Method for improving distance measurement precision based on laser communication

Abstract

The invention provides a method for improving distance measurement precision based on laser communication, and relates to the technical field of laser communication, and the method comprises the steps: obtaining first communication data containing a first synchronization pulse from a second node through a first detector; adjusting a first oscillation frequency of a first oscillator through a first clock recovery unit until the first oscillation frequency and the first communication data have the same frequency to obtain a first decoding clock; monitoring the first oscillation frequency through a first frequency discriminator to obtain a first monitoring signal; based on the first decoding clock, decoding the first communication data through a first decoder to obtain a first synchronization pulse; on the basis of the first monitoring signal, the first converter is forbidden or enabled to work through the first control unit; converting the first synchronization pulse into a digital signal through a first converter to obtain a first receiving moment; the first receiving moment is used for ranging calculation.

Description

Technical Field

[0001] The present disclosure relates to the field of laser communication technology, and more specifically to a method for improving ranging accuracy based on laser communication. Background Art

[0002] With the development of space laser communication technology, space laser communication terminals have gradually become a standard configuration for satellite payloads. Using space laser communication terminals for ranging can expand the application value of space laser communication terminals, and at the same time improve the ranging accuracy between satellites or between satellites and the ground, as well as the satellite orbit determination accuracy.

[0003] The ranging technology based on laser communication and the space laser communication terminal also face the problems of instability and repeated disconnection / establishment of the laser communication link, which leads to large errors in some ranging data and affects the ranging accuracy of the ranging technology based on laser communication. Summary of the invention

[0004] In view of this, the present disclosure provides a method for improving ranging accuracy based on laser communication, which is applied to a first node, wherein the first node includes a first detector, a first clock recovery unit, a first control unit, a first decoder and a first converter, wherein the first clock recovery unit includes a first oscillator and a first frequency discriminator, and the method includes: obtaining first communication data including a first synchronization pulse from a second node through the first detector; adjusting the first oscillation frequency of the first oscillator through the first clock recovery unit until it has the same frequency as the first communication data to obtain a first decoding clock; monitoring the first oscillation frequency through the first frequency discriminator to obtain a first monitoring signal; decoding the first communication data through the first decoder based on the first decoding clock to obtain the first synchronization pulse; prohibiting or enabling the operation of the first converter through the first control unit based on the first monitoring signal; converting the first synchronization pulse into a digital signal through the first converter to obtain a first receiving time; the first receiving time is used for ranging calculation.

[0005] According to an embodiment of the present disclosure, based on the first monitoring signal, the first control unit prohibits or enables the operation of the first converter, including: prohibiting the operation of the first converter when the first monitoring signal does not satisfy a preset condition; enabling the operation of the first converter when the first monitoring signal satisfies the preset condition; wherein the preset condition indicates that the time duration during which the first monitoring signal is less than a threshold value is greater than a preset time duration.

[0006] According to an embodiment of the present disclosure, the first oscillation frequency is monitored by the first frequency discriminator to obtain a first monitoring signal, including: subtracting the first oscillation frequency from the frequency of the first communication data by the first frequency discriminator to obtain a frequency difference; and obtaining the first monitoring signal based on the frequency difference.

[0007] According to an embodiment of the present disclosure, applied to the above-mentioned second node, the above-mentioned second node includes a second detector, a second clock recovery unit, a second control unit, a second decoder and a second converter, the above-mentioned second clock recovery unit includes a second oscillator and a second discriminator, and the above-mentioned method also includes: obtaining second communication data containing a second synchronization pulse from the above-mentioned first node through the above-mentioned second detector; adjusting the second oscillation frequency of the above-mentioned second oscillator through the above-mentioned second clock recovery unit until it has the same frequency as the above-mentioned second communication data, so as to obtain a second decoding clock; monitoring the above-mentioned second oscillation frequency through the above-mentioned second discriminator to obtain a second monitoring signal; based on the above-mentioned second decoding clock, decoding the above-mentioned second communication data through the above-mentioned second decoder to obtain the above-mentioned second synchronization pulse; based on the above-mentioned second monitoring signal, prohibiting or enabling the above-mentioned second converter from working through the above-mentioned second control unit; converting the above-mentioned second synchronization pulse into a digital signal through the above-mentioned second converter to obtain a second receiving time; the above-mentioned second receiving time is used for the above-mentioned ranging calculation.

