CN1168972A - Spectrum modulation type biconical optical fiber sensor signal detection method - Google Patents

Spectrum modulation type biconical optical fiber sensor signal detection method Download PDF

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Publication number
CN1168972A
CN1168972A CN 97112576 CN97112576A CN1168972A CN 1168972 A CN1168972 A CN 1168972A CN 97112576 CN97112576 CN 97112576 CN 97112576 A CN97112576 A CN 97112576A CN 1168972 A CN1168972 A CN 1168972A
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biconical
optical fiber
peak
transmission
fiber
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CN 97112576
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彭江得
陈智浩
顾东华
刘小明
唐平生
周炳琨
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Tsinghua University
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Tsinghua University
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Abstract

This invention relates to a new signal detecting method by spectrum modulating type biconical optical fiber sensor. The method is based on the principle that displacement (delta lambda) of relevant wavelengy of one or several valley (or peak) of transmissive spectrum from the biconical optical fiber filler responds linearly to variation (delt N) of index of refraction of the surrounding substance/ Comparig with prior luminous strengh modulating biconicul optical fiber sensor. the new biconical optical fiber sensor is not under the influnence of the influnence fo the rising and falling of system power and the changing of loss in photo-loop. It can also realize the sence measure for multiple-parameter in real time simultaneously.

