Frequency scale transmission system

Abstract

The invention discloses a frequency scale transmission system, which belongs to the technical field of frequency scale transmission and comprises a central station and a terminal station which are connected through an optical fiber link. The terminal station performs sideband amplification injection locking according to the first optical signal with the frequency scale information transmitted by the central station to obtain a second optical signal with the frequency scale information, performs frequency shift on the second optical signal with the frequency scale information to obtain a frequency shift optical signal, and returns the frequency shift optical signal to the central station through an optical fiber link; the central station converts the frequency shift optical signal returned by the terminal station into a second electric signal, performs phase compensation on the original electric signal according to the second electric signal to obtain a compensation electric signal, performs sideband amplification injection locking according to the compensation electric signal to obtain a first optical signal with frequency scale information, and sends the first optical signal to the terminal station; and the first optical signal with the frequency scale information is transmitted to a terminal station through an optical fiber link. According to the system, the signal transmission performance and efficiency can be improved, the two-way transmission of light with quasi-same wavelength is realized, and the symmetrical reciprocity of the two-way transmission is improved.

Description

Technical Field

[0001] The invention relates to a frequency mark transmission system, belonging to the technical field of frequency mark transmission. Background Art

[0002] Fiber-based RF frequency standard transmission, also known as frequency standard transmission, refers to modulating the RF signal onto an optical carrier for transmission. Due to the influence of ambient temperature, fiber jitter, etc., the optical path changes when light is transmitted in the link, causing the phase of the transmitted light to fluctuate. By measuring the phase fluctuation of the round-trip light passing through the same section of optical fiber and performing phase compensation to offset the influence of link delay, the stable phase transmission of the RF signal can be achieved, thereby transmitting the optical frequency signal remotely with high fidelity.

[0003] Research on inter-site frequency synchronization technology based on optical fiber communication networks as physical carriers requires the transmission of high-precision frequency standards to each network node to ensure signal synchronization and accurate data transmission, which can provide core technical support for important applications such as positioning, navigation, and communication. For example, applying the frequency standard transmission system between multiple sites at very long distances can enable multiple sites to observe the same target point at the same frequency and phase, and the observation results are more accurate than those of a single site. The effect is equivalent to that of a very large-caliber antenna, but the maintenance cost is greatly reduced.

[0004] At present, most of the research on frequency standard transmission based on optical fiber focuses on the measurement and compensation of phase fluctuations, and there are few methods to improve transmission efficiency and ensure the symmetric reciprocity of bidirectional transmission in the long term. Especially in the process of combining optical and radio frequency, phase noise may be introduced, making the phase characteristics of the signal unstable and causing a decrease in signal quality. Summary of the invention

[0005] The object of the present invention is to provide a frequency standard transmission system, which can improve the transmission performance and efficiency of signals, realize bidirectional transmission of light with quasi-isochronous wavelengths, and improve the symmetric reciprocity of bidirectional transmission.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: The present invention provides a frequency standard transmission system, comprising a central station and a terminal station connected by an optical fiber link; the terminal station performs sideband amplification injection locking according to a first optical signal with frequency standard information transmitted by the central station, obtains a second optical signal with frequency standard information, performs frequency shifting on the second optical signal with frequency standard information, obtains a frequency-shifted optical signal, and returns the frequency-shifted optical signal to the central station through the optical fiber link; the central station converts the frequency-shifted optical signal returned by the terminal station into a second electrical signal, performs phase compensation on the original electrical signal according to the second electrical signal, obtains a compensated electrical signal, performs sideband amplification injection locking according to the compensated electrical signal, obtains a first optical signal with frequency standard information, and transmits the first optical signal with frequency standard information to the terminal station through the optical fiber link.

[0007] Furthermore, the terminal station includes: A first photodetector, used for converting a first optical signal carrying frequency mark information into a first electrical signal; A laser module, used for performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain a second optical signal with frequency mark information; A frequency shift module, used for performing frequency shift on the second optical signal with frequency mark information to obtain a frequency shifted optical signal; The central station includes: a second photodetector, used to convert the frequency-shifted optical signal into a second electrical signal; A measurement compensation module, used to compare the second electrical signal with the original electrical signal to obtain a phase difference between the second electrical signal and the original electrical signal; A compensation module, used to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal; The mutual injection laser module is used to perform sideband amplification injection locking according to the compensation electrical signal to obtain the first optical signal with frequency mark information.

