CN103364370A - Annular core optical fiber sensor based on annular chamber decline - Google Patents

Annular core optical fiber sensor based on annular chamber decline Download PDF

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Publication number
CN103364370A
CN103364370A CN2013102773334A CN201310277333A CN103364370A CN 103364370 A CN103364370 A CN 103364370A CN 2013102773334 A CN2013102773334 A CN 2013102773334A CN 201310277333 A CN201310277333 A CN 201310277333A CN 103364370 A CN103364370 A CN 103364370A
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optical fiber
toroidal cores
fiber
fibre
major diameter
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CN103364370B (en
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关春颖
钟幸
李树强
刘志海
苑立波
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Harbin Engineering University
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Harbin Engineering University
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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

Toroidal cores Fibre Optical Sensor based on the ring cavity decline
Technical field
What the present invention relates to is a kind of Fibre Optical Sensor, particularly a kind of toroidal cores Fibre Optical Sensor that is 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 of late 1980s rise, have the impact of the light intensity of not being subjected to fluctuation and respond the characteristics such as rapid, thereby have potentiality at optical pressure sensor and the sensor-based system of making a new generation.But the CRD technology has very high requirement for the collimation property that keeps light path to the reflectivity of catoptron and the precision of position adjustment, thereby is 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 Stewart at first, and et al. put forward in calendar year 2001, is used at first the measurement of gas concentration.It utilizes optical fiber and coupling mechanism to consist of equivalent light reflection mirror, and the laser of transmission is limited in the optical fiber, surveys external action to the impact of loss by measuring light intensity attenuation to the time of threshold values.Because the physical quantity surveyed of FLRD sensing technology is the time, without any need for optical amplifier apparatus, can not introduce the ASE noise, thus have highly sensitive, reaction velocity is fast, accuracy is high, light source power is low, to advantages such as the light source power stability requirement are low.Also can realize such as multiple sensings such as pressure, temperature, tension force, refractive index, chemical compositions having larger dirigibility in application by the sensing head of assembling different structure.These characteristics of FLRD become possibility so that make the Fibre Optical Sensor of a new generation.
Summary of the invention
The object of the present invention is to provide a kind of simple in structure, 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 section two ends with major diameter toroidal cores optical fiber link to each other with the high end of two 1 * 2 fiber coupler splitting ratios with high splitting ratio respectively, the side that two 1 * 2 fiber couplers have 1 port is interconnected each other, and then the formation ring cavity, light-pulse generator and detector link to each other with the low end of the splitting ratio of two 1 * 2 fiber couplers respectively.
Described optical fiber with major diameter toroidal cores is that fibre diameter is 125 microns, and fiber core is shaped as annular, and the fibre core wall thickness is the 4-8 micron, and the external diameter of toroidal cores is the optical fiber of 80-125 micron, its fiber core refractive index n CoreGreater than cladding index n Clad
It is described that to have the length that major diameter toroidal cores optical fiber is used for transducing part be 2-5 centimetre.
Described have annular fibre core waveguide distance outside air distance that major diameter toroidal cores optical fiber is used for transducing part less than 1 micron.
Described to have major diameter toroidal cores optical fiber be that external diameter is the optical fiber of 80-123 micron, comes the covering of attenuate optical fiber by the method for chemical etching, makes fibre core be exposed to the external world.
The splitting ratio of described high splitting ratio 1 * 2 fiber coupler is higher than 99:1.
Described to have major diameter toroidal cores optical fiber be directly to weld by two ends and high splitting ratio 1 * 2 fiber coupler axes alignment that will have major diameter toroidal cores optical fiber with being connected of fiber coupler, then carries out fused biconical taper at the solder joint place and realize.
Described have major diameter toroidal cores optical fiber and being connected of fiber coupler be by will having major diameter toroidal cores optical fiber waveguide place of incident end ring shape certain a bit aim at welding with high splitting ratio 1 * 2 a fiber coupler fiber core, have major diameter toroidal cores optical fiber exit end and then connect welding with another high splitting ratio 1 * 2 fiber coupler optical fiber axle center collimation, then carry out fused biconical taper at the solder joint place and realize.
Described have major diameter toroidal cores Fibre Optical Sensor and partly increase plating one deck sensitive membrane.The sensitivity of raising system.
Toroidal cores Fibre Optical Sensor part fibre core spacing from the external world very close to, strong evanscent field is arranged, can record the environmental evolutions such as extraneous liquid or gas refracting index by measuring ring-down time.The adverse effect that this sensor can bring the light source fluctuation fluctuating is reduced to minimum, and measurement mechanism is simple in structure, and is 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 the sensing probe part, because the energy that its evanscent field appears is more even, the sensing area is larger, so that the sensitivity of sensor is higher;
2, utilize the fiber annular cavity attenuation and vibration technique so that measure that to obtain 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 variations such as ambient temperature, bending, pressure, refractive index, do chemistry on its surface or physical modification is also more convenient, so that this toroidal cores Fibre Optical Sensor based on ring cavity decline can change is various, wider range of application is arranged.
Description of drawings
Fig. 1 is based on the toroidal cores optical fibre sensor structure figure of 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 during 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 annular surface core fibre and single-mode fiber axes alignment welding post-tensioning cone schematic diagram;
