阅读说明：本技术 基于fbg解调仪的f-p干涉型多点测量氢气传感器 (F-P interference type multipoint measurement hydrogen sensor based on FBG demodulator ) 是由 赵春柳 李嘉丽 毛邦宁 王海龙 于 2019-11-08 设计创作，主要内容包括：本发明涉及基于FBG解调仪的F-P干涉型多点测量氢气传感器,包括FBG解调仪、长距离单模传输光纤、阵列波导光栅、FP传感头、PC机；所述FP传感头由空芯光纤、PDMS(聚二甲基硅氧烷)薄膜和Pt/WO<Sub>3</Sub>(三氧化钨载铂)氢敏材料组成；当氢气浓度增加时,Pt/WO<Sub>3</Sub>氢敏材料与氢气发生反应放热,PDMS薄膜体积膨胀,空气腔腔长缩短,FP传感头的干涉光谱将发生漂移,进而阵列波导光栅的反射光强发生改变,通过PC机检测反射光强的变化,就可实现对氢气浓度的测量。本发明提出一种结构简单、灵敏度高、可同时多点测量的基于FBG解调仪的F-P干涉型多点测量氢气传感器。(The invention relates to an F-P interference type multipoint measurement hydrogen sensor based on an FBG (fiber Bragg Grating) demodulator, which comprises the FBG demodulator, a long-distance single-mode transmission optical fiber, an array waveguide grating, an FP (Fabry-Perot) sensing head and a PC (personal computer); the FP sensing head consists of a hollow fiber, a PDMS (polydimethylsiloxane) film and Pt/WO 3 (platinum-supported tungsten trioxide) hydrogen sensitive material; Pt/WO when the hydrogen concentration increases 3 The hydrogen sensitive material reacts with hydrogen to release heat, the volume of the PDMS film expands, the length of the air cavity is shortened, the interference spectrum of the FP sensing head drifts, the reflected light intensity of the arrayed waveguide grating changes, and the change of the reflected light intensity is detected by the PC, so that the measurement of the hydrogen concentration can be realized. The invention provides an F-P interference type multipoint measurement hydrogen sensor based on an FBG (fiber Bragg Grating) demodulator, which has a simple structure and high sensitivity and can perform multipoint measurement simultaneously.)

1. F-P interference type multipoint measurement hydrogen sensor based on FBG demodulator is characterized by comprising the following steps:

selecting an FBG demodulator, an arrayed waveguide grating with N channels and working wavelength matched with the output wavelength of the FBG demodulator, a long-distance single-mode transmission optical fiber, N FP sensing heads and a PC (personal computer); the FP sensing head consists of a hollow fiber, a PDMS (polydimethylsiloxane) film and Pt/WO₃(platinum-supported tungsten trioxide) hydrogen sensitive material; the FBG demodulator consists of a light source, a circulator and a signal demodulation module;

step two, the manufacturing process of the FP sensor head is as follows: one end of a section of hollow optical fiber is welded with the single-mode optical fiber by using an optical fiber fusion splicer, the length of the hollow optical fiber is 100-150 mu m, the tip of the hollow optical fiber is inserted into PDMS liquid for 10 seconds, the PDMS liquid enters the hollow optical fiber due to capillary effect, air is sealed in the hollow optical fiber, and the length of an air cavity is 30-80 mu m; then wiping off PDMS liquid attached to the outside of the optical fiber by alcohol, placing the whole sensing head on a heating table for heating and curing, and continuously heating for 3-4 hours at 60-70 ℃ to change the PDMS material from a liquid state to a semi-crosslinked state; taking off the sensing head from the heating table, and extending one end of the hollow optical fiber into the Pt/WO₃Among the hydrogen-sensitive materials, Pt/WO₃The hydrogen sensitive material can be adhered to a semi-crosslinked PDMS film with viscosity, and Pt/WO is adhered to the hydrogen sensitive material₃Placing the sensing head of hydrogen-sensitive material on a heating table, continuously heating at 60-70 deg.C for 3-4 hr to completely cure PDMS film, and Pt/WO₃The hydrogen sensitive material is tightly fixed on the PDMS film, and the whole FP sensing head is manufactured;

for the FP sensing head that the preparation was accomplished, through the signal light of single mode fiber transmission, some will be in the butt fusion face reflection of single mode fiber and hollow optic fibre, and another part light will get into the air chamber through the butt fusion face, and the light that gets into the air chamber will be reflected at the interface department of PDMS film and air, and then coherent interference takes place for two bundles of reverberation, and the reflected light intensity I can be expressed as:

