A phase noise compensation enhancement method and system for optical fiber optical frequency transfer

Abstract

The application discloses a phase noise compensation enhancement method and system for optical fiber optical frequency transmission, and relates to the technical field of optical communication and signal processing. The local high-precision laser source is transmitted to the remote end through an optical fiber, and frequency comparison is performed by beating with the remote laser source. Comparison data is obtained by measuring the beat signal through a phase counter. The local compensation radio frequency signal and the uncompensated signal are collected through a digital circuit, and the measurement time interval of the two signals is set. Then, the signals are connected to the phase counter for measurement. The compensation deviation data is obtained by subtracting the measured two-phase signals. The comparison data is subtracted by the compensation deviation data, so that the phase noise suppression enhancement is realized, the phase control bandwidth of the optical fiber optical frequency transmission is improved, and the transmission signal precision is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical communication and signal processing, in particular to a phase noise compensation enhancement method, system, device and medium for optical fiber optical frequency transfer. BACKGROUND

[0002] Optical fiber optical frequency transfer is to transfer high-precision optical frequency signals through optical fibers, realize remote transfer and comparison of frequency signals, and has advantages of high precision, low loss and anti-interference, and has important applications in high-precision time-frequency standards, optical communication, scientific research and other fields; in order to ensure the precision of the transferred signal, the phase noise introduced by the environmental disturbance of the optical fiber needs to be overcome, such as temperature change, vibration interference, etc.

[0003] The current optical fiber optical frequency transfer scheme is to compare the phase noise between the round-trip transfer signal and the reference signal through the optical fiber interference method, and to compensate the phase noise, so as to realize high-fidelity optical frequency signal transmission; however, the inherent optical fiber time delay in the optical frequency signal transmission process limits the phase-locked bandwidth and noise suppression amplitude, and further limits the transfer precision; at present, although the transfer method of multi-stage relay can be used to improve the system phase-locked bandwidth, the relay scheme greatly increases the system structure complexity and reduces the system reliability, so that the current solution limits the control bandwidth under the optical fiber time delay, so that the precision of the transferred signal is low, and it is difficult to be applied to high-precision optical fiber optical frequency transfer. SUMMARY

[0004] The embodiment of the present application provides a phase noise compensation enhancement method and system for optical fiber optical frequency transfer, which can solve the problem that the current solution limits the control bandwidth under the optical fiber time delay, so that the precision of the transferred signal is low, and it is difficult to be applied to high-precision optical fiber optical frequency transfer.

[0005] The embodiment of the present application provides a phase noise compensation enhancement method for optical fiber optical frequency transfer, comprising the following steps:

[0006] The sending end divides the optical frequency signal into a first optical frequency signal and a second optical frequency signal, and the first optical frequency signal is transmitted to the receiving end through the optical fiber line;

[0007] The receiving end divides the first optical frequency signal transmitted to the receiving end into a third optical frequency signal and a fourth optical frequency signal, the third optical frequency signal is output to the user end, and the fourth optical frequency signal is returned to the sending end along the original path through the Faraday mirror; the sending end detects the beat frequency signal of the second optical frequency signal and the fourth optical frequency signal, demodulates the beat frequency signal, and obtains the optical fiber line phase noise signal;

[0008] The sending end measures the phase of the optical fiber line phase noise signal and the first optical frequency signal, adjusts the measurement time interval of the optical fiber line phase noise signal and the first optical frequency signal when measuring the phase, obtains the measured phase of the optical fiber line phase noise signal and the first optical frequency signal, and obtains the phase noise deviation data by subtracting the measured phase of the optical fiber line phase noise signal and the first optical frequency signal.

[0009] The receiving end measures the phase of the first optical frequency signal transmitted to the receiving end to obtain the transmission signal phase data, subtracts the phase noise deviation data from the transmission signal phase data to compensate the phase noise of the first optical frequency signal transmitted to the receiving end, obtains the first optical frequency signal after phase noise compensation, and outputs the split third optical frequency signal to the user end.

[0010] Preferably, the phase noise deviation data is obtained by:

[0011] The phase of the optical fiber line phase noise signal is set as The phase of the second optical frequency signal is set as The phase of the first optical frequency signal is set as ;

[0012] At the moment t , the phase of the transmission signal received by the receiving end is , which is expressed as:

[0013] ;

[0014] Wherein: represents the phase jitter introduced by the forward transmission of the optical signal through the optical fiber line; represents the time required for a single transmission of the optical frequency signal through the optical fiber line;

[0015] The phase noise deviation data is obtained by comparing the round-trip signal and the reference signal, which is expressed as:

[0016] ;

[0017] Wherein: represents the phase jitter introduced by the reverse transmission of the optical signal through the optical fiber line;

[0018] The measurement time interval of the optical fiber line phase noise signal and the first optical frequency signal when measuring the phase is adjusted, and the phase of the optical fiber line phase noise signal and the first optical frequency signal is subtracted to obtain the phase noise deviation data.

