CN111912810A - Strong-interference-resistant optical fiber methane gas concentration measuring device and measuring method - Google Patents

Abstract

The invention discloses an anti-strong-interference optical fiber methane gas concentration measuring device and a measuring method. The transmitter comprises a processor, a driving module, a light source, a temperature control module, an optical circulator, an optical switch, two photoelectric converters, a photoelectric balance detector, analog binarization, two multipliers, an analog-to-digital converter and a data sending module. The accurate positioning of the position of the methane gas absorption peak in the return signal of the sensing probe is realized by utilizing an electric balance detector, analog binarization and a multiplier, the equivalent intersection point of light intensity curves returned by the sensing probe and a methane gas sealed air chamber is utilized to dynamically lock wavelength areas on two adjacent sides of the methane absorption peak, and the serious reduction of measurement precision caused by the overlapping of the absorption spectral lines of methane gas molecules and the absorption spectral lines of water vapor and other hydrocarbons in a strong interference environment is eliminated.

Description

Optical fiber methane gas concentration measuring device and measuring method with strong interference resistance

technical field

The invention belongs to the technical field of gas concentration measurement, and in particular relates to an optical fiber methane gas concentration measurement device and a measurement method against strong interference, which can realize the measurement of methane gas concentration in a strong interference environment.

Background technique

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

Optical fiber methane gas concentration measurement is usually based on the principle of spectral absorption, comprehensively using Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology, according to the Lambert-Beer law, by detecting the attenuation of light intensity to obtain methane gas concentration. Among them, the spectral absorption of gas molecules refers to the phenomenon that photons in a certain wavelength range are absorbed by gas molecules. Methane molecules have multiple absorption lines in the mid-infrared and near-infrared bands. In order to be suitable for transmission in ordinary silica fibers, the absorption spectrum near 1654 nm is usually selected as the working wavelength of the sensing system. When light passes through the gas under test containing methane molecules, photons of specific wavelengths are absorbed by the methane molecules. Therefore, after the light passes through the measured gas, the light intensity is attenuated, and the degree of attenuation is linearly related to the concentration of methane gas. The gas sensing system based on spectral absorption can indirectly obtain the methane concentration value of the measured gas by measuring the attenuation of light intensity.

Tunable semiconductor laser spectral absorption technology mainly uses the narrow linewidth and wavelength of the tunable semiconductor laser to change with the injection current. By modulating the wavelength of the laser, the wavelength of the laser scans the absorption peak of the gas molecule to be measured. The Lambert-Beer law enables gas molecules to absorb the modulated laser light, so that the concentration of gas molecules can be measured according to the amount of absorption. The physical meaning of the Lambert-Beer law is that when a beam of parallel monochromatic light vertically passes through a uniform non-scattering light-absorbing material, such as methane gas, its absorbance, that is, the attenuation of light intensity, is proportional to the concentration of the light-absorbing material.

The inventors found that due to the absorption lines of methane gas molecules, the interaction with water vapor, other hydrocarbons such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ) The absorption lines have many overlapping regions. Therefore, when the optical fiber methane gas concentration measurement system is used in some special environments with strong interference, such as underground urban integrated pipe gallery with gas pipelines, gas stations, gas stations, etc., the measurement results will be greatly affected by other gas components . Furthermore, the absorption lines of methane gas molecules are very different from those of water vapor, other hydrocarbons such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), and butane (C ₄ H ₁₀ ) Approximately, this effect cannot be eliminated using traditional differential measurements.

SUMMARY OF THE INVENTION

In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide an optical fiber methane gas concentration measuring device and measuring method that are resistant to strong interference.

