CN109668860A - Long-period fiber grating hydrogen detector based on Mach-Zender interferometer - Google Patents
Long-period fiber grating hydrogen detector based on Mach-Zender interferometer Download PDFInfo
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- CN109668860A CN109668860A CN201811507089.5A CN201811507089A CN109668860A CN 109668860 A CN109668860 A CN 109668860A CN 201811507089 A CN201811507089 A CN 201811507089A CN 109668860 A CN109668860 A CN 109668860A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
- G01N2021/458—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods using interferential sensor, e.g. sensor fibre, possibly on optical waveguide
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Abstract
The invention discloses a kind of long-period fiber grating hydrogen detector based on Mach-Zender interferometer, by wideband light source, fiber coupler, gas chamber, air inlet, gas outlet, Mach-Zehnder LPG optical fiber structure, palladium-gold-palladium-gold-palladium alloy layer, test chamber, photodiode, power amplifier module, loudspeaker composition.When detector is in the environment containing hydrogen, hydrogen is reacted with palladium-gold-palladium-gold-palladium alloy layer of optical fiber surface.When density of hydrogen changes, the transmitted spectrum of fiber grating pair generates variation, i.e., the interference light signal Strength Changes that photoelectric diode receives obtain density of hydrogen and curent change relationship to generate the variation of electric current.Electric signal is carried out power amplification, is alerted more than after given threshold by loudspeaker.Due to the outstanding Wuli-Shili-Renli system approach of optical fiber, which has corrosion-resistant, the advantage that anti-electromagnetic interference capability is strong, reusability is good, easy to use, has good practical value and application prospect.
Description
Technical field
The invention belongs to the technical fields of hydrogen concentration measurement, and in particular to a kind of length based on Mach-Zender interferometer
Period optical fiber grating hydrogen detector.
Background technique
Various functional fiber grating sensors based on Mach-Zender interferometer structure start to send out rapidly since 1991
Exhibition, has greatly pushed the development of sensing technology, has widened the application range of fiber grating.
Since optical fiber has the advantages that light, cheap, electromagnetism interference, corrosion-resistant, have very in sensing detection
Good practical value.
Mach-Zehnder optical fiber structure is made of two sections of identical long-period fiber grating (LGP), avoids drawing cone, erosion
Process, the preparation process such as quarter are simple.
Since palladium has unique selective and higher response speed for hydrogen, palladium-gold-palladium-gold-palladium alloy layer can be effective
The phenomenon that phase transformation, null offset are generated when pure palladium is reacted with hydrogen is eliminated, therefore palladium-gold-palladium-gold-palldium alloy is ideal hydrogen
Gas detects sensing material, so in this experiment using gold, palladium as sensing material.
Photodiode is the optoelectronic sensor for optical signal being converted into electric signal, its working principle is based on photoelectricity
Effect can change the size of output electric current using this characteristic, to realize the measurement changed to light intensity, and have volume
It is small, the service life is long, quantum efficiency is high, be not necessarily to high voltage the advantages that, be widely used.
Summary of the invention
For the deficiency of existing fiber optical grating construction hydrogen gas sensor, it is an object of the invention to Mach-Zehnder LPG
Optical fiber structure is sensor primary structure, and with the variation of the interference peaks threshold value of transmitted spectrum, the displacement of wavelength is where interference peaks
The processing is simple for basis and long-period fiber grating (LPG), the high advantage of coupling sensitivity, realizes the measurement of density of hydrogen, and
Density of hydrogen realizes alarm in time when reaching threshold value, solve the hydrogen sensor susceptibility based on bragg grating (FBG)
Disadvantage low, that preparation process is cumbersome, complicated.