[0019] Preferably, the phase measurement of the sending end and the receiving end comprises:

[0020] An optical fiber time synchronization method is adopted to provide a unified time reference for the phase measurement devices of the sending end and the receiving end;

[0021] The time stamp is added during phase data acquisition, and the timing deviation formed by transmission delay is corrected by an algorithm.

[0022] Preferably, the path of the fourth optical frequency signal returning to the sending end along the original path in reverse through the Faraday mirror comprises:

[0023] The fourth optical frequency signal is reflected by the Faraday mirror, and the reflected fourth optical frequency signal returns to the optical fiber line through the second beam splitter and is transmitted to the sending end in reverse, is input through the second interface of the circulator, and is output to the detector through the third interface of the circulator.

[0024] Preferably, at the sending end, after the optical frequency signal is split into a first optical frequency signal and a second optical frequency signal by the first beam splitter, the first optical frequency signal is modulated by the first acousto-optic modulator and transmitted to the receiving end by the optical fiber line.

[0025] At the receiving end, the first optical frequency signal transmitted by the optical fiber line is modulated by the second acousto-optic modulator and split into a third optical frequency signal and a fourth optical frequency signal by the second beam splitter.

[0026] Preferably, the process of modulating the optical frequency signal by the first acousto-optic modulator comprises:

[0027] The radio frequency source RF1 and the radio frequency source RF2 respectively output driving signals with frequencies f1 and f2, and f1 and f2 are not equal.

[0028] Based on the driving signals with frequencies f1 and f2, the optical fiber line phase noise compensation signal and the optical fiber line phase noise uncompensation signal are separated by a frequency division multiplexing method, and the optical fiber line phase noise compensation signal and the optical fiber line phase noise uncompensation signal are independently extracted.

[0029] The embodiment of the application also provides an optical fiber optical frequency transmission phase noise compensation enhancement system, comprising:

[0030] The signal modulation module splits the optical frequency signal into a first optical frequency signal and a second optical frequency signal at the sending end, and the first optical frequency signal is transmitted to the receiving end by the optical fiber line.

[0031] The receiving end splits the first optical frequency signal transmitted to the receiving end into a third optical frequency signal and a fourth optical frequency signal, the third optical frequency signal is output to the user end, and the fourth optical frequency signal is returned to the sending end along the original path in reverse through the Faraday mirror; the sending end obtains the optical fiber line phase noise signal by phase demodulating the beat frequency signal of the second optical frequency signal and the fourth optical frequency signal.

[0032] The modulation compensation module measures the phase of the fiber line phase noise signal and the first optical frequency signal at the sending end, adjusts the measurement time interval of the fiber line phase noise signal and the first optical frequency signal at the time of phase measurement, obtains the measured phase of the fiber line phase noise signal and the first optical frequency signal, and obtains the phase noise deviation data by subtracting the measured phase of the fiber line phase noise signal and the first optical frequency signal.

[0033] The receiving end measures the phase of the first optical frequency signal transmitted to the receiving end, obtains the transmission signal phase data, subtracts the phase noise deviation data from the transmission signal phase data, compensates the phase noise of the first optical frequency signal transmitted to the receiving end, obtains the first optical frequency signal after phase noise compensation, and outputs the third optical frequency signal after beam splitting to the user end.

[0034] The embodiment of the present application also provides an electronic device, comprising a memory and a processor;

[0035] The memory is used for storing a computer program;

[0036] The processor is used for executing the computer program stored in the memory, and realizing the steps of the phase noise compensation enhancement method for optical fiber optical frequency transmission.

[0037] The embodiment of the present application also provides a computer readable storage medium, which is used for storing a computer program, and the computer program is executed by the processor to realize the steps of the phase noise compensation enhancement method for optical fiber optical frequency transmission.