In order to solve the above technical problems, the following one or more embodiments of the present invention provide the following technical solutions:

In the first aspect, the present invention provides an optical fiber methane gas concentration measurement device with strong interference resistance, comprising: a detection module, a transmitter and an alarm controller which are signally connected in sequence;

Wherein, the detection module includes at least one sensing probe and a gas-sealed air chamber, and both the sensing probe and the gas-sealed air chamber are connected to the optical circulator of the transmitter through an optical fiber;

In the transmitter:

The processor, the driving module, the light source and the optical circulator are signally connected in sequence;

The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter, and the processor are sequentially connected in signals, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel;

The optical switch, the photoelectric converter 1 and the multiplier 1 are signally connected in sequence;

The optical circulator is respectively connected with the optical balance detector and the photoelectric converter 2 signal;

The optical switch and the data sending module are signal-connected with the processor, and the data sending module is signal-connected with the data receiving module of the alarm controller.

In a second aspect, an optical fiber methane gas concentration measurement method with strong interference resistance is provided, comprising the following steps:

The light source generates a continuous optical signal under the excitation of the ramp signal of the driving module, and the continuous optical signal covers the absorption peak of methane gas;

The optical circulator receives the continuous optical signal of the light source, divides it into N+1 channels, and transmits it to each sensing probe and the gas-sealed gas chamber through the optical fiber; transmits the optical signal reflected by the sensing probe to the optical switch, and sequentially passes through the optical switch. Transmit each optical signal to the photoelectric balance detector; transmit the optical signal reflected back from the gas-sealed gas chamber to the photoelectric balance detector;

The photoelectric balance detector converts two optical signals into one electrical signal and outputs it to analog binarization;

The analog binarization outputs the analog electrical signal of constant voltage between the two peaks before and after the electrical signal, and outputs the analog electrical signal of 0V outside the two peak points; the multiplier 1 and the multiplier 2 receive the analog electrical signal;

The photoelectric converter 1 receives the optical signal returned by one sensor probe transmitted by the optical switch, and outputs it to the multiplier 1;

The photoelectric converter 2 receives the optical signal returned by the methane gas sealed gas chamber, and outputs it to the multiplier 2;

The multiplier 1 and the multiplier 2 transmit the electrical signal whose optical wavelength range is on the adjacent two sides of the methane absorption peak to the analog-to-digital converter;

The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor;

The processor uses the digital quantity obtained by the optical signal reflected from the gas-sealed gas chamber as a reference, and calibrates the digital quantity obtained by the optical signal returned by the sensor probe, and calculates the methane gas concentration value;

The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

Compared with the prior art, the above one or more technical solutions of the present invention have achieved the following beneficial effects:

The optical fiber methane gas concentration measurement method and device against strong interference are composed of an alarm controller, a transmitter, a methane gas sealed gas chamber and a sensing probe. The alarm controller and transmitter are packaged in the main box and placed in the monitoring room, office and other safe areas; the methane gas sealing chamber and the sensing probe are placed in the dangerous area where the methane gas may leak; the methane gas sealing chamber is sealed with standard The concentration of methane gas is used to return the light intensity curve with the correct absorption peak position; the sensing probe is used to measure the concentration of methane gas at close range. A passive long-distance fiber optic connection is used between the main unit and the probe.

The transmitter includes processor, drive module, light source, temperature control module, optical circulator (1*(N+1)*(N+1)), optical switch (1*N), two photoelectric converters, photoelectric Balanced detector, analog binarization, two multipliers, analog-to-digital converter and data transmission module. The photoelectric balance detector, analog binarization and multiplier are used to realize the accurate positioning of the absorption peak position of methane gas in the return signal of the sensing probe, and the dynamic locking is carried out by using the equivalent intersection point of the light intensity curve returned by the sensing probe and the methane gas sealed chamber. The wavelength region on the adjacent two sides of the methane absorption peak, eliminates the absorption spectrum of methane gas molecules and water vapor, other hydrocarbons (such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) in a strong interference environment and butane (C ₄ H ₁₀ )), resulting in a serious drop in measurement accuracy.

