KR20150059436A - Light based interferometer system - Google Patents

Abstract

According to an embodiment of the present invention, a light based interferometer system may comprise: a light source to guide light to an optical fiber; a micro-optical fiber to form one section in the optical fiber; a temperature sensitivity inhibitor which covers the outer side of the micro-optical fiber and has a negative thermooptical coefficient to inhibit temperature sensitivity; and an interference pattern measuring part connected to the optical fiber to measure interference patterns. According to the embodiment of the present invention, the light based interferometer system can accurately measure the physical quantity such as strain and pressure and reduce optical attenuation without being affected by temperature variations with the use of the temperature sensitivity inhibitor arranged in a detection section.

Description

[0002] Light based interferometer system [0003]

A light based interferometer system is disclosed. More specifically, a light-based interferometer system capable of accurately measuring physical quantities such as strain and pressure as well as optical loss without being affected by temperature changes is disclosed.

Optical fiber and optical waveguide-based interferometers are widely used in real-time deformations of various buildings, bridges, airplanes, ships, spacecraft, and accurate physical quantities such as pressure and twist. In particular, since the interferometer is independent of electromagnetic disturbance, it is easy to insert into a structure and has a high sensitivity, it is being watched as a next generation measurement system to replace a semiconductor-based sensor in the field of chemical gas detection and biomaterial detection.

Conventional temperature sensitivity suppression techniques for optical fiber and optical waveguide interferometers are based on the use of a single material such as a photonic crystal fiber or a polarization maintaining photonic crystal fiber, for example, a special optical fiber made of silica, a method for correcting temperature sensitivity through signal processing , And other types of optical elements are connected in parallel to measure the temperature and the physical quantity to be measured simultaneously.

However, in the case of an interferometer using a conventional photonic crystal fiber or a polarization-maintaining photonic crystal optical fiber, since a special optical fiber is used, the production cost is high, the loss is large, and since the optical fiber is bonded with other kinds of optical fibers, .

In addition, there are limitations in that a method for correcting the temperature sensitivity through signal processing or a method for performing simultaneous measurement by connecting in parallel requires a complicated system and a system size increases accordingly.

An object of an embodiment of the present invention is to provide a temperature sensing device capable of precisely measuring physical quantities such as strain and pressure without being affected by a temperature change by providing a temperature sensitive inhibiting material in a sensing section, To provide an interferometer system.

Another object of the present invention is to provide a light-based interferometer system capable of reducing the cost of constructing a system because it uses silica while having excellent durability against impact from the outside.

An optical fiber based interferometer system according to an embodiment of the present invention includes: a light source for guiding light to an optical fiber; A micro optical fiber forming a section of the optical fiber; A temperature sensitive suppressing material that surrounds the micro optical fiber from outside and suppresses temperature sensitivity by having a negative thermoluminescence coefficient; And an interference fringe measuring unit connected to the optical fiber to measure an interference fringe. According to this configuration, since the temperature sensitive suppressing substance is provided in the sensing unit, Not only can the physical quantity be accurately measured but also the optical loss can be reduced.

According to one aspect, the micro-optical fiber and the temperature-sensitive suppressing material may further include an externally surrounding protective cell.

According to one aspect of the present invention, the temperature sensitivity can be suppressed by canceling out the optical path change rate with respect to the effective refractive index of the light and the optical path change rate due to the thermal expansion, which are changed through the diameter control of the sensing unit in which the micro optical fiber is interposed.

According to one aspect of the present invention, the temperature sensitivity can be suppressed by canceling out the optical path change rate due to the change of the thermodynamic coefficient of the temperature sensitive material and the optical path change rate due to the thermal expansion.

According to one aspect, the temperature sensitivity suppressing material may be made of any one of materials including index matching oil, Teflon, low index epoxy, and polymer .

According to one aspect of the present invention, the optical fiber is divided into two bifurcations, and an optical coupler is coupled to each of the split portion and the gathered portion, and the micro optical fiber is divided into one of two bifurcated optical fibers by the optical coupler And the other of the optical fibers may be provided as a reference section.

According to one aspect, a polarization controller or an optical attenuator can be installed in the reference section to improve the extinction ratio of the interference fringes measured by the interference fringe measuring section.