[0008] According to an embodiment of the present disclosure, the above-mentioned method also includes: converting the above-mentioned second synchronization pulse into a digital signal through the above-mentioned first converter to obtain a first sending time; converting the above-mentioned first synchronization pulse into a digital signal through the above-mentioned second converter to obtain a second sending time; based on a set of the above-mentioned first sending time, the above-mentioned first receiving time, the above-mentioned second sending time and the above-mentioned second receiving time, calculating the distance between the above-mentioned first node and the above-mentioned second node.

[0009] According to an embodiment of the present disclosure, the above-mentioned first node also includes a first encoder, the above-mentioned second node also includes a second encoder, and the above-mentioned method also includes: obtaining the above-mentioned second synchronization pulse and the above-mentioned second communication data through the above-mentioned first encoder; obtaining the above-mentioned first synchronization pulse and the above-mentioned first communication data through the above-mentioned second encoder.

[0010] According to an embodiment of the present disclosure, the above-mentioned first node also includes a first modulator, the above-mentioned second node also includes a second modulator, and the above-mentioned method also includes: sending the above-mentioned second communication data to the above-mentioned second node through the first modulator; sending the above-mentioned first communication data to the above-mentioned first node through the second modulator.

[0011] According to an embodiment of the present disclosure, the above-mentioned first clock recovery unit also includes a phase detector, and the above-mentioned method also includes: using the above-mentioned phase detector to make a difference in the phase of the above-mentioned first oscillation clock and the above-mentioned first communication data to obtain a phase difference; under the action of the above-mentioned phase difference and the above-mentioned frequency difference, adjusting and outputting the above-mentioned first oscillation frequency through the above-mentioned first oscillator.

[0012] According to an embodiment of the present disclosure, the above-mentioned first clock recovery unit also includes a first filter, a second filter and a summer, and the above-mentioned method also includes: filtering the above-mentioned phase difference through the above-mentioned first filter; filtering the above-mentioned frequency difference through the above-mentioned second filter; and summing the above-mentioned filtered phase difference and the above-mentioned filtered frequency difference through the above-mentioned summer to act on the above-mentioned first oscillator.

[0013] According to an embodiment of the present disclosure, the first node and the second node establish a communication link via a space link. When the space link is disconnected and / or the connection is unstable, the first oscillation frequency jitters; when the space link is stable, the first oscillation frequency is stable.

[0014] According to an embodiment of the present disclosure, a first decoding clock is obtained by adjusting the first oscillation frequency, thereby obtaining a first synchronization pulse; by monitoring the first oscillation frequency, a first monitoring signal reflecting whether the communication state between the first node and the second node is stable can be obtained; through the first monitoring signal, the operation of the first converter is prohibited or enabled, and the first synchronization pulse in the case of an unstable communication state can be eliminated, leaving the first synchronization pulse in the case of a stable communication state, so as to obtain a first receiving moment for ranging calculation based on the first synchronization pulse, thereby improving the ranging accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings.

[0016] Figure 1 The operational flow chart of the method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0017] Figure 2 A schematic diagram of a first node of a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0018] Figure 3 A schematic diagram of a second node of the method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0019] Figure 4A schematic diagram of a first clock recovery unit of a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0020] Figure 5 A schematic diagram of a ranging system for a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0021] Figure 6 A schematic diagram of ranging results of a ranging system according to an embodiment of the present disclosure that does not use a method for improving ranging accuracy based on laser communication is shown schematically.

[0022] Figure 7 A schematic diagram of ranging results of adding monitoring signals to a ranging system according to an embodiment of the present disclosure that does not use the method for improving ranging accuracy based on laser communication is schematically shown.

[0023] Figure 8 A schematic diagram of the ranging results of a ranging system according to a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0025] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0026] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0027] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0028] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure.

