Laser pulse position coding control method, control system, and optical communication equipment

Abstract

The present invention belongs to the technical field of long-distance time transmission of space laser pulses, and discloses a laser pulse position coding control method, control system, and optical communication equipment. By selectively controlling the polarization state of the laser pulse output by the laser, the selected laser pulse is input into the delayed optical path, so as to realize the laser pulse position coding and load the specific optical pulse moment coding information. The present invention encodes the moment information, and through the invented laser pulse modulation coding control technology and device, the moment coding information is loaded into the laser pulse sequence, and then the sequence is sent to the receiving end through the laser emission system, so as to realize the long-distance transmission of the time code information and the time difference measurement and comparison of the long-distance space system. The control accuracy of the present invention reaches the picosecond level. By controlling the multiple round trips of the laser pulse in the delayed optical path, the pulse coding order is increased and the length of the delayed optical path is shortened. The external control optical path involved in the present invention does not affect the working stability of the laser.

Description

Technical Field

[0001] The present invention belongs to the technical field of long-distance time transmission of space laser pulses, and in particular relates to a laser pulse position coding control method, a control system, and optical communication equipment. Background Art

[0002] Laser pulse position coding (PPM) technology is a technology that achieves information encoding and loading of pulse sequences by controlling the interval of laser pulses, that is, the timing position of single or multiple laser pulses in the laser pulse sequence. Laser pulse position modulation technology is widely used in the field of laser communication, including fiber laser communication and space laser communication, with the goal of pursuing communication speed. The modulated pulse sequence is usually generated by direct laser modulation.

[0003] If there is a signal of n bits, PPM technology can load these n bits onto one pulse, and the data information can be read through the relative position of the pulse. This pulse position has 2 n This modulation is repeated every T, so the transmission rate becomes "n / T" (bits / second). Pulse position modulation is widely used in optical communication systems because there is little or no multipath interference problem in optical communication systems.

[0004] In the field of space laser pulse long-distance time transfer technology, the laser pulse is required to be as narrow as possible to improve the accuracy of laser pulse moment measurement. At the same time, the laser single pulse energy is required to be as large as possible to increase the laser transmission distance. This technical field has very high requirements for lasers. Keeping the laser at a stable light output frequency and reducing laser pulse jitter is beneficial to improving the stability and reliability of the laser and the accuracy of time transfer. Especially for high-power narrow pulse lasers, the light output frequency is not allowed to fluctuate over a large range, otherwise it will cause damage. Strict requirements are placed on the pulse timing, which limits the direct modulation of the laser to generate a pulse sequence. This brings technical obstacles to time transfer over long distances, especially in the deep space range of the solar system over hundreds of millions of kilometers.

[0005] At present, the pulse laser used in the space laser pulse long-distance time transfer technology usually has a fixed output laser pulse frequency, and there is a fixed pulse interval between laser pulses. It is impossible to load and transmit time code information, and other technical methods such as microwaves must be used to exchange measurement data.

[0006] Through the above analysis, the problems and defects of the prior art are as follows:

[0007] (1) In the prior art, it is not possible to achieve precise time transmission and time code information transmission through the same laser link.

[0008] (2) In the prior art, the long-distance transmission performance of time code information is poor; moreover, the pulse position cannot be strictly controlled at all times, and the control accuracy is low. The prior art can meet the communication requirements by directly modulating the laser, and does not require high precision of laser pulse timing, and lacks effective control methods.

[0009] (3) The existing technology affects the working stability of the laser and easily causes laser pulse jitter, which affects the laser timing and measurement accuracy.

[0010] The difficulty in solving the above problems and defects is as follows: The difficulty lies in the fast transmission speed of laser pulses, which places high demands on the synchronous laser signal detection and control speed. Pulse position encoding accuracy and high-precision control are relatively difficult.

