CN115792857A - Device for reducing spontaneous radiation noise of coaxial single-photon laser radar - Google Patents
Device for reducing spontaneous radiation noise of coaxial single-photon laser radar Download PDFInfo
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- CN115792857A CN115792857A CN202211427072.5A CN202211427072A CN115792857A CN 115792857 A CN115792857 A CN 115792857A CN 202211427072 A CN202211427072 A CN 202211427072A CN 115792857 A CN115792857 A CN 115792857A
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Abstract
The embodiment of the invention provides a device for reducing spontaneous radiation noise of a coaxial single-photon laser radar. The device comprises: the device comprises a first laser, a second laser, a time sequence adjuster, an optical fiber amplifier, an optical transmitting device, an optical receiving device and a detector; the first laser emits a first laser pulse, the second laser emits a second laser pulse, and the output wavelengths of the first laser and the second laser are different; the time sequence adjuster controls the first laser pulse to be input into the optical fiber amplifier before the second laser pulse so that the first laser pulse absorbs spontaneous emission noise in the optical fiber amplifier; the optical transmitting device receives the second laser pulse sent by the optical fiber amplifier and transmits the second laser pulse to the detection target, the optical receiving device receives an echo signal returned from the detection target, and the detector detects the echo signal. The invention reduces the spontaneous radiation noise of the laser amplifier and improves the accuracy of the radar detection data through wavelength division multiplexing and time division multiplexing.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a device for reducing spontaneous radiation noise of a coaxial single-photon laser radar.
Background
The laser radar is a radar system that detects a characteristic amount such as a position and a velocity of a target by emitting a laser beam. For a direct detection coaxial single-photon laser radar system, the problem of serious spontaneous radiation noise exists, and the spontaneous radiation noise has important influence on the performance of the laser radar system. Therefore, how to reduce the spontaneous emission noise is essential.
Disclosure of Invention
The embodiment of the invention aims to provide a device for reducing spontaneous radiation noise of a coaxial single-photon laser radar. The specific technical scheme is as follows:
the invention provides a device for reducing spontaneous radiation noise of a coaxial single-photon laser radar, which comprises:
the device comprises a first laser, a second laser, a time sequence adjuster, an optical fiber amplifier, an optical transmitting device, an optical receiving device and a detector;
the first laser emits a first laser pulse, the second laser emits a second laser pulse, and the output wavelength of the first laser is different from the output wavelength of the second laser;
the timing adjuster controls the first laser pulse to be input into the optical fiber amplifier earlier than the second laser pulse so that the first laser pulse absorbs spontaneous emission noise in the optical fiber amplifier;
the optical transmitting device receives the second laser pulse sent by the optical fiber amplifier and transmits the second laser pulse to a detection target, the optical receiving device receives an echo signal returned from the detection target, and the detector detects the echo signal.
Optionally, the timing adjuster is a first optical switch.
Optionally, the optical emission device includes:
a circulator and a telescope;
the first end of the circulator is connected with the optical fiber amplifier, the second end of the circulator is connected with the telescope, and the third end of the circulator is connected with the optical receiving device;
the circulator inputs the second laser pulse transmitted by the optical fiber amplifier to the telescope, and the telescope transmits the second laser pulse to the detection target;
the circulator transmits the signal input to the telescope to the optical receiving device.
Optionally, the optical receiving apparatus includes:
a light path breaker;
the light path breaker is connected with the third end of the circulator;
the light path breaker cuts off the mirror reflection receiving light path of the telescope.
Optionally, the optical path breaker is a second optical switch.
Optionally, the optical receiving apparatus further includes:
a narrow band filter;
the input end of the narrow-band filter is connected with the light path breaker, and the output end of the narrow-band filter is connected with the detector;
the narrow-band filter filters the echo signal to filter noise generated by the first laser pulse and the spontaneous emission noise.
Optionally, the optical receiving apparatus further includes:
a temperature control device;
the filter is arranged in the temperature control device, and the temperature control device controls the temperature of the narrow-band filter.
Optionally, the method further includes:
a processor;
the processor is connected with the optical receiving device and corrects the echo signal.
Alternatively to this, the first and second parts may,
the difference range of the output wavelength of the first laser and the output wavelength of the second laser is-3 nm.
Optionally, the optical fiber amplifier is an erbium-doped optical fiber amplifier.
