CN109001155A - A kind of humidity measuring method based on low gain low noise optical fiber cavity attenuation and vibration technique - Google Patents
A kind of humidity measuring method based on low gain low noise optical fiber cavity attenuation and vibration technique Download PDFInfo
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- CN109001155A CN109001155A CN201810854585.1A CN201810854585A CN109001155A CN 109001155 A CN109001155 A CN 109001155A CN 201810854585 A CN201810854585 A CN 201810854585A CN 109001155 A CN109001155 A CN 109001155A
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- optical fiber
- fiber
- ring
- relative humidity
- coupler
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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
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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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
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
- G01N2021/396—Type of laser source
Abstract
The invention discloses a kind of humidity measuring methods based on low gain low noise optical fiber cavity attenuation and vibration technique, with the variation of gas relative humidity in alignment gas chamber, fiber optic loop cavity loss changes therewith, corresponding change occurs for the die-away time of pulse signal, the ring-down time of corresponding calibrating gas sample is obtained by detection according to the calibrating gas sample of relative humidity known to multiple groups, establish the linear relationship curve of relative humidity and ring-down time, then the relative humidity of under test gas sample is obtained according to the ring-down time of the under test gas sample measured and the linear relationship curve of combination relative humidity and ring-down time.The present invention has many advantages, such as that high sensitivity, measurement range are wide, it is fast, easy to operate, at low cost to analyze speed, facilitates real-time monitoring, can be used for measuring relative air humidity, provide conveniently for fields such as industry monitoring, environmental monitoring, medical diagnosis.
Description
Technical field
The invention belongs to relative humidity measurement technical fields, and in particular to one kind is based on low gain low noise optical fiber cavity-type BPM
The humidity measuring method of technology.
Background technique
Currently, light fibre humidity transducer has fiber evanescent wave humidity sensor, fiber grating humidity sensor, fiber F-P cavity wet
Degree sensing etc..Fiber evanescent wave humidity sensor is compact-sized and small volume, is suitable for in-site measurement.But air humidity is larger
When measurement accuracy it is poor, and as humidity rises, other measurement methods is needed to assist, thus measurement range also needs further to grind
Study carefully.Fiber bragg grating temperature sensor sensitivity is higher, but temperature, humidity, bending, strain, refractive index etc. intersect impact sensing
Very big, demodulation is difficult, and measurement accuracy is caused to substantially reduce.Fiber F-P cavity humidity sensor can carry out Wavelength demodulation, but volume is huge
Greatly, cost is higher.Optical fiber cavity attenuation and vibration technique, it is high-precision, highly sensitive and do not received extensively by the characteristic of light source influence of fluctuations
Concern and research, disadvantage mentioned above can effectively be overcome by carrying out moisture measurement with optical fiber ring cavity attenuation and vibration technique, however, not having still at present
There is the correlative study of this aspect to report.
Summary of the invention
The present invention be solve in the prior art the other factors such as humidity measurement system structure is complicated, temperature intersection sensing,
The problems such as precision is low and at high cost and provide a kind of humidity measuring method based on low gain low noise optical fiber cavity attenuation and vibration technique,
This method by analyze, study decline swing cavity configuration under relative humidity change caused by the light decay of optical attenuation swing signal and realize phase
Measurement to humidity, with high sensitivity, measurement range is wide, it is fast, easy to operate, at low cost to analyze speed, facilitates real-time monitoring
The advantages that, it can be used for measuring relative air humidity, be provided conveniently for fields such as industry monitoring, environmental monitoring, medical diagnosis.
