KR101343954B1 - Optical fiber and, sensor system and sensing method using the same - Google Patents

Abstract

A cladding extending to a predetermined length, and a core extending along the longitudinal direction of the cladding in the cladding, wherein the core has a refractive index different from the core and interferes with a path of light passing through the core. A plurality of gratings are formed along the longitudinal direction of the core, and the plurality of gratings are arranged at different intervals, and when light is irradiated to a light inlet, a portion of the light passing through the core is transferred to the plurality of gratings. The reflected light is reflected by a grating and output through the light inlet, and the reflected light output through the light inlet includes first and second reflected light polarized in different directions, and the first and second reflected light An optical fiber is provided that forms the wavelength spectrum of another band.

Description

Optical fiber and sensor system and sensing method using the same

The present invention relates to an optical fiber, a sensor system and a sensing method using the same, and more particularly, to a sensor system and a sensing method capable of detecting a position, a direction, and a curvature in which an optical fiber is refracted by using one optical fiber. will be.

Various endoscope equipments used for endoscopy and the like are attracting attention because they can minimize wounds caused by invasion. However, in medical practice using endoscopy equipment, it is difficult for the user to visually check the state of refraction of the endoscope equipment that is frequently refracted in the human body. This needs to be taken.

To this end, a method of using an optical fiber that can be refracted in response to the movement of the endoscope equipment refracted in various directions in the human body has been proposed.

Fig. 1 schematically shows an optical fiber structure according to the prior art.

The optical fiber 1 includes a cladding 2 formed of a glass material and freely refractable and a core 3 formed along the longitudinal direction of the cladding 2 at the center of the cladding 2. The optical fiber 1 is made of glass, . The refractive index of the cladding 2 is n _1, and the refractive indices of the core 3 are different from each other with n ₀ . At both ends of the optical fiber 1, a light inlet 5 through which light is incident from a light source (not shown) and a light outlet 6 through which light is output through the core 3 are formed.

A plurality of gratings 4 are formed in the core 3 at equal intervals A along the longitudinal direction of the core 3 in order to detect whether or not the optical fiber 1 has been refracted. Grid 4 is a portion through which the infrared light in the manufacturing process of the optical fiber 1 changes in the core 3, the physical properties of the part, and has a refractive index (n ₀ + △ n).

The grating 4 interferes with the incident light 3 passing through the core 3, and a part of the incident light 3 is reflected by the plurality of gratings 4 to the reflected light 8 through the light inlet 5. Is output.

FIG. 2 (a) shows the wavelength spectrum of the wavelength versus magnitude of the incident light incident through the light inlet 5, and FIG. 2 (b) shows the wavelength spectrum of the reflected light output through the light inlet 5 It is.

Even though incident light having a broad band wavelength is incident on the core 3, only reflected light of a specific wavelength λ _B through the light inlet 5 due to interference by a plurality of gratings 4 located in the middle of the core 3. Is output. Specifically, a part of the incident light incident through the light inlet 5 hits and reflects the first lattice located first, and the other part advances through the first lattice. Some of the light passing through the first lattice hits the second lattice and is reflected, and the reflected light meets again with the first lattice, some pass through it and merges with the first reflected light by the first lattice, and the rest Is reflected back by the first lattice to the second lattice. This phenomenon occurs repeatedly in the gratings located after the second grating, and the incident light incident on the optical fiber 1 interferes with each other while being repeatedly reflected and passed by the plurality of gratings 4. As a result, even though incident light having a wavelength spectrum of the form shown in FIG. 2 (a) is incident, as shown in FIG. 2 (b), almost all reflected light of wavelengths other than the wavelength λ _B is lost due to interference by each other. , Only the reflected light 8 having the wavelength λ _B is output through the light inlet 5.

In this case, the wavelength λ _B of the reflected light may be expressed as shown in Equation 1 below.

[Equation 1]

λ _B = 2 n _eff

Here, n _eff is an index which shows the effective refractive index of a core.

When a refraction occurs in a specific portion of the optical fiber 1 having the above-described configuration, a change occurs in the wavelength spectrum while the lattice spacing of the refracted portion changes. By detecting the change of the wavelength spectrum, it is possible to confirm whether or not the optical fiber 1 is refracted.

However, the optical fiber 1 of the above-described configuration can analyze whether the optical fiber 1 is refracted by analyzing the reflected light, but there is a problem in that the location and direction of refraction cannot be confirmed.

