CN102809778B - Liquid-encapsulated fiber bragg grating temperature compensation method - Google Patents
Liquid-encapsulated fiber bragg grating temperature compensation method Download PDFInfo
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- CN102809778B CN102809778B CN201210296184.1A CN201210296184A CN102809778B CN 102809778 B CN102809778 B CN 102809778B CN 201210296184 A CN201210296184 A CN 201210296184A CN 102809778 B CN102809778 B CN 102809778B
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Abstract
A liquid-encapsulated fiber bragg grating temperature compensation method comprises the following steps: firstly, preparing a micron-diameter fiber bragg grating, removing silica glass cladding the fiber bragg grating by utilizing the hydrofluoric acid etching process, and partially etching a fiber core which is the only one existing in the grid region of the fiber bragg grating to enable the diameter of the fiber core to reach 4Mum-8Mum; and secondly, enabling a single mode fiber prepared in the first step to penetrate a quartz glass tube and to be straightened without the need of prestress, achieving columnar encapsulation of the processed micron-diameter fiber bragg grating by using the quartz glass tube in which a solution with specific refractive index and temperature coefficient of refractive index is charged, extracting air in the solution, sealing two ends of the quartz glass tube by an adhesive, using the solution as the cladding of the fiber bragg grating, and compensating the characteristic that the reflection wavelength of the fiber bragg grating is subject to redshift long with the temperature rise. The liquid-encapsulated fiber bragg grating temperature compensation method has the characteristics of simplicity, convenience in operation and function of reducing the temperature sensitivity of the fiber bragg grating.
Description
Technical field
The invention belongs to optical fiber communication and optical fiber sense technical field, be specifically related to a kind of liquid-packing optical fiber grating temperature compensation method, adopt the technology that reduces the long temperature sensitivity of Fiber Bragg Grating FBG (FBG) cardiac wave, by the ordinary optic fibre Bragg grating corroding, encapsulate with quartz glass tube, and in pipe, fill specific refractive index solution, to realize the temperature stability of fiber grating bragg wavelength, relate to the test device system of this kind of device simultaneously.
Background technology
Fiber Bragg Grating FBG is a kind of photosensitivity of utilizing silica fibre material, incident light coherent field pattern is write fibre core by method by ultraviolet photoetching, in fibre core, produce periodic index of refraction variation vertically, thereby form a fibre-optic waveguide device with narrow-band filtering function.In the time of broadband light process fiber grating, the wavelength that meets Bragg condition will reflect, and the light of its commplementary wave length will continue transmission through fiber grating.Utilize this characteristic can form the optoelectronic device of many unique properties, as the measurement of the strain of the wavelength division multiplexer in narrow band filter, reverberator, dispersion compensator, Er-doped fiber gain amplifier and noise filter, dwdm system, large scale structure and the quasi-distributed measurement of temperature, oil (gas) down-hole pressure and flow, space shuttle monitoring running state, bridge deformation are measured the Fibre Optical Sensor etc. of application.Fiber grating owing to thering is microminiaturization, coupling is good, wavelength selectivity is good, it is insensitive to polarize and be easy to and the characteristic such as fibre system is connected, and becomes the Key Passive Components of optical fiber telecommunications system and optical fiber sensing system.
