CN201392311Y - Reflective Optical Fiber Biochemical Sensor Based on Long Period Fiber Bragg Grating - Google Patents

Abstract

The utility model relates to a reflection-type optical fiber biochemistry sensor based on long period optical fiber grating. The reflection-type optical fiber biochemistry sensor comprises a grating section photosensitive optical fiber and a reflection section photosensitive optical fiber which have the same specification and are welded together, wherein the core of the grating section photosensitive optical fiber is written with a long period optical fiber grating, the center of one connected end of the reflection photosensitive optical fiber with the grating section photosensitive optical fiber is corroded by hydrofluoric acid solution to form a conical scattering pit which inwards concave, the diameter of the bottom surface of the scattering pit is equal to the diameter of the core of the reflection section photosensitive optical fiber, and the other end surface of the reflection photosensitive optical fiber is plated with a metal reflecting film. As the spread of mode conduction in the fiber core is eliminated through scattering, the optical fiber can not generate interference with modes spreading in a cladding, and the spectrum peak value reflected back by the end surface metal film is single. The reflection-type optical fiber biochemistry sensor has simple structure, convenient measurement and low cost.

Description

Reflection-type optical fiber biochemical sensor based on long period fiber grating

Technical field

The utility model belongs to technical field of optical fiber sensing, relates to a kind of reflection-type optical fiber biochemical sensor based on long period fiber grating.

Background technology

Optical fiber sensing technology is an emerging technology that forms on fiber optics and Fibre Optical Communication Technology development foundation, is to utilize optical fiber or the optical-fiber type device characteristic of some physical quantity sensitivity to external world, converts thereof into the technology of the signal that can measure.Fiber grating is a kind of optical-fiber type device that has periodic modulation in fiber core along longitudinal refractive index.It can be used as a kind of wavelength-modulated type optical sensor.It has inherited not only that all anti-electromagnetic interference (EMI) of Fibre Optical Sensor, high sensitivity, response speed are fast, wide dynamic range, in light weight, compact conformation, use flexibly, be applicable to advantages such as corrosivity or risk environment, also have Wavelength-encoding simultaneously, be convenient to advantage such as multiplexing formation optical fiber sensing network.For potential demands such as biochemical sensor or biochemical probes, attracted very big application future especially based on the refractive index sensing of fiber grating.

Fiber grating is to utilize the photosensitivity of fiber optic materials and the one dimension periodic structure that forms in fiber core, and its principle of work is to satisfy resonance coupling between the wavelength place emergence pattern of phase-matching condition.When physical quantitys such as the strain of fiber grating environment of living in, temperature change, if this variation can cause the cycle of grating or effective refractive index and also change, thereby make the resonant wavelength of grating change, just can obtain the situation of change of measured physical quantity by measuring the variation of resonant wavelength.According to the difference of fiber grating cycle length, be divided into bragg grating (FBG) and long period fiber grating (LPG) two big classes.

The Bragg wavelength X of bragg grating _BDetermine by following formula:

λ _B＝2nA

In the formula, n is the effective refractive index of fibre core, and Λ is the cycle of grating.The cycle that is operated in the FBG of optical fiber communication wave band generally is the hundreds of nanometer, and it is the reverse coupled to the basic mode that is transmitted in fibre core.Therefore can be used as stress, the reflection sensor of temperature etc.But traditional FBG is insensitive for the environment refractive index, can not be used to make biochemical sensor or bioprobe.Someone proposes to remove the covering of optical fiber by processing such as corrosion or polishings, thereby makes the fibre core guided mode can experience the change of refractive of external environment.But the physical strength of having removed the fiber core (about general single mode fiber core diameter 8 μ m) of covering reduces greatly, is difficult to obtain in practice application.

The resonance wavelength of long period fiber grating _jCan provide by following formula:

${\mathrm{\λ}}_j=(n_{\mathrm{eff}}^{\mathrm{co}}-n_{\mathrm{eff},j}^{\mathrm{cl}})\mathrm{\Λ}$

Wherein, n _Eff ^CoBe the effective refractive index of fibre core guided mode, n _{Eff, j} ^ClBe the effective refractive index of j rank claddingmode, Λ is the cycle of long period fiber grating.LPG is coupled to cladding mode to the basic mode of transmission in the same way.The effective refractive index n of cladding mode _{Eff, j} ^ClBe subjected to the influence of the extraneous refractive index of optical fiber, along with the environment change of refractive, the resonance wavelength of LPG can produce corresponding drift.Therefore LPG not only has the temperature higher than FBG, and sensitivitys such as stress more have its distinctive susceptibility to the environment refractive index.

In order to improve the performance of fiber-optic grating sensor, people have proposed various sensor construction based on long period fiber grating.Common long period fiber grating sensing device structure is to be carved with one of LPG with one to terminate on the light source, the other end connects spectrometer, when external environment parameters changed, observed spectrum also can change on the spectrometer, utilized this to change the variation that detects environment.The interferometer in two identical LPG formation optical fiber of cascade on same optical fiber is also arranged., can not be directly used in and design and produce biochemical probe sensor at transmission mode based on the working sensor of long period fiber grating, be unfavorable for that also the networking of sensor is multiplexing.

Summary of the invention

The purpose of this utility model just provides a kind of novel sensor based on long period fiber grating, this sensor adopts long period fiber grating and fiber end face plating catoptron, utilize its coupled wavelength can detect extraneous change of refractive, use thereby be used for biochemical sensitive.

The utility model comprises the grating section light-sensitive optical fibre and the reflecting segment light-sensitive optical fibre of welding, and grating section light-sensitive optical fibre and reflecting segment light-sensitive optical fibre adopt the light-sensitive optical fibre of same size, and promptly the diameter of fibre core specification identical, covering is identical.Grating section light-sensitive optical fibre fibre core is with long period fiber grating.The center of the end that the reflecting segment light-sensitive optical fibre is connected with grating section light-sensitive optical fibre caves inward into the scattering hole, described scattering hole is for conical, conical scattering hole is coaxial with the reflecting segment light-sensitive optical fibre, and the equal diameters of the diameter of conical bottom surface and reflecting segment light-sensitive optical fibre fibre core.The end face of the reflecting segment light-sensitive optical fibre other end is coated with metallic reflective coating, and the material of metallic reflective coating is a kind of in aluminium, silver or the gold.

Biochemical sensor of the present utility model has adopted long period fiber grating and fiber end face plating mirror structure, fibre core is provided with the scattering hole simultaneously, the propagation of guided mode in the fibre core has been fallen in scattering, thereby can not interfere with the pattern of in covering, propagating, the spectrum peak that the end plane metal film reflects is single.There is the same reflection peak of spectral characteristic of the loss peak of and traditional long period fiber grating in this biochemical sensor, so is operated in reflective-mode, and variations in refractive index has higher sensitivity to external world.That this sensor has is simple in structure, compact, measure convenient and low cost and other advantages.

Description of drawings

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

Embodiment

As shown in Figure 1, comprise the grating section light-sensitive optical fibre 1 and the reflecting segment light-sensitive optical fibre 2 of welding based on the reflection-type optical fiber biochemical sensor of long period fiber grating, grating section light-sensitive optical fibre 1 and reflecting segment light-sensitive optical fibre 2 adopt the light-sensitive optical fibre of same sizes.Grating section light-sensitive optical fibre fibre core 7 is with long period fiber grating 6.The center of the end that reflecting segment light-sensitive optical fibre 2 is connected with grating section light-sensitive optical fibre 1 caves inward into scattering hole 5.Scattering hole 5 is conical, and conical scattering hole 5 is coaxial with reflecting segment light-sensitive optical fibre 2, and the equal diameters of the diameter of conical bottom surface and reflecting segment light-sensitive optical fibre fibre core 4.The end face of reflecting segment light-sensitive optical fibre 2 other ends is coated with metallic reflective coating 3.The material of metallic reflective coating can be aluminium, silver or golden.

The principle of work of this reflection-type optical fiber biochemical sensor is: the light that wideband light source emits enters first port of optical circulator by optical fiber, come out from second port through optical circulator, enter on the optical fiber of long period fiber grating, run into long period fiber grating in communication process after, that part of light that meets the resonant wavelength matching condition is coupled to from fibre core through long period fiber grating and enters covering.Except other light in resonant wavelength zone continues to propagate along fiber core, and run into optical fiber fibre core the scattering hole and be scattered.The light that is coupled to claddingmode is propagated in fibre cladding, and the influence that is subjected to scattering hole seldom after reflecting through optical fiber connector end plane metal reflectance coating again, is coupled into fiber core again during once more through long period fiber grating and propagates.Because the fibre core at optical fiber is provided with the scattering hole, other is not coupled out the light wave of covering, will through the scattering hole time, be scattered, thereby can the reflected light detector, that part of light in the resonant wavelength zone that the coupled back into optical fibers fibre core is propagated reenters second port of optical circulator along optical fiber, come out from the 3rd port through behind the optical circulator, enter into spectroanalysis instrument by the optical fiber connection.Formula by the resonant wavelength of long period fiber grating ${\mathrm{\λ}}_j=(n_{\mathrm{eff}}^{\mathrm{co}}-n_{\mathrm{eff},j}^{\mathrm{cl}})\mathrm{\Λ}$ As can be known, when the extraneous coenocorrelation that acts on grating changes and causes that refractive index around the grating changes, can cause the change of fiber core and cladding mode effective refractive index difference, finally can cause the variation of coupled wavelength.By detecting the long drift of coupled wave of grating, need just can obtain the coenocorrelation dynamic-change information of detection.

Claims (1)

1. Reflective optical fiber biochemical sensor based on long-period fiber grating, including fused grating section photosensitive optical fiber and reflection section photosensitive optical fiber. The fiber core is written with a long-period fiber grating; the center of one end of the photosensitive fiber in the reflection section and the photosensitive fiber in the grating section is sunken inward to form a scattering pit, and the scattering pit is conical, and the conical scattering pit is the same as the photosensitive fiber in the reflection section. axis, and the diameter of the conical bottom surface is equal to the diameter of the core of the photosensitive optical fiber in the reflective section; the other end of the photosensitive optical fiber in the reflective section is coated with a metal reflective film, and the material of the metal reflective film is one of aluminum, silver or gold.

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