3 shows an optical fiber 10 according to another form of the prior art.

The optical fiber 10 includes the cladding 20 and the core 30 in the same manner as described above. The refractive indices of the cladding 20 and the core 30 are different from each other.

The core 30 is formed with first to fifth grid portions 41 to 45, each of which consists of three gratings. The three gratings forming each grating portion are arranged at equal intervals from each other. The spacings Λ ₁ , Λ ₂ , Λ ₃ , Λ ₄ , Λ ₅ of the three lattices constituting the first to fifth grid portions 41 to 45 are Λ ₁ <Λ ₂ <Λ ₃ <Λ ₄ < Has a relationship of Λ ₅ . The spacings 51, 52, 53, 54 between the first and fifth lattice portions 41 to 45 are significantly larger than the spacings of the lattice Λ ₁ , Λ ₂ , Λ ₃ , Λ ₄ , Λ ₅ . .

According to the above configuration, interference caused by the grating parts occurs with respect to the light incident to the light inlet 50 of the optical fiber 10, and the reflected light output to the light inlet 50 has a wavelength as shown in FIG. 4. Has a spectrum.

The wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ , λ ₅ appearing in the wavelength spectrum of FIG. 4 correspond to the intervals Λ ₁ , Λ ₂ , Λ ₃ , Λ ₄ , Λ ₅ of the gratings of the respective grating portions. Corresponds to the value obtained by substituting Equation 1. In other words, the wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ , and λ ₅ represent the wavelengths of the reflected light reflected and output by the first to fifth grid portions 41 to 45, respectively.

When the optical fiber 10 is refracted at the portion where the second lattice portion 42 is located, the spacing Λ ₂ of the gratings constituting the second lattice portion 42 will change, and according to the above equation 1], it is possible to observe the shift of the curve for the wavelength λ ₂ of the wavelength curves of FIG. It can be seen that the optical fiber 10 is refracted at the position of the second lattice portion 42 when the curve for the wavelength λ ₂ is observed to shift left and right.

On the other hand, by using at least three strands of the optical fiber 10 in a bundle can be used to calculate the refraction direction and the angle. For example, when the portion where the second grid portion 42 is located is bent, the second grid portion 42 of the optical fiber 10 located in the bent direction is compressed to shorten the wavelength of the reflected light, so that the wavelength curve is leftward. The second grid portion 42 of the optical fiber 10 positioned on the opposite side of the optical fiber 10 is extended to extend the wavelength of the reflected light so that the wavelength curve is shifted to the right. Therefore, by analyzing the change in the wavelength spectrum of each of the three or more optical fibers 10 bound together, it is possible to calculate the direction and angle of refraction.

However, in the optical fiber 10 as described above, when refraction occurs between the lattice portions 51, 52, 53, and 54, the lattice spacing of the lattice portions does not change, and thus the refraction position cannot be found. Thus, the gaps 51, 52, 53, 54 between the grating portions form a so-called "dead zone" in which the refraction position cannot be confirmed. There is a problem that the refractive position cannot be accurately sensed due to the presence of the "dead zone" at very large intervals.

In addition, the resolution for accurately calculating the refraction position calculation is low because one grating portion is composed of a plurality of gratings arranged at equal intervals.

For example, when the refraction occurs in the vicinity of the first grating of the second lattice portion 42 and when the refraction occurs in the vicinity of the last grating, the curve for the wavelength λ ₂ is shifted in the same aspect, so that the change in the wavelength curve There is a problem that it is difficult to determine the exact location of the refraction because the two cases can not be distinguished through. The spacing between the first and last gratings is usually 5-10 mm.

Furthermore, in order to detect the refraction direction using the optical fiber 10, since several strands of the optical fiber 10 must be bundled and used, there is a problem in that the overall size of the equipment using the optical fiber 10 is increased as well.

Korean Patent Publication No. 10-1998-076791

The present invention is to solve the problems of the prior art as described above, when the optical fiber is refracted by using one optical fiber can detect both the refracted position, the direction and the angle and curvature, the refractive state of the endoscope equipment, etc. An object of the present invention is to provide an optical fiber suitable for use as a sensor to grasp, a sensor system and a sensing method using the same.