I₁and I₂The reflection intensity of the fusion-joint surface of the single-mode optical fiber and the hollow optical fiber and the interface of the PDMS film and the air respectively, L is the length of the air cavity of the FP sensor head, n_airIs the refractive index of air, λ is the wavelength of light;

when the light intensity reaches the maximum value, the phase difference

λ_dis the wavelength corresponding to the maximum intensity of light, m is an arbitrary integer;

the Free Spectral Range (FSR), which is the distance between two adjacent reflection peaks or valleys, is related to the bandwidth of a single spectral period and can be expressed as:

with the change of the hydrogen concentration, Pt/WO₃The hydrogen sensitive material and hydrogen gas generate oxidation-reduction reaction to release heat, the PDMS film expands rapidly, the length L of the air cavity is shortened, and the phase difference is

the hydrogen sensitivity S of the FP sensor head can be expressed as:

Δ λ represents the wavelength drift amount, c is the hydrogen concentration, and Δ c represents hydrogenThe amount of change in concentration, k is the coefficient of thermal expansion of PDMS, and α is Pt/WO₃The heat released by the hydrogen sensitive material per unit concentration; since k and alpha are constants, it can be seen that the shift amount of the wavelength and the hydrogen concentration are in a linear relationship;

thirdly, the optical output end of the FBG demodulator is connected with the optical input end of the arrayed waveguide grating through a single-mode transmission optical fiber, N channels of the arrayed waveguide grating are respectively connected with the single-mode optical fiber ends of the N FP sensing heads, and the signal output end of the FBG demodulator is connected with the PC; the FBG demodulator generates signal light which is transmitted to the arrayed waveguide grating by a single mode fiber, the arrayed waveguide grating divides the signal light into N channels with different central wavelengths, each channel is respectively connected with the FP sensing head, each beam of signal light is respectively emitted at the FP sensing head, two beams of reflected light are subjected to coherent interference, the reflected light is combined into one beam of light after passing through the arrayed waveguide grating and is output to the FBG demodulator, and the optical signal is converted into an electric signal after being demodulated by a signal demodulation module of the FBG demodulator and is output to a PC (personal computer) for display and processing;

the arrayed waveguide grating is a multiplexing component with N channels, each channel has a fixed wavelength range, each channel is respectively connected with an FP sensing head which can be matched with the central wavelength of the channel, and the central wavelength of the mth channel of the arrayed waveguide grating is fixed; when the center wavelength of the FP sensing head is completely overlapped with the center wavelength of the mth channel, the overlapped part of the reflection spectrums of the FP sensing head and the arrayed waveguide grating is the maximum value, namely the reflection light intensity is the maximum value; when the hydrogen concentration changes, the reflection spectrum of the FP sensing head drifts, and if the reflection spectrum drifts to the right, the overlapped part of the mth channel of the arrayed waveguide grating and the reflection spectrum of the FP sensing head is reduced, and at the moment, the reflection light intensity is reduced; when the reflection spectrum of the FP sensing head is not coincident with the reflection spectrum of the mth channel completely, the reflection light intensity is the minimum value; therefore, the reflected light intensity of the array waveguide grating changes monotonously with the change of the hydrogen concentration;

the FBG demodulator obtains a reflected light intensity signal of the mth channel of the arrayed waveguide grating through demodulation processing, in one scanning period of the FBG demodulator, the output abscissa of the FBG demodulator corresponds to a wavelength range, and the ordinate represents a light intensity value;

reflection spectrum I of mth channel of arrayed waveguide grating_mCan be expressed as:

λ_mthe central wavelength of the mth channel of the arrayed waveguide grating is used, b is the standard deviation, and the width of the channel is controlled;

the reflection spectrum I of the FP sensor head along with the change of the hydrogen concentration is shown as the formula (1), namely:

the FBG demodulator monitors the reflected light intensity S of the mth channel of the arrayed waveguide grating_mCan be expressed as:

λ₁and λ₂The wavelength range of the mth channel of the arrayed waveguide grating; the formula (8) shows that the light intensity obtained by the FBG demodulation instrument is related to the air cavity length L of the FP sensing head, the air cavity length L of the FP sensing head is related to the hydrogen concentration c, and the FBG demodulation instrument can obtain the change of the hydrogen concentration at the position corresponding to the FP sensing head by monitoring the change of the reflected light intensity of the mth channel of the arrayed waveguide grating;

the scanning range of the FBG demodulation instrument covers the working wavelength of the arrayed waveguide grating, namely the FBG demodulation instrument can monitor the reflected light intensity of the N channels of the arrayed waveguide grating in sequence, therefore, the change of the reflected light intensity of all the channels of the arrayed waveguide grating is monitored by using the FBG demodulation instrument, the hydrogen concentration at the N FP sensing heads can be measured in real time, and the multiplexing of the FP sensing heads and the simultaneous measurement of the multi-point hydrogen concentration are realized.

2. The device for realizing the method of claim 1 comprises an FBG demodulator, a long-distance single-mode transmission optical fiber, an arrayed waveguide grating, an FP sensing head and a PC (personal computer)(ii) a The optical output end of the FBG demodulator is connected with the optical input end of the arrayed waveguide grating through a single-mode transmission optical fiber, the optical output channels of the arrayed waveguide grating are respectively connected with the single-mode optical fiber end of the FP sensing head, and the signal output end of the FBG demodulator is connected with the PC; Pt/WO when the hydrogen concentration increases₃The hydrogen sensitive material reacts with hydrogen to release heat, the volume of the PDMS film expands, and the length of the air cavity is shortened, so that the interference spectrum of the FP sensing head drifts, the reflected light intensity of the arrayed waveguide grating changes, and the change of the reflected light intensity is detected by the PC, so that the measurement of the hydrogen concentration can be realized.

Technical Field

The invention belongs to the technical field of optical fiber sensing, and particularly relates to an F-P interference type multipoint hydrogen measurement sensor based on an FBG (fiber Bragg Grating) demodulator.

Background

As a clean, sustainable and pollution-free new energy, hydrogen draws wide attention in various fields in the aspect of solving energy crisis. The combustion product of the hydrogen only contains water and does not contain any harmful substance, thereby being a clean energy and having wide application in the production and living fields. However, due to the high diffusion coefficient, low ignition energy, high heat of combustion and wide explosive concentration range (4% -75%) of hydrogen, it is very easy to leak from the container and even explode in air, so that the detection and monitoring of the hydrogen concentration is very important for safe use of hydrogen. The traditional electric sensor is easy to generate electric spark to cause hydrogen explosion, and the optical fiber hydrogen sensor is an intrinsic safety device taking optical signals as sensing media, so in recent years, the optical fiber hydrogen sensor is widely concerned by people.

The principle of the optical fiber hydrogen sensor is that the optical fiber is combined with the hydrogen sensitive material, when the hydrogen sensitive material reacts with hydrogen, the physical property of the optical fiber is changed, so that the optical characteristic of transmitted light in the optical fiber is changed, and the hydrogen concentration can be measured by detecting the change of output light and analyzing the relation between the change and the corresponding physical quantity. The current common fiber hydrogen sensors include an interference type, a fiber grating type and the like.

The interference type optical fiber hydrogen sensor such as an M-Z (Mach-Zehnder) interferometer type, an F-P (Fabry-Perot) interferometer type and the like has the advantages of high sensitivity, simple structure, low cost, easiness in operation and the like, wherein the F-P interference type sensor forms a microcavity in two reflecting surfaces by manufacturing the two reflecting surfaces in an optical fiber, and when a light beam enters along the optical fiber, the light beam returns along the original path after being reflected by the two end surfaces and forms interference light. When the hydrogen concentration changes and acts on the microcavity, the cavity length of the microcavity changes, so that the output interference light signal also changes. However, the interference type optical fiber hydrogen sensor usually has only one sensing head, and can only measure the hydrogen concentration at a single point, if the interference type sensors with the same structure are cascaded, the interference spectrum is more complex, signal light is difficult to distinguish, and the requirement of the actual application occasion of multipoint simultaneous measurement cannot be met.

