Single-channel laser heterodyne spectrometer

Abstract

The invention discloses a single-channel laser heterodyne spectrometer. Comprising a plurality of optical fiber collimating mirrors, a plurality of optical switches, a plurality of amplifiers, a plurality of narrow-band optical filters, a plurality of local oscillator lasers, a plurality of optical fiber beam combiners, a signal generation circuit, a single wavelength division multiplexer, a single high-speed photoelectric detector, a radio frequency processing circuit, a Schottky diode, an AD acquisition circuit and an upper computer. The number of the optical fiber collimating mirrors, the number of the optical switches, the number of the amplifiers, the number of the narrow-band optical filters, the number of the local oscillator lasers and the number of the optical fiber beam combiners are the same. All the components are connected in sequence, and finally, spectrum processing software built in the upper computer analyzes and processes acquired signals, and calculates to obtain the vertical profile / column concentration of the greenhouse gas. According to the single-channel laser heterodyne spectrometer, the virtual digital phase locking device is adopted to replace an existing entity phase locking device, and the single-channel laser heterodyne spectrometer has the advantages that a heterodyne detection circuit can be simplified, and the system response speed can be increased.

Description

Technical Field

[0001] The invention relates to a spectral measurement technology for environmental monitoring, in particular to a single-channel laser heterodyne spectrometer for synchronous measurement of multi-component greenhouse gas column concentrations / profiles. Background Art

[0002] Carbon in nature is cyclical, and there is often a temporary stop in the process of carbon cycling, which can be further divided into two types: "source" and "sink". Carbon sinks and sources are a set of concepts closely related to climate change and carbon cycles, and are inextricably linked to achieving carbon neutrality. Timely and accurate accounting of the carbon source and sink flux of the entire sector is the key to the country's formulation of the implementation path for the "dual carbon" goal.

[0003] At present, my country is facing the problem of insufficient regional carbon source and sink assessment capabilities, which leads to relatively large uncertainties in climate change assessments. Establishing a high-density greenhouse gas column concentration / profile observation network is an important means to solve this problem. At present, the National Atmospheric Composition Change Detection Network (NDACC) and the Total Carbon Column Observation Network (TCCON) have been established internationally, with the aim of conducting long-term observations of greenhouse gas column concentrations and profile information, so as to better grasp the spatiotemporal distribution of greenhouse gases and quantify the total amount of sources and sinks, and reduce the uncertainty of regional greenhouse gas source and sink assessments. In order to control data quality, the observation stations used to measure greenhouse gas profiles all use the same set of ground-based high-resolution Fourier transform spectrometers (IFS 125HR) produced by Bruker, Germany. Although the ground-based high-resolution Fourier transform spectrometer has high measurement accuracy and can measure a wide range of gas molecules, it has the problem of being bulky and having poor environmental adaptability, making it difficult to deploy observation stations on a large scale. At present, the TCCON observation network has deployed more than 30 stations around the world, and only Hefei and Xianghe in my country have observation stations. However, due to my country's vast land area, changeable regional climate, large differences in greenhouse gas emission fluxes, and insufficient carbon source and sink monitoring capabilities, it is necessary to establish a more intensive greenhouse gas observation network.

[0004] Against the backdrop of the realization of the "dual carbon" strategic goals, there is currently no standard product in China that is comparable to the ground-based high-resolution Fourier transform spectrometer. Therefore, there is an urgent need for a greenhouse gas profile detection device that is environmentally adaptable and mobile.

