Time-frequency signal optical fiber transmission distribution method and system

Abstract

The invention belongs to a time-frequency signal distribution method based on an optical fiber, and aims to solve the problems that long-distance multi-user distribution cannot be carried out and the precision and the safety are insufficient in the conventional common time-frequency signal distribution method. The invention provides a time-frequency signal optical fiber transmission distribution method and system, aiming at solving the technical problems that in the prior art, the cost is high when special optical fiber transmission equipment is adopted, and the increase of the number of users is limited, the invention provides the time-frequency signal optical fiber transmission distribution method and the system, a coded signal to be transmitted is simultaneously modulated into a first laser signal and a second laser signal with different wavelengths at a main end; the method comprises the following steps: respectively demodulating coded signals from a first wavelength division laser signal and a second wavelength division laser signal at a slave end, respectively recovering a time signal, a first frequency signal and a second frequency signal from the demodulated coded signals, then carrying out phase discrimination to obtain a phase difference, and subsequently compensating the transmission delay of the time signal. And a time signal accurately synchronized with the time-frequency reference source is obtained.

Description

Technical Field

[0001] The present application relates to a time-frequency signal distribution method, and specifically to a time-frequency signal optical fiber transmission distribution method and system. Background Art

[0002] The time unit "second" is one of the seven basic units in the International System of Units. It is the physical quantity with the highest measurement accuracy at present and is also a crucial parameter in various fields. With the rapid development of basic scientific research and deep space exploration and other applications, the distribution technology of high-precision time and frequency signals (hereinafter referred to as time and frequency signals) is becoming increasingly important. It has become an important basic condition for the coordinated work of cutting-edge basic scientific research, high-tech engineering applications and high-precision equipment. For example, in large radar stations or large time and frequency application centers, high-precision time and frequency synchronization of picoseconds is required between multiple sites or multiple users.

[0003] High-performance atomic clocks enable the generation and maintenance of precise time signals, but they are often expensive. In order to meet the needs of multiple users for high-precision time and frequency signals at the same time, multi-user time and frequency signal distribution technology is of great significance. At present, the commonly used time and frequency signal distribution methods include the use of coaxial cables for distribution, satellite two-way comparison or satellite common view for distribution, optical fiber-based White Rabbit technology (White Rabbit is an optical fiber-based precise time and data distribution protocol), and dedicated links for distribution, all of which have corresponding defects: (1) Using coaxial cable for time-frequency signal distribution: Due to the influence of transmission bandwidth and loss, it is only suitable for short-distance signal distribution within a hundred meters and cannot meet the needs of long-distance and high-precision distribution.

[0004] (2) Using satellite two-way comparison or satellite common view to allocate time and frequency signals: Due to interference from factors such as ionosphere and troposphere fluctuations, the accuracy is generally in the nanosecond range, which makes it difficult to meet the needs of multiple users for high-precision signals at the same time. In addition, there are problems such as insufficient security and expensive equipment.

[0005] (3) Optical fiber-based White Rabbit technology: Although it does not require a dedicated transmission channel, it has problems such as link asymmetry. The transmission accuracy cannot exceed the sub-nanosecond level, and it cannot transmit frequency signals.

[0006] (4) Use a dedicated link for time-frequency signal distribution: picosecond stability time transfer can be achieved during transmission, or E -17 Frequency transmission of this magnitude is currently commonly used for long-distance optical fiber time transmission. However, due to the limitations of time division multiple access or wavelength division multiple access technology, the increase in the number of users is restricted. At the same time, the optical fiber transmission equipment required is complex in structure and expensive, so it is difficult to meet the needs of multiple users for time and frequency signals at the same time. Summary of the invention

[0007] The present application aims to provide a method and system for optical fiber transmission and distribution of time-frequency signals in order to solve the technical problems that the currently commonly used time-frequency signal distribution methods are unable to carry out long-distance multi-user distribution, lack accuracy and security, use of dedicated optical fiber transmission equipment is expensive, and the increase in the number of users is restricted.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for optical fiber transmission and distribution of time-frequency signals, wherein the time-frequency signals are transmitted from a master end to a slave end via an optical fiber; the method comprises: The coded signal to be transmitted is modulated into a first laser signal with a wavelength of λ1 and a second laser signal with a wavelength of λ2 at the same time; wherein λ1≠λ2; the coded signal to be transmitted is obtained by encoding the time signal to be transmitted and the frequency signal to be transmitted from a time-frequency reference source, and the frequency signal to be transmitted is subjected to frequency multiplication processing before being encoded; The first laser signal and the second laser signal are wavelength-divided and combined, and then amplified to be divided into multiple laser signals, which are respectively transmitted to multiple slave ends through different optical fiber links; For either slave: The received laser signal is wavelength-divided and output to obtain a first wavelength-divided laser signal with a wavelength of λ1 and a second wavelength-divided laser signal with a wavelength of λ2; Demodulating the coded signals from the first wavelength division laser signal and the second wavelength division laser signal respectively and decoding them to obtain a first demodulated coded signal and a second demodulated coded signal respectively; Recovering time information, a first frequency signal, and a second frequency signal from the first demodulated coded signal and the second demodulated coded signal respectively, and then performing phase discrimination on the first frequency signal and the second frequency signal to obtain a phase difference; According to the phase difference and the second frequency signal, the optical fiber link noise is compensated to obtain a compensation frequency signal, so that the frequency of the compensation frequency signal is equal to the frequency of the main end to be transmitted after frequency doubling processing; Divide the compensation frequency signal to a frequency equal to the frequency signal to be transmitted at the main end, and then distribute it to multiple outputs with the same performance; Delay the first frequency signal according to the time information N cycles, and obtain a time signal roughly synchronized with the time signal to be transmitted; The coarse synchronization time signal is adjusted according to the phase shift value After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained; wherein, the transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part obtained is N , the remainder is The transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal; The time signal synchronized with the time signal to be transmitted is distributed as multiple outputs with the same performance.