The Fiber Bragg Grating (FBG) type fiber hydrogen sensor performs signal sensing in a mode of changing wavelength, is a sensor with mature technology at present, is widely applied to distributed measurement, but has lower sensitivity compared with an interference type fiber hydrogen sensor generally, and the signal demodulation technology of the FBG sensor is a key part in various fiber bragg grating sensing systems and aims to demodulate sensing signals from wavelength information and convert the sensing signals into electric signals for display and calculation. The FBG demodulator is a commercial fiber grating demodulator with mature technology, has the advantages of small volume, high precision, accurate measurement and spectral analysis capability in large dynamic range and the like, can be used as a light source, and has the capability of spectral analysis, so that if the FBG demodulator is used in a traditional optical fiber sensing system, the FBG demodulator can replace a commonly used broadband light source and a spectrometer, thereby greatly simplifying the volume of optical sensing and being more convenient for practical operation and use.

Aiming at the problems that the optical fiber hydrogen sensor is low in sensitivity, complex in structure and incapable of simultaneously measuring multiple points, the invention provides an F-P interference type multiple-point measurement hydrogen sensor based on an FBG demodulator. The invention has the advantages of simple structure, high sensitivity, simultaneous multi-point measurement, suitability for remote measurement and the like.

Disclosure of Invention

Aiming at the defects that the conventional optical fiber hydrogen sensor has low sensitivity and a complex structure and cannot simultaneously perform multi-point measurement on an F-P interference type sensor, the invention provides the F-P interference type multi-point measurement hydrogen sensor based on the FBG demodulator, which has the advantages of high sensitivity, simplicity in operation, flexibility and convenience, capability of simultaneously performing multi-point measurement and suitability for remote measurement.

The method adopted for solving the technical problem comprises the following steps:

selecting an FBG demodulator, an arrayed waveguide grating with N channels and working wavelength matched with the output wavelength of the FBG demodulator, a long-distance single-mode transmission optical fiber, N FP sensing heads and a PC (personal computer); the FP sensing head consists of a hollow fiber, a PDMS (polydimethylsiloxane) film and Pt/WO₃(platinum-supported tungsten trioxide) hydrogen sensitive material; the FBG demodulator consists of a light source, a circulator and a signal demodulation module;

step two, the manufacturing process of the FP sensor head is as follows: using a fusion splicer to splice a hollow sectionOne end of the optical fiber is welded with the single-mode optical fiber, the length of the hollow optical fiber is 100-150 mu m, the tip of the hollow optical fiber is inserted into PDMS liquid for 10 seconds, the PDMS liquid enters the hollow optical fiber due to capillary effect, air is sealed inside the hollow optical fiber, and the length of an air cavity is 30-80 mu m; then wiping off PDMS liquid attached to the outside of the optical fiber by alcohol, placing the whole sensing head on a heating table for heating and curing, and continuously heating for 3-4 hours at 60-70 ℃ to change the PDMS material from a liquid state to a semi-crosslinked state; taking off the sensing head from the heating table, and extending one end of the hollow optical fiber into the Pt/WO₃Among the hydrogen-sensitive materials, Pt/WO₃The hydrogen sensitive material can be adhered to a semi-crosslinked PDMS film with viscosity, and Pt/WO is adhered to the hydrogen sensitive material₃Placing the sensing head of hydrogen-sensitive material on a heating table, continuously heating at 60-70 deg.C for 3-4 hr to completely cure PDMS film, and Pt/WO₃The hydrogen sensitive material is tightly fixed on the PDMS film, and the whole FP sensing head is manufactured;

for the FP sensing head that the preparation was accomplished, through the signal light of single mode fiber transmission, some will be in the butt fusion face reflection of single mode fiber and hollow optic fibre, and another part light will get into the air chamber through the butt fusion face, and the light that gets into the air chamber will be reflected at the interface department of PDMS film and air, and then coherent interference takes place for two bundles of reverberation, and the reflected light intensity I can be expressed as:

I₁and I₂The reflection intensity of the fusion-joint surface of the single-mode optical fiber and the hollow optical fiber and the interface of the PDMS film and the air respectively, L is the length of the air cavity of the FP sensor head, n_airIs the refractive index of air, λ is the wavelength of light;

when the light intensity reaches the maximum value, the phase difference

Can be expressed as:

λ_dis the wavelength corresponding to the maximum intensity of light, m is an arbitrary integer;

the Free Spectral Range (FSR), which is the distance between two adjacent reflection peaks or valleys, is related to the bandwidth of a single spectral period and can be expressed as:

with the change of the hydrogen concentration, Pt/WO₃The hydrogen sensitive material and hydrogen gas generate oxidation-reduction reaction to release heat, the PDMS film expands rapidly, the length L of the air cavity is shortened, and the phase difference is

The reflection spectrum of the FP sensing head is reduced, so the reflection spectrum of the FP sensing head is shifted;

the hydrogen sensitivity S of the FP sensor head can be expressed as:

Δ λ represents the wavelength drift amount, c represents the hydrogen concentration, Δ c represents the hydrogen concentration change amount, k is the thermal expansion coefficient of PDMS, and α is Pt/WO₃The heat released by the hydrogen sensitive material per unit concentration; since k and alpha are constants, it can be seen that the shift amount of the wavelength and the hydrogen concentration are in a linear relationship;

thirdly, the optical output end of the FBG demodulator is connected with the optical input end of the arrayed waveguide grating through a single-mode transmission optical fiber, N channels of the arrayed waveguide grating are respectively connected with the single-mode optical fiber ends of the N FP sensing heads, and the signal output end of the FBG demodulator is connected with the PC; the FBG demodulator generates signal light which is transmitted to the arrayed waveguide grating by a single mode fiber, the arrayed waveguide grating divides the signal light into N channels with different central wavelengths, each channel is respectively connected with the FP sensing head, each beam of signal light is respectively emitted at the FP sensing head, two beams of reflected light are subjected to coherent interference, the reflected light is combined into one beam of light after passing through the arrayed waveguide grating and is output to the FBG demodulator, and the optical signal is converted into an electric signal after being demodulated by a signal demodulation module of the FBG demodulator and is output to a PC (personal computer) for display and processing;

the arrayed waveguide grating is a multiplexing component with N channels, each channel has a fixed wavelength range, each channel is respectively connected with an FP sensing head which can be matched with the central wavelength of the channel, and the central wavelength of the mth channel of the arrayed waveguide grating is fixed; when the center wavelength of the FP sensing head is completely overlapped with the center wavelength of the mth channel, the overlapped part of the reflection spectrums of the FP sensing head and the arrayed waveguide grating is the maximum value, namely the reflection light intensity is the maximum value; when the hydrogen concentration changes, the reflection spectrum of the FP sensing head drifts, and if the reflection spectrum drifts to the right, the overlapped part of the mth channel of the arrayed waveguide grating and the reflection spectrum of the FP sensing head is reduced, and at the moment, the reflection light intensity is reduced; when the reflection spectrum of the FP sensing head is not coincident with the spectrogram of the mth channel completely, the reflection light intensity is the minimum value; therefore, the reflected light intensity of the array waveguide grating changes monotonously with the change of the hydrogen concentration;

the FBG demodulator obtains a reflected light intensity signal of the mth channel of the arrayed waveguide grating through demodulation processing, in one scanning period of the FBG demodulator, the output abscissa of the FBG demodulator corresponds to a wavelength range, and the ordinate represents a light intensity value;

reflection spectrum I of mth channel of arrayed waveguide grating_mCan be expressed as:

λ_mthe central wavelength of the mth channel of the arrayed waveguide grating is used, b is the standard deviation, and the width of the channel is controlled;

the reflection spectrum I of the FP sensor head along with the change of the hydrogen concentration is shown as the formula (1), namely:

the FBG demodulator monitors the reflected light intensity S of the mth channel of the arrayed waveguide grating_mCan be expressed as:

λ₁and λ₂The wavelength range of the mth channel of the arrayed waveguide grating; the formula (8) shows that the light intensity obtained by the FBG demodulation instrument is related to the air cavity length L of the FP sensing head, the air cavity length L of the FP sensing head is related to the hydrogen concentration c, and the FBG demodulation instrument can obtain the change of the hydrogen concentration at the position corresponding to the FP sensing head by monitoring the change of the reflected light intensity of the mth channel of the arrayed waveguide grating;

the scanning range of the FBG demodulation instrument covers the working wavelength of the arrayed waveguide grating, namely the FBG demodulation instrument can monitor the reflected light intensity of the N channels of the arrayed waveguide grating in sequence, therefore, the change of the reflected light intensity of all the channels of the arrayed waveguide grating is monitored by using the FBG demodulation instrument, the hydrogen concentration at the N FP sensing heads can be measured in real time, and the multiplexing of the FP sensing heads and the simultaneous measurement of the multi-point hydrogen concentration are realized.