According to an aspect of the present invention for achieving the above object, it comprises a cladding extending to a predetermined length, the core extending in the longitudinal direction of the cladding inside the cladding, the core and the refractive index inside the core A plurality of different gratings are formed along the longitudinal direction of the core so as to interfere with a path of light passing through the core, and the plurality of gratings are arranged at different intervals, respectively, to light inlets of the core. When light is irradiated, a part of the light passing through the core is reflected by the plurality of gratings and is output through the light inlet, and the reflected light output through the light inlet is polarized in the first reflection light polarized in different directions and An optical fiber comprising a second reflected light, wherein the first reflected light and the second reflected light form a wavelength spectrum of a different band; It is.

The spacing of the plurality of gratings may increase or decrease in a constant function from the light inlet to the light outlet.

In addition, the core may have a density different from the horizontal axis direction density and the vertical axis direction density so that a wavelength difference between the first reflected light and the second reflected light may occur.

According to another aspect of the invention, the optical fiber, a light source for irradiating light to the light inlet of the optical fiber, and an optical analyzer for analyzing the wavelength of the reflected light output from the light inlet of the optical fiber, the core The center of the optical fiber is disposed spaced apart from the center of refraction of the entire sensor used, the optical analyzer is refracted by detecting a change in the wavelength spectrum of the first reflected light and the second reflected light when the sensor is refracted A sensor system is provided for detecting position and orientation.

The optical analyzer may further detect an angle in a refracted direction by detecting a change in a wavelength spectrum of the first reflected light and the second reflected light.

The optical analyzer may further detect the curvature of refraction by detecting a change in the wavelength spectrum of the first reflected light and the second reflected light.

According to still another aspect of the present invention, there is provided a method of detecting a refractive state of an optical fiber by using the sensor system, the method comprising: irradiating light to a light inlet of the optical fiber, first reflected light and a first light output from the light inlet; Collecting the reflected light, analyzing a change in the wavelength spectrum of the first reflected light and the second reflected light, and calculating a change amount when there is a change in the wavelength spectrum of the first reflected light and the second reflected light. A sensing method is provided that includes detecting a position and a direction in which a fiber is refracted.

The method may further include detecting an angle and a curvature in a direction in which the optical fiber is refracted by calculating a change amount when there is a change in the wavelength spectrum of the first reflected light and the second reflected light.

Figure 1 shows an optical fiber according to an aspect of the prior art.
Fig. 2 shows the wavelength spectrum of incident light and reflected light through the light entrance of the optical fiber of Fig. 1. Fig.
3 shows an optical fiber according to another form of the prior art.
4 illustrates a wavelength spectrum of reflected light output through a light inlet of the optical fiber of FIG. 3.
5 and 6 are side and front views, respectively, of an optical fiber according to an embodiment of the present invention.
FIG. 7 illustrates a state of use of the optical fiber of FIG. 5.
FIG. 8 illustrates a wavelength spectrum of reflected light output through a light inlet of the optical fiber of FIG. 5.
9 and 10 are diagrams for illustrating the principle of detecting the refraction position of the optical fiber of FIG.
11 and 12 are diagrams for illustrating the principle of detecting the degree of refraction of the optical fiber of FIG.
FIG. 13 is a diagram for illustrating a principle of detecting a refractive direction and an angle of the optical fiber of FIG. 5 together with FIGS. 5 and 7.
14 illustrates a sensor system according to one embodiment of the invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Although the present invention has been described with reference to the embodiments shown in the drawings, this is described as one embodiment, whereby the technical spirit of the present invention and its core configuration and operation are not limited.

FIG. 5 is a side view of the optical fiber 100 according to an embodiment of the present invention, and FIG. 6 is a front view of the optical fiber 100 of FIG. 5.

5 and 6, the optical fiber 100 includes a cladding 110 extending to a predetermined length and a core 120 extending along the longitudinal direction of the cladding 110 inside the cladding 110. do. A buffer for surrounding the cladding 110 and a jacket for enclosing the buffer may be formed on the outer periphery of the cladding 110, but are not shown in the present embodiment.

The optical fiber 100 is mainly made of a glass material such as silica (SiO ₂ ). The cladding 110 is made of pure silica and the core 120 is made of silica doped with germanium (Ge doped SiO ₂ ), so that refractive indexes are different from each other. At both ends of the optical fiber 100, a light inlet 130 through which light is incident from a light source (not shown) and a light outlet 140 through which light is output through the core 120 are formed.

