Reverse transmission optical frequency synthesis device

Abstract

The invention discloses a reverse transmission optical frequency synthesis device, which comprises a user side, a reference laser side and an optical fiber, and is characterized in that the user side comprises target laser and a noise elimination module, and the reference laser side comprises reference laser and an optical frequency synthesis system. A user side can directly use laser after optical frequency synthesis, and an additional laser is not needed for further phase-locked amplification; after a laser signal of the user side is transmitted to the reference laser side, optical frequency synthesis of the reference laser side and optical fiber noise elimination of the user side are synchronously carried out; an optical fiber noise elimination system of a user end collects noise at an output port of an application system and samples noise at a reference laser end and a phase-locked output port of reference laser, end-to-end laser phase elimination can be carried out in one step, and the length of a free optical path and the number of the optical fiber noise elimination systems are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical frequency transmission, and in particular relates to a reverse transmission optical frequency synthesis device, which is suitable for the fields of ultra-stable laser distribution and optical clock comparison. Background Art

[0002] High-precision optical clocks (optical atomic clocks) are important measurement tools in modern physics and play a vital role in the development of modern physics. At present, high-precision optical clocks have been widely used in the field of basic physics research, such as testing basic physical constants, verifying special and general relativity, satellite navigation, earth exploration, etc. In order to develop high-stability optical clocks, lasers with higher frequency stability are needed as the local oscillator source of the optical clock. Pound-Drever-Hall (PDH) laser frequency stabilization technology can produce ultra-stable lasers with narrow linewidth, low phase noise, and high frequency stability. However, the operation and maintenance costs of high-stability ultra-stable lasers are high, and they have wavelength restrictions. For example, a single-crystal silicon cavity needs to work in a low-temperature environment cooled by liquid nitrogen or liquid helium, and is only transparent to infrared light with a wavelength of 1.5um. In order to produce high-stability ultra-stable lasers of different wavelengths to meet the needs of different optical clocks or other research, it is necessary to use an optical comb to transfer the linewidth and frequency stability of the reference laser to the required various optical wavelengths through phase-locking technology.

[0003] The existing optical frequency synthesis methods all place the reference laser and the slave laser in the same laboratory for optical frequency synthesis, and then transmit them to the user end for use after the optical frequency synthesis is completed. Optical frequency synthesis and optical frequency transmission are two independent processes, and the laser power is wasted greatly during the optical frequency synthesis and transmission process. In application, the optical power signal received by the user end is limited, and requires secondary amplification or phase-locked amplification, and cannot be used directly. In addition, when performing one-to-many ultra-stable laser distribution, the laser management pressure of the reference laser end platform is large. If optical frequency transmission and optical frequency synthesis are combined to realize direct optical frequency synthesis of the laser transmitted from the application end to the reference end, it can not only greatly reduce the laser distribution pressure of the launch platform and reduce the number of lasers, but also allow the user end to have a higher degree of freedom in the use of laser frequency. Summary of the invention

[0004] The object of the present invention is to provide a reverse transmission optical frequency synthesis device in view of the above-mentioned problems existing in the prior art.

[0005] The above-mentioned purpose of the present invention is achieved by the following technical means:

[0006] A reverse transmission optical frequency synthesis device comprises a user end, a reference laser end, and an optical fiber, wherein the user end comprises a target laser and a noise elimination module, the reference laser end comprises a reference laser and an optical frequency synthesis system, the noise elimination module comprises a first photodetector, a first optical beam splitter, a first feedback control circuit, a first acousto-optic modulator driver, a first acousto-optic modulator, and a first semi-transmissive semi-reflector, the first optical beam splitter comprises an A input port, a B output port, a C bidirectional port, and a D bidirectional port, the target laser is input from the A input port of the first optical beam splitter, and the B output port of the first optical beam splitter is connected to the input port of the first photodetector , the output port of the first photodetector is connected to the first input port of the first feedback control circuit, the first reference signal is input from the second input port of the first feedback control circuit, the output port of the first feedback control circuit is connected to the input port driven by the first acousto-optic modulator, the output port driven by the first acousto-optic modulator is connected to the radio frequency input port of the first acousto-optic modulator, the C bidirectional port of the first optical beam splitter is connected to the first bidirectional port of the first acousto-optic modulator, the D bidirectional port of the first optical beam splitter is connected to the optical frequency synthesis system through an optical fiber, and the second bidirectional port of the first acousto-optic modulator is connected to the first bidirectional port of the first semi-transmitter and semi-reflector.

