Photoacoustic spectroscopy multi-component gas detection system and method based on fiber intracavity laser

Abstract

The invention discloses a photoacoustic spectroscopy multi-component gas detection system based on optical fiber intracavity laser, comprising a pump source 1, the pump source 1 is connected to a wavelength division multiplexer 1, the wavelength division multiplexer 1 is connected to a C-band erbium-doped optical fiber, the C-band erbium-doped optical fiber is connected to a coupler 1; a pump source 2, the pump source 2 is connected to a wavelength division multiplexer 2, the wavelength division multiplexer 2 is connected to an L-band erbium-doped optical fiber, the L-band erbium-doped optical fiber is connected to a coupler 1; the coupler 1 is connected to a circulator, the circulator is connected to a photoacoustic cell, the circulator is connected to a coupler 2, the coupler 2 is connected to a wavelength division multiplexer 1 and a wavelength division multiplexer 2; the photoacoustic cell is connected to a plurality of fiber gratings arranged in series, the fiber gratings are connected to a PZT actuator, the PZT actuator is connected to a PZT driver, the PZT driver is connected to a signal generating module; the photoacoustic cell is connected to a signal output device. The invention has a simple and reasonable structure, can perform multi-component gas detection, and improves detection sensitivity.

Description

Technical Field

[0001] The invention belongs to the technical field of gas detection, and in particular relates to a photoacoustic spectroscopy multi-component gas detection system and method based on optical fiber intracavity laser. Background Art

[0002] With the progress and development of society, environmental issues have become particularly important. Rapid and accurate gas detection has received widespread attention in all walks of life. As an important part of environmental monitoring, gas detection technology can be used not only in atmospheric gas detection, but also in human daily life, industrial development and aerospace technology. In the construction of my country's aerospace field, aircraft, rockets, etc. need to be strictly tested for trace gases inside and outside before launch to ensure the normal operation of the equipment and the safety of the staff; in the mining and transportation of coal, oil and natural gas, real-time monitoring of combustible gases such as methane and acetylene is also particularly important; at the same time, the emission of harmful gases such as industrial waste gas and automobile exhaust also makes gas detection technology more important. Because these gases are low in content and difficult to detect when mixed in the air, it is planned to study a high-sensitivity photoacoustic spectroscopy multi-component gas detection system and detection method to solve the above technical problems. Summary of the invention

[0003] In order to overcome the above technical problems, the present invention provides a photoacoustic spectroscopy multi-component gas detection system and method based on fiber intracavity laser, constructs a ring cavity fiber laser with a parallel C+L band structure, and sets a variety of fiber gratings in series to achieve multiple wavelength outputs. At the same time, the broadband characteristics of the photoacoustic cell help to use frequency division multiplexing to achieve multi-component demodulation, thereby realizing intracavity multi-component gas detection, and finally achieving the effect of realizing multi-component gas detection and improving detection sensitivity.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A pump source 1, the pump source 1 is connected to a wavelength division multiplexer 1, the wavelength division multiplexer 1 is connected to a C-band erbium-doped optical fiber, the C-band erbium-doped optical fiber is connected to a coupler 1; a pump source 2, the pump source 2 is connected to a wavelength division multiplexer 2, the wavelength division multiplexer 2 is connected to an L-band erbium-doped optical fiber, the L-band erbium-doped optical fiber is connected to a coupler 1; an output end of the coupler 1 is connected to a first port of a circulator, a second port of the circulator is connected to one end of a photoacoustic cell, a third port of the circulator is connected to a coupler 2, and the coupler 2 The photoacoustic cell is connected to a wavelength division multiplexer 1 and a wavelength division multiplexer 2; the other end of the photoacoustic cell is connected to a plurality of fiber gratings arranged in series, the fiber grating is connected to a PZT actuator, the PZT actuator is connected to a PZT driver, the PZT driver is connected to a signal generating module, the pump source 1 and the pump source 2 are both 980nm single-mode pump sources, the wavelength division multiplexer 1 and the wavelength division multiplexer 2 are both 980 / 1550nm wavelength division multiplexers, the pump source 1 is connected to the 980 port of the wavelength division multiplexer 1, the pump source The second coupler is connected to the 980 port of the second wavelength division multiplexer, the second coupler is connected to the 1550 port of the first wavelength division multiplexer and the second wavelength division multiplexer, the first pump source, the first wavelength division multiplexer and the C-band erbium-doped optical fiber output C-band light, the second pump source, the second wavelength division multiplexer and the L-band erbium-doped optical fiber output L-band light, and the two are combined by the first coupler to realize C+L band light output, the wavelength of C+L band light covers 1510nm-1590nm, which contains a variety of gas absorption peaks, and the PZT actuator and PZT driver control light The fiber Bragg grating realizes wavelength scanning and modulation. The laser corresponding to the reflection wavelength of the fiber Bragg grating interacts with the gas in the photoacoustic cell to generate a photoacoustic signal. At the same time, the reflection wavelength of the fiber Bragg grating corresponds to the central wavelength of the gas absorption peak. The signal generation module controls the PZT driver, and then controls the fiber Bragg grating to periodically expand and contract through piezoelectric ceramics to realize wavelength scanning and modulation, and finally realize multi-component gas detection. Since gas detection is to be achieved through second harmonic demodulation technology, the modulation frequency of the fiber Bragg grating should be set to half of the resonance frequency of the photoacoustic cell.