Description

Spectrum modulation type biconical optical fiber sensor signal detection method
The invention belongs to the photoelectron technology field, particularly a kind of new spectrum modulation type biconical optical fiber sensor signal detection method.
Biconical fiber is heated to softening back with a section single-mould fiber localized hyperthermia and stretches along the mandrel direction and form, geometric configuration as shown in Figure 1,11 is fibre cladding, 12 is fiber cores, 13 is the pyrometric cone district.Because awl district's diameter (comprising core diameter) is received thin, the distribution of transmission light wave mould field changes in optical fiber, will produce basic mode in the fibre core and the energy conversion between the cladding mode, will " ooze out " covering-air interface by the cladding mode evanescent field of exponential damping.As the optical taper district being placed the material of refractive index less than cladding index, then will cause the decay of transmitting " leakage " of light-wave energy in the optical fiber and causing transmitting optical power, and its damping capacity increases with the increase of external substance refractive index, and the variation of measuring the biconical fiber Output optical power can be learnt the refractive index of external substance.In addition, when biconical fiber is subjected to the external force effect and when crooked, can causes that also this " leakages " loss increases, the variation of measurement biconical fiber Output optical power can be learnt the size of ambient pressure.The principle of work of Here it is normal optical modulation type biconical optical fiber sensor.Utilize biconical fiber to make sensor and can measure the physics of liquid substance, chemistry even biological parameter.
The example of typical light intensity modulation type biconical optical fiber sensor is just like Britain＜electronics wall bulletin〉the 20th phase of volume nineteen ninety-five the 31st is contained＜single-mode fiber surface plasma-wave chemical sensor 〉, the U.S.＜optics letter〉and the 16th the 2nd phase of volume in 1991 is contained＜pressure transducer that utilizes crooked bipyramid single-mode fiber to constitute〉etc.The poor anti jamming capability of this intensity modulation type biconical optical fiber sensor is subjected to the influence of factors such as light source power fluctuation and optical path loss variation easily.For the purpose of practicality, when measuring, must adopt compensation technique to eliminate the influence of various labile factors.This has not only increased the complicacy of sensing technology, and cost is improved, and compensation technique itself also can be brought new problem.
The objective of the invention is to for overcoming the weak point of prior art, a kind of new spectrum modulation type biconical Fibre Optical Sensor signal detecting method is proposed, the characteristic of wavelength shift takes place in the transmission spectrum that it is based on biconical fiber with the change of external substance parameter, has the measuring accuracy height, working stability, and can realize advantages such as a plurality of parameters measurements in real time simultaneously.
Biconical fiber can be subjected to the modulation of exterior materials parameter except aforementioned monochromatic light transmitting optical power, also has an important characteristic, promptly because core-conversion of awl district cladding mode and covering in " leakage " of transmission light-wave energy all relevant with optical wavelength, thereby its output characteristics is to the unusual sensitivity of wavelength.For a monochromatic source, the output power of biconical fiber with the growth in awl district and awl waist attenuate and periodically increase and decrease; For a wideband light source, then the output power spectrum of biconical fiber will present periodic oscillations characteristic.Therefore, utilize biconical fiber can constitute a unreflected optical filter.Fig. 2 provides the transmission spectrum of a typical case 1.5 mu m waveband biconical fiber wave filters, and visible light transmission paddy is sharper than transmission peaks, and 5 corresponding wavelength of transmission paddy are respectively λ 01, λ 02, λ 03, λ 04And λ 05When biconical fiber periphery during around the refraction index changing of material, the position of transmission paddy (or peak) (being corresponding wavelength) also will produce skew.The inventor is from theoretical proof: the biconical fiber periphery around the scope of material refractive index less than fibre cladding refractive index (～1.45) in, the displacement λ of transmission paddy (or peak) respective wavelength is with linear around the changes delta N of material refractive index.Fig. 3 provides its theoretical curves, wherein gets reference wavelength λ 0=1535nm, initial refractive index N 0=1.31 (corresponding to true origin).Therefore, measure the displacement of transmission paddy (or peak) respective wavelength, can determine the refractive index of periphery around material.As biconical fiber is soaked in the fluent meterial, because the refractive index of solution is the function of multiple physical quantitys such as concentration, temperature and pressure, thereby utilize biconical fiber filter transmission spectrum to the susceptibility of periphery around the material refractive index variation, can realize sensing measurement to physical quantitys such as concentration, temperature and pressure.
Based on the above-mentioned theory result of study, experiment confirm the displacement of biconical fiber transmission paddy (or peak) respective wavelength linear response that periphery is changed around material refractive index.
For this reason, the present invention proposes the single parameter signals real-time detection method of a kind of spectrum modulation type biconical optical fiber sensor, it is characterized in that may further comprise the steps:
Described biconical fiber wave filter is immersed in known parameter N 0Material in, choose the corresponding wavelength X of a transmission paddy (or peak) 0As demarcating with reference to putting, when tested parameter N changes, corresponding shifted by delta λ=λ-λ will take place in this reference wavelength 0,, can determine tested parameter N by (1) formula by the offset λ of witness mark wavelength.
The present invention can be that described biconical fiber wave filter with a plurality of transmission paddy (or peak) is immersed in known M parameter X for real-time its step of sensing measurement simultaneously of described many reference amounts also 01, X 02... X 0MMaterial in, in transmission spectrum, choose the corresponding wavelength (λ of the different transmission paddy (or peak) of M sensitivity 01, λ 02... λ 0M) as calibrating with reference to putting.When one or more the changing in M the parameter, because of the refractive index of material with change, cause that M transmission paddy (or peak) value corresponding reference wavelength is offset.By measuring the amount of movement Δ λ of M reference wavelength 1, Δ λ 2..., Δ λ N, can determine M tested parameter by (3) formula.
Biconical fiber wave filter of the present invention adopts single-mode fiber localized hyperthermia to fuse drawing and forms, by structure parameters such as control biconical fiber awl length, tapering and awl waist under the logical light detection of wideband light source, selected light source wave spectrum is formed one or more transmission paddy (or peak).
In described biconical fiber wave filter, also can introduce enhanced sensitivity mechanism, further improve sensing sensitivity.