[0029] Conventional laser ranging methods mainly include pulse laser ranging methods, continuous wave laser ranging methods, triangulation ranging methods, etc. Satellite laser ranging, laser radar and other ranging technologies based on laser communication have the advantages of long measurement distance and high measurement accuracy compared with conventional laser ranging methods. For example, the ground-moon laser communication LLCD system (Laser Communications Relay Demonstration) has a ranging accuracy of about 1.3cm (RMS) at a distance of 380,000 kilometers. For example, the satellite-to-ground laser communication system LCRD (Laser Communication Relay Demonstration) has a ranging accuracy of 3mm (standard deviation) at a distance of 74,000 kilometers, which is about 2 orders of magnitude higher than the ranging accuracy of the radio channel at the same distance.

[0030] The ranging technology based on laser communication generally requires two-way communication to achieve ranging because the clocks at both ends of the communication are not synchronized. The ranging technology based on laser communication and the space laser communication terminal also face the problems of unstable laser communication links and repeated disconnection / establishment. The clock information of the ranging technology based on laser communication is contained in the data stream of the laser communication. When the communication link is disconnected and the connection is reestablished, the receiving end needs to re-lock the local digital clock to the clock information of the laser communication data stream. During the locking process of the local digital clock, the receiving end can normally receive the laser communication data stream and can normally decode the laser communication data stream. However, the phase difference between the local digital clock and the phase difference between the clock of the laser communication data stream is large, resulting in a large error in this part of the ranging data, thereby affecting the ranging accuracy of the ranging technology based on laser communication.

[0031] The present disclosure provides a method for improving ranging accuracy based on laser communication, which can improve the ranging accuracy of ranging technology based on laser communication.

[0032] Figure 1 The operational flow chart of the method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0033] According to an embodiment of the present disclosure, a method for improving ranging accuracy based on laser communication is applied to the first node.

[0034] Figure 2 A schematic diagram of a first node of a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0035] like Figure 2 As shown, the first node includes a first detector, a first clock recovery unit, a first control unit, a first decoder and a first converter. The first clock recovery unit includes a first oscillator and a first frequency detector.

[0036] like Figure 1 As shown, the method for improving ranging accuracy based on laser communication includes operations S110 to S160.

[0037] In operation S110, first communication data including a first synchronization pulse from a second node is obtained through a first detector.

[0038] According to an embodiment of the present disclosure, the first communication data may be serial data based on laser communication. The first synchronization pulse may be obtained according to the system clock of the second node. In one example, the first bit of the data frame of the first communication data may be the first synchronization pulse, that is, the first synchronization pulse is embedded in the header of the first communication data. The serial data based on laser communication of the second node may be sent to the first node at a fixed period, and the serial data based on laser communication of the second node carries the information of the system clock of the second node.

[0039] In operation S120, a first oscillation frequency of a first oscillator is adjusted by a first clock recovery unit until the first oscillation frequency has the same frequency as the first communication data, thereby obtaining a first decoding clock.

[0040] According to an embodiment of the present disclosure, the first oscillator may be a voltage controlled oscillator. The clock recovery process of the first node may be based on the clock recovery technology and the phase locking technology, by adjusting the first oscillation frequency, to obtain a first decoding clock having the same frequency as the system clock of the second node, that is, locking the local digital clock of the first node to the system clock of the second node.

[0041] In operation S130, the first oscillation frequency is monitored by a first frequency discriminator to obtain a first monitoring signal.

[0042] According to the embodiment of the present disclosure, based on the clock recovery technology and the phase locking technology, the communication state between the first node and the second node may be affected during the process of adjusting the first oscillation frequency. By monitoring the first oscillation frequency, a first monitoring signal reflecting the communication state may be obtained.

[0043] In operation S140, the first communication data is decoded by a first decoder based on a first decoding clock to obtain a first synchronization pulse.

[0044] In operation S150 , the first converter is disabled or enabled to operate through the first control unit based on the first monitoring signal.

