1. A laser module for coherent lidar comprising: continuous laser, laser pulse modulation module, first beam splitter, second beam splitter and third beam splitter, wherein:

the continuous laser is used for outputting a continuous laser signal with a preset wavelength;

the first beam splitter is used for splitting laser signals output by the continuous laser into two paths, one path is used as local oscillator light and output to the second beam splitter, and the other path is used as signal light and output to the laser pulse modulation module;

the second beam splitter is used for dividing the local oscillator light output by the first beam splitter into N paths for output; wherein N is a positive integer greater than 1;

the laser pulse modulation module is used for modulating the input continuous laser signals into pulse light signals and outputting the pulse light signals;

the third beam splitter is used for dividing pulse optical signals input by the laser pulse modulation module into N paths to be output; wherein N is a positive integer greater than 1.

2. The laser module for coherent lidar of claim 1, further comprising N optical amplifier modules, wherein N is a positive integer greater than 1; the N optical amplifier modules are arranged in one-to-one correspondence with the N paths of pulse light signals output by the third beam splitter, and each optical amplifier module is used for amplifying the corresponding path of pulse light signal; the pulsed laser light output by the plurality of optical amplifier modules is directed in a specified spatial direction.

3. The laser module of claim 2, wherein the laser performance parameters output by each optical amplifier module are the same, and the relative delay of the laser pulses output by each optical amplifier module is adjustable.

4. A laser module for coherent lidar according to claim 3, wherein the relative delay of the laser pulses output by the optical amplifier modules is adjustable, comprising: the predetermined delay of the output light pulse of each optical amplifier module is achieved by adjusting the length of the optical fiber and the current on-off time in each optical amplifier module.

5. The laser module for coherent lidar according to claim 1, wherein the continuous laser has an emission wavelength of 0.9-2.5 microns; the spectral linewidth of the laser output by the continuous laser is less than 15 kHz; the pulse width output by the laser pulse modulation module is 0.1-2000 ns.

6. The laser module for coherent lidar according to claim 2, wherein the spectral linewidth of the laser light output by each of the optical amplifier modules is less than 10MHz, and the energy of the laser light single pulse output by each of the optical amplifier modules is 0.1 microjoule to 2000 microjoule.

7. A laser module for coherent lidar according to claim 2, wherein the continuous laser is a fiber laser; the optical amplifier module is an optical fiber device; the first beam splitter, the second beam splitter and the third beam splitter are all optical fiber beam splitters; and the continuous laser, the laser pulse modulation module, the optical amplifier module, the first beam splitter, the second beam splitter and the third beam splitter are connected by adopting optical fibers.

8. The laser module of claim 1, wherein the laser pulse modulation module is an acousto-optic modulator, an electro-optic modulator, or a magneto-optic modulator, and the acousto-optic modulator is further configured to generate a predetermined frequency shift of the input laser signal.

9. The laser module for coherent lidar of claim 1, wherein the splitting ratios of the first, second, and third beam splitters are a preset ratio; the beam splitting ratio of the second beam splitter is the same as that of the third beam splitter.

10. The laser module for coherent lidar of claim 1, further comprising N fiber circulators, wherein,

the N optical fiber circulators are arranged corresponding to N pulse light signals output by a laser module for coherent laser radar, and the input end of each optical fiber circulator is connected with one path of pulse light signal output end output by the laser module for coherent laser radar; wherein N is a positive integer greater than 1.

Background

The existing narrow-linewidth nanosecond pulse fiber laser used for the laser radar is generally a 1X1 module, namely a seed source module and an optical amplifier module. The inventor of the invention finds out through research that: because the range of measurement carried by a single optical amplifier module on a radar transmitter is limited, and a plurality of 1X1 modules are placed in a measurement system, the cost is high, and because the time sequence reference of each module is different, the laser pulse delay of each optical amplifier module is difficult to be accurately modulated, so that the large-range and high-precision measurement is difficult to realize.

Disclosure of Invention

In order to solve the above problems, the present invention provides a laser module for coherent lidar comprising: continuous laser, laser pulse modulation module, first beam splitter, second beam splitter and third beam splitter, wherein:

the continuous laser is used for outputting a continuous laser signal with a preset wavelength;

the first beam splitter is used for splitting laser signals output by the continuous laser into two paths, one path is used as local oscillator light and output to the second beam splitter, and the other path is used as signal light and output to the laser pulse modulation module;

the second beam splitter is used for dividing the local oscillator light output by the first beam splitter into N paths for output; wherein N is a positive integer greater than 1;

the laser pulse modulation module is used for modulating the input continuous laser signals into pulse light signals and outputting the pulse light signals;

the third beam splitter is used for dividing pulse optical signals input by the laser pulse modulation module into N paths to be output; wherein N is a positive integer greater than 1.

