Fitting Method for Spontaneous Emission Noise of LiDAR System and Fiber Optic Sensing System

Abstract

The present application discloses a fitting method for the spontaneous emission noise of a lidar system and an optical fiber sensing system. Using the control variable method, by comparing co-located data and separated data, the spontaneous emission noise is fitted, which is beneficial to evaluating the performance of the laser. After measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, improving the detection distance and the accuracy of detection data of the lidar system and the optical fiber sensing system; in addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to achieve the detection of a single-photon lidar without the interference of spontaneous emission noise.

Description

Technical Field

[0001] The present invention relates to the technical field of lidar, and in particular to a fitting method for the spontaneous emission noise of a lidar system and a fiber optic sensing system. Background Art

[0002] Lidar is an active modern optical remote sensing technology and a hot research field in atmospheric remote sensing. Following microwave radar, lidar has increased the frequency of the radiation source to the optical frequency, which is four orders of magnitude higher than millimeter waves, enabling it to detect tiny targets, including aerosols and molecules in the atmosphere. Lidar emits laser pulses towards the detection target. After interacting with the target, the target backscattered signal is collected by an optical telescope and input into an optical receiver. After photoelectric detection and data processing, target information is obtained. Using laser as the carrier, lidar can carry information with amplitude, frequency, phase, and polarization state. Therefore, lidar can not only accurately measure distance but also accurately measure frequency shift, angle, attitude, and depolarization. Lidar mainly includes: ranging lidar, velocity measurement lidar, environmental monitoring lidar, imaging lidar, flash lidar, terrain mapping lidar, synthetic aperture lidar, etc.

[0003] A lidar system can be divided into a laser emission module and a receiver module. In the laser emission module, the linearly polarized light generated by a continuous wave laser is modulated into pulsed light by an acousto-optic modulator, then power-amplified by a fiber amplifier, and then emitted by a telescope. In the fiber amplifier, while the active particles return from the excited state to the ground state and amplify the signal, random incoherent spontaneous emission of the stimulated particles will occur. This spontaneous emission can be in any direction, can cause further stimulated emission, and can be amplified. This is called the spontaneous emission noise of the amplifier. The spontaneous emission process extracts the energy stored in the gain fiber, consumes a large number of upper-level inverted particles, and reduces the signal extraction rate of the gain. Therefore, the greater the spontaneous emission noise, the smaller the power of the signal amplified, that is, the smaller the signal gain. At the same time, the frequency band of the spontaneous emission noise is very wide and can occupy the entire gain bandwidth, deteriorating the performance of the system.

[0004] According to whether the optical axes of the optical emission system and the optical reception system of the lidar are coaxial, the lidar can be divided into two structures: separate transmitter and receiver and co-located transmitter and receiver. The separate transmitter and receiver structure uses two telescope optical systems for transmission and reception, with non-coaxial optical axes. The receiving telescope only receives the atmospheric echo signal and background noise. For the co-located system, the transmitting system and the receiving system use the same telescope system with coincident optical axes. Therefore, the receiving system is also affected by the mirror scattering of the transmitting system and the spontaneous emission noise of the laser. Summary of the Invention

[0005] In view of this, the present application provides a fitting method for the spontaneous emission noise of a lidar system and an optical fiber sensing system, which can precisely measure the spontaneous emission noise and improve the detection range and the accuracy of detection data of the lidar system and the optical fiber sensing system.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A lidar system, the lidar system comprising:

[0008] A signal source, a transceiver co-located module and a transceiver separated module; the signal source is used to provide a trigger acquisition signal to simultaneously trigger the transceiver co-located module and the transceiver separated module to detect a detection target;

[0009] Wherein, the transceiver co-located module has a first telescope, the first telescope is used to emit a detection beam and receive co-located data returned by the detection target; the transceiver separated module has a second telescope, the second telescope is used to receive separated data returned by the detection target; based on the co-located data and the separated data, the spontaneous emission noise is fitted.

[0010] Preferably, in the above lidar system, the first telescope and the second telescope are different;

[0011] The first telescope is a single-tube telescope, which is used to simultaneously emit the detection light and receive the co-located data returned by the detection target; the second telescope is a single-tube telescope, which is used to receive the separated data returned by the detection target.

[0012] Preferably, in the above lidar system, it further comprises:

[0013] An upper computer, the upper computer is used to perform data processing on the co-located data and the separated data to fit the spontaneous emission noise of the lidar system.