[0045] In operation S160, the first synchronization pulse is converted into a digital signal by a first converter to obtain a first receiving time. The first receiving time is used for distance measurement calculation.

[0046] According to an embodiment of the present disclosure, the first converter may be a time-to-digital converter, which may record the first synchronization pulse and convert the time of recording the first synchronization pulse into a digital signal, thereby obtaining the first receiving time.

[0047] According to an embodiment of the present disclosure, when the communication state between the first node and the second node is unstable, the time when the first converter records the first synchronization pulse may shift, resulting in a measurement error.

[0048] According to an embodiment of the present disclosure, a first decoding clock is obtained by adjusting the first oscillation frequency, thereby obtaining a first synchronization pulse; by monitoring the first oscillation frequency, a first monitoring signal reflecting whether the communication state between the first node and the second node is stable can be obtained; through the first monitoring signal, the operation of the first converter is prohibited or enabled, and the first synchronization pulse in the case of an unstable communication state can be eliminated, leaving the first synchronization pulse in the case of a stable communication state, so as to obtain a first receiving moment for ranging calculation based on the first synchronization pulse, thereby improving the ranging accuracy.

[0049] According to an embodiment of the present disclosure, when the first monitoring signal does not meet a preset condition, the first converter is prohibited from operating; when the first monitoring signal meets a preset condition, the first converter is enabled to operate; wherein the preset condition indicates that the time duration during which the first monitoring signal is less than a threshold value is greater than a preset time duration.

[0050] In one example, the preset duration may be 20ms. After the first monitoring signal is less than the threshold value for a duration greater than 20ms, the communication state is considered to be stable, and the first control unit outputs a high-level signal to enable the first converter to work and output the first receiving time for ranging calculation. If the preset conditions are not met, the communication state is considered to be disconnected or in an unstable state for reestablishing the connection. The first control unit outputs a low-level signal to prohibit the first converter from working, remove the first synchronization pulse in the unstable state, and do not record the first receiving time in the unstable state.

[0051] According to an embodiment of the present disclosure, a first oscillation frequency and a frequency of the first communication data are subtracted by a first frequency discriminator to obtain a frequency difference; based on the frequency difference, a first monitoring signal is obtained.

[0052] According to an embodiment of the present disclosure, when the communication state is disconnected, the first monitoring signal corresponding to the frequency difference in this state is greater than a threshold, and the first detector cannot receive the first communication data.

[0053] According to an embodiment of the present disclosure, when the communication state begins to recover but is in an unstable state, the first monitoring signal corresponding to the frequency difference in this state may be less than a threshold value or greater than a threshold value within a preset time length. The received first communication data is decoded and the first synchronization pulse in the unstable state is obtained. In the absence of a first control unit, the first receiving moment in the unstable state is obtained, and the ranging calculation in the unstable state is performed, resulting in a ranging error. However, the first detector can receive the first communication data. Although the first oscillation frequency in the unstable state is close to the system clock of the second node, there is still a certain gap. Therefore, the frequency difference in the unstable state has no effect on the communication function, but it will affect the accuracy of the ranging.

[0054] According to an embodiment of the present disclosure, a method for improving ranging accuracy based on laser communication is applied to the second node.

[0055] Figure 3 A schematic diagram of a second node of the method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0056] like Figure 3 As shown, the second node includes a second detector, a second clock recovery unit, a second control unit, a second decoder and a second converter, and the second clock recovery unit includes a second oscillator and a second frequency discriminator.

[0057] According to an embodiment of the present disclosure, a method for improving ranging accuracy based on laser communication also includes: obtaining second communication data including a second synchronization pulse from a first node through a second detector; adjusting a second oscillation frequency of a second oscillator through a second clock recovery unit until the frequency is the same as that of the second communication data to obtain a second decoding clock; monitoring the second oscillation frequency through a second frequency discriminator to obtain a second monitoring signal; decoding the second communication data through a second decoder based on the second decoding clock to obtain a second synchronization pulse; based on the second monitoring signal, disabling or enabling the second converter to operate through a second control unit; converting the second synchronization pulse into a digital signal through a second converter to obtain a second receiving time; the second receiving time is used for ranging calculation.