Furthermore, the optical amplifier also comprises N optical amplifier modules, wherein N is a positive integer greater than 1; the N optical amplifier modules are arranged in one-to-one correspondence with the N paths of pulse light signals output by the third beam splitter, and each optical amplifier module is used for amplifying the corresponding path of pulse light signal; the pulsed laser light output by the plurality of optical amplifier modules is directed in a specified spatial direction.

Furthermore, the laser performance parameters output by each optical amplifier module are the same, and the relative time delay of the laser pulses output by each optical amplifier module is adjustable.

Further, the relative delay of the laser pulse output by each optical amplifier module is adjustable, including: the predetermined delay of the output light pulse of each optical amplifier module is achieved by adjusting the length of the optical fiber and the current on-off time in each optical amplifier module.

Further, the emission wavelength of the continuous laser is 0.9-2.5 micrometers; the spectral linewidth of the laser output by the continuous laser is less than 15 kHz; the pulse width output by the laser pulse modulation module is 0.1-2000 ns.

Furthermore, the spectral line width of the laser output by each optical amplifier module is less than 10MHz, and the single pulse energy of the laser output by each optical amplifier module is 0.1-2000 microjoules.

Further, the continuous laser is a fiber laser; the optical amplifier module is an optical fiber device; the first beam splitter, the second beam splitter and the third beam splitter are all optical fiber beam splitters; and the continuous laser, the laser pulse modulation module, the optical amplifier module, the first beam splitter, the second beam splitter and the third beam splitter are connected by adopting optical fibers.

Further, the laser pulse modulation module is an acousto-optic modulator, an electro-optic modulator or a magneto-optic modulator, and the acousto-optic modulator is also used for generating a preset frequency shift on an input laser signal.

Further, the beam splitting ratio of the first beam splitter, the second beam splitter and the third beam splitter is a preset ratio; the beam splitting ratio of the second beam splitter is the same as that of the third beam splitter.

Further, the optical fiber ring device also comprises N optical fiber ring devices, wherein,

the N optical fiber circulators are arranged corresponding to N pulse light signals output by a laser module for coherent laser radar, and the input end of each optical fiber circulator is connected with one path of pulse light signal output end output by the laser module for coherent laser radar; wherein N is a positive integer greater than 1.

The laser module for the coherent laser radar provided by the invention can simultaneously output multi-path local oscillator light and signal light by only using one continuous laser as a seed light source and one laser pulse modulation module, thereby realizing multi-beam and multi-angle target detection. By adopting the scheme of the invention, the compactness of the whole structure of the laser is increased, and the power consumption and the cost are reduced. The input light sources of the multi-channel signal light are all from the same light source, so that the consistency of various parameter measurements of the output laser is effectively ensured. The single-type sub-source module brings a single-pulse time sequence reference, and the only time sequence reference can be used for accurately controlling the light-emitting time delay of a subsequent light path, so that the receiving and transmitting precision and the measuring precision of the laser radar system are greatly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions and advantages of 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 other drawings can be obtained by those skilled in the art without creative efforts.

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a block diagram of a laser module for coherent lidar according to an embodiment of the present invention;

fig. 2 is a block diagram of another structure of a laser module for coherent lidar according to an embodiment of the present invention;

fig. 3 is another structural block diagram of a laser module for coherent lidar according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention are 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 derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

Example (b):

fig. 1 is a block diagram of a laser module for coherent lidar according to an embodiment of the present invention. As shown in fig. 1, a laser module for coherent lidar comprising: continuous laser 1, laser pulse modulation module 4, first beam splitter 2, second beam splitter 3 and third beam splitter 5, wherein:

the continuous laser 1 is used to output a continuous laser signal of a predetermined wavelength.

The first beam splitter 2 is used for splitting the laser signal output by the continuous laser 1 into two paths, one path is used as local oscillation light and is output to the second beam splitter 3, and the other path is used as signal light and is output to the laser pulse modulation module 4;

the second beam splitter 3 is configured to split the local oscillation light output by the first beam splitter 2 into N paths for output; wherein N is a positive integer greater than 1;

the laser pulse modulation module 4 is used for modulating the input continuous laser signals into pulse light signals and outputting the pulse light signals;

the third beam splitter 5 is configured to split the pulsed light signal input by the laser pulse modulation module 4 into N paths for output; wherein N is a positive integer greater than 1.