[0014] Preferably, in the above lidar system, the transceiver co-located module further comprises: a laser, an erbium-doped amplifier, a circulator, an optical switch, a filter and a first detector, the laser is used to emit the detection beam;

[0015] Among them, the first output terminal of the signal source is connected to the input terminal of the laser, the output terminal of the laser is connected to the input terminal of the erbium-doped amplifier, the output terminal of the erbium-doped amplifier is connected to the input terminal of the circulator, the first output terminal of the circulator is connected to the first telescope, the second output terminal of the circulator is connected to the input terminal of the optical switch, the output terminal of the optical switch is connected to the input terminal of the filter, the output terminal of the filter is connected to the first input terminal of the first detector, the second output terminal of the signal source is connected to the second input terminal of the first detector, and the output terminal of the first detector is connected to the host computer.

[0016] Preferably, in the above lidar system, the transceiver separation module further includes: a laser, an erbium-doped amplifier, a circulator, the first telescope, and a second detector;

[0017] Among them, the first output terminal of the signal source is connected to the input terminal of the laser, the output terminal of the laser is connected to the input terminal of the erbium-doped amplifier, the output terminal of the erbium-doped amplifier is connected to the input terminal of the circulator, the first output terminal of the circulator is connected to the first telescope, the third output terminal of the signal source is connected to the first input terminal of the second detector, the output terminal of the second telescope is connected to the second input terminal of the second detector, and the output terminal of the second detector is connected to the host computer.

[0018] The present invention also provides an optical fiber sensing system, which includes:

[0019] A signal source, a laser, a circulator, an optical fiber coil, and an optical switch; the signal source is used to provide a trigger acquisition signal to trigger the laser to emit a detection beam for detecting a detection target;

[0020] Among them, the optical switch is used to control the switch of the circulator, and the optical switch has a first state and a second state; in the first state, the optical switch is open, and after the detection beam is emitted from the first output terminal of the circulator, it is output by the optical fiber coil, and the detection target returns co-located data based on the detection beam; in the second state, the optical switch cuts off the first output terminal of the circulator, and the detection beam enters the optical switch through the second output terminal of the circulator to receive separated data.

[0021] Preferably, in the above optical fiber sensing system, it further includes:

[0022] An erbium-doped amplifier, a filter, a detector, and a host computer; the host computer is used to perform data processing on the co-located data and the separated data to fit the spontaneous emission noise of the optical fiber sensing system.

[0023] Among them, the first output end of the signal source is connected to the input end of the laser, the output end of the laser is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped amplifier is connected to the input end of the circulator, the first output end of the circulator is connected to the input end of the fiber optic disk, the second output end of the circulator is connected to the input end of the optical switch, the output end of the optical switch is connected to the input end of the filter, the output end of the filter is connected to the first input end of the detector, the second output end of the signal source is connected to the second input end of the detector, and the output end of the detector is connected to the host computer.

[0024] The present invention also provides a fitting method for spontaneous emission noise. The fitting method is applied to a lidar system or a fiber optic sensing system. The lidar system is the above-mentioned lidar system, and the fiber optic sensing system is the above-mentioned fiber optic sensing system. The fitting method includes:

[0025] A trigger acquisition signal is provided by a signal source;

[0026] Based on the trigger acquisition signal, a co-located transceiver module and a separated transceiver module are triggered to perform synchronous detection on a detection target;

[0027] The co-located data and the separated data returned by the detection target are received;

[0028] The co-located data and the separated data are respectively subtracted from the local noise;

[0029] A linear interval is selected to normalize the co-located data;

[0030] The normalized co-located data and the separated data are subtracted from each other to obtain the spontaneous emission noise;

[0031] The spontaneous emission noise is fitted by a function.

[0032] As can be seen from the above description, in the fitting method for the spontaneous emission noise of the lidar system and the fiber optic sensing system provided by the technical solution of the present invention, the control variable method is used. By comparing the co-located data and the separated data, the spontaneous emission noise is fitted, which is beneficial to evaluating the performance of the laser. At the same time, after measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, and the detection distance and the accuracy of the detection data of the lidar system and the fiber optic sensing system can be improved. In addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to realize the detection of a single-photon lidar without the interference of spontaneous emission noise. Description of the Drawings

[0033] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0034] The structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those who are familiar with this technology to understand and read, and are not used to limit the limiting conditions under which the present application can be implemented. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present application can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present application.