[0009] Furthermore, the method for calculating the transmission time of the laser signal in the optical fiber link between any slave end and the master end includes:

[0010] in, It represents the transmission time of the laser signal in the optical fiber link between any slave end and the master end. Indicates the length of the optical fiber link between any slave end and the master end, determined by the phase difference, represents the refractive index of the first laser signal in the optical fiber link, Represents the speed of light in a vacuum.

[0011] Furthermore, the length of the optical fiber link between any slave end and the master end is The calculation methods include:

[0012] in, represents the phase difference, represents the dispersion coefficient of the optical fiber, Indicates the laser wavelength difference between the first laser signal and the second laser signal.

[0013] Furthermore, the method for acquiring the coded signal to be transmitted includes: The frequency emitted by the time-frequency reference source is f 0 frequency signal to be transmitted m times, the frequency is mf 0 frequency signal; Frequency mf The frequency signal of 0 is used as the carrier signal, and the time signal to be transmitted and the corresponding time code information are encoded on the frequency mf 0, and obtain the coded signal to be transmitted.

[0014] In a second aspect, the present application proposes a time-frequency signal optical fiber transmission and distribution system, including a master end and a slave end; The master end comprises: The first laser and the second laser are used to simultaneously modulate the coded signal to be transmitted into a first laser signal with a wavelength of λ1 and a second laser signal with a wavelength of λ2; wherein λ1≠λ2; the coded signal to be transmitted is obtained by encoding the time signal to be transmitted and the frequency signal to be transmitted from a time-frequency reference source, and the frequency signal to be transmitted is subjected to frequency multiplication processing before being encoded; A first wavelength division multiplexer, used for wavelength division and combining the first laser signal and the second laser signal; Optical amplifier, used to amplify the laser signal after wavelength division and beam combination; An optical splitter is used to split the amplified laser signal into multiple laser signals, which are respectively transmitted to multiple slave ends through different optical fiber links; The slave end comprises: A second wavelength division multiplexer is used to perform wavelength division output on the received laser signal to obtain a first wavelength division laser signal with a wavelength of λ1 and a second wavelength division laser signal with a wavelength of λ2; The first photodetector and the second photodetector are used to demodulate the coded signal from the first wavelength division laser signal and the second wavelength division laser signal respectively; The first decoder and the second decoder are used to decode the demodulated coded signal to obtain a first demodulated coded signal and a second demodulated coded signal respectively; The first carrier recovery module and the second carrier recovery module are used to recover the time information, the first frequency signal and the second frequency signal from the first demodulated coded signal and the second demodulated coded signal respectively; the phase detector is used to perform phase detection on the first frequency signal and the second frequency signal to obtain a phase difference; The frequency servo purification module is used to compensate the optical fiber link noise according to the phase difference and the second frequency signal to obtain a compensation frequency signal, so that the frequency of the compensation frequency signal is equal to the frequency of the main end to be transmitted after frequency doubling processing; A frequency distributor is used to divide the compensation frequency signal into a frequency equal to the frequency of the frequency signal to be transmitted at the main end, and then distribute it into multiple outputs with the same performance; A time regeneration module is used to delay the first frequency signal according to the time information N cycles, and obtain a time signal roughly synchronized with the time signal to be transmitted; Phase compensation module, used to compensate the coarse synchronization time signal according to the phase shift value After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained; wherein, the transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part obtained is N , the remainder is The transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal; The time distributor is used to distribute the time signal synchronized with the time signal to be transmitted into multiple outputs with the same performance.

[0015] Furthermore, the method for calculating the transmission time of the laser signal in the optical fiber link between any slave end and the master end includes:

[0016]

[0017] in, It represents the transmission time of the laser signal in the optical fiber link between any slave end and the master end. Indicates the length of the optical fiber link between any slave end and the master end. represents the refractive index of the first laser signal in the optical fiber link, represents the speed of light in vacuum, represents the phase difference, represents the dispersion coefficient of the optical fiber, Indicates the laser wavelength difference between the first laser signal and the second laser signal.