[0011] The significance of solving the above problems and defects is as follows: the method of the present invention mainly solves the problem of PPM modulation and control of laser pulse sequence outside the laser. According to the needs, the method and control system of the present invention can generate both first-order pulse position coding and multi-order coding. The pulse position delay accuracy is determined by the delay optical path length, and the high-order coding delay interval is an integer multiple of the delay optical path length, which is convenient for accurate measurement and resolution. Summary of the invention

[0012] In order to solve the problems existing in the prior art, the present invention provides a laser pulse position coding control method, a control system, and an optical communication device.

[0013] The present invention is implemented as follows: a laser pulse position coding control method, the laser pulse position coding control method comprising:

[0014] By selecting the polarization state of the laser pulse output by the laser, the selected laser pulse is input into the delayed optical path, so that the laser pulse position encoding is realized to load the specific time information.

[0015] Furthermore, the specific moment information is the moment information of the first laser pulse in the pulse sequence or other user information.

[0016] Furthermore, the laser pulse position encoding control method further comprises:

[0017] In the first step, the laser pulse passes through the first polarizer, enters the pulse modulation coding control optical path, passes through the Faraday isolator and the half-wave plate, the polarization direction is rotated 90°, and is reflected by the second polarizer;

[0018] In the second step, the optical switch composed of a quarter-wave plate and a Pockels cell controls the polarization state of the laser pulse, rotates 90° again, and the laser pulse is reflected by the first total reflection mirror. At the same time, the optical detector detects and monitors the leaked laser pulse.

[0019] In the third step, the laser pulse with the rotated polarization state enters the optical delay optical path composed of the second total reflection mirror, the total reflection mirror and the one-dimensional translation stage; the laser pulse is locked in the delay optical path, and after 1 to n round trips, a path delay is generated each time after a round trip, and the specific delay time is determined by the length of the delay optical path; when the laser pulse reaches the predetermined delay time, the optical switch composed of the quarter wave plate and the Pockels cell is controlled to change the polarization state of the laser pulse again, so that the polarization state is rotated 90°;

[0020] In the fourth step, after the polarization state is rotated 90° in the third step, the laser pulse is reflected by the second polarizer, passes through the half wave plate and the Faraday isolator in the reverse direction, and the polarization state of the laser pulse does not change. The laser pulse is reflected by the first polarizer and enters the subsequent laser transmission optical path.

[0021] Furthermore, in the first step, the Faraday rotator is used in combination with a half wave plate to achieve a 90° rotation of the polarization state of the incident laser pulse.

[0022] Furthermore, in the third step, the optical delay time is determined by the number of round trips and the length of the delayed optical path; the delayed optical path is achieved by increasing the optical path of the laser pulse transmission.

[0023] Furthermore, in the third step, the laser pulse position coding is single-order and multi-order position coding, and the multi-order position coding is determined by the number of round trips of the laser pulse in the delayed optical path; the optical switch frequency is 10Hz-300KHz.

[0024] Furthermore, in the first to fourth steps, the laser pulse is a nanosecond laser pulse, a picosecond laser pulse or a femtosecond laser pulse with a width of 10ns-100fs; the laser pulse wavelength is 532nm, 1064nm or 1550nm; and the laser pulse frequency is 10Hz-300KHz.

[0025] Another object of the present invention is to provide a control system for implementing laser pulse position coding, comprising: a first polarizer;

[0026] The laser pulse emitted by the laser passes through the first polarizer, enters the pulse modulation coding control optical path, passes through the Faraday isolator and the half wave plate, the polarization direction is rotated 90°, and is reflected by the second polarizer;

[0027] The optical switch composed of a quarter-wave plate and a Pockels cell controls the polarization state of the laser pulse, which is rotated 90° again. The laser pulse is reflected by the first total reflection mirror, and at the same time, the optical detector detects and monitors the leaked laser pulse;

[0028] In the non-modulation coding state, the optical switch does not change the polarization state of the laser pulse. After being reflected by the first total reflection mirror, the laser pulse passes through the Faraday isolator and the half-wave plate in the reverse direction, and the polarization direction does not rotate. The outgoing laser pulse is reflected because the polarization direction is perpendicular to the transmission direction of the first polarizer, and enters the next-stage output optical path through the third total reflection mirror;

[0029] For laser pulses that need to be modulated, the optical switch controls the laser pulses to rotate the polarization state by 90°. After being reflected by the first total reflection mirror, the laser pulses enter the optical delay optical path composed of the second total reflection mirror, the total reflection mirror and the one-dimensional translation stage to generate delay coding. The delay time is determined by the optical path difference of the optical path.