The invention is realized by the following technical scheme: the long-period fiber grating hydrogen inspection based on Mach-Zender interferometer
Instrument is surveyed, by wideband light source (1), fiber coupler (2), gas chamber (3), air inlet (4), gas outlet (5), Mach-Zehnder LPG light
Fine structure (6), palladium-gold-palladium-gold-palladium alloy layer (7), test chamber (8), photodiode (9), power amplifier module (10) are raised
Sound device (11) composition；It is characterized by: wideband light source (1) is connected to Mach-Zehnder by optical fiber and fiber coupler (2)
LPG optical fiber structure (6), Mach-Zehnder LPG optical fiber structure (6) are fixed in closed lighttight gas chamber (3), Mach-Zehnder
Your LPG (6) two sections of LGP centre distances of optical fiber structure are 50 millimeters, and grating length is 20 millimeters, and screen periods are 500 microns, horse
The fiber bragg grating center wavelength of conspicuous-Zeng Deer LPG optical fiber structure (6) is 1550 nanometers, palladium-gold-palladium-gold-palladium alloy layer (7)
With a thickness of 100 nanometers, for palladium layers with a thickness of 10-20 nanometers, layer gold thickness range is 20- in palladium-gold-palladium-gold-palladium alloy layer (7)
30 nanometers, palladium-gold-palladium-gold-palladium alloy layer (7) is 70 millimeters along optical fiber axial direction length；Pass through fiber coupler (2) and optical fiber
It is connected to the test chamber (8) based on photodiode (9), when the density of hydrogen in gas chamber (3) changes, photodiode
(9) the interference light signal intensity received changes, so that the electric current generated changes, obtains density of hydrogen and electric current becomes
The relationship of change, the electric signal input power amplification module (8) that photodiode (9) are generated, amplified electric signal is in the mould
It is compared by integrated transporting discharging chip with setting value in block, realizes alarm by loudspeaker (9) after the threshold exceeded.
The loudspeaker (9) is driven using 5V voltage.
The material of the test chamber (6) is polyethylene, is dual openings cube, a length of 25mm, width 15mm are a height of
15mm, with a thickness of 3mm.
The fiber bragg grating center wavelength of the Mach-Zehnder LPG optical fiber structure (4) is 1550nm.
, can be with cracking resolution of velocity for two hydrogen atoms when hydrogen encounters the palladium in alloy-layer, and occur instead with palladium
It answers, generates palladium hydride, volume expands therewith.Palladium hydride has the optical property different from palladium, its complex dielectric permittivity
Real part and imaginary part are all smaller, this makes the boundary condition and core mode of gold-palladium alloy layer inner surface and the covering outer surface of LPG
Effective refractive index between cladding mode changes.Meanwhile the presence of the gold in alloy-layer effectively inhibit the phase transformation of palladium with
The null offset of sensor prevents the palladium film of optical fiber surface from occurring fracturing and flaking off phenomenon, and it is fine that this has gold-palldium alloy
Hydrogen detectability.
The working principle of the invention is: the interference pattern based on the interference of Mach-Zehnder LPG structure works as monochromatic collimated beam
It is incident in optical fiber, in the case where the resonance wavelength of light meets phase-matching condition, LPG can induce the coupling of core mode Yu cladding mode optical path
It closes, relationship meets following formula:
λ res is resonance wavelength in formula, and Λ is screen periods,For the effective refractive index of core mode,For m rank cladding mode
Effective refractive index.
The effective refractive index of m rank cladding mode in (1) formulaFor the major parameter for influencing resonance wavelength, and its fadout
Field is easy to be influenced by the refractive index of external environment.Therefore when fibre cladding surface is there are when gold-palladium alloy layer, in (1) formula
Resonance wavelength res can change with the variation of gold-palldium alloy refractive index.