Described enhanced sensitivity mechanism can adopt and reduce to bore waist diameter, increase optical fiber cone angle and length with narrower many paddy (peak) transmission spectrum of acquisition bandwidth, or adopts many awl cascades to obtain more single paddy (peak) transmission spectrum of narrow bandwidth.
Described enhanced sensitivity mechanism also can be by realizing at awl district optical fiber outside surface plating enhanced sensitivity material (as aluminium, biological membrane etc.) film.
Principle of work of the present invention is as follows:
In biconical fiber filter transmission spectrum, get the position of a transmission paddy (or peak) as the reference wavelength X 0(since transmission paddy is generally sharper than transmission peaks, chooses transmission paddy point for referencial use and can obtain higher resolution), when periphery around material refractive index from N 0When becoming N, reference wavelength will be from λ 0Move on to λ 1, and the displacement λ of reference wavelength=λ 1-λ 0With changes delta N=N-N around material refractive index 0Linear:
K is a proportionality constant in Δ N=K Δ λ (1) formula, is decided by the structure parameter (numerical aperture, core diameter etc.) of optical fiber and the structure parameter of optical taper (awl length, tapering and awl waist etc.), can be by measuring.By to known substance refractive index N 0Demarcation, measure Δ λ and can determine unknown change of refractive Δ N around material.
Many reference amounts described in said method sensing measurement simultaneously can utilize the biconical fiber wave filter with a plurality of transmission paddy (or peak) to realize.For M parameter X 01, X 02... X 0MSensing, can in transmission spectrum, get the corresponding wavelength (λ of the different transmission paddy (or peak) of M sensitivity 01, λ 02... λ 0M) as with reference to the point.When one or more the changing in M the parameter, the refractive index N of material follows change, causes that M transmission paddy (or peak) corresponding reference wavelength is offset, and can be write out by formula (1):
ΔN 1＝f 11(X 1-X 01)+f 12(X 2-X 02)+...+f 1M(X M-X 0M)＝K 1Δλ 1
ΔN 1＝f 21(X 1-X 01)+f 22(X 2-X 02)+...+f 2M(X M-X 0M)＝K 2Δλ 2
(2)
Δ N M=f M1(X 1-X 01)+f M2(X 2-X 02)+...+f MM(X M-X 0M)=K MΔ λ MFrom the physical relation of strictness, the f in the formula Ij(i, j=1,2 ... M) should be expressed as variations in refractive index and M parameter X respectively 01, X 02, X 0MRelevant function (not necessarily constant).Obtain thus:
F 11(X 1-X 01)+F 12(X 2-X 02)+...+F 1M(X M-X 0M)＝Δλ 1
F 21(X 1-X 01)+F 22(X 2-X 02)+...+F 2M(X M-X 0M)＝Δλ 2
(3)
F M1(X 1-X 01)+F M2(X 2-X 02)+...+F MM(X M-X 0M)=Δ λ MOr be abbreviated as Σ j F ij ( X j - X 0 j ) = Δ λ i - - - ( 3 ′ ) F in the formula Ij=f Ij/ K iBe the reference wavelength skew sensing transforming function transformation function of i reference point to j parameter, all can be by measuring.Like this, measure Δ λ 1, Δ λ 2... Δ λ MJust can obtain the variation delta X of M parameter by (3) formula j=(X j-X 0j).
Compare with normal optical modulation type biconical fiber method for sensing, the present invention has following effect:
The first, the method for sensing that moves based on biconical fiber transmission paddy (or peak) respective wavelength is not subjected to the influence that system power rises and falls and optical path loss changes, thereby the accuracy and reliability of sensing measurement improves greatly.
The second, in view of many paddy (peak) value characteristic of the transmission spectrum of biconical fiber wave filter, same sensor can be realized the real-time while sensing measurement to a plurality of parameters.
In view of the above-mentioned good characteristic of spectrum modulation type biconical optical fiber sensor of the present invention, can obtain important application in oceanographic engineering (measurement of seawater salinity, temperature, pressure), environmental engineering (pollution monitoring) and biomedicine fields such as (sero-immunity detections).
Brief Description Of Drawings:
Fig. 1 is the biconical fiber structural representation.
Fig. 2 is the theoretical curves of biconical fiber wave filter typical case transmission spectrum.
Fig. 3 is the theoretical curves of spectrum modulation type biconical Fibre Optical Sensor characteristic.
Fig. 4 is the transmission spectrum of the biconical fiber wave filter used in the embodiment of the invention 1
Fig. 5 is the Δ S～Δ λ test curve of the spectrum modulation type biconical optical fiber salinity sensor of the embodiment of the invention 1.
Fig. 6 is the transmission spectrum of the biconical fiber wave filter used in the embodiment of the invention 2.
Fig. 7 is the Δ S～Δ λ test curve of the spectrum modulation type biconical optical fiber salinity/temperature sensor of the embodiment of the invention 2.
Fig. 8 is the Δ T～Δ λ test curve of the spectrum modulation type biconical optical fiber salinity/temperature sensor of the embodiment of the invention 2.
The embodiment one that the present invention proposes utilizes above-mentioned measuring method to realize the high resolving power of brine solution concentration is measured.Adopt local the melting of single-mode fiber of 1.5 mu m wavebands to pull into biconical fiber, bore long 17.5mm, awl waist diameter 8 μ m are with Er-doped fiber amplified spont-aneous emission light source, spectrum width 1515～1575nm.Earlier biconical fiber is placed salinity S 0Demarcate in the aqueous solution of=0Wt.%, measure its output spectrum, select the pairing wavelength X of one of them transmission paddy from spectrometer 0=1539.7nm is as the reference wavelength, as shown in Figure 4.Change solution concentration S again, observe output spectrum generation translation from spectrometer, Fig. 5 provides the test curve of salinity Δ S～Δ λ.Can see that brine concentration S and reference wavelength amount of movement Δ λ are linear:
Δ S=S-S 0R is a proportionality constant in=R Δ λ (4) formula, i.e. slope of a curve, the sensing sensitivity of reflection biconical fiber concentration sensor.In the present embodiment, experiment records R=0.72wt.%/nm.
As second embodiment of the present invention, sensing when considering to brine solution concentration S and temperature T.Select the biconical fiber wave filter of a transmission spectrum shown in Figure 6 for use, be placed on known salinity S 0And temperature T 0Brine solution in demarcate, in transmission spectrum, select 2 corresponding wavelength X of transmission paddy that sensitivity is different 01=1527.5nm, λ 02=1549.2nm is as the reference point.Change solution concentration and temperature again, observe output spectrum generation translation from spectrometer, according to (3) formula, concentration S and temperature T and two reference wavelength shifted by delta λ 1With Δ λ 2Relation determine by following formula:
A(S-S 0)+B(T-T 0)＝Δλ 1
C (S-S 0)+D (T-T 0)=Δ λ 2(5) A, B are respectively wavelength X in the formula 01The wavelength shift that place's concentration and temperature variation cause, C, D are respectively wavelength X 02The wavelength shift that place's concentration and temperature variation cause.Should consider its nonlinear relationship when accurately demarcating these parameters, for the sake of simplicity, desirable linear-apporximation.Fig. 7 and 8 provides respectively transmission valley wavelength X 01Δ S～Δ the λ that records 1With Δ T～Δ λ 1Relation curve can be demarcated A=5.42nm/wt.%, B=-0.35nm/wt.% thus.Use the same method to transmission valley wavelength X 02Measure Δ S～Δ λ 2With Δ T～Δ λ 2Relation curve, can demarcate C=6.75nm/ ℃, D=-0.37nm/ ℃.Like this, when concentration and temperature change simultaneously, measure Δ λ 1With Δ λ 2Just can obtain concentration S and temperature T simultaneously by (5) formula.