As shown in FIG. 5, a plurality of gratings g ₁ , g ₂ ,... G _a ,... G _n are formed in the core 120 along the longitudinal direction of the core 120. Differs from the refractive index of the core 120 of the plurality of gratings g ₁ , g ₂ , ... g _a , ... g _n . On the other hand, the refractive indices of the plurality of gratings g ₁ , g ₂ , ... g _a , ..., g _n are equal to each other.

The plurality of gratings g ₁ , g ₂ , ... g _a , ..., g _n are spaced apart by different distances Λ ₁ , Λ ₂ , Λ _a , ... Λ _n-1 do. According to this embodiment, the spacing (Λ ₁ , Λ ₂ , ..., Λ _a , ... Λ _n-1 ) between the gratings increases from the light inlet 130 to the light exit 140 as _a constant function. According to this embodiment, the spacing (Λ ₁ , Λ ₂ , ... Λ _a , ... Λ _n-1 ) between the gratings gradually increases at a constant rate. According to this embodiment, the spacing (Λ ₁ , Λ ₂ , ... Λ _a , ... Λ _n-1 ) between the gratings increases with a constant function, but the spacing (Λ ₁ , Λ ₂ , .. it will be understood that also a _{Λ a, ... Λ n-1} ) so as to decrease at a constant function.

On the other hand, the core 120 of the optical fiber 100 has a density in the horizontal axis (x) direction larger than a density in the vertical axis (y) direction. The density difference between the horizontal axis and the vertical axis of the core 120 is achieved by the stress enhancing unit 160.

The stress enhancing unit 160 is formed by inserting a material having a thermal expansion coefficient different from that of the cladding 110 into the cladding 110. As shown in FIG. 6, two stress intensifiers 160 are symmetrically formed on the horizontal axis of the optical fiber 100 about the core 120.

A process of forming the stress enhancing portion 160 on the optical fiber 100 will be described. First, a cylindrical base material for forming the optical fiber 100 is drilled at a position where the stress-strengthening portion 160 is to be formed, and the material of the stress-strengthening portion 160 is inserted. When the base material manufacturing process of the optical fiber is completed at a high temperature, and the base material is drawn and cooled, the optical fiber 100 is formed. At this time, due to the difference in the coefficient of thermal expansion between the cladding 110 and the stress-strengthening portion 160, there occurs a difference in shrinkage in the horizontal direction and shrinkage in the vertical direction, so that tensile stress is generated only in one direction in the core 120.

According to the present embodiment, the two stress-strengthening portions 160 are formed symmetrically on the horizontal axis of the optical fiber 100 about the core 120, and the thermal expansion coefficient of the stress- ) Are used. In this case, when the stress reinforcement 160 is contracted less than the cladding 110, the stress reinforcement 160 compresses the core 120 in the horizontal axis direction of the optical fiber 100. With this configuration, the core 120 of the optical fiber 100 has a density in the horizontal axis (x) direction larger than that in the vertical axis (y) direction.

In the core 120 of the optical fiber 100, the density in the horizontal axis x direction becomes larger than the density in the vertical axis y direction, and the refractive index in the horizontal axis x direction becomes larger than the refractive index in the vertical axis y direction. . In addition, the refractive index in the horizontal axis (x) direction of the plurality of gratings formed by changing the physical properties of the core 120 is larger than the refractive index in the vertical axis (y) direction.

Therefore, when light incident through the light entrance of the core 120 and having undergone interference by a plurality of gratings is again emitted through the light entrance, reflected light polarized in the horizontal axis (x) direction and reflected light polarized in the vertical axis (y) Have a wavelength difference DELTA lambda.

Hereinafter, the reflected light characteristic of the optical fiber 100 according to the present embodiment will be described in more detail with reference to FIG. 7.

A plurality of grid when light enters through the light entrance 130 of the optical fiber _{(100) (g 1, g} 2, ... g a, ... g n) of the reflected light is the light entrance 130, reflected by the Is output.

As described above, since the spacing between the plurality of gratings g ₁ , g ₂ ,... G _a ,... G _n increases at a constant rate, the wavelength spectrum of the reflected light has a wide band as shown in FIG. 8. It is represented by the curve (C _x , C _y ) having the wavelength of the band.

The peaks of the curves C _x and C _y correspond to the peaks of the reflected light of each of the plurality of gratings g ₁ , g ₂ , ... g _a , ..., g _n , respectively, (? ₁ ,? ₂ , ...? _A , ...? _N ).