The continuum laser 1, also referred to as seed laser, seed light source, is capable of providing a continuous laser signal of a predetermined wavelength.

Optionally, the laser pulse modulation module 4 is an acousto-optic modulator, an electro-optic modulator, or a magneto-optic modulator, and the acousto-optic modulator is further configured to generate a preset frequency shift on an input laser signal.

The acousto-optic modulator (AOM) module has a specific frequency shift amount, which is 80MHz in the invention. The main control circuit board of the laser controls the switch of the acousto-optic and the opening threshold width by controlling the radio frequency signal input into the acousto-optic modulator module, thereby cutting the continuous laser into the pulse laser with a certain width (for example, a few nanoseconds), and the opening time is recorded as the time sequence reference.

Of course, the electro-optical modulator, the magneto-optical modulator, the mechanical modulator, and the like can convert continuous laser signals into pulse optical signals, and the invention is applicable as long as the function of modulating the input continuous laser signals into pulse optical signals can be realized.

The splitting ratio of the first beam splitter 2, the second beam splitter 3 and the third beam splitter 5 is a preset ratio; the splitting ratio of the second beam splitter 3 is the same as that of the third beam splitter 5. Because the N paths of laser light output by the second beam splitter 3 and the N paths of laser light output by the third beam splitter 5 need to be coherently detected, the splitting ratio of the second beam splitter 3 is the same as that of the third beam splitter 5, and in specific implementation, each group of coherent detection signals are guaranteed to be in one-to-one correspondence, so that the accuracy of a detection structure is guaranteed.

The continuous laser 1 is a fiber laser; the optical amplifier module 6 is an optical fiber device; the first beam splitter 2, the second beam splitter 3 and the third beam splitter 5 are all optical fiber beam splitters; the continuous laser 1, the laser pulse modulation module 4, the optical amplifier module 6, the first beam splitter 2, the second beam splitter 3 and the third beam splitter 5 are all connected by optical fibers.

In one embodiment, the emission wavelength of the continuous laser 1 is 0.9-2.5 microns; the spectral linewidth of the laser output by the continuous laser 1 is less than 15 kHz; the pulse width output by the laser pulse modulation module 4 is 0.1-2000 ns.

In one embodiment, the spectral linewidth of the laser output from each of the optical amplifier modules 6 is the limit of the fourier transform, indicating that the inventive technique achieves very good beam quality. The laser single pulse energy output by each optical amplifier module 6 is 0.1 microjoule-2000 microjoule.

In an application scene (such as atmospheric detection), the laser single pulse energy output by each optical amplifier module 6 is 0.1 microjoule-150 microjoule.

In a preferred embodiment, the wavelengths generated by the continuous laser 1 are preferably in the optical communication C-Band (1520 nm to 1570 nm), and L-Band (i.e., 1570nm to 1610 nm). In the C-Band wave Band and the L-Band wave Band, except the influence of atmospheric molecular Rayleigh signals can be ignored, due to the high-speed development and maturation of optical communication devices, the optical devices are stable and reliable, and the safety factor of human eyes of the wave bands is high, so that the optical communication device can be operated in places with dense human mouths, such as cities, airports, meteorological stations and the like, and can realize miniaturization, convenience and human eye safety detection. In the prior art, the near infrared wave short wave band widely used for atmospheric measurement cannot realize all-fiber integration, and the system is huge and not compact.

The laser module for the coherent laser radar provided by the invention can simultaneously output multi-path local oscillator light and signal light by only using one continuous laser 1 as a seed light source and one laser pulse modulation module 4, thereby realizing multi-beam and multi-angle target detection. By adopting the scheme of the invention, the compactness of the whole structure of the laser is increased, and the power consumption and the cost are reduced. The input light sources of the multi-channel signal light are all from the same light source, so that the consistency of various parameter measurements of the output laser is effectively ensured. The single-type sub-source module brings a single-pulse time sequence reference, and the only time sequence reference can be used for accurately controlling the light-emitting time delay of a subsequent light path, so that the receiving and transmitting precision and the measuring precision of the laser radar system are greatly improved.

In one embodiment, as shown in fig. 2, N optical amplifier modules 6 are further included, where N is a positive integer greater than 1; the N optical amplifier modules 6 are arranged in one-to-one correspondence with the N pulsed light signals output by the third beam splitter 5, and each optical amplifier module 6 is configured to amplify a corresponding pulsed light signal; the pulsed laser light output from the plurality of optical amplifier modules 6 is directed in a specified spatial direction.