[0035] Figure 1 It is a schematic structural diagram of a lidar system provided by an embodiment of the present invention;

[0036] Figure 2 It is a flowchart of a fitting method for the spontaneous emission noise of a lidar system provided by an embodiment of the present invention;

[0037] Figure 3 It is a comparison diagram of the number of photons received by the transceiver-separated module and the transceiver-co-located module without correcting the spontaneous emission noise;

[0038] Figure 4 It is a comparison diagram of the number of photons received by the transceiver-separated module and the transceiver-co-located module after correcting the spontaneous emission noise;

[0039] Figure 5 It is the cross-correlation coefficient between the co-located end after ASE correction and the separated end;

[0040] Figure 6 It is a schematic structural diagram of an optical fiber sensing system provided by an embodiment of the present invention. Detailed implementation manners

[0041] The following will clearly and completely describe the embodiments in the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present application.

[0042] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below with reference to the drawings and specific implementation manners.

[0043] ReferenceFigure 1 , Figure 1 is a schematic structural diagram of a lidar system provided by an embodiment of the present invention. Among them, the operating wavelength of the lidar system is 1548 nm.

[0044] As Figure 1 shown, the lidar system includes:

[0045] a signal source 11, a transceiver co-located module 100, and a transceiver separated module 200; the signal source 11 is used to provide a trigger acquisition signal to simultaneously trigger the transceiver co-located module 100 and the transceiver separated module 200 to detect a detection target;

[0046] Among them, the transceiver co-located module 100 has a first telescope 15, and the first telescope 15 is used to emit a detection beam and receive the co-located data returned by the detection target; the transceiver separated module 200 has a second telescope 19, and the second telescope 19 is used to receive the separated data returned by the detection target; based on the co-located data and the separated data, the spontaneous emission noise is fitted.

[0047] In the embodiment of the present invention, the first telescope 15 and the second telescope 19 are different;

[0048] the first telescope 15 is a single-tube telescope, which is used to simultaneously emit the detection light and receive the co-located data returned by the detection target; the second telescope 19 is a single-tube telescope, which is used to receive the separated data returned by the detection target.

[0049] It should be noted that the second telescope 19 is only used during factory calibration. After the spontaneous emission noise (ASE noise) is fitted, the calibrated single-tube telescope can be used alone to realize the detection of a single-photon lidar without ASE noise interference.

[0050] Based on Figure 1 the shown lidar system, it further includes: a host computer 21, and the host computer 21 is used to perform data processing on the co-located data and the separated data to fit the spontaneous emission noise of the lidar system.

[0051] As Figure 1 shown, both the transceiver co-located module 100 and the transceiver separated module 200 have a laser 12, an erbium-doped amplifier 13, a circulator 14, an optical switch 16, a filter 17, a first detector 18, and the first telescope 15, and the laser 12 is used to emit the detection beam;

[0052] Among them, the first output end of the signal source 11 is connected to the input end of the laser 12, the output end of the laser 12 is connected to the input end of the erbium-doped amplifier 13, the output end of the erbium-doped amplifier 13 is connected to the input end 1 of the circulator 14, the first output end 2 of the circulator 14 is connected to the first telescope 15, the second output end 3 of the circulator 14 is connected to the input end of the optical switch 16, the output end of the optical switch 16 is connected to the input end of the filter 17, the output end of the filter 17 is connected to the first input end of the first detector 18, the second output end of the signal source 11 is connected to the second input end of the first detector 18, and the output end of the first detector 18 is connected to the upper computer 21.

[0053] Specifically, when the signal source 11 provides a trigger acquisition signal, it triggers the laser 12 to emit the detection beam. After being amplified by the erbium-doped amplifier 13, the detection beam is emitted through the first output end 2 of the circulator 14 and the first telescope 15. The detection target returns co-location data based on the detection beam. The first telescope 15 receives the co-location data and sends it to the circulator 14, and enters the optical switch 16 through the second output end 3 of the circulator 14 to eliminate specular reflection, and then enters the first detector 18 after passing through the filter 17, and is transmitted to the upper computer 21 through the first detector 18.

[0054] Among them, the first detector 18 can be a single-photon detector.

