CN201575791U - Small capacity optical fiber mode interferometer sensor - Google Patents

Abstract

The utility model relates to a small capacity optical fiber mode interferometer sensor, which aims to overcome the defects of the conventional optical fiber mode interferometer, such as complicate manufacture techniques, special raw materials, lower mechanical strength, etc. The interferometer sensor comprises standard single mode fibers, a small capacity single mode fiber, reflecting film, a broadband light source, an optical spectrum analyzer and a circulator, wherein the broadband light source is optically connected with a port I of the circulator through a first standard single mode fiber, the optical spectrum analyzer is optically connected with a port III of the circulator through a second standard single mode fiber, one end of the small capacity single mode fiber is optically connected with a port II of the circulator through a third standard single mode fiber, the reflecting film with the thickness of d is arranged at the other end of the small capacity single mode fiber, d ranges from 100 Mum to 200 Mum, and the connected standard single mode fibers and the small capacity single mode fiber are coaxially arranged. The sensor provided by the utility model has the advantages of simple manufacture process and low cost.

Description

A kind of thin core optical fiber mode interferometer sensor

Technical field

The utility model belongs to technical field of optical fiber sensing, be specifically related to a kind of thin core optical fiber mode interferometer sensor, can be used to detect multiple material and characteristics such as antibody-antigen, chemical agent concentration, sewage PH in fields such as biomedicine, chemical detection, environmental monitorings.

Background technology

Fibre Optical Sensor is a kind of novel sensor.Compare with traditional sensor, it is little that it has a volume, light weight, and anti-electromagnetic interference (EMI), highly sensitive, the sensor of advantage, particularly full fiber type such as corrosion-resistant is convenient to and fibre-optic transmission system (FOTS) is formed telemetry network, works under abominable, dangerous environment.According in the Fibre Optical Sensor whether based on optical grating construction, Fibre Optical Sensor can be divided into fiber-optic grating sensor and non-grating type Fibre Optical Sensor.

Fiber-optic grating sensor is to have become widely used sensor, and it is divided into two kinds, and a kind of (Fiber Bragg Grating FBG), is a kind of sensor of reflection-type of arrowband based on the optical fiber Bragg fiber grating; It is another kind of that (Long-Period Fiber Grating LPG), is a kind of band resistance sensor of transmission-type based on long period fiber grating.These two kinds of sensors can apply to stress, and bending waits the field, also have higher signal to noise ratio (S/N ratio) simultaneously.But its temperature stability is lower, therefore has temperature disturbance, particularly long-period fiber grating sensor, and more responsive to temperature, its temperature-responsive is approximately 0.1～0.3nm/ ℃, and this greatly reduces the stability and the sensitivity of sensor.In addition, the ordinary optic fibre grating just begins annealing under greater than 300 ℃ environment, therefore be unfavorable for working under hot environment.

And the optical fiber interferometer sensor of non-grating type, because its simple manufacture craft, cheap cost and higher temperature stability have attracted more and more scholars, become the focus of current academia research.This class sensor design thought is optical-fiber type mode interferometer of structure, excite the high-order cladding mode of transmission light thus, and make and have stable optical path difference and interfering at last between high-order cladding mode and the core, thereby form the interferometer sensor of sensitivity to be measured to external world.But shortcomings such as all there is complex manufacturing technology in existing optical-fiber type mode interferometer, and starting material are special, and physical strength is lower.

Summary of the invention

The purpose of this utility model is at the deficiencies in the prior art, has proposed a kind of thin core optical fiber mode interferometer sensor of making simple, high mechanical properties, low temperature susceptibility.This sensor utilizes the thin-core fibers at fused fiber splice place to excite higher order mode, and as mode coupler, thereby form the interferometer sensor of test substance sensitivity to external world.

The utility model comprises standard single-mode fiber, thin core single-mode fiber, reflectance coating, wideband light source, spectroanalysis instrument and circulator; Wideband light source is connected with the I mouth light of circulator by standard single-mode fiber, spectroanalysis instrument is connected with the III mouth light of circulator by standard single-mode fiber, one end of thin core single-mode fiber is connected with the II mouth light of circulator by standard single-mode fiber, the other end of thin core single-mode fiber is provided with the reflectance coating that thickness is d, wherein 100 μ m≤d≤200 μ m.

Standard single-mode fiber that is connected with the II mouth light of circulator and the thin coaxial setting of core single-mode fiber.

The utility model thin core optical fiber mode interferometer sensor principle of work is: light is single mode transport in single-mode fiber, only has the basic mode of sandwich layer transmission.After light imports thin-core fibers into, because fibre core varies in size, cause light single mode transport again, the high-order cladding mode is excited.Because effective refractive index was different when different high-order cladding modes transmitted in optical fiber, therefore, the light of different mode is after the reflection of thin-core fibers end face reflection film, when arriving single-mode fiber, interfere with the basic mode of sandwich layer transmission, thereby form local constructive interference and destructive interference.Destructive interference condition to certain concrete transmission paddy can be expressed as:

$2\mathrm{\π}[n_{\mathrm{eff}}^{\mathrm{co}}\left(\mathrm{\λ}\right)-n_{\mathrm{eff}}^{\mathrm{cl},j}(\mathrm{\λ},n_{\mathrm{ext}})]\frac{L}{{\mathrm{\λ}}_D}=(2k+1)\mathrm{\π}---\left(1\right)$

Wherein, λ _DBe the destructive interference wavelength, n _Eff ^CoBe the effective refractive index of sandwich layer, n _Eff ^{Cl, j}Be the effective refractive index of j rank cladding mode, n _ExtBe the refractive index of external substance, L is the length of thin-core fibers, and k is an integer.

The interference pattern of thin core optical fiber mode interferometer sensor has reacted sensing characteristics.Because length that thin-core fibers is depended in local constructive interference that forms and destructive interference and the higher order mode that inspires, when extraneous refraction index changing, the characteristic of higher order mode will change thereupon, thereby influence the interference pattern of sensor.This sensor response of refractive index to external world can be expressed as:

$\frac{d{\mathrm{\λ}}_D}{d{n}_{\mathrm{ext}}}=\frac{-{\mathrm{\λ}}_D}{\mathrm{\Δ}{n}_{\mathrm{eff}}}\frac{\∂n_{\mathrm{eff}}^{\mathrm{cl},j}}{\∂n_{\mathrm{ext}}}/[1-\frac{{\mathrm{\λ}}_D}{\mathrm{\Δ}{n}_{\mathrm{eff}}}(\frac{\∂n_{\mathrm{eff}}^{\mathrm{co}}}{\∂\mathrm{\λ}}-\frac{\∂n_{\mathrm{eff}}^{\mathrm{cl},j}}{\∂\mathrm{\λ}})]---\left(2\right)$

Wherein, Δ n _EffThe effective refractive index that is sandwich layer pattern and basic mode is poor.As sensor, temperature stability is an important parameter, and the temperature of the thin core optical fiber mode interferometer that the utility model proposes should be expressed as:

$\frac{d{\mathrm{\λ}}_D}{\mathrm{dT}}\≅[\frac{{\mathrm{\λ}}_D}{\mathrm{\Δ}{n}_{\mathrm{eff}}}(\frac{\∂\mathrm{\Δ}{n}_{\mathrm{eff}}}{\∂n_{\mathrm{co}}}\frac{d{n}_{\mathrm{co}}}{\mathrm{dT}}+\frac{\∂\mathrm{\Δ}{n}_{\mathrm{eff}}}{\∂n_{\mathrm{cl}}}\frac{{\mathrm{dn}}_{\mathrm{cl}}}{\mathrm{dT}})+\frac{{\mathrm{\λ}}_D}{L}\frac{\mathrm{dL}}{\mathrm{dT}}]/(1-\frac{{\mathrm{\λ}}_D}{\mathrm{\Δ}{n}_{\mathrm{eff}}}\frac{\∂n_{\mathrm{eff}}}{\∂\mathrm{\λ}}).---\left(3\right)$

Sensor production technology of the present utility model is simple, need comprise that unlike fiber-optic grating sensor a whole set of grating of laser instrument is inscribed system, only needs the single-mode fiber of a unjacketed optical fiber welder and two kinds of different core diameters.In view of the utlity model has very high refractive index susceptibility and temperature stability, therefore can on this sensor, plate bio-sensitive film, materials such as pH sensitive high molecular weight film detect specific biomolecule or pH value of water solution etc.

