signal.
And S24, performing photoelectric conversion and power amplification on the optical signal to obtain an intermediate frequency signal.
In the embodiment of the present disclosure, as shown in fig. 5, S3 specifically includes:
and S31, obtaining a phase error signal according to the intermediate frequency signal and the reference signal.
And S32, performing high-frequency filtering processing on the phase error signal to obtain a filtered phase error signal.
And S33, performing gain processing on the filtered phase error signal to obtain an error control signal.
In the embodiments of the present disclosure, each method step corresponds to each module in the above-described embodiment device, and specific parameters, connection relationships, and the like of each module are not described in detail here.
It should be noted that the structure of the apparatus provided in the above embodiments does not constitute a limitation to the present apparatus, the module structure, connection relationship, and the like in the apparatus may be modified according to actual situations, and the configuration of the device may be more complicated or simpler.
Those skilled in the art will appreciate that various combinations and/or combinations of features recited in the various embodiments and/or claims of the present disclosure can be made, even if such combinations or combinations are not expressly recited in the present disclosure. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present disclosure may be made without departing from the spirit or teaching of the present disclosure. All such combinations and/or associations are within the scope of the present disclosure.
While the disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.
Claims (10)
1. A laser frequency stabilization apparatus based on delayed differential feed forward, comprising:
an optical signal generating unit comprising: the first optical coupler is used for dividing the optical carrier into two light beams;
the delay difference unit is used for delaying and frequency shifting the first light beam and outputting an intermediate frequency signal through photoelectric conversion;
the phase-locked control unit is used for carrying out phase discrimination, filtering and gain processing on the intermediate-frequency signal to obtain an error control signal;
wherein the optical signal generating unit further comprises:
the adjustable optical delay line is used for delaying the second light beam so as to enable the delay of the second light beam to be matched with the path delay of the first light beam converted into the error control signal, and a delayed light wave signal is obtained;
a voltage controlled microwave source for generating a drive signal under excitation of the error control signal;
and the first optical modulator is used for performing frequency shift processing on the delayed optical wave signal under the modulation of the driving signal to obtain a target optical signal.
2. The delayed differential feedforward-based laser frequency stabilization device of claim 1, wherein the first optical modulator is an acousto-optic modulator or a dual-polarization quadrature phase shift keying modulator.
3. The delayed differential feedforward-based laser frequency stabilization device of claim 1, wherein the first optical modulator comprises: a mach-zehnder modulator and an optical filter.
4. The delay differential feedforward-based laser frequency stabilization device according to claim 1, wherein the first optical coupler is a fiber coupler or a spatial optical coupler.
5. The delayed differential feedforward-based laser frequency stabilization device of claim 1, wherein the voltage-controlled microwave source is a voltage-controlled direct digital signal frequency synthesizer or a voltage-controlled oscillator.
6. The delayed differential feedforward-based laser frequency stabilization device of claim 1, wherein the error control signal is a direct current control signal.
7. A laser frequency stabilization method based on delay difference feedforward is characterized by comprising the following steps:
s1, splitting the optical carrier into a first beam and a second beam;
s2, delaying and frequency shifting the first light beam, and outputting an intermediate frequency signal through photoelectric conversion;
s3, performing phase discrimination, filtering and gain processing on the intermediate frequency signal to obtain an error control signal;
s4, performing delay processing on the second light beam to match the delay of the second light beam with the path delay experienced by the first light beam converted into the error control signal, so as to obtain a delayed lightwave signal;
s5, generating a driving signal under the excitation of the error control signal by adopting a voltage-controlled microwave source;
and S6, under the modulation of the driving signal, performing frequency shift processing on the delayed optical wave signal to obtain a target optical signal.
8. The method for laser frequency stabilization based on delayed differential feedforward according to claim 7, wherein the S6 includes:
s61, performing frequency shift processing on the delayed lightwave signal by adopting a Mach-Zehnder modulator under the modulation of the driving signal;
and S62, filtering the optical wave signal after the frequency shift processing by using an optical filter to obtain a target optical signal.
9. The method for laser frequency stabilization based on delayed differential feedforward according to claim 7, wherein the S2 includes:
s21, splitting the first light beam to obtain a third light beam and a fourth light beam;
s22, performing frequency shift processing on the third light beam to obtain a frequency-shifted third light beam; delaying the fourth light beam to obtain a delayed fourth light beam;
s23, combining the frequency-shifted third light beam and the delayed fourth light beam to obtain an optical signal;
and S24, performing photoelectric conversion and power amplification on the optical signal to obtain an intermediate frequency signal.
10. The method for laser frequency stabilization based on delayed differential feedforward according to claim 7, wherein the S3 includes:
s31, obtaining a phase error signal according to the intermediate frequency signal and the reference signal;
s32, performing high-frequency filtering processing on the phase error signal to obtain a filtered phase error signal;
and S33, performing gain processing on the filtered phase error signal to obtain an error control signal.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN114204997A (en) * | 2021-11-24 | 2022-03-18 | 北京印刷学院 | Optical generation method and device for 32 frequency doubling millimeter wave signal |
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| CN114205003A (en) * | 2021-12-09 | 2022-03-18 | 北京邮电大学 | Fast and slow loop combined feedback control system and method for locking signal light and local oscillator light frequency difference signal of optical fiber link |
| CN114205003B (en) * | 2021-12-09 | 2023-10-20 | 北京邮电大学 | Fast and slow loop combined feedback control system and method for locking signal light and local oscillation optical frequency difference signal of optical fiber link |
| CN113922872A (en) * | 2021-12-14 | 2022-01-11 | 广州汇信特通信技术股份有限公司 | Optical amplitude modulation and demodulation system based on 5G transmission |
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