[0008] Further, the mutual injection laser module includes a first laser and a second laser that are injected into each other, and the frequency of the compensation electrical signal is the frequency difference corresponding to the optical signal of the first laser and the optical signal of the second laser; Performing sideband amplification injection locking according to the compensation electrical signal to obtain a first optical signal with frequency mark information includes: Loading the compensation electrical signal onto the optical signal of the second laser and generating a sideband; Injecting the optical signal of the first laser into the second laser, so that the sideband of the optical signal of the second laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; Using the optical signals mutually injected into the laser modules as the first optical signal with frequency marker information; The laser module includes a third laser without an isolator, and the frequency difference between the optical signal of the third laser and the optical signal of the first laser is equal to the frequency difference between the optical signal of the first laser and the optical signal of the second laser; Performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain the second optical signal with frequency mark information includes: Loading the first electrical signal onto the optical signal of the third laser and generating a sideband; Injecting the first optical signal with frequency mark information into the third laser, so that the sideband of the optical signal of the third laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; The optical signal of the third laser is used as the second optical signal with frequency mark information.

[0009] Furthermore, the frequency shift module uses an acousto-optic modulator to frequency shift the second optical signal carrying the frequency mark information to obtain a frequency-shifted optical signal.

[0010] Furthermore, the compensation module uses a voltage-controlled oscillator to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal.

[0011] Furthermore, the compensation module is also used to feed back the compensated electrical signal to the compensation measurement module; the compensation measurement module is also used to detect the compensated electrical signal. If it is detected that the compensation of the compensated electrical signal is incorrect, the compensated electrical signal is returned to the compensation module for re-compensation until the compensation of the compensated electrical signal is correct.

[0012] Furthermore, the terminal station also includes: A first optical amplifier, used to amplify the first optical signal carrying the frequency mark information to obtain an amplified first optical signal carrying the frequency mark information; The splitter is used to transmit the amplified first optical signal with frequency mark information to the first photodetector and the laser module respectively.

[0013] Furthermore, the terminal station also includes a first circulator and a second circulator; the first port of the first circulator is connected to the first end of the optical fiber link, the second port of the first circulator is connected to the input end of the first optical amplifier, and the third port of the first circulator is connected to the output end of the frequency shift module; the first port of the second circulator is connected to the first output end of the splitter, the second port of the second circulator is connected to the optical fiber port of the laser module, and the third port of the second circulator is connected to the input end of the frequency shift module; wherein the second output end of the splitter is connected to the input end of the first photodetector, and the output end of the first photodetector is connected to the RF port of the laser module.

[0014] Furthermore, the central station also includes: A second optical amplifier, used to amplify the frequency-shifted optical signal to obtain an amplified frequency-shifted optical signal; an optical filter, configured to filter the amplified frequency-shifted optical signal, obtain the filtered frequency-shifted optical signal, and transmit the filtered frequency-shifted optical signal to a second photodetector; The electric filter is used to filter the second electric signal, obtain the filtered second electric signal, and transmit the filtered second electric signal to the measurement compensation module.

[0015] Furthermore, the central station also includes a third circulator; the first port of the third circulator is connected to the optical fiber port of the mutual injection laser module, the second port of the third circulator is connected to the second end of the optical fiber link, and the third port of the third circulator is connected to the input end of the second optical amplifier; wherein, the output end of the second optical amplifier is connected to the input end of the optical filter, the output end of the optical filter is connected to the input end of the second photodetector, the output end of the second photodetector is connected to the input end of the electric filter, the output end of the electric filter is connected to the first input end of the measurement compensation module, the second input end of the measurement compensation module is connected to the original electrical signal, the third input end of the measurement compensation module is connected to the first output end of the compensation module, the output end of the measurement compensation module is connected to the input end of the compensation module, and the second output end of the compensation module is connected to the RF port of the mutual injection laser module.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The frequency standard transmission system provided by the present invention is that the central station performs sideband amplification injection locking according to the compensation electrical signal, which can optimize the phase noise of the signal, realize single-sideband modulation at the same time, reduce the bandwidth occupied by the signal, reduce power consumption, and improve signal transmission efficiency; the terminal station performs sideband amplification injection locking according to the first optical signal with frequency standard information transmitted by the central station, which can realize bidirectional transmission of light of quasi-same wavelength on the optical fiber link, and improve the symmetric reciprocity of bidirectional transmission. By shifting the frequency of the second optical signal with frequency standard information through the frequency shifting module, the influence of Rayleigh scattering in the optical fiber link can be reduced. By performing phase compensation on the original electrical signal according to the phase difference through the compensation module, the terminal station can obtain a signal that is strictly synchronized with the frequency phase of the central station. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a frequency standard transmission system provided by an embodiment of the present invention; Figure 2 It is a detailed schematic diagram of the frequency standard transmission system structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0019] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0020] The present application embodiment provides a frequency standard transmission system, such as Figure 1As shown, it includes a central station and terminal stations connected by optical fiber links.