[0058] According to an embodiment of the present disclosure, the second communication data may be serial data based on laser communication. The second synchronization pulse may be obtained according to the system clock of the first node. In one example, the first bit of the data frame of the second communication data may be the second synchronization pulse, that is, the second synchronization pulse is embedded in the header of the second communication data. The serial data based on laser communication of the first node may be sent to the second node at a fixed period, and the serial data based on laser communication of the first node carries the information of the system clock of the first node.

[0059] According to an embodiment of the present disclosure, the second oscillator may be a voltage controlled oscillator. The clock recovery process of the second node may be based on clock recovery technology and phase locking technology, and by adjusting the second oscillation frequency, a second decoding clock having the same frequency as the system clock of the first node is obtained, that is, the local digital clock of the second node is locked to the system clock of the first node.

[0060] According to the embodiment of the present disclosure, based on the clock recovery technology and the phase locking technology, the communication state between the first node and the second node may be affected during the process of adjusting the second oscillation frequency. By monitoring the second oscillation frequency, a second monitoring signal reflecting the communication state may be obtained.

[0061] According to an embodiment of the present disclosure, the second converter may be a time-to-digital converter, which may record the second synchronization pulse and convert the time of recording the second synchronization pulse into a digital signal, thereby obtaining the second receiving time.

[0062] According to an embodiment of the present disclosure, when the communication state between the first node and the second node is unstable, the time when the second converter records the second synchronization pulse may shift, resulting in a measurement error.

[0063] According to an embodiment of the present disclosure, a second decoding clock is obtained by adjusting the second oscillation frequency, thereby obtaining a second synchronization pulse; by monitoring the second oscillation frequency, a second monitoring signal reflecting whether the communication state between the first node and the second node is stable can be obtained; through the second monitoring signal, the second converter is prohibited or enabled to operate, and the second synchronization pulse in the case of an unstable communication state can be eliminated, leaving the second synchronization pulse in the case of a stable communication state, so as to obtain a second receiving time for ranging calculation based on the second synchronization pulse, thereby improving the ranging accuracy.

[0064] According to an embodiment of the present disclosure, the method for improving ranging accuracy based on laser communication also includes: converting the second synchronization pulse into a digital signal through a first converter to obtain a first sending time; converting the first synchronization pulse into a digital signal through a second converter to obtain a second sending time; based on a set of first sending time, first receiving time, second sending time and second receiving time, calculating the distance between the first node and the second node.

[0065] According to an embodiment of the present disclosure, the first node records the time of sending the second synchronization pulse through the first converter to obtain the first sending time. The second node records the time of sending the first synchronization pulse through the second converter to obtain the second sending time.

[0066] According to an embodiment of the present disclosure, the process of ranging calculation is as follows.

[0067] After the first node and the second node establish a laser communication link, the first node and the second node send and receive serial data to each other and obtain a set of ranging data: the first sending time , first receiving time , Second sending time and the second reception time Ignoring atmospheric delay and relativistic effects, a set of distance measurement data can be used to calculate the distance .distance The calculation formula is as follows:

[0068]

[0069] in, The speed of light.

[0070] According to an embodiment of the present disclosure, the first node further includes a first encoder, and the second node further includes a second encoder. The method for improving ranging accuracy based on laser communication also includes: obtaining a second synchronization pulse and a second communication data through the first encoder; and obtaining a first synchronization pulse and a first communication data through the second encoder.

[0071] According to an embodiment of the present disclosure, the first node further includes a first modulator, and the second node further includes a second modulator. The method for improving ranging accuracy based on laser communication also includes: sending the second communication data to the second node through the first modulator; and sending the first communication data to the first node through the second modulator.

[0072] According to an embodiment of the present disclosure, the first modulator may be a parallel-to-serial conversion circuit, which may modulate the serial data of the second communication data into an optical signal for transmission in the communication link. The second modulator may be a parallel-to-serial circuit, which may modulate the serial data of the first communication data into an optical signal for transmission in the communication link.