The optical fiber methane gas concentration measuring method and device against strong interference use infrared light signals to measure the methane gas concentration. Its signal transmission medium (optical fiber) and probe are completely passive, no power supply, no heating or burning phenomenon, and can be placed in a dangerous position close to the methane gas leakage area, which solves the safety and monitoring requirements of traditional methane gas alarm devices. inherent contradiction.

The optical fiber methane gas concentration measurement method and device for strong interference resistance utilizes the intensity change of the infrared light signal to realize the detection of the methane gas concentration, there is no probe poisoning, the working life is prolonged, and the maintenance cost is reduced.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention.

Fig. 1 is the overall structure schematic diagram of the embodiment of the present invention;

2 is a schematic structural diagram of an alarm controller according to an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a transmitter according to an embodiment of the present invention.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

In the first aspect, the present invention provides an optical fiber methane gas concentration measurement device with strong interference resistance, comprising: a detection module, a transmitter and an alarm controller which are signally connected in sequence;

Wherein, the detection module includes at least one sensing probe and a gas-sealed air chamber, and both the sensing probe and the gas-sealed air chamber are connected to the optical circulator of the transmitter through an optical fiber;

In the transmitter:

The processor, the driving module, the light source and the optical circulator are signally connected in sequence;

The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter, and the processor are sequentially connected in signals, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel;

The optical switch, the photoelectric converter 1 and the multiplier 1 are signally connected in sequence;

The optical circulator is respectively connected with the optical balance detector and the photoelectric converter 2 signal;

The optical switch and the data sending module are signal-connected with the processor, and the data sending module is signal-connected with the data receiving module of the alarm controller.

In some embodiments, the transmitter further includes a temperature control module connected to the light source. It is used to control the temperature of the light source, so that the temperature of the light source is constant, and the wavelength and power of the optical signal are prevented from being affected by changes in the ambient temperature.

In some embodiments, the optical fibers are passive long distance transmission fibers.

In some embodiments, the alarm controller is provided with a data receiving module, a display module, a relay group and a power supply module, and the display module, the relay group and the power supply module are all connected to the data receiving module.

Further, the power module is connected with the transmitter. Provide power to the transmitter.

Further, the alarm controller further includes a button module.

Further, the alarm controller also includes a sound and light alarm, an indicator light and a fan, all of which are connected to the relay group.

Further, the indicator lights include a running indicator light, a fault indicator light and a power indicator light.

In a second aspect, an optical fiber methane gas concentration measurement method with strong interference resistance is provided, comprising the following steps:

The light source generates a continuous optical signal under the excitation of the ramp signal of the driving module, and the continuous optical signal covers the absorption peak of methane gas;

The optical circulator receives the continuous optical signal of the light source, divides it into N+1 channels, and transmits it to each sensing probe and the gas-sealed gas chamber through the optical fiber; transmits the optical signal reflected by the sensing probe to the optical switch, and sequentially passes through the optical switch. Transmit each optical signal to the photoelectric balance detector; transmit the optical signal reflected back from the gas-sealed gas chamber to the photoelectric balance detector;

The photoelectric balance detector converts two optical signals into one electrical signal and outputs it to analog binarization;

The analog binarization outputs the analog electrical signal of constant voltage between the two peaks before and after the electrical signal, and outputs the analog electrical signal of 0V outside the two peak points; the multiplier 1 and the multiplier 2 receive the analog electrical signal;

The photoelectric converter 1 receives the optical signal returned by one sensor probe transmitted by the optical switch, and outputs it to the multiplier 1;

The photoelectric converter 2 receives the optical signal returned by the methane gas sealed gas chamber, and outputs it to the multiplier 2;

The multiplier 1 and the multiplier 2 transmit the electrical signal whose optical wavelength range is on the adjacent two sides of the methane absorption peak to the analog-to-digital converter;

The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor;

The processor uses the digital quantity obtained by the optical signal reflected from the gas-sealed gas chamber as a reference, and calibrates the digital quantity obtained by the optical signal returned by the sensor probe, and calculates the methane gas concentration value;

The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

In some embodiments, the wavelength of the absorption peak of methane gas is 1654 nm.