In optical fiber grating sensing application, be mainly to have utilized the tunability of its reflection wavelength to temperature and strain.But along with this functional fibre-optic waveguide device function exploitation and application, need in many instances the high stability of fiber grating reflection wavelength to temperature, just need to carry out temperature to fiber grating and subtract quick or compensation deals, calibrate as the wavelength of selecting reference optical fiber optical grating reflection in Demodulation of Fiber Grating Sensor, must require to there is good temperature-insensitive with reference to the reflection wavelength of grating.In optical fiber telecommunications system, grating fibers is mainly used to serve as wavelength selector part, its stability to operating ambient temperature is to weigh the important indicator of device performance, particularly carrying out based on fiber grating in the narrow cable and wide optical fiber laser of wavelength selection, realize stable single-frequency laser output, the fiber grating that serves as exocoel end mirror just must have good temperature-insensitive characteristic.But bare fibre Bragg grating has certain susceptibility to temperature, its reflection wavelength is 0.013nm/ ℃ to the response sensitivity of temperature, and this has just affected the temperature stability of Fiber Bragg Grating FBG reflection wavelength.Addressing the above problem conventional method is with the material with negative expansion coefficient, fiber grating to be encapsulated, utilize material negative expansion produce negative strain compensated optical fiber grating thermal expansion effects in normal strain, and require solidifying of material in encapsulation process can not make fiber grating produce chirp phenomenon, therefore the encapsulation technology of fiber grating is had to high requirement.
So, propose a kind of effective, easy fiber bragg grating temperature and subtract quick method, reduce the response sensitivity of Fiber Bragg Grating FBG wavelength to temperature and the technical difficulty of optical fiber grating temperature compensation, be the technical problem underlying that patent of the present invention will solve.
Summary of the invention
In order to overcome above-mentioned the deficiencies in the prior art, the object of the present invention is to provide a kind of liquid-packing optical fiber grating temperature compensation method, solve the technical difficulty that reduces optical fiber grating temperature compensation encapsulation process, there is method simple, easy to operate and reduce the feature of the temperature control of fiber grating.
To achieve these goals, the technical solution used in the present invention is: a kind of liquid-packing optical fiber grating temperature compensation method, comprises the following steps:
One, prepare micron diameter fiber grating, utilize hydrofluorite etching process that the silica glass of cladded-fiber grating is removed, only there is fibre core in the grid region of fiber grating, and fibre core is carried out to partial corrosion, makes the diameter of the fibre core in grid region reach 4～8 μ m;
Two, single-mode fiber prepared by step 1 is through quartz glass tube stretching without Prestressing, finished micron diameter fiber grating is carried out to column encapsulation with quartz glass tube, in quartz glass tube, fill the solution with specific refractive index and thermal refractive index coefficient, take out after the air in solution with vacuum pump, quartz glass tube two ends seal with adhesive, served as the covering of fiber grating by solution, utilize cladding index to increase the characteristic that reduces to cause fiber grating reflection wavelength violet shift with temperature, fiber grating reflection wavelength is increased to red shift Characteristic Compensation of Medical Sensors with temperature.
The refractive index of the solution described in step 2 is 1.4545 ~ 1.4560, and its thermal refractive index coefficient is 0.00026 ~ 0.00045.
Described fiber grating adopts Fiber Bragg Grating FBG.
The optical fiber grating temperature compensation technical method relating in the present invention, be primarily characterized in that the thermo-optic effect based on solution, select the particular solution of thermal refractive index coefficient in 0.00026 ~ 0.00045 scope to replace the covering of fiber grating according to the grid region diameter dimension of fiber grating, realize the temperature-responsive of fiber grating is compensated by the temperature variant characteristic of the thermo-optic effect ie in solution refractive index of solution, not adopt positive thermal strain that traditional negative thermal strain compensates fine grating to reach the object of stablizing output wavelength.
Beneficial effect of the present invention:
The present invention's micron diameter fiber grating used, is characterized in that only there is fibre core in the grid region of fiber grating, and its diameter is first to determine through ad hoc approach, utilizes hydrofluorite etching process that covering is removed.
The packaging technology of fiber grating involved in the present invention, is characterized in that in encapsulation process without fiber grating is applied to prestress, seals after only needing to exclude the air of solution in quartz glass tube again, and therefore technique simple possible, easy to operate.
The employing special solution that the present invention proposes encapsulates the method that realizes temperature compensation to unclad fiber grating, owing to having avoided the impact of encapsulating material strain on fiber grating, therefore implement the impact that is not subject to packaging technology technology, simple possible, easy to operate, and there is repeatability.