[0073] Figure 4 A schematic diagram of a first clock recovery unit of a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0074] According to an embodiment of the present disclosure, the first clock recovery unit recovers the system clock of the second node contained in the first communication data based on a phase-locked loop structure.

[0075] like Figure 4 As shown, the first clock recovery unit further includes a phase detector.

[0076] According to an embodiment of the present disclosure, the method for improving ranging accuracy based on laser communication also includes: using a phase detector to differentiate the phases of a first oscillation clock and first communication data to obtain a phase difference; and under the action of the phase difference and the frequency difference, adjusting and outputting the first oscillation frequency through a first oscillator.

[0077] According to the embodiments of the present disclosure, the first synchronization pulse in the communication re-establishment stage is eliminated by monitoring the frequency difference. On the one hand, ranging data with large errors is eliminated, thereby improving ranging accuracy. On the other hand, the functional properties of the phase-locked loop structure are not changed, and the normal communication function of the first node is not affected.

[0078] like Figure 4 As shown, the first clock recovery unit further includes a first filter, a second filter and a summer.

[0079] According to an embodiment of the present disclosure, the method for improving ranging accuracy based on laser communication also includes: filtering the phase difference through a first filter; filtering the frequency difference through a second filter; and summing the filtered phase difference and the filtered frequency difference through a summer to act on the first oscillator.

[0080] According to an embodiment of the present disclosure, a first node and a second node establish a communication link via a space link. When the space link is disconnected and / or the connection is unstable, the first oscillation frequency jitters; when the space link is stable, the first oscillation frequency is stable.

[0081] According to an embodiment of the present disclosure, the first node monitors the first oscillation frequency in real time. During the process of disconnection of the space link, the data transmission of the first node will be suspended, and the first oscillation frequency will have a large jitter, and the first converter will be prohibited from working. During the process of recovery of the space link, the data transmission of the first node will work normally, but the first oscillation frequency will continue to jitter for a preset time length, and the first converter will be prohibited from working. After the space link is restored to stability, the data transmission of the first node will work normally, and the first converter will be enabled to work. Similarly, the second node monitors the second oscillation frequency in real time. During the process of disconnection of the space link, the data transmission of the second node will be suspended, and the second oscillation frequency will have a large jitter, and the second converter will be prohibited from working. During the process of recovery of the space link, the data transmission of the second node will work normally, but the second oscillation frequency will continue to jitter for a preset time length, and the second converter will be prohibited from working. After the space link is restored to stability, the data transmission of the second node will work normally, and the second converter will be enabled to work.

[0082] The method for improving ranging accuracy based on laser communication of the embodiment of the present disclosure monitors the clock recovery process of the first node and the second node respectively, and eliminates the ranging data in the case of unstable space link, so as to ensure the ranging accuracy of the ranging technology based on laser communication.

[0083] The method for improving ranging accuracy based on laser communication is further described below through a ranging process of a ranging system based on laser communication in a specific embodiment.

[0084] Figure 5 A schematic diagram of a ranging system for a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0085] like Figure 5As shown, in one example, the first node includes a 1064nm narrow linewidth laser, a 1064nm intensity modulator, a 1064nm power optical amplifier, a first optical fiber DM, a 1072nm low noise optical amplifier, a 1072nm narrow linewidth filter, a first APD detector, and electronics A. The second node includes a 1072nm narrow linewidth laser, a 1072nm intensity modulator, a 1072nm power optical amplifier, a second optical fiber DM, a 1064nm low noise optical amplifier, a 1064nm narrow linewidth filter, a second APD detector, and electronics B.

[0086] Electronics A includes a first modulator, a first clock recovery unit (CDR), a first decoder, a first control unit and a first converter. Electronics B includes a second modulator, a second clock recovery unit (CDR), a second decoder, a second control unit and a second converter.

[0087] in accordance with Figure 5 The ranging system shown in the figure is set up, each electronic device is powered and initialized to work, and the satellite telescope of the first node and the ground telescope of the second node are aimed and tracked. Due to the influence of atmospheric turbulence changes, telescope tracking jitter and space link distance changes, the space link communication will be repeatedly disconnected and reconnected.