[0038] The embodiment of the present application provides a phase noise compensation enhancement method and system for optical fiber optical frequency transmission, and the beneficial effects are as follows compared with the prior art:

[0039] The application splits the optical frequency signal of the sending end into a first optical frequency signal and a second optical frequency signal, the first optical frequency signal is transmitted to the receiving end through the optical fiber line; the first optical frequency signal transmitted to the receiving end is split into a third optical frequency signal and a fourth optical frequency signal, the third optical frequency signal is output to the user end, and the fourth optical frequency signal is returned to the sending end along the original path in reverse through the Faraday mirror, the beat frequency signal of the second optical frequency signal and the fourth optical frequency signal is detected through the detector, the beat frequency signal is phase demodulated to obtain the optical fiber line phase noise signal; the optical fiber line phase noise signal and the first optical frequency signal are phase measured, and the measurement time interval of the optical fiber line phase noise signal and the optical fiber line phase noise uncompensated signal in the phase measurement is adjusted, and the difference is obtained to obtain the phase noise compensation deviation data, and then the phase data of the first optical frequency signal transmitted to the receiving end is subtracted by the phase noise compensation deviation data, the phase noise compensation of the transmitted signal is realized, in the process, because the measurement time of the optical fiber line phase noise compensation signal lags behind the uncompensated signal, that is, by setting the measurement time interval of the optical fiber line phase noise uncompensated signal and the compensation signal, that is, by setting the measurement time interval of the compensation signal and the uncompensated signal, the optical fiber delay can be adjusted according to the actual situation, the phase compensation deviation caused by the delay is accurately eliminated in the later period, the process does not need to set multiple levels of relay to transmit the signal, and the signal is directly compensated, so that the phase-locked bandwidth and the noise suppression amplitude in the optical frequency signal transmission process can be improved, and the accuracy of the transmitted signal is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A flow chart of a phase noise compensation enhancement method for optical fiber optical frequency transmission provided by the embodiment of the application is provided.

[0041] Figure 2 A phase jitter diagram caused by the optical fiber line of the phase noise compensation enhancement method for optical fiber optical frequency transmission provided by the embodiment of the application is provided.

[0042] Figure 3 A phase noise diagram corresponding to the phase jitter caused by the optical fiber line of the phase noise compensation enhancement method for optical fiber optical frequency transmission provided by the embodiment of the application is provided. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application are described in detail below. In the following description, a large number of specific details are set forth in order to fully understand the application. However, the application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the concept of the application, therefore the application is not limited by the specific embodiments disclosed below.

[0044] Reference Figure 1The embodiment of the present application provides a phase noise compensation enhancement method for optical fiber optical frequency transmission, after the optical frequency signal output by a laser is split by a beam splitter 1, the signal is divided into two beams, one of which is connected to a loopback device interface 1 and is output by a loopback device interface 2, and then passes through an acousto-optic modulator 1 (AOM1), the acousto-optic modulator 1 is used for modulating the optical frequency signal, and the modulation signal is provided by two radio frequency sources (RF1 and RF2); the AOM1 output optical frequency signal reaches a signal receiving end through a fiber line, first passes through an acousto-optic modulator 2 (AOM2), the acousto-optic modulator output optical frequency signal is split into two beams by a beam splitter 2, one of which is output to a user, and the other is connected to a Faraday mirror, and the Faraday mirror returns the transmission signal to the sending end along the original transmission path in the reverse direction, the reverse optical frequency signal is output to the loopback device, input by the loopback device interface 2, and output from the loopback device interface 3, and is input to a detector together with the output light of the beam splitter 1, the detector detects the beat frequency signal of the two beams, and the beat frequency signal frequency is the sum of the modulation frequencies of the AOM1 and the AOM2, since the AOM1 has two frequency different radio frequency drives, therefore the detector detects two frequency signals, one of which is filtered and phase demodulated by a filter and a demodulator, so that the optical fiber line phase noise compensation signal can be obtained, and the noise compensation signal is fed back to the radio frequency drive 1, so that the optical fiber line noise compensation is realized.

[0045] The phase of the compensation signal provided by the radio frequency drive 1 is denoted as , the other frequency signal detected by the detector carries uncompensated optical fiber noise, and the phase of the other frequency signal is denoted as , and the phase of the transmission signal obtained at the receiving end is denoted as ; it can be known that at the moment t , the received signal phase can be represented as , through the above-described optical fiber noise compensation method, the following can be obtained:

[0046] .

[0047] Among them: represents the phase jitter introduced by the optical signal passing through the optical fiber line in the forward direction; represents the time required for the optical frequency signal to pass through the optical fiber line once; is obtained by comparing the round-trip signal and the reference signal, and can be represented as , wherein represents the phase jitter introduced by the optical signal passing through the optical fiber line in the reverse direction.

[0048] As can be known from the expression of , the compensation signal lags behind the noise signal in time relative to the transmission signal, thereby limiting the noise suppression bandwidth.