Meanwhile, an optical waveguide-based interferometer system according to an embodiment of the present invention includes: an optical waveguide connected to the optical fiber by a connector coupling the light; A temperature sensitive suppressing material that surrounds a part of the optical waveguide from outside and suppresses temperature sensitivity by having a negative thermoluminescence coefficient; And an interference fringe measuring unit provided at an end of the optical fiber connected to the optical waveguide and the connector for measuring an interference fringe. According to this configuration, since the temperature sensitive suppressing substance is provided in the sensing unit, It is possible to accurately measure physical quantities such as the degree of deformation and pressure and reduce optical loss.

According to one aspect of the present invention, the optical path change rate to the effective refractive index of the light, which is changed through the diameter control of the sensing section formed on the optical waveguide to which the temperature sensitive suppression material is coupled, Or the temperature sensitivity can be suppressed by canceling out the optical path change rate due to the change of the thermodynamic coefficient of the temperature sensitive inhibiting material and the optical path change rate due to the thermal expansion.

According to one aspect, the temperature sensitive inhibiting material can be made of any one of materials including index matching oil, Teflon, low index epoxy, polymer.

Meanwhile, an optical fiber based interferometer system according to an embodiment of the present invention includes: a light source for guiding light to an optical fiber; A temperature sensitivity suppressing material provided in the optical fiber and suppressing temperature sensitivity by having a negative thermoluminescence coefficient; And an interference fringe measuring unit connected to the optical fiber to measure an interference fringe.

According to one aspect of the present invention, the optical fiber is a hollow optical fiber having an inner hole, and the temperature sensitivity suppressing material can be filled in the inner hole.

According to one aspect, the optical fiber is any one of a photonic crystal fiber, a polarization maintaining photonic crystal fiber, and a photonic band gap optical fiber, and the temperature sensitivity suppressing material may be filled or coated.

According to the embodiment of the present invention, since the temperature sensitive suppressing material is provided in the sensing section, it is possible to accurately measure the physical quantity such as the strain and the pressure without being affected by the temperature change, and reduce the optical loss.

Further, according to the embodiment of the present invention, since silica is used while having excellent durability against impact from the outside, the cost for constructing the system can be reduced.

1 is a schematic view illustrating a configuration of an optical fiber based interferometer system according to an embodiment of the present invention.
2 is a view showing a state where the temperature sensitive suppressing material and the protection cell are coupled to the micro optical fiber shown in FIG.
FIG. 3 is a graph showing the optical path change of the optical fiber based interferometer system according to the temperature change.
FIG. 4 is a graph showing a result of Fourier transform of the obtained interference fringes for simplification of the interferometer system.
5 is a Fourier transformed spatial frequency transformation graph with temperature variation.
FIG. 6 is a diagram illustrating a schematic configuration of an optical waveguide-based interferometer system according to another embodiment of the present invention.
FIG. 7 is a view schematically showing the configuration of a temperature sensitivity suppressing material surrounding the sensing unit in FIG.

Hereinafter, configurations and applications according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION The following description is one of many aspects of the claimed invention and the following description forms part of a detailed description of the present invention.

In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

FIG. 1 is a view schematically showing a configuration of an optical fiber based interferometer system according to an embodiment of the present invention. FIG. 2 shows a state where a temperature sensitive suppressing material and a protective cell are coupled to the micro optical fiber shown in FIG. 1 FIG.

Referring to FIG. 1, an optical fiber based interferometer system 100 according to an embodiment of the present invention includes a light source 110 for guiding light to an optical fiber 111, a light source 110 for guiding light from the light source 110 to the optical fiber 111, A micro optical fiber 130 interposed in one of two branches of a split optical fiber 111 and a micro optical fiber 130 which surrounds the micro optical fiber 130 from outside, A temperature sensitive suppressing material 150 for suppressing the temperature sensitivity by having the optical fiber 111 and the optical coupler 120 coupled to a part where the bifurcated optical fiber 111 is gathered again to collect light, And an interference fringe measuring unit 140 provided at an end of the fringe measuring unit 140 to measure an interference fringe.

With such a configuration, it is possible to measure the physical quantity such as the deformation degree and the pressure without being affected by the temperature change, thereby improving the accuracy and reducing the optical loss.