[0021] The terminal station performs sideband amplification injection locking on the first optical signal with frequency mark information transmitted by the central station, obtains the second optical signal with frequency mark information, frequency shifts the second optical signal with frequency mark information, obtains the frequency-shifted optical signal, and returns the frequency-shifted optical signal to the central station via the optical fiber link.

[0022] The central station converts the frequency-shifted optical signal returned by the terminal station into a second electrical signal, performs phase compensation on the original electrical signal according to the second electrical signal, obtains the compensated electrical signal, performs sideband amplification injection locking according to the compensated electrical signal, obtains the first optical signal with frequency mark information, and transmits the first optical signal with frequency mark information to the terminal station via an optical fiber link.

[0023] In the frequency standard transmission system provided in this embodiment, the central station performs sideband amplification injection locking based on the compensation electrical signal, which can optimize the phase noise of the signal and realize single-sideband modulation at the same time, reduce the bandwidth occupied by the signal, reduce power consumption, and improve signal transmission efficiency; the terminal station performs sideband amplification injection locking based on the first optical signal with frequency standard information transmitted by the central station, which can realize bidirectional transmission of light of quasi-isochronous wavelength on the optical fiber link, and improve the symmetric reciprocity of the bidirectional transmission.

[0024] It should be noted that sideband amplification injection locking occurs between two lasers. Laser 1 is modulated using an RF signal. When the modulated sideband of laser 1 enters the vicinity of the cavity mode of laser 2, it will be amplified by the Gaussian gain region centered on the cavity mode of laser 2. By appropriately reducing the interval between the sideband of laser 1 and the cavity mode of laser 2, the cavity mode of laser 2 will be locked to the sideband of laser 1. This is the sideband amplification injection locking effect. This effect can optimize the phase noise of the signal while achieving single sideband modulation, reducing the bandwidth occupied by the signal, reducing power consumption, and improving signal transmission efficiency.

[0025] In one possible embodiment, Figure 1 As shown, the terminal station specifically includes: A first photodetector, used for converting a first optical signal carrying frequency mark information into a first electrical signal; A laser module, used for performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain a second optical signal with frequency mark information; The frequency shift module is used to perform frequency shift on the second optical signal carrying the frequency mark information to obtain a frequency-shifted optical signal.

[0026] The central station specifically includes: a second photodetector, used to convert the frequency-shifted optical signal into a second electrical signal; A measurement compensation module, used to compare the second electrical signal with the original electrical signal to obtain a phase difference between the second electrical signal and the original electrical signal; A compensation module, used to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal; The mutual injection laser module is used to perform sideband amplification injection locking according to the compensation electrical signal to obtain the first optical signal with frequency mark information.

[0027] In this embodiment, Figure 2 As shown, the mutual injection laser module specifically includes a first laser L1 and a second laser L2 that are injected into each other to compensate for the frequency of the electrical signal. is the frequency corresponding to the optical signal of the first laser L1 The frequency corresponding to the optical signal of the second laser L2 The difference, that is .

[0028] In this embodiment, performing sideband amplification injection locking according to the compensation electrical signal to obtain the first optical signal with frequency mark information includes: Loading the compensation electrical signal onto the optical signal of the second laser and generating a sideband; Injecting the optical signal of the first laser into the second laser, so that the sideband of the optical signal of the second laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; The optical signal mutually injected into the laser module is used as the first optical signal with frequency mark information.