[0005] In this regard, researchers engaged in related technologies at home and abroad have realized the detection of atmospheric multi-component greenhouse gases by increasing the number of laser heterodyne spectral channels. Unlike single-channel time-division multiplexing technology, this method controls multiple local oscillator lasers to emit light at the same time, which can truly realize the simultaneous detection of atmospheric gas components. For example, Wang Jingjing and Xue Zhenyue from the Anguang Institute of the Chinese Academy of Sciences used this method to build a set of all-fiber near-infrared laser heterodyne atmospheric CO2 and CH4 column concentration / profile detection systems and mid-infrared laser heterodyne atmospheric CH4 and N2O profile detection systems; Rodin and others from the Russian Space Research Center combined differential detection technology to simultaneously detect the absorption spectra of CO2 and CH4 in the entire atmosphere with high resolution, thereby obtaining the wind speed profile of the middle and upper atmosphere of the earth. However, although the increase in the number of heterodyne detection channels can achieve true simultaneous detection, the corresponding hardware circuit also needs to increase with the increase in the number of heterodyne detection channels, resulting in a relatively complex overall hardware circuit, and the corresponding system complexity, cost, and power consumption also increase exponentially. Summary of the invention

[0006] The present invention is to avoid the deficiencies existing in the above-mentioned prior art and provide a single-channel laser heterodyne spectrometer to simplify the heterodyne detection circuit and improve the system response speed.

[0007] The present invention adopts the following technical solutions to solve the technical problems.

[0008] A single-channel laser heterodyne spectrometer of the present invention comprises a plurality of optical fiber collimators, a plurality of optical switches, a plurality of amplifiers, a plurality of narrow-band optical filters, a plurality of local oscillator lasers, a plurality of optical fiber combiners, a signal generating circuit, a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, an AD acquisition circuit and a host computer; the plurality of optical fiber collimators, the plurality of optical switches, the plurality of amplifiers, the plurality of narrow-band optical filters, the plurality of local oscillator lasers and the plurality of optical fiber combiners are the same in number; The solar tracker receives sunlight and introduces the sunlight into multiple fiber combiners through multiple optical switches, multiple amplifiers, and multiple narrow-band optical filters in sequence; the multiple fiber combiners are connected to a host computer through a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, and an AD acquisition circuit in sequence; the sawtooth signal generated by the signal generation circuit is input into the multiple fiber combiners through multiple local oscillator lasers; and the multi-channel frequency modulation signals generated by the signal generation circuit are respectively input into the multiple optical switches.

[0009] The input ends of the plurality of fiber optic collimators are connected to the output ends of the sun tracker, and the sun tracker introduces sunlight into the plurality of fiber optic collimators; The output ends of the plurality of optical fiber collimators are connected to the input ends of the plurality of optical switches through optical fibers and correspond one to one, and the sunlight is coupled into the plurality of optical fibers respectively and then introduced into the plurality of optical switches; The output ends of the plurality of optical switches are connected to the input ends of the plurality of amplifiers in a one-to-one correspondence and are connected to the plurality of frequency modulation signal output ends of the signal generating circuit in a one-to-one correspondence; The output ends of the plurality of amplifiers are connected to the input ends of the plurality of narrow-band optical filters in a one-to-one correspondence; The plurality of sawtooth signal output terminals of the signal generating circuit are connected to the input terminals of the plurality of local oscillator lasers; The output ends of the multiple local oscillator lasers are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence, and the output ends of the multiple narrow-band optical filters are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence; The output ends of the multiple optical fiber combiners are all connected to the input end of the single wavelength division multiplexer; The output end of the single wavelength division multiplexer is connected to the input end of the single high-speed photodetector; The output end of the single high-speed photodetector is connected to the input end of the radio frequency processing circuit; The output end of the radio frequency processing circuit is connected to the input end of the Schottky diode; The output end of the Schottky diode is connected to the input end of the AD acquisition circuit; The output end of the AD acquisition circuit is connected to the acquisition signal input end of the host computer; The spectrum processing software in the host computer analyzes and processes the collected signals to calculate the vertical profile / column concentration of greenhouse gases.

[0010] The structural features of a single-channel laser heterodyne spectrometer of the present invention are also as follows: Furthermore, the multiple local oscillator lasers are all narrow linewidth semiconductor lasers.

[0011] Furthermore, the wavelengths of the multiple local oscillator lasers are different.

[0012] Furthermore, there are three local oscillator lasers, and the wavelengths of the three local oscillator lasers are 1522nm, 1564nm and 1572nm respectively.

[0013] Furthermore, the central wavelengths of the plurality of narrow-band optical filters are different.