As described above, the wavelength difference Δλ occurs between the reflected light polarized in the horizontal axis x direction and the reflected light polarized in the vertical axis y direction output through the light inlet of the core 120. Thus, as shown in FIG. 7, the reflected light polarized in the horizontal axis x direction and the reflected light polarized in the vertical axis y direction are represented by two curves C _x and C _y having different bands from each other. The two curves C _x and C _y independently represent the wavelength of the reflected light by each of the plurality of gratings g ₁ , g ₂ , ... g _a , ..., g _n . For example, in the curves (C _x , C _y ), the wavelength (λ _x1 ) and the wavelength (λ _y1 ) both represent the wavelength of the reflected light reflected by the grating (g ₁ ). The wavelength (λ _x1 ) and the wavelength (λ _y1 ) have wavelength differences of Δλ.

The optical fiber 100 according to the present embodiment has a wavelength that is detected as the distance between the plurality of gratings g ₁ , g ₂ ,... G _a ,... G _n increases or decreases similarly to the related art. Changes detect the state of refraction. When the center of the optical fiber 100 is equal to the center of refraction of the entire optical fiber 100, since the average of the lattice spacing based on the center of the optical fiber 100 is 0 The distance between the adjacent two gratings increases in one part, whereas in the opposite part, the distance between the two gratings decreases, so that the change in mean spacing is substantially zero).

Therefore, as shown in FIG. 8, according to the present embodiment, the center of the core 120 is spaced apart from the center of refraction of the entire optical fiber 100. As a method of allowing the center of the optical fiber 100 to be spaced apart from the actual center of refraction, as shown in FIG. 8, the center of the optical fiber 100 is the center of the endoscope equipment 150 to which the optical fiber 100 is applied. That is, there is a method to be located in a different part from the center of refraction. In addition, a thin but strong support core (not shown) is attached to the outside of the optical fiber 100 so that the support core is a refractive center of the optical fiber 100 so that the core located at the center of the optical fiber 100 ( The center of 110 may be spaced apart from the center of refraction.

With the center of the optical fiber 100 spaced apart from the actual center of refraction, for example when the endoscope equipment 150 is bent in direction 1 (FIG. 8), the gratings of the optical fiber 100 at the bent portion are substantially All are compressed to reduce the spacing between the gratings.

Hereinafter, a process of detecting the position where the optical fiber 100 is refracted will be described with reference to FIGS. 9 and 10.

As described above, the optical fiber 100 according to the present embodiment uses both the reflected light polarized in the horizontal axis (x) direction and the reflected light polarized in the vertical axis (y) direction to determine the refractive state. For convenience, only the wavelength spectrum of the reflected light polarized in the horizontal axis (x) direction is shown. In addition, FIG. 10 simultaneously shows a curve C _before indicating a state _before refraction occurs and a curve C _after indicating after the refraction occurs.

Assuming that the optical fiber 100 is refracted at refracted portion 1 (FIG. 9), the spacing between the grating located at refracted portion 1 and its adjacent grating is varied (FIG. 10 shows the grating at refracted portion 1 due to refraction). If the gap is refracted in the increasing direction). Accordingly, the wavelength of the reflected light due to the grating located at the refracting portion 1 also changes. As a result, as shown in FIG. 10, the magnitude R of light at wavelength λ ₁ decreases, and due to the change in wavelength of reflected light by the grating located at the refractive portion 1, the wavelength near wavelength λ ₁ The peak P ₁ is generated as the light intensity of the changed reflected light wavelength) increases.

When the optical fiber 100 is refracted once more in the refraction portion 2, as shown in FIG. 10, the wavelength λ ₂ of the reflected light by the grating located in the refraction portion 2 moves laterally, and the peak P ₂ is moved. Will occur.

According to the present embodiment, since the wavelength of the reflected light by each of the plurality of gratings in the state where the optical fiber 100 is not refracted is known, the above-described principle is used in reverse and the wavelength at which the size of the reflected light in the wavelength spectrum of the reflected light decreases The position of the lattice corresponding to the reflected light of the wavelength can be detected. That is, when the optical fiber 100 is refracted, it is possible to detect the occurrence of refraction at a position where a lattice is located through the change of the wavelength spectrum.

Hereinafter, the principle of detecting the degree of refraction of the optical fiber 100 will be described with reference to FIGS. 11 and 12.

12 illustrates only a wavelength spectrum of reflected light polarized in the horizontal axis (x) direction for convenience of description. In addition, FIG. 12 simultaneously shows the wavelength spectral curve R1 corresponding to the case of FIG. 11A and the wavelength spectral curve R2 corresponding to the case of FIG. 11B.

