KR100963169B1 - Bending sensor using rf signals and bend sensing method using the same - Google Patents

Abstract

A light source unit generating an RF modulated optical signal; A deformable part spaced apart from each other and having a reference optical fiber lattice and a sensing optical fiber lattice reflecting an optical signal of the light source unit and bent in both directions; An optical fiber spool providing dispersion according to wavelengths to the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating; And an optical detector configured to receive an optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating from the optical fiber spool, and convert the received optical signals into electrical signals. A bending sensor corresponding to the curvature of the electrical signal converted by the deformable portion and a bending measuring method using the same are disclosed. The bending sensor according to an embodiment of the present invention can be used in a distributed sensor because it can be transmitted over a long distance by using a low loss optical fiber, and can freely adjust the measurement sensitivity and measurement range by changing the frequency of the modulated RF signal. There is an advantage to that.

Cantilever, Cantilever, Bend Sensor, Fiber Optic Grating

Description

Bending sensor using RF signal and bending method using same {BENDING SENSOR USING RF SIGNALS AND BEND SENSING METHOD USING THE SAME}

The present invention relates to a bending sensor using an RF signal and a bending measurement method using the same. Specifically, an optical fiber grating and a sensing optical fiber provided in a deformation part such as a cantilever beam of an optical signal of an RF modulated broadband light source. The present invention relates to a bend sensor for transmitting a grid and calculating a curvature of a deformation part from an intensity of an electric signal converted from an optical signal reflected from both optical fiber gratings, and a bending measuring method using the same.

Optical fiber grating-based optical sensors have many advantages, such as no interference from electromagnetic waves, large bandwidths, and low loss, so that physical quantities can be measured at far distances. However, the conventional fiber grating-based sensor mainly requires expensive equipment such as a tunable laser, a tunable filter, or an optical spectrum analyzer because the sensor is mainly based on the wavelength change, and the measurement speed is difficult over kHz.

On the other hand, the intensity modulated optical fiber sensor has a simple structure that can lower the price, and has a relatively high measurement speed. Therefore, a method of converting the wavelength change of the optical fiber grating into the change of the intensity of the optical signal using a specially designed filter has been proposed (S. Kim et al., IEEE Photon. Technology. Lett. Vol. 13, 839-841, 2001). Measurements can only be made in a limited range of wavelength variations, and the effects of temperature and strain are mixed and cannot be separated.

The present invention for solving the problems of the prior art, by using a cantilever and an optical fiber grating and a sensing fiber grating, the RF-modulated optical signal is not affected by temperature changes from the signal reflected from the two optical fiber gratings It is an object of the present invention to provide a bending sensor based on an optical fiber grating using an RF signal capable of accurately measuring the degree of bending without using the same, and a bending measuring method using the same.

According to an exemplary embodiment, a bending sensor may include: a light source unit generating an RF modulated optical signal; A deformable part spaced apart from each other and having a reference optical fiber lattice and a sensing optical fiber lattice reflecting an optical signal of the light source unit and bent in both directions; An optical fiber spool providing dispersion according to wavelengths to the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating; And an optical detector configured to receive the optical signal reflected by the reference optical fiber lattice and the optical signal reflected by the sensing optical fiber lattice from the optical fiber spool, and convert the received optical signals into electrical signals. In this case, the intensity of the electrical signal converted by the light detector corresponds to the curvature of the deformable portion.

In addition, the bending measurement method according to an embodiment of the present invention, transmitting the RF-modulated optical signal, the deformable portion having a reference optical fiber grid and a sensing optical fiber grid spaced from each other and bent in both directions; Providing dispersion according to a wavelength to each of the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating; Converting the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating into an electrical signal; And calculating a curvature of the deformation part from the converted electrical signal.

The bending sensor and the bending measuring method according to an embodiment of the present invention, a low-cost semiconductor optical amplifier (SOA) and hundreds of MHz without using an expensive optical spectrum analyzer or a wavelength variable laser used in a conventional sensor The low-cost vibrator can be used to measure the curvature economically, and the optical fiber with low loss can be used for long distance measurement, and the measurement sensitivity and measuring range can be changed by changing the frequency of the modulated RF signal. There is an advantage that can be adjusted freely.

Hereinafter, with reference to the accompanying drawings looks at in detail with respect to the preferred embodiment of the present invention. In the following description of the present invention, the description of related known functions or configurations will be omitted when the description may unnecessarily obscure the subject matter of the present invention.