Description of drawings

Fig. 1 is a structural representation of the present utility model;

Fig. 2 is the interferogram of the thin core optical fiber mode interferometer sensor of different thin-core fibers length;

Fig. 3 is temperature response characteristics figure of the present utility model;

Fig. 4 is the utility model response characteristic figure of refractive index to external world.

Embodiment

Below in conjunction with accompanying drawing the utility model is further described

As shown in Figure 1, a kind of thin core optical fiber mode interferometer sensor comprises thin core single-mode fiber 5, reflectance coating 6, wideband light source 1, spectroanalysis instrument 2 and circulator 4; Wideband light source 1 is connected with the I mouth light of circulator 6 by the first standard single-mode fiber 3-1, spectroanalysis instrument 5 is connected with the III mouth light of circulator 6 by the second standard single-mode fiber 3-2, thin core single-mode fiber 2 (as, Nufern 460-HP, the about 3 μ m of core diameter, cutoff wavelength 450nm) end by the 3rd standard single-mode fiber 3-3 (as, Corning SMF-28, the about 8 μ m of core diameter) be connected with the II mouth light of circulator 4, the other end is provided with the reflectance coating 3 that thickness is 200 μ m.

The 3rd standard single-mode fiber 3-3 that connects and thin core single-mode fiber 5 coaxial settings adopt fusion techniques to connect between the two, and reflectance coating is formed by the sputter sputter.After the light that wideband light source 1 sends enters the I mouth of circulator 4, by the outgoing of II mouth, after the reflectance coating reflection of thin core single-mode fiber end, enter the II mouth of circulator 4, and by the outgoing of III mouth, spectroanalysis instrument 2 receives and analyzes this interference signal.

Because the length of thin-core fibers will influence interference pattern in this sensor, in the manufacturing process of sensor, insert the thin-core fibers of different length, its interference pattern as shown in Figure 2, wherein, (a) thin core single-mode optical fiber length is that the thin core single-mode optical fiber length of 1cm, (b) is that the thin core single-mode optical fiber length of 2cm, (c) is 3cm.Therefore can design the sensor of special transmission wavelength and bandwidth by the length that changes thin core single-mode fiber.

Temperature response characteristics is a very important index of sensor, is directly connected to the stability of its work.The utility model uses a programmable temperature control furnace to test the temperature stability of the sensor samples that inserts the long thin core single-mode fiber of 1cm.As shown in Figure 3, the position of destructive interference wavelength is along with the rising of temperature is drifted about to the long wave direction, and both present a good linear relationship.Its temperature stability is 9.8pm/ ℃, than FBG and LPG sensor, the utlity model has very good temperature stability.

In order to prove that the utility model can be applied to sensory fields such as biomedicine, chemical detection, environmental monitoring, studied this sensor response characteristic of refractive index to external world for this reason.Utilize this sensor that the sucrose solution of variable concentrations has been carried out refraction index test, mass percent is respectively: (1.381,5.123,8.425,11.817,14.821,18.033,21.136,24.242,26.901,29.577,32.432,35.065); Corresponding refractive index is (1.3346,1.3400,1.3448,1.3500,1.3547,1.3599,1.3651,1.3704,1.3750,1.3798,1.3850,1.3899).The result as shown in Figure 4, the refractive index sensitivity of this sensor is up to 105nm/R.I.U, and has the better linearity relation.

Therefore this thin core optical fiber mode interferometer sensor with high sensitivity and temperature stability has very application prospects at sensory field.

Claims (1)

1. thin core optical fiber mode interferometer sensor, comprise standard single-mode fiber, thin core single-mode fiber, reflectance coating, wideband light source, spectroanalysis instrument and circulator, it is characterized in that: wideband light source is connected with the I mouth light of circulator by standard single-mode fiber, spectroanalysis instrument is connected with the III mouth light of circulator by standard single-mode fiber, thin core single-mode fiber one end is connected with the II mouth light of circulator by standard single-mode fiber, the other end is provided with the reflectance coating that thickness is d, wherein 100 μ m≤d≤200 μ m; Standard single-mode fiber that is connected with the II mouth light of circulator and the thin coaxial setting of core single-mode fiber.

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