CN103364370B - Annular core optical fiber sensor based on annular chamber decline - Google Patents
Annular core optical fiber sensor based on annular chamber decline Download PDFInfo
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- CN103364370B CN103364370B CN201310277333.4A CN201310277333A CN103364370B CN 103364370 B CN103364370 B CN 103364370B CN 201310277333 A CN201310277333 A CN 201310277333A CN 103364370 B CN103364370 B CN 103364370B
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Abstract
The invention provides an annular core optical fiber sensor based on annular chamber decline. Two ends of a section of optical fiber with a large-diameter annular core are respectively connected with one ends with high beam splitting ratios, of two 1*2 optical fiber couplers with high beam splitting ratios; one sides of the two 1*2 optical fiber couplers with one ports are mutually coupled, so as to form an annular chamber; a pulse light source and a detector are respectively connected with one ends with low beam splitting ratios, of the two 1*2 optical fiber couplers. As the optical fiber core of the sensing part of the annular core optical fiber is close to the external environment, and a strong evanescent field is available, the change of the environment such as an external liquid or a gas refractive index can be tested by measuring decline time. By using the sensor, unbeneficial influence caused by light source fluctuation can be reduced to the minimum, a measuring device is simple in structure, light and convenient, high in sensitivity and high in anti-interference capability, and is widely applied to aspects in sensing solution or gas concentration, temperature and the like.
Description
Technical field
What the present invention relates to is a kind of Fibre Optical Sensor, particularly a kind of toroidal cores Fibre Optical Sensor being mainly used in the sensing measurements such as external environment refractive index, gas concentration.
Background technology
Optical cavity decline (CRD, Cavity Ringdown) spectral technique is the technology of a kind of ultra-high sensitive detection absorption spectrum risen late 1980s, there is the impact of not light reception intensity fluctuation and respond the characteristics such as rapid, thus great potential on the optical pressure sensor manufacturing a new generation and sensor-based system.But CRD technology is keep the precision of the collimation property of light path to the reflectivity of catoptron and position adjustment to have very high requirement, is thus difficult to actual coming into operation.
Optic fiber ring-shaped cavity Fading (FLRD, Fiber Loop Ring Down) is the development of traditional C RD technology, and this technology is that Stewart, et al. put forward in calendar year 2001, at first for the measurement of gas concentration at first.It utilizes optical fiber and coupling mechanism to form equivalent light reflection mirror, and the laser of transmission is limited in a fiber, detects the impact of external action on loss by measuring light intensity attenuation to time of threshold values.The physical quantity surveyed due to FLRD sensing technology is the time, without any need for optical amplifier apparatus, can not introduce ASE noise, thus have highly sensitive, reaction velocity is fast, accuracy is high, light source power is low, to the advantage such as light source power stability requirement is low.Also by assembling the sensing head of different structure, realize as multiple sensings such as pressure, temperature, tension force, refractive index, chemical compositions, application has larger dirigibility.These characteristics of FLRD make the Fibre Optical Sensor manufacturing a new generation become possibility.
Summary of the invention
The object of the present invention is to provide a kind of structure simple, light, highly sensitive, the toroidal cores Fibre Optical Sensor based on ring cavity decline that antijamming capability is strong.
The object of the present invention is achieved like this:
One end that one section of two ends with major diameter toroidal cores optical fiber have high splitting ratio respectively 1 × 2 fiber coupler splitting ratio with two is high is connected, two 1 × 2 fiber couplers have the side mutual connection of 1 port, and then formation ring cavity, one end that light-pulse generator and detector are low with the splitting ratio of two 1 × 2 fiber couplers is respectively connected.
The described optical fiber with major diameter toroidal cores is fibre diameter is 125 microns, and fiber core shape is annular, and fibre core wall thickness is 4-8 micron, and the external diameter of toroidal cores is the optical fiber of 80-125 micron, its fiber core refractive index n
corebe greater than cladding index n
clad.
It is described that to have major diameter toroidal cores optical fiber for the length of transducing part be 2-5 centimetre.
Described have major diameter toroidal cores optical fiber and be less than 1 micron for the annular core waveguide distance outside air distance of transducing part.
Described to have major diameter toroidal cores optical fiber be external diameter is the optical fiber of 80-123 micron, carried out the covering of thinning optical fiber, make fibre core be exposed to the external world by the method for chemical etching.