In fig. 2, an acousto-optic modulator (AOM) is taken as an example of the laser pulse modulation module 4.

When the continuum laser 1 is a fiber laser, the optical amplifier module 6 is a rare-earth-doped fiber amplifier module corresponding to the laser wavelength. For example, the optical amplifier module 6 is an erbium-doped or erbium-ytterbium-doped rare earth fiber amplifier module.

The invention takes the example that the central wavelength is 1548nm, the spectral line width is less than 15kHz, and the relative intensity noise is less than-140 dB/Hz.

Illustratively, the laser performance parameters output by each optical amplifier module 6 are the same, and the relative delay of the laser pulses output by each optical amplifier module 6 is adjustable.

Illustratively, the relative delay of the laser pulses output by each optical amplifier module 6 is adjustable, and includes: the predetermined delay of the output light pulse of each optical amplifier module 6 is realized by adjusting the length of the optical fiber and the current-off time in each optical amplifier module 6. The longer the fiber length, the longer the delay time.

In particular, each optical amplifier module 6 comprises a length of optical fibre; the length of the optical fiber in each optical amplifier module 6 is set to be a preset length, the pumping current of each optical amplifier module 6 is accurately controlled to be started according to preset time, and the current of each optical amplifier module 6 is set to be switched on and off according to preset time, so that the output time of the pulse laser of each optical amplifier module 6 is accurately controlled.

In an example, the second beam splitter 3 and the third beam splitter 5 are all-fiber passive devices specially made, laser light is input from one input end fiber, and will be split into multiple light portions to be output from different fibers, and each light portion occupies a predetermined power ratio, and 2 and N portions are taken as examples in the present invention.

The acousto-optic modulator module is an acousto-optic modulator module with a specific frequency shift, and the frequency shift amount is 80MHz as an example in the invention. The switch of acousto-optic and the width of opening threshold are controlled by controlling the radio frequency signal input into the acousto-optic modulator module, so that the continuous laser is cut off into nanosecond pulse laser.

The N optical amplifier modules 6 are illustrated as N modules that amplify the laser power of the input signal, respectively. In the invention, the input signal lights of the N optical amplifier modules 6 all come from the same seed source, namely from N output ends of the same beam splitter. In the invention, the average power output by each optical amplifier module 6 is larger than 1W, the single pulse energy is larger than 100 muJ, and the sideband mode rejection ratio is larger than 60 dB.

In the example, the input signal lights of the N optical amplifier modules 6 all come from the same seed source, that is, from the same beam splitter output end, and the N signal lights with similar powers are respectively connected to the N optical amplifier modules 6 for power amplification. Because the input signal lasers of each optical amplifier module 6 are all from the same seed source, and the output signal power is close, the consistency of the characteristics of the spectrum, the pulse width and the like of the output light pulses of each optical amplifier module 6 is ensured from the source; meanwhile, the uniqueness of the time base is ensured, and the time interval of the output light pulse among the optical amplifier modules 6 can be accurately controlled.

The consistency of the characteristics such as the spectrum and the pulse width of the output optical pulse of each optical amplifier module 6 is ensured from the source in the example, because the parameters such as the power, the center wavelength, the spectrum width and the noise of the signal laser in the N output optical fibers of the same beam splitter (third beam splitter 5) are basically consistent, the amplification factors of each optical amplifier module 6 on the signal laser are basically the same under the requirement of certain output power, and thus the consistency of the characteristics such as the spectrum and the pulse width of the output optical pulse of each optical amplifier module 6 can be ensured.

In the example, it is ensured from the source that the optical pulse output by each optical amplifier module 6 ensures the uniqueness of the time base, and the time interval of the optical pulse output between each optical amplifier module 6 can be accurately controlled, because the signal laser input to each optical amplifier module 6 comes from the same seed source, only one time sequence counter for controlling the on-off of the acousto-optic module is provided, and the on-off time and the frequency micro-variation of the time sequence counter are synchronous with the optical amplifier module 6 at the back, the problem that the on-off time sequence difference and the frequency micro-variation difference caused by a plurality of counters in a plurality of sub-source modules cannot be synchronized, and further the time interval of the optical pulse output by each optical amplifier module 6 cannot be accurately and stably controlled can be effectively avoided.

In the following, the principle and implementation of the present invention will be explained in detail from a specific application scenario, where N is 10 as an example.