[0049] The application filters the other output signal of the probe through a filter at the sending end, and the filtered signal and the compensation signal are sent to a measuring device for phase measurement, and the time interval of the two is reasonably adjusted, and the difference between the two can obtain the phase noise compensation deviation data; at the receiving end, the phase of the transmission signal is measured by the phase measuring device, and the phase data of the transmission signal is obtained, and then the phase noise deviation data obtained at the local end is subtracted through post-processing, which can further reduce the signal noise, thereby improving the control bandwidth and the optical frequency signal transmission accuracy; it is known through derivation that when the time interval difference between the compensation signal phase and the uncompensated signal phase measured at the local end is 1.5 When the time interval difference between the compensation signal phase and the uncompensated signal phase measured at the local end is 1.5

[0050] The current optical fiber optical frequency transmission technology mainly focuses on real-time optical fiber phase noise compensation, but due to the limitation of optical fiber delay, the optical fiber phase noise cannot be completely compensated; the application measures the phase compensation deviation caused by the delay at the local end, and further eliminates the deviation through post-processing, thereby improving the phase control bandwidth of the optical fiber optical frequency transmission, and further improving the transmission accuracy; the application provides a high-precision optical frequency transmission means for the field of optical fiber optical frequency remote comparison and precise spectrum measurement; compared with the prior art, the signal phase control bandwidth and the phase noise suppression ratio will be effectively improved, thereby improving the signal transmission accuracy.

[0051] The application can be used for remote optical frequency comparison, transmitting the local high-precision laser source to the remote end through the optical fiber, and frequency comparison with the remote laser source by beating, measuring the beat signal by the phase counter to obtain comparison data; collecting the local compensation radio frequency signal and the uncompensated signal through the digital circuit, setting the measurement time interval of the two signals, and then connecting the signals to the phase counter for measurement, and the difference between the two phase signals measured by the method of the application can obtain the compensation deviation data; considering that the optical fiber delay is τ, the beat signal obtained at the remote end is delayed by 0.5τ through the delay optical fiber, and then counted by the phase counter, and the comparison data is subtracted by the deviation data, so as to realize the enhancement of the phase noise suppression, thereby improving the comparison accuracy.

[0052] The application simulates the traditional noise compensation scheme of the optical fiber optical frequency transmission and the phase noise compensation enhancement method of the application by using Matlab software, establishes a 500km optical fiber optical frequency transmission simulation model according to the optical fiber phase noise and time delay characteristics, calculates and compensates the compensation deviation data, and verifies that the phase noise compensation enhancement method of the application can effectively suppress the residual noise and further improve the transmission accuracy; for example Figure 2The figure is a schematic diagram of phase jitter caused by fiber line, as Figure 3 The figure is a schematic diagram of phase noise corresponding to phase jitter caused by fiber line, wherein the black line is fiber phase noise without compensation, the red line is phase noise after compensation by traditional scheme, and the blue line is phase noise after compensation by the method provided by the present application. It can be seen that the phase noise is further inhibited, and the phase inhibition bandwidth is also improved.