The splitting ratio of described high splitting ratio 1 × 2 fiber coupler is higher than 99:1.
The described major diameter toroidal cores optical fiber that has is by directly being welded with high splitting ratio 1 × 2 fiber coupler axes alignment at the two ends with major diameter toroidal cores optical fiber, then carrying out fused biconical taper to realize at solder joint place with the connection of fiber coupler.
Described have major diameter toroidal cores optical fiber and the connection of fiber coupler be by by have major diameter toroidal cores optical fiber incidence end disc waveguide place certain a bit aim at high splitting ratio 1 × 2 fiber coupler fiber core and weld, have major diameter toroidal cores fiber exit end then splitting ratio 1 × 2 fiber coupler optical fiber axle center high with another collimation connect and weld, then carry out fused biconical taper to realize at solder joint place.
The described major diameter toroidal cores Fibre Optical Sensor part that has increases plating one deck sensitive membrane.The sensitivity of raising system.
The toroidal cores Fibre Optical Sensor segment core distance external world is very near, has strong evanscent field, can record the change of the environment such as environmental liquids or gas refracting index by measuring ring-down time.This sensor adverse effect brought that light source fluctuation can be risen and fallen is reduced to minimum, and measurement mechanism structure is simple, light, highly sensitive, and antijamming capability is strong, and in solution or gas concentration, the sensing aspects such as temperature all will be widely used.
Compared with prior art, advantage of the present invention is:
1, utilize toroidal cores fiber core surface as sensing probe part, the energy appeared due to its evanscent field evenly, sensing area is larger, makes the sensitivity of sensor higher;
2, utilize fiber annular cavity attenuation and vibration technique to make to measure acquisition data more convenient, utilize two coupling mechanisms just can realize, price is more cheap, and cost performance is high;
3, major diameter toroidal cores optical fiber is when fibre core is exposed to the external world, it is sensitive to the multiple change such as ambient temperature, bending, pressure, refractive index, chemistry is done or physical modification is also more convenient on its surface, make this toroidal cores Fibre Optical Sensor based on ring cavity decline can change various, have wider range of application.
Accompanying drawing explanation
Fig. 1 is the toroidal cores optical fibre sensor structure figure based on ring cavity decline;
Fig. 2 (a) is the cross sectional representation of annular surface core fibre; Fig. 2 (b) is toroidal cores external diameter toroidal cores cross section of optic fibre schematic diagram when being less than 125 microns;
Fig. 3 is annular surface core fibre and single-mode fiber end face axes alignment welding schematic diagram;
Fig. 4 is that annular surface core fibre and single mode fiber core aim at welding post-tensioning cone schematic diagram;
Fig. 5 is toroidal cores external diameter toroidal cores fiber optical corrosive program schematic diagram when being less than 125 microns;
Fig. 6 be when utilizing toroidal cores external diameter to be less than 125 microns toroidal cores optical fiber be used as sensing unit and with Single-Mode Fiber Coupling schematic diagram;
Fig. 7 increases plating one deck sensitive membrane structural representation outside annular surface core fibre fibre core.
Embodiment
Basic scheme of the present invention is: the toroidal cores Fibre Optical Sensor based on ring cavity fading effect is that one end 2-2,3-2 that 1 × 2 fiber coupler 2,3 splitting ratio that has high splitting ratio respectively with two by one section of two ends 1-1 with 1-2 with major diameter toroidal cores optical fiber 1 is high is connected, two 1 × 2 fiber couplers have side 2-3 and the 3-3 mutual connection of 1 port, and then formation ring cavity, one end 2-1 with 3-1 that light-pulse generator 4 and detector 5 are low with the splitting ratio of two 1 × 2 fiber couplers is respectively connected and forms.The splitting ratio of high splitting ratio 1 × 2 fiber coupler is at least higher than 99:1.The optical fiber with major diameter toroidal cores is a kind of fibre diameter is 125 microns, fiber core shape is annular, fibre core 6 wall thickness is 4-8 micron, the external diameter of toroidal cores 6 is the special optical fiber of 80-125 micron, its length for transducing part is 2-5 centimetre, and the annular core waveguide 6 of transducing part is less than 1 micron apart from outside air distance.If toroidal cores 6 external diameter is the optical fiber of 80-123 micron, the method of chemical etching can be waited to carry out the covering 7 of thinning optical fiber by HF acid, core waveguide 6 is made to be less than 1 micron apart from outside air distance, be exposed to the external world as much as possible, increase the evanscent field of optical fiber as far as possible, and then improve the sensitivity of system.Decline based on annular and swing the toroidal cores Fibre Optical Sensor in chamber, its principle of work is when narrow-pulse laser light source 4 injects from 2-1 end, and pulse width is less than the time that light moved needed for one week in chamber, incident light often has due to the strong evanscent field of toroidal cores optical fiber through the light intensity of its output terminal of toroidal cores optical fiber and decays, light intensity will exponentially decline in time, and then can die-away time of measuring system, die-away time can change due to the material change around sensing probe, and then draws change to be measured accordingly.