[0007] As described above, the A input port and the B output port are optically connected to the C bidirectional port and the D bidirectional port respectively. The optical signal input to the A input port is output from the C bidirectional port and the D bidirectional port; the optical signal input to the C bidirectional port and the D bidirectional port is output from the B output port.

[0008] As described above, the optical frequency synthesis system includes a second acousto-optic modulator, a second acousto-optic modulator driver, a second semi-transmissive semi-reflector, an optical frequency beat signal generating module, and a second feedback control circuit. The D bidirectional port of the first optical beam splitter is connected to the first bidirectional port of the second acousto-optic modulator through an optical fiber, the second bidirectional port of the second acousto-optic modulator is connected to the first bidirectional port of the second semi-transmissive semi-reflector, the second output port of the second semi-transmissive semi-reflector is connected to the first input port of the optical frequency beat signal generating module, the reference laser is input from the second input port of the optical frequency beat signal generating module, the output port of the optical frequency beat signal generating module is connected to the second input port of the second feedback control circuit, the second reference signal is input from the first input port of the second feedback control circuit, the output port of the second feedback control circuit is connected to the input port of the second acousto-optic modulator driver, and the output port of the second acousto-optic modulator driver is connected to the radio frequency input port of the second acousto-optic modulator.

[0009] As described above, after the target laser is split by the first optical beam splitter, the first split light A is input from the D bidirectional port and the optical fiber to the second acousto-optic modulator, the second acousto-optic modulator modulates the first split light A according to the first RF input signal input from the RF input port, to obtain the first modulated light A whose frequency is the sum of the first split light A and the first RF input signal, the first modulated light A is superimposed on the frequency offset caused by the first phase noise generated by the optical fiber link from the first optical beam splitter to the second semi-transmissive semi-reflector, to obtain the second modulated light A whose frequency is the sum of the first modulated light A and the frequency offset caused by the first phase noise, the second modulated light A is input to the second semi-transmissive semi-reflector, the second semi-transmissive semi-reflector outputs a part of the second modulated light A from the second output port to the optical frequency beat signal generating module, the optical frequency beat signal generating module outputs a third RF signal having the same frequency as the beat signal of the second modulated light A and the reference laser, and the second feedback control circuit phase-locks the third RF signal by feedback modulating the first RF input signal.

[0010] As described above, the second semi-transmitter and semi-reflector inputs another part of the second modulated light A to the second acousto-optic modulator, and the second acousto-optic modulator performs secondary modulation on the second modulated light A according to the first RF input signal to obtain a third modulated light A whose frequency is the sum of the frequencies of the second modulated light A and the first RF input signal. The third modulated light A is superimposed with the frequency offset caused by the first phase noise to obtain a fourth modulated light A whose frequency is the sum of the frequencies of the third modulated light A and the frequency offset caused by the first phase noise. The fourth modulated light A is input into the first optical beam splitter from the D bidirectional port.

[0011] As described above, after the target laser is split by the first optical beam splitter, the first split beam B is output from the C bidirectional port to the first acousto-optic modulator. The first acousto-optic modulator modulates the first split beam B according to the second RF input signal input from the RF input port to obtain a first modulated light B whose frequency is the sum of the first split beam B and the second RF input signal. The first modulated light B is superimposed with a frequency offset caused by a second phase noise generated in the optical fiber link from the first optical beam splitter to the first semi-transmitter and semi-reflector to obtain a second modulated light whose frequency is the sum of the first modulated light B and the frequency offset caused by the second phase noise. B, the second modulated light B is input into the first semi-transmissive semi-reflector, the first semi-transmissive semi-reflector re-inputs a part of the second modulated light B into the first acousto-optic modulator, the first acousto-optic modulator performs secondary modulation on the second modulated light B according to the second RF input signal, and obtains a third modulated light B whose frequency is the sum of the second modulated light B and the second RF input signal, the third modulated light B is superimposed with the frequency offset caused by the second phase noise to obtain a fourth modulated light B whose frequency is the sum of the third modulated light B and the frequency offset caused by the second phase noise, and the fourth modulated light B is input into the first optical beam splitter from the D bidirectional port;