[0018] Furthermore, in the frequency servo purification module, compensating for the optical fiber link noise to obtain a compensated frequency signal includes: The frequency servo purification module serves the VCOCXO inside the frequency servo purification module according to the phase difference and the second frequency signal, so that the VCOCXO outputs a compensation frequency signal.

[0019] Furthermore, the master end also includes a frequency multiplier and an encoder; The frequency multiplier is used to multiply the frequency emitted by the time-frequency reference source by 1 before encoding the frequency signal to be transmitted. f 0 frequency signal to be transmitted m times, the frequency is mf 0 frequency signal; The encoder is used to mf The frequency signal of 0 is used as the carrier signal, and the time signal to be transmitted and the corresponding time code information are encoded on the frequency mf 0, and obtain the coded signal to be transmitted.

[0020] Furthermore, it also includes a time code source; the time code source is used to output time code information.

[0021] Furthermore, when slave ends are added, a new optical amplifier and a new optical splitter are sequentially added between the optical splitter and any original slave end, and the new optical splitter is respectively connected to each of the added slave ends.

[0022] Compared with the prior art, this application has the following beneficial effects: The present application proposes a method for optical fiber transmission and distribution of time-frequency signals, wherein a coded signal to be transmitted is modulated into a first laser signal and a second laser signal of two different wavelengths at a master end, and a coded signal is demodulated from the first wavelength-divided laser signal and the second wavelength-divided laser signal at a slave end, and after decoding, time information, a first frequency signal, and a second frequency signal are recovered from the first demodulated coded signal and the second demodulated coded signal, respectively, and then the first frequency signal and the second frequency signal are phase-detected to obtain a phase difference, and the first frequency signal is subsequently delayed according to the time information. N cycles, and obtain a time signal roughly synchronized with the time-frequency reference source, and then the roughly synchronized time signal is adjusted according to the phase shift value After phase shifting, a time signal synchronized with the time-frequency reference source with high precision is obtained. The transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part is obtained. N , the remainder is , the transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal. The present application accurately calculates the transmission delay of the time-frequency signal in the optical fiber link based on the phase difference, and compensates for the transmission delay in real time, so that the output time of the slave end is accurately synchronized with the reference time of the master end. In addition, the present application performs phase discrimination in the slave end, which can effectively improve the transmission delay of the optical fiber link, thereby improving the accuracy of signal transmission and distribution, and can solve the existing problem of multiple users' simultaneous demand for high-precision time-frequency signals.

[0023] The present application also proposes a time-frequency signal optical fiber transmission and distribution system, which has all the advantages of the above-mentioned time-frequency signal optical fiber transmission and distribution method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A schematic diagram of a flow chart of the optical fiber transmission allocation method of time-frequency signals of the present application; Figure 2 A schematic diagram of a master end in the optical fiber transmission and distribution system for time-frequency signals of the present application; Figure 3 A schematic diagram of a slave end in the optical fiber transmission and distribution system for time-frequency signals of the present application; Figure 4 A schematic diagram of adding a slave end to the optical fiber transmission and distribution system for time-frequency signals of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0029] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invented product is usually placed when used. It is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0031] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] At present, the commonly used time-frequency signal distribution methods include distribution using coaxial cables, distribution using satellite two-way comparison or satellite common view, distribution based on optical fiber White Rabbit technology, and distribution using dedicated links. Specifically: (1) Use coaxial cable for time-frequency signal distribution: Coaxial cable can effectively prevent external electromagnetic interference and reduce signal attenuation, but its limitations are also obvious when using coaxial cable for time-frequency signal distribution. Since the transmission loss of coaxial cable increases with the increase of distance, especially when high-frequency signals are transmitted, the attenuation is more significant. Therefore, this method is usually only suitable for short-distance signal distribution within 100 meters. In addition, the transmission bandwidth of coaxial cable is limited, which limits the type and rate of signals it can transmit. For high-precision, high-frequency time-frequency signals, coaxial cable may not be able to meet its bandwidth requirements. Furthermore, although coaxial cable has a certain anti-interference ability, its anti-interference performance may not be sufficient to ensure stable signal transmission in complex electromagnetic environments, such as large industrial facilities or urban centers.

[0033] (2) Using satellite two-way comparison or satellite common view for time-frequency signal allocation: Satellite two-way comparison and satellite common view are advanced technologies for using satellites for time and frequency synchronization. However, they also face some inherent challenges. When satellite signals pass through the Earth's atmosphere, they are affected by the ionosphere and troposphere, resulting in signal delays and phase changes. These changes are difficult to accurately predict and compensate for, which will affect the accuracy of time and frequency synchronization. In addition, due to the above-mentioned interference and the limitations of the satellite system itself, the accuracy of time and frequency synchronization using satellites can usually only reach the nanosecond level, which is not enough for some high-precision applications that require sub-nanosecond or even picosecond accuracy. Furthermore, the construction and maintenance costs of satellite communication systems are high, and there is a risk of malicious attacks or interference. In addition, the limited satellite resources also limit its application in large-scale time and frequency synchronization networks.

