Microwave photon long-distance transmission link phase automatic compensation method and device

Abstract

The invention discloses a microwave photon long-distance transmission link phase automatic compensation method and device, and the method comprises the steps: a modulation signal is loaded on an optical carrier signal outputted by a laser through a cascade modulator, and an optical frequency comb signal outputted by the cascade modulator is divided into two paths after passing through an optical coupler, wherein one path is input into the optical circulator through the first optical filter and is forwards transmitted to the optical reflection module through one path of optical fiber, the optical reflection module reflects back transmitted optical signals, the optical signals are input into the optical circulator and then are output to the first optical detector through the other port of the optical circulator, and radio-frequency signals are output after photoelectric conversion; the other path of optical signal output by the optical coupler is input into the optical modulator through a second optical filter to serve as a carrier signal, and a radio frequency signal is loaded on the optical modulator, is forwards transmitted through another path of optical fiber and is output to a second optical detector through a third optical filter; the method has the advantages of high response speed, system order establishment and large compensation range.

Description

Technical Field

[0001] The present invention relates to the field of microwave signal transmission, and particularly to a method and device for automatically compensating the phase of a microwave photon long-distance transmission link. Background Art

[0002] Highly synchronous time and frequency are the core requirements of modern electronic systems. In modern electronic systems such as time service, navigation and positioning, space TT&C and astronomical observation, mobile communication, and distributed systems, the accuracy and stability of time and frequency synchronization often directly affect and determine the core performance of the system.

[0003] Frequency and time signal transmission methods mainly include wireless transmission, coaxial cable transmission, satellite transmission, optical fiber transmission, etc. The wireless-based signal transmission method mainly uses short-wave signals to reflect signals through the ionosphere in the atmosphere, transmit them through the atmospheric channel to the receiving antenna end, and then compare them with the clock at the receiving end to achieve signal and clock synchronization. However, the distribution, height, and structure of the ionosphere are usually random and are easily affected by factors such as atmospheric turbulence. The delay of the signal reaching the user also changes, resulting in low signal transmission accuracy, and the accuracy of clock synchronization is limited by the stability of the ionosphere.

[0004] The advantage of coaxial cable-based signal transmission is its relatively wide bandwidth, but coaxial cables have large losses, limited long-distance transmission capabilities, and transmission delays are also affected by pressure and temperature. In addition, the cost of laying and maintaining cables is also very high.

[0005] A representative application of satellite-based time and frequency transmission is the global satellite navigation and positioning system for positioning, navigation, etc. The GPS global navigation and positioning system composed of 24 satellites has a highly stable clock reference on each satellite. By synchronizing and encoding each sub-satellite, the encoded signal is transmitted to the receiving station on the ground. Subsequently, the ground station calculates the relative delay based on the received multi-satellite encoded signals, and thus the specific position of the target can be obtained. However, affected by atmospheric disturbances, the stability of the space-ground link is poor, and it often requires long-term averaging to improve the transmission stability, making it difficult to meet the requirements of high-precision frequency transmission, which directly affects the positioning accuracy of the system.

[0006] In summary, traditional frequency transmission methods, such as satellite link transmission, have a long-term stability of 10 -15 order of magnitude; while currently commonly used frequency sources, such as frequency reference local oscillators like optical clocks and atomic clocks, have a long-term stability of up to 10 -16 ~10 -18Magnitude. Compared with the stability of the frequency source, the stability of the traditional frequency transmission method is several orders of magnitude worse, especially the short-term stability is relatively low, which has been difficult to meet the requirements of high-precision microwave / millimeter-wave frequency signal transmission.

[0007] When using microwave dielectrics for long-distance signal transmission, there are problems such as large power loss and limited bandwidth. Optical fibers have the advantages of large bandwidth, low loss, light weight, small volume, and immunity to electromagnetic interference, and are considered the best medium for long-distance transmission of high-frequency microwave signals. With the development of optical communication technology, optical devices and optoelectronic devices have become quite mature, and optical fibers have been widely laid, laying a good foundation for the transmission of frequency signals using optical fibers. However, during the optical fiber transmission process, especially in long-distance optical fiber links, the length and effective refractive index of the optical fiber are also affected by temperature, external stress, and even the rotation of the earth in the environment, resulting in phase distortion of the transmitted signal. In response to this problem, a large number of active phase control and compensation methods have been proposed. For example, a microwave photon Ising machine phase control system disclosed in Chinese Patent Publication No. CN117424649A. However, these systems often have problems such as slow response speed, complex systems, or limited compensation range. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that the existing microwave photon long-distance transmission link phase compensation methods have problems such as slow response speed, complex systems, or limited compensation range.

[0009] The present invention solves the above technical problems through the following technical means: A method for automatically compensating the phase of a microwave photon long-distance transmission link. The modulation signal is loaded onto the optical carrier signal output by the laser through a cascaded modulator. The optical frequency comb signal output by the cascaded modulator is divided into two equal-power optical signals after passing through an optical coupler. One of the optical signals passes through a first optical filter to filter out the optical carrier signal and the first-order sideband signal and is input into an optical circulator. It is forward-transmitted through a section of optical fiber to an optical reflection module. The optical reflection module reflects the transmitted optical signal back, and after being input into the optical circulator, it is output from the other port of the optical circulator to a first optical detector. After photoelectric conversion, a radio frequency signal is output; the other optical signal output by the optical coupler passes through a second optical filter to filter out the optical carrier signal and the third-order sideband signal, and is input into an optical modulator as a carrier signal. The radio frequency signal is loaded onto the optical modulator to modulate the optical carrier signal and the third-order sideband signal. The modulated signal is then forward-transmitted through another section of optical fiber to a third optical filter to filter out the first-order sideband signal and the third-order sideband signal, and is output to a second optical detector for beat frequency output. The above-mentioned filtering out means extracting the corresponding signals.

[0010] Further, the laser outputs a single-wavelength laser signal as the optical carrier signal.

[0011] Furthermore, the frequency of the modulation signal is 1 / 2 of the radio frequency signal frequency to be transmitted.

[0012] Furthermore, the frequency comb interval of the optical frequency comb signal output by the cascaded modulator is the frequency of the loaded modulation signal, and the teeth of the optical frequency comb signal include at least the 1st order sideband signal and the 3rd order sideband signal of the modulation signal.

[0013] Furthermore, the optical reflection module is an optical mirror or another optical circulator.

[0014] Furthermore, the two optical fibers are bundled into one optical cable through optical fiber bundling and then split at the terminal position of the optical cable.

[0015] Furthermore, the expression of the optical frequency comb signal is:

[0016]

[0017] where A is the amplitude of the optical carrier signal, w 0 is the angular frequency of the optical carrier signal, is the initial phase of the optical carrier signal, t is the current time, f m is the radio frequency signal frequency, θ represents the initial phase of the radio frequency signal to be transmitted A 1 、A 3 correspond to the amplitudes of the 1st order and 3rd order sideband signals respectively.

[0018] Even further, the expression of the radio frequency signal e 1u is:

[0019] e 1u = a 1u cos(f m t / 2 + θ / 2 + 2ΔT * f m / 2) = a 1u cos(f m t / 2 + θ / 2 + ΔT * f m )

[0020] where a 1u is the amplitude of the radio frequency signal, and ΔT is the time change after the signal is transmitted through the one-way optical fiber transmission link.

[0021] Even further, the expression of the signal output by the second optical detector through beat frequency is e 0 = a 0 cos(f m t + θ), where a 0 is the amplitude of the signal output by the second optical detector.

[0022] The present invention also provides a phase automatic compensation device for a microwave photon long-distance transmission link. The device applies the above method and includes a laser, a cascaded modulator, an optical coupler, a first optical filter, a second optical filter, an optical circulator, an optical reflection module, a first optical detector, an optical modulator, a third optical filter, and a second optical detector. The laser is connected to the optical coupler via the cascaded modulator. The cascaded modulator receives a modulation signal. The optical coupler is respectively connected to the first optical filter and the second optical filter. The first optical filter is connected to the optical reflection module via the optical circulator and a fiber optic cable. The optical circulator is connected to the optical modulator via the first optical detector. The second optical filter is connected to the third optical filter via the optical modulator and another fiber optic cable. The third optical filter is connected to the second optical detector.

[0023] The advantages of the present invention are as follows:

[0024] (1) The present invention adopts microwave photon technology. By obtaining the phase change in the fiber optic link through a round-trip transmission link, and then through beat frequency pre-modulation, and finally through the way of beat frequency cancellation, it realizes the elimination of the phase change generated by the optical transmission link affected by the environment. The passive compensation method adopted by the system does not require a complex feedback control circuit. The system architecture is a full-analog real-time automatic compensation without digital and signal control, so it has a fast response speed, a large compensation range, and high reliability.