The embodiment of the invention provides a device for reducing spontaneous emission noise of a coaxial single-photon laser radar, which comprises a first laser, a second laser, a time sequence regulator, an optical fiber amplifier, an optical transmitting device, an optical receiving device and a detector, wherein the first laser is connected with the second laser through a first optical fiber; the first laser emits a first laser pulse, the second laser emits a second laser pulse, and the output wavelength of the first laser is different from that of the second laser; the time sequence adjuster controls the first laser pulse to be input into the optical fiber amplifier before the second laser pulse so that the first laser pulse absorbs spontaneous radiation noise in the optical fiber amplifier; the optical transmitting device receives the second laser pulse sent by the optical fiber amplifier and transmits the second laser pulse to the detection target, the optical receiving device receives an echo signal returned from the detection target, and the detector detects the echo signal. The invention can pre-release the layout number in the optical fiber amplifier through wavelength division multiplexing and time division multiplexing, thereby reducing the spontaneous radiation noise of the laser amplifier.
Of course, it is not necessary for any product or method to achieve all of the above-described advantages at the same time for practicing the invention.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an apparatus for reducing spontaneous emission noise of a coaxial single-photon laser radar according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a first optical switch according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another apparatus for reducing spontaneous emission noise of a coaxial single-photon lidar according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a signal transmission direction of a circulator provided by an embodiment of the invention;
FIG. 5 is a schematic structural diagram of another apparatus for reducing spontaneous emission noise of a coaxial single-photon laser radar according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of another apparatus for reducing spontaneous emission noise of a coaxial single-photon lidar according to an embodiment of the present invention;
FIG. 7 is a timing diagram of laser pulses provided in accordance with an embodiment of the present invention;
FIG. 8 is a diagram illustrating comparison of echo signals according to an embodiment of the present invention;
fig. 9 is a schematic diagram of an echo signal according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The traditional laser radar system generally utilizes an optical transmission mirror, a reflecting mirror and the like to realize optical transformation of light beams, and the system has a complex structure and cannot realize flexible transformation of the light beams. Compared with the traditional laser radar system, the all-fiber laser radar can realize flexible conversion of light beams, but the all-fiber laser radar has the problem of serious spontaneous radiation noise.
According to whether the optical axes of the laser radar transmitting system and the receiving system are coaxial or not, the laser radar can be divided into a transmitting-receiving simultaneous position and a transmitting-receiving separate position. For the receiving and transmitting co-located structure, the same telescope optical system is adopted by the transmitting system and the receiving system, the optical axes are coincident, and the problem of optical axis stability does not exist, but the receiving and transmitting co-located structure is influenced by mirror surface scattering and laser spontaneous radiation noise, so that the problems that the near-field mirror surface scattering annihilates the real signal, the far-field laser spontaneous radiation noise annihilates the real signal, the signal to noise ratio is low, and the echo signal is inaccurate exist.
Laser radar systems can be divided into coherent detection and direct detection depending on the detection mode of the laser radar system. The direct detection laser radar system is limited by a larger filter bandwidth, and the detector is a more sensitive single-photon detector, so that the detector receives more spontaneous radiation noise signal energy, the signal-to-noise ratio of the laser radar system is greatly influenced, and finally the spontaneous radiation noise has more serious influence on the performance of the laser radar system.
For a directly detected transmitting-receiving co-located all-fiber laser radar system, namely for a coaxial single-photon laser radar system, spontaneous radiation noise has important influence on the performance of the laser radar system. Based on this, the present invention provides an apparatus for reducing spontaneous emission noise of a coaxial single-photon laser radar, as shown in fig. 1, the apparatus comprising:
the device comprises a first laser 1, a second laser 2, a timing adjuster 3, a fiber amplifier 4, an optical transmitting device 5, an optical receiving device 6 and a detector 7.
The first laser emits a first laser pulse, the second laser emits a second laser pulse, the output wavelength of the first laser is different from that of the second laser, and the difference range between the output wavelength of the first laser and that of the second laser can be-3 nm. The first laser pulse may be a pre-seed light and the second laser pulse may be a probe laser. Optionally, the output wavelength of the first laser is 1548nm; the output wavelength of the second laser is 1550nm. The output wavelength range of the first laser depends on the fiber amplifier, which needs to satisfy the condition that the fiber amplifier can amplify, for example, the output wavelength of the first laser can be 1550 ± 3nm. Optionally, the fiber amplifier is an erbium-doped fiber amplifier.