[0034] (3) Optical fiber-based White Rabbit technology: White Rabbit is an optical fiber-based precision time and data distribution protocol that uses the low loss and high bandwidth characteristics of optical fiber to achieve high-precision time synchronization and data transmission. However, in the White Rabbit network, due to the asymmetry of the optical fiber link (such as differences in length, attenuation, etc.), time synchronization errors may occur, which are particularly significant in long-distance transmission or complex network topologies. Although White Rabbit technology has sub-nanosecond time synchronization accuracy, it is difficult to further improve its transmission accuracy due to factors such as optical fiber link quality and equipment performance. Furthermore, White Rabbit technology is mainly designed for time synchronization and data transmission, and has limited support for the transmission of frequency signals, which limits its use in application scenarios that require the simultaneous transmission of time and frequency signals.

[0035] (4) Use dedicated links for time-frequency signal distribution; dedicated links usually refer to high-performance, high-stability transmission links designed for specific applications, such as dedicated optical fiber links or microwave links. This method has significant advantages in long-distance time and frequency synchronization. However, due to the limitations of time division multiple access or wavelength division multiple access technology, the number of users that dedicated links can support is limited. As user demand increases, it may be necessary to build more links or adopt more complex multiplexing technologies to meet demand. In addition, the construction and maintenance of dedicated links require high-performance equipment and technical support, such as high-precision time and frequency sources, stable optical fiber transmission equipment, and complex multiplexing and demultiplexing equipment. These devices are expensive and require professional technicians to maintain and operate. Furthermore, dedicated links are usually designed for specific applications, and their flexibility and scalability are limited. Once a link is built and put into use, it is difficult to modify or expand it on a large scale, which also limits its use in application scenarios that change rapidly or require high flexibility.

[0036] Based on the above situation, the present application proposes a method and system for optical fiber transmission distribution of time-frequency signals, which will be described in detail below in conjunction with embodiments and drawings.

[0037] like Figure 1 As shown, it is a flow chart of the optical fiber transmission distribution method of the time-frequency signal of the present application, and the time-frequency signal is transmitted from the master end to the slave end through the optical fiber. It may include: S101, modulate the coded signal to be transmitted into a first laser signal of wavelength λ1 and a second laser signal of wavelength λ2 simultaneously; wherein λ1≠λ2; the coded signal to be transmitted is obtained by encoding the time signal to be transmitted and the frequency signal to be transmitted which are derived from a time-frequency reference source, and the frequency signal to be transmitted is frequency-multiplied before being encoded.

[0038] In practical applications, laser modulation technology can be used to simultaneously modulate the coded signal to be transmitted onto two lasers of different wavelengths (λ1 and λ2) to convert the electrical signal into an optical signal. The selection of λ1 and λ2 can take into account the loss and dispersion of optical fiber transmission and the requirements of wavelength division multiplexing technology, as long as there is enough spacing to avoid cross interference.

[0039] S102, performing wavelength division and beam combination on the first laser signal and the second laser signal, and then amplifying the first laser signal and dividing the signal into multiple laser signal beams, which are respectively transmitted to multiple slave ends through different optical fiber links.

[0040] For either slave: S103 , performing wavelength division output on the received laser signal to obtain a first wavelength division laser signal with a wavelength λ1 and a second wavelength division laser signal with a wavelength λ2 .

[0041] In practical applications, a wavelength division multiplexer can be used to separate the received composite optical signal into two wavelength division signals with different wavelengths (wavelengths are λ1 and λ2).

[0042] S104, demodulating and decoding the coded signals from the first wavelength division laser signal and the second wavelength division laser signal respectively, and obtaining a first demodulated coded signal and a second demodulated coded signal accordingly.

[0043] The original coded signal can be demodulated from each wavelength-division laser signal using a technique that reverses the modulation process.

[0044] S105, recovering the time information, the first frequency signal and the second frequency signal from the first demodulated coded signal and the second demodulated coded signal respectively, and then performing phase detection on the first frequency signal and the second frequency signal to obtain a phase difference.

[0045] In practical applications, two frequency signals are subjected to phase detection to obtain the phase difference between them. This phase difference contains the delay and jitter information that may be introduced during the transmission process.

[0046] S106, compensating for the optical fiber link noise according to the phase difference and the second frequency signal to obtain a compensation frequency signal, so that the frequency of the compensation frequency signal is equal to the frequency of the main end transmission frequency signal after frequency doubling processing.

[0047] According to the phase difference obtained by phase detection and the information of the second frequency signal, a compensation frequency signal having the same frequency as the frequency signal to be transmitted at the master end after frequency multiplication can be generated through frequency adjustment technology.

[0048] S107, dividing the compensation frequency signal to a frequency equal to the frequency of the frequency signal to be transmitted at the master end, and then distributing it into multiple channels with the same performance for output.