The invention adopts the following devices for solving the technical problems:

the FBG demodulation device is characterized by comprising an FBG demodulation instrument, a long-distance single-mode transmission optical fiber, an array waveguide grating, N FP sensing heads and a PC (personal computer); the optical output end of the FBG demodulator is connected with the optical input end of the arrayed waveguide grating through a single-mode transmission optical fiber, the N optical output channels of the arrayed waveguide grating are respectively connected with the single-mode optical fiber ends of the N FP sensing heads, and the optical output end of the FBG demodulator is connected with the PC.

The invention has the beneficial effects that:

1. the invention adopts PDMS film and Pt/WO₃FP filled with hydrogen sensitive material is sensor head, PDMS material has high thermal expansion coefficient, Pt/WO₃The hydrogen sensitive material reacts with the hydrogen to emit heat, the PDMS film rapidly expands due to heating, the length of the air cavity of the FP sensor head is rapidly shortened, and the FP sensor head isHigh hydrogen sensitivity and small volume, and is due to Pt/WO₃The hydrogen sensitive material is fixed inside the hollow optical fiber and is not easy to fall off and damage.

2. The invention adopts the array waveguide grating as a multiplexing device, has N channels with different central wavelengths, can be directly connected with N FP sensing heads respectively, has no mutual interference of the channels, can independently measure each channel, can directly monitor the change of the reflected light intensity, and realizes the simultaneous measurement of the concentration of the hydrogen at multiple points.

3. The FBG demodulator is used as a generation and demodulation device of the optical signal, and can simultaneously replace bulky optical instruments in common optical fiber hydrogen sensors, such as a broadband light source, a spectrometer and the like to work, so that the volume of the whole optical fiber sensor is greatly simplified, and the actual measurement is more convenient and flexible.

Drawings

FIG. 1 is a structural schematic diagram of an F-P interference type multi-point measurement hydrogen sensor based on an FBG demodulator.

FIG. 2 is a schematic diagram of an F-P interference type multi-point measurement hydrogen sensor test based on an FBG demodulator.

FIG. 3 is a schematic diagram of a test result of an F-P interference type multi-point measurement hydrogen sensor based on an FBG demodulator.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, the F-P interferometric multi-point hydrogen sensor based on the FBG demodulator comprises an FBG demodulator 1, a single-mode transmission fiber 2, an arrayed waveguide grating 3, an FP sensor head 4, and a PC 5. The FP sensing head 4 is formed by welding a small segment of single-mode optical fiber 6 with a hollow optical fiber 7, a PDMS film 8 is filled in the hollow optical fiber 7 to form a closed air cavity 9, and Pt/WO is adhered to the outer side of the PDMS film 8₃Hydrogen sensitive material 10 formation; the FBG demodulator 1 consists of a light source 11, a circulator 12 and a signal demodulation module 13. The optical output end 101 of the FBG demodulator 1 is connected with the optical input end of the arrayed waveguide grating 3 through the single-mode transmission optical fiber 2, the N optical output channels of the arrayed waveguide grating 3 are respectively connected with the single-mode optical fiber 6 ends of the N FP sensing heads 4, and the signal output end 102 of the FBG demodulator 1 is connected with the PC 5And (4) connecting.

As shown in fig. 2-1, the center wavelength of the FP sensor head completely coincides with the center wavelength of the mth channel of the arrayed waveguide grating, and at this time, the coinciding part of the reflection spectra of the FP sensor head and the arrayed waveguide grating is the maximum value, that is, the reflected light intensity is the maximum value; when the hydrogen concentration changes, the reflection spectrum of the FP sensing head drifts, as shown in figure 2-1, the superposition part of the reflection spectrum of the FP sensing head and the array waveguide grating is reduced, the reflection light intensity is gradually reduced, and the change of the hydrogen concentration and the change of the reflection light intensity are in a linear relation in a certain interval.