[0006] The light selected by the fiber grating in the C+L band light is divided into two paths by the second coupler and enters wavelength division multiplexer 1 and wavelength division multiplexer 2 respectively, realizing the light path circulation and forming an intracavity laser. The laser cavity has high power density and round-trip characteristics, which can improve the sensitivity of gas detection.

[0007] The output of the photoacoustic cell is connected to a signal output device, the signal output device includes a preamplifier connected to the output end of the photoacoustic cell, the preamplifier is connected to a phase-locked amplifier, the phase-locked amplifier is connected to a signal acquisition system, and the signal acquisition system is connected to a computer; the current signal output by the photoacoustic cell is converted into a voltage signal by the preamplifier and amplified, the phase-locked amplifier demodulates the voltage signal into a second harmonic, the signal acquisition system collects the demodulated data, and then transmits the data to the computer for signal processing and calculation of gas concentration.

[0008] The photoacoustic cell is a resonant photoacoustic cell with a gas buffer cell, which helps to improve the stability of gas detection. It contains a microphone inside to detect the sound wave signal, which is further amplified by the resonance cavity. At the same time, the broadband characteristics of the photoacoustic cell help to realize multi-component demodulation by using frequency division multiplexing.

[0009] The photoacoustic spectroscopy multi-component gas detection method based on optical fiber intracavity laser includes the following steps:

[0010] S1. Start pump source 1 and pump source 2 at the same time. The 980nm light emitted by pump source 1 enters wavelength division multiplexer 1, and then is transmitted to the C-band erbium-doped fiber to output C-band light. The 980nm light emitted by pump source 2 enters wavelength division multiplexer 2, and then is transmitted to the L-band erbium-doped fiber to output L-band light. The two bands of light are combined by coupler 1 to output C+L band light.

[0011] S2. The PZT actuator and PZT driver control the fiber Bragg grating to achieve wavelength scanning and modulation. The laser corresponding to the fiber Bragg grating reflection wavelength interacts with the gas in the photoacoustic cell to generate a photoacoustic signal. At the same time, the fiber Bragg grating reflection wavelength corresponds to the central wavelength of the gas absorption peak. The signal generation module controls the PZT driver, and then controls the fiber Bragg grating to periodically expand and contract to achieve wavelength scanning and modulation.

[0012] S3. After the C+L band light passes through the circulator and the photoacoustic cell, the light reflected by the fiber grating frequency selection is divided into two paths by the second coupler and enters the first wavelength division multiplexer and the second wavelength division multiplexer respectively, realizing the optical path circulation and forming an intracavity laser;

[0013] S4. The wavelength of C+L band light covers 1510nm-1590nm, and the spectral line width can realize multiple gas detection. The C+L band light enters the fiber grating through the circulator and the photoacoustic cell and reflects the multiple narrowband wavelengths required for gas sensing. The light from the circulator passes through the photoacoustic cell, where the light interacts with the gas to realize multiple gas detection;

[0014] S5. The current signal output from the photoacoustic cell is converted into a voltage signal and amplified by a preamplifier, and then demodulated into a second harmonic by a phase-locked amplifier. The data is then collected by a signal acquisition system and finally transmitted to a computer for signal processing and calculation of gas concentration.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention sets a pump source 1, a wavelength division multiplexer 1 and a C-band erbium-doped optical fiber to output C-band light, sets a pump source 2, a wavelength division multiplexer 2 and an L-band erbium-doped optical fiber to output L-band light, and the C-band light and the L-band light are combined by a coupler 1 to realize C+L-band light output, the wavelength of the C+L-band light covers 1510nm-1590nm, and contains a variety of gas absorption peaks, and sets a PZT actuator and a PZT driver to control the fiber grating to realize wavelength scanning and modulation, and the laser corresponding to the reflection wavelength of the fiber grating interacts with the gas in the photoacoustic cell to generate a photoacoustic signal, and at the same time, the reflection wavelength of the fiber grating corresponds to the central wavelength of the gas absorption peak, and sets a signal generation module to control the PZT driver, and then controls the fiber grating to periodically expand and contract through piezoelectric ceramics to realize wavelength scanning and modulation, and finally realize multi-component gas detection;