In some embodiments, the constant voltage analog electrical signal is a 1V analog electrical signal.

Example

As shown in Figure 1, the anti-strong interference optical fiber methane gas concentration measurement device is composed of an alarm controller, a transmitter, a methane gas sealed gas chamber and a sensing probe. The alarm controller and transmitter are packaged in the main box and placed in the monitoring room, office and other safe areas; the methane gas sealing chamber and the sensing probe are placed in the dangerous area where the methane gas may leak; the methane gas sealing chamber is sealed with standard The concentration of methane gas is used to return the light intensity curve with the correct absorption peak position; the sensing probe is used to measure the concentration of methane gas at close range. A passive long-distance fiber optic connection is used between the main unit and the probe.

As shown in Figure 2, the alarm controller is divided into a data receiving module, a display module, a key module, a relay module, a sound and light alarm module and a power supply module according to functions. The data receiving module receives the measurement data of methane gas concentration; the display module displays the methane gas concentration value, alarm threshold, alarm and fault information; the button module is used to set the alarm threshold; On-off control of running lights and fault lights, as well as switch control of peripheral sound and light alarms and fans. The power module is used to power the alarm controller and transmitter.

As shown in Figure 3, the transmitter includes a processor, a drive module, a light source, a temperature control module, an optical circulator (1*(N+1)*(N+1)), an optical switch (1*N), two A photoelectric converter, photoelectric balance detector, analog binarization, two multipliers, analog-to-digital converter and data transmission module.

The processor controls the driving module to generate a suitable driving current signal, and receives the digital signal sent by the analog-to-digital converter, and calculates the methane gas concentration value.

Under the control of the processor, the drive module generates the current signal required to drive the light source. The waveform of the current signal is a ramp signal, so that the wavelength of the continuous light emitted by the light source scans from λ ₁ to λ ₂ , which can cover the wavelength of methane gas at 1654nm. nearby absorption peaks.

Under the excitation of the driving module, the light source generates a continuous optical signal and transmits it to the optical circulator.

The temperature control module is used to control the temperature of the light source, so that the temperature of the light source is constant, and the wavelength and power of the optical signal are prevented from being affected by changes in the ambient temperature.

The optical circulator receives the optical signal of the light source, divides the optical signal into N+1 channels, and transmits it to the N sensing probes and one methane gas sealed gas chamber in the detection area through the long-distance optical fiber. The N optical signals are transmitted to the optical switch, and the 1 optical signal reflected from the methane gas sealed gas chamber is transmitted to the input port 1 of the photoelectric balance detector. Under the control of the processor, the optical switch sequentially transmits the optical signals returned by the N sensing probes to the input port 2 of the optical balance detector.

The optical balance detector converts two input optical signals into one electrical signal output, and when the intensity of the two input optical signals is the same, the output electrical signal amplitude is the highest. In a single ramp cycle, since the wavelength sweeps from λ ₁ to λ ₂ , covering the absorption peak of methane gas near the wavelength of 1654 nm, for the optical signal reflected back from the sealed gas cell of methane gas, the intensity curve experiences from strong to weak and then strong For the optical signal returned by the sensing probe, since the concentration of methane gas in the air is unknown and is affected by the absorption lines of water vapor and other hydrocarbons, when the light wavelength is scanned from λ ₁ to λ ₂ , the intensity curve changes Irregular, but there are always two equivalent intersection points with the optical signal intensity curve reflected back from the methane gas sealed cell, and the two intersection points must be on the adjacent sides of the methane absorption peak.

The analog binarization receives the electrical signal output by the photoelectric balance detector, outputs an analog electrical signal of 1V between the two peak points before and after, and outputs an analog electrical signal of 0V outside the two peak points, and the output is connected to two multipliers.