[0029] Specifically, Figure 2 As shown, the compensation electrical signal is loaded onto the optical signal of the second laser L2 and a sideband is generated. Then, the optical signal of the first laser L1 is injected into the second laser L2, so that the sideband of the optical signal of the second laser L2 is locked to the cavity membrane of the first laser L1, completing the sideband amplification injection locking, which can optimize the phase noise of the signal, realize single sideband amplification, reduce power consumption, and improve signal transmission efficiency. At this time, Figure 2 As shown in (a), corresponding to point a on the output optical path of the mutual injection laser module, the electrical signal corresponding to the first laser L1 can be expressed as , the electrical signal corresponding to the second laser L2 can be expressed as ,in, Indicates time, represents the amplitude of the electrical signal corresponding to the first laser L1, Indicates the amplitude of the electrical signal corresponding to the second laser L2.

[0030] The optical signal output by the mutual injection laser module is transmitted to the terminal station through the optical fiber link. When it reaches the terminal station, the electrical signal corresponding to the first laser L1 is , the electrical signal corresponding to the second laser L2 is .

[0031] In this embodiment, Figure 2 As shown, the laser module includes a third laser L3 without an isolator, and the frequency corresponding to the optical signal of the third laser L3 is The frequency corresponding to the optical signal of the first laser L1 The difference is equal to the frequency corresponding to the optical signal of the first laser L1 The frequency corresponding to the optical signal of the second laser L2 The difference, that is .

[0032] In this embodiment, performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain the second optical signal with frequency mark information includes: Loading the first electrical signal onto the optical signal of the third laser and generating a sideband; Injecting the first optical signal with frequency mark information into the third laser, so that the sideband of the optical signal of the third laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; The optical signal of the third laser is used as the second optical signal with frequency mark information.

[0033] Specifically, Figure 2 As shown, the first electrical signal is loaded onto the optical signal of the third laser L3 and a sideband is generated, and then the first optical signal with frequency mark information is injected into the third laser L3, so that the sideband of the optical signal of the third laser L3 is locked to the cavity membrane of the first laser L1, completing the sideband amplification injection locking, and enabling bidirectional transmission of quasi-same wavelength light on the optical fiber link, thereby improving the symmetric reciprocity of bidirectional transmission. At this time, Figure 2 As shown in (b), corresponding to point b on the output optical path of the laser module, the electrical signal corresponding to the third laser L3 can be expressed as ,in, Indicates the amplitude of the electrical signal corresponding to the third laser L3.

[0034] In a possible embodiment, the frequency shift module uses an acousto-optic modulator (AOM) to shift the frequency of the second optical signal carrying the frequency mark information to obtain a frequency-shifted optical signal.

[0035] Specifically, Figure 2 As shown, the AOM is used to shift the frequency of the second optical signal with frequency mark information, and the frequency shift amount is , which can weaken the influence of optical fiber Rayleigh scattering. Figure 2 As shown in (c), corresponding to point c on the output optical path of the AOM, the electrical signal corresponding to the first laser L1 can be expressed as , the electrical signal corresponding to the second laser L2 can be expressed as , the electrical signal corresponding to the third laser L3 can be expressed as . Figure 2 middle, , , express , , The corresponding value after frequency shifting, , , .

[0036] The optical signal output by the AOM is returned to the central station through the same optical fiber link as the backlight. When the first laser L1 reaches the central station, the electrical signal corresponding to the first laser L1 is , the electrical signal corresponding to the second laser L2 is , the electrical signal corresponding to the third laser L3 is .

[0037] In a possible embodiment, the compensation module uses a voltage controlled oscillator (VCO) to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal.

[0038] Specifically, Figure 2 As shown, the second electrical signal Input measurement compensation module and original electrical signal Compare and obtain the second electrical signal The original electrical signal Phase difference Since the total delay of the optical fiber link is , and obtain the one-way delay of the optical fiber link Then use VCO to adjust the phase difference The original electrical signal Perform phase compensation and adjust the original electrical signal The phase is reduced by a delay , obtain the compensation electrical signal, and load the compensation electrical signal onto the optical signal of the second laser L2, so that the terminal station can obtain a signal that is strictly synchronized with the frequency and phase of the central station.