Claims (6)

1. the single parameter signals real-time detection method of spectrum modulation type biconical optical fiber sensor is characterized in that described biconical fiber wave filter is immersed in known parameter N 0Material in, choose the corresponding wavelength X of a transmission paddy (or peak) 0As demarcating with reference to putting, when tested parameter N changes, corresponding shifted by delta λ=λ-λ will take place in this reference wavelength 0,, can determine tested parameter N by the offset λ of witness mark wavelength.
2. spectrum modulation type biconical optical fiber sensor many reference amounts signal real-time detection method simultaneously, it is characterized in that, be that described biconical fiber wave filter with a plurality of transmission paddy (or peak) is immersed in known M parameter X for the real-time sensing measurement simultaneously of described many reference amounts 01, X 02... X 0MMaterial in, in transmission spectrum, choose the corresponding wavelength (λ of the different transmission paddy (or peak) of M sensitivity 01, λ 02... λ 0M) as calibrating with reference to point, when one or more the changing in M the parameter, because of the refractive index of material with change, cause that M transmission paddy (or peak) value corresponding reference wavelength is offset, by the amount of movement Δ λ of M reference wavelength of measurement 1, Δ λ 2..., Δ λ N, can determine M tested parameter.
3. by claim 1 or 2 described methods, it is characterized in that described biconical fiber wave filter adopts single-mode fiber localized hyperthermia to fuse drawing and forms, by structure parameters such as control biconical fiber awl length, tapering and awl waist under the logical light detection of wideband light source, selected light source wave spectrum is formed one or more transmission paddy (or peak).
4. by claim 1 or 2 described methods, it is characterized in that in described biconical fiber wave filter, introducing enhanced sensitivity mechanism and can improve sensing sensitivity.
5. by the described method of claim 4, it is characterized in that described enhanced sensitivity mechanism can adopt reduces to bore the waist diameter, increases optical fiber cone angle and length obtaining narrower many paddy (peak) transmission spectrum of bandwidth, or adopts many awl cascades to obtain more single paddy (peak) transmission spectrum of narrow bandwidth.
6. by the described method of claim 4, it is characterized in that described enhanced sensitivity mechanism also can be by realizing at awl district optical fiber outside surface plating enhanced sensitivity material film.
CN 97112576 1997-06-27 1997-06-27 Spectrum modulation type biconical optical fiber sensor signal detection method Pending CN1168972A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103868896A (en) * 2014-01-26 2014-06-18 中国科学院长春光学精密机械与物理研究所 Chemical optical fiber sensor self-reference quantization detection method
CN104713660A (en) * 2015-03-13 2015-06-17 天津大学 Optical fiber sensor, manufacturing method and simultaneous measuring method for liquid temperature and refractive index
CN113155744A (en) * 2021-04-26 2021-07-23 广东长光中科生物科技有限公司 Method for quantitatively detecting target protein in serum by micro-nano optical fiber coupler label-free biosensing
CN114543968A (en) * 2022-01-26 2022-05-27 武汉理工大学 Optical fiber bending vibration sensing method and device

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103868896A (en) * 2014-01-26 2014-06-18 中国科学院长春光学精密机械与物理研究所 Chemical optical fiber sensor self-reference quantization detection method
CN104713660A (en) * 2015-03-13 2015-06-17 天津大学 Optical fiber sensor, manufacturing method and simultaneous measuring method for liquid temperature and refractive index
CN113155744A (en) * 2021-04-26 2021-07-23 广东长光中科生物科技有限公司 Method for quantitatively detecting target protein in serum by micro-nano optical fiber coupler label-free biosensing
CN114543968A (en) * 2022-01-26 2022-05-27 武汉理工大学 Optical fiber bending vibration sensing method and device
CN114543968B (en) * 2022-01-26 2023-05-26 武汉理工大学 Optical fiber bending vibration sensing method and device

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