Path integral differential absorption laser radar signal enhancement system and method

Abstract

The invention discloses a path integral differential absorption laser radar signal enhancement system, which comprises an optical switch, an acoustic optical modulator, an erbium-doped optical fiber amplifier, a telescope, a temperature control filter, a single-photon detector and a signal acquisition card which are connected in sequence, the signal acquisition card is connected with the second laser through a power feedback control module or an error signal calculation processing module, and the temperature control filter is located in a temperature control box; the invention also discloses a signal enhancement method, which realizes dual-channel total gain consistency control by dynamically adjusting laser power of a non-absorption wavelength channel and compensating signal loss caused by filter transmittance difference, and locks a filter passband at an absorption wavelength peak value to maximize a main channel signal and improve the gain consistency of the main channel. The filter transmittance loss of the secondary channel is compensated through power regulation, and the performance compromise limitation caused by the fact that dual-wavelength passbands need to be considered in a traditional scheme is broken through.

Description

Technical Field

[0001] This invention belongs to the technical field of lidar atmospheric measurement equipment, and relates to a path integral differential absorption lidar signal enhancement system. This invention also relates to a signal enhancement method. Background Technology

[0002] With the continuous development of laser technology, lidar has been widely used in atmospheric environment detection. Among them, path integral differential absorption lidar (IPDA), as a remote sensing technology for large-scale gas column concentration, achieves high-precision monitoring of greenhouse gases such as CO2 and CH4 in the atmosphere by measuring the path integral absorption signal after laser reflection from hard targets such as clouds and the ground. Compared with traditional range-resolved differential absorption lidar (DIAL), path integral lidar only obtains gas profile concentration. It sacrifices range resolution for large-scale monitoring adaptability, high signal-to-noise ratio, and low system complexity, making it more suitable for rapid detection of wide-area gas concentrations on airborne and spaceborne platforms. It has become one of the core means of global carbon cycle monitoring.

[0003] In traditional path integral lidar systems, the receiver typically uses a narrowband filter to suppress strong background light noise in order to balance... and The echo signal received by the channel, the filter passband center is usually set at and However, this design causes the peak wavelength of the filter transmittance curve to fail to align with the laser center wavelengths of the on and off channels, resulting in a mismatch between the spectral energy distribution of the dual-channel echo signal and the maximum transmission region of the filter. This significantly reduces the signal transmittance, thereby weakening the system's signal-to-noise ratio and effective detection range. Therefore, enhancing the echo signal received by the dual channels to improve the detection range poses new requirements for the development of path integral differential absorption lidar. To improve the signal strength of path integral lidar, existing technologies mainly adopt the following solutions: the method of adjusting only the laser emission power based on the laser reflection device cannot maximize the consistency of the on / off channel echo signal; the method based on fixed gain and mechanically tuned filters cannot dynamically adjust the gain according to the signal strength, and will face problems such as slow tuning speed, large size, and limited accuracy; by introducing accumulated optical depth and molecular number density error, the upper limit of maximum saturation and the lower limit of minimum detection are simulated and determined. A method is proposed to select the absorption line between the upper limit of maximum saturation and the lower limit of minimum detection of gas concentration by using molecular number density error. Different absorption lines are used under different environmental concentrations. This method can be used to detect gas concentrations over a wide dynamic range, but it introduces certain errors.

[0004] In summary, existing path integral lidar systems face a dilemma in filter design and power allocation: if the filter passband is fixed at... Wavelength, then The channel signal is significantly attenuated due to low transmittance; if dual wavelengths are considered at the same time, the performance of both channels deteriorates simultaneously. How to achieve dynamic balance of dual-channel signals without introducing complex hardware has become a key challenge to improve the practicality of path integration lidar. Summary of the Invention

[0005] The purpose of this invention is to provide a path integral differential absorption lidar signal enhancement system, which solves the problem of synchronous attenuation caused by the passband offset of the shared filter on the dual-wavelength signal at the receiving end in the existing traditional system.

[0006] A second objective of this invention is to provide a signal enhancement method.

[0007] The first technical solution adopted in this invention is a path integral differential absorption lidar signal enhancement system, comprising an optical switch, an acousto-optic modulator, an erbium-doped fiber amplifier, a telescope, a temperature-controlled filter, a single-photon detector, and a signal acquisition card connected in sequence. The optical switch is connected to a first laser and a second laser. The signal acquisition card and the second laser are connected through a power feedback control module or an error signal calculation and processing module. The temperature-controlled filter is located inside a temperature-controlled chamber.

[0008] The first technical solution of this invention is also characterized by: The power feedback control module is a computer.

[0009] The error signal calculation and processing module includes a PID controller, a digital-to-analog converter, and a drive circuit connected in sequence. The PID controller is connected to the signal acquisition card, and the drive circuit is connected to the second laser.

[0010] The second technical solution adopted in this invention is a signal enhancement method, comprising the following steps: Step 1: The first and second lasers alternately emit continuous light, which passes through an optical switch, an acousto-optic modulator, an erbium-doped fiber amplifier, and a telescope before being emitted into the atmosphere. The telescope receives the atmospheric echo signal and filters out the background light using a temperature-controlled filter. The transmittance of the temperature-controlled filter is then fixed at a certain value. At wavelength; Step 2: The computer calculates the ratio of the number of photons reflected by the dual-channel mirror in real time, multiplies the ratio of the number of photons reflected by the dual-channel mirror by the output power of the second laser, and adjusts the output power of the second laser.

[0011] The second technical solution of the present invention is further characterized by: In step 1, the continuous light is switched by an optical switch and then converted into pulsed light by an acousto-optic modulator. lon and l off The pulsed light is amplified by an erbium-doped fiber amplifier and then alternately emitted into the atmosphere through a telescope; the transmittance of the temperature-controlled filter is fixed at a certain value by controlling the temperature of the temperature-controlled chamber. At wavelength.

[0012] Step 2 is performed as follows: Step 2.1: The atmospheric echo signal after background light filtering is detected using a single-photon detector, and the signal acquisition card collects the number of specularly reflected photons from the dual channels. , ; Step 2.2, the computer calculates the ratio of the number of photons reflected from the dual-channel mirror. Perform calculations, Transmitted to the second laser, and The output power of the second laser is dynamically adjusted by multiplying it by a proportionality coefficient, so that the total gain of the dual channels satisfies the following: ,in P on Absorption wavelength l on The output power of the laser, in W; P off Absorption wavelength l off The output power of a laser, measured in W; T on and T off The temperature control filter is respectively in l on and l off The transmittance at the point, with a value ranging from 0 to 1, ensures that the signal strength received by the single-photon detector is always below the saturation threshold.

[0013] The third technical solution adopted in this invention is a signal enhancement method, comprising the following steps: Step a: The first and second lasers alternately emit continuous light, which passes through an optical switch, an acousto-optic modulator, an erbium-doped fiber amplifier, and a telescope before being emitted into the atmosphere. The telescope receives the atmospheric echo signal and filters out the background light using a temperature-controlled filter. The transmittance of the temperature-controlled filter is then fixed at a certain value. At wavelength; Step b: The PID controller calculates the error signal and controls the output, converting the output into a voltage signal and sending it to the drive circuit. The drive circuit adjusts the drive current of the second laser according to the voltage signal.

[0014] The third technical solution of this invention is further characterized by: Step b is to be performed as follows: Step b.1: The atmospheric echo signal after background light filtering is detected using a single-photon detector, and the signal acquisition card collects the number of specularly reflected photons from the dual channels. , ; Step b.2, the PID controller calculates the error signal in real time. e ( t ):

[0015] t express t At that moment, when At that time, the dual-channel signals were balanced. e ( t When 0 ≠ 0, the PID controller adjusts its output to make the PID controller output... satisfy:

[0016] in, , , The parameters are adjustable; the output power of the second laser is dynamically adjusted via a digital-to-analog converter and a drive circuit until... e ( t → 0, achieving dual-channel balance; Step b.3, the digital-to-analog converter will The signal is converted into a voltage signal and output to the driving circuit. The driving circuit adjusts the driving current of the second laser according to the received signal to ensure that its output power meets the following requirements: .

[0017] Proportional Term The initial adjustment range is determined in response to the current error; the integral term... Eliminate historical error accumulation to ensure steady-state accuracy; differential term Predict the trend of error changes and suppress over-adjustment and oscillation.

[0018] When the error signal is input to the PID controller, a power regulation command is generated, making... The total gain of the channel satisfies G off : Real-time tracking The total gain of the channel satisfies G on : .

[0019] The beneficial effects of this invention are: This invention compensates for signal loss caused by differences in transmittance of the temperature-controlled filter by dynamically adjusting the laser power of the non-absorption wavelength channel, achieving consistent overall gain control across both channels. Based on the direct proportional adjustment of the ratio of specular reflection photons to the transmittance parameter, it rapidly balances signal intensity. Furthermore, it introduces PID closed-loop control, using real-time error signal calculation and integral-derivative compensation to achieve higher-precision dynamic matching in complex environments. By locking the passband of the temperature-controlled filter to the peak of the absorption wavelength, it maximizes the main channel signal while compensating for the transmittance loss of the secondary channel's temperature-controlled filter through power adjustment. This overcomes the performance trade-offs imposed by traditional solutions that require balancing dual-wavelength passbands, significantly improving the system's signal-to-noise ratio and detection range. It provides a solution that balances flexibility and stability for atmospheric trace gas path integral monitoring. Signal loss due to reduced transmittance of the temperature-controlled filter in the channel can be mitigated by improving... The power compensation of the channel for its low transmittance filter can achieve... and By unifying the total gain of the two channels and balancing the total gain, the signal strength difference between the channels can be eliminated, the echo signal strength and signal-to-noise ratio can be improved, and the detection range of the lidar can be increased. Attached Figure Description

[0020] Figure 1 The structure of the path integral differential absorption lidar signal enhancement system of the present invention is shown below. Figure one ; Figure 2 The signal enhancement method flow of the present invention Figure one ; Figure 3 The structure of the path integral differential absorption lidar signal enhancement system of the present invention is shown below. Figure 2 ; Figure 4 The signal enhancement method flow of the present invention Figure 2 ; Figure 5 This is a structural diagram of the driving circuit in this invention.

[0021] In the diagram, 1. First laser, 2. Second laser, 3. Optical switch, 4. Acousto-optic modulator, 5. Erbium-doped fiber amplifier, 6. Telescope, 7. Temperature control box, 8. Temperature control filter, 9. Single-photon detector, 10. Signal acquisition card, 11. Power feedback control module, 111. Computer, 12. Error signal calculation and processing module, 121. PID controller, 122. Digital-to-analog converter, 123. Drive circuit. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Path integral differential absorption lidar signal enhancement system, refer to Figure 1 The system includes, in sequence, an optical switch 3, an acousto-optic modulator 4, an erbium-doped fiber amplifier 5, a telescope 6, a temperature-controlled filter 8, a single-photon detector 9, and a signal acquisition card 10. The optical switch 3 is connected to a first laser 1 and a second laser 2. The signal acquisition card 10 and the second laser 2 are connected via a power feedback control module 11 or an error signal calculation and processing module 12. The temperature-controlled filter 8 is located inside a temperature-controlled box 7. The power feedback control module 11 is a computer 111. (Refer to...) Figure 3 The error signal calculation and processing module 12 includes a PID controller 121, a digital-to-analog converter 122, and a drive circuit 123 connected in sequence. The PID controller 121 is connected to the signal acquisition card 10, and the drive circuit 123 is connected to the second laser 2.

[0024] The temperature-controlled filter 8 is an adjustable narrowband fiber optic filter. Its core function is to adjust the center wavelength through temperature control, and the adjustment range can cover the wavelength range required by the system. This feature allows it to meet the requirement of locking the passband at the absorption wavelength peak. The center wavelength of the temperature-controlled filter 8 changes with temperature. Therefore, when using the temperature-controlled filter 8, it is necessary to optimize the selection for the temperature corresponding to the required center wavelength. The performance of the temperature-controlled filter 8 should be tested under multiple temperature settings to determine its optimal operating temperature. At this temperature, the temperature-controlled filter 8 exhibits the best performance, ensuring that its center wavelength accurately matches the absorption wavelength peak required by the system, thereby maximizing the reception of the main channel signal. l on The transmittance reached its peak and for l on Background noise in the receiving channel is filtered out to the maximum extent possible; before actual measurement, the temperature of the temperature control filter 8 is adjusted via the temperature control box 7 to ensure... l on The transmittance reaches its peak, maintaining the temperature of the temperature control chamber 7 at that calibration point, ensuring that the passband of the temperature control filter 8 is always locked at [value missing]. l on Absorption peak.

[0025] The signal enhancement method includes the following steps: Step 1: The first laser 1 and the second laser 2 alternately emit continuous light. After being switched by the optical switch 3, the continuous light is converted into pulsed light by the acousto-optic modulator 4. l on and l off The pulsed light is amplified by the erbium-doped fiber amplifier 5 and then alternately emitted into the atmosphere through the telescope 6. The telescope 6 receives the atmospheric echo signal and filters out the background light through the temperature-controlled filter 8. The transmittance of the temperature-controlled filter 8 is fixed by controlling the temperature of the temperature-controlled chamber 7. At wavelength, making The number of echo photons in the receiving channel is maximized; at this point, Transmittance of the receiving channel ; Step 2: The atmospheric echo signal after background light filtering is detected by single-photon detector 9, and the signal acquisition card 10 acquires the number of specularly reflected photons in the dual channels. , Computer 111 dual-channel specular reflection photon ratio Perform calculations, Transmitted to the second laser 2, and The output power of the second laser 2 is dynamically adjusted by multiplying it by a proportionality coefficient, so that the total gain of the dual channels satisfies the following: ,in P on Absorption wavelength l on The output power of the laser, in W; P off Absorption wavelength l off The output power of a laser, measured in W; T on and T off Temperature control filter 8 l on and l off The transmittance at the point is in the range of 0-1; by controlling the incident photon rate to be less than the maximum linear count rate of the single-photon detector 9, the signal strength received by the single-photon detector 9 is always kept below the saturation threshold.

[0026] Compensation logic: due to T on > T off (8 pairs of temperature control filters) l on (Higher transmittance) requires improvement l off The transmission power is such that the intensity of the two channel signals is consistent at the single-photon detector 9. In real-time measurement, the transmittance of the temperature control filter 8 cannot be measured in real time, but the number of mirror-reflected photons can be obtained in real time. The ratio of the number of mirror-reflected photons already includes the influence of the transmittance difference. Therefore, the power of the laser can be directly proportionally adjusted based on the ratio of the number of mirror-reflected photons.

[0027] The signal enhancement method includes the following steps: Step a: The first laser 1 and the second laser 2 alternately emit continuous light, which passes through the optical switch 3, acousto-optic modulator 4, erbium-doped fiber amplifier 5, and telescope 6 before being emitted into the atmosphere. The telescope 6 receives the atmospheric echo signal and filters out the background light through the temperature-controlled filter 8, fixing the transmittance of the temperature-controlled filter 8 at a certain value. At wavelength; Step b: The atmospheric echo signal after background light filtering is detected by single-photon detector 9, and the signal acquisition card 10 acquires the number of specularly reflected photons from the dual channels. , PID controller 121 calculates error signals in real time. e ( t ):

[0028] t express t At any given moment, the error signal directly reflects the degree of imbalance in the dual-channel signal strength. When the error signal is input to the PID controller 121, a power adjustment command is generated to make... The total gain of the channel satisfies G off : Real-time tracking The total gain of the channel satisfies G on : ,when At that time, the dual-channel signals were balanced. e ( t When ) ≠ 0, the PID controller 121 adjusts its output, causing the PID controller 121 to output satisfy:

[0029] in, , , For adjustable parameters, the proportional term The initial adjustment range is determined in response to the current error; the integral term... Eliminate historical error accumulation to ensure steady-state accuracy; differential term Predicting error trends and suppressing over-adjustment and oscillation; dynamically adjusting the output power of the second laser 2 via the digital-to-analog converter 122 and the drive circuit 123 until... e ( t → 0, achieving dual-channel balance; the digital-to-analog converter 122 will The signal is converted into a voltage signal and output to the drive circuit 123. The drive circuit 123 adjusts the drive current of the second laser 2 according to the received signal to ensure that its output power meets the following requirements: .

[0030] First, the signal acquisition card 10 acquires the dual-channel signals output by the single-photon detector 9 in real time and transmits these signals to the PID controller 121. The core function of the PID controller 121 is to compare the preset target value (such as the signal strength ratio when the total gain of the two channels is consistent) with the actual signal value input from the signal acquisition card 10, and calculate the error signal between the two. This error signal directly reflects the deviation between the current output power of the second laser 2 and the ideal power. If the actual signal strength is lower than the target value, the error signal is positive, indicating that the power needs to be increased; if the actual signal strength is higher than the target value, the error signal is negative, indicating that the power needs to be reduced. Subsequently, the PID controller 121 performs proportional (P), integral (I), and derivative (D) calculations on the error signal. The PID controller directly outputs the adjustment amount based on the error magnitude, quickly responding to deviations. The integral term eliminates long-term steady-state errors, ensuring the system ultimately reaches the target value. The derivative term predicts the adjustment trend based on the error rate of change, avoiding overshoot or oscillation. The adjustment signal after PID calculation is still a digital signal, which needs to be converted into an analog voltage signal by a digital-to-analog converter 122. This conversion process transforms the digital adjustment command into a voltage form recognizable by the drive circuit. The magnitude of the voltage signal corresponds to the required power adjustment. The entire signal transmission chain starts with the PID controller 121 outputting a digital error signal to the digital-to-analog converter 122, which then converts the digital signal into an analog voltage signal and transmits it to the drive circuit 123. Figure 5The driving circuit 123 is a constant current driving source for a laser diode. This type of laser driving circuit is commonly used in the field, and its basic structure and working principle are existing technologies. This invention does not improve its structure but only utilizes its existing characteristics to drive and control the second laser 2 in conjunction with the digital-to-analog converter 122. It includes a voltage input interface, a voltage-to-current conversion unit, and a laser temperature control module. The voltage input interface receives the analog voltage signal from the digital-to-analog converter 122. After receiving the analog voltage signal output by the digital-to-analog converter 122, the driving circuit 123 converts the voltage signal into a driving current at a fixed ratio through its internal voltage-to-current conversion unit. (If PID control...) The device 121 calculates the power required to be increased, and the voltage signal output by the digital-to-analog converter 122 is enhanced. The drive circuit 123 will then increase the output current accordingly. This current is injected into the second laser 2 through the constant current interface. Since the output power of the second laser 2 is positively correlated with the injected current in its linear operating range, the change in current will directly lead to the real-time change of the output optical power. When the current increases, the carrier concentration increases, stimulated emission is enhanced, and the power increases. When the current decreases, the power decreases accordingly. Finally, the second laser 2 outputs adjustable optical power according to the magnitude of the drive current, thereby realizing the regulation of the output power of the second laser 2. The laser is then re-emitted into the atmosphere to complete the gas measurement. The end-to-end signal response meets the requirements of rapid dynamic adjustment.

[0031] Through the process of "signal acquisition card 10 real-time feedback - PID controller 121 operation and adjustment - digital-to-analog converter 122 signal conversion - drive circuit 123 current regulation - second laser 2 power response", the system can continuously monitor the signal deviation and dynamically adjust the power of the second laser 2, realize real-time and high-precision power regulation, ensure that the total gain of the dual channels remains consistent, and improve the detection stability and signal-to-noise ratio of the lidar.

[0032] Example 1: The path integral differential absorption lidar signal enhancement system includes an optical switch 3, an acousto-optic modulator 4, an erbium-doped fiber amplifier 5, a telescope 6, a temperature control filter 8, a single-photon detector 9, and a signal acquisition card 10 connected in sequence. The optical switch 3 is connected to a first laser 1 and a second laser 2. The signal acquisition card 10 and the second laser 2 are connected through a computer 111. The temperature control filter 8 is located inside a temperature control box 7.

[0033] Example 2: The path integral differential absorption lidar signal enhancement system includes an optical switch 3, an acousto-optic modulator 4, an erbium-doped fiber amplifier 5, a telescope 6, a temperature-controlled filter 8, a single-photon detector 9, and a signal acquisition card 10 connected in sequence. The optical switch 3 is connected to a first laser 1 and a second laser 2. The signal acquisition card 10 and the second laser 2 are connected through an error signal calculation and processing module 12. The temperature-controlled filter 8 is located inside a temperature-controlled box 7. The error signal calculation and processing module 12 includes a PID controller 121, a digital-to-analog converter 122, and a drive circuit 123 connected in sequence. The PID controller 121 is connected to the signal acquisition card 10, and the drive circuit 123 is connected to the second laser 2.

[0034] Example 3: The signal enhancement method includes the following steps: Step 1: The first laser 1 and the second laser 2 alternately emit continuous light, which passes through the optical switch 3, acousto-optic modulator 4, erbium-doped fiber amplifier 5, and telescope 6 before being emitted into the atmosphere. The telescope 6 receives the atmospheric echo signal and filters out the background light through a temperature-controlled filter 8, fixing the transmittance of the temperature-controlled filter 8 at a certain value. At wavelength; Step 2: The atmospheric echo signal after background light filtering is detected by single-photon detector 9, and the signal acquisition card 10 acquires the number of specularly reflected photons in the dual channels. , Computer 111 dual-channel specular reflection photon ratio Perform calculations, Transmitted to the second laser 2, and The output power of the second laser 2 is dynamically adjusted by multiplying it by a proportionality coefficient, so that the total gain of the dual channels satisfies the following: ,in P on Absorption wavelength l on The output power of the laser, in W; P off Absorption wavelength l off The output power of a laser, measured in W; T on and T off Temperature control filter 8 l on and l off The transmittance at the point is 0-1; ensuring that the signal strength received by the single-photon detector 9 is always below the saturation threshold.

[0035] Example 4: The signal enhancement method includes the following steps: Step 1: The first laser 1 and the second laser 2 alternately emit continuous light. After being switched by the optical switch 3, the continuous light is converted into pulsed light by the acousto-optic modulator 4. l on and l off The pulsed light is amplified by the erbium-doped fiber amplifier 5 and then alternately emitted into the atmosphere through the telescope 6. The telescope 6 receives the atmospheric echo signal and filters out the background light through the temperature-controlled filter 8. The transmittance of the temperature-controlled filter 8 is fixed by controlling the temperature of the temperature-controlled chamber 7. At wavelength; Step 2: The computer 111 calculates the ratio of the number of photons reflected by the dual-channel mirror in real time, multiplies the ratio of the number of photons reflected by the dual-channel mirror by the output power of the second laser 2, and adjusts the output power of the second laser 2.

[0036] Example 5: The signal enhancement method includes the following steps: Step a: The first laser 1 and the second laser 2 alternately emit continuous light, which passes through the optical switch 3, acousto-optic modulator 4, erbium-doped fiber amplifier 5, and telescope 6 before being emitted into the atmosphere. The telescope 6 receives the atmospheric echo signal and filters out the background light through the temperature-controlled filter 8, fixing the transmittance of the temperature-controlled filter 8 at a certain value. At wavelength; Step b: The atmospheric echo signal after background light filtering is detected by single-photon detector 9, and the signal acquisition card 10 acquires the number of specularly reflected photons from the dual channels. , PID controller 121 calculates error signals in real time. e ( t ):

[0037] t express t At any given time, when the error signal is input to the PID controller 121, a power adjustment command is generated, causing... The total gain of the channel satisfies G off : Real-time tracking The total gain of the channel satisfies G on : ,when At that time, the dual-channel signals were balanced. e ( t When ) ≠ 0, the PID controller 121 adjusts its output, causing the PID controller 121 to output satisfy:

[0038] in, , , The parameters are adjustable; the output power of the second laser 2 is dynamically adjusted via the digital-to-analog converter 122 and the drive circuit 123 until... e ( t → 0, achieving dual-channel balance; the digital-to-analog converter 122 will The signal is converted into a voltage signal and output to the drive circuit 123. The drive circuit 123 adjusts the drive current of the second laser 2 according to the received signal to ensure that its output power meets the following requirements: .

[0039] Example 6: The signal enhancement method includes the following steps: Step a: The first laser 1 and the second laser 2 alternately emit continuous light, which passes through the optical switch 3, acousto-optic modulator 4, erbium-doped fiber amplifier 5, and telescope 6 before being emitted into the atmosphere. The telescope 6 receives the atmospheric echo signal and filters out the background light through the temperature-controlled filter 8, fixing the transmittance of the temperature-controlled filter 8 at a certain value. At wavelength; Step b: The atmospheric echo signal after background light filtering is detected by single-photon detector 9, and the signal acquisition card 10 acquires the number of specularly reflected photons from the dual channels. , PID controller 121 calculates error signals in real time. e ( t ):

[0040] t express t At that moment, when At that time, the dual-channel signals were balanced. e ( t When ) ≠ 0, the PID controller 121 adjusts its output, causing the PID controller 121 to output satisfy:

[0041] in, , , For adjustable parameters, the proportional term The initial adjustment range is determined in response to the current error; the integral term... Eliminate historical error accumulation to ensure steady-state accuracy; differential term Predicting error trends and suppressing over-adjustment and oscillation; dynamically adjusting the output power of the second laser 2 via the digital-to-analog converter 122 and the drive circuit 123 until... e ( t→ 0, achieving dual-channel balance; the digital-to-analog converter 122 will The signal is converted into a voltage signal and output to the drive circuit 123. The drive circuit 123 adjusts the drive current of the second laser 2 according to the received signal to ensure that its output power meets the following requirements: .

Claims

1. A path integral differential absorption lidar signal enhancement system, characterized in that, The system includes an optical switch (3), an acousto-optic modulator (4), an erbium-doped fiber amplifier (5), a telescope (6), a temperature control filter (8), a single-photon detector (9), and a signal acquisition card (10) connected in sequence. The optical switch (3) is connected to a first laser (1) and a second laser (2). The signal acquisition card (10) and the second laser (2) are connected to each other through a power feedback control module (11) or an error signal calculation and processing module (12). The temperature control filter (8) is located inside a temperature control box (7).

2. The path integral differential absorption lidar signal enhancement system according to claim 1, characterized in that, The power feedback control module (11) is a computer (111).

3. The path integral differential absorption lidar signal enhancement system according to claim 1, characterized in that, The error signal calculation and processing module (12) includes a PID controller (121), a digital-to-analog converter (122), and a drive circuit (123) connected in sequence. The PID controller (121) is connected to the signal acquisition card (10), and the drive circuit (123) is connected to the second laser (2).

4. A signal enhancement method, using the path integral differential absorption lidar signal enhancement system as described in claim 2, characterized in that, Includes the following steps: Step 1: The first laser (1) and the second laser (2) alternately emit continuous light, which is then emitted into the atmosphere after passing through an optical switch (3), an acousto-optic modulator (4), an erbium-doped fiber amplifier (5), and a telescope (6). The telescope (6) receives the atmospheric echo signal and filters out the background light through a temperature-controlled filter (8). The transmittance of the temperature-controlled filter (8) is fixed at a certain value. At wavelength; Step 2: The computer (111) calculates the ratio of the number of photons reflected by the dual-channel mirror in real time, multiplies the ratio of the number of photons reflected by the dual-channel mirror by the output power of the second laser (2), and adjusts the output power of the second laser (2).

5. The signal enhancement method according to claim 4, characterized in that, In step 1, the continuous light is switched by the optical switch (3) and then converted into pulsed light by the acousto-optic modulator (4). λ on and λ off The pulsed light is amplified by the erbium-doped fiber amplifier (5) and then alternately emitted into the atmosphere through the telescope (6); the transmittance of the temperature-controlled filter (8) is fixed at a certain value by controlling the temperature of the temperature-controlled chamber (7). At wavelength.

6. The signal enhancement method according to claim 4, characterized in that, Step 2 is performed as follows: Step 2.1: The atmospheric echo signal after background light filtering is detected by a single-photon detector (9), and the signal acquisition card (10) acquires the number of specularly reflected photons in the dual channels. , ; Step 2.2, the computer (111) calculates the ratio of the number of photons reflected by the dual-channel mirror. Perform calculations, Transmitted to the second laser (2), and The output power of the second laser (2) is dynamically adjusted by multiplying it by a proportionality coefficient, so that the total gain of the dual channels satisfies: ,in P on Absorption wavelength λ on The output power of the laser, in W; P off Absorption wavelength λ off The output power of a laser, measured in W; T on and T off The temperature control filter (8) is respectively in λ on and λ off The transmittance at the point is in the range of 0-1; ensure that the signal strength received by the single-photon detector (9) is always below the saturation threshold.

7. A signal enhancement method, using the path integral differential absorption lidar signal enhancement system as described in claim 3, characterized in that, Includes the following steps: Step a: The first laser (1) and the second laser (2) alternately emit continuous light, which is then emitted into the atmosphere after passing through an optical switch (3), an acousto-optic modulator (4), an erbium-doped fiber amplifier (5), and a telescope (6). The telescope (6) receives the atmospheric echo signal and filters out the background light through a temperature-controlled filter (8). The transmittance of the temperature-controlled filter (8) is fixed at a certain value. At wavelength; Step b: The PID controller (121) calculates the error signal and controls the output, converts the output into a voltage signal and sends it to the drive circuit (123). The drive circuit (123) adjusts the drive current of the second laser (2) according to the voltage signal.

8. The signal enhancement method according to claim 7, characterized in that, Step 2 is performed as follows: Step b.1: The atmospheric echo signal after background light filtering is detected by a single-photon detector (9), and the signal acquisition card (10) acquires the number of specularly reflected photons in the dual channels. , ; Step b.2, the PID controller (121) calculates the error signal in real time. e ( t ): t express t At that moment, when At that time, the dual-channel signals were balanced. e ( t When )≠0, the PID controller (121) adjusts the output, causing the PID controller (121) to output satisfy: in, , , The output power of the second laser (2) is dynamically adjusted via a digital-to-analog converter (122) and a drive circuit (123) until it becomes adjustable. e ( t → 0, achieving dual-channel balance; Step b.3, the digital-to-analog converter (122) will The signal is converted into a voltage signal and output to the driving circuit (123). The driving circuit (123) adjusts the driving current of the second laser (2) according to the received signal so that its output power meets the following requirements: .

9. The signal enhancement method according to claim 8, characterized in that, The proportional term The initial adjustment range is determined in response to the current error. Integral term Eliminate historical error accumulation to ensure steady-state accuracy; differential term Predict the trend of error changes and suppress over-adjustment and oscillation.

10. The signal enhancement method according to claim 8, characterized in that, When the error signal is input to the PID controller (121), a power adjustment command is generated, causing... The total gain of the channel satisfies G off : Real-time tracking The total gain of the channel satisfies G on : .

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