Hydrogen is put into gas chamber (known density of hydrogen is 4%).When light meets in gas chamber with first LPG, a part
Luminous energy is coupled in cladding mode with obtaining resonance wavelength res in (1) formula, and by the transmitting of one section of optical fiber, this part luminous energy is second
It is re-coupled in core mode at a LGP by cladding mode.After through second LPG, original core mode and with covering coupling
Core mode after conjunction interferes, and transmitted spectrum is rendered as the form of interference fringe.In LPGP, transmission coefficient can be with table
It is existing are as follows:
α is the rate of cladding mode losses, T in formulasingleFor the transmission coefficient of single LPG, RsingleFor the reflection system of single LPG
Number, ψ is phase.The length in path is related between core mode after wherein ψ is coupled with original core mode and again, and relationship can
To show themselves in that
L is grating space in formula.
By formula (2) and formula (3) it is found that the phase of LPGP interference spectrum be byInfluence.When effective folding of cladding mode
When the rate of penetrating changes, LPGP output spectrum can change therewith.
So gold-palladium alloy layer and the hydrogen of cladding surface react, and cladding mode has when injecting hydrogen to gas chamber (3)
Effect refractive index changes therewith, this will result directly in peak wavelength in LPGP transmitted spectrum and is subjected to displacement, and pass through simple computation
It can measure within a short period of time in environment with the presence or absence of hydrogen.
The beneficial effects of the present invention are: main as sensor using Mach-Zehnder LPG optical fiber structure in design of the invention
Structure, by palladium to the unique selection of hydrogen and the central wavelength of transmitted spectrum and the functional relation of density of hydrogen based on, and
Safely, conveniently the advantages of, to have in environment no hydrogen carry out precise measurement.It is able to achieve quickly repeatedly measurement, and measurement sensitivity
It is higher, there is very strong innovative and practical value, there is good application prospect.
Detailed description of the invention
Fig. 1 is the long-period fiber grating hydrogen detector structural schematic diagram based on Mach-Zender interferometer.
Fig. 2 is Mach-Zehnder optical fiber structure schematic diagram.
Specific embodiment
Long-period fiber grating hydrogen detector based on Mach-Zender interferometer, by wideband light source (1), fiber coupling
Device (2), gas chamber (3), air inlet (4), gas outlet (5), Mach-Zehnder LPG optical fiber structure (6), palladium-gold-palladium-gold-palladium
Alloy-layer (7), test chamber (8), photodiode (9), power amplifier module (10), loudspeaker (11) composition；Its feature exists
In: wideband light source (1) is connected to Mach-Zehnder LPG optical fiber structure (6) by optical fiber and fiber coupler (2), and Mach-was once
Dare LPG optical fiber structure (6) is fixed in closed lighttight gas chamber (3), and (6) two sections of Mach-Zehnder LPG optical fiber structure
LGP centre distance is 50 millimeters, and grating length is 20 millimeters, and screen periods are 500 microns, Mach-Zehnder LPG optical fiber knot
The fiber bragg grating center wavelength of structure (6) is 1550 nanometers, and palladium-gold-palladium-gold-palladium alloy layer (7) is with a thickness of 100 nanometers, palladium-
Palladium layers are in gold-palladium-gold-palladium alloy layer (7) with a thickness of 10-20 nanometers, and layer gold thickness range is 20-30 nanometers, palladium-gold-palladium-
Gold-palladium alloy layer (7) is 70 millimeters along optical fiber axial direction length；It is connected to by fiber coupler (2) and optical fiber based on photoelectricity two
The test chamber (8) of pole pipe (9), when the density of hydrogen in gas chamber (3) changes, interference light that photodiode (9) receives
Signal strength changes, so that the electric current generated changes, the relationship of density of hydrogen and curent change is obtained, photoelectricity two
The electric signal input power amplification module (8) that pole pipe (9) generates, amplified electric signal pass through integrated transporting discharging core in the module
Piece is compared with setting value, realizes alarm by loudspeaker (9) after the threshold exceeded.