[0039] In a possible embodiment, the compensation module is also used to feed back the compensation electrical signal to the compensation measurement module; the compensation measurement module is also used to detect the compensation electrical signal fed back by the compensation module. If it is detected that the compensation of the compensation electrical signal fed back by the compensation module is incorrect, the incorrectly compensated compensation electrical signal is returned to the compensation module for re-compensation until the compensation of the compensation electrical signal fed back by the compensation module is correct.

[0040] In one possible embodiment, Figure 2 As shown, the terminal station also includes: A first optical amplifier, used to amplify the first optical signal carrying the frequency mark information to obtain an amplified first optical signal carrying the frequency mark information; The splitter is used to transmit the amplified first optical signal with frequency mark information to the first photodetector and the laser module respectively.

[0041] In one possible embodiment, Figure 2 As shown, the terminal station also includes a first circulator C1 and a second circulator C2; the first port of the first circulator C1 is connected to the first end of the optical fiber link, the second port of the first circulator C1 is connected to the input end of the first optical amplifier, and the third port of the first circulator C1 is connected to the output end of the frequency shift module; the first port of the second circulator C2 is connected to the first output end of the splitter, the second port of the second circulator C2 is connected to the optical fiber port of the laser module, and the third port of the second circulator C2 is connected to the input end of the frequency shift module; wherein the second output end of the splitter is connected to the input end of the first photodetector, and the output end of the first photodetector is connected to the RF port of the laser module.

[0042] Specifically, Figure 2 As shown, the second port of the second circulator C2 is connected to the optical fiber port of the third laser L3, the third port of the second circulator C2 is connected to the input end of the AOM, and the output end of the AOM is connected to the third port of the first circulator C1. The first optical signal with frequency mark information output from the first output end of the splitter is input from the first port of the second circulator C2, output from the second port of the second circulator C2, and injected into the third laser L3 through the optical fiber port of the third laser L3. The first electrical signal output by the first photodetector is loaded onto the optical signal of the third laser L3 through the radio frequency port of the third laser L3. The third laser L3 performs sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal. The obtained second optical signal with frequency mark information is returned to the second circulator C2 through the optical fiber port of the third laser L3, input from the second port of the second circulator C2, and output from the third port of the second circulator C2 to the AOM. Figure 2In the figure, 1, 2, 3 of the first circulator C1 represent the first port, the second port, and the third port of the first circulator C1, and 1, 2, 3 of the second circulator C2 represent the first port, the second port, and the third port of the second circulator C2.

[0043] In one possible embodiment, Figure 2 As shown, the central station also includes: A second optical amplifier, used to amplify the frequency-shifted optical signal to obtain an amplified frequency-shifted optical signal; an optical filter, configured to filter the amplified frequency-shifted optical signal, obtain the filtered frequency-shifted optical signal, and transmit the filtered frequency-shifted optical signal to a second photodetector; The electric filter is used to filter the second electric signal, obtain the filtered second electric signal, and transmit the filtered second electric signal to the measurement compensation module.

[0044] Specifically, Figure 2 As shown, the frequency-shifted optical signal is amplified by the second optical amplifier. Due to the influence of Rayleigh scattering of light, the optical signal returned to the central station together with the original optical signal of the first laser L1 and the second laser L2. In order to reduce the redundant electrical signals generated after photoelectric conversion, an optical filter is used to filter out the optical signal returned to the central station by Rayleigh scattering of the second laser L2 in the light and the optical signal returned to the central station after frequency shifting at the terminal station. At this time, Figure 2 As shown in (d), corresponding to point d on the output optical path of the optical filter, the optical signal input to the second photodetector is the original optical signal of the first laser L1, the optical signal of the first laser L1 returned to the central station after frequency shifting at the terminal station, and the optical signal of the third laser L3 returned to the central station after frequency shifting at the terminal station. The original optical signal of the first laser L1 is , the optical signal of the first laser L1 returned to the central station after frequency shifting at the terminal station is , the optical signal of the third laser L3 returned to the central station after frequency shifting at the terminal station is After the original optical signal of the first laser L1, the optical signal of the first laser L1 returned to the central station after frequency shifting at the terminal station, and the optical signal of the third laser L3 returned to the central station after frequency shifting at the terminal station are converted into electrical signals by the second photoelectric detector, the electrical signal of the original optical signal of the first laser L1 converted by the second photoelectric detector is filtered out by an electrical filter, and the optical signal of the first laser L1 returned to the central station after frequency shifting at the terminal station and the optical signal of the third laser L3 returned to the central station after frequency shifting at the terminal station are obtained. The electrical signal is the second electrical signal that is ultimately required. At this time, if Figure 2 As shown in (e), corresponding to point e on the output circuit of the electric filter, the final required second electrical signal is .