[0088] A 1064nm narrow linewidth laser is used to output a 1064nm laser, and the second communication data and the second sending time are obtained through electronics A. The second communication data is modulated on the 1064nm laser through a 1064nm intensity modulator to obtain a 1064nm modulated laser, and the 1064nm modulated laser is amplified by a 1064nm power optical amplifier, and the first optical signal is obtained through modulation of the first optical fiber DM. The first optical signal enters the space link through the satellite telescope. A 1072nm narrow linewidth laser is used to output a 1072nm laser, and the first communication data and the first sending time are obtained through electronics B. The first communication data is modulated on the 1072nm laser through a 1072nm intensity modulator to obtain a 1072nm modulated laser, and the 1072nm modulated laser is amplified by a 1072nm power optical amplifier, and the second optical signal is obtained through modulation of the second optical fiber DM. The second optical signal enters the space link through the ground telescope.

[0089] The second optical signal is obtained from the space link through the first optical fiber DM, and after being processed by a 1072nm low-noise optical amplifier and a 1072nm narrow linewidth filter, the first APD detector detects the photons of the processed second optical signal to obtain the first communication data. The first communication data is decoded by electronics A and the first receiving time when the space link is stable is obtained by monitoring the space link. The first optical signal is obtained from the space link through the second optical fiber DM, and after being processed by a 1064nm low-noise optical amplifier and a 1064nm narrow linewidth filter, the second APD detector detects the photons of the processed first optical signal to obtain the second communication data. The second communication data is decoded by electronics B and the second receiving time when the space link is stable is obtained by monitoring the space link.

[0090] The distance between the first node and the second node is calculated through a set of a first sending time, a first receiving time, a second sending time and a second receiving time.

[0091] Finally, the distance measurement data is exported and the power of each electronic device is turned off.

[0092] The following experimental verification is carried out using a ranging system that does not use the method for improving ranging accuracy based on laser communication and a ranging system that uses the method for improving ranging accuracy based on laser communication. The technical effect of the method for improving ranging accuracy based on laser communication is further illustrated through the experimental results.

[0093] Figure 6 A schematic diagram of ranging results of a ranging system according to an embodiment of the present disclosure that does not use a method for improving ranging accuracy based on laser communication is shown schematically.

[0094] like Figure 6 As shown, after the distance measurement calculation of a large number of sampling points, there are many obvious erroneous data in the distance measurement results, which may cause the deviation of the distance measurement results to reach several centimeters to tens of centimeters.

[0095] Figure 7 A schematic diagram of ranging results of adding monitoring signals to a ranging system according to an embodiment of the present disclosure that does not use the method for improving ranging accuracy based on laser communication is schematically shown.

[0096] like Figure 7 As shown, the first monitoring signal (monitoring signal 1) of the first node and the second monitoring signal (monitoring signal 2) of the second node are added to the ranging result, and the two monitoring signals are aligned with the ranging result of each sampling point. The positions of the two monitoring signals completely match the positions where the erroneous data occurs. The monitoring signals can well indicate the position where the erroneous data occurs. Figure 7 As shown, in the distance measurement data with a duration of 30 seconds, the accuracy of the distance measurement results is about 8.2mm (standard deviation).

[0097] Figure 8 A schematic diagram of the ranging results of a ranging system according to a method for improving ranging accuracy based on laser communication according to an embodiment of the present disclosure is schematically shown.

[0098] like Figure 8 As shown, the erroneous data is eliminated according to the first monitoring signal and the second monitoring signal. In the distance measurement data with a duration of 30 seconds, there is no obvious erroneous data, and the accuracy of the distance measurement result is about 7.1mm (standard deviation).

