阅读说明：本技术 一种具有分布式测温功能的太赫兹时域光谱和成像系统 (Terahertz time-domain spectroscopy and imaging system with distributed temperature measurement function ) 是由 朱新勇 刘永利 郭永玲 王玉建 张朝惠 初文怡 张磊 管玉超 刘虎 于 2020-06-24 设计创作，主要内容包括：本发明公开了一种具有分布式测温功能的太赫兹时域光谱和成像系统,包括飞秒激光器、一级光纤分路器、太赫兹光谱单元、脉冲光调制单元、分布式光纤传感器单元和信号采集处理单元,一级光纤分路器将飞秒激光器产生的飞秒脉冲激光分为激发光和激励光,激发光传输到太赫兹光谱单元产生携带样品信息的电流信号,激励光经脉冲光调制单元调制为调制脉冲光,调制脉冲光输送到分布式光纤传感器单元产生携带温度信息的模拟信号,信号采集处理单元采集并处理携带样品信息的电流信号和/或携带温度信息的模拟信号。成功将飞秒激光应用于分布式光纤温度传感系统中,提出了完整的飞秒脉冲光调制和管理方案,实现了对飞秒激光器的多系统复用。(The invention discloses a terahertz time-domain spectroscopy and imaging system with a distributed temperature measurement function, which comprises a femtosecond laser, a primary fiber branching unit, a terahertz spectroscopy unit, a pulse light modulation unit, a distributed fiber sensor unit and a signal acquisition and processing unit, wherein the primary fiber branching unit divides femtosecond pulse laser generated by the femtosecond laser into excitation light and excitation light, the excitation light is transmitted to the terahertz spectroscopy unit to generate a current signal carrying sample information, the excitation light is modulated into modulated pulse light by a pulse light modulation unit, the modulated pulse light is transmitted to the distributed fiber sensor unit to generate an analog signal carrying temperature information, and the signal acquisition and processing unit acquires and processes the current signal carrying the sample information and/or the analog signal carrying the temperature information. The femtosecond laser is successfully applied to a distributed optical fiber temperature sensing system, a complete femtosecond pulse light modulation and management scheme is provided, and multi-system multiplexing of the femtosecond laser is realized.)

1. A terahertz time-domain spectroscopy and imaging system with a distributed temperature measurement function is characterized by comprising a femtosecond laser, a primary fiber splitter and a terahertz spectroscopy unit, the terahertz spectrum sensor comprises a pulse light modulation unit, a distributed optical fiber sensor unit and a signal acquisition and processing unit, wherein a first-level optical fiber branching unit divides femtosecond pulse laser generated by a femtosecond laser into excitation light and excitation light, the excitation light is transmitted to a terahertz spectrum unit to generate a current signal carrying sample information, the excitation light is modulated into modulation pulse light by the pulse light modulation unit, the modulation pulse light is transmitted to the distributed optical fiber sensor unit to generate an analog signal carrying temperature information, the signal acquisition and processing unit is respectively connected with the terahertz spectrum unit and the distributed optical fiber sensor unit, and the current signal carrying the sample information and/or the analog signal carrying the temperature information are acquired and processed.

2. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function according to claim 1, wherein the pulse light modulation unit comprises a fiber isolator, a pulse broadening device and an electro-optic modulator, the fiber isolator is connected with a first-stage fiber shunt excitation light output end and used for constraining a laser transmission direction, the pulse broadening device is connected with the fiber isolator and used for quantitatively broadening femtosecond laser pulses and broadening the femtosecond pulses to a nanosecond level, and the electro-optic modulator is connected with the pulse broadening device and used for amplitude modulation of a femtosecond pulse sequence to obtain modulated pulsed light.

3. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function according to claim 2, wherein the distributed optical fiber sensor unit comprises a coarse wavelength division multiplexer, a temperature sensing optical fiber and a photoelectric detector, the coarse wavelength division multiplexer is connected with the electro-optic modulator through a second port, the temperature sensing optical fiber is connected with a first port of the coarse wavelength division multiplexer, the temperature sensing optical fiber modulates transmission of pulse light in the optical fiber to generate anti-stokes light, the anti-stokes light carrying temperature information of different positions of the optical fiber returns to the coarse wavelength division multiplexer, the photoelectric detector is connected with a third port of the coarse wavelength division multiplexer, and the returned anti-stokes light carrying temperature information of different positions of the optical fiber is subjected to photoelectric conversion under synchronous pulse triggering with an output modulation signal to output an analog signal.

4. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function according to claim 3, wherein the terahertz spectroscopy unit comprises a secondary fiber splitter, a fiber delay line, a modulation bias source, a terahertz emitting antenna and a terahertz detecting antenna, the secondary fiber splitter is connected with an excitation light output end of the primary fiber splitter to divide the excitation light into pump light and detection light, a pump light output end of the secondary fiber splitter is connected with the terahertz emitting antenna, the modulation bias source is connected with the terahertz emitting antenna to generate a bias voltage, a detection light output end of the secondary fiber splitter is connected with the terahertz detecting antenna through the fiber delay line, under the combined action of the pump light and the modulation bias source, the terahertz emitting antenna generates pulse terahertz waves, the terahertz waves are collimated by a free light path and then refocused on the terahertz detecting antenna, meanwhile, the detection light output by the secondary optical fiber branching unit meets the terahertz detection antenna after passing through the optical fiber delay line, free carriers are generated in the photoconductive antenna, the free carriers are migrated under the induction electric field generated by the terahertz detection antenna, and a current signal in direct proportion to the intensity of the terahertz signal is formed.

5. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function according to claim 4, wherein the signal acquisition and processing unit comprises a signal acquisition and data processing unit and a PC, the signal acquisition and data processing unit is connected with the terahertz detection antenna, acquires a current signal proportional to the intensity of the terahertz signal, the signal acquisition and data processing unit is connected with the femtosecond laser, controls the generation of femtosecond pulse laser, is connected with a modulation bias source, controls the generation of bias voltage, is connected with the electro-optic modulator, sends the modulation signal to the electro-optic modulator, is connected with the photoelectric detector, acquires an output analog signal, and is connected with the signal acquisition and data processing unit, and is used for data processing, data processing and data processing of the integrated system, Analysis, visual display and storage. In order to avoid flow intersection among different systems, the signal acquisition and data processing unit comprises two paths of modulation signal outputs and two acquisition channels which work in an asynchronous mode, wherein one path of modulation signal output is connected with the femtosecond laser and the modulation bias source, one acquisition channel is connected with the terahertz detection antenna, the other path of modulation signal output is connected with the electro-optic modulator, and the other acquisition channel is connected with the photoelectric detector.

6. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function as claimed in claim 5, wherein after passing through the primary fiber splitter, the optical power for the terahertz spectroscopy and imaging system is generally not less than 80mw, the optical power for the fiber temperature sensing system is generally not more than 10mw, and the average power after passing through the electro-optic modulator is not more than 2 mw.

7. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function as claimed in claim 6, wherein the extinction ratio parameter of the electro-optic modulator is not less than 35dB to ensure a good signal-to-noise level of the sensing system.

8. The terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function as claimed in claim 7, wherein an optical fiber polarization scrambler is disposed in front of the isolator to convert linearly polarized light into naturally polarized light.

The technical field is as follows:

the invention belongs to the technical field of terahertz spectrum and imaging, and particularly relates to a terahertz time-domain spectrum and imaging system with a distributed temperature measurement function.

Background art:

the all-fiber terahertz time-domain spectroscopy and terahertz imaging system is used as a product with the highest commercialization degree of terahertz technology, has the advantages of low photon energy, special penetrability, fingerprint spectrum characteristics, all-fiber coupling structure flexibility and the like derived from terahertz waves, and has wide application potential in industrial nondestructive testing, process quality control and other scenes. However, the measurement parameters provided by terahertz products cannot completely meet the purpose of quality improvement and efficiency improvement by comprehensive monitoring in the industrial manufacturing process, the performance of a terahertz system is influenced by temperature, certain substances to be detected can show different attributes at different temperatures, the conventional terahertz time-domain spectroscopy system is difficult to directly obtain temperature parameters, and the accuracy of terahertz spectral data lacking temperature correction and indexing needs to be improved. In addition, the high price often becomes a reason for restricting the application and popularization.