[0017] 2. In the present invention, the light selected by the fiber grating in the C+L band light is divided into two paths by the second coupler and enters the wavelength division multiplexer 1 and the wavelength division multiplexer 2 respectively, realizing the light path circulation and forming an intracavity laser. The laser cavity has high power density and round-trip characteristics, thereby improving the sensitivity of gas detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is an overall schematic diagram of the present invention;

[0019] Figure 2 It is a schematic diagram of the photoacoustic cell in the present invention. DETAILED DESCRIPTION

[0020] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0021] The photoacoustic spectroscopy multi-component gas detection system based on fiber intracavity laser includes:

[0022] A pump source 1, wherein the pump source 1 is connected to a wavelength division multiplexer 1, wherein the wavelength division multiplexer 1 is connected to a C-band erbium-doped optical fiber, and the C-band erbium-doped optical fiber is connected to a coupler 1; a pump source 2, wherein the pump source 2 is connected to a wavelength division multiplexer 2, wherein the wavelength division multiplexer 2 is connected to an L-band erbium-doped optical fiber, and the L-band erbium-doped optical fiber is connected to a coupler 1; an output end of the coupler 1 is connected to a first port of a circulator, wherein a second port of the circulator is connected to one end of a photoacoustic cell, wherein a third port of the circulator is connected to a coupler 2, and wherein the coupler 2 is connected to the wavelength division multiplexer 1 and the wavelength division multiplexer 2; the other end of the photoacoustic cell is connected to a plurality of fiber gratings arranged in series, wherein the fiber gratings are connected to a PZT actuator, wherein the PZT actuator is connected to a PZT driver, and wherein the PZT driver is connected to a signal generating module; and an output of the photoacoustic cell is connected to a signal output device.

[0023] The pump source 1 and the pump source 2 are both 980nm single-mode pump sources. The wavelength division multiplexer 1 and the wavelength division multiplexer 2 are both 980 / 1550nm wavelength division multiplexers. The pump source 1 is connected to the 980 port of the wavelength division multiplexer 1, the pump source 2 is connected to the 980 port of the wavelength division multiplexer 2, the coupler 2 is connected to the 1550 port of the wavelength division multiplexer 1 and the wavelength division multiplexer 2, and the photoacoustic cell is a resonant photoacoustic cell.

[0024] The signal output device comprises a preamplifier connected to the output end of the photoacoustic cell, the preamplifier is connected to a phase-locked amplifier, the phase-locked amplifier is connected to a signal acquisition system, and the signal acquisition system is connected to a computer.

[0025] The photoacoustic spectroscopy multi-component gas detection method based on optical fiber intracavity laser includes the following steps:

[0026] S1. Start pump source 1 and pump source 2 at the same time. The 980nm light emitted by pump source 1 enters wavelength division multiplexer 1, and then is transmitted to the C-band erbium-doped fiber to output C-band light. The 980nm light emitted by pump source 2 enters wavelength division multiplexer 2, and then is transmitted to the L-band erbium-doped fiber to output L-band light. The two bands of light are combined by coupler 1 to output C+L band light.

[0027] S2. The PZT actuator and PZT driver control the fiber Bragg grating to achieve wavelength scanning and modulation. The laser corresponding to the fiber Bragg grating reflection wavelength interacts with the gas in the photoacoustic cell to generate a photoacoustic signal. At the same time, the fiber Bragg grating reflection wavelength corresponds to the central wavelength of the gas absorption peak. The signal generation module controls the PZT driver, and then controls the fiber Bragg grating to periodically expand and contract to achieve wavelength scanning and modulation.

[0028] S3. After the C+L band light passes through the circulator and the photoacoustic cell, the light reflected by the fiber grating frequency selection is divided into two paths by the second coupler and enters the first wavelength division multiplexer and the second wavelength division multiplexer respectively, realizing the optical path circulation and forming an intracavity laser;

[0029] S4. The wavelength of C+L band light covers 1510nm-1590nm, and the spectral line width can realize multiple gas detection. The C+L band light enters the fiber grating through the circulator and the photoacoustic cell and reflects the multiple narrowband wavelengths required for gas sensing. The light from the circulator passes through the photoacoustic cell, where the light interacts with the gas to realize multiple gas detection;

[0030] S5. The current signal output from the photoacoustic cell is converted into a voltage signal and amplified by a preamplifier, and then demodulated into a second harmonic by a phase-locked amplifier. The data is then collected by a signal acquisition system and finally transmitted to a computer for signal processing and calculation of gas concentration.