[0055] As Figure 1 shown, the transceiver-separated module 200 further includes: a laser 12, an erbium-doped amplifier 13, a circulator 14, the first telescope 15, and a second detector 20; the second detector 20 can be a single-photon detector.

[0056] Among them, the first output end of the signal source 11 is connected to the input end of the laser 12, the output end of the laser 12 is connected to the input end of the erbium-doped amplifier 13, the output end of the erbium-doped amplifier 13 is connected to the input end 1 of the circulator 14, the first output end 2 of the circulator 14 is connected to the first telescope 15, the third output end of the signal source 11 is connected to the first input end of the second detector 20, the output end of the second telescope 19 is connected to the second input end of the second detector 20, and the output end of the second detector 20 is connected to the upper computer 21.

[0057] Specifically, when the signal source 11 provides a trigger acquisition signal, the laser 12 is triggered to emit the detection beam. After being amplified by the erbium-doped amplifier 13, the detection beam exits through the first output end 2 of the circulator 14 and the first telescope 15. The detection target returns the split data based on the detection beam. The second telescope 19 receives the split data and sends it to the second detector 20, and then it is transmitted to the host computer 21 through the second detector 20. The host computer 21 processes the data based on the co-located data and the split data, and fits the spontaneous emission noise of the lidar system.

[0058] As can be seen from the above description, in the lidar system provided by the technical solution of the present invention, the control variable method is used to fit the spontaneous emission noise through the co-located data and the split data, which is beneficial to evaluating the performance of the laser. At the same time, after measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, and the detection range and the accuracy of the detection data of the lidar system and the fiber optic sensing system can be improved. In addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to realize the detection of a single-photon lidar without the interference of spontaneous emission noise.

[0059] Based on the above lidar system, another embodiment of the present invention further provides a method for fitting the spontaneous emission noise of a lidar system, as Figure 2 shown Figure 2 is a flowchart of a method for fitting the spontaneous emission noise of a lidar system provided by an embodiment of the present invention. The fitting method includes:

[0060] Step S101: A trigger acquisition signal is provided by a signal source;

[0061] Step S102: Based on the trigger acquisition signal, trigger the co-located transceiver module and the split transceiver module to perform synchronous detection on the detection target;

[0062] Step S103: Receive the co-located data and the split data returned by the detection target;

[0063] Step S104: Subtract the local noise from the co-located data and the split data respectively;

[0064] Step S105: Select a linear interval to normalize the co-located data;

[0065] Step S106: Subtract the normalized co-located data from the split data to obtain the spontaneous emission noise;

[0066] Step S107: Fit the spontaneous emission noise through a function.

[0067] Specifically, first, a trigger acquisition signal is provided by a signal source to trigger the co-located module and the separated transceiver module to synchronously detect a detection target. Then, the received co-located data and separated data are respectively subtracted from the local noise to eliminate the influence of background noise.

[0068] The number of photons of a lidar system that ignores local noise is in the form of:

[0069]

[0070] where N(R) represents the number of photons of the echo signal returned at distance R, E represents the number of photons of the emitted pulse, η0 represents the optical reception efficiency of the entire system, η q is the quantum efficiency of the detector, h is Planck's constant, v is the frequency of the laser, A is the effective area of the second telescope, O(R) is the set overlap factor of the spot reception field of view, c is the speed of light, Δt is the pulse width, and β and σ are respectively the backscattering coefficient and extinction coefficient of the atmosphere.

[0071] In the calculation process, using the logarithmically transformed distance correction signal S(R) will greatly improve the operation speed:

[0072] S(R) = In[R 2 N(R)]

[0073] If a reference point is selected, whose distance from the laser emission position is R0, then the above can be written as:

[0074]

[0075] where S0 and β0 are respectively the distance correction signal at the reference point position and the total scattered coefficient of the atmosphere in the image. Differentiating the above equation with respect to distance can obtain:

[0076]

[0077] When the atmosphere of the lidar system is relatively uniform, it can be considered that the backscattering coefficient does not change with the change of distance, so the first term on the right side of the above equation is cancelled out and becomes:

[0078]

[0079] σ hom The subscript represents that the calculated atmospheric extinction coefficient at this time assumes a uniform atmosphere. Therefore, the intervals with the same slope of the echo signals received by the co-located module and the separated transceiver module are intercepted to ensure that the subsequent processed co-located data and separated data are obtained by detecting the same section of uniform atmosphere.