[0099] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for improving ranging accuracy based on laser communication, characterized in that: Applied to a first node, the first node comprises a first detector, a first clock recovery unit, a first control unit, a first decoder and a first converter, the first clock recovery unit comprises a first oscillator and a first frequency discriminator, the method comprises: Obtaining first communication data including a first synchronization pulse from a second node through the first detector; Adjusting the first oscillation frequency of the first oscillator by the first clock recovery unit until the first oscillator has the same frequency as the first communication data to obtain a first decoding clock; The first oscillation frequency is monitored by the first frequency discriminator to obtain a first monitoring signal; Based on the first decoding clock, decoding the first communication data by the first decoder to obtain the first synchronization pulse; Based on the first monitoring signal, prohibiting or enabling the first converter from operating through the first control unit; The first synchronization pulse is converted into a digital signal by the first converter to obtain a first receiving time; the first receiving time is used for ranging calculation.

2. The method for improving ranging accuracy according to claim 1, characterized in that: The disabling or enabling the first converter to operate based on the first monitoring signal through the first control unit includes: When the first monitoring signal does not meet a preset condition, prohibiting the first converter from operating; When the first monitoring signal satisfies the preset condition, enabling the first converter to operate; The preset condition indicates that the duration during which the first monitoring signal is less than a threshold value is greater than a preset duration.

3. The method for improving ranging accuracy according to claim 1, characterized in that: The step of monitoring the first oscillation frequency by the first frequency discriminator to obtain a first monitoring signal includes: Subtracting the first oscillation frequency from the frequency of the first communication data by the first frequency discriminator to obtain a frequency difference; Based on the frequency difference, the first monitoring signal is obtained.

4. The method for improving ranging accuracy according to claim 1, characterized in that: Applied to the second node, the second node includes a second detector, a second clock recovery unit, a second control unit, a second decoder and a second converter, the second clock recovery unit includes a second oscillator and a second frequency discriminator, and the method further includes: obtaining, by the second detector, second communication data including a second synchronization pulse from the first node; The second oscillation frequency of the second oscillator is adjusted by the second clock recovery unit until it has the same frequency as the second communication data, thereby obtaining a second decoding clock; The second oscillation frequency is monitored by the second frequency discriminator to obtain a second monitoring signal; Based on the second decoding clock, decoding the second communication data by the second decoder to obtain the second synchronization pulse; Based on the second monitoring signal, prohibiting or enabling the second converter from operating through the second control unit; The second synchronization pulse is converted into a digital signal by the second converter to obtain a second receiving time; the second receiving time is used for the ranging calculation.

5. The method for improving ranging accuracy according to claim 4, characterized in that: The method further comprises: Converting the second synchronization pulse into a digital signal by the first converter to obtain a first sending time; Converting the first synchronization pulse into a digital signal by the second converter to obtain a second sending time; Based on a set of the first sending time, the first receiving time, the second sending time and the second receiving time, a distance between the first node and the second node is calculated.

6. The method for improving distance measurement accuracy according to claim 4, characterized in that: The first node further includes a first encoder, the second node further includes a second encoder, and the method further includes: Obtaining the second synchronization pulse and the second communication data through the first encoder; The first synchronization pulse and the first communication data are obtained through the second encoder.

7. The method for improving distance measurement accuracy according to claim 4, characterized in that: The first node further includes a first modulator, the second node further includes a second modulator, and the method further includes: sending the second communication data to the second node through the first modulator; The first communication data is sent to the first node through a second modulator.

8. The method for improving distance measurement accuracy according to claim 3, characterized in that: The first clock recovery unit further includes a phase detector, and the method further includes: Difference is made between the phases of the first oscillation clock and the first communication data by the phase detector to obtain a phase difference; Under the effect of the phase difference and the frequency difference, the first oscillation frequency is adjusted and output by the first oscillator.

9. The method for improving distance measurement accuracy according to claim 8, characterized in that: The first clock recovery unit further includes a first filter, a second filter and a summer, and the method further includes: filtering the phase difference by using the first filter; filtering the frequency difference by the second filter; The filtered phase difference and the filtered frequency difference are summed by the summer to act on the first oscillator.

10. The method for improving distance measurement accuracy according to claim 1, characterized in that: The first node and the second node establish a communication link via a space link. When the space link is disconnected and / or the connection is unstable, the first oscillation frequency jitters; when the space link is stable, the first oscillation frequency is stable.

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