[0045] In one possible embodiment, Figure 2 As shown, the central station also includes a third circulator C3; the first port of the third circulator C3 is connected to the optical fiber port of the mutual injection laser module, the second port of the third circulator C3 is connected to the second end of the optical fiber link, and the third port of the third circulator C3 is connected to the input end of the second optical amplifier; wherein, the output end of the second optical amplifier is connected to the input end of the optical filter, the output end of the optical filter is connected to the input end of the second photodetector, the output end of the second photodetector is connected to the input end of the electric filter, the output end of the electric filter is connected to the first input end of the measurement compensation module, the second input end of the measurement compensation module is connected to the original electrical signal, the third input end of the measurement compensation module is connected to the first output end of the compensation module, the output end of the measurement compensation module is connected to the input end of the compensation module, and the second output end of the compensation module is connected to the RF port of the mutual injection laser module.

[0046] Specifically, Figure 2 As shown, the first port of the third circulator C3 is connected to the optical fiber port of the second laser L2, the third input end of the measurement compensation module is connected to the first output end of the VCO, the output end of the measurement compensation module is connected to the input end of the VCO, and the second output end of the VCO is connected to the radio frequency port of the second laser L2. The compensation electrical signal output by the second output end of the VCO is loaded onto the optical signal of the second laser L2 via the radio frequency port of the second laser L2, and the second laser L2 performs sideband amplification injection locking according to the compensation electrical signal. The first optical signal with frequency mark information obtained is transmitted to the third circulator C3 via the optical fiber port of the second laser L2, input from the first port of the third circulator C3, transmitted from the second port of the third circulator C3 to the first circulator C1, and input from the first port of the first circulator C1; the frequency-shifted optical signal output by the AOM is input from the third port of the first circulator C1, returned from the first port of the first circulator C1 to the third circulator C3, input from the second port of the third circulator C3, and transmitted from the third port of the third circulator C3 to the second optical amplifier. Figure 2 In FIG. 1 , 1, 2, and 3 of the third circulator C3 represent the first port, the second port, and the third port of the third circulator C3 .

[0047] The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A frequency standard transmission system, characterized in that: It includes a central station and a terminal station connected by an optical fiber link; the terminal station performs sideband amplification injection locking according to a first optical signal with frequency mark information transmitted by the central station, obtains a second optical signal with frequency mark information, frequency-shifts the second optical signal with frequency mark information, obtains a frequency-shifted optical signal, and returns the frequency-shifted optical signal to the central station through the optical fiber link; the central station converts the frequency-shifted optical signal returned by the terminal station into a second electrical signal, performs phase compensation on the original electrical signal according to the second electrical signal, obtains a compensated electrical signal, performs sideband amplification injection locking according to the compensated electrical signal, obtains a first optical signal with frequency mark information, and transmits the first optical signal with frequency mark information to the terminal station through the optical fiber link.

2. The frequency standard transmission system according to claim 1, characterized in that: The terminal includes: A first photodetector, used for converting a first optical signal carrying frequency mark information into a first electrical signal; A laser module, used for performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain a second optical signal with frequency mark information; A frequency shift module, used for performing frequency shift on the second optical signal with frequency mark information to obtain a frequency shifted optical signal; The central station includes: a second photodetector, used to convert the frequency-shifted optical signal into a second electrical signal; A measurement compensation module, used to compare the second electrical signal with the original electrical signal to obtain a phase difference between the second electrical signal and the original electrical signal; A compensation module, used to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal; The mutual injection laser module is used to perform sideband amplification injection locking according to the compensation electrical signal to obtain the first optical signal with frequency mark information.

3. The frequency standard transmission system according to claim 2, characterized in that: The mutual injection laser module includes a first laser and a second laser that are injected into each other, and the frequency of the compensation electrical signal is the frequency difference corresponding to the optical signal of the first laser and the optical signal of the second laser; Performing sideband amplification injection locking according to the compensation electrical signal to obtain a first optical signal with frequency mark information includes: Loading the compensation electrical signal onto the optical signal of the second laser and generating a sideband; Injecting the optical signal of the first laser into the second laser, so that the sideband of the optical signal of the second laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; Using the optical signals mutually injected into the laser modules as the first optical signal with frequency marker information; The laser module includes a third laser without an isolator, and the frequency difference between the optical signal of the third laser and the optical signal of the first laser is equal to the frequency difference between the optical signal of the first laser and the optical signal of the second laser; Performing sideband amplification injection locking according to the first optical signal with frequency mark information and the first electrical signal to obtain the second optical signal with frequency mark information includes: Loading the first electrical signal onto the optical signal of the third laser and generating a sideband; Injecting the first optical signal with frequency mark information into the third laser, so that the sideband of the optical signal of the third laser locks the cavity membrane of the first laser, completing the sideband amplification injection locking; The optical signal of the third laser is used as the second optical signal with frequency mark information.

4. The frequency standard transmission system according to claim 2, characterized in that: The frequency shift module uses an acousto-optic modulator to shift the frequency of the second optical signal with frequency mark information to obtain a frequency-shifted optical signal.

5. The frequency standard transmission system according to claim 2, characterized in that: The compensation module uses a voltage-controlled oscillator to perform phase compensation on the original electrical signal according to the phase difference to obtain a compensated electrical signal.

6. The frequency standard transmission system according to claim 2, characterized in that: The compensation module is also used to feed back the compensation electrical signal to the compensation measurement module; the compensation measurement module is also used to detect the compensation electrical signal. If it is detected that the compensation of the compensation electrical signal is incorrect, the compensation electrical signal is returned to the compensation module for re-compensation until the compensation of the compensation electrical signal is correct.

7. The frequency standard transmission system according to claim 2, characterized in that: The terminal also includes: A first optical amplifier, used to amplify the first optical signal carrying the frequency mark information to obtain an amplified first optical signal carrying the frequency mark information; The splitter is used to transmit the amplified first optical signal with frequency mark information to the first photodetector and the laser module respectively.

8. The frequency standard transmission system according to claim 7, characterized in that: The terminal station also includes a first circulator and a second circulator; the first port of the first circulator is connected to the first end of the optical fiber link, the second port of the first circulator is connected to the input end of the first optical amplifier, and the third port of the first circulator is connected to the output end of the frequency shift module; the first port of the second circulator is connected to the first output end of the splitter, the second port of the second circulator is connected to the optical fiber port of the laser module, and the third port of the second circulator is connected to the input end of the frequency shift module; wherein the second output end of the splitter is connected to the input end of the first photodetector, and the output end of the first photodetector is connected to the radio frequency port of the laser module.

9. The frequency standard transmission system according to claim 2, characterized in that: The central station also includes: A second optical amplifier, used to amplify the frequency-shifted optical signal to obtain an amplified frequency-shifted optical signal; an optical filter, configured to filter the amplified frequency-shifted optical signal, obtain the filtered frequency-shifted optical signal, and transmit the filtered frequency-shifted optical signal to a second photodetector; The electric filter is used to filter the second electric signal, obtain the filtered second electric signal, and transmit the filtered second electric signal to the measurement compensation module.

10. The frequency standard transmission system according to claim 9, characterized in that: The central station also includes a third circulator; a first port of the third circulator is connected to the optical fiber port of the mutual injection laser module, a second port of the third circulator is connected to the second end of the optical fiber link, and a third port of the third circulator is connected to the input end of the second optical amplifier; wherein, the output end of the second optical amplifier is connected to the input end of the optical filter, the output end of the optical filter is connected to the input end of the second photodetector, the output end of the second photodetector is connected to the input end of the electric filter, the output end of the electric filter is connected to the first input end of the measurement compensation module, the second input end of the measurement compensation module is connected to the original electrical signal, the third input end of the measurement compensation module is connected to the first output end of the compensation module, the output end of the measurement compensation module is connected to the input end of the compensation module, and the second output end of the compensation module is connected to the radio frequency port of the mutual injection laser module.

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