1 is a block diagram illustrating a bending sensor according to an embodiment of the present invention. Referring to FIG. 1, the bending sensor according to the embodiment includes a light source unit 110 including a broadband light source 111, a deformable unit 140 including a reference fiber grating 150, and a sensing fiber grating 155, and an optical fiber. It is configured to include a spool 160 and the light detector 170.

The broadband light source 111 of the light source unit 110 modulates the Spontaneous Emission (ASE) by the RF signal to generate an RF modulated optical signal. In one embodiment of the present invention, the broadband light source 111 may include a semiconductor optical amplifier (SOA), a reflective semiconductor optical amplifier (RSAA), or an anti-reflective coating on which the optical signal is output. Fabry-Perot laser and the like can be used.

In one embodiment of the present invention, the light source unit 110 may generate an RF modulated optical signal by modulating the current supplied to the broadband light source 111. In this case, the light source unit 110 may use a low-cost oscillator such as a voltage controlled oscillator (VCO) 112 as an RF signal source of the broadband light source 111, or a conventionally used RF generator 113 ) Can also be used. The RF signal generated by the VCO 112 or the RF generator 113 is added to the broadband light source 111 as a supply current in addition to the DC signal through a circuit 114 composed of an inductor and a capacitor.

In one embodiment of the present invention, the RF modulated light signal generated from the light source unit 110 is transmitted to the deforming unit 140 by the optical circulator 120. The deformation unit 140 includes a reference optical fiber grating 150 and a sensing optical fiber grating 155.

When the optical signal is transmitted, the reference optical fiber grating 150 and the sensing optical fiber grating 155 spaced apart from each other reflect only an optical signal having a wavelength corresponding to a unique Bragg wavelength among the transmitted optical signals. In one embodiment of the present invention, the wavelength of the optical signal reflected from the reference optical fiber grid 150 and the wavelength of the optical signal reflected from the sensing optical fiber grid 155 may be configured differently.

In the present specification, the wavelength gap between the optical signal reflected from the reference optical fiber grating 150 and the optical signal reflected from the sensing optical fiber grating 155 refers to the Bragg wavelength of the reference optical fiber grating 150 and the sensing optical fiber grating ( Mean the difference between the Bragg wavelengths of 155.

On the other hand, in the embodiment shown in Figure 1 deformable portion 140 is configured in the form of cantilever (cantilever). For example, the deformable portion 140 may be a cantilever beam formed of a thin metal plate. One end of the deformable part 140 is fixed by the fixing part 130, and the other end of the fixed one end is opposite in both directions (D1) based on the fixed one end as shown by a dotted line in FIG. Can be bent).

In the present invention, the signal corresponding to the curvature of the deformation unit 140 is output by using the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155, which is the light detector 170 Will be described later in detail.

The optical signal reflected by each of the reference optical fiber grating 150 and the sensing optical fiber grating 155 provided in the deformation unit 140 is transmitted to the optical circulator 120 again. The optical circulator 120 transmits the reflected optical signal to the single mode optical fiber spool 160.

The reference optical fiber grating 150 and the sensing optical fiber grating 155 reflect an optical signal of a single wavelength corresponding to the black wavelength of each optical fiber grating, and the reflected single wavelength optical signal passes through the optical fiber spool 160 to the wavelength. According to the dispersion. In one embodiment of the present invention, the optical fiber spool 16 may provide different dispersion values to the optical signal reflected by the reference optical fiber grid 150 and the optical signal reflected by the sensing optical fiber grid 155. Two optical signals having a dispersion according to the wavelength through the optical fiber spool 160 are transmitted to the optical detector 170.

The light detector 170 receives optical signals having dispersion according to the wavelength from the optical fiber spool 160. In this case, when the frequency of the optical signal RF-modulated by the broadband light source 111 is f, it is reflected by each of the reference optical fiber grating 150 and the sensing optical fiber grating 155, the optical detection unit 170 via the optical fiber spool 160 Intensity of the optical signal received at) may be expressed by Equation 1 below.

은 기준 광섬유격자(150)에서 반사된 광신호의 위상을 나타내며,

는 센싱 광섬유격자(155)에서 반사된 광신호의 위상을 나타내고,

은 기준 광섬유격자(150)에서 반사된 광신호의 세기를 나타내며,

는 센싱 광섬유격자(155)에서 반사된 광신호의 세기를 나타낸다. In Equation 1,

Represents the phase of the optical signal reflected from the reference fiber grating 150,

Represents the phase of the optical signal reflected from the sensing optical fiber grating 155,

Represents the intensity of the optical signal reflected from the reference fiber grating 150,

Denotes the intensity of the optical signal reflected from the sensing optical fiber grating 155.