[0030] After the delayed encoded laser pulse, the polarization state passes through the first polarizer and is reflected by the third total reflection mirror into the next-stage output optical path.

[0031] Furthermore, the first polarizer and the second polarizer are both Glan prisms, Brewster angle polarizers or thin film polarizers.

[0032] Furthermore, the optical switch is a single crystal Pockels cell or a double crystal Pockels cell; the optical detector is a silicon photodetector, a photomultiplier tube, or an InGaAs detector.

[0033] Another object of the present invention is to provide an optical communication device that implements the laser pulse position coding control method, which is used for long-distance and time-based transmission of laser pulses in remote space.

[0034] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows:

[0035] The invention relates to laser pulse time measurement, and the pulse time information is loaded into the laser beam through modulation coding to generate a laser pulse sequence containing time code information. The invention is used to achieve precise time synchronization and high-precision timing between the free space ground and spacecraft or between spacecraft.

[0036] The device of the present invention can be used in a space laser precision time transfer system. The control system encodes the moment information. Through the laser pulse modulation coding control technology and device of the present invention, the time code coding information is loaded into the laser pulse sequence, and the sequence is sent to the receiving end through the laser emission system, thereby realizing the long-distance transmission of the time code information.

[0037] Moreover, the pulse position timing of the present invention can be strictly controlled, and the control accuracy can reach the picosecond level.

[0038] Through multiple round trip control of laser pulses, the pulse coding order can be further improved and the delay optical path length can be shortened.

[0039] The external control optical path involved in the present invention does not affect the working stability of the laser, and is conducive to reducing the influence of laser pulse jitter on laser time code and measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 It is a flow chart of the laser pulse position encoding control method provided by an embodiment of the present invention.

[0042] Figure 2 It is a schematic diagram of the laser pulse position coding control system provided in Example 1 of the present invention.

[0043] Figure 3 It is a schematic diagram of the laser pulse position coding control system provided in Example 2 of the present invention.

[0044] In the figure: 1. first polarizer; 2. Faraday isolator; 3. half wave plate; 4. second polarizer; 5. quarter wave plate; 6. Pockels cell; 7. first total reflection mirror; 8. photodetector; 9. second total reflection mirror; 10. total reflection mirror and one-dimensional translation stage; 11. third total reflection mirror; 12. laser. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] In the prior art, the long-distance transmission performance of time code information is poor; moreover, the pulse position moment cannot be strictly controlled, and the control accuracy is low.

[0047] The existing technology cannot control the laser pulses back and forth multiple times, and cannot increase the pulse coding order, resulting in the inability to delay the optical path length.

[0048] The existing technology affects the working stability of the laser and easily causes laser pulse jitter, which affects the laser time code and measurement accuracy.

[0049] In view of the problems existing in the prior art, the present invention provides a laser pulse position coding control method, a control system, and an optical communication device. The present invention is described in detail below in conjunction with the accompanying drawings.

[0050] The present invention provides a laser pulse position encoding control method, comprising:

[0051] By selecting the polarization state of the laser pulse output by the laser, the selected laser pulse is input into the delayed optical path, so that the laser pulse position encoding is realized to load the specific time information.

[0052] The specific time information is the time information of the first laser pulse of the pulse sequence or other user information.