[0049] In practical applications, if the frequency of the compensation frequency signal is higher than the frequency of the frequency signal to be transmitted at the main end, it is necessary to perform frequency division processing to reduce it to the frequency of the frequency signal to be transmitted at the main end, which can be achieved through a frequency divider. Then, the divided frequency signal is distributed as multiple outputs, and the performance of each output (such as frequency stability, phase consistency, etc.) should be the same or similar.

[0050] S108, delaying the first frequency signal according to the time information N cycles to obtain a time signal roughly synchronized with the time signal to be transmitted.

[0051] S109: the coarse synchronization time signal is adjusted according to the phase shift value After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained; wherein, the transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part obtained isN , the remainder is The transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal.

[0052] It should be noted that the phase shift value It reflects the slight delay introduced in the transmission process. Through phase shifting processing, the influence of transmission delay on the time signal can be further reduced or eliminated.

[0053] S110, allocating the time signal synchronized with the time signal to be transmitted into multiple channels with the same performance and then outputting them.

[0054] The time signal synchronized with the time signal to be transmitted is divided into multiple outputs so that the performance of each output (such as time stability, phase consistency, etc.) is the same, thereby ensuring that the output time signals have the same accuracy and stability.

[0055] This application can accurately measure and compensate for the phase difference and delay introduced in the transmission process by simultaneously modulating two laser signals of different wavelengths (wavelengths are λ1 and λ2) and performing phase detection processing, which can significantly improve the accuracy and stability of time-frequency signal transmission. In addition, the two wavelength signals are combined and transmitted using wavelength division multiplexing technology, and wavelength division multiplexing and multi-channel distribution are performed at the slave end, which can significantly improve the transmission efficiency and capacity of the optical fiber link, while meeting the needs of multiple slave ends for time-frequency signals. The slave end decodes, delays, phase shifts, and compensates the received time-frequency signal, which can maintain a high degree of consistency and stability with the master end signal, helping to ensure the long-term stable operation of the entire system. Furthermore, compared with traditional coaxial cable or satellite communication methods, optical fiber transmission has the advantages of lower loss, larger bandwidth, and longer transmission distance, which helps to reduce the cost of system construction and maintenance.

[0056] Used to implement the above-mentioned time-frequency signal optical fiber transmission distribution method, such as Figure 2 As shown, it is a schematic diagram of the master end of the optical fiber transmission and distribution system of the time-frequency signal of the present application, such as Figure 3 As shown, it is a schematic diagram of a slave end in the optical fiber transmission and distribution system of the time-frequency signal of the present application, which specifically includes: 1. Time and frequency reference source and master end.

[0057] The time-frequency reference source outputs the time signal and frequency to be transmitted as f 0 to be transmitted, and the time code source sends out time code information.

[0058] 2. Master end.

[0059] Frequency multiplier: multiplies the frequency signal to be transmitted m times the frequency mf0. The frequency multiplier can increase the frequency of the signal to be transmitted, increase the bandwidth, and improve the transmission rate.

[0060] Encoder: frequency mf The frequency signal of 0 is used as the carrier signal, and the time signal to be transmitted and the time code information sent by the time code source are encoded on the frequency signal to be transmitted to obtain the encoded signal to be transmitted. Through the encoder, an encoded signal containing time information, time code information and frequency information can be obtained. The first laser and the second laser: the coded signal to be transmitted is modulated on the first laser and the second laser simultaneously, wherein the wavelength of the first laser signal sent by the first laser is λ1, the wavelength of the second laser signal sent by the second laser is λ2, and it is ensured that λ1≠λ2.

[0061] Wavelength division multiplexer: The first laser signal and the second laser signal are wavelength-divided and combined by the wavelength division multiplexer. Through wavelength division multiplexing technology, multiple signals can be transmitted in parallel in the same optical fiber link, improving transmission efficiency and capacity.

[0062] Optical amplifier: used to amplify the laser signal after wavelength division and beam combining. It can significantly increase the transmission distance and coverage of the signal.

[0063] Optical splitter: used to split the amplified laser signal into multiple laser beams, which are transmitted to multiple slave ends through different optical fiber links. The optical splitter can realize signal distribution and transmission, and supports multiple slave ends to receive signals simultaneously.

[0064] 3. Slave end (in this embodiment, the slave end is provided with n indivual).

[0065] In the present application, multiple slave ends can be set at the same time, and the structures of the slave ends are the same. For any slave end, specifically including: The second wavelength division multiplexer: receives the laser signal sent by the master end and performs wavelength division output to obtain the first wavelength division laser signal with wavelength λ1 and the second wavelength division laser signal with wavelength λ2. The first wavelength division laser signal with wavelength λ1 is sent to the first photodetector, and the second wavelength division laser signal with wavelength λ2 is sent to the second photodetector. The second wavelength division multiplexer separates the laser signal received from the master end at the slave end and sends them to the corresponding photodetectors respectively.

[0066] The first photodetector and the second photodetector are used to demodulate the coded signal from the first wavelength division laser signal and the second wavelength division laser signal respectively. The photodetector can convert the optical signal into an electrical signal, absorb the optical energy and convert it into an electric current signal.