The photoelectric converter 1 receives the optical signal returned by the 1-channel sensor probe transmitted by the optical switch, and outputs it to another input port of the multiplier 1 . The photoelectric converter 2 receives the optical signal returned from the methane gas sealed gas chamber, and outputs it to another input port of the multiplier 2 .

Two multipliers, under the control of the high and low levels of the analog binarization output, only output the relevant electrical signals whose optical wavelength range is adjacent to the methane absorption peak to the analog-to-digital converter (the optical wavelength range is not adjacent to the methane absorption peak. The electrical signals output by the two multipliers on both sides are 0V).

The analog-to-digital converter converts the voltage signal to a digital signal for transmission to the processor. The processor calibrates the methane gas concentration corresponding to the digital quantity obtained by the optical signal returned by the sensing probe according to the digital quantity obtained by the optical signal reflected from the methane gas sealed gas chamber as a reference. The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

The optical fiber methane gas concentration measurement method with strong interference resistance specifically includes the following steps:

In the first step, the light source generates a continuous optical signal under the excitation of the ramp signal of the driving module and transmits it to the optical circulator. The wavelength of the continuous light emitted by the light source is scanned from λ ₁ to λ ₂ , which can cover the absorption peak of methane gas near the wavelength of 1654 nm.

In the second step, the optical circulator receives the light signal of the light source, divides it into (N+1) paths and transmits it to the N sensing probes and 1 methane gas sealed gas chamber in the detection area through the long-distance optical fiber, and reflects the sensing probe back at the same time. The N optical signals of the methane gas are transmitted to the optical switch, and the 1 optical signal reflected from the methane gas sealed gas chamber is transmitted to the input port 1 of the photoelectric balance detector. Under the control of the processor, the optical switch sequentially transmits the optical signals returned by the N sensing probes to the input port 2 of the optical balance detector.

In step 3, the optical balance detector converts the two input optical signals into one electrical signal output, and when the two input optical signals have the same intensity, the output electrical signal amplitude is the highest. In a single ramp cycle, since the wavelength sweeps from λ ₁ to λ ₂ , covering the absorption peak of methane gas near the wavelength of 1654 nm, for the optical signal reflected back from the sealed gas cell of methane gas, the intensity curve experiences from strong to weak and then strong For the optical signal returned by the sensing probe, since the concentration of methane gas in the air is unknown and is affected by the absorption lines of water vapor and other hydrocarbons, when the light wavelength is scanned from λ ₁ to λ ₂ , the intensity curve changes Irregular, but there are always two equivalent intersection points with the optical signal intensity curve reflected back from the methane gas sealed cell, and the two intersection points must be on the adjacent sides of the methane absorption peak.

Step 4: The analog binarization receives the electrical signal output by the photoelectric balance detector, outputs an analog electrical signal of 1V between the two peak points before and after, and outputs an analog electrical signal of 0V outside the two peak points, and the output is connected to two multiplier. The photoelectric converter 1 receives the optical signal returned by the 1-channel sensor probe transmitted by the optical switch, and outputs it to another input port of the multiplier 1 . The photoelectric converter 2 receives the optical signal returned from the methane gas sealed gas chamber, and outputs it to another input port of the multiplier 2 . Two multipliers, under the control of the high and low levels of the analog binarization output, only output the relevant electrical signals whose optical wavelength range is adjacent to the methane absorption peak to the analog-to-digital converter (the optical wavelength range is not adjacent to the methane absorption peak. The electrical signals output by the two multipliers on both sides are 0V).

Step 5: The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor.