11 (a) and 11 (b) show a case in which the optical fiber 100 is refracted at the same point, but the degree of refraction is different. FIG. 11A shows a more refracted state than that in FIG. 11B (ie, r1 <r2). In both cases, as shown in Fig. 12, it is confirmed that the curves R1 and R2 generate peaks at almost the same wavelength, but the peaks R are formed to be different from each other. Therefore, the degree of refraction of the optical fiber 100 can be detected by analyzing the magnitude of the peak generated by the refraction.

Hereinafter, the principle of detecting the direction and the angle at which the optical fiber 100 is refracted will be described with reference to FIGS. 5, 8, and 13.

The optical fiber 100 at the position lattice (g _a) of Figure 5, when it is refracted in the direction 3 in FIG. 8, the grating (g _a) and the x-axis direction interval (Λ _x) and y-axis direction of the grating adjacent to the The interval Λ _y is all increased.

The increase in wavelength (λ _ax) of the reflected light by the grating (g _a) As the x-direction spacing of the lattice (Λ _x) is increased. Therefore, even on the right side than the 13 (a), the reduction in size of the light having a wavelength (λ _ax) at a wavelength spectrum curve to the R value is decreased at a wavelength (λ _ax) and wavelength (λ _ax) as shown in The peak P _1x occurs at the located wavelength λ _ax + Δλ _x .

On the other hand, increases the wavelength (λ _ay) of the reflected light by the grating (g _a) As the y-axis direction interval between gratings (Λ _y) is increased. Accordingly, on the right side than Fig. 13 (b), the reduction in size of the light having a wavelength (λ _ay) at a wavelength spectrum curve to the R value is decreased at a wavelength (λ _ay), and the wavelength (λ _ay) as shown in The peak P _1y occurs at the located wavelength λ _ay + _{Δλ y} .

Alternatively, if the optical fiber 100 is refracted in direction 2 of Figure 7, the grating (g _a) and the x-axis spacing of the grating adjacent to the (Λ _x) is increased, and the y-axis direction interval (Λ _y) .

With this case, the decrease in the curve (C _x) peak (P _1x) occurs on the right side than the wavelength (λ _ax) and, y-axis direction interval (Λ _y) on the by the increase of the x-axis direction interval (Λ _x) In the curve (C _y ), the peak (P _1y ) will be generated on the left side of the wavelength (λ _ay ).

Referring to FIG. 8, the phenomenon occurring when the optical fiber 100 is refracted is summarized in the table below.

direction The curve (C _x ) The curve (C _y ) Direction 1 Decrease the x-axis direction spacing (Λ _x )
-> peak (P _1x ) occurs to the left of the reference wavelength Reduce the y-axis direction spacing (Λ _y )
-> peak (P _1y ) occurs to the left of the reference wavelength Direction 2 Increase in x-axis direction (Λ _x )
-> peak (P _1x ) occurs to the right of the reference wavelength Reduce the y-axis direction spacing (Λ _y )
-> peak (P _1y ) occurs to the left of the reference wavelength Direction 3 Increase in x-axis direction (Λ _x )
-> peak (P _1x ) occurs to the right of the reference wavelength Increase in y-direction spacing (Λ _y )
-> peak (P _1y ) occurs to the right of the reference wavelength Direction 4 Decrease the x-axis direction spacing (Λ _x )
-> peak (P _1x ) occurs to the left of the reference wavelength Increase in y-direction spacing (Λ _y )
-> peak (P _1y ) occurs to the right of the reference wavelength

It is possible to determine the direction in which the optical fiber 100 is refracted by analyzing how the wavelength spectrum curve (C _x , C _y ) changes.

Furthermore, the angle at which the optical fiber 100 is refracted can also be calculated.

Referring to FIG. 13 again, substituting Δλ _x in [Equation 1] in the curve C _x at the original position of the grating g _a in a state before the optical fiber 100 is refracted, g _a We can calculate how much) moves in the x-axis direction. Similarly, substituting Δλ _y into the above equation (1) in the curve C _y can calculate how far the grating g _a moves from the original position in the y-axis direction. Can know the displacement of the x-axis and y-axis of the grating (g _a), the grid (g _a) is rotated can be calculated the angle.