Below in conjunction with accompanying drawing citing, the present invention is described in more detail:
Embodiment 1:
Composition graphs 1-Fig. 4, a kind of surperficial toroidal cores Fibre Optical Sensor sensing unit based on fiber annular cavity-type BPM to be toroidal cores 6 external diameter of a segment length 3 centimetres be annular surface core fibre 1 of 125 microns, its two ends 1-1 with 1-2 to be 1 × 2 fiber coupler 2,3 splitting ratio of 99.0:1.0 respectively with two splitting ratios be 99.0 one end 2-2,3-2 be connected, two 1 × 2 fiber couplers have side 2-3 and the 3-3 mutual connection of 1 port, thus form ring cavity.One end 2-1 with 3-1 that light-pulse generator 4 and detector 5 are 1.0 with the splitting ratio of two 1 × 2 fiber couplers is respectively connected.Wherein toroidal cores optical fiber 1 and the connection of fiber coupler 2 and 3 are by directly being welded (Fig. 3) with coupling mechanism optical fiber 3-2 and 2-2 axes alignment by two ends 1-1 and 1-2 of toroidal cores optical fiber 1, then carry out fused biconical taper (Fig. 4) at solder joint place, realize Energy Coupling by conical transition zone 8.When light source 4 is injected by one end, the other end is detected by photodetector 5 and oscillograph and shows exiting light beam intensity over time, and then measure its die-away time, if sensing unit is placed in saline solution, when the concentration change of saline solution, liquid refractivity just can change, the optical attenuation value that now detector observes will change along with the change of sensing unit ambient refractive index with the die-away time measured, according to refractive index and the concentration thereof that just can be easy to the saline solution obtaining unknown concentration die-away time measured.
Embodiment 2:
Composition graphs 1, Fig. 5 and Fig. 6, a kind of toroidal cores Fibre Optical Sensor sensing unit based on fiber annular cavity-type BPM to be one section of toroidal cores 6 external diameter be toroidal cores optical fiber 1 of 100 microns, its two ends 1-1 with 1-2 to be 1 × 2 fiber coupler 2,3 splitting ratio of 99.0:1.0 respectively with two splitting ratios be 99.0 one end 2-2,3-2 be connected, two 1 × 2 fiber couplers have side 2-3 and the 3-3 mutual connection of 1 output port, thus form ring cavity.One end 2-1 with 3-1 that light-pulse generator 4 and detector 5 are 1.0 with the splitting ratio of two 1 × 2 fiber couplers is respectively connected.Wherein the exit end 1-2 of toroidal cores optical fiber 1 holds with the optical fiber 2-2 of coupling mechanism 2 is directly welded by axes alignment, then carries out fused biconical taper at solder joint place, utilizes conical transition zone 8 to realize Energy Coupling; And the optical fiber 3-2 of the incidence end 1-1 of toroidal cores optical fiber 1 and coupling mechanism 3 hold be utilize by fibre core alignment ring core fiber annular waveguide place of optical fiber 3-2 certain 1: 10, then carry out welding (Fig. 6) of realizing Energy Coupling.External diameter is that the toroidal cores optical fiber 1 of 100 microns utilizes hydrofluorite that its surrounding layer 7 is eroded to 100 microns, and corrosion length is 2 centimetres.When light source 4 is injected by one end, the other end is detected by photodetector 5 and oscillograph and shows exiting light beam intensity over time, and then measure its die-away time, if sensing unit is placed in air chamber, when gas concentration changes, gas refracting index also can change, and the optical attenuation value that now detector observes will change along with the change of sensing unit ambient gas concentration with the die-away time measured, and the die-away time according to measuring just can be easy to the gas concentration obtaining unknown concentration.
Embodiment 3:
Composition graphs 1 and Fig. 7, plant the toroidal cores Fibre Optical Sensor based on fiber annular cavity-type BPM, as different from Example 1, increases the sensitivity of sensor at the top layer of the transducing part of the annular surface core plating metal film of thin layer or deielectric-coating 9.
Claims (7)
1. the toroidal cores Fibre Optical Sensor based on ring cavity decline, it is characterized in that: one end that one section of two ends with major diameter toroidal cores optical fiber have high splitting ratio respectively 1 × 2 fiber coupler splitting ratio with two is high is connected, two 1 × 2 fiber couplers have the side mutual connection of 1 port, and then formation ring cavity, one end that light-pulse generator and detector are low with the splitting ratio of two 1 × 2 fiber couplers is respectively connected;
The described optical fiber with major diameter toroidal cores is fibre diameter is 125 microns, and fiber core shape is annular, and fibre core wall thickness is 4-8 micron, and the external diameter of toroidal cores is the optical fiber of 80-123 micron, its fiber core refractive index n
corebe greater than cladding index n
clad; Carried out the covering of thinning optical fiber by the method for chemical etching, make fibre core be exposed to the external world.
2. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, is characterized in that: described to have major diameter toroidal cores optical fiber for the length of transducing part be 2-5 centimetre.
3. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, is characterized in that: described have major diameter toroidal cores optical fiber and be less than 1 micron for the annular core waveguide distance outside air distance of transducing part.
4. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, is characterized in that: the splitting ratio of described high splitting ratio 1 × 2 fiber coupler is higher than 99:1.
5. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, it is characterized in that: having major diameter toroidal cores optical fiber with the connection of fiber coupler is by directly being welded with high splitting ratio 1 × 2 fiber coupler axes alignment at the two ends with major diameter toroidal cores optical fiber, then carrying out fused biconical taper to realize at solder joint place.
6. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, it is characterized in that: have major diameter toroidal cores optical fiber and the connection of fiber coupler be by by have major diameter toroidal cores optical fiber incidence end disc waveguide place certain a bit aim at high splitting ratio 1 × 2 fiber coupler fiber core and weld, have major diameter toroidal cores fiber exit end then splitting ratio 1 × 2 fiber coupler optical fiber axle center high with another collimation connect and weld, then carry out fused biconical taper to realize at solder joint place.
7. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, is characterized in that: the described major diameter toroidal cores Fibre Optical Sensor part that has increases plating one deck sensitive membrane.
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| CN104807765B (en) * | 2015-05-04 | 2018-01-23 | 华北电力大学 | The Gas in Oil of Transformer detection means of high sensitivity spectral absorption damped oscillation chamber |
| CN106950194B (en) * | 2017-03-17 | 2018-06-12 | 哈尔滨翰奥科技有限公司 | Gas sensor and the method for detecting concentration of SO 2 gas variation |
| CN109115252A (en) * | 2018-09-21 | 2019-01-01 | 太原理工大学 | A kind of Grating examinations device based on fiber annular cavity-type BPM |
| CN109655431A (en) * | 2018-12-12 | 2019-04-19 | 桂林电子科技大学 | Toroidal cores optical fiber SPR sensor |
| CN111025476A (en) * | 2019-11-20 | 2020-04-17 | 桂林电子科技大学 | Single-mode fiber and multi-annular-core hollow fiber coupler and preparation method thereof |
| CN110824728A (en) * | 2019-11-26 | 2020-02-21 | 哈尔滨工程大学 | Double solid core optical fiber photo-thermal phase modulator coated with thermosensitive material |
| CN113324947A (en) * | 2021-05-26 | 2021-08-31 | 南方电网科学研究院有限责任公司 | Gas on-line detection system and method for gas insulated equipment based on evanescent wave method |
| CN114777823B (en) * | 2022-05-24 | 2024-01-05 | 华中科技大学 | FLRD sensor system and FLRD sensing device based on phase drift |
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