[0025] (2) The radio frequency signal of the present invention undergoes a phase change due to the influence of the environment through a round-trip optical transmission link, and through direct frequency conversion on the optical signal, it realizes the cancellation of the phase change generated by the optical transmission link affected by the environment. Finally, the radio frequency signal output does not have the influence of the phase change in the transmission link, thus ensuring the output of a radio frequency signal with stable phase of the system. The system structure is more compact and is convenient for miniaturization and integration. Description of the Drawings

[0026] Figure 1 It is a schematic structural diagram of a phase automatic compensation device for a microwave photon long-distance transmission link disclosed in an embodiment of the present invention. Detailed Embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Such as Figure 1As shown in the figure, an embodiment of the present invention provides a method and device for automatic phase compensation of a microwave photonic long-distance transmission link. The device includes a laser, a cascaded modulator, an optical coupler, a first optical filter, a second optical filter, a third optical filter, a first optical detector, a second optical detector, an optical modulator, an optical circulator, a transmission optical fiber bundle, an optical reflection module, etc.

[0029] The laser outputs a single-wavelength laser signal as an optical carrier signal and inputs it into the cascaded modulator module. The optical carrier signal E 0 The expression is:

[0030]

[0031] where A is the amplitude of the optical carrier signal, w 0 is the angular frequency of the optical carrier signal, is the initial phase of the optical carrier signal, and t is the current time.

[0032] The modulation signal is loaded onto the optical carrier signal output by the laser through the cascaded modulator. The frequency of the loaded modulation signal is 1 / 2 of the radio frequency signal frequency f m to be transmitted. The optical signal output by the cascaded modulator is an optical frequency comb signal, and the frequency comb interval is the frequency of the loaded modulation signal. The comb teeth include at least the 1st and 3rd sidebands of the modulation signal. The optical frequency comb signal E 1 The expression is:

[0033]

[0034] Only the 1st and 3rd sidebands are retained in the above expression, and other sideband terms are omitted. Where A 1 and A 3 correspond to the amplitudes of the 1st and 3rd sideband signals respectively, and θ represents the initial phase of the radio frequency signal to be transmitted.

[0035] The optical frequency comb signal output by the cascaded modulator is divided into two equal-power optical signals through the optical coupler. One of the optical signals passes through the first optical filter to filter out the optical carrier signal and the 1st sideband signal and inputs it into the optical circulator. After passing through the optical circulator, it is forward transmitted through 1 optical fiber. The forward transmitted optical signal E 1u The expression is:

[0036]

[0037] The above optical signal is input into the optical reflection module after long-distance transmission in the optical fiber. The optical signal is reflected back and continues to be transmitted in the original optical fiber along the original path in the reverse direction. The optical reflection module can be implemented using an optical mirror or an optical circulator, etc.

[0038] The backward-transmitted optical signal is input into the optical circulator and then output from another port of the optical circulator and connected to the first optical detector. After photoelectric conversion, a radio frequency signal is output. Then, the radio frequency signal undergoes a phase change due to the influence of the environment through the round-trip optical transmission link, and the radio frequency signal e 1u The expression is:

[0039] e 1u = a 1u cos( f m t / 2 + θ / 2 + 2ΔT*f m / 2) = a 1u cos( f m t / 2 + θ / 2 + ΔT*f m )

[0040] Among them, a 1u is the amplitude of the radio frequency signal after conversion, and ΔT is the time change after the signal is transmitted through the one-way optical fiber transmission link.

[0041] Another optical signal output by the optical coupler passes through the second optical filter to filter out the optical carrier signal and the third-order sideband signal. This signal is then input into the optical modulator as the carrier signal E 1d , and the expression of the carrier signal E 1d is:

[0042]

[0043] The radio frequency signal after photoelectric conversion output by the aforementioned optical circulator is then loaded onto the optical modulator to modulate the optical carrier signal and the third-order sideband signal. The modulated signal is then forward-transmitted through another optical fiber. The expression of the modulated signal E 2 is:

[0044]

[0045] In the above expression, only the optical carrier signal, the third-order sideband signal, and the first-order sideband signal after the carrier signal is modulated are retained, and other sideband terms are omitted. Among them, B 1 corresponds to the amplitude of the first-order sideband signal after the carrier signal is modulated.

[0046] The aforementioned forward-transmitted modulated signal E 2 After long-distance optical fiber transmission, the expression of E 2 becomes:

[0047]

[0048] The above optical signal is input into the third optical filter to filter out the first-order sideband signal and the third-order sideband signal, and then output to the second optical detector for beat frequency output. The expression of its output signal e 0 is:

[0049]

[0050] Thereby, the phase change generated by the influence of the environment on the optical transmission link is offset, and the phase change in the transmission link does not exist in the finally output radio frequency signal, thereby ensuring the output of a radio frequency signal with stable system phase. The finally output radio frequency signal is twice the frequency of the modulation signal. Wherein, a 0 is the amplitude of the signal output by the second optical detector.

[0051] It should be noted that the two forward-transmitted optical signals are respectively transmitted through different optical fibers, but the two optical fibers are bundled in one optical cable through optical fiber bundling to ensure that the temperature, stress and other environments of the two optical fibers are the same during long-distance transmission. After being transmitted to the final position, they are split again, and the separated optical fibers are ensured to be as short as possible.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for automatic phase compensation of a microwave photon long-distance transmission link, characterized in that: The modulation signal is loaded on the optical carrier signal output by the laser through the cascade modulator. The optical frequency comb signal output by the cascade modulator is divided into two optical signals of equal power after passing through the optical coupler. One optical signal passes through the first optical filter, filters out the optical carrier signal and the first-order sideband signal, and inputs into the optical circulator, and is forwarded to the optical reflection module through an optical fiber. The optical reflection module reflects the transmitted optical signal back, inputs into the optical circulator, and then outputs from the other port of the optical circulator to the first optical detector, and outputs the radio frequency signal after photoelectric conversion; the other optical signal output by the optical coupler passes through the second optical filter, filters out the optical carrier signal and the third-order sideband signal, and is input into the optical modulator as the carrier signal. The radio frequency signal is loaded on the optical modulator, and the optical carrier signal and the third-order sideband signal are modulated. The modulated signal is then forwarded to the third optical filter through another optical fiber, and the first-order sideband signal and the third-order sideband signal are filtered out, and output to the second optical detector for beat frequency output.

2. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The laser outputs a single-wavelength laser signal as an optical carrier signal.

3. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The frequency of the modulation signal is 1 / 2 of the frequency of the radio frequency signal to be transmitted.

4. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The frequency comb interval of the optical frequency comb signal output by the cascade modulator is the frequency of the loaded modulation signal, and the comb teeth of the optical frequency comb signal at least include the first-order sideband signal and the third-order sideband signal of the modulation signal.

5. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The light reflection module is a light reflection mirror or another light circulator.

6. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The two optical fibers are bundled in one optical cable through optical fibers and then split at the terminal position of the optical cable.

7. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 1, characterized in that: The optical frequency comb signal expression is: Where A is the amplitude of the optical carrier signal, w0 is the angular frequency of the optical carrier signal, is the initial phase of the optical carrier signal, t is the current time, f m is the RF signal frequency, θ represents the initial phase of the transmitted RF signal, and A1 and A3 correspond to the amplitudes of the 1st-order and 3rd-order sideband signals, respectively.

8. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 7, characterized in that: The radio frequency signal e 1u The expression is: e 1u =a 1u cos(f m t / 2+θ / 2+2ΔT*f m / 2)=a 1u cos(f m t / 2+θ / 2+ΔT*f m ) Among them, a 1u is the amplitude of the RF signal, and ΔT is the time change of the signal after it is transmitted through a one-way optical fiber transmission link.

9. The method for automatic phase compensation of a microwave photon long-distance transmission link according to claim 8, characterized in that: The signal expression of the beat frequency output of the second photodetector is e0=a0cos(f m t+θ), where a0 is the amplitude of the signal output by the second photodetector.

10. A microwave photon long-distance transmission link phase automatic compensation device, characterized in that: The device applies the method described in any one of claims 1 to 9, and the device includes a laser, a cascade modulator, an optical coupler, a first optical filter, a second optical filter, an optical circulator, an optical reflection module, a first optical detector, an optical modulator, a third optical filter and a second optical detector. The laser is connected to the optical coupler via the cascade modulator, the cascade modulator receives a modulated signal, the optical coupler is respectively connected to the first optical filter and the second optical filter, the first optical filter is connected to the optical reflection module via the optical circulator and an optical fiber, the optical circulator is connected to the optical modulator via the first optical detector, the second optical filter is connected to the third optical filter via the optical modulator and another optical fiber, and the third optical filter is connected to the second optical detector.

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