The present invention adopts the following technical scheme that one kind is declined based on the optical fiber cavity of low gain low noise to solve above-mentioned technical problem
Swing the humidity measuring method of technology, it is characterised in that: by passing sequentially through the first connected fiber coupler of optical fiber, 3.6km single mode
Optical fiber, erbium-doped fiber amplifier, the second isolator, alignment gas chamber and the second fiber coupler constitute optical fiber ring cavity, the first optical fiber
Coupler passes sequentially through optical fiber and connect with the first isolator and laser source, which passes sequentially through route and semiconductor laser tune
Device processed is connected with signal source, and the second fiber coupler is connected by optical fiber with photodetector, which passes through route
It is connected with oscillograph, accesses semiconductor laser modulator, semiconductor laser modulator control when signal source generates a series of impulse waves
The output power and wavelength of laser source processed, it is modulated after optical pulse train via the first isolator and the first fiber coupler
10% port is coupled in optical fiber loop, successively by 3.6km single mode optical fiber, erbium-doped fiber amplifier, the second isolator and right
Quasi- gas chamber, 90% output light accesses the first fiber coupler through the second fiber coupler in optical fiber ring cavity, in optical fiber ring cavity
10% output light accesses photodetector by optical fiber loop through the second fiber coupler, the output periodic sequence for the pulse that decays
Electric signal is converted by photodetector, is eventually displayed on digital oscilloscope, filled with mark gaseous sample in alignment gas chamber
Or under test gas sample, with the change of gas relative humidity in alignment gas chamber, fiber optic loop cavity loss is changed correspondingly, pulse letter
Number die-away time occur it is corresponding change, corresponding mark is obtained by detection according to the calibrating gas sample of relative humidity known to multiple groups
The ring-down time of quasi- gaseous sample establishes the linear relationship curve of relative humidity and ring-down time, then to be measured according to measuring
The ring-down time of gaseous sample simultaneously combines relative humidity and the linear relationship curve of ring-down time to obtain the phase of under test gas sample
To humidity.
Preferably, the erbium-doped fiber amplifier is by the Er-doped fiber of one section of low gain, pump laser and three ports
WDM coupler composition, Er-doped fiber, pump laser and the light pulse of WDM coupler output of low gain are connect respectively in WDM coupling
Three ports of clutch.
Preferably, port, respectively light inlet, light-emitting window, air inlet and air outlet there are four the alignment gas chamber tools,
Middle light inlet is connected by optical fiber with the second isolator, and light-emitting window passes through optical fiber and is connected with the second fiber coupler, air inlet and
Calibrating gas sample or under test gas sample communicate, and gas outlet is communicated with gas collector or ambient atmosphere.
Compared with the prior art, the invention has the following beneficial effects:
1, the invention proposes a kind of humidity measuring methods based on low gain low noise optical fiber cavity attenuation and vibration technique, effectively solve
Current moisture measurement of having determined is difficult to realize highly sensitive and better stability problem simultaneously；
2, the present invention reduces noise in wave distortion and compensated optical fiber ring cavity using low gain and low noise Er-doped fiber
Decaying；
3, the present invention increases pulse peak number come compensated optical fiber ring cavity internal loss using erbium-doped fiber amplifier to improve relatively
The measurement accuracy of humidity；
4, present invention finds have good linear relationship between ring-down time and relative humidity；
5, measurement process of the present invention simplifies, convenient rapid, effectively overcomes numerous present in conventional moisture measurement method
The defect of trivial process and higher cost.
Detailed description of the invention
Fig. 1 is the optical path connection figure of humidity measurement system in the present invention；
Fig. 2 is the structural schematic diagram of erbium-doped fiber amplifier in the present invention.
In figure: 1- signal source, 2- semiconductor laser modulator, 3- laser source, the first isolator of 4-, the first fiber coupling of 5-
Device, 6-3.6km single mode optical fiber, 7- erbium-doped fiber amplifier, the second isolator of 8-, 9- are directed at gas chamber, the second fiber coupling of 10-
Device, 11- photodetector, 12- oscillograph, 13- optical fiber.
Specific embodiment
Above content of the invention is described in further details by the following examples, but this should not be interpreted as to this
The range for inventing above-mentioned theme is only limitted to embodiment below, and all technologies realized based on above content of the present invention belong to this hair
Bright range.