[0031] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the above embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. Photoacoustic spectroscopy multi-component gas detection system based on fiber intracavity laser, characterized in that: include: A pump source 1, wherein the pump source 1 is connected to a wavelength division multiplexer 1, wherein the wavelength division multiplexer 1 is connected to a C-band erbium-doped optical fiber, and wherein the C-band erbium-doped optical fiber is connected to a coupler 1; A second pump source, wherein the second pump source is connected to a second wavelength division multiplexer, wherein the second wavelength division multiplexer is connected to an L-band erbium-doped optical fiber, and wherein the L-band erbium-doped optical fiber is connected to a first coupler; The output end of the coupler 1 is connected to the first port of the circulator, the second port of the circulator is connected to one end of the photoacoustic cell, the third port of the circulator is connected to the coupler 2, and the coupler 2 is connected to the wavelength division multiplexer 1 and the wavelength division multiplexer 2; The other end of the photoacoustic cell is connected to a plurality of fiber gratings arranged in series, the fiber gratings are connected to a PZT actuator, the PZT actuator is connected to a PZT driver, and the PZT driver is connected to a signal generating module; The photoacoustic cell output is connected to a signal output device; The pump source 1 and the pump source 2 are both 980nm single-mode pump sources; The signal output device comprises a preamplifier connected to the output end of the photoacoustic cell, the preamplifier is connected to a phase-locked amplifier, the phase-locked amplifier is connected to a signal acquisition system, and the signal acquisition system is connected to a computer.

2. The optical fiber intracavity laser based photoacoustic spectroscopy multi-component gas detection system according to claim 1 is characterized in that: The wavelength division multiplexer 1 and the wavelength division multiplexer 2 are both 980 / 1550nm wavelength division multiplexers.

3. The optical fiber intracavity laser based photoacoustic spectroscopy multi-component gas detection system according to claim 2 is characterized in that: The first pump source is connected to the 980 port of the first wavelength division multiplexer, the second pump source is connected to the 980 port of the second wavelength division multiplexer, and the second coupler is connected to the 1550 ports of the first wavelength division multiplexer and the second wavelength division multiplexer.

4. The photoacoustic spectroscopy multi-component gas detection system based on fiber intracavity laser according to claim 1 is characterized in that: The photoacoustic cell is a resonant photoacoustic cell.

5. A multi-component gas detection method based on photoacoustic spectroscopy using an optical fiber intracavity laser, characterized in that: The photoacoustic spectroscopy multi-component gas detection system based on fiber intracavity laser according to any one of claims 1 to 4 comprises the following steps: S1. Start pump source 1 and pump source 2 at the same time. The 980nm light emitted by pump source 1 enters wavelength division multiplexer 1, and then is transmitted to the C-band erbium-doped fiber to output C-band light. The 980nm light emitted by pump source 2 enters wavelength division multiplexer 2, and then is transmitted to the L-band erbium-doped fiber to output L-band light. The two bands of light are combined by coupler 1 to output C+L band light. S2. The PZT actuator and PZT driver control the fiber Bragg grating to achieve wavelength scanning and modulation. The laser corresponding to the fiber Bragg grating reflection wavelength interacts with the gas in the photoacoustic cell to generate a photoacoustic signal. At the same time, the fiber Bragg grating reflection wavelength corresponds to the central wavelength of the gas absorption peak. The signal generation module controls the PZT driver, and then controls the fiber Bragg grating to periodically expand and contract to achieve wavelength scanning and modulation. S3. After the C+L band light passes through the circulator and the photoacoustic cell, the light reflected by the fiber grating frequency selection is divided into two paths by the second coupler and enters the first wavelength division multiplexer and the second wavelength division multiplexer respectively, realizing the optical path circulation and forming an intracavity laser; S4. The wavelength of C+L band light covers 1510nm-1590nm, and the spectral line width can realize multiple gas detection. The C+L band light enters the fiber grating through the circulator and the photoacoustic cell and reflects the multiple narrowband wavelengths required for gas sensing. The light from the circulator passes through the photoacoustic cell, where the light interacts with the gas to realize multiple gas detection; S5. The current signal output from the photoacoustic cell is converted into a voltage signal and amplified by a preamplifier, and then demodulated into a second harmonic by a phase-locked amplifier. The data is then collected by a signal acquisition system and finally transmitted to a computer for signal processing and calculation of gas concentration.

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