[0014] Furthermore, the signal generating circuit is a high-precision FPGA signal generating circuit.

[0015] Furthermore, the multiple amplifiers are semiconductor optical amplifiers or optical fiber amplifiers.

[0016] Furthermore, the AD acquisition circuit includes a digital-to-analog converter LTC2270.

[0017] Furthermore, the signal generating circuit outputs the multi-channel frequency modulation signals to a plurality of optical switches, and outputs a plurality of sawtooth signals to a plurality of local oscillator lasers.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The invention discloses a single-channel laser heterodyne spectrometer, comprising a plurality of optical fiber collimators, a plurality of optical switches, a plurality of amplifiers, a plurality of narrow-band optical filters, a plurality of local oscillator lasers, a plurality of optical fiber combiners, a signal generating circuit, a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, an AD acquisition circuit and a host computer; the plurality of optical fiber collimators, the plurality of optical switches, the plurality of amplifiers, the plurality of narrow-band optical filters, the plurality of local oscillator lasers and the plurality of optical fiber combiners are of the same number; the above-mentioned components are connected in sequence, and finally the spectrum processing software built into the host computer analyzes and processes the collected signals, and calculates and obtains the vertical profile / column concentration of greenhouse gases.

[0019] The single-channel laser heterodyne spectrometer of the present invention adopts a virtual digital phase locker to replace the existing physical phase locker, which has the advantages of being able to simplify the heterodyne detection circuit, improve the system response speed, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The structure block diagram of a single-channel laser heterodyne spectrometer of the present invention.

[0021] Figure 2 This is a high-resolution spectrum signal diagram of the transmittance of carbon dioxide, methane and water vapor in the entire atmosphere measured synchronously by the single-channel laser heterodyne spectrometer of the present invention.

[0022] The present invention will be further described below through specific implementation modes in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0023] See also Figure 1 A single-channel laser heterodyne spectrometer of the present invention comprises a plurality of optical fiber collimators, a plurality of optical switches, a plurality of amplifiers, a plurality of narrow-band optical filters, a plurality of local oscillator lasers, a plurality of optical fiber combiners, a signal generating circuit, a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, an AD acquisition circuit and a host computer; the plurality of optical fiber collimators, the plurality of optical switches, the plurality of amplifiers, the plurality of narrow-band optical filters, the plurality of local oscillator lasers and the plurality of optical fiber combiners are the same in number; The solar tracker receives sunlight and introduces the sunlight into multiple fiber combiners through multiple optical switches, multiple amplifiers, and multiple narrow-band optical filters in sequence; the multiple fiber combiners are connected to a host computer through a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, and an AD acquisition circuit in sequence; the sawtooth signal generated by the signal generation circuit is input into the multiple fiber combiners through multiple local oscillator lasers; and the multi-channel frequency modulation signals generated by the signal generation circuit are respectively input into the multiple optical switches.

[0024] The input ends of the plurality of fiber optic collimators are connected to the output ends of the sun tracker, and the sun tracker introduces sunlight into the plurality of fiber optic collimators; Multiple fiber collimators couple sunlight into multiple optical fibers respectively and output the sunlight to multiple optical switches through the optical fibers; the multiple optical switches are used to perform intensity modulation of different frequencies on the power-amplified sunlight according to different frequency modulation signals of the signal generation circuit.

[0025] The output ends of the plurality of optical fiber collimators are connected to the input ends of the plurality of optical switches through optical fibers and correspond one to one, and the sunlight is coupled into the plurality of optical fibers respectively and then introduced into the plurality of optical switches; Multiple optical switches simultaneously modulate the intensity of sunlight coupled into the optical fiber at different frequencies, so that the digital phase-locked correlation demodulation principle can be used to synchronously demodulate the spectral signal of the greenhouse gas transmittance of the entire layer of the atmosphere at the corresponding frequency.