Embodiment
A kind of humidity measuring method based on low gain low noise optical fiber cavity attenuation and vibration technique, is connected by passing sequentially through optical fiber 13
The first fiber coupler 5,3.6km single mode optical fiber 6, erbium-doped fiber amplifier 7, the second isolator 8, alignment gas chamber 9 and second
Fiber coupler 10 constitutes optical fiber ring cavity, and erbium-doped fiber amplifier 7 is by the Er-doped fiber of one section of low gain, pump laser and three
The WDM coupler of port forms, and Er-doped fiber, pump laser and the light pulse of WDM coupler output of low gain connect respectively
In three ports of WDM coupler, the first fiber coupler 5 passes sequentially through optical fiber 13 and the first isolator 4 and laser source 3 connects
It connects, which passes sequentially through route and be connected with semiconductor laser modulator 2 and signal source 1, and the second fiber coupler 10 passes through
Optical fiber 13 is connected with photodetector 11, which is connected by route with oscillograph 12, when signal source 1 generates one
Series of pulses wave accesses semiconductor laser modulator 2, and semiconductor laser modulator 2 controls the output power and wavelength of laser source 3,
Optical pulse train after modulated is coupled in optical fiber loop via 10% port of the first isolator 4 and the first fiber coupler 5,
Successively pass through 3.6km single mode optical fiber 6, erbium-doped fiber amplifier 7, the second isolator 8 and be directed at gas chamber 9,90% in optical fiber ring cavity
Output light access the first fiber coupler 5 through the second fiber coupler 10,10% output light is through the second light in optical fiber ring cavity
Fine coupler 10 accesses photodetector 11 by optical fiber loop, and the output periodic sequence for the pulse that decays is by 11 turns of photodetector
It changes electric signal into, is eventually displayed on digital oscilloscope 12, there are four ports, respectively light inlet, out light for alignment gas chamber 9 tool
Mouthful, air inlet and air outlet, wherein light inlet is connected by optical fiber 13 with the second isolator 8, and light-emitting window passes through optical fiber 13 and the
Two fiber couplers 10 are connected, and air inlet is communicated with calibrating gas sample or under test gas sample, and gas outlet and gas collection fill
It sets or ambient atmosphere communicates, filled with mark gaseous sample or under test gas sample in alignment gas chamber 9, with gas in alignment gas chamber
The variation of body relative humidity, fiber optic loop cavity loss change therewith, and corresponding change occurs for the die-away time of pulse signal, according to more
The calibrating gas sample of the known relative humidity of group obtains the ring-down time of corresponding calibrating gas sample by detection, establishes relatively wet
The linear relationship curve of degree and ring-down time, then according to the ring-down time of the under test gas sample measured and in conjunction with relative humidity
The relative humidity of under test gas sample is obtained with the linear relationship curve of ring-down time.
The principle of the present invention is based on fiber optic loop Research on Cavity Ring Down Spectroscopy, and a series of impulse waves that signal source generates pass through " mould
Quasi- modulation input " port is transported to semiconductor laser modulators modulate into pulsed light, enters fiber optic loop through the first fiber coupler
Chamber, by the intracavitary 3.6km single mode optical fiber of fiber optic loop, erbium-doped fiber amplifier, the second fibre optic isolater, alignment gas chamber, from second
One end of fiber coupler comes out, and accesses photodetector.In order to improve the measurement accuracy of ring-down time, it is necessary to increase pulse
Number.So with an erbium-doped fiber amplifier come the loss of compensated optical fiber loop.Pass through the amplification of different length Er-doped fiber
Device experiment, it is found that laser can be generated by Er-doped fiber is too long, and Er-doped fiber is too short, and gain is inadequate, the pulse spacing is smaller.Therefore,
The image intensifer and 980nm pump laser of the Er-doped fiber that length is 2m have been built in laboratory.Under the same conditions, it compares
Be placed on the decaying spectrum of the EDFA of inside and outside of cavity, when EDFA is placed on it is intracavitary when, the peak strength of pulse signal is bigger,
It is more, it is more advantageous to and detects ring-down time.Compared with conventional CRD signal processing, intracavitary declining to swing and be with EDFA
System is greatly improved to the raising of moisture measurement sensitivity.