Step 6: The processor calibrates the methane gas concentration corresponding to the digital quantity obtained by the optical signal returned by the sensing probe according to the digital quantity obtained by the optical signal reflected from the methane gas sealed gas chamber as a reference. The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. an optical fiber methane gas concentration measuring device of anti-strong interference, is characterized in that: comprise: the detection module, the transmitter and the alarm controller of successive signal connection; Wherein, the detection module includes at least one sensing probe and a gas-sealed air chamber, and both the sensing probe and the gas-sealed air chamber are connected to the optical circulator of the transmitter through an optical fiber; In the transmitter: The processor, the driving module, the light source and the optical circulator are signally connected in sequence; The optical circulator, the optical switch, the optical balance detector, the analog binarization, the multiplier component, the analog-to-digital converter, and the processor are sequentially connected in signals, wherein the multiplier component includes a multiplier 1 and a multiplier 2, which are connected in parallel; The optical switch, the photoelectric converter 1 and the multiplier 1 are signally connected in sequence; The optical circulator is respectively connected with the optical balance detector and the photoelectric converter 2 signal; The optical switch and the data sending module are signal-connected with the processor, and the data sending module is signal-connected with the data receiving module of the alarm controller. 2 . The optical fiber methane gas concentration measuring device against strong interference according to claim 1 , wherein the transmitter further comprises a temperature control module, and the temperature control module is connected with the light source. 3 . 3 . The optical fiber methane gas concentration measuring device against strong interference according to claim 1 , wherein the optical fiber is a passive long-distance transmission optical fiber. 4 . 4. The optical fiber methane gas concentration measuring device of anti-strong interference according to claim 1, is characterized in that: described alarm controller is provided with data receiving module, display module, relay group and power supply module, display module, relay group And the power module are connected with the data receiving module. 5 . The optical fiber methane gas concentration measuring device according to claim 4 , wherein the power module is connected to the transmitter. 6 . 6 . The optical fiber methane gas concentration measuring device against strong interference according to claim 4 , wherein the alarm controller further comprises a button module. 7 . 7 . The optical fiber methane gas concentration measuring device against strong interference according to claim 4 , wherein the alarm controller further comprises an acousto-optic alarm device, an indicator light and a fan, all of which are connected to a relay group. 8 . 8 . The optical fiber methane gas concentration measuring device against strong interference according to claim 7 , wherein the indicator light comprises a running indicator light, a fault indicator light and a power indicator light. 9 . 9. An optical fiber methane gas concentration measurement method for strong interference resistance, characterized in that: comprising the steps: The light source generates a continuous optical signal under the excitation of the ramp signal of the driving module, and the continuous optical signal covers the absorption peak of methane gas; The optical circulator receives the continuous optical signal of the light source, divides it into N+1 channels, and transmits it to each sensing probe and the gas-sealed gas chamber through the optical fiber; transmits the optical signal reflected by the sensing probe to the optical switch, and sequentially passes through the optical switch. Transmit each optical signal to the photoelectric balance detector; transmit the optical signal reflected back from the gas-sealed gas chamber to the photoelectric balance detector; The photoelectric balance detector converts two optical signals into one electrical signal and outputs it to analog binarization; The analog binarization outputs the analog electrical signal of constant voltage between the two peaks before and after the electrical signal, and outputs the analog electrical signal of 0V outside the two peak points; the multiplier 1 and the multiplier 2 receive the analog electrical signal; The photoelectric converter 1 receives the optical signal returned by one sensor probe transmitted by the optical switch, and outputs it to the multiplier 1; The photoelectric converter 2 receives the optical signal returned by the methane gas sealed gas chamber, and outputs it to the multiplier 2; The multiplier 1 and the multiplier 2 transmit the electrical signal whose optical wavelength range is on the adjacent two sides of the methane absorption peak to the analog-to-digital converter; The analog-to-digital converter converts the voltage signal into a digital signal and transmits it to the processor; The processor uses the digital quantity obtained by the optical signal reflected from the gas-sealed gas chamber as a reference, and calibrates the digital quantity obtained by the optical signal returned by the sensor probe, and calculates the methane gas concentration value; The data sending module transmits the methane gas concentration value calculated by the processor to the alarm controller. 10 . The optical fiber methane gas concentration measurement method according to claim 1 , wherein the wavelength of the absorption peak of methane gas is 1654 nm. 11 .

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