[0080] To eliminate the influence caused by the optical switch and filter of the transceiver co-location module, as well as the inconsistent barrel sizes of the transceiver co-location module and the transceiver separation module, the data of the transceiver co-location module is normalized:

[0081] log 10 ((N D (R)-n)R 2 )-log 10 ((N s (R)-n)R 2 )=C

[0082] Where N D (R) and N s (R) are the number of photons received by the transceiver co-location module and the transceiver separation module respectively, n is the local noise, and C is a constant.

[0083] From the above formula, the normalized co-location data N sn (R) can be obtained as:

[0084] N sn (R)=(N s (R)-n)×10 c

[0085] Subtracting the separated data from the normalized co-location data can obtain the spontaneous emission noise N ASE (R) of the laser:

[0086] N ASE (R)=N sn (R)-(N D (R)-n)

[0087] Finally, the spontaneous emission noise is fitted with a function in the following form:

[0088]

[0089] Refer to Figures 3 - 5 , Figure 3 which is the comparison diagram of the number of photons received by the transceiver separation module and the transceiver co-location module without correcting the spontaneous emission noise, Figure 4 which is the comparison diagram of the number of photons received by the transceiver separation module and the transceiver co-location module after correcting the spontaneous emission noise, Figure 5 which is the cross-correlation coefficient between the co-location end after ASE correction and the separated end.

[0090] Figures 3 - 5In the shown manner, 50 represents the photon number curve received by the transceiver-separated module, and 60 represents the photon number curve received by the transceiver-collocated module. It can be seen that, compared with before correction, the data of the transceiver-separated module and the transceiver-collocated module after correction have reached a very high degree of correlation, indicating that the present invention has effectively fitted the spontaneous emission noise.

[0091] As can be seen from the above description, in the method for fitting the spontaneous emission noise of the lidar system provided by the technical solution of the present invention, the control variable method is used. By comparing the collocated data and the separated data, the spontaneous emission noise is fitted, which is beneficial to evaluating the performance of the laser. At the same time, after measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, and the detection distance and the accuracy of the detection data of the lidar system and the fiber optic sensing system can be improved. In addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to achieve the detection of a single-photon radar without the interference of spontaneous emission noise.

[0092] Based on the above embodiments, another embodiment of the present invention further provides a fiber optic sensing system, as Figure 6 shown, Figure 6 which is a schematic structural diagram of a fiber optic sensor provided by an embodiment of the present invention. The fiber optic sensing system includes:

[0093] A signal source 31, a laser 32, a circulator 34, an optical fiber coil 35, and an optical switch 36; the signal source 31 is used to provide a trigger acquisition signal to trigger the laser 32 to emit a detection beam for detecting a detection target;

[0094] Among them, the optical switch 36 is used to control the switch of the circulator 34, and the optical switch 36 has a first state and a second state; in the first state, the optical switch 36 is open, and after the detection beam exits from the first output end 2 of the circulator 34, it is output by the optical fiber coil 35, and the detection target returns collocated data based on the detection beam; in the second state, the optical switch 36 cuts off the first output end of the circulator 34, and the detection beam enters the optical switch 36 through the second output end 3 of the circulator 34 to receive separated data.

[0095] Based on Figure 6 the shown fiber optic sensing system, it further includes:

[0096] An erbium-doped amplifier 33, a filter 37, a detector 38, and a host computer 39; the host computer 39 is used to perform data processing on the collocated data and the separated data to fit the spontaneous emission noise of the fiber optic sensing system;

[0097] Among them, the first output end of the signal source 31 is connected to the input end of the laser 32, the output end of the laser 32 is connected to the input end of the erbium-doped amplifier 33, the output end of the erbium-doped amplifier 33 is connected to the input end 1 of the circulator 34, the first output end 2 of the circulator 34 is connected to the input end of the fiber optic disc 35, the second output end 3 of the circulator 34 is connected to the input end of the optical switch 36, the output end of the optical switch 36 is connected to the input end of the filter 37, the output end of the filter 37 is connected to the first input end of the detector 38, the second output end of the signal source 31 is connected to the second input end of the detector 38, and the output end of the detector 38 is connected to the host computer 39.