[0067] The first decoder and the second decoder: respectively decode the demodulated coded signal to obtain the first demodulated coded signal and the second demodulated coded signal respectively, and send them to the first carrier recovery module and the second carrier recovery module respectively.

[0068] The first carrier recovery module and the second carrier recovery module are used to recover the time information, the first frequency signal and the second frequency signal from the first demodulated coded signal and the second demodulated coded signal, respectively. In practical applications, a series of digital signal processing algorithms, such as a phase-locked loop, can be used to recover the time information, the first frequency signal and the second frequency signal.

[0069] Phase detector: performs phase detection on the first frequency signal and the second frequency signal to obtain the phase difference r The phase detector compares the phase difference between the first frequency signal and the second frequency signal, which serves as an important basis for subsequent frequency servo and phase compensation.

[0070] Frequency servo purification module: the second frequency signal and phase difference r The input is sent to the frequency servo purification module, which servos the internal VCOCXO (Voltage Controlled-Oven Controlled Crystal Oscillator) to make the VCOCXO stably output a compensation frequency signal equal to the frequency of the main end to be transmitted. The frequency servo purification module is a closed-loop control system that uses the phase difference output by the phase detector to r To adjust the output frequency of the internal VCOCXO, VCOCXO is an oscillator that can change the output frequency according to the control voltage. The goal of the frequency servo purification module is to make the output frequency of VCOCXO equal to the frequency of the frequency signal to be transmitted at the master end, thereby achieving frequency synchronization.

[0071] Frequency divider: divides the compensation frequency signal to a frequency equal to the frequency of the main end to be transmitted, that is, the frequency is f 0, and then redistribute them into multiple outputs with the same performance.

[0072] In order to perform subsequent phase shift and delay compensation, the following calculations are performed first: The length of the optical fiber link between any slave and the master for:

[0073] in, represents the dispersion coefficient of the optical fiber, represents the laser wavelength difference between the first laser signal and the second laser signal, =| λ1 - λ2 | .

[0074] Time regeneration module: delays the first frequency signal according to the time information N cycles to obtain a time signal roughly synchronized with the time signal to be transmitted.

[0075] Phase compensation module: The coarse synchronization time signal is adjusted according to the phase shift value. After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained, completing the compensation of the optical fiber link delay. The transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part is N , the remainder is , can be combined with and The formula is calculated as follows: The transmission time of the laser signal in the optical fiber link between any slave and the master for:

[0076] in, represents the refractive index of the first laser signal in the optical fiber link, Represents the speed of light in a vacuum.

[0077] Time distributor: distributes the time signal synchronized with the time signal to be transmitted into multiple outputs with the same performance.

[0078] In other embodiments of the present application, Figure 4 The following is a schematic diagram of adding a slave end. n Increase to n +2, you only need to add optical amplifiers and splitters in the optical fiber link, without adding or changing other original equipment at the main end, to expand the number of users.

[0079] The system of the present application utilizes a first laser and a second laser to simultaneously modulate the coded signal to be transmitted into two laser signals of different wavelengths, thereby realizing multi-wavelength parallel transmission and greatly improving transmission efficiency and capacity. By combining and separating the laser signals through the first wavelength division multiplexer, signals of multiple wavelengths can be transmitted in the same optical fiber, further improving the utilization rate and transmission capacity of the optical fiber. The frequency servo purification module effectively improves the frequency stability and synchronization accuracy. The time regeneration module and the phase compensation module jointly ensure the time synchronization accuracy between the slave end and the master end. The master end uses a splitter to enable the system to be easily expanded to multiple slave ends to meet the needs of large-scale distributed applications. The frequency distributor and the time distributor enable the system to provide stable and accurate frequency signals and time signals to multiple slave ends at the same time. The entire system can also quickly and easily expand the number of users by connecting optical amplifiers and splitters in the optical fiber link.

[0080] The following is a specific example of applying the optical fiber transmission allocation method of the time-frequency signal of the present application: (1) The time-frequency reference source outputs the time signal and frequency to be transmitted: f 0 = 10MHz frequency signal to be transmitted, the frequency of the frequency signal to be transmitted f 0 times 10 times to 10 f 0 = 100MHz.

[0081] (2) Using a 100 MHz frequency signal as a carrier signal, the time signal and time code information to be transmitted are encoded on the frequency signal to be transmitted to form a coded signal to be transmitted.

[0082] (3) The coded signal to be transmitted is modulated on the first laser and the second laser simultaneously, wherein the wavelength of the first laser signal sent by the first laser is λ1=1310, and the wavelength of the second laser signal sent by the second laser is λ2=1550.

[0083] (4) The first laser signal and the second laser signal are wavelength-divided and combined by the first wavelength division multiplexer, and the power is amplified by the optical amplifier. Then, the optical splitter is used to divide the first laser signal into multiple laser signals, which are then transmitted to the slave end through different optical fiber links.