As shown in fig. 3, the reflected light intensity of the N channels of the arrayed waveguide grating changes with the change in the hydrogen concentration.

The working mode of the invention is as follows: the signal light that light source 11 sent in FBG demodulation appearance 1, in the array waveguide grating 3 is inputed from single mode transmission fiber 2, array waveguide grating 3 can be with a bundle of signal light demultiplexing for N bundle of light that has different central wavelength, and export N FP sensing head 4 respectively from its N passageway, every bundle of light is reflected at PDMS film 8, the reflected light is through N passageway to array waveguide grating 3 and multiplexing become a bundle of synthetic light, the reflected light is through single mode transmission fiber 2 transmission to FBG demodulation appearance 1, after signal demodulation module 13 demodulation, convert the optical signal into the signal of telecommunication and export PC 5. Pt/WO when the hydrogen concentration in the environment increases₃The hydrogen sensitive material 10 can take place the chemical reaction with hydrogen and give off heat, and PDMS film 8 is heated the volume expansion, leads to the chamber length of air chamber 9 to shorten, therefore the interference spectrum of FP sensing head 4 will drift, and then the reflection light intensity of array waveguide grating 3 can change, detects the change of reflection light intensity through PC 5, establishes the corresponding relation of reflection light intensity and hydrogen concentration, just can realize the measurement to multiple spot hydrogen concentration.

The device can realize that F-P based on FBG demodulation appearance interferes type multiple spot and measures hydrogen concentration measurement key technology of hydrogen sensor has:

1. the structure of the FP sensor head. PDMS films and Pt/WO₃The FP sensing head filled with hydrogen sensitive material is the basis for realizing high-sensitivity sensing, and adopts PDMS material with high thermal expansion coefficient and Pt/WO material with good selectivity to hydrogen₃Hydrogen sensitive materialThe material can make the hydrogen concentration measurement more accurate and sensitive, and the Pt/WO₃The hydrogen sensitive material is adhered to the inner side of the PDMS film and embedded into the hollow optical fiber, so that the hydrogen sensitive material can play a certain protection role, is not easy to drop and wear and is easy to measure for a long time.

2. And (5) the FBG demodulator. The light source and the signal demodulation module which are arranged in the FBG demodulator can replace a light source and a spectrometer in a traditional optical fiber hydrogen sensor, and the key for reducing the volume of the whole device is realized.

3. An arrayed waveguide grating. The array waveguide grating is used as an optical path multiplexing and demultiplexing unit of the sensor, is a key device for realizing simultaneous multipoint measurement of hydrogen concentration, has N channels in the working wavelength range, is fixed at intervals, and does not interfere with each other when in work.

4. And connecting the FP sensing head with the array waveguide grating. The center wavelength of the FP sensing head is matched with the center wavelength of the corresponding channel of the arrayed waveguide grating, so that the linear relation between the change of the hydrogen concentration at the FP sensing head and the reflected light intensity of the corresponding channel of the arrayed waveguide grating is ensured.

In one embodiment of the invention, the output wavelength of a laser light source of an FBG demodulator (Sm125) is 1530nm-1565nm, the single-mode transmission fiber and the single-mode fiber for manufacturing the FP sensing head both adopt a conventional single-mode fiber (G.625), the hollow-core fiber adopts a quartz capillary tube (TSP075150), the length of the hollow-core fiber is 100 mu m-150 mu m, the length of an air cavity is 30 mu m-80 mu m, the thickness of a PDMS film is 20 mu m-70 mu m, the array waveguide grating is provided with 16 channels which are respectively connected with 16 FP sensing heads, and experimental results show that the hydrogen sensitivity of the F-P interference type multi-point measurement hydrogen sensor based on the FBG demodulator can reach 1.210/dB DEG C within the temperature range of 30 ℃ to 40 ℃.

While the foregoing shows and describes the fundamental principles and features of this invention, there are alterations and modifications which fall within the scope of the invention as claimed, without departing from the principles of this invention.