To describe each configuration, the light source 110 of the present embodiment may be provided as a spontaneous emission light source. For example, a white light source, a broadband supercontinuum light source, a super luminescent diode (SLD) light source, , An LED, and a laser.

The optical coupler 120 of the present embodiment is provided in the bifurcated portion and the collected portion of the optical fiber 111 so that light can be sent to both optical fibers 113 and 115 and the light can be gathered again . The optical coupler 120 may be provided at a ratio of 5 to 5 in order to improve the extinction ratio of the interference pattern. However, the present invention is not limited to this, and it is of course possible to provide, for example, 7: 3, 8: 2, 9: 1 or the like.

Meanwhile, the optical fiber 111 of the present embodiment may be formed of a single mode optical fiber. In single-mode fiber, the diameter of the core is extremely small, so the light propagation mode is unified and the output wavelength can be more accurate. However, the type of the optical fiber 111 is not limited thereto, and any one of a polarization maintaining optical fiber, a photonic bandgap optical fiber, a hollow optical fiber, an optical fiber such as a photonic crystal optical fiber, a polarization maintaining photonic crystal fiber and a dispersion compensating optical fiber may be applied .

The interference fringe measuring unit 140 of the present embodiment can be provided as an optical spectrum analyzer that measures interference fringes through optical spectrum measurement. However, the present invention is not limited thereto, and it is of course possible to provide a spectrometer or a photo detector.

As described above, the optical fiber 111 is divided into two parts. One of the optical fibers 113 is connected to the micro optical fiber 130, which is used as a sensing part for sensing, and the other optical fiber 115 It can be applied as a standard sector.

2, the micro-optical fiber 130 has a diameter smaller than that of the connected optical fiber 111. The temperature-sensitivity suppressing material 150 is surrounded on the outer side and the micro-optical fiber 130 and the temperature- A protection cell 160 may be coupled to protect the second electrode 150. [

Therefore, the interferometer system 100 can be realized with a small and simple structure because it has excellent durability even when an external impact is applied, and is manufactured on a silica-based basis.

Here, the temperature sensitivity inhibiting material 150 has a negative thermodynamic coefficient to suppress the temperature sensitivity. The material may be an index matching oil, a Teflon, a low index epoxy, and polymer may be used. However, the present invention is not limited thereto.

On the other hand, although not shown, a polarization controller or an optical attenuator can be attached to the other optical fiber 113 forming the reference section, and the extinction ratio of the interference pattern measured by the interference fringe measuring section 140 can be improved .

With this configuration, the temperature sensitivity can be suppressed by canceling out the optical path change rate with respect to the effective refractive index of the light and the optical path change rate due to the thermal expansion, which are changed through the diameter control of the sensing section in which the micro-optical fiber 130 is interposed.

Alternatively, the temperature sensitivity may be suppressed by offsetting the optical path change rate due to the change in the thermoelectric coefficient number of the temperature sensitivity suppressing material 150 and the optical path change rate due to the thermal expansion.

Hereinafter, the process of measuring the interference fringe using the optical fiber based interferometer system 100 having the above-described structure will be described.

First, when heat is applied to the interferometer system 100 of the present embodiment, a light path difference occurs between a portion of the micro-optical fiber 130 forming the sensing portion and the optical fiber 115 forming the reference portion, can do. The wavelength interval (?) Of the interference fringe can be expressed by the following equation (1).

......식 1

Equation 1

Herein, n1, n2 and n3 represent the refractive index of the portion of the micro-optical fiber 130, the refractive index of the optical fiber 113 forming the sensing portion, and the refractive index of the optical fiber 115 forming the reference portion, And? Represents a wavelength.

As the temperature around the interferometer system 100 increases, the length of the refractive index of the optical fiber 111 increases, so that the optical path difference Δξ at both ends increases and the wavelength interval of the interference fringes becomes relatively small. In order to suppress the influence of the temperature, a temperature sensitive suppressing material 150 having a negative thermoluminescence coefficient is coated on the micro-optical fiber 130. The wavelength interval (?) That varies with temperature can be expressed by the following equation (2).