[0084] (5) In slave end 1, the laser signal sent by the master end is received through the second wavelength division multiplexer, and the signal is wavelength-divided and output to obtain a first wavelength-divided laser signal with wavelength λ1 and a second wavelength-divided laser signal with wavelength λ2. l The first wavelength laser signal of 1 is sent to the first photodetector, and the l The second wavelength division laser signal of 2 is sent to the second photodetector.

[0085] (6) The first photodetector and the second photodetector respectively demodulate the coded signals from the first wavelength division laser signal and the second wavelength division laser signal, and after decoding, send the coded signals to the first carrier recovery module and the second carrier recovery module respectively.

[0086] (7) The first carrier recovery module and the second carrier recovery module respectively recover the time information, the first frequency signal and the second frequency signal from the demodulated coded signal, and then perform phase detection on the recovered first frequency signal and the second frequency signal through a phase detector to obtain a phase difference .

[0087] (8) The phase difference The second frequency signal is input to the frequency servo purification module, which serves the internal VCOCXO to make VCOCXO stably output the compensation frequency signal. The frequency of the compensation frequency signal is equal to the frequency of the main end to be transmitted after multiplication processing, which is equal to 100MHz.

[0088] (9) Length of the optical fiber link between slave 1 and the master for:

[0089] Among them, D=17ps / (nm*km) is the dispersion coefficient of the optical fiber. =| λ1 - λ2 |= 240nm is the wavelength difference between the first laser and the second laser. Assume that the phase detector value is = 4ns, then the fiber link length l 1=0.98km.

[0090] The transmission time of the laser signal in the optical fiber link between any slave and the master for

[0091] in, n =1.48, c =299792458m / s, N for Divide by the integer part of the period T0=10ns of the 100MHz frequency signal, The remainder is not divided. By calculation, we can get = 4839.949ns.

[0092] The time regeneration module delays the first frequency signal N=483 cycles, the time signal roughly synchronized with the time-frequency reference source is output. The phase compensation module performs phase shifting on the time signal roughly synchronized with the time-frequency reference source output by the time regeneration module. The phase shift value is =9.949ns, thereby completing the compensation for the optical fiber link delay, and the time distributor distributes the time signal synchronized with the time signal to be transmitted into multiple outputs with the same performance.

[0093] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for distributing time-frequency signals by optical fiber transmission, wherein the time-frequency signals are transmitted from a master end to a slave end via an optical fiber; characterized in that: include: The coded signal to be transmitted is modulated into a first laser signal with a wavelength of λ1 and a second laser signal with a wavelength of λ2 at the same time; wherein λ1≠λ2; the coded signal to be transmitted is obtained by encoding the time signal to be transmitted and the frequency signal to be transmitted from a time-frequency reference source, and the frequency signal to be transmitted is subjected to frequency multiplication processing before being encoded; The first laser signal and the second laser signal are wavelength-divided and combined, and then amplified to be divided into multiple laser signals, which are respectively transmitted to multiple slave ends through different optical fiber links; For either slave: The received laser signal is wavelength-divided and output to obtain a first wavelength-divided laser signal with a wavelength of λ1 and a second wavelength-divided laser signal with a wavelength of λ2; Demodulating the coded signals from the first wavelength division laser signal and the second wavelength division laser signal respectively and decoding them to obtain a first demodulated coded signal and a second demodulated coded signal respectively; Recovering time information, a first frequency signal, and a second frequency signal from the first demodulated coded signal and the second demodulated coded signal respectively, and then performing phase discrimination on the first frequency signal and the second frequency signal to obtain a phase difference; According to the phase difference and the second frequency signal, the optical fiber link noise is compensated to obtain a compensation frequency signal, so that the frequency of the compensation frequency signal is equal to the frequency of the main end to be transmitted after frequency doubling processing; Divide the compensation frequency signal to a frequency equal to the frequency signal to be transmitted at the main end, and then distribute it to multiple outputs with the same performance; Delay the first frequency signal according to the time information N cycles, and obtain a time signal roughly synchronized with the time signal to be transmitted; The coarse synchronization time signal is adjusted according to the phase shift value After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained; wherein, the transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part obtained is N , the remainder is The transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal; The time signal synchronized with the time signal to be transmitted is distributed as multiple outputs with the same performance.

2. The method for optical fiber transmission and distribution of time-frequency signals according to claim 1, characterized in that: The method for calculating the transmission time of the laser signal in the optical fiber link between any slave end and the master end comprises: in, It represents the transmission time of the laser signal in the optical fiber link between any slave end and the master end. Indicates the length of the optical fiber link between any slave end and the master end, determined by the phase difference, represents the refractive index of the first laser signal in the optical fiber link, Represents the speed of light in a vacuum.

3. The method for optical fiber transmission and distribution of time-frequency signals according to claim 2, characterized in that: The length of the optical fiber link between any slave and the master The calculation methods include: in, represents the phase difference, represents the dispersion coefficient of the optical fiber, Represents the laser wavelength difference between the first laser signal and the second laser signal.