[0012] The fourth modulated light A input from the D bidirectional port and the fourth modulated light B input from the C bidirectional port are beat by the first optical beam splitter to obtain the first beat frequency light. The first beat frequency light passes through the first photodetector, and the first photodetector converts the beat frequency signal into a fourth radio frequency signal of the same frequency. The first feedback control circuit phase-locks the fourth radio frequency signal by feedback controlling the second radio frequency input signal; the first semi-transmitter and semi-reflector outputs the other part of the second modulated light B.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) Placing the laser and the fiber noise elimination module at the user end effectively reduces the loss of the laser. The user end can directly use the laser after optical frequency synthesis without the need for further phase-locked amplification with an additional laser, thereby improving the flexibility of laser use at the user end.

[0015] (2) The laser signal at the user end is transmitted to the reference laser end, and the optical frequency synthesis at the reference laser end and the optical fiber noise elimination at the user end are performed synchronously. When the reference laser at the reference laser end needs to realize one-to-many optical frequency transmission, the device and method can effectively reduce the laser management pressure of the optical frequency distribution platform.

[0016] (3) The fiber optic noise elimination system at the user end samples noise at the output port to the application system (i.e., the second phase noise generated in the fiber optic link from the first beam splitter to the first semi-transmitter and semi-reflector) and samples noise at the phase-locked output port between the reference laser end and the reference laser (i.e., the first phase noise generated in the fiber optic link from the first beam splitter to the second semi-transmitter and semi-reflector), thereby performing end-to-end laser phase elimination in one step, reducing the length of the free optical path and the number of fiber optic noise elimination systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of the optical fiber noise elimination module and the optical frequency synthesis system in the device of the present invention;

[0019] Figure 3 This is a structural schematic diagram of an optical frequency beat signal generating module according to Embodiment 1 of the present invention;

[0020] Figure 4 This is a schematic diagram of the structure of an optical frequency beat signal generating module according to Embodiment 2 of the present invention;

[0021] Reference numerals and corresponding component names:

[0022] 1—target laser; 2—optical fiber noise elimination module; 3—optical fiber; 4—reference laser; 5—optical frequency synthesis system; 21—first photodetector; 22—first optical beam splitter; 23—first feedback control circuit; 24—first acousto-optic modulator driver; 25—first acousto-optic modulator; 26—first semi-transparent and semi-reflector; 51—second acousto-optic modulator; 52—second acousto-optic modulator driver; 53—second feedback control circuit; 54—second semi-transparent and semi-reflector; 55—optical frequency beat signal generation module; 551—optical beat generator; 552—second photodetector; 553—optical comb and light beat synthesis module. DETAILED DESCRIPTION

[0023] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below in conjunction with embodiments. The embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0024] Embodiment 1:

[0025] like Figure 1 As shown, a reverse transmission optical frequency synthesis device includes a user end, a reference laser end, and an optical fiber 3, the user end includes a target laser 1 and an optical fiber noise elimination module 2, the reference laser end includes a reference laser 4 and an optical frequency synthesis system 5, the optical fiber noise elimination module 2 includes a first photodetector 21, a first optical beam splitter 22, a first feedback control circuit 23, a first acousto-optic modulator driver 24, a first acousto-optic modulator 25, and a first semi-transmitter and semi-reflector 26, the first optical beam splitter 22 includes an A input port, a B output port, a C bidirectional port, and a D bidirectional port, the A input port and the B output port are optically connected with the C bidirectional port and the D bidirectional port respectively, the optical signal input to the A input port is output from the C bidirectional port and the D bidirectional port; the optical signal input to the C bidirectional port and the D bidirectional port is output from the B output port;