Temporal analysis is usually to determine fiber optic loop by monitoring the Decay for the light pulse for being introduced into optical fiber circuit
Light loss in road.In FLRDS system, the pulsed light of modulation enters optical fiber loop by the first fiber coupler, then exists
It is repeatedly round-trip in optical fiber loop, in each two-way process, swings a small amount of light of cavity loss since optical fiber declines and can lose, result
It is that light in annular chamber is exponentially decayed at any time, optical cavity ring-down signal may be expressed as:
It=I0exp(-t/τ) (1)
Wherein I0For initial beam intensity, τ is the optical cavity ring-down time.
Damped exponential signals are obtained by the small amount of leakage light of the second coupler every time by photodetector detection record.?
Relative humidity measurement experiment in, optical fiber decline swing it is intracavitary decaying change with the variation of relative humidity, when the loss in annular chamber
Lower, die-away time, τ was bigger.Therefore τ reflects the loss as caused by relative humidity thickness change, and can be by measuring τ
It obtains.The die-away time τ of optical cavity is defined as the time needed for light decay reduces to the 1/e of its initial strength, which is
In formula, d is the length of optical fiber ring cavity, and c is the light velocity, and n is the refractive index of optical fiber ring cavity, and A is each cavity-type BPM process
In total losses, decline including optical fiber and swing the loss that chamber inherent loss and camera lens are docked with high reflecting mirror surface.It is intracavitary in fiber annular,
The inherent loss of optic fiber ring-shaped cavity is damaged mainly from the scattering of the absorption of optical fiber ring cavity, the insertion loss of fiber coupler, optical fiber
The junction loss of consumption and optical fiber.
Photodetector and oscillograph are used to monitor deamplification round-trip every time and record and analyze data, and then are declined
Swing the relationship of time and relative humidity.The experimental results showed that the erbium-doped fiber amplifier of low gain low noise Er-doped fiber is added
Decline swing intracavitary progress signal amplification when, the sensitivity that pulse number can be increased, improve moisture measurement, and different humidity pair
First peak atenuation absorption of the output signal answered has exponent relation, and meets 1550nm laser to the absorbing rule of steam.From knot
The sensitivity that fruit can be seen that the FLRDS system is 4.61538, and the related coefficient of matched curve is 0.99399, relative to hair
Hairdo, measurement with wet, moisture measurement precision is higher, and solve in optical fiber type sensing measurement high humility temperature, strain etc. because
Element intersects the problem of sensing, improves the stability of measuring system.In addition, the fiber annular cavity ring-down spectroscopy system structure is tight
It gathers, is low in cost, convenient for real-time measurement, can be used for measuring relative air humidity, being industry monitoring, environmental monitoring, medical diagnosis
It is convenient that equal fields provide.
Embodiment above describes basic principles and main features of the invention and advantage, the technical staff of the industry should
Understand, the present invention is not limited to the above embodiments, and the above embodiments and description only describe originals of the invention
Reason, under the range for not departing from the principle of the invention, various changes and improvements may be made to the invention, these changes and improvements are each fallen within
In the scope of protection of the invention.