4. The method for optical fiber transmission and distribution of time-frequency signals according to claim 1, characterized in that: The method for acquiring the coded signal to be transmitted comprises: The frequency emitted by the time-frequency reference source is f 0 frequency signal to be transmitted m times, the frequency is mf 0 frequency signal; Frequency mf The frequency signal of 0 is used as the carrier signal, and the time signal to be transmitted and the corresponding time code information are encoded on the frequency mf 0, and obtain the coded signal to be transmitted.

5. A time-frequency signal optical fiber transmission and distribution system, comprising a master end and a slave end; characterized in that: The master end comprises: The first laser and the second laser are used to simultaneously modulate the coded signal to be transmitted into a first laser signal with a wavelength of λ1 and a second laser signal with a wavelength of λ2; wherein λ1≠λ2; the coded signal to be transmitted is obtained by encoding the time signal to be transmitted and the frequency signal to be transmitted from a time-frequency reference source, and the frequency signal to be transmitted is subjected to frequency multiplication processing before being encoded; A first wavelength division multiplexer, used for wavelength division and combining the first laser signal and the second laser signal; Optical amplifier, used to amplify the laser signal after wavelength division and beam combination; An optical splitter is used to split the amplified laser signal into multiple laser signals, which are respectively transmitted to multiple slave ends through different optical fiber links; The slave end comprises: A second wavelength division multiplexer is used to perform wavelength division output on the received laser signal to obtain a first wavelength division laser signal with a wavelength of λ1 and a second wavelength division laser signal with a wavelength of λ2; The first photodetector and the second photodetector are used to demodulate the coded signal from the first wavelength division laser signal and the second wavelength division laser signal respectively; The first decoder and the second decoder are used to decode the demodulated coded signal to obtain a first demodulated coded signal and a second demodulated coded signal respectively; The first carrier recovery module and the second carrier recovery module are used to recover the time information, the first frequency signal and the second frequency signal from the first demodulated coded signal and the second demodulated coded signal respectively; the phase detector is used to perform phase detection on the first frequency signal and the second frequency signal to obtain a phase difference; The frequency servo purification module is used to compensate the optical fiber link noise according to the phase difference and the second frequency signal to obtain a compensation frequency signal, so that the frequency of the compensation frequency signal is equal to the frequency of the main end to be transmitted after frequency doubling processing; A frequency distributor is used to divide the compensation frequency signal into a frequency equal to the frequency of the frequency signal to be transmitted at the main end, and then distribute it into multiple outputs with the same performance; A time regeneration module is used to delay the first frequency signal according to the time information N cycles, and obtain a time signal roughly synchronized with the time signal to be transmitted; Phase compensation module, used to compensate the coarse synchronization time signal according to the phase shift value After phase shifting, a time signal synchronized with the time signal to be transmitted is obtained; wherein, the transmission time of the laser signal in the optical fiber link between any slave end and the master end is divided by the period of the frequency signal in the coded signal to be transmitted at the master end, and the integer part obtained is N , the remainder is The transmission time of the laser signal in the optical fiber link between any slave end and the master end is calculated based on the phase difference and the laser wavelength difference between the first laser signal and the second laser signal; The time distributor is used to distribute the time signal synchronized with the time signal to be transmitted into multiple outputs with the same performance.

6. The time-frequency signal optical fiber transmission and distribution system according to claim 5, characterized in that: The method for calculating the transmission time of the laser signal in the optical fiber link between any slave end and the master end comprises: in, It represents the transmission time of the laser signal in the optical fiber link between any slave end and the master end. Indicates the length of the optical fiber link between any slave end and the master end. represents the refractive index of the first laser signal in the optical fiber link, represents the speed of light in vacuum, represents the phase difference, represents the dispersion coefficient of the optical fiber, Indicates the laser wavelength difference between the first laser signal and the second laser signal.

7. The time-frequency signal optical fiber transmission and distribution system according to claim 5, characterized in that: In the frequency servo purification module, the optical fiber link noise is compensated to obtain a compensation frequency signal, including: The frequency servo purification module serves the VCOCXO inside the frequency servo purification module according to the phase difference and the second frequency signal, so that the VCOCXO outputs a compensation frequency signal.

8. The optical fiber transmission and distribution system for time-frequency signals according to claim 5, characterized in that: The master end also includes a frequency multiplier and an encoder; The frequency multiplier is used to multiply the frequency emitted by the time-frequency reference source by 1 before encoding the frequency signal to be transmitted. f 0 frequency signal to be transmitted m times, the frequency is mf 0 frequency signal; The encoder is used to mf The frequency signal of 0 is used as the carrier signal, and the time signal to be transmitted and the corresponding time code information are encoded on the frequency mf 0, and obtain the coded signal to be transmitted.

9. The optical fiber transmission and distribution system for time-frequency signals according to claim 5, characterized in that: It also includes a time code source; the time code source is used to output time code information.

10. The optical fiber transmission and distribution system for time-frequency signals according to claim 5, characterized in that: When slave ends are added, a new optical amplifier and a new optical splitter are sequentially added between the optical splitter and any original slave end, and the new optical splitter is respectively connected to each of the added slave ends.

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