The optical fiber 100 according to the present embodiment can measure not only the refracted position but also the refracted direction and the angle using the single fiber. Therefore, it has a very good spatial characteristics compared to the optical fiber according to the prior art (see FIG. 3), which requires at least three strands to be used in order to measure the refracted direction and the angle thereof.

In addition, in the optical fiber 100 according to the present embodiment, since a plurality of gratings are disposed relatively tightly, there are almost no "dead zones" formed in the optical fiber according to the prior art.

In addition, according to the optical fiber 100 according to the present embodiment it was confirmed that the resolution (Resolution) of the detected refraction position can be significantly improved compared to the optical fiber according to the prior art.

Due to the excellent effect as described above, the optical fiber 100 according to the present embodiment can be usefully used as a sensor for sensing the refractive state of the equipment used in the narrow space, such as the endoscope equipment 150. 14 illustrates a sensor system according to one embodiment of the invention.

According to the present embodiment, the sensor system includes an optical fiber 100, a light source 200 for irradiating light to the optical fiber 100, and an optical analyzer 210 for analyzing the reflected light output from the optical fiber 100. .

Although it is possible to extract the reflected light polarized in the horizontal axis direction and the reflected light polarized in the vertical axis from the reflected light output from the optical fiber 100, in the present sensor system, the light output from the light source 200 is simplified to simplify the operation. Only incident light polarized in the horizontal axis and incident light polarized in the vertical axis by passing through the line 240 is extracted.

Accordingly, incident light polarized in the horizontal axis direction and incident light polarized in the vertical axis are incident on the optical fiber 100, and the polarized incident light is output as reflected light polarized in the horizontal axis direction and reflected light polarized in the vertical axis, respectively. The reflected light is sent to the optical analyzer 210 via the distributor 230. The optical analyzer 210 analyzes the wavelength spectrum of the collected reflected light polarized in the horizontal axis direction and the reflected light polarized in the vertical axis in real time to analyze the refractive state of the optical fiber 100.

Claims (8)

A cladding extending to a predetermined length,
A core extending along the longitudinal direction of the cladding within the cladding,
In the core, a plurality of gratings are formed that are different in refractive index from the core and are disposed along the longitudinal direction of the core to interfere with a path of light passing through the core.
Wherein the plurality of gratings are disposed at mutually different intervals,
When light is irradiated to the light inlet of the core, a portion of the light passing through the core is reflected by the plurality of gratings and output through the light inlet,
The reflected light output through the light inlet includes first and second reflected light polarized in different directions, and the first and second reflected light form a wavelength spectrum of different bands. Fiber. The method of claim 1,
And the spacing of the plurality of gratings increases or decreases in a constant function from the light inlet to the light outlet. The method of claim 1,
The first reflected light is reflected light polarized in the horizontal axis direction of the core,
The second reflected light is reflected light polarized in the vertical axis direction of the core,
The core has a density in the horizontal axis direction and a density in the vertical axis direction different from each other, so that a wavelength difference between the first reflected light and the second reflected light occurs. Claims 1 to 3 of the optical fiber of any one of;
A light source for irradiating light to the light inlet of the optical fiber;
An optical analyzer for analyzing a wavelength of reflected light output from the light inlet of the optical fiber,
The center of the core is disposed spaced apart from the center of refraction of the entire sensor using the optical fiber,
And when the sensor is refracted, the optical analyzer detects a refraction position and direction by detecting a change in a wavelength spectrum of the first and second reflected light. 5. The method of claim 4,
And the optical analyzer further detects a change in the wavelength spectrum of the first reflected light and the second reflected light to further detect an angle in the refracted direction. The method of claim 5,
And the optical analyzer further detects a curvature of refraction by detecting a change in a wavelength spectrum of the first reflected light and the second reflected light. A method of detecting the refractive state of the optical fiber using the sensor system of claim 4,
Irradiating light onto a light inlet of the optical fiber;
Collecting the first reflected light and the second reflected light output from the light inlet;
Calculating a wavelength spectrum of the first reflected light and the second reflected light;
Analyzing a change in the wavelength spectrum of the first and second reflected light;
And detecting a position and a direction in which the optical fiber is refracted by calculating a change amount when there is a change in the wavelength spectrum of the first reflected light and the second reflected light. The method of claim 7, wherein
And calculating an amount of change when there is a change in the wavelength spectrum of the first reflected light and the second reflected light to detect an angle and curvature in the direction in which the optical fiber is refracted.

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