Claims (3)
1. a kind of humidity measuring method based on low gain low noise optical fiber cavity attenuation and vibration technique, it is characterised in that: by passing sequentially through
The first connected fiber coupler of optical fiber, 3.6km single mode optical fiber, erbium-doped fiber amplifier, the second isolator, alignment gas chamber and the
Two fiber couplers constitute optical fiber ring cavity, and the first fiber coupler passes sequentially through optical fiber and connect with the first isolator and laser source,
The laser source passes sequentially through route and is connected with semiconductor laser modulator and signal source, and the second fiber coupler passes through optical fiber and light
Electric explorer is connected, which is connected by route with oscillograph, when signal source generates a series of impulse wave accesses half
Conductor Laser modulator, the output power and wavelength of semiconductor laser modulator control laser source, it is modulated after optical pulse train
10% port via the first isolator and the first fiber coupler is coupled in optical fiber loop, and 3.6km single-mode optics are successively passed through
Fibre, erbium-doped fiber amplifier, the second isolator and alignment gas chamber, 90% output light is through the second fiber coupler in optical fiber ring cavity
Access the first fiber coupler, 10% output light is visited through the second fiber coupler by optical fiber loop access photoelectricity in optical fiber ring cavity
Device is surveyed, the output periodic sequence for the pulse that decays is converted into electric signal by photodetector, is eventually displayed on digital oscilloscope,
It is aligned in gas chamber filled with mark gaseous sample or under test gas sample, with the change of gas relative humidity in alignment gas chamber,
Fiber optic loop cavity loss changes correspondingly, and corresponding change occurs for the die-away time of pulse signal, according to relative humidity known to multiple groups
Calibrating gas sample obtains the ring-down time of corresponding calibrating gas sample by detection, establishes the line of relative humidity and ring-down time
Then sexual intercourse curve according to the ring-down time of under test gas sample measured and combines the linear of relative humidity and ring-down time
Relation curve obtains the relative humidity of under test gas sample.
2. the humidity measuring method according to claim 1 based on low gain low noise optical fiber cavity attenuation and vibration technique, feature
Be: the erbium-doped fiber amplifier by the Er-doped fiber of one section of low gain, pump laser and three ports WDM coupler group
Meet three in WDM coupler respectively at the light pulse of Er-doped fiber, pump laser and WDM the coupler output of, low gain
Port.
3. the humidity measuring method according to claim 1 based on low gain low noise optical fiber cavity attenuation and vibration technique, feature
Be: there are four ports, respectively light inlet, light-emitting window, air inlet and air outlet for the alignment gas chamber tool, and wherein light inlet is logical
It crosses optical fiber to be connected with the second isolator, light-emitting window is connected by optical fiber with the second fiber coupler, air inlet and calibrating gas sample
Product or under test gas sample communicate, and gas outlet is communicated with gas collector or ambient atmosphere.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110873589A (en) * | 2019-12-06 | 2020-03-10 | 河南师范大学 | Fiber ring cavity ring-down temperature and humidity measurement method based on TDM technology |
| WO2021128668A1 (en) * | 2020-02-04 | 2021-07-01 | 中国计量科学研究院 | Gas quantitative detection device and method |
| CN114812630A (en) * | 2022-07-01 | 2022-07-29 | 中北大学 | Double-parameter in-situ sensor based on waveguide grating, sensing system and preparation method |
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| CN107991259A (en) * | 2017-12-19 | 2018-05-04 | 河南师范大学 | A kind of cavity ring-down spectroscopy humidity measurement system based on intracavitary amplification |
| CN207557107U (en) * | 2017-12-19 | 2018-06-29 | 河南师范大学 | A kind of cavity ring-down spectroscopy humidity measurement system based on intracavitary amplification |
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| CN107991259A (en) * | 2017-12-19 | 2018-05-04 | 河南师范大学 | A kind of cavity ring-down spectroscopy humidity measurement system based on intracavitary amplification |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110873589A (en) * | 2019-12-06 | 2020-03-10 | 河南师范大学 | Fiber ring cavity ring-down temperature and humidity measurement method based on TDM technology |
| WO2021128668A1 (en) * | 2020-02-04 | 2021-07-01 | 中国计量科学研究院 | Gas quantitative detection device and method |
| US11761887B2 (en) | 2020-02-04 | 2023-09-19 | National Institute Of Metrology, China | Apparatus and method for quantitative detection of gases |
| CN114812630A (en) * | 2022-07-01 | 2022-07-29 | 中北大学 | Double-parameter in-situ sensor based on waveguide grating, sensing system and preparation method |
| CN114812630B (en) * | 2022-07-01 | 2022-09-20 | 中北大学 | Double-parameter in-situ sensor based on waveguide grating, sensing system and preparation method |
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Application publication date: 20181214 |