Distributed optical fiber sensing technology has grown with the progress of optical fiber technology and optical fiber communication technology as a new sensing technology that has been rapidly developed in recent years. The optical fiber sensor has obvious advantages, and common single-mode optical fibers can stably work under various severe environments such as high temperature and high pressure, electromagnetic radiation, corrosion and the like, and have incomparable great advantages compared with the traditional sensor as the optical fiber sensor is benefited by the huge information capacity of the optical fibers. Among a plurality of optical fiber sensing technologies, a distributed optical fiber temperature sensing system (DTS) is the most mature representative of commercialization, and an optical fiber with the length of 1000m can realize real-time monitoring of at least 1000 temperature points, so that the optical fiber temperature sensing system has good application effects in temperature monitoring in fire safety, electric power, pipelines and production processes. The patent CN103207033A discloses a spectroscopic optical fiber sensing device for simultaneously measuring temperature and strain, wherein incident light generated by a narrow linewidth laser passes through an isolator and then is divided into two branches by the coupler, the first branch is modulated into pulsed light by the pulsed light generating device, and then is amplified by the erbium-doped optical fiber amplifier and then is connected with a first port of the circulator as a pulse pump light, and a second port of the circulator is connected to one end of the sensing optical fiber; the frequency of a second branch is shifted by the frequency shifting device to serve as detection light after frequency shifting to be accessed to the other end of the sensing optical fiber, a third port of the circulator is connected with the photoelectric detector to perform photoelectric conversion, and finally the Brillouin frequency shift quantity of the sensing optical fiber is obtained through the data acquisition card and the computer; the two narrow linewidth lasers are not accessed at the same time and have different wavelengths, and when the narrow linewidth laser works, the narrow linewidth laser under the first wavelength is accessed for measurement, and then the narrow linewidth laser under the second wavelength is accessed for measurement.

The invention content is as follows:

the invention aims to overcome the defects in the prior art, and aims to provide a comprehensive monitoring system capable of simultaneously carrying out terahertz spectrum and imaging and distributed temperature measurement so as to overcome the defects of single measurement parameter and low cost performance of the two current independent systems.

In order to achieve the purpose, the terahertz time-domain spectroscopy and imaging system with the distributed temperature measurement function comprises a femtosecond laser, a first-level optical fiber branching unit, a terahertz spectroscopy unit, a pulse light modulation unit, a distributed optical fiber sensor unit and a signal acquisition and processing unit, wherein the first-level optical fiber branching unit is connected with the femtosecond laser and divides femtosecond pulse laser generated by the femtosecond laser into excitation light and excitation light, the excitation light output end of the first-level optical fiber branching unit is connected with the terahertz spectroscopy unit, the excitation light is transmitted to the terahertz spectroscopy unit to generate a current signal carrying sample information, the excitation light output end of the first-level optical fiber branching unit is connected with the pulse light modulation unit, the excitation light is modulated into modulated pulse light by the pulse light modulation unit, the distributed optical fiber sensor unit is connected with the pulse light modulation unit, and the modulated pulse light is transmitted to the distributed, the signal acquisition and processing unit is respectively connected with the terahertz spectrum unit and the distributed optical fiber sensor unit and is used for acquiring and processing a current signal carrying sample information and/or an analog signal carrying temperature information. Wherein the pulse light modulation unit and the distributed optical fiber sensor unit form a distributed temperature sensing system,

specifically, the pulse light modulation unit comprises an optical fiber isolator, a pulse stretching device and an electro-optical modulator, the optical fiber isolator is connected with a first-level optical fiber shunt excitation light output end and used for constraining the laser transmission direction, the pulse stretching device is connected with the optical fiber isolator and used for quantitatively stretching femtosecond laser pulses to a nanosecond level, and the electro-optical modulator is connected with the pulse stretching device and used for amplitude modulation of a femtosecond pulse sequence to obtain modulated pulse light.

Specifically, the distributed optical fiber sensor unit comprises a coarse wavelength division multiplexer, a temperature sensing optical fiber and a photoelectric detector, wherein the coarse wavelength division multiplexer is connected with an electro-optical modulator, the coarse wavelength division multiplexer is connected with the electro-optical modulator through a second port, the temperature sensing optical fiber is connected with a first port of the coarse wavelength division multiplexer, the transmission of modulation pulse light in the optical fiber is used for generating anti-stokes light, the anti-stokes light carrying temperature information of different positions of the optical fiber returns to the coarse wavelength division multiplexer, the photoelectric detector is connected with a third port of the coarse wavelength division multiplexer, under the trigger of synchronous pulses of output modulation signals, the returned anti-stokes light carrying temperature information of different positions of the optical fiber is subjected to photoelectric conversion, and analog signals are output.

Specifically, the terahertz spectrum unit comprises a secondary optical fiber splitter, an optical fiber delay line, a modulation bias source, a terahertz emission antenna and a terahertz detection antenna, wherein the secondary optical fiber splitter is connected with an excitation light output end of the primary optical fiber splitter and divides the excitation light into pumping light and detection light, a pumping light output end of the secondary optical fiber splitter is connected with the terahertz emission antenna, the modulation bias source is connected with the terahertz emission antenna and is used for generating bias voltage, a detection light output end of the secondary optical fiber splitter is connected with the terahertz detection antenna through the optical fiber delay line, under the combined action of the pumping light and the modulation bias source, the terahertz emission antenna generates pulse terahertz waves, the terahertz waves are collimated by a free light path and then refocused on the terahertz detection antenna, and meanwhile, the detection light output by the secondary optical fiber splitter meets the terahertz detection antenna through the optical fiber delay line, free carriers are generated in the photoconductive antenna and migrate under the induced electric field generated by the terahertz detection antenna to form a current signal in direct proportion to the intensity of the terahertz signal.

Specifically, the signal acquisition and processing unit comprises a signal acquisition and data processing unit and a PC, wherein the signal acquisition and data processing unit is connected with the terahertz detection antenna and is used for acquiring a current signal in direct proportion to the intensity of the terahertz signal, the signal acquisition and data processing unit is connected with the femtosecond laser and is used for controlling the generation of femtosecond pulse laser, the signal acquisition and data processing unit is connected with a modulation bias voltage source and is used for controlling the generation of bias voltage, the signal acquisition and data processing unit is connected with the electro-optical modulator and is used for sending the modulation signal to the electro-optical modulator, the signal acquisition and data processing unit is connected with the photoelectric detector and is used for acquiring an output analog signal, and the PC is connected with the signal acquisition and data processing unit and is used for data processing, analysis, visual display and storage of the integrated system. In order to avoid flow intersection among different systems, the signal acquisition and data processing unit comprises two paths of modulation signal outputs and two acquisition channels which work in an asynchronous mode, wherein one path of modulation signal output is connected with the femtosecond laser and the modulation bias source, one acquisition channel is connected with the terahertz detection antenna, the other path of modulation signal output is connected with the electro-optic modulator, and the other acquisition channel is connected with the photoelectric detector.

In particular, the photodetector is an APD detector.

Further, after passing through the first-stage optical fiber splitter, the optical power for the terahertz spectrum and the imaging system is generally not less than 80mw, the optical power for the optical fiber temperature sensing system is generally not more than 10mw, and the average power after passing through the electro-optical modulator is not more than 2 mw.

Further, in order to ensure a good signal-to-noise level of the sensing system, the extinction ratio parameter of the electro-optical modulator is not less than 35 dB.

Further, an optical fiber polarization scrambler is arranged in front of the isolator 4 to convert the linearly polarized light into naturally polarized light.

Compared with the prior art, the invention has the following beneficial effects:

1. the temperature of a substance to be measured is obtained through the temperature sensing optical fiber, the terahertz spectrum and imaging system can realize multidimensional imaging of the measured object added with thermodynamic diagram, can be used as the spectrum analysis auxiliary parameter input of a temperature sensitive sample, provides more parameters for sample analysis, and enables the terahertz spectrum and the imaging system to measure more accurately

2. The femtosecond laser is successfully applied to the distributed optical fiber temperature sensing system, a complete femtosecond pulse light modulation and management scheme is provided, multi-system multiplexing of the femtosecond laser is realized, the problem that the femtosecond laser is difficult to be directly applied to the optical fiber temperature sensing system is solved, and the femtosecond laser is beneficial to saving resources and reducing energy consumption while achieving richer system functions.

3. The integration of the optical fiber integration terahertz time-domain spectrum and imaging system and the distributed optical fiber temperature sensing system is realized, the sharing of key resources is realized, the multi-parameter output terahertz system is formed, the more accurate measurement is favorably realized, the requirement of comprehensive monitoring is met, and the applicability of a wider application scene is realized.

Description of the drawings:

FIG. 1 is a structural schematic diagram of a terahertz time-domain spectroscopy and imaging system with a distributed temperature measurement function according to the present invention.

The specific implementation mode is as follows:

the invention is further illustrated by the following specific examples in combination with the accompanying drawings.