및

는 실질적으로

으로 서로 동일할 수도 있다.In Equation 1, the wavelength gap between the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155 is about several nm, and the reflectances of the two optical fiber grids 150 and 155 are the same. The intensity of the optical signal

And

Is substantially

May be the same as each other.

Meanwhile, the light detector 170 may generate the RF signal in the form of an electrical signal by converting the received optical signals. In this case, the intensity of the electrical signal converted by the light detector 170 may be represented by the following equation (2).

는 광 검출부(170)에 의해 변환된 전기신호의 위상을 나타나며 아래 수학식 3에 의해 정의된다. In Equation 2

Denotes the phase of the electrical signal converted by the light detector 170 and is defined by Equation 3 below.

는 광 검출부(170)에 수신된 두 광신호의 위상차를 나타내며 아래 수학식 4에 의해 정의된다.Meanwhile, in Equation 2

Denotes a phase difference between two optical signals received by the optical detector 170 and is defined by Equation 4 below.

는 기준 광섬유격자(150)에서 반사되는 광신호와 센싱 광섬유격자(155)에서 반사되는 광신호 사이의 파장 간격을 나타낸다. In Equation 4, c is the speed of light in a vacuum, n is the refractive index of the optical fiber constituting the optical fiber grid, d is the distance between the reference optical fiber grid 150 and the sensing optical fiber grid 155, D is the optical fiber spool 160 ), L is the length of the optical fiber spool 160,

Denotes a wavelength interval between the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155.

는 기준 광섬유격자(150) 및 센싱 광섬유격자(155)에서 반사된 두 광신호가 서로 다른 위치에서 반사되기 때문에 일어나는 진행 경로의 차이로 인한 위상차를 나타낸다. In the right parenthesis of Equation 4, the front term

Denotes a phase difference due to a difference in a propagation path that occurs because two optical signals reflected from the reference optical fiber grid 150 and the sensing optical fiber grid 155 are reflected at different positions.

는 기준 광섬유격자(150) 및 센싱 광섬유격자(155)에서 반사된 두 광신호의 파장이 서로 다르기 때문에, 길이가 충분히 긴 단일모드 광섬유 스풀(160)을 지나는 동안 색분산으로 인한 광신호의 진행차로 인해 발생하는 위상차이다. Also, the rear term in the right parenthesis of Equation 4

Since the wavelengths of the two optical signals reflected from the reference optical fiber grating 150 and the sensing optical fiber grating 155 are different from each other, the optical signal due to chromatic dispersion during the long length of the single-mode optical fiber spool 160 is long. Due to phase difference.

에 따라 변화하며, 위상차

는 다시

값에 따라 변화하는 것을 확인할 수 있다. 그러므로, 광 검출부(170)에서 출력되는 전기신호의 세기 로부터

의 값을 산출할 수 있다.From the above Equations 2 and 4, the intensity of the electrical signal output from the light detector 170 is a phase difference

Changes according to the phase difference

Is back

You can see that it changes according to the value. Therefore, from the intensity of the electrical signal output from the light detector 170

Can be calculated.

는 온도와 스트레인(strain)에 따라 하기 수학식 5와 같이 변화하게 된다.On the other hand, the Bragg wavelength, which is the wavelength of the optical signal reflected from the reference optical fiber grid 150 or the sensing optical fiber grid 155

Is changed according to Equation 5 according to temperature and strain.

은 광섬유격자에 가해지는 스트레인의 크기이고,

는 광섬유의 온도에 따른 팽창 계수이며,

는 광섬유의 굴절률 변화를 나타내는 열광학 계수이고,

는 온도 변화량이다. In Equation 5, p _e Is the photoelastic coefficient of the optical fiber constituting each optical fiber grid, and is about 0.22 in the case of silica glass, the value varies slightly depending on the physical properties of the optical fiber. Also in Equation 5

Is the size of strain applied to the optical fiber grid,

Is the expansion coefficient according to the temperature of the optical fiber,

Is a thermo-optic coefficient representing the change in refractive index of the optical fiber,

Is the temperature change amount.

Therefore, the change of the wavelength of the optical signal reflected by each of the optical fiber grids 150 and 155 alone does not distinguish whether the effect is due to the temperature or the strain due to bending. In other words, in order to accurately measure the degree of bending from the Bragg wavelength change, the wavelength change due to temperature should be removed.

To this end, in the present invention, two optical fiber gratings 150 and 155 are used to measure the change in the distance between two Bragg wavelengths, which is proportional to the degree of bending deformation of the deformation unit 140 but independent of temperature. do. Therefore, the bending curvature of the deformation unit 140 can be accurately measured without being affected by the temperature change. Hereinafter, this will be described in detail with reference to FIG. 2.

은 하기 수학식 6으로 표현된다. 2A is a schematic diagram showing the case where the deformable portion 14 is bent. Referring to FIG. 2A, when a force is applied to the deformation part 140 in a vertical direction, the deformation part 140 is bent in the direction as shown in FIG. 2A. At this time, the strain applied to the deformation unit 140

Is expressed by the following equation (6).

는 변형부(140)의 곡률 반경을 나타낸다. 즉, 상기 수학식 6으로부터 변형부(140)에 인가되는 스트레인은 변형부(140)가 구부려진 곡률에 비례한다는 것을 알 수 있다. In Equation 6, l is the length of the portion where the deformation portion 140 is not fixed, T is the thickness of the deformation portion 140,

Denotes the radius of curvature of the deformation unit 140. That is, it can be seen that the strain applied to the deformation unit 140 from Equation 6 is proportional to the curvature of the deformation unit 140.

On the other hand, Figure 2b is a schematic diagram showing an approximation of the degree of deformation of the deformation unit 140 in a curve. In this case, the deformation curve of the deformation unit 140 may be expressed by Equation 7 below.

In Equation 7, z (x) represents the degree of deformation at a point away from the fixing part 13 when the end of the deformation part 14 having the length of the non-fixed part is bent by z. . On the other hand, the curvature at the point x away from the fixing portion 13 can be expressed by the following equation (8) by applying the equation (7).

The strain applied to the deformation unit 14 is proportional to the curvature as shown in Equation 6, and the curvature is determined by Equation 8. Thus, the strain applied to the deformable portion 14 is greatest at one end where the deformable portion 14 is fixed by the fixing portion 13, and zero at the opposite end.

Referring to FIG. 1, the reference optical fiber grating 150 is positioned adjacent to a portion where the deformation part 140 is fixed by the fixing part 130. Therefore, even if the deformation unit 140 is bent, the position of the reference optical fiber grid 150 does not change. On the other hand, since the sensing optical fiber grid 155 is located at the center of the deformation unit 140, the position of the sensing optical fiber grid 155 also changes as the deformation unit 140 is bent.

가 변하게 된다. Therefore, when the deformable part 140 is bent as shown by a dotted line in FIG. 1, the reference optical fiber grating 150 does not receive strain, but the sensing optical fiber grating 155 positioned in the middle of the deformable part 140 is in a tensioned direction. Under tension. Accordingly, the wavelength of the optical signal reflected from the sensing optical fiber grid 155 is shifted, and as a result, the wavelength gap between the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155.

Will change.

는 변화하지 않는다.However, when the deformation unit 140 does not bend and only changes in temperature, the Bragg wavelength of each of the reference optical fiber grating 150 and the sensing optical fiber grating 155 is changed, but both optical fiber gratings 150 and 155 are changed. Since the amount of change in the Bragg wavelength of is the same, the wavelength interval of the optical signal reflected from both optical fiber grids 150 and 155

Does not change.

는 온도 변화에 의해 영향을 받지 않으며, 상기 수학식 8과 같이 변형부(140)가 구부러지는 것으로 인해 센싱 광섬유격자(155)에 인가되는 스트레인에 의해서만 영향을 받게 된다. 그러므로, 광 검출부(170)에 의해 측정되는 신호의 세기로부터 변형부(140)의 곡률을 산출할 수 있다.Therefore, the wavelength gap between the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155

Is not affected by the temperature change, and is only affected by the strain applied to the sensing fiber grating 155 due to the bending of the deformation unit 140 as shown in Equation (8). Therefore, the curvature of the deformation unit 140 may be calculated from the intensity of the signal measured by the light detector 170.

에 따라 도시한 그래프이다. 본 발명가들은, 기준 광섬유격자(150)와 센싱 광섬유격자(155) 사이의 거리 d 가 20cm, 광섬유 스풀(160)의 분산값 D 가 17ps/km nm, 광섬유 스풀(160)의 길이 L 이 25km 인 구부림 센서에 대해서 계산을 수행하였다. 3 shows the intensity of the optical signal transmitted to the optical detector 170 in the bending sensor shown in FIG. 1, the optical signal reflected from the reference optical fiber grid 150 and the wavelength of the optical signal reflected from the sensing optical fiber grid 155. interval

It is a graph shown according to. The inventors have a distance d of 20 cm between the reference optical fiber grating 150 and the sensing optical fiber grating 155, the dispersion value D of the optical fiber spool 160 is 17 ps / km nm, and the length L of the optical fiber spool 160 is 25 km. The calculation was performed on the bending sensor.

가 0nm 에서 1nm 로 증가하면 정규화된(normalized) 전체 광신호의 세기는 0.5에서 0.1로 감소하는 것을 알 수 있다. 따라서, 전체 광신호의 세기로부터 파장 간격

를 산출할 수 있으며, 상기 수학식 5로부터 다시 센싱 광섬유격자(155)가 위치한 지점의 스트레인을 산출할 수 있다. 또한 산출된 스트레인을 상기 수학식 6에 대입하여 변형부(14)의 곡률을 산출할 수 있다.Referring to FIG. 3, when the modulation frequency f of the broadband light source 111 is 350 MHz, the wavelength interval

It can be seen that when increases from 0nm to 1nm, the intensity of the normalized total optical signal decreases from 0.5 to 0.1. Thus, the wavelength gap from the intensity of the entire optical signal

May be calculated, and the strain of the point where the sensing optical fiber grating 155 is located may be calculated again from Equation 5. In addition, the curvature of the deformation unit 14 may be calculated by substituting the calculated strain into Equation 6 above.

4 is a block diagram of a bending sensor according to another embodiment of the present invention. Referring to FIG. 4, in the embodiment illustrated in FIG. 4, the deformable part 140 is a reference fiber grating 150 positioned in the center of the bottom of the deformable part 140 and a sensing located in the center of the upper surface of the deformable part 140. An optical fiber grating 155 is provided. Except for the position of the reference optical fiber grating 150 in the deformation unit 140, the configuration and function of the light source unit 110, the optical fiber spool 160 and the light detector 170 is the same as the embodiment described above with reference to FIG. Therefore, detailed description is omitted.

In the embodiment shown in FIG. 4, when the deformable portion 140 is bent along both directions D1, the sensing optical fiber lattices 155 disposed on the upper surface of the deformable portion 140 may have a strain in the tensioning direction. Although the reference fiber grating 150 is located on the bottom surface of the deformable portion 140 is subjected to strain (compression) in the compression direction.

Therefore, in comparison with the embodiment shown in FIG. 1, since the strains applied to the reference optical fiber grating 150 and the sensing optical fiber grating 155 are in opposite directions, the deformation of the deformation unit 140 is performed. Accordingly, the amount of change in the wavelength gap between the optical signal reflected from the reference optical fiber grid 150 and the optical signal reflected from the sensing optical fiber grid 155 is doubled. Therefore, compared with the embodiment shown in FIG. 1, there is an advantage that an improved measurement accuracy can be obtained.

In the embodiment shown in FIG. 4, the reference optical fiber grating 150 is formed on the bottom of the deformation part 140 and the sensing optical fiber grating 155 is formed on the top surface of the deformation part 140. In another embodiment of FIG. 4, the positions of the reference optical fiber grating 150 and the sensing optical fiber grating 155 may be opposite to those shown in FIG. 4.

5 is a block diagram illustrating a bending sensor according to another embodiment of the present invention. Referring to FIG. 5, in the bending sensor according to the embodiment, the light source unit 110 includes a broadband light source 111 and an external light modulator 115. Except for the configuration of the light source unit 110, the configuration and function of the deformation unit 140, the optical fiber spool 160, and the light detection unit 170 is the same as the above-described embodiment with reference to Figure 1 will not be described in detail.

1 and 4 described above, RF signals are directly generated by RF modulation of the optical signal of the broadband light source 111. However, when using a high-power Erbium-Doped Fiber Amplifier (EDFA) or the like for use as a long-range sensor, it is difficult to directly RF modulate the optical signal of the broadband light source 111.

Accordingly, in the above embodiment, as shown in FIG. 5, the light source unit 110 is configured to include a broadband light source 111 and an external light modulator 115. The optical signal generated by the broadband light source 111 is RF-modulated while passing through the external optical modulator 115, and the RF-modulated optical signal is output from the light source unit 110 and transmitted to the optical circulator 120.

FIG. 6 is a graph illustrating the magnitude of an RF signal output from the light detector 170 according to the curvature in the bending sensor according to the exemplary embodiment of the present invention shown in FIG. 4. At this time, the distance d between the reference optical fiber grating 150 and the sensing optical fiber grating 155 is 48 cm, and when there is no bending, the difference between the two Brack wavelengths was about 2.7 nm. Referring to FIG. 6, a square (□) on the graph indicates curvature, and a circle (○) on the graph indicates wavelength spacing. It can be seen that the RF signal strength decreases when the curvature increases from 0 m ^{- 1} to 2 m ^{- 1} .

Meanwhile, in the graph of FIG. 6, the negative curvature corresponds to the opposite direction of bending.

The bending sensor according to an embodiment of the present invention described above can be used for a distributed sensor because it can be transmitted over a long distance by using a low loss optical fiber, and the measurement sensitivity and measurement range can be changed by changing the frequency of the modulated RF signal. There is an advantage that can be adjusted freely.

Although the present invention described above has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. However, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a block diagram of a bending sensor according to an embodiment of the present invention.

2A and 2B are schematic diagrams illustrating a principle of obtaining curvature from a deformation curve of a deformation part in the bending sensor illustrated in FIG. 1 and a relationship between curvature and strain.

3 is a graph showing the results of experiments using the bending sensor shown in FIG. 1.

4 is a block diagram of a bending sensor according to another embodiment of the present invention.

5 is a block diagram of a bending sensor according to another embodiment of the present invention.

FIG. 6 is a graph illustrating an experiment result using the bending sensor illustrated in FIG. 4.

Claims (12)

A light source unit generating an RF modulated optical signal; A deformable part spaced apart from each other and having a reference optical fiber lattice and a sensing optical fiber lattice reflecting an optical signal of the light source unit and bent in both directions; An optical fiber spool providing dispersion according to wavelengths to the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating; And A light detector for receiving the optical signal reflected by the reference optical fiber lattices and the optical signal reflected by the sensing optical fiber lattices from the optical fiber spool, and converting the received optical signals into electrical signals; The strength of the electrical signal converted by the light detector, the bending sensor, characterized in that corresponding to the curvature of the deformation. The method of claim 1, And the reference optical fiber grating and the sensing optical fiber grating reflect optical signals having different wavelengths from among optical signals of the light source unit. The method of claim 1, The deformable portion, A metal plate having one end fixed and the other end bent in both directions; A reference optical fiber grid positioned adjacent said one end of said metal plate; And And a sensing optical fiber lattice spaced apart from the one end of the metal plate. The method of claim 1, The deformable portion, A metal plate having one end fixed and the other end bent in both directions; A reference optical fiber lattice positioned at one end of the metal plate and formed on one side of the metal plate; And And a sensing optical fiber grating positioned on the other side of the metal plate and formed on the other side of the metal plate. The method of claim 1, The optical fiber spool, The bending sensor according to claim 1, wherein the bending signal is provided with different dispersion values to the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating. The method of claim 1, The light source unit, A bending sensor comprising a semiconductor optical amplifier, a reflective semiconductor optical amplifier, or a Fabry-Perot laser on which a surface on which an optical signal is output is antireflectively coated. The method of claim 1, The light source unit, It includes a broadband light source for generating an optical signal, Bending sensor, characterized in that for generating an RF-modulated optical signal by modulating the supply current of the broadband light source. The method of claim 7, wherein The light source unit, And a voltage controlled oscillator (VCO) or an RF generator for providing an RF signal to the broadband light source. The method of claim 1, The light source unit, A broadband light source generating an optical signal; And And an external optical modulator for RF modulating the optical signal of the broadband light source. Transmitting the RF modulated optical signal to a deformable part having a reference optical fiber grid and a sensing optical fiber grid spaced from each other and bent in both directions; Providing dispersion according to a wavelength to each of the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating; Converting the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating into an electrical signal; And And calculating a curvature of the deformable part from the converted electric signal. The method of claim 10, Providing the dispersion according to the wavelength, And providing different dispersion values to the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating. The method of claim 10, Calculating the curvature of the deformation portion, Calculating a wavelength interval between the optical signal reflected by the reference optical fiber grating and the optical signal reflected by the sensing optical fiber grating from the intensity of the converted electrical signal; Calculating a strain value applied to the sensing optical fiber grating from the wavelength interval calculated in the step; And And calculating a curvