CN115842589A - Relay node downloading method and device based on optical frequency comb - Google Patents
Relay node downloading method and device based on optical frequency comb Download PDFInfo
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- CN115842589A CN115842589A CN202211358873.0A CN202211358873A CN115842589A CN 115842589 A CN115842589 A CN 115842589A CN 202211358873 A CN202211358873 A CN 202211358873A CN 115842589 A CN115842589 A CN 115842589A
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Abstract
The invention discloses a relay node downloading method and device based on an optical frequency comb. The invention is used for solving the problem that a node end is difficult to obtain frequency information transmitted in a link in a time-frequency information transmission system, and is characterized in that an optical coupling module is used for obtaining an optical comb signal transmitted in the link of the time-frequency transmission system based on an optical comb and a returned optical comb signal, the transmitted optical comb signal is converted into an electric signal through a photoelectric detection module, two paths of electric signals are obtained through a power distribution module, the central frequencies of electric band-pass filters respectively connected with the two paths of electric signals are adjusted, a low-order harmonic component and a high-order harmonic component with the frequency being twice of the relation are obtained, the returned optical comb signal is subjected to image processing, the two low-order harmonic components are connected to a phase detection module to obtain relative time delay information, and the high-order harmonic component is directly subjected to phase shifting through a phase shifting module according to the time delay information, so that an original signal can be recovered. Compared with the prior art, the method and the device make full use of the characteristic that the optical comb signal contains multi-frequency components, avoid using complex electrical devices such as a frequency divider, a frequency multiplier and the like, reduce the cost, obviously reduce the electrical noise of the download node, and improve the stability of node frequency extraction.
Description
Technical Field
The invention relates to the field of time frequency transmission and measurement in information science, in particular to a multipoint downloading method based on an optical frequency comb.
Background
The time is one of seven physical quantities as a basic measurement unit, which relates to aspects of life, and the precision and the accuracy of time measurement are more and more emphasized by people. With the development of the prior art, the accuracy of the atomic optical clock is higher and higher, and reaches 1E-18 order, the existing remote transmission technology can not meet the requirement of high-accuracy optical clock remote comparison developed at a rapid speed, and how to accurately transmit the time and frequency information of the atomic clock becomes an important research direction. The optical fiber is used as the best propagation medium of the existing light wave, the communication is carried out by using the optical fiber, the optical fiber has the advantages of long transmission distance, high transmission speed, low loss, strong anti-interference capability and the like, and time-frequency transmission based on the optical fiber becomes the preferred scheme of a ground clock comparison network in the future.
The high-precision long-distance optical fiber time-frequency transmission technology mainly comprises three types, namely radio frequency modulation, optical frequency direct transmission and optical frequency comb transmission. Compared with other methods, the optical frequency comb is a mode-locked laser with stable frequency and phase, and can simply and accurately link the optical frequency with the cesium atom microwave frequency standard due to the characteristic that the optical frequency comb can generate a large number of coherent spectral lines which are arranged at equal intervals, so that the optical frequency comb has very wide application and prospect in optical precision measurement.
Most of the existing time-frequency transmission systems are based on point-to-point transmission, and if more than two nodes want to use the frequency information transmitted by the system, the time-frequency transmission system with a point-to-point structure cannot work normally. In order to obtain the transmitted frequency information at any node of the optical fiber link, many schemes and structures have been proposed, but most of them are based on radio frequency modulation and optical frequency direct transmission, and the general structure is complex and the frequency extraction stability is poor. The optical frequency comb has a lot of gaps in the aspect of optical frequency comb, and the structure of extracting frequency information by nodes can be theoretically optimized by utilizing the multi-frequency component characteristic and the high signal-to-noise ratio characteristic of the optical frequency comb, so that the cost is reduced, and the stability of frequency extraction is improved.
Disclosure of Invention
In order to fill the gap of the optical frequency comb and fully utilize the characteristics of the optical frequency comb, the invention provides a multipoint downloading method based on the optical frequency comb. The method can be used on most complete time-frequency transmission systems based on the optical frequency comb; the optical comb signal can be extracted from any node on a transmission link by using an optical fiber coupling module; utilizing the photoelectric detection module and a band-pass filter corresponding to the central frequency to obtain an N frequency multiplication signal and a 2N frequency multiplication signal of a round-trip optical comb signal; obtaining a phase difference between N frequency doubling signals of a round-trip optical comb signal by using a phase detection module, wherein the phase difference is twice of the phase delay of a link to be compensated of the N frequency doubling signals at a node; based on the characteristics of the optical frequency comb, the phase difference is equal to the link phase delay of the 2N frequency multiplication signal at the node to be compensated, and the phase information is used for controlling the phase shift module, so that the compensation of the 2N frequency multiplication signal at the node can be completed.
The technical scheme of the invention is as follows:
a multipoint downloading method based on an optical frequency comb comprises the following steps:
1) Selecting a node on a complete time-frequency transmission system based on optical frequency comb, and obtaining an optical comb signal 1 sent by the node and a returned optical comb signal 2 by using an optical fiber coupling module under the condition of not influencing the normal transmission of link signals;
2) Converting an optical comb signal 1 and an optical comb signal 2 into an electric signal 1 and an electric signal 2 by using a photoelectric detection module;
3) Dividing an electric signal 1 into an electric signal 3 and an electric signal 4 through a power distribution module, wherein the electric signal 3 passes through a band-pass filtering module with the central frequency being N times of optical comb repetition frequency, and the electric signal 4 passes through a band-pass filtering module with the central frequency being 2N times of optical comb repetition frequency, wherein the electric signal 3 is changed into a sinusoidal signal with the frequency being N times of repetition frequency, and the electric signal 4 is changed into a sinusoidal signal with the frequency being 2N times of repetition frequency;
4) The electrical signal 2 is the same as above, wherein the sinusoidal signal with the frequency of N times of repetition frequency is the electrical signal 5, and the sinusoidal signal with the frequency of 2N times of repetition frequency is the electrical signal 6;
5) The electric signal 3 and the electric signal 5 are led into a phase detection module to obtain the difference of phase information carried by the two signals
6) Using a phase-shifting module to change the phase information of the electrical signals 4 and 6, the electrical signals 4 are shifted in phase
Electrical signal 6 is phase shifted>
Namely, the compensation of the signal is completed, and the original signal of the time-frequency transmission system is recovered.
Furthermore, the complete optical frequency comb-based time-frequency transmission system comprises a source end, a transmission link and a far end, and has a compensation structure capable of pre-compensating the phase delay generated by the whole link, so that the phase delay of the whole link is compensated by the signal transmitted in the link.
Further, the repetition frequency of the optical comb is determined by the optical frequency comb itself used in the time-frequency transfer system.
Further, the power distribution module can be replaced by adding an optical fiber coupling module in front of the photoelectric detection module, namely the optical fiber coupling module is used for dividing the optical comb signal 1 into an optical comb signal 3 and an optical comb signal 4, the optical comb signal 2 is divided into an optical comb signal 5 and an optical comb signal 6, and then the optical comb signal is converted into an electric signal 3, the electric signal 4, the electric signal 5 and the electric signal 6 through the photoelectric detection module, and the subsequent steps are the same as the above.
Further, the value of N should be determined according to whether the center frequency of the band pass filter and the power of the N-fold repetition frequency component satisfy the experimental requirements.
Further, the air conditioner is provided with a fan,
theoretically, the phase delay of the optical comb signal is twice of the phase delay of the N-times of the heavy frequency components after the optical comb signal is transmitted from the node to the far end of the system.
Further, the air conditioner is provided with a fan,
theoretically equal to the phase delay of the 2N multiple of the repetition frequency component in the optical comb signal after the optical comb signal is transmitted from the node to the far end of the system.
The optical fiber coupling module is used for dividing optical comb signals transmitted back and forth in an optical fiber link into two paths, wherein one path of the optical comb signals continuously participates in signal transmission of the whole system, and the other path of the optical comb signals participates in a multipoint downloading method. The splitting ratio is determined by actual conditions, and light needs to be split on the premise that time-frequency information transmission of the whole system is not affected as much as possible.
The band-pass filtering module is used for extracting sinusoidal signals corresponding to the center frequency in the electric signals 3 and 4, the sinusoidal signals are generated as the characteristics of the optical frequency comb, and the frequency of the sinusoidal signals is integral multiple of the repetition frequency of the optical frequency comb. By utilizing the characteristic, sine waves with different frequencies can be obtained by adjusting the center frequency of the band-pass filtering module, so that the frequency multiple adjustment of the obtained signals by using additional devices such as a frequency multiplier, a frequency divider and the like is avoided.
The phase shift module is used for shifting the phase of the electrical signals 4 and 6, and can perform forward phase shift or reverse phase shift on the reference signal through the input phase information.
Compared with the prior art, the invention has the beneficial effects that:
(1) The phase delay of the signal at the node end, which needs to be compensated, can be obtained by performing photoelectric detection, filtering and phase detection on the extracted round-trip optical comb signal, so that the change of the structure of a time-frequency transmission system is avoided, and the use of a complex device at the node end is avoided;
(2) The optical frequency comb is used as a light source of a time-frequency transmission system using a multipoint downloading technology, and sine waves with different times of repetition frequencies can be obtained by adjusting the central frequency of a band-pass filtering module after photoelectric detection by utilizing the characteristic that the optical frequency comb can generate a large number of coherent spectral lines arranged at equal intervals, so that the use of electric devices such as a frequency multiplier and a frequency divider is avoided, the electrical noise of a downloading node is remarkably reduced, and the stability of node frequency extraction is further improved;
(3) And (2) the phase shift module is used for shifting the phase of the signal obtained at the node end, the center frequency of the band-pass filter module is adjusted to change the frequency of the reference signal accessed by the phase shift module, and the phase information obtained in the step (1) can be directly used for shifting the phase without additional operation. Therefore, the invention fully utilizes the characteristics of the optical frequency comb, optimizes the existing multipoint downloading structure, reduces the error introduced by the electrical device, reduces the cost and improves the accuracy of recovering the original signal.
Drawings
Fig. 1 is a system structure diagram of a multi-point download method based on an optical frequency comb according to the present invention.
Fig. 2 is a system structure diagram of the multi-point downloading method based on the optical frequency comb after adding the optical fiber coupling module.
Fig. 3 is a schematic structural diagram of an embodiment of a multi-point downloading method based on an optical frequency comb according to the present invention.
Detailed Description
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, the optical fiber coupling device comprises an optical comb signal 1, an optical comb signal 2, an optical fiber coupling module, two photoelectric detection modules, two power distribution modules, four band-pass filtering modules, a phase detection module and a phase shifting module.
The optical comb signal 1 is an optical comb signal sent by a source end, and the optical comb signal 2 is an optical comb signal returned by a far end, so that a time-frequency transmission system is required to delay the phase of an overall link
Pre-compensation is performed.An optical comb signal 1 and an optical comb signal 2 enter an optical fiber coupling module and are respectively divided into optical comb signals 3 and 4 and optical comb signals 5 and 6, the optical comb signal 3 and the optical comb signal 5 reenter a link to participate in time-frequency transmission, and the optical comb signal 4 and the optical comb signal 6 are introduced into a photoelectric detection module to obtain an electric signal 1 and an electric signal 2. The electric signal 1 is divided into an electric signal 3 and an electric signal 4 after passing through the power distribution module, the electric signal 2 is divided into an electric signal 5 and an electric signal 6 after passing through the power distribution module, the electric signal 3 and the electric signal 5 are changed into sine signals with frequency being N times of repetition frequency through the band-pass filtering module with central frequency being N times of optical comb repetition frequency, and phase information is/is respectively>
And &>
Then, the electric signal 3 and the electric signal 5 enter the phase detection module to obtain the phase difference between the two signals>
The electric signal 4 and the electric signal 6 pass through the band-pass filtering module with the center frequency of 2N times of the optical comb repetition frequency to be changed into sine signals with the frequency of 2N times of the repetition frequency, and the phase information is ^ er and greater than or equal to>
And &>
The phase information obtained by the phase detection module is used for controlling the phase shift module to carry out positive phase shift and reverse phase shift on the electric signals 4 and 6, so that phase delay can be compensated at a node, and the original signals are recovered.
The power distribution module can be replaced by more optical fiber coupling modules, referring to fig. 2, the optical comb signal 4 and the optical comb signal 6 are respectively divided into optical comb signals 7 and 8 and optical comb signals 9 and 10 through one optical fiber coupling module, and then are converted into electric signals 3, 4, 5 and 6 through the photoelectric detection module, and the subsequent steps are the same as the scheme.
The invention will be further explained by taking an example of an optical frequency comb with a repetition frequency of 100MHz and a bandpass filter module with N value of 1.
The embodiment is as follows:
referring to fig. 3, the method includes the steps of:
1) The transmitted optical comb signal 1 and the optical comb signal 2 are introduced into an optical fiber coupling module and are divided into optical comb signals 3 and 4 and optical comb signals 5 and 6, and the optical comb signal 3 and the optical comb signal 5 reenter a link to participate in time-frequency transmission;
2) The optical comb signal 4 and the optical comb signal 6 are converted into an electric signal 1 and an electric signal 2 through a photoelectric detection module;
3) The electric signal 1 and the electric signal 2 are respectively divided into an electric signal 3, an electric signal 4, an electric signal 5 and an electric signal 6 through a power distribution module;
4) After the electrical signal 3 and the electrical signal 5 pass through the band-pass filtering module with the center frequency of 100MHz, the amplitude influence of the sinusoidal signal is ignored, and the amplitude influence is respectively recorded as:
wherein, ω is 1 =100MHz, the overall phase delay of the transmission link is recorded as
Node to source side link phase delay of ^ 4>
Node to far-end link phase delay of ^ 4>
Then->
Because the system delays the phase of the entire link->
Is pre-compensated, then>
5) Then the electric signal 3 and the electric signal 5 are led into a phase detection module to obtain the phase difference between the two signals
6) After the electric signal 4 and the electric signal 6 pass through the band-pass filtering module with the center frequency of 200MHz, the amplitude influence of the sinusoidal signal is ignored, and the amplitude influence is respectively recorded as:
wherein, ω is 2 ＝200MHz.
7) Phase difference obtained by using the phase detection module
Phase-shifting electrical signals 4 and 6, the electrical signal 4 being phase-shifted>
Electric signal 6 phase>
Thus the phase-shifted signal F 4 '(t)＝F 6 '(t)＝sin(ω 2 t), the phase delay in the signal has been compensated and the original signal has been recovered.
The above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and a person skilled in the art can make modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the present invention, and the scope of protection of the present invention should be subject to the claims.
Claims (7)
1. A multipoint downloading method based on an optical frequency comb comprises the following steps:
1) An optical coupling module is used for obtaining an optical frequency comb signal (1) and an optical frequency comb signal (2) which are back and forth in a link at a node end of the complete frequency transmission system;
2) The optical frequency comb signal (1) and the optical frequency comb signal (2) are respectively converted into an electric signal (1) and an electric signal (2) through a photoelectric detection module, then the electric signal (1) is divided into an electric signal (3) and an electric signal (4) through a power distribution module, and the electric signal (2) is divided into an electric signal (5) and an electric signal (6);
3) The electric signals (3), (4), (5) and (6) are connected to a band-pass filter and converted into electric signals (7), (8), (9) and (10).
4) The electric signal (7) and the electric signal (9) are accessed into a phase detection module to obtain the phase difference between the two signals;
5) The phase difference control phase shift module is used for respectively shifting the phase of the electric signal (8) and the phase of the electric signal (10) and compensating the phase drift introduced by optical fiber transmission.
2. The method of claim 1, wherein the full frequency transmission system is a system having a source, a remote, a transmission link, and a structure capable of compensating for overall transmission link drift. The light source of the source end in the system is an optical comb light source with determined fundamental frequency, and the frequency information transmission of the whole system cannot be influenced by the addition of the node end in the transmission link.
3. A method according to claim 1, characterized in that the electrical signal (1), (2), (3), (4), (5), (6) contains a number of frequency components, each frequency component having a frequency which is a positive integer multiple of the fundamental frequency of the optical comb.
4. Method according to claim 1, characterized in that the center frequency of the bandpass filter previously accessed for the electrical signal (7) and the electrical signal (9) is N times the fundamental optical comb frequency, and the center frequency of the bandpass filter previously accessed for the electrical signal (8) and the electrical signal (10) is 2N times the fundamental optical comb frequency.
5. Method according to claim 1, characterized in that the electrical signals (7), (8), (9), (10) comprise only one frequency component, wherein the frequencies of the electrical signals (7) and (9) are N times the fundamental optical comb frequency and the frequencies of the electrical signals (8) and (10) are 2N times the fundamental optical comb frequency.
6. The method according to claim 1 or 2, wherein the phase difference obtained by the phase detection module is two times of the phase delay of the multiplied-by-N component of the optical comb signal after the optical comb signal is transmitted from the node end to the far end, and is equal to the phase delay of the multiplied-by-N component.
7. The method according to claim 1, 2 or 6, characterized in that the phase shift module uses the electrical signal (8) and the electrical signal (10) as reference signals, the value of the phase delay to be compensated is equal to the value of the phase difference obtained after the electrical signal (7) and the electrical signal (9) are connected to the phase detection module, the phase shift module with the reference signal being the electrical signal (8) needs to perform positive phase shift on the signal, and the phase shift module with the reference signal being the electrical signal (10) needs to perform negative phase shift on the signal.
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