Fig. 5 is toroidal cores external diameter toroidal cores fiber optical corrosive program schematic diagram during less than 125 microns;
Fig. 6 be when utilizing the toroidal cores external diameter less than 125 microns toroidal cores optical fiber as sensing unit and with the Single-Mode Fiber Coupling schematic diagram;
Fig. 7 is that the annular surface core fibre fibre core outside increases plating one deck sensitive membrane structural representation.
Embodiment
Basic scheme of the present invention is: be to be linked to each other with a high end 2-2, the 3-2 of two 1 * 2 fiber coupler 2,3 splitting ratios with high splitting ratio respectively by one section two ends 1-1 with major diameter toroidal cores optical fiber 1 and 1-2 based on the toroidal cores Fibre Optical Sensor of ring cavity fading effect, a side 2-3 and 3-3 that two 1 * 2 fiber couplers have 1 port are interconnected each other, and then the formation ring cavity, light-pulse generator 4 and detector 5 respectively with the low end 2-1 of the splitting ratio of two 1 * 2 fiber couplers formation that links to each other with 3-1.The splitting ratio of high splitting ratio 1 * 2 fiber coupler will be higher than 99:1 at least.Optical fiber with major diameter toroidal cores is that a kind of fibre diameter is 125 microns, fiber core is shaped as annular, fibre core 6 wall thickness are the 4-8 micron, the external diameter of toroidal cores 6 is the special optical fiber of 80-125 micron, its length that is used for transducing part is 2-5 centimetre, the annular fibre core waveguide 6 of transducing part apart from the outside air distance less than 1 micron.If toroidal cores 6 external diameters are the optical fiber of 80-123 micron, can wait the method for chemical etching to come the covering 7 of attenuate optical fiber by HF acid, make fibre core waveguide 6 apart from outside air distance less than 1 micron, be exposed to as much as possible the external world, increase as far as possible the evanscent field of optical fiber, and then improve the sensitivity of system.The toroidal cores Fibre Optical Sensor that declines and swing the chamber based on annular, its principle of work is to inject from the 2-1 end when narrow-pulse laser light source 4, and pulse width is moved in the chamber the required time in a week less than light, the every light intensity through its output terminal of toroidal cores optical fiber of incident light has owing to the strong evanscent field of toroidal cores optical fiber is decayed, light intensity will be index decreased in time, but and then the die-away time of measuring system, can change die-away time owing to the material around the sensing probe changes, and then draw corresponding variation to be measured.
For example the present invention is described in more detail below in conjunction with accompanying drawing:
Embodiment 1:
In conjunction with Fig. 1-Fig. 4, a kind of is 125 microns annular surface core fibre 1 based on decline toroidal cores 6 external diameters that the surperficial toroidal cores Fibre Optical Sensor sensing unit that swings is 3 centimetres of segment lengths of optic fiber ring-shaped cavity, its two ends 1-1 and 1-2 are that 1 * 2 fiber coupler 2,3 splitting ratios of 99.0:1.0 are that 99.0 an end 2-2,3-2 link to each other with two splitting ratios respectively, a side 2-3 and 3-3 that two 1 * 2 fiber couplers have 1 port are interconnected each other, thereby form ring cavity.Light-pulse generator 4 and detector 5 are that an end 2-1 of 1.0 links to each other with 3-1 with the splitting ratio of two 1 * 2 fiber couplers respectively.Wherein toroidal cores optical fiber 1 and fiber coupler 2 and being connected of being connected are by the two ends 1-1 of toroidal cores optical fiber 1 and 1-2 and coupling mechanism optical fiber 3-2 and 2-2 axes alignment are directly welded (Fig. 3), then carry out fused biconical taper (Fig. 4) at the solder joint place, realize Energy Coupling by conical transition zone 8.When light source 4 is injected by an end, the other end is surveyed by photodetector 5 and oscillograph and is shown the outgoing light intensity over time, and then measure its die-away time, if sensing unit is placed saline solution, when the concentration change of saline solution, liquid refractivity just can change, this moment the light decay depreciation that observes of detector and die-away time of measuring will change along with the variation of refractive index around the sensing unit, according to refractive index and the concentration thereof of the saline solution that just can be easy to obtain unknown concentration the die-away time of measuring.
Embodiment 2:
In conjunction with Fig. 1, Fig. 5 and Fig. 6, a kind of is that one section toroidal cores 6 external diameter is 100 microns toroidal cores optical fiber 1 based on the optic fiber ring-shaped cavity toroidal cores Fibre Optical Sensor sensing unit that swings that declines, its two ends 1-1 and 1-2 are that 1 * 2 fiber coupler 2,3 splitting ratios of 99.0:1.0 are that 99.0 an end 2-2,3-2 link to each other with two splitting ratios respectively, a side 2-3 and 3-3 that two 1 * 2 fiber couplers have 1 output port are interconnected each other, thereby form ring cavity.Light-pulse generator 4 and detector 5 are that an end 2-1 of 1.0 links to each other with 3-1 with the splitting ratio of two 1 * 2 fiber couplers respectively.Wherein the optical fiber 2-2 of the exit end 1-2 of toroidal cores optical fiber 1 and coupling mechanism 2 end is directly to weld by axes alignment, then carries out fused biconical taper at the solder joint place, utilizes conical transition zone 8 to realize Energy Coupling; And the optical fiber 3-2 of the incident end 1-1 of toroidal cores optical fiber 1 and coupling mechanism 3 end be utilize with fibre core alignment ring core fiber annular waveguide place of optical fiber 3-2 certain 1: 10, then weld (Fig. 6) of realizing Energy Coupling.External diameter is that 100 microns toroidal cores optical fiber 1 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 an end, the other end is surveyed by photodetector 5 and oscillograph and is shown the outgoing light intensity over time, and then measure its die-away time, if sensing unit is placed air chamber, when gas concentration changes, gas refracting index also can change, and the light decay depreciation that this moment, detector observed will change along with the variation of sensing unit ambient gas concentration with the die-away time that measures, according to the gas concentration that just can be easy to obtain unknown concentration die-away time of measuring.
Embodiment 3:
In conjunction with Fig. 1 and Fig. 7, plant the toroidal cores Fibre Optical Sensor that declines and swing based on optic fiber ring-shaped cavity, as different from Example 1, in the metal film of the top layer plating thin layer of the transducing part of annular surface core or the sensitivity that deielectric-coating 9 increases sensor.