[0053] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A phase noise compensation enhancement method for optical fiber optical frequency transfer, characterized in that, The method comprises the following steps: The sending end divides the optical frequency signal into a first optical frequency signal and a second optical frequency signal, and the first optical frequency signal is transmitted to the receiving end through an optical fiber line; The receiving end divides the first optical frequency signal transmitted to the receiving end into a third optical frequency signal and a fourth optical frequency signal, the third optical frequency signal is output to the user end, and the fourth optical frequency signal is returned to the sending end along the original path through a Faraday mirror; the sending end obtains the optical fiber line phase noise signal by detecting the beat frequency signal of the second optical frequency signal and the fourth optical frequency signal and performing phase demodulation on the beat frequency signal; The sending end measures the phase of the optical fiber line phase noise signal and the first optical frequency signal, adjusts the measurement time interval of the optical fiber line phase noise signal and the first optical frequency signal during the phase measurement, obtains the measured phase of the optical fiber line phase noise signal and the first optical frequency signal, and obtains the phase noise deviation data by subtracting the measured phase of the optical fiber line phase noise signal and the first optical frequency signal; The receiving end measures the phase of the first optical frequency signal transmitted to the receiving end, obtains the transmission signal phase data, subtracts the phase noise deviation data from the transmission signal phase data, compensates the phase noise of the first optical frequency signal transmitted to the receiving end, obtains the first optical frequency signal after phase noise compensation, and outputs the divided third optical frequency signal to the user end; The phase noise deviation data is obtained by: setting the phase of the optical fiber link phase noise signal to setting the phase of the second optical frequency signal to setting the phase of the first optical frequency signal to ; At t the moment, the phase of the transfer signal received by the receiving end is , expressed as: ； wherein: denotes the phase jitter introduced by the optical signal passing through the optical fiber line in the forward direction; denotes the time required for a single pass of the optical frequency signal through the optical fiber line. By comparing the round-trip signal and the reference signal acquisition, denoted as: ； wherein: denotes the phase jitter introduced by the optical signal passing back through the optical fiber line. Adjusting the measurement time interval of the optical fiber line phase noise signal and the first optical frequency signal during the phase measurement, and subtracting the phase of the optical fiber line phase noise signal and the first optical frequency signal to obtain the phase noise deviation data; In the sending end, after the optical frequency signal is divided into a first optical frequency signal and a second optical frequency signal by a first beam splitter, the first optical frequency signal is modulated by a first acousto-optic modulator and then transmitted to the receiving end by an optical fiber line; In the receiving end, the first optical frequency signal transmitted by the optical fiber line is modulated by a second acousto-optic modulator and then divided into a third optical frequency signal and a fourth optical frequency signal by a second beam splitter; The process of modulating the optical frequency signal by the first acousto-optic modulator comprises: The radio frequency source RF1 and the radio frequency source RF2 respectively output driving signals with frequencies f1 and f2, and f1 and f2 are not equal; Based on the driving signals with frequencies f1 and f2, the optical fiber line phase noise compensation signal and the optical fiber line phase noise uncompensation signal are separated by a frequency division multiplexing method, and the optical fiber line phase noise compensation signal φ1 and the optical fiber line phase noise uncompensation signal are independently extracted.

2. The method of claim 1, wherein the method further comprises, The phase measurement of the sending end and the receiving end comprises: An optical fiber time synchronization method is used to provide a unified time reference for the phase measurement devices of the sending end and the receiving end; Time stamps are added during phase data acquisition, and the time sequence deviation caused by transmission delay is corrected through an algorithm.

3. The method of claim 1, wherein the method further comprises, The path through which the fourth optical frequency signal returns to the sending end along the original path through the Faraday mirror comprises: The fourth optical frequency signal is reflected by the Faraday mirror, the reflected fourth optical frequency signal returns to the optical fiber line through the second beam splitter, and after being transmitted to the sending end in reverse, it is input through the second port of the circulator and output to the detector through the third port of the circulator.

4. A phase noise compensation enhancement system for optical fiber optical frequency transfer, implementing a phase noise compensation enhancement method for optical fiber optical frequency transfer according to any one of claims 1 to 3, characterized in that, Comprise: The signal modulation module splits the optical frequency signal into a first optical frequency signal and a second optical frequency signal at the sending end, and the first optical frequency signal is transmitted to the receiving end through the optical fiber line; The receiving end splits the first optical frequency signal transmitted to the receiving end into a third optical frequency signal and a fourth optical frequency signal, the third optical frequency signal is output to the user end, and the fourth optical frequency signal is returned to the sending end along the original path through the Faraday mirror; The sending end obtains the optical fiber line phase noise signal by detecting the beat frequency signal of the second optical frequency signal and the fourth optical frequency signal, and phase demodulating the beat frequency signal; The modulation compensation module measures the phase of the optical fiber line phase noise signal and the first optical frequency signal at the sending end, adjusts the measurement time interval of the optical fiber line phase noise signal and the first optical frequency signal when measuring the phase, obtains the phase measured by the optical fiber line phase noise signal and the first optical frequency signal, and obtains the phase noise deviation data by subtracting the phase measured by the optical fiber line phase noise signal and the first optical frequency signal. The receiving end measures the phase of the first optical frequency signal transmitted to the receiving end, obtains the transfer signal phase data, subtracts the phase noise deviation data from the transfer signal phase data, and compensates the phase noise of the first optical frequency signal transmitted to the receiving end to obtain the first optical frequency signal after phase noise compensation, and outputs the third optical frequency signal after splitting to the user end.

5. An electronic device, comprising: Comprising: Memory and processor; The memory is used to store computer programs; The processor is used to execute the computer programs stored in the memory, and realizes the steps of the optical fiber optical frequency transfer phase noise compensation enhancement method according to any one of claims 1-3.

6. A computer readable storage medium characterized by, A computer program is stored, and the computer program is executed by the processor to realize the steps of the optical fiber optical frequency transfer phase noise compensation enhancement method according to any one of claims 1-3.

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