The timing adjuster controls the first laser pulse to be input into the fiber amplifier earlier than the second laser pulse so that the first laser pulse absorbs spontaneous emission noise in the fiber amplifier. The response bandwidth of the fiber amplifier is wide, and the invention utilizes wavelength division multiplexing and time division multiplexing. Wavelength division multiplexing uses 1548nm pre-amplification seed light to pre-release the population number in the optical fiber amplifier, and then 1550nm detection laser is amplified, actually passes through signals with two wavelengths of the amplifier, and the optical receiving device receives the 1550nm detection laser. Time division multiplexing means that 1548nm pre-released seed light and 1550nm detection laser pass through an optical fiber amplifier in a time-sharing manner, and a time interval that 1548nm and 1550nm lasers pass through the optical fiber amplifier in sequence is controlled by using a time sequence adjuster so as to ensure that pre-released spontaneous radiation noise is released completely. Since the spontaneous emission noise in the optical fiber amplifier is already released, the generated spontaneous emission noise is significantly reduced when the 1550nm probe laser passes through the optical fiber amplifier.
The optical transmitting device receives the second laser pulse sent by the optical fiber amplifier and transmits the second laser pulse to the detection target, the optical receiving device receives an echo signal returned from the detection target, and the detector detects the echo signal.
Optionally, the timing adjuster is a first optical switch. As shown in fig. 2, the first optical switch includes a first input Port1, a second input Port2, a first output Port3, and a second output Port4. The first input end is connected with the first laser, the second input end is connected with the second laser, the first output end is connected with the optical fiber amplifier, and the second output end is empty. The first optical switch further includes a signal input terminal (not shown in the figure), the signal input terminal is connected to a driving control circuit, and the driving control circuit inputs a high level or a low level into the first optical switch to control the conduction relationship between the input terminal and the output terminal. When the signal input end inputs a high level, the first input end is connected with the first output end, the second input end is connected with the second output end, and at the moment, a first laser pulse emitted by the first laser is input into the optical fiber amplifier. When the signal input end inputs a low level, the first input end is connected with the second output end, the second input end is connected with the first output end, and at the moment, a second laser pulse emitted by the second laser is input into the optical fiber amplifier. The control of the laser pulses with different time sequences can be realized through the control of the level signal.
As an alternative embodiment, as shown in fig. 3, the optical emission device 5 includes: a circulator 51 and a telescope 52. The first end a of the circulator is connected with the optical fiber amplifier, the second end b of the circulator is connected with the telescope, and the third end c of the circulator is connected with the optical receiving device.
As shown in fig. 4, it is a schematic diagram of an optical path in the circulator, and the arrow direction in fig. 4 is a signal transmission direction. The circulator 51 inputs the second laser pulse transmitted from the optical fiber amplifier 4 to the telescope 52, and the telescope 52 transmits the second laser pulse to the detection target. The circulator transmits the signal input to the telescope to the optical receiving device 6.
As an alternative embodiment, as shown in fig. 5, the optical receiving device 6 includes: an optical path breaker 61.
The light path breaker is connected with the third end of the circulator.
The light path breaker cuts off the mirror reflection receiving light path of the telescope.
Optionally, the optical path breaker is a second optical switch. The second optical switch structure may be the same as the first optical switch structure, in particular, the second optical switch structure is shown in fig. 2.
As another optional implementation, the optical receiving apparatus further includes: a narrow band filter 62.
The input end of the narrow-band filter is connected with the light path breaker, and the output end of the narrow-band filter is connected with the detector.
The narrow-band filter filters the echo signal to filter noise generated by the first laser pulse and spontaneous emission noise.
The mirror reflection receiving optical path is an optical path between the telescope and the circulator and between the circulator and the filter. The second optical switch is used for cutting off the mirror reflection receiving optical path behind the telescope, and the filter is used for filtering the echo signal, so that background light noise, noise generated by the first laser pulse and spontaneous radiation noise can be eliminated, and the influence caused by the spontaneous radiation noise is reduced. Optionally, the 3dB bandwidth of the narrow-band filter is not higher than 0.3nm.
As another optional implementation, the optical receiving apparatus further includes: a temperature control device 63.
The filter is arranged in the temperature control device, and the temperature control device controls the temperature of the narrow-band filter.
Because the filter is a narrow-band filter, the temperature control device can keep the filter stable when being influenced by temperature, and the light with the preset wave band can pass through the temperature control device under the condition of the temperature of the filter.
In an alternative embodiment, as shown in fig. 6, the apparatus for reducing spontaneous emission noise of an in-line single photon lidar of the present invention further comprises:
a processor 8.
The processor is connected with the optical receiving device and corrects the echo signals.