[0053] like Figure 1 As shown, in the present invention, the laser pulse position encoding control method further includes:

[0054] S101, the laser pulse passes through the first polarizer, enters the pulse modulation coding control optical path, passes through the Faraday isolator and the half wave plate, the polarization direction is rotated 90°, and is reflected by the second polarizer.

[0055] S102, the optical switch composed of a quarter wave plate and a Pockels cell controls the polarization state of the laser pulse, rotates 90 degrees again, and the laser pulse is reflected by the first total reflection mirror. At the same time, the optical detector detects and monitors the leaked laser pulse.

[0056] S103, the laser pulse with its polarization state rotated enters the optical delay optical path composed of a second total reflection mirror, a total reflection mirror and a one-dimensional translation stage; the laser pulse is locked in the delay optical path, and after 1 to n round trips; when the laser pulse reaches a predetermined delay time, the optical switch composed of a quarter wave plate and a Pockels cell is controlled to change the polarization state of the laser pulse again, so that the polarization state is rotated 90°.

[0057] S104, after the polarization state is rotated 90° in step S103, the laser pulse is reflected by the second polarizer, passes through the half wave plate and the Faraday isolator in the reverse direction, and the polarization state of the laser pulse does not change. The laser pulse is reflected by the first polarizer and enters the subsequent laser transmission optical path.

[0058] In the present invention, a laser pulse position coding control system is provided, in which the laser pulse is a nanosecond laser pulse, a picosecond laser pulse or a femtosecond laser pulse with a width of 10ns-100fs; the laser pulse wavelength is 532nm, 1064nm or 1550 nanometers; and the laser pulse frequency is 10Hz-300KHz.

[0059] The polarizer is a Glan prism, a Brewster angle polarizer or a thin film polarizer.

[0060] The delayed optical path is realized by increasing the optical distance of laser pulse transmission, and the laser pulse can travel back and forth on the delayed optical path for multiple times.

[0061] The Faraday rotator is used in combination with a half wave plate to achieve a 90° rotation of the polarization state of the incident laser pulse.

[0062] The optical switch is a single crystal Pockels cell or a double crystal Pockels cell. The optical detector is a silicon photodetector, a photomultiplier tube, or an InGaAs detector. The laser pulse position coding can be single-order or multi-order position coding, and the multi-order position coding is determined by the number of round trips of the laser pulse in the delayed optical path.

[0063] The specific time information is the time information of the first laser pulse of the pulse sequence or other user information. The optical switch frequency is 10 Hz-300 KHz.

[0064] The present invention will be further described below in conjunction with specific embodiments.

[0065] Example 1

[0066] like Figure 2 As shown, in the laser pulse position coding control system provided by the present invention, the laser pulse emitted by the laser passes through the first polarizer 1, enters the pulse modulation coding control optical path, passes through the Faraday isolator 2 and the half wave plate 3, and the polarization direction is rotated 90°, so it is reflected by the second polarizer 4. At this time, the optical switch composed of the quarter wave plate 5 and the Pockels cell 6 controls the polarization state of the laser pulse, and rotates 90° again. The laser pulse is reflected by the first total reflection mirror 7, and the optical detector 8 detects and monitors the leaked laser pulse. In the non-modulation coding state, the optical switch does not change the polarization state of the laser pulse. After the laser pulse is reflected by the first total reflection mirror 7, it passes through the Faraday isolator 2 and the half wave plate 3 in the reverse direction, and the polarization direction does not rotate. The emitted laser pulse is reflected because the polarization direction is perpendicular to the transmission direction of the first polarizer 1, and enters the next-level output optical path through the third total reflection mirror 11. For laser pulses that need to be modulated, the optical switch controls the laser pulses to rotate their polarization state by 90°. At this time, after the laser pulses are reflected by the first total reflection mirror 7, they enter the optical delay optical path composed of the second total reflection mirror 9, the total reflection mirror and the one-dimensional translation stage 10, generating delay coding, and the delay time is determined by the optical path difference of the optical path. Enter the next level output optical path.

[0067] This scheme simplifies control, but has fewer coding levels and less information loading.

[0068] In the laser pulse position coding control method of the present invention, the laser pulse first passes through the first polarizer 1, enters the pulse modulation coding control optical path, passes through the Faraday isolator 2 and the half wave plate 3, and the polarization direction is rotated 90°, so it is reflected by the second polarizer 4 polarizer. At this time, the optical switch composed of the quarter wave plate 5 and the Pockels cell 6 controls the polarization state of the laser pulse, rotates 90° again, and the laser pulse is reflected by the first total reflection mirror 7. At the same time, the optical detector 8 detects and monitors the leaked laser pulse. After that, because the polarization state of the laser pulse has been rotated, the pulse meets the polarizer transmission condition, and the laser pulse can enter the optical delay optical path composed of the second total reflection mirror 9, the total reflection mirror and the one-dimensional translation stage 10. At this time, the laser pulse will be locked in the delay optical path, and after 1 to n round trips, the optical delay time is determined by the number of round trips and the length of the delay optical path. When the laser pulse reaches the predetermined delay time, the optical switch composed of the quarter-wave plate 5 and the Pockels cell 6 can be controlled to change the polarization state of the laser pulse again and rotate it 90°. At this time, the laser pulse will be reflected by the second polarizer 4 and pass through the half-wave plate 3 and the Faraday isolator 2 in the reverse direction. The polarization state of the laser pulse will not change, and the laser pulse will be reflected by the first polarizer 1, thereby entering the subsequent laser transmission optical path.

[0069] Example 2

[0070] like Figure 3 As shown, in the laser pulse position coding control system provided by the present invention, the laser pulse emitted by the laser 12 passes through the first polarizer 1, enters the pulse modulation coding control optical path, passes through the Faraday isolator 2 and the half wave plate 3, and the polarization direction is rotated 90°, so it is reflected by the second polarizer 4. At this time, the optical switch composed of the quarter wave plate 5 and the Pockels cell 6 controls the polarization state of the laser pulse, and rotates 90° again. The laser pulse is reflected by the first total reflection mirror 7, and the optical detector 8 detects and monitors the leaked laser pulse. In the non-modulation coding state, the optical switch does not change the polarization state of the laser pulse. After the laser pulse is reflected by the first total reflection mirror 7, it passes through the Faraday isolator 2 and the half wave plate 3 in the reverse direction, and the polarization direction does not rotate. The emitted laser pulse is reflected because the polarization direction is perpendicular to the transmission direction of the first polarizer 1, and enters the next-level output optical path through the third total reflection mirror 11. For laser pulses that need to be modulated, the optical switch controls the laser pulses to rotate their polarization state by 90°. At this time, after the laser pulses are reflected by the first total reflection mirror 7, they will enter the optical delay optical path composed of the second total reflection mirror 9, the total reflection mirror and the one-dimensional translation stage 10, and generate delay coding. The delay time is determined by the optical path difference of the optical path. The polarization state of the laser pulses that have undergone delay coding can pass through the first polarizer 1 and be reflected by the third total reflection mirror 11 to enter the next-level output optical path. This solution simplifies the control, but the number of coding levels is small and the amount of information loaded is small.

[0071] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A laser pulse position encoding control method, characterized in that: The laser pulse position coding control method comprises: selectively controlling the polarization state of the laser pulse output by the laser, inputting the selected laser pulse into the delayed optical path, and realizing the laser pulse position coding to load the specific time information; The laser pulse position encoding control method further comprises: In the first step, the laser pulse passes through the first polarizer, enters the pulse modulation coding control optical path, passes through the Faraday isolator and the half-wave plate, the polarization direction is rotated 90°, and is reflected by the second polarizer; In the second step, the optical switch composed of a quarter-wave plate and a Pockels cell controls the polarization state of the laser pulse, rotates 90° again, and the laser pulse is reflected by the first total reflection mirror. At the same time, the optical detector detects and monitors the leaked laser pulse. In the third step, the laser pulse with its polarization state rotated enters an optical delay optical path composed of a second total reflection mirror, a total reflection mirror and a one-dimensional translation stage; the laser pulse is locked in the delay optical path and goes back and forth 1 to n times; when the laser pulse reaches a predetermined delay time, the optical switch composed of a quarter wave plate and a Pockels cell is controlled to change the polarization state of the laser pulse again, so that the polarization state is rotated 90°; In the fourth step, after the polarization state is rotated 90° in the third step, the laser pulse is reflected by the second polarizer, passes through the half wave plate and the Faraday isolator in the reverse direction, and the polarization state of the laser pulse does not change. The laser pulse is reflected by the first polarizer and enters the subsequent laser transmission optical path.

2. The laser pulse position encoding control method according to claim 1, characterized in that: The specific time information is the time information of the first laser pulse of the pulse sequence or other user information.

3. The laser pulse position encoding control method according to claim 1, characterized in that: In the first step, a Faraday rotator is used in combination with a half wave plate to achieve a 90° rotation of the polarization state of the incident laser pulse.

4. The laser pulse position encoding control method according to claim 3, characterized in that: In the third step, the optical delay time is determined by the number of round trips and the length of the delayed optical path; the delayed optical path is achieved by increasing the optical path of the laser pulse transmission.

5. The laser pulse position encoding control method according to claim 3, characterized in that: In the third step, the laser pulse position coding is single-order and multi-order position coding, and the multi-order position coding is determined by the number of round trips of the laser pulse in the delayed optical path; the optical switch frequency is 10Hz-300KHz.

6. The laser pulse position encoding control method according to claim 1, characterized in that: In the first to fourth steps, the laser pulse is a nanosecond laser pulse, a picosecond laser pulse or a femtosecond laser pulse with a width of 10ns-100fs; the laser pulse wavelength is 532nm, 1064nm or 1550nm; and the laser pulse frequency is 10Hz-300KHz.

7. A laser pulse position coding control system for implementing the laser pulse position coding control method according to any one of claims 1 to 6, characterized in that: The laser pulse position coding control system comprises: a first polarizer; The laser pulse emitted by the laser passes through the first polarizer, enters the pulse modulation coding control optical path, passes through the Faraday isolator and the half wave plate, the polarization direction is rotated 90°, and is reflected by the second polarizer; The optical switch composed of a quarter-wave plate and a Pockels cell controls the polarization state of the laser pulse, which is rotated 90° again. The laser pulse is reflected by the first total reflection mirror, and at the same time, the optical detector detects and monitors the leaked laser pulse; In the non-modulation coding state, the optical switch does not change the polarization state of the laser pulse. After being reflected by the first total reflection mirror, the laser pulse passes through the Faraday isolator and the half-wave plate in the reverse direction, and the polarization direction does not rotate. The outgoing laser pulse is reflected because the polarization direction is perpendicular to the transmission direction of the first polarizer, and enters the next-stage output optical path through the third total reflection mirror; For laser pulses that need to be modulated, the optical switch controls the laser pulses to rotate the polarization state by 90°. After being reflected by the first total reflection mirror, the laser pulses enter the optical delay optical path composed of the second total reflection mirror, the total reflection mirror and the one-dimensional translation stage to generate delay coding. The delay time is determined by the optical path difference of the optical path. After the delayed encoded laser pulse, the polarization state passes through the first polarizer and is reflected by the third total reflection mirror into the next-stage output optical path.

8. The laser pulse position coding control system according to claim 7, characterized in that: The first polarizer and the second polarizer are both Glan prisms, Brewster angle polarizers or thin film polarizers; The optical switch is a single crystal Pockels cell or a double crystal Pockels cell; the optical detector is a silicon photodetector, a photomultiplier tube or an InGaAs detector.

9. An optical communication device implementing the laser pulse position coding control method according to any one of claims 1 to 6.

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