Claims (1)
1. the long-period fiber grating hydrogen detector based on Mach-Zender interferometer, by wideband light source (1), fiber coupler
(2), gas chamber (3), air inlet (4), gas outlet (5), Mach-Zehnder LPG optical fiber structure (6), palladium-gold-palladium-gold-palldium alloy
Layer (7), test chamber (8), photodiode (9), power amplifier module (10), loudspeaker (11) composition；It is characterized by: broadband
Light source (1) is connected to Mach-Zehnder LPG optical fiber structure (6), Mach-Zehnder LPG by optical fiber and fiber coupler (2)
Optical fiber structure (6) is fixed in closed lighttight gas chamber (3), (6) two sections of centers LGP of Mach-Zehnder LPG optical fiber structure away from
From being 50 millimeters, grating length is 20 millimeters, and screen periods are 500 microns, the optical fiber of Mach-Zehnder LPG optical fiber structure (6)
Raster center wavelength is 1550 nanometers, and palladium-gold-palladium-gold-palladium alloy layer (7) is with a thickness of 100 nanometers, palladium-gold-palladium-gold-palladium
Palladium layers are in alloy-layer (7) with a thickness of 10-20 nanometers, and layer gold thickness range is 20-30 nanometers, palladium-gold-palladium-gold-palladium alloy layer
It (7) is 70 millimeters along optical fiber axial direction length；The inspection based on photodiode (9) is connected to by fiber coupler (2) and optical fiber
It surveys chamber (8), when the density of hydrogen in gas chamber (3) changes, the interference light signal intensity that photodiode (9) receives occurs
Variation obtains the relationship of density of hydrogen and curent change so that the electric current generated changes, and photodiode (9) are generated
Electric signal input power amplification module (8), amplified electric signal in the module pass through integrated transporting discharging chip and setting value
It is compared, realizes alarm by loudspeaker (9) after the threshold exceeded.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114354546A (en) * | 2021-12-31 | 2022-04-15 | 北京景通科信科技有限公司 | Mine gas concentration detection system based on optical fiber sensing |
Citations (3)
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| CN102608071A (en) * | 2012-02-21 | 2012-07-25 | 中国计量学院 | M-Z type hydrogen sensing head based on femto-second laser micro-machined hollow PBGF with written-in LPGs |
| CN108844921A (en) * | 2018-09-12 | 2018-11-20 | 中国计量大学 | Sensor based on hydrogen in MZ interference inclined optical fiber grating measuring transformer |
| CN209589839U (en) * | 2018-12-10 | 2019-11-05 | 中国计量大学 | Long-period fiber grating hydrogen based on Mach-Zender interferometer detects detector |
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2018
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| CN102608071A (en) * | 2012-02-21 | 2012-07-25 | 中国计量学院 | M-Z type hydrogen sensing head based on femto-second laser micro-machined hollow PBGF with written-in LPGs |
| CN108844921A (en) * | 2018-09-12 | 2018-11-20 | 中国计量大学 | Sensor based on hydrogen in MZ interference inclined optical fiber grating measuring transformer |
| CN209589839U (en) * | 2018-12-10 | 2019-11-05 | 中国计量大学 | Long-period fiber grating hydrogen based on Mach-Zender interferometer detects detector |
Non-Patent Citations (4)
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| DONATO LUNA-MORENO ET.AL: "Tailored Pd–Au layer produced by conventional evaporation process for hydrogen sensing", 《OPTICS ANDLASERSINENGINEERING》, vol. 49, pages 693 - 697, XP028188329, DOI: 10.1016/j.optlaseng.2010.12.015 * |
| YANG FANG ET.AL: "Pd-Ag film coated LPG for hydrogen sensing", 《PROC. OF SPIE》, vol. 8409, pages 6 * |
| 沈常宇等: "表面等离子共振氢气传感研究进展", 《中国计量大学学报》, vol. 28, no. 1, pages 7 - 16 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114354546A (en) * | 2021-12-31 | 2022-04-15 | 北京景通科信科技有限公司 | Mine gas concentration detection system based on optical fiber sensing |
| CN114354546B (en) * | 2021-12-31 | 2024-03-22 | 北京景通科信科技有限公司 | Mine gas concentration detection system based on optical fiber sensing |
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