[0026] The target laser 1 is input from the A input port of the first beam splitter 22. The first beam splitter 22 splits the target laser 1 and inputs them into the C bidirectional port and the D bidirectional port respectively. The B output port of the first beam splitter 22 is connected to the input port of the first photodetector 21. The output port of the first photodetector 21 is connected to the first input port of the first feedback control circuit 23. The first reference signal is input from the second input port of the first feedback control circuit 23. The output port of the first feedback control circuit 23 is connected to the input port of the first acousto-optic modulator driver 24. The output port of the first acousto-optic modulator driver 24 is connected to the radio frequency input port of the first acousto-optic modulator 25. The C bidirectional port of the first beam splitter 22 is connected to the first bidirectional port of the first acousto-optic modulator 25. The D bidirectional port of the first beam splitter 22 is connected to the optical frequency synthesis system 5 through the optical fiber 3. The second bidirectional port of the first acousto-optic modulator 25 is connected to the first bidirectional port of the first semi-transmissive semi-reflector 26. The second output port of the first semi-transmissive semi-reflector 26 is connected to the application system.

[0027] The optical frequency synthesis system 5 includes a second AOM 51, a second AOM driver 52, a second semi-transmissive reflector 54, an optical frequency beat signal generating module 55, and a second feedback control circuit 53. The D bidirectional port of the first optical beam splitter 22 is connected to the first bidirectional port of the second AOM 51 through the optical fiber 3, the second bidirectional port of the second AOM 51 is connected to the first bidirectional port of the second semi-transmissive reflector 54, the second output port of the second semi-transmissive reflector 54 is connected to the first input port of the optical frequency beat signal generating module 55, the reference laser 4 is input from the second input port of the optical frequency beat signal generating module 55, the output port of the optical frequency beat signal generating module 55 is connected to the second input port of the second feedback control circuit 53, the second reference signal is input from the first input port of the second feedback control circuit 53, the output port of the second feedback control circuit 53 is connected to the input port of the second AOM driver 52, and the output port of the second AOM driver 52 is connected to the radio frequency input port of the second AOM 51.

[0028] The principle of phase locking and phase noise elimination of the device of the present invention is as follows:

[0029] The first split light A after the target laser 1 at the user end is split by the first optical beam splitter 22 is input from the D bidirectional port and the optical fiber 3 to the first bidirectional port of the second acousto-optic modulator 51 at the reference laser end. The second acousto-optic modulator 51 modulates the first split light A according to the first RF input signal input from the RF input port to obtain a first modulated light A whose frequency is the sum of the first split light A and the first RF input signal. The first modulated light A is superimposed on the frequency offset caused by the first phase noise generated by the optical fiber link from the first optical beam splitter 22 to the second semi-transmissive semi-reflector 54 to obtain a second modulated light A whose frequency is the sum of the first modulated light A and the frequency offset caused by the first phase noise. The second modulated light A is input to the second semi-transmissive semi-reflector 54. The second semi-transmissive semi-reflector 54 outputs a part of the second modulated light A from the second output port to the optical frequency beat signal generating module 55. The optical frequency beat signal generating module 55 outputs a third RF signal with the same frequency as the beat signal of the second modulated light A and the reference laser 4.