Equation 2

이 음의 값을 가지게 된다. 또한 마이크로 광섬유(130)의 직경을 조절하면 마이크로 광섬유(130) 주변으로 퍼지는 소산장의 크기를 조절할 수 있기 때문에 소산장의 크기에 의해 결정되는 (δn₁/δ_nambient)의 값을 조절해 줄 수 있다. 따라서 식 2의

과

의 값이 같아지도록 직경을 최적화 하면 온도 변화에 대한 파장 간격의 변화를 상쇄시킬 수 있다. 즉 온도 변화에 영향이 없는 간섭계 시스템(100)을 구축할 수 있는 것이다.Where n _ambient is the index of refraction of the temperature sensitive inhibitor 150, σ _ambient is the thermodynamic coefficient of the temperature sensitive inhibitor 150, and α is the thermal expansion coefficient of the silica. When a temperature sensitive inhibiting material 150 having a negative thermodynamic coefficient is coated,

And has a negative value. Also can adjust the value of (δn ₁ / δ _nambient) which is determined by the dissipation sheet size, because the micro fiber by adjusting a diameter of 130 to control the dissipation sheet size which spreads around the micro-fiber (130). Therefore,

and

Optimizing the diameter to equalize the value of the wavelength can offset the change in the wavelength interval to the temperature change. That is, the interferometer system 100 having no influence on the temperature change can be constructed.

In order to simplify the interferometer system 100, the obtained interference fringe is Fourier-transformed to obtain a graph having one peak. By measuring the peak, physical quantities such as strain and pressure can be measured irrespective of temperature have.

Referring to FIG. 3, the optical path change of the optical fiber based interferometer system according to the temperature change can be seen. 3, it can be confirmed that the optical path is not changed by the compensation effect of the temperature sensitivity suppressing material 150. FIG.

Meanwhile, FIG. 4 is a graph showing the result of Fourier transform of the obtained interference fringes for simplification of the interferometer system. In this embodiment, since there is almost no change in the wavelength interval of the interference fringes with respect to the temperature variation, Value. ≪ / RTI >

5 is a Fourier-transformed spatial frequency conversion graph according to a temperature change. In the present embodiment, since the optical path difference does not change due to the temperature sensitivity suppressing material 150, it can be understood that the spatial frequency subjected to the Fourier transform also does not change have.

As described above, according to the embodiment of the present invention, the temperature sensitive inhibiting material 150 wraps the micro-optical fiber 130 formed in the sensing section, so that the physical quantity such as the deformation degree and the pressure can be accurately measured In addition, since the silica can be used while having excellent durability against impact from the outside, which can reduce the optical loss, there is an advantage that the cost for constructing the system can be reduced.

Hereinafter, the optical waveguide substrate interferometer system 100 according to another embodiment of the present invention will be described with respect to portions substantially the same as those of the optical fiber based interferometer system 100 of the above-described embodiment .

As shown in these drawings, the optical waveguide-based interferometer system 200 according to another embodiment of the present invention includes a light source 210 for guiding light to an optical fiber, and a connector (not shown) An optical waveguide 213 connected to the optical fiber 211 and a temperature sensitive suppression material 250 that surrounds the optical waveguide 213 from outside to suppress the temperature sensitivity by having a negative thermoregulatory coefficient, And an interference fringe measuring unit 240 provided at an end of the optical fiber 211 connected to the optical fiber 213 by a connector and measuring an interference fringe.

In this embodiment, the optical waveguide 213 has a structure that is divided from the connector into two parts and is collected again from the other connector. The temperature sensitive suppressing material 250 is coated on a part of the one-way optical waveguide 213, and the other optical waveguide 213 can be applied as the reference part.

Through this, the temperature sensitivity can be suppressed by canceling the optical path change rate with respect to the effective refractive index of light, which is changed through the diameter control of the sensing section, and the optical path change rate due to thermal expansion. Alternatively, the temperature sensitivity may be suppressed by offsetting the optical path change rate due to the change in the thermoelectric coefficient number of the temperature sensitivity suppressing material 250 and the optical path change rate due to the thermal expansion.

Meanwhile, since the temperature sensitivity compensation principle of the optical waveguide based interferometer system 200 having such a configuration and the experimental results according to the principle substantially correspond to the interferometer system 100 (see FIG. 1) of the above-described embodiment, .

In the above-described embodiment, the case where the temperature sensitive suppressing material 150 is coated on the micro optical fiber 130 which is relatively thin compared to the diameter of the surrounding optical fiber has been described, but the present invention is not limited thereto.

For example, one section of the optical fiber forming the sensing section is provided with a hollow hollow optical fiber having an inner hole, and the inner hole is filled with the temperature sensitivity suppressing material, thereby being not affected by the ambient temperature It is of course possible to measure physical quantities such as strain or pressure.

For example, a photonic crystal fiber, a polarization-maintaining photonic crystal fiber, a photonic bandgap optical fiber, or the like can be applied as the kind of the optical fiber, and the temperature sensitive material can be applied to the optical fiber As shown in FIG.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

100: Fiber-based interferometer system
110: Light source
111: Optical fiber
130: Micro optical fiber
140: interference fringe measuring unit
150: Temperature Sensitivity Inhibiting Substance
160: Protection cell

Claims (13)

A light source for guiding light to an optical fiber;
A micro optical fiber forming a section of the optical fiber;
A temperature sensitive suppressing material that surrounds the micro optical fiber from outside and suppresses temperature sensitivity by having a negative thermoluminescence coefficient; And
An interference fringe measuring unit connected to the optical fiber to measure an interference fringe;
/ RTI > The system of claim < RTI ID =
The method according to claim 1,
Further comprising an externally encapsulating protective cell to protect the micro-optical fiber and the temperature sensitive inhibiting material.
The method according to claim 1,
The optical fiber based interferometer system suppresses the temperature sensitivity by canceling the optical path change rate with respect to the effective refractive index of the changed light and the optical path change rate due to the thermal expansion through the diameter control of the sensing unit with the micro optical fiber interposed therebetween.
The method according to claim 1,
A fiber-based interferometer system that suppresses temperature sensitivity by offsetting the optical path change rate due to a change in the thermo-optic coefficient of the temperature sensitive suppression material and the optical path change rate due to thermal expansion.
The method according to claim 1,
Wherein the temperature sensitive inhibiting material can be manufactured from any one of materials including index matching oil, Teflon, low index epoxy, and polymer.
The method according to claim 1,
The optical fiber is divided into two bifurcations, and the optical coupler is coupled to the split portion and the gathered portion, respectively,
Wherein the micro-optical fiber is provided as a sensing section in one of the bifurcated optical fibers by the optical coupler, and the other of the optical fibers is provided in a reference section.
The method according to claim 6,
Wherein a polarization controller or an optical attenuator is mountable in the reference section to improve an extinction ratio of the interference fringe measured by the interference fringe measuring section.
A light source for guiding light to an optical fiber;
An optical waveguide connected to the optical fiber by a connector coupling the light;
A temperature sensitive suppressing material that surrounds a part of the optical waveguide from outside and suppresses temperature sensitivity by having a negative thermoluminescence coefficient; And
An interference fringe measuring unit provided at an end of the optical fiber connected to the optical waveguide and the connector, for measuring an interference fringe;
And an optical waveguide-based interferometer system.
9. The method of claim 8,
The temperature sensitivity can be suppressed by offsetting the optical path change rate with respect to the effective refractive index of the light and the optical path change rate due to the thermal expansion through the diameter control of the sensing section formed in the optical waveguide to which the temperature-
The optical waveguide-based interferometer system suppresses temperature sensitivity by canceling the optical path change rate due to the change of the thermodynamic coefficient of the temperature sensitive suppression material and the optical path change rate due to the thermal expansion.
9. The method of claim 8,
Wherein the temperature sensitive inhibiting material can be made of any one of materials including index matching oil, Teflon, low index epoxy, polymer.
A light source for guiding light to an optical fiber;
A temperature sensitivity suppressing material provided in the optical fiber and suppressing temperature sensitivity by having a negative thermoluminescence coefficient; And
An interference fringe measuring unit connected to the optical fiber to measure an interference fringe;
/ RTI > The system of claim < RTI ID =
12. The method of claim 11,
Wherein the optical fiber is a hollow optical fiber having an inner hole, and the temperature sensitivity suppressing material can be filled in the inner hole.
12. The method of claim 11,
Wherein the optical fiber is any one of a photonic crystal fiber, a polarization maintaining photonic crystal fiber, and a photonic band gap optical fiber, and the temperature sensitivity suppressing material is filled or coated.

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