Accompanying drawing explanation
Fig. 1 is fiber bragg grating temperature compensation encapsulating structure figure of the present invention.
Fig. 2 is Fiber Bragg Grating FBG reflection wavelength test macro of the present invention.
Fig. 3 is solution cladded-fiber optical grating reflection spectrogram of the present invention.
Fig. 4 is the temperature variant relation curve of Fiber Bragg Grating FBG reflection wavelength after temperature compensation of the present invention.
embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail, but the invention is not restricted to described embodiment below.
embodiment 1
Optical fiber grating temperature compensation method proposed by the invention, its core is that the silica glass covering of fiber grating specific refractive index solution is replaced, and then with the encapsulation of cylindric quartz glass tube, increase the characteristic that reduces to cause fiber grating reflection wavelength violet shift by cladding index with temperature, fiber grating reflection wavelength is increased to red shift Characteristic Compensation of Medical Sensors with temperature.Adopt apparatus structure schematic diagram as shown in Figure 1, by single-mode fiber 1,7, adhesive 2,6, particular solution 3, forms without covering grating 4 and cylindric quartz glass tube 5.
Its manufacturing process method is: the covering hydrofluorite at 4 places, the grid region of ordinary optic fibre grating is eroded, and fibre core is carried out to partial corrosion, the diameter in grid region 4 is reached below 8 μ m; Then single-mode fiber 1,7 is also stretching without Prestressing through quartz glass tube 5, first stick with glue left end the fixing single-mode fiber 1 of agent 2 shutoff quartz glass tubes 5, after tackifier is solid, give in quartz glass tube 5 and fill solution 3 again, and with after the air in vacuum pump extraction solution 3, with right-hand member the fixing single-mode fiber 7 of adhesive 6 shutoff quartz glass tubes 5, after tackifier 6 is solid, temperature compensation has encapsulated again.
embodiment 2
In the present embodiment, relate to the fiber grating after compensation encapsulation is carried out to temperature test experimental system, formed by the part such as fiber grating 12, spectroanalysis instrument 13 after coupling liquid bath 8, adjustable incubator 9, fiber optical circulator 10, wideband light source 11, encapsulation, each several part connects with general single mode fiber, fiber grating after encapsulation 12 left side tail optical fiber terminals immerse coupling liquid baths 8, object be eliminate optical fiber fault plane reflection to improve the signal to noise ratio (S/N ratio) of wavelength signals.The effect of fiber optical circulator 10 is to limit the direction of propagation of light.The light that wideband light source 12 sends is entered by the red end of fiber optical circulator 10, enter fiber grating 12 from blue end output, the light that meets Bragg condition is reflected through fiber optical circulator 10 and enters spectroanalysis instrument 13 from white end, and the light that does not meet Bragg condition enters coupling liquid bath 8 by grating and is absorbed almost no reflection events.
A kind of liquid-packing optical fiber grating temperature compensation method, comprises the following steps:
One, prepare micron diameter fiber grating, utilize hydrofluorite etching process that the silica glass of cladded-fiber grating is removed, only there is fibre core in the grid region of fiber grating, and fibre core is carried out to partial corrosion, makes the diameter of the fibre core in grid region reach 5 μ m;
Two, single-mode fiber prepared by step 1 is through quartz glass tube stretching without Prestressing, finished micron diameter fiber grating is carried out to column encapsulation with quartz glass tube, in quartz glass tube, fill refractive index and be 1.4550 solution, its thermal refractive index coefficient is 0.00038 RIU/ ℃, take out after the air in solution with vacuum pump, quartz glass tube two ends seal with adhesive, served as the covering of fiber grating by solution, utilize cladding index to increase the characteristic that reduces to cause fiber grating reflection wavelength violet shift with temperature, fiber grating reflection wavelength is increased to red shift Characteristic Compensation of Medical Sensors with temperature.
