CN101936885B - Optical fiber transceiver integrated air differential optical absorption spectroscopy (DOAS) measuring system - Google Patents

Abstract

An optical fiber transceiver integrated air differential absorption spectrum measurement system. It solves the problems of low spectrum utilization efficiency and difficulties in instrument adjustment and optical path alignment in existing typical DOAS systems. The measurement system of the present invention includes a point light source, a telescope and a spectrometer, and also includes a transceiver-integrated structure optical fiber bundle composed of a transmitting optical fiber and a receiving optical fiber with a common end of the transmitting and receiving optical fiber. The spectrum emitted by the point light source is emitted from one end of the transmitting fiber through the common end of the transmitting and receiving optical fiber, collimated by the spherical reflector in the telescope, and then reflected in the original direction after reaching the corner cube, and then focused by the spherical reflector again into the common end of the transmitting and receiving optical fiber. Finally, after exiting from the other end of the receiving fiber, it is imported into a spectrometer for spectral detection. Compared with the typical DOAS system, this system reduces two flat mirrors, avoids the shielding of the flat mirrors during the beam transmission process, improves the efficiency of spectrum utilization, and simplifies the instrument adjustment and centering process.

Description

Optical Fiber Transceiver Integrated Air Differential Absorption Spectroscopy Measurement System

【Technical field】：

The invention relates to a differential absorption spectrum air quality monitoring system, in particular to a monitoring system for measuring trace gas in the air.

【Background technique】:

Air pollution destroys the ecosystem and causes great harm to human health. Therefore, it is necessary to monitor various air pollutants first. The monitoring instruments in many cities in my country adopt point sampling, which can only understand the air pollution situation in the sampling space of the monitoring point and the average condition during the sampling period, and the temporal and spatial representation is poor. The telemetry technology using differential absorption spectroscopy (DOAS) is becoming an ideal tool for environmental pollution monitoring due to its large-scale, multi-component detection, and continuous real-time online measurement methods. Using DOAS technology can simultaneously monitor several pollutants in the same spectral absorption band, which can realize complete non-contact online automatic monitoring; the instrument has high sensitivity and low monitoring concentration; the monitoring range can reach hundreds of meters or even thousands of meters, and can reflect an area The average pollution degree, the monitoring results are more representative than single-point monitoring. DOAS technology is the development direction of conventional online monitoring technology for air quality pollution indicators.

Currently widely used DOAS systems are generally based on the Cassegrain telescope structure. In this structure, the spectrum emitted by the xenon lamp is collimated by the reflector into a parallel light output, and after passing through an optical path of hundreds of meters or even thousands of meters, it is reflected by the corner cube prism at the other end and the light is converged and coupled by the receiving end. After entering the optical fiber, the absorption spectrum is detected by a spectrometer, as shown in Figure 1. In Figure 1, the continuous spectrum emitted by the point light source (xenon lamp) 1 is reflected by the plane reflector 2 at an angle of 45° to the optical axis and then irradiates on the spherical reflector 3, and then irradiates in the distance after being reflected by the spherical reflector 3 on the corner cube prism 4. The corner cube prism 4 reflects the light irradiated on it along the original path, passes through the spherical mirror 3 and the plane mirror 5 in sequence, and finally gathers it at the receiving point, receives it by the optical fiber, and sends it to the spectrometer for analysis.

This kind of DOAS system based on the Cassegrain telescope structure, because the light is blocked by the mirror many times, the spectrum utilization efficiency is low, and the instrument adjustment and optical path alignment are difficult.

【Invention content】：

The purpose of the present invention is to solve the problems of low spectrum utilization efficiency and difficulty in instrument adjustment and optical path alignment in the existing DOAS system, and provide an air differential absorption spectrum measurement system integrated with optical fiber transceiver.

The optical fiber transceiver integrated air differential absorption spectrum measurement system provided by the present invention includes a point light source, a telescope and a spectrometer, and the system also includes a transceiver optical fiber bundle with a common end of the transceiver optical fiber, which is composed of a transmitting optical fiber and a receiving optical fiber. The spectrum emitted by the point light source is first coupled to one end of the transmitting fiber in the optical fiber bundle with integrated transceiver structure, and then emitted through the other end of the transmitting fiber, which is the common end of the transmitting and receiving fiber, collimated by the spherical mirror in the telescope, and passes through an open atmosphere , reaching the corner cube prism at the other end of the telescope’s optical path, and then reflected in the original direction, the reflected light carrying the pollution gas information in the atmosphere returns along the original direction, and is focused by the spherical reflector in the telescope again into the common end of the transceiver optical fiber, and finally passes through the After the other end of the receiving fiber exits, it is imported into a spectrometer for spectral detection.