[0030] The second feedback control circuit 53 phase-locks the frequency of the third RF signal output by the optical beat frequency signal generating module 55 by feedback modulating the frequency of the output signal of the second feedback control circuit 53 (i.e., the first RF input signal input from the RF input port of the second acousto-optic modulator 51);

[0031] The second transflector 54 inputs another part of the second modulated light A to the second acousto-optic modulator 51, and the second acousto-optic modulator 51 performs secondary modulation on the second modulated light A according to the first RF input signal to obtain a third modulated light A whose frequency is the sum of the second modulated light A and the first RF input signal. The third modulated light A is superimposed with the frequency shift caused by the first phase noise to obtain a fourth modulated light A whose frequency is the sum of the third modulated light A and the frequency shift caused by the first phase noise. The fourth modulated light A is input to the first optical beam splitter 22 from the D bidirectional port;

[0032] The first split beam B of the target laser 1 after being split by the first optical beam splitter 22 is output from the C bidirectional port to the first acousto-optic modulator 25. The first acousto-optic modulator 25 modulates the first split beam B according to the second RF input signal input from the RF input port to obtain a first modulated light B whose frequency is the sum of the first split beam B and the second RF input signal. The first modulated light B is superimposed with the frequency offset caused by the second phase noise generated in the optical fiber link from the first optical beam splitter 22 to the first semi-transmitter and semi-reflector 26 to obtain a second modulated light B whose frequency is the sum of the first modulated light B and the frequency offset caused by the second phase noise. The second modulated light B is input into the first semi-transmissive reflector 26, and the first semi-transmissive reflector 26 re-inputs a part of the second modulated light B into the first acousto-optic modulator 25. The first acousto-optic modulator 25 performs secondary modulation on the second modulated light B according to the second RF input signal to obtain a third modulated light B having a frequency equal to the sum of the second modulated light B and the second RF input signal. The third modulated light B is then superimposed with the frequency offset caused by the second phase noise to obtain a fourth modulated light B having a frequency equal to the sum of the third modulated light B and the frequency offset caused by the second phase noise. The fourth modulated light B is input into the first optical beam splitter 22 from the D bidirectional port;

[0033] The fourth modulated light A input from the D bidirectional port and the fourth modulated light B input from the C bidirectional port are beat by the first optical beam splitter 22 to obtain the first beat frequency light. The first beat frequency light passes through the first photodetector 21. The first photodetector 21 converts the beat frequency signal into a fourth radio frequency signal of the same frequency. The first feedback control circuit 23 phase-locks the fourth radio frequency signal by feedback controlling the second radio frequency input signal. The first semi-transmitter and semi-reflector 26 inputs another part of the second modulated light B into the application system. At this time, the frequency of the second modulated light B input into the application system is only related to the frequency of the reference laser 4, the reference frequency of the reference laser end (that is, the reference frequency of the second reference signal), and the reference frequency of the user end (that is, the reference frequency of the first reference signal), and is independent of the frequency offset caused by the phase noise of the optical fiber link (including the frequency offset caused by the first phase noise and the frequency offset caused by the second phase noise) and the frequency of the target laser 1.

[0034] As an implementable embodiment, the optical frequency beat signal generating module 55 includes an optical beater 551 and a second photodetector 552, the second output port of the second semi-transmitter and semi-reflector 54 is connected to the first input port of the optical beater 551, the reference laser 4 is input from the second input port of the optical beater 551, the output port of the optical beater 551 is connected to the input port of the second photodetector 552, and the output port of the second photodetector 552 is connected to the second input port of the second feedback control circuit 53.

[0035] The optical beater 551 beats the second modulated light A with the reference laser 4, and the second photodetector 552 converts the optical signal after the beat by the optical beater 551 into a third radio frequency signal with the same frequency.

[0036] In this embodiment, the first feedback control circuit 23 controls the second RF input signal by feedback so that the fourth RF signal is locked to the reference frequency of the first reference signal. The second feedback control circuit 53 locks the frequency of the third RF signal to the reference frequency of the second reference signal by feedback modulating the first RF input signal. The frequency of the target laser 1 is recorded as v 1 , the frequency of reference laser 4 is recorded as v 2 The frequency shift caused by the phase noise introduced by the optical fiber link from the first optical beam splitter 22 to the second semi-transmitter and semi-reflector 54 is Δφ 3 ,, the reference frequency of the first reference signal of the first feedback control circuit 23 is f 1 , the second RF input signal is f′ 1 The frequency offset caused by the phase noise introduced in the optical fiber link from the first optical beam splitter 22 to the first semi-transmitter and semi-reflector 26 is Δφ 1 , the reference frequency of the second reference signal of the second feedback control circuit 53 is f 2 , the first RF input signal is f′ 2 ,