Utilize embodiment 2 shown devices, the fiber grating of encapsulation 4 is placed in to adjustable incubator 9, since 25 ℃ of intensifications, records primary event wavelength every 5 ℃ with spectroanalysis instrument 13, until be warmed to 70 ℃, the fiber grating reflection wavelength drift amount obtaining and temperature relation are as shown in Figure 3.By Tu Ke get, it is this that with quartz glass tube encapsulation, filling solution serves as the fiber grating of covering, the temperature control of its reflection wavelength is 0.0006nm/ ℃, compared with ordinary optic fibre grating, the temperature control of reflection wavelength reduces nearly 22 times, after encapsulation, obtains fiber grating reflection wavelength the stability of temperature has been improved.And in heating and cooling process, fiber grating reflectance spectrum shape is substantially constant, can meet application requirements, specifically as shown in Figure 4, there is no chirp phenomenon.
Therefore, embodiment 3 has confirmed the feasibility of this kind of temperature compensation, the encapsulation of adopting quartz glass pipe has also been described on the other hand, do not make fiber grating that the additional strain causing because of encapsulating material thermal expansion occurs, produce chirp phenomenon, this mainly comes from optical fiber has identical thermal expansivity with quartz glass tube.
According to above-mentioned principle, method and result, also can select the different unclad fiber grating of diameter and the solution encapsulation with different refractivity temperature coefficient to realize the temperature compensation of fiber grating.Described embodiment only in order to illustrate implementer's case of the present invention feasibility and and unrestricted, modify or be equal to replacement based on technical method described in embodiment, and do not depart from the spirit and scope of the present invention, all should be encompassed in claim scope of the present invention.
optical fiber grating temperature compensation principle of the present invention is as follows:
Optical fiber Bragg raster (FBG) is the fibre-optic waveguide that a kind of fiber cores district refractive index is subject to periodic modulation, its guided mode centre wavelength
with fibre core effective refractive index
, the grating cycle
meet relation
relation.Any change of grating cycle and effective refractive index all can cause the change of centre wavelength.
For the fiber grating without covering, in the time that environment temperature changes, the thermo-optic effect of optical fiber and thermal expansion effects can cause that effective refractive index and the variation in grating cycle cause reflection wavelength to change, and meet:
Wherein,
with
represent respectively thermo-optical coeffecient and the thermal expansivity of fiber grating, experimental results show that in the temperature range of grating application and all can regard normal number as.Therefore, ordinary optic fibre optical grating reflection wavelength is Linear-moving with the increase of temperature, and temperature raises and moves to long wave direction, and temperature moves to shortwave direction while reduction.
After the grid region of fiber grating covering is corroded, the fibre core that is carved with grating is just exposed in the environment with certain refractive index, part transmission light will transmit in the medium outside fibre core with the form of evanscent field, have an effect with surrounding environment medium and affect the effective refractive index of transmission mode, finally causing the change of fiber grating reflection wavelength.For serving as the liquid of covering, in the time that temperature raises, its refractive index reduces, this thermo-optic effect can make that the effective refractive index of fibre core guided mode is corresponding to be reduced, cause reflection wavelength to move to shortwave direction, and core diameter size is less, the wavelength that this solution thermo-optic effect causes moves can be more obvious.And meet:
Wherein,
represent the cycle of fiber grating,
for the temperature variant thermo-optical coeffecient of solution refractive index, can be considered normal number.
for the coefficient of correspondence that covering solution variations in refractive index causes effective refractive index to change, it is the function of covering solution refractive index and core diameter.In the situation that core diameter is definite, the above-mentioned wavelength variations causing because of solution thermo-optic effect is not linear with temperature variation in theory, but experimental results show that, in the time that refractive index changes among a small circle, this variation relation can be considered linear relationship.Cause fiber grating reflection wavelength to move to long wave with respect to temperature increase, the reflection wavelength of liquid cladding fiber grating causes liquid refractivity to reduce effect with temperature rising and moves to shortwave direction, this identical external cause of temperature variation can make the reflection wavelength of fiber grating move round about, thereby realizes the compensation to temperature.Therefore, by above-mentioned relation Shi Ke get:
Utilize in this formula relevant ginseng preferably covering solution refractive index with and thermo-optical coeffecient, adopt method for packing of the present invention, the temperature compensation of realization to fiber grating.