The common end of the transmitting and receiving optical fiber in the optical fiber bundle of the integrated transceiver structure is located on the optical axis of the telescope, assuming that the radius of the spherical reflector is R, the distance from the common end of the transmitting and receiving optical fiber to the spherical reflector is 1/2R.

The common end of the transmitting and receiving optical fiber in the integrated optical fiber bundle of the transmitting and receiving structure can be installed on a three-dimensional mobile platform and can be adjusted in three dimensions.

Advantages and positive effects of the present invention: In the transceiver integrated air differential absorption spectrum measurement system provided by the present invention, the spectrum transceiver adopts an integrated optical fiber bundle with a common port, and there is only one reflective spherical mirror in the telescope, which is different from the existing typical structure based on Cassegrain telescope Compared with the existing DOAS system, two flat mirrors are reduced, which avoids the blocking of the flat mirror during the transmission of the beam, and improves the spectral utilization efficiency. At the same time, in the process of adjustment and alignment, the system only needs to perform three-dimensional adjustment on the common end of the integrated optical fiber bundle, which simplifies the instrument adjustment and alignment process. The adjustment process can adopt a three-dimensional electric micro-adjustment structure, which can improve automation. degree.

[Description of drawings]:

Figure 1 is a schematic diagram of the existing typical DOAS system structure based on the Cassegrain telescope structure;

Fig. 2 is a schematic diagram of an optical fiber transceiver integrated air differential absorption spectrum measurement system provided by the present invention;

Fig. 3 is a schematic diagram of the structure of the transceiver-integrated optical fiber bundle.

【Detailed ways】:

Fig. 2 shows the optical fiber transceiver integrated air differential absorption spectroscopy measurement system provided by the present invention, which includes a point light source (xenon lamp) 6, a telescope and a spectrometer (not shown) that can emit a wide spectrum structure. Wherein the telescope includes: a spherical reflector 9, and a corner cube prism 10 at the other end of the optical path of the telescope. In addition, the system also includes a transceiver-integrated optical fiber bundle structure (as shown in Figure 3), which is composed of a transmitting optical fiber 12 and a receiving optical fiber 13, one end of which is fixed together to become the common end 8 of the transmitting and receiving optical fiber, which is located at the telescope On the optical axis, assuming that the radius of the spherical reflector 9 is R, the distance between the common end of the transmitting and receiving optical fiber and the spherical reflecting mirror is 1/2R, and the common end of the transmitting and receiving optical fiber can be installed on an existing three-dimensional electric mobile platform and can be carried out Three-dimensional adjustment.

During detection, the spectrum emitted by the xenon lamp 6 first enters the incident port 7 of the emission fiber 12 after being coupled, and is emitted from the other end of the emission fiber, that is, the common end 8 of the transceiver fiber, collimated by the spherical mirror 9 in the telescope, and passes through a section The open atmosphere reaches the corner cube prism 10 at the other end of the optical path of the telescope, and is then reflected in the original direction, and the reflected light carrying the information of the polluted gas in the atmosphere returns along the original direction, and is focused by the spherical reflector 9 in the telescope again into the transceiver optical fiber The common end 8 finally exits through the other port 11 of the receiving optical fiber 13 and then is introduced into a spectrometer for spectrum detection. The spectrometer can invert the concentration of trace gases in the air according to the characteristic absorption spectrum of the gas.

Claims (2)

1. An optical fiber transceiver integrated air differential absorption spectrum measurement system, the system includes a point light source, a telescope and a spectrometer, it is characterized in that the system also includes a transceiver integrated structure optical fiber with a common end of the transceiver optical fiber made of a transmitting optical fiber and a receiving optical fiber The spectrum emitted by the point light source is first coupled to one end of the transmitting fiber in the optical fiber bundle with integrated transceiver structure, and then emitted through the other end of the transmitting fiber, that is, the common end of the transmitting and receiving fiber, and collimated by the spherical mirror in the telescope. Through an open atmosphere, it reaches the corner cube prism at the other end of the telescope’s optical path, and is reflected in the original direction. The reflected light carrying the pollution gas information in the atmosphere returns along the original direction, and is focused by the spherical mirror in the telescope again into the transceiver optical fiber. The common end is finally imported into the spectrometer for spectral detection after the other end of the receiving optical fiber exits; The distance between the fiber common end and the spherical reflector is 1/2R. 2. The optical fiber transceiver integrated air differential absorption spectroscopy measurement system according to claim 1, characterized in that the common end of the transceiver optical fiber in the transceiver integrated structural fiber bundle is installed on a three-dimensional mobile platform and can be adjusted in three dimensions.

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