[0026] The output ends of the plurality of optical switches are connected to the input ends of the plurality of amplifiers in a one-to-one correspondence and are connected to the plurality of frequency modulation signal output ends of the signal generating circuit in a one-to-one correspondence; The output ends of the plurality of amplifiers are connected to the input ends of the plurality of narrow-band optical filters in a one-to-one correspondence; The plurality of sawtooth signal output terminals of the signal generating circuit are connected to the input terminals of the plurality of local oscillator lasers; The output ends of the multiple local oscillator lasers are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence, and the output ends of the multiple narrow-band optical filters are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence; Multiple fiber combiners are used to combine local oscillator lasers of different wavelengths with sunlight of different modulation frequencies. Multiple local oscillator lasers of different wavelengths can solve the problem of improving the signal-to-noise ratio of heterodyne signals caused by the power saturation effect limitation of the detector in a single heterodyne channel.

[0027] The output ends of the multiple optical fiber combiners are all connected to the input end of the single wavelength division multiplexer; The output end of the single wavelength division multiplexer is connected to the input end of the single high-speed photodetector; A single wavelength division multiplexer is used for low-loss secondary beam combining of multiple primary combined light beams input from multiple optical fiber combiners, and the obtained secondary combined light beams are output to a single high-speed photodetector through one optical fiber; The output end of the single high-speed photodetector is connected to the input end of the radio frequency processing circuit; A single high-speed photodetector is used to beat the local oscillator lasers of different wavelengths with the sunlight of different modulation frequencies to generate heterodyne signals corresponding to the modulation frequency characteristics. A single high-speed photodetector is used to simultaneously detect multiple heterodyne signals.

[0028] The output end of the radio frequency processing circuit is connected to the input end of the Schottky diode; The RF processing circuit includes amplifier ZX60-4016E-S.

[0029] The output end of the Schottky diode is connected to the input end of the AD acquisition circuit; The Schottky diode is a high-sensitivity zero-bias Schottky diode DHM124AA.

[0030] The output end of the AD acquisition circuit is connected to the acquisition signal input end of the host computer; The spectrum processing software in the host computer analyzes and processes the collected signals to calculate the vertical profile / column concentration of greenhouse gases.

[0031] The spectral processing software of the host computer is used to process the heterodyne signal and perform digital phase-locked correlation demodulation on the collected signal to obtain the absorption spectrum signal of the entire atmospheric greenhouse gas corresponding to the target wavelength and invert the greenhouse gas column concentration / profile. The high-speed A / D sampling circuit is directly connected to the Schottky diode, and a virtual digital phase-locked device is used to replace the existing physical phase-locked device. A high-performance digital phase-locked demodulation algorithm is built into the spectral processing software of the host computer to synchronously demodulate the entire atmospheric transmittance spectrum signal of multiple greenhouse gases. The digital phase-locked module of the software replaces the existing hardware-integrated phase-locked amplifier, which simplifies the system circuit structure and cost.

[0032] The single-channel laser heterodyne spectrometer of the present invention introduces sunlight into each optical switch after being introduced by multiple optical fiber collimators. The optical switch modulates the sunlight according to the frequency modulation signal given by the signal generation circuit and outputs it to multiple amplifiers. The multiple amplifiers are used to amplify the sunlight power under the power limit of the local oscillator laser caused by the power saturation of the photoelectric detector and output it to multiple narrow-band optical filters. The multiple narrow-band optical filters are used to filter out sunlight other than the target detection wavelength and output it to multiple optical fiber combiners. The multiple local oscillator lasers are used to detect the target greenhouse gas and output the detection signal to the multiple optical fiber combiners and receive the sawtooth signal given by the signal generation circuit. ; Multiple fiber combiners are used to combine the sunlight sent by multiple narrow-band optical filters and the local oscillator lasers sent by multiple local oscillator lasers, and then input them into a single wavelength division multiplexer; the single wavelength division multiplexer is used to combine the primary combined light from multiple fiber combiners again and send it to a single high-speed photodetector; the single high-speed photodetector is used to generate a heterodyne signal according to the secondary combined light transmitted by the single wavelength division multiplexer and output it to a Schottky diode; the Schottky diode is used to detect the power of the heterodyne signal and output the detected power signal to the AD acquisition circuit; the AD acquisition circuit converts the power signal into a digital signal and outputs it to the host computer.