Claims (9)

1. toroidal cores Fibre Optical Sensor based on ring cavity decline, it is characterized in that: one section two ends with major diameter toroidal cores optical fiber link to each other with the high end of two 1 * 2 fiber coupler splitting ratios with high splitting ratio respectively, the side that two 1 * 2 fiber couplers have 1 port is interconnected each other, and then the formation ring cavity, light-pulse generator and detector link to each other with the low end of the splitting ratio of two 1 * 2 fiber couplers respectively.
2. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, it is characterized in that: described optical fiber with major diameter toroidal cores is that fibre diameter is 125 microns, fiber core is shaped as annular, the fibre core wall thickness is the 4-8 micron, the external diameter of toroidal cores is the optical fiber of 80-125 micron, its fiber core refractive index n CoreGreater than cladding index n Clad
3. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1 is characterized in that: described to have the length that major diameter toroidal cores optical fiber is used for transducing part be 2-5 centimetre.
4. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1 is characterized in that: described have annular fibre core waveguide distance outside air distance that major diameter toroidal cores optical fiber is used for transducing part less than 1 micron.
5. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 2, it is characterized in that: described to have major diameter toroidal cores optical fiber be that external diameter is the optical fiber of 80-123 micron, come the covering of attenuate optical fiber by the method for chemical etching, make fibre core be exposed to the external world.
6. the toroidal cores Fibre Optical Sensor based on ring cavity decline according to claim 1, it is characterized in that: the splitting ratio of described high splitting ratio 1 * 2 fiber coupler is higher than 99:1.
7. 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 is directly to weld by two ends and high splitting ratio 1 * 2 fiber coupler axes alignment that will have major diameter toroidal cores optical fiber with being connected of fiber coupler, then carries out fused biconical taper at the solder joint place and realizes.
8. 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 being connected of fiber coupler and be by will having major diameter toroidal cores optical fiber waveguide place of incident end ring shape certain a bit aim at welding with high splitting ratio 1 * 2 a fiber coupler fiber core, have major diameter toroidal cores optical fiber exit end and then connect welding with another high splitting ratio 1 * 2 fiber coupler optical fiber axle center collimation, then carry out fused biconical taper at the solder joint place and realize.
9. 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 Fibre Optical Sensor and partly increase plating one deck sensitive membrane.
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Cited By (8)

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CN104807765A (en) * 2015-05-04 2015-07-29 华北电力大学 High-sensitivity spectral absorption damped oscillation cavity gas detection device of transformer oil
CN106950194A (en) * 2017-03-17 2017-07-14 哈尔滨翰奥科技有限公司 Gas sensor and the method for detecting concentration of SO 2 gas change
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
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
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
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
CN114777823A (en) * 2022-05-24 2022-07-22 华中科技大学 FLRD sensor system and FLRD sensing device based on phase drift

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CN104807765A (en) * 2015-05-04 2015-07-29 华北电力大学 High-sensitivity spectral absorption damped oscillation cavity gas detection device of transformer oil
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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
CN114777823A (en) * 2022-05-24 2022-07-22 华中科技大学 FLRD sensor system and FLRD sensing device based on phase drift
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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