[0037] Then the frequency of the first modulated light A is v 1 +f′ 2 ; The frequency of the second modulated light A is v 1 +Δφ 3 +f′ 2 ; The frequency of the third RF signal is f b2 , f b2 =v 1 +Δφ 3 +f′ 2 -v 2 ;

[0038] The second feedback control circuit 53 locks the frequency of the third RF signal to the reference frequency f of the second reference signal. 2 On, that is:

[0039] f 2 =v 1 +Δφ 3 +f′ 2 -v 2

[0040] At this time, the frequency of the second modulated light A in the second transflector 54 is:

[0041] v 1 +Δφ 3 +f′2 =v 2 +f 2 ;

[0042] The frequency of the third modulated light A is v 1 +Δφ 3 +2f′ 2 The frequency of the fourth modulated light A is v 1 +2Δφ 3 +2f′ 2 ; The frequency of the first modulated light B is v 1 +f′ 1 ; The frequency of the second modulated light B is v 1 +Δφ 1 +f′ 1 ; The frequency of the third modulated light B is v 1 +Δφ 1 +2f′ 1 The frequency of the fourth modulated light B is v 1 +2Δφ 1 +2f′ 1 ; The frequency of the first beat frequency light is f b1 , f b1 =(v 1 +2Δφ 1 +2f′ 1 )-(v 1 +2Δφ 3 +2f′ 2 )=2(f′ 1 +Δφ 1 )-2(Δφ 3 +f′ 2 );

[0043] The first feedback control circuit 23 controls the fourth RF input signal by feedback so that f b1 =f 1 , we can get:

[0044]

[0045] At this time, the frequency of the second modulated light B output by the first transflector 26 to the application system is:

[0046]

[0047] The frequency of the second modulated light B input to the application system is the same as the frequency v of the reference laser 4. 2 , the reference frequency f of the reference laser end 2 , and the user-side reference frequency f 1 It is related to the frequency offset caused by the phase noise of the optical fiber link and has nothing to do with the frequency of the target laser 1.

[0048] Embodiment 2:

[0049] As an implementable embodiment, the optical beater 551 can adopt an optical comb optical beat frequency synthesis module 553. When the wavelengths of the target laser 1 and the reference laser 4 at the user end are different, the optical comb optical beat frequency synthesis module 553 can output the beat frequency signal of the reference laser 4 and the target laser 1 based on the optical frequency comb (optical comb); or the beat frequency signal of the optical comb and the target laser 1 after the optical comb is locked to the reference laser 4; or it can be a frequency difference signal synthesized based on the beat frequency signals of the optical comb and the reference laser 4 and the target laser 1 respectively.

[0050] In this embodiment, the frequency of the third RF signal output by the optical frequency beat signal generating module 55 is:

[0051] f b2 =v 1 +Δφ 3 +f′ 2 -kv 2 -f 0

[0052] Where k is the frequency scaling factor of the optical comb beat frequency synthesis module 553, and f 0 is the controlled frequency offset of the optical comb optical beat frequency synthesis module 553, which can be 0 or not.

[0053] After the third RF signal is phase-locked with the second reference signal by the second acousto-optic modulator 51, we have f b2 =f 2 ,Right now:

[0054] v 1 +Δφ 3 +f′ 2 =kv 2 +f 0 +f 2

[0055] The laser frequency on the second semi-transmitter and semi-reflector 54 is v 1 +Δφ 3 +f′ 2 =kv 2 +f o +f 2 ;

[0056] Then the frequency of the laser output by the first semi-transmitter and semi-reflector 26 is:

[0057]

[0058] At this time, the laser frequency from the user end to the application system is the frequency v of the reference laser 4 2 k times of the controlled frequency offset f 0, the reference frequency f of the reference laser end 2 , and the user-side reference frequency f 1 It is related to the frequency offset caused by the phase noise of the optical fiber link and has nothing to do with the frequency of the target laser 1.