As shown in fig. 2, a laser module for coherent lidar according to an embodiment of the present invention, operating around 1.5 μm wavelength, is a narrow linewidth nanosecond pulse fiber laser for lidar, and includes: one seed source module and 10 optical amplifier modules 6.

Wherein the seed source module comprises: a continuous laser 1 (CW) laser seed source with the emission wavelength of 1.5 μm provides original signal light for the whole system; the first beam splitter 2 is used for dividing a Continuous Wave (CW) laser seed source with the emission wavelength of 1.5 μm into two parts according to a preset proportion; the second beam splitter 3 is for equally dividing a part of the continuous signal light into 10 parts; an acousto-optic modulator (AOM) module is used for cutting a part of continuous signal light into pulse laser and generating fixed frequency shift; the third beam splitter 5 is used to equally split the pulsed laser light output from the AOM into 10 parts. The 10 optical amplifier modules 6 amplify the pulse signal light split by the third beam splitter 5, respectively.

The emission wavelength of the continuous laser 1 is 1.5 mu m, the spectral line width is less than 5kHz, the relative intensity noise is < -140dB/Hz, and the side mode suppression ratio is more than 40 dB.

The first beam splitter 2 is a special all-fiber passive device, and has one optical fiber at the input end and two optical fibers at the output end; for dividing a continuous laser emitting light with a wavelength of 1.5 μm into two parts in proportion.

The second beam splitter 3 is a special all-fiber passive device, and has an input end with one optical fiber and an output end with 10 optical fibers. By fusing a specific output end optical fiber of the second beam splitter 3 with the input end optical fiber of the beam splitter, the optical signal is divided into a plurality of signal lights and output from different optical fibers, and the power proportion of each light is customized, which takes 10 equal parts as an example in the invention. The optical signal equally divided by 10 here is referred to as local oscillator light according to the subsequent use.

An acousto-optic modulator (AOM) module is a fiber optic acousto-optic modulator with a specific amount of frequency shift. In some specific application scenarios, such as measuring atmospheric wind speed, an acousto-optic modulator is required to generate a frequency shift. In the present invention, the frequency shift amount is 80MHz as an example. The main control circuit board of the laser controls the switch of the acousto-optic and the opening threshold width by controlling the radio frequency signal input into the acousto-optic modulator module, so that the continuous laser is cut off into nanosecond pulse laser, and the opening time is recorded as a time sequence reference. Of course, in some specific application scenarios, the acousto-optic modulator may not generate a frequency shift, and only serves as a pulse modulation device to generate pulsed light.

The third beam splitter 5 is a special all-fiber passive device, and has an input end with one optical fiber and an output end with 10 optical fibers. By welding the AOM output signal fiber with the input end fiber, the optical signal is divided into multiple signal lights and output from different fibers, the power proportion of each light is customized, and 10 equal parts are taken as an example in the invention.

The 10 optical amplifier modules 6 have the same size and internal structure, and are respectively connected with 10 output end optical fibers of the third beam splitter 5. Each path of pulse signal light is amplified in each optical amplifier module 6 in about the same proportion, so that parameters of laser output by each optical amplifier module 6 are nearly consistent finally. The timing reference of all the optical amplifier modules 6 is the timing reference of the acousto-optic modulator in the seed source module, so that the output time of the pulse laser of each optical amplifier module 6 can be accurately controlled by combining the difference of the lengths of the optical paths of each optical amplifier module 6 and accurately controlling the pumping current starting time delay of each optical amplifier module 6.

As shown in fig. 3, in one embodiment, N fiber circulators 7 are further included, wherein,

the N optical fiber circulators 7 are arranged corresponding to N pulse light signals output by a laser module for coherent laser radar, and the input end of each optical fiber circulator 7 is connected with one path of pulse light signal output end output by the laser module for coherent laser radar; wherein N is a positive integer greater than 1.

The structure of the multi-path optical amplifier module based on the single-type sub-source module not only increases the compactness of the whole structure of the laser, but also reduces the cost and the power consumption.

The input light sources of the multi-path optical amplifier module are all from the same light source, so that the consistency of various parameter measurements of the laser output by each optical amplifier is ensured.

The single-photon source module of the invention brings single pulse time sequence reference, and the unique time sequence reference can be used for accurately controlling the light-emitting time delay of each optical amplifier module, thereby greatly improving the receiving and transmitting and measuring accuracy of the corresponding coherent laser radar system.

According to the invention, the light emitting direction of the laser module or the optical fiber circulator faces to the preset area, so that a technical basis is provided for the laser radar to realize simultaneous detection in multiple angles and large areas.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.