Claims (3)
1. a liquid-packing optical fiber grating temperature compensation method, is characterized in that, comprises the following steps:
One, prepare micron diameter fiber grating, utilize hydrofluorite etching process that the silica glass of cladded-fiber grating is removed, only there is fibre core in the grid region of fiber grating, and fibre core is carried out to partial corrosion, makes the diameter of the fibre core in grid region reach 4～8 μ m;
Two, single-mode fiber prepared by step 1 is through quartz glass tube stretching without Prestressing, finished micron diameter fiber grating is carried out to column encapsulation with quartz glass tube, in quartz glass tube, fill the solution with refractive index and thermal refractive index coefficient, take out after the air in solution with vacuum pump, quartz glass tube two ends seal with adhesive, served as the covering of fiber grating by solution, utilize cladding index to increase the characteristic that reduces to cause fiber grating reflection wavelength violet shift with temperature, fiber grating reflection wavelength is increased to red shift Characteristic Compensation of Medical Sensors with temperature,
The refractive index of described solution is 1.4545 ~ 1.4560, and its thermal refractive index coefficient is 0.00026 ~ 0.00045 RIU/ ℃.
2. a kind of liquid-packing optical fiber grating temperature compensation method according to claim 1, is characterized in that, described fiber grating adopts Fiber Bragg Grating FBG.
3. a kind of liquid-packing optical fiber grating temperature compensation method according to claim 1, is characterized in that, comprises the following steps:
One, prepare micron diameter fiber grating, utilize hydrofluorite etching process that the silica glass of cladded-fiber grating is removed, only there is fibre core in the grid region of fiber grating, and fibre core is carried out to partial corrosion, makes the diameter of the fibre core in grid region reach 5 μ m;
Two, single-mode fiber prepared by step 1 is through quartz glass tube stretching without Prestressing, finished micron diameter fiber grating is carried out to column encapsulation with quartz glass tube, in quartz glass tube, fill refractive index and be 1.4550 solution, its thermal refractive index coefficient is 0.00038 RIU/ ℃, take out after the air in solution with vacuum pump, quartz glass tube two ends seal with adhesive, served as the covering of fiber grating by solution, utilize cladding index to increase the characteristic that reduces to cause fiber grating reflection wavelength violet shift with temperature, fiber grating reflection wavelength is increased to red shift Characteristic Compensation of Medical Sensors with temperature.
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| CN102759774A (en) * | 2012-07-02 | 2012-10-31 | 暨南大学 | Optical waveguide structure for achieving fiber bragg grating temperature compensation and preparation method of optical waveguide structure |
| CN104864918B (en) * | 2015-06-19 | 2017-05-24 | 西安石油大学 | Device and method for testing fiber bragg grating corrosion and liquid refractive index |
| CN107490821B (en) * | 2016-06-12 | 2020-03-20 | 天津大学 | Optical waveguide device insensitive to broadband temperature |
| CN108981810B (en) * | 2018-07-17 | 2021-07-27 | 西安石油大学 | Preparation method of novel optical fiber F-P cavity sensing device |
| CN109031515A (en) * | 2018-08-22 | 2018-12-18 | 长春理工大学 | A kind of fiber grating preparation method |
| US11966076B2 (en) | 2020-03-02 | 2024-04-23 | National Research Council Of Canada | High-temperature optical fiber transducer and method of producing same |
| CN112162347B (en) * | 2020-09-24 | 2022-03-29 | 武汉理工大学 | Liquid sapphire optical fiber cladding and preparation method thereof |
| CN113702172A (en) * | 2021-07-30 | 2021-11-26 | 南京航空航天大学 | Method for testing residual strain of resin curing |
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