[0059] Embodiment 3:

[0060] As an implementation method, the first feedback control circuit 23 and the second feedback control circuit 53 can use frequency division phase locking instead of ordinary phase locking during the phase locking process. In this case, there is k at the reference laser end. 2 f 2 =f b2 ,Right now:

[0061] k 2 f 2 =v 1 +Δφ 3 +f′ 2 -v 2

[0062] On the user side there is f b1 =k 1 f 1 ,Right now:

[0063] k 1 f 1 =2(f′ 1 +Δφ 1 )-2(Δφ 3 +f′ 2 )

[0064] Therefore, the frequency of the laser output by the first semi-transmitter and semi-reflector 26 can be obtained as follows:

[0065]

[0066] Among them, k 1 is the frequency division coefficient of the first feedback control circuit 23; k 2 is the frequency division coefficient of the second feedback control circuit 53.

[0067] It should be noted that the embodiments described in the present invention are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the described embodiments or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims.

Claims

1. A reverse transmission optical frequency synthesis device, comprising a user end, a reference laser end, and an optical fiber (3), characterized in that: The user end comprises a target laser (1) and a noise elimination module (2); the reference laser end comprises a reference laser (4) and an optical frequency synthesis system (5); the noise elimination module (2) comprises a first photodetector (21), a first optical beam splitter (22), a first feedback control circuit (23), a first acousto-optic modulator driver (24), a first acousto-optic modulator (25), and a first semi-transmitter and semi-reflector (26); the first optical beam splitter (22) comprises an A input port, a B output port, a C bidirectional port, and a D bidirectional port; the target laser (1) is input from the A input port of the first optical beam splitter (22); the B output port of the first optical beam splitter (22) is connected to the input port of the first photodetector (21); the output port of the first photodetector (21) is connected to the output port of the first photodetector (21); The output port is connected to the first input port of the first feedback control circuit (23), the first reference signal is input from the second input port of the first feedback control circuit (23), the output port of the first feedback control circuit (23) is connected to the input port of the first acousto-optic modulator driver (24), the output port of the first acousto-optic modulator driver (24) is connected to the radio frequency input port of the first acousto-optic modulator (25), the C bidirectional port of the first optical beam splitter (22) is connected to the first bidirectional port of the first acousto-optic modulator (25), the D bidirectional port of the first optical beam splitter (22) is connected to the optical frequency synthesis system (5) through the optical fiber (3), and the second bidirectional port of the first acousto-optic modulator (25) is connected to the first bidirectional port of the first semi-transmitter (26).

2. The reverse transmission optical frequency synthesizer according to claim 1, characterized in that: The A input port and the B output port are optically connected to the C bidirectional port and the D bidirectional port respectively. The optical signal input to the A input port is output from the C bidirectional port and the D bidirectional port; the optical signal input to the C bidirectional port and the D bidirectional port is output from the B output port.

3. The reverse transmission optical frequency synthesizer according to claim 2, characterized in that: The optical frequency synthesis system (5) comprises a second acousto-optic modulator (51), a second acousto-optic modulator driver (52), a second semi-transmissive reflector (54), an optical frequency beat signal generating module (55), and a second feedback control circuit (53); a D bidirectional port of the first optical beam splitter (22) is connected to a first bidirectional port of the second acousto-optic modulator (51) via an optical fiber (3); a second bidirectional port of the second acousto-optic modulator (51) is connected to a first bidirectional port of the second semi-transmissive reflector (54); a second output port of the second semi-transmissive reflector (54) and the optical frequency beat signal generating module The reference laser (4) is input from the second input port of the optical frequency beat signal generating module (55), the output port of the optical frequency beat signal generating module (55) is connected to the second input port of the second feedback control circuit (53), the second reference signal is input from the first input port of the second feedback control circuit (53), the output port of the second feedback control circuit (53) is connected to the input port of the second acousto-optic modulator driver (52), and the output port of the second acousto-optic modulator driver (52) is connected to the radio frequency input port of the second acousto-optic modulator (51).

4. The reverse transmission optical frequency synthesizer according to claim 3, characterized in that: The target laser (1) is beam-split by the first optical beam splitter (22), and the first split light A is input to the second acousto-optic modulator (51) from the D bidirectional port and the optical fiber (3). The second acousto-optic modulator (51) modulates the first split light A according to the first radio frequency input signal input from the radio frequency input port to obtain the first modulated light A whose frequency is the sum of the first split light A and the first radio frequency input signal. The first modulated light A is superimposed with the frequency offset caused by the first phase noise generated by the optical fiber link from the first optical beam splitter (22) to the second semi-transmitter and semi-reflector (54), and the frequency is obtained. A second modulated light A is a sum of the frequencies of the first modulated light A and the frequency offset caused by the first phase noise, the second modulated light A is input into a second semi-transmissive semi-reflector (54), the second semi-transmissive semi-reflector (54) outputs a portion of the second modulated light A from a second output port to an optical frequency beat signal generating module (55), the optical frequency beat signal generating module (55) outputs a third radio frequency signal having the same frequency as the beat signal of the second modulated light A and the reference laser (4), and the second feedback control circuit (53) performs phase locking on the third radio frequency signal by feedback modulating the first radio frequency input signal.

5. A reverse transmission optical frequency synthesis device according to claim 4, characterized in that: The second transflector (54) inputs another part of the second modulated light A to the second acousto-optic modulator (51), and the second acousto-optic modulator (51) performs secondary modulation on the second modulated light A according to the first radio frequency input signal to obtain a third modulated light A having a frequency that is the sum of the frequencies of the second modulated light A and the first radio frequency input signal. The third modulated light A is superimposed with a frequency offset caused by the first phase noise to obtain a fourth modulated light A having a frequency that is the sum of the frequencies of the third modulated light A and the frequency offset caused by the first phase noise. The fourth modulated light A is input into the first optical beam splitter (22) from the D bidirectional port.

6. A reverse transmission optical frequency synthesizer according to claim 5, characterized in that: The target laser (1) is beam-split by the first optical beam splitter (22), and the first split beam B is output from the C bidirectional port to the first acousto-optic modulator (25). The first acousto-optic modulator (25) modulates the first split beam B according to the second radio frequency input signal input from the radio frequency input port to obtain a first modulated light B having a frequency that is the sum of the first split beam B and the frequency of the second radio frequency input signal. The first modulated light B is superimposed with a frequency offset caused by a second phase noise generated in the optical fiber link from the first optical beam splitter (22) to the first semi-transmitter and semi-reflector (26), to obtain a second modulated light having a frequency that is the sum of the frequency of the first modulated light B and the frequency offset caused by the second phase noise. B, the second modulated light B is input into the first semi-transmissive semi-reflector (26), the first semi-transmissive semi-reflector (26) re-inputs a part of the second modulated light B into the first acousto-optic modulator (25), the first acousto-optic modulator (25) performs secondary modulation on the second modulated light B according to the second radio frequency input signal, and obtains a third modulated light B having a frequency that is the sum of the second modulated light B and the second radio frequency input signal, the third modulated light B is then superimposed with the frequency offset caused by the second phase noise to obtain a fourth modulated light B having a frequency that is the sum of the third modulated light B and the frequency offset caused by the second phase noise, and the fourth modulated light B is input into the first optical beam splitter (22) from the D bidirectional port; The fourth modulated light A input from the D bidirectional port and the fourth modulated light B input from the C bidirectional port are beat by the first optical beam splitter (22) to obtain the first beat frequency light. The first beat frequency light passes through the first photodetector (21). The first photodetector (21) converts the beat frequency signal into a fourth radio frequency signal of the same frequency. The first feedback control circuit (23) performs phase locking on the fourth radio frequency signal by feedback controlling the second radio frequency input signal. The first semi-transmitter and semi-reflector (26) outputs the other part of the second modulated light B.

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