In practical application, the echo signals can be corrected through a signal noise processing algorithm, so that the echo signals which are not influenced by spontaneous radiation noise are obtained, and the accuracy of the laser radar detection data is improved.
In addition, under the assumption of uniform atmosphere, the echo signal waveform of the laser radar equation is utilized, and the actually measured signal is subjected to further noise removal through polynomial fitting.
As shown in fig. 7, the curve corresponding to the large peak is a second laser pulse timing curve emitted by the second laser, i.e., pulsed light emitted by the 1550nm laser, and the curve corresponding to the small peak is a first laser pulse timing curve emitted by the first laser, i.e., pulsed light emitted by the 1548nm laser. In fig. 7, the ordinate represents power, and the abscissa represents time.
As shown in fig. 8, the solid line is an echo signal that is not subjected to pre-release at 1548nm, the linear dotted line is an echo signal subjected to pre-release at 1548nm, the dotted line is an echo signal subjected to filtering and pre-release, and the dotted line is an echo signal subjected to filtering, pre-release and fitting. In fig. 8, the ordinate represents power, and the abscissa represents time.
As shown in fig. 9, it is a real echo signal obtained by using the apparatus for reducing spontaneous emission noise of an in-line single photon lidar shown in fig. 6. In fig. 9, the ordinate represents power, and the abscissa represents time.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the system embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and reference may be made to the partial description of the method embodiment for relevant points.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement or the like made within the spirit and principle of the present application shall be included in the scope of the claims of the present application.
Claims (10)
1. An apparatus for reducing in-line single photon lidar spontaneous emission noise comprising:
the device comprises a first laser, a second laser, a time sequence adjuster, an optical fiber amplifier, an optical transmitting device, an optical receiving device and a detector;
the first laser emits a first laser pulse, the second laser emits a second laser pulse, and the output wavelength of the first laser is different from the output wavelength of the second laser;
the timing regulator controls the first laser pulse to be input into the optical fiber amplifier before the second laser pulse so that the first laser pulse absorbs spontaneous emission noise in the optical fiber amplifier;
the optical transmitting device receives the second laser pulse sent by the optical fiber amplifier and transmits the second laser pulse to a detection target, the optical receiving device receives an echo signal returned from the detection target, and the detector detects the echo signal.
2. The apparatus according to claim 1 wherein the timing adjuster is a first optical switch.
3. The apparatus for reducing coaxial single photon lidar spontaneous emission noise according to claim 1, wherein said optical emission means comprises:
a circulator and a telescope;
the first end of the circulator is connected with the optical fiber amplifier, the second end of the circulator is connected with the telescope, and the third end of the circulator is connected with the optical receiving device;
the circulator inputs the second laser pulse transmitted by the optical fiber amplifier to the telescope, and the telescope transmits the second laser pulse to the detection target;
the circulator transmits the signal input to the telescope to the optical receiving device.
4. The apparatus for reducing the spontaneous emission noise of coaxial single photon lidar according to claim 3, wherein the optical receiving apparatus comprises:
a light path breaker;
the light path breaker is connected with the third end of the circulator;
the light path isolator isolates the specular reflection receiving light path of the telescope.
5. The apparatus according to claim 4 wherein the optical path interrupter is a second optical switch.
6. The apparatus for reducing in-line single photon lidar spontaneous emission noise according to claim 4, wherein said optical receiving means further comprises:
a narrow band filter;
the input end of the narrow-band filter is connected with the light path breaker, and the output end of the narrow-band filter is connected with the detector;
the narrow-band filter filters the echo signal to filter noise generated by the first laser pulse and the spontaneous emission noise.
7. The apparatus for reducing in-line single photon lidar spontaneous emission noise according to claim 6, wherein said optical receiving means further comprises:
a temperature control device;
the filter is arranged in the temperature control device, and the temperature control device controls the temperature of the narrow-band filter.
8. The apparatus for reducing coaxial single photon lidar spontaneous emission noise according to claim 1, further comprising:
a processor;
the processor is connected with the optical receiving device and corrects the echo signals.
9. The apparatus for reducing in-line single photon lidar spontaneous emission noise according to claim 1,
the difference range of the output wavelength of the first laser and the output wavelength of the second laser is-3 nm.
10. The apparatus according to claim 1, wherein said fiber amplifier is an erbium doped fiber amplifier.
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| CN202211427072.5A CN115792857A (en) | 2022-11-15 | 2022-11-15 | Device for reducing spontaneous radiation noise of coaxial single-photon laser radar |
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