[0098] Specifically, when the optical switch 36 is in the first state, the optical switch 36 is open. The detection beam emitted by the laser 32 is amplified by the erbium-doped amplifier 33, and then exits through the first output end 2 of the circulator 34 and is transmitted by the fiber optic disc 35. The detection target returns co-located data based on the detection beam. The fiber optic disc 35 receives the co-located data and sends it to the circulator 34, enters the optical switch 36 through the second output end 3 of the circulator 34 to eliminate specular reflection, then passes through the filter 37 and enters the detector 38, and is transmitted to the host computer 39 through the detector 38; in the second state, the optical switch 36 cuts off the first output end 2 of the circulator 34. The detection beam emitted by the laser 32 is amplified by the erbium-doped amplifier 33, enters the optical switch 36 through the second output end 3 of the circulator 34 to obtain off-set data, then passes through the filter 37 and enters the detector 38, and is transmitted to the host computer 39 through the detector 38.

[0099] In the fiber optic sensing system, the acquisition of co-located data and off-set data is achieved by the optical switch 36 controlling the circulator 34. When collecting co-located data, the optical switch 36 is open at this time. The detection beam exits through the first output end 2 of the circulator 34 and is transmitted by the fiber optic disc 35, and then is reflected and enters the second output end 3 of the circulator 34, and enters the filter 37 after passing through the optical switch 36; when collecting off-set data, the optical switch 36 cuts off the input of the first output end 2 of the circulator 34 at this time, so the off-set data without spontaneous emission noise is received at the second output end 3 of the circulator 34.

[0100] As can be seen from the above description, in the fiber optic sensing system provided by the technical solution of the present invention, the control variable method is used to fit the spontaneous emission noise by comparing the co-located data and the separated data, which is beneficial to evaluating the performance of the laser. At the same time, after measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, and the detection range and the accuracy of the detection data of the lidar system and the fiber optic sensing system can be improved. In addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to achieve the detection of a single-photon radar without the interference of the spontaneous emission noise.

[0101] Based on the above fiber optic sensing system, another embodiment of the present invention further provides a fitting method for the spontaneous emission noise of a fiber optic sensing system, as Figure 2 shown, the fitting method includes:

[0102] Step S101: Provide a trigger acquisition signal by a signal source;

[0103] Step S102: Based on the trigger acquisition signal, trigger the co-located transceiver module and the separated transceiver module to perform synchronous detection on the detection target;

[0104] Step S103: Receive the co-located data and the separated data returned by the detection target;

[0105] Step S104: Subtract the local noise from the co-located data and the separated data respectively;

[0106] Step S105: Select a linear interval to normalize the co-located data;

[0107] Step S106: Subtract the normalized co-located data from the separated data to obtain the spontaneous emission noise;

[0108] Step S107: Fit the spontaneous emission noise through a function.

[0109] It should be noted that the fitting method for the spontaneous emission noise adopted by the fiber optic sensing system and the lidar system is the same. The fitting method for the spontaneous emission noise of the lidar system in the above embodiment can be referred to, and details are not described herein again.

[0110] As can be seen from the above description, in the method for fitting the spontaneous emission noise of the fiber optic sensing system provided by the technical solution of the present invention, the control variable method is used. By comparing the co-located data and the separated data, the spontaneous emission noise is fitted, which is beneficial to evaluating the performance of the laser. At the same time, after measuring the spontaneous emission noise, by selecting a filter with an appropriate bandwidth and subsequent signal noise processing algorithms, the influence of the spontaneous emission noise on the echo signal can be removed, and the detection range and the accuracy of the detection data of the lidar system and the fiber optic sensing system can be improved. In addition, after fitting the spontaneous emission noise, a calibrated single-tube telescope can be used alone to achieve the detection of a single-photon radar without the interference of spontaneous emission noise.

[0111] In this specification, the various embodiments are described in a progressive, or parallel, or a combination of progressive and parallel manners. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other.

[0112] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the article or device including the above element.

[0113] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lidar system, characterized in that, The lidar system includes: a signal source, a co-located transceiver module, and a separated transceiver module; the signal source is used to provide a trigger acquisition signal to simultaneously trigger the co-located transceiver module and the separated transceiver module to detect a detection target. Among them, the co-located transceiver module has a first telescope, and the first telescope is used to emit a detection beam and receive co-located data returned by the detection target; the separated transceiver module has a second telescope, and the second telescope is used to receive separated data returned by the detection target; based on the co-located data and the separated data, the spontaneous emission noise is fitted. Among them, the fitting process of the spontaneous emission noise includes: Subtracting the local noise from the co-located data and the separated data respectively. Selecting a linear interval to normalize the co-located data. Subtracting the normalized co-located data from the separated data to obtain the spontaneous emission noise. Fitting the spontaneous emission noise through a function.

2. The lidar system according to claim 1, wherein The first telescope and the second telescope are different. The first telescope is a single-tube telescope, which is used to simultaneously emit the detection beam and receive the co-located data returned by the detection target. The second telescope is a single-tube telescope, which is used to receive the separated data returned by the detection target.

3. The lidar system according to claim 1, wherein, It further includes: A host computer, which is used to process the co-located data and the separated data to fit the spontaneous emission noise of the lidar system.

4. The lidar system according to claim 1, wherein The co-located transceiver module further includes: a laser, an erbium-doped amplifier, a circulator, an optical switch, a filter, and a first detector, and the laser is used to emit the detection beam. Among them, the first output end of the signal source is connected to the input end of the laser, the output end of the laser is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped amplifier is connected to the input end of the circulator, the first output end of the circulator is connected to the first telescope, the second output end of the circulator is connected to the input end of the optical switch, the output end of the optical switch is connected to the input end of the filter, the output end of the filter is connected to the first input end of the first detector, the second output end of the signal source is connected to the second input end of the first detector, and the output end of the first detector is connected to the host computer.

5. The lidar system according to claim 1, wherein, The separated transceiver module further includes: a laser, an erbium-doped amplifier, a circulator, the first telescope, and a second detector. Among them, the first output end of the signal source is connected to the input end of the laser, the output end of the laser is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped amplifier is connected to the input end of the circulator, the first output end of the circulator is connected to the first telescope, the third output end of the signal source is connected to the first input end of the second detector, the output end of the second telescope is connected to the second input end of the second detector, and the output end of the second detector is connected to the host computer.

6. An optical fiber sensing system, characterized in that, The fiber optic sensing system includes: A signal source, a laser, a circulator, an optical fiber coil, and an optical switch; the signal source is used to provide a trigger acquisition signal to trigger the laser to emit a detection beam to detect a detection target. Wherein, the optical switch is used to control the switch of the circulator, and the optical switch has a first state and a second state; in the first state, the optical switch is turned on, and after the detection beam is emitted from the first output end of the circulator, it is output by the optical fiber disk, and the detection target returns co-located data based on the detection beam; in the second state, the optical switch cuts off the first output end of the circulator, and the detection beam enters the optical switch through the second output end of the circulator to receive off-located data; the co-located data and the off-located data are used to fit the spontaneous emission noise; Wherein, the fitting process of the spontaneous emission noise includes: Subtracting the local noise from the co-located data and the off-located data respectively; Selecting a linear interval to normalize the co-located data; Taking the difference between the normalized co-located data and the off-located data to obtain the spontaneous emission noise; Fitting the spontaneous emission noise through a function.

7. The fiber optic sensing system according to claim 6, wherein It further includes: An erbium-doped amplifier, a filter, a detector, and a host computer; the host computer is used to perform data processing on the co-located data and the off-located data to fit the spontaneous emission noise of the fiber optic sensing system; Wherein, the first output end of the signal source is connected to the input end of the laser, the output end of the laser is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped amplifier is connected to the input end of the circulator, the first output end of the circulator is connected to the input end of the optical fiber disk, the second output end of the circulator is connected to the input end of the optical switch, the output end of the optical switch is connected to the input end of the filter, the output end of the filter is connected to the first input end of the detector, the second output end of the signal source is connected to the second input end of the detector, and the output end of the detector is connected to the host computer.

8. A fitting method for spontaneous emission noise, the fitting method being applied to a lidar system or an optical fiber sensing system, the lidar system being the lidar system according to any one of claims 1-5, and the optical fiber sensing system being the optical fiber sensing system according to claim 6 or 7, characterized in that, The fitting method includes: Providing a trigger acquisition signal by a signal source; Based on the trigger acquisition signal, triggering the co-located transceiver module and the off-located transceiver module to perform synchronous detection on the detection target; Receiving the co-located data and the off-located data returned by the detection target; Subtracting the local noise from the co-located data and the off-located data respectively; Selecting a linear interval to normalize the co-located data; Taking the difference between the normalized co-located data and the off-located data to obtain the spontaneous emission noise; Fitting the spontaneous emission noise through a function.

Images