[0033] In a specific implementation, the multiple local oscillator lasers are all narrow linewidth semiconductor lasers.

[0034] Local oscillator lasers with different operating wavelengths are used to detect multiple components of greenhouse gases. Local oscillator lasers are generally wavelength-tunable narrow-linewidth semiconductor lasers.

[0035] During specific implementation, the wavelengths of the multiple local oscillator lasers are different.

[0036] In a specific implementation, the number of the plurality of local oscillator lasers is three, and the wavelengths of the three local oscillator lasers are 1522 nm, 1564 nm and 1572 nm respectively.

[0037] Three local oscillator lasers with wavelengths of 1522nm, 1564nm and 1572nm are used to detect and scan the absorption spectra of multiple greenhouse gas components respectively.

[0038] In a specific implementation, the central wavelengths of the multiple narrow-band optical filters are different.

[0039] During specific implementation, the signal generating circuit is a high-precision FPGA signal generating circuit.

[0040] The high-precision FPGA signal generation circuit of the present invention is used to simultaneously generate multiple sawtooth waveform signals and simultaneously inject local oscillator lasers of different wavelengths; it is also used to generate frequency modulation signals and output them to multiple amplifiers. The FPGA of the high-precision FPGA signal generation circuit uses an Altera Cyclone IV series device, model EP4CE10F17C8N.

[0041] The DAC model of the FPGA signal generation circuit is DAC5672, with a resolution of 14 bits, a maximum conversion speed of 250MHz, and a designed scanning waveform frequency of 0.5Hz. It can achieve dual-channel output and then be transmitted to each laser in multiple channels. It can flexibly realize arbitrary waveform settings, and the output waveform voltage accuracy is better than 0.5mV.

[0042] In a specific implementation, the multiple amplifiers are semiconductor optical amplifiers or optical fiber amplifiers.

[0043] Multiple amplifiers are used to increase the power of sunlight coupled into single-mode optical fibers. The modulated sunlight enters a semiconductor optical amplifier or a fiber amplifier for narrowband optical power amplification, and then is combined with local oscillator lasers of different wavelengths through a fiber combiner. Finally, the output of the combiner is connected to the input of the wavelength division multiplexer for low-loss combination again, which can effectively avoid the optical power saturation effect of the photodetector and the loss in the combination process, resulting in a reduction in the heterodyne signal-to-noise ratio, thereby improving the accuracy of detection.

[0044] In a specific implementation, the AD acquisition circuit includes a digital-to-analog converter LTC2270.

[0045] The AD acquisition circuit is used to collect the power and voltage values ​​of heterodyne signals with different modulation frequencies at high speed. The model of the digital-to-analog converter of the AD acquisition circuit is LTC2270, which has independent dual channels, 16 bits resolution, and a maximum sampling rate of 20MSps.

[0046] In the present invention, the AD acquisition circuit adopts ADC+FPGA+MCU structure, and FPGA controls two ADCs to complete dual-channel spectral data acquisition and data reading, and implements preprocessing such as cumulative averaging and digital filtering inside the FPGA to improve the signal-to-noise ratio while reducing data traffic. A dual-port RAM is constructed inside the FPGA using on-chip RAM, and the preprocessed spectral data is stored here. The microprocessor directly takes out the data from the FPGA through the FSMC interface and sends it through the network interface, which reduces the waiting time for sending data and improves data throughput efficiency. The model of the digital-to-analog converter of the AD acquisition circuit is LTC2270, and the FPGA model of the AD acquisition circuit is EP4CE22. About 600KB of on-board storage can be used for data caching, and 132 hardware multipliers are built in to complete digital signal processing functions such as filtering. The MCU model of the AD acquisition circuit is the STM23H7 series chip, with a main frequency of 480MHz, 1MB of high-speed RAM on chip, and SPI, I 2 C, USART, FSMC, Ethernet MAC and other peripheral communication interfaces, and the on-chip integrated multi-channel ADC can be used for the collection of status parameters.

[0047] In a specific implementation, the signal generation circuit outputs the multi-channel frequency modulation signals to multiple optical switches, and outputs the multiple sawtooth signals to multiple local oscillator lasers.

[0048] When implementing it, Figure 1 The number of the multiple fiber collimators, multiple optical switches, multiple amplifiers, multiple narrow-band optical filters, multiple local oscillator lasers and multiple fiber combiners is three, which are used to measure the entire atmospheric carbon dioxide, methane and water vapor respectively.

[0049] Figure 2 This is a high-resolution spectrum signal diagram of the transmittance of carbon dioxide, methane and water vapor in the entire atmosphere measured synchronously by the single-channel laser heterodyne spectrometer of the present invention.

[0050] The local oscillator laser is a narrow linewidth (2MHz) semiconductor laser with different wavelengths. The central wavelengths are 1522nm, 1572nm, and 1654nm respectively. The high-precision FPGA signal generation circuit generates a sawtooth scanning signal, so that the local oscillator laser light wavelength sweeps across the absorption spectral line positions of gases such as H2O, CO2, and CH4.

[0051] The three optical switches respectively modulate the intensity of the sunlight coupled into the optical fiber, and the modulation frequencies of the first modulation frequency signal, the second modulation frequency signal and the third modulation frequency signal are respectively f 1 , f 2 , f 3The input optical fibers of the three optical switches are respectively connected to the output optical fibers of the optical fiber collimator, and the output optical fibers are respectively connected to the input optical fibers of the three semiconductor optical amplifiers, and the output end of the semiconductor optical amplifier is connected to the input optical fiber of the narrow-band optical filter, and the output optical fibers of the three narrow-band optical filters and the output optical fibers of the three local oscillator lasers are respectively connected to the input optical fibers of the three optical fiber combiners, so that the local oscillator lasers of different wavelengths and the intensity-modulated sunlight are combined.

[0052] The optical fibers at the output ends of the three fiber combiners are connected to the optical fibers at the input ends of the wavelength division multiplexer for low-loss beam combining again. Finally, the optical fiber at the output end of the wavelength division multiplexer is connected to a high-speed photodetector. The combined light of the local oscillator laser and the sunlight will be optically mixed on the photosensitive surface of the detector to produce a difference frequency signal. The input end of the RF processing circuit is connected to the output end of the photodetector, and is transmitted to the RF processing circuit and the Schottky diode for filtering, signal amplification, power detection and other processing. Finally, the Schottky diode outputs an analog signal of the difference frequency signal power. The high-speed A / D sampling circuit is connected to the output end of the Schottky diode, collects the power signal at high speed and converts it into a digital signal and uploads it to the host computer, and transmits it to the host computer spectral processing software through serial communication to synchronously demodulate the entire atmospheric H2O, CO2, and CH4 transmittance spectrum data, and finally invert the atmospheric column concentration and vertical profile of the target gas molecules.

[0053] A single-channel laser heterodyne spectrometer of the present invention has the following characteristics.

[0054] 1. Compared with the existing atmospheric multi-component laser heterodyne spectroscopy detection technology, the frequency division multiplexing technology and the signal light intensity modulation laser heterodyne spectroscopy technology are combined. By modulating the intensity of multiple beams of sunlight at different frequencies, the simultaneous detection of multiple gas components in the atmosphere with a single heterodyne channel is realized.

[0055] 2. Using semiconductor optical amplifiers or fiber amplifiers to amplify the power of sunlight solves the problem of optical power limitation of the local oscillator laser participating in the heterodyne beat frequency process under the detector saturation power threshold, and ensures the signal-to-noise ratio of the heterodyne signal.

[0056] 3. A digital phase-locked amplifier programmed by a host computer software is used to simultaneously demodulate heterodyne signals of multiple modulation frequencies, thereby realizing synchronous detection of atmospheric multi-component greenhouse gases and simplifying the system structure. The present invention adopts a conventional phase-locked method or algorithm, which does not require special processing, makes calculations simpler in software design, and data can be reused, making the present invention more versatile.

[0057] The single-channel laser heterodyne spectrometer of the present invention simplifies the number of laser heterodyne spectrum detection channels used for detecting the column concentration / profile of multi-component greenhouse gases in the entire atmosphere, while ensuring the measurement accuracy of the system, and improves the synchronization and time resolution of greenhouse gas observation data.

[0058] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A single-channel laser heterodyne spectrometer, characterized in that: It includes multiple fiber collimators, multiple optical switches, multiple amplifiers, multiple narrow-band optical filters, multiple local oscillator lasers, multiple fiber combiners, a signal generation circuit, a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, an AD acquisition circuit and a host computer; the number of the multiple fiber collimators, multiple optical switches, multiple amplifiers, multiple narrow-band optical filters, multiple local oscillator lasers and multiple fiber combiners is the same; The solar tracker receives sunlight and introduces the sunlight into multiple fiber combiners through multiple optical switches, multiple amplifiers, and multiple narrow-band optical filters in sequence; the multiple fiber combiners are connected to a host computer through a single wavelength division multiplexer, a single high-speed photodetector, a radio frequency processing circuit, a Schottky diode, and an AD acquisition circuit in sequence; the sawtooth signal generated by the signal generation circuit is input into the multiple fiber combiners through multiple local oscillator lasers; and the multi-channel frequency modulation signals generated by the signal generation circuit are respectively input into the multiple optical switches.

2. A single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The input ends of the plurality of fiber optic collimators are connected to the output ends of the sun tracker, and the sun tracker introduces sunlight into the plurality of fiber optic collimators; The output ends of the plurality of optical fiber collimators are connected to the input ends of the plurality of optical switches through optical fibers and correspond one to one, and the sunlight is coupled into the plurality of optical fibers respectively and then introduced into the plurality of optical switches; The output ends of the plurality of optical switches are connected to the input ends of the plurality of amplifiers in a one-to-one correspondence and are connected to the plurality of frequency modulation signal output ends of the signal generating circuit in a one-to-one correspondence; The output ends of the plurality of amplifiers are connected to the input ends of the plurality of narrow-band optical filters in a one-to-one correspondence; The plurality of sawtooth signal output terminals of the signal generating circuit are connected to the input terminals of the plurality of local oscillator lasers; The output ends of the multiple local oscillator lasers are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence, and the output ends of the multiple narrow-band optical filters are connected to the input ends of the multiple fiber combiners in a one-to-one correspondence; The output ends of the multiple optical fiber combiners are all connected to the input end of the single wavelength division multiplexer; The output end of the single wavelength division multiplexer is connected to the input end of the single high-speed photodetector; The output end of the single high-speed photodetector is connected to the input end of the radio frequency processing circuit; The output end of the radio frequency processing circuit is connected to the input end of the Schottky diode; The output end of the Schottky diode is connected to the input end of the AD acquisition circuit; The output end of the AD acquisition circuit is connected to the acquisition signal input end of the host computer; The spectrum processing software in the host computer analyzes and processes the collected signals to calculate the vertical profile / column concentration of greenhouse gases.

3. A single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The multiple local oscillator lasers are all narrow linewidth semiconductor lasers.

4. A single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The wavelengths of the multiple local oscillator lasers are different.

5. The single-channel laser heterodyne spectrometer according to claim 1, characterized in that: There are three local oscillator lasers, and the wavelengths of the three local oscillator lasers are 1522nm, 1564nm and 1572nm respectively.

6. A single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The plurality of narrow-band optical filters have different central wavelengths.

7. The single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The signal generating circuit is a high-precision FPGA signal generating circuit.

8. The single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The plurality of amplifiers are semiconductor optical amplifiers or optical fiber amplifiers.

9. The single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The AD acquisition circuit includes a digital-to-analog converter LTC2270.

10. The single-channel laser heterodyne spectrometer according to claim 1, characterized in that: The signal generating circuit outputs multi-channel frequency modulation signals to a plurality of optical switches, and outputs a plurality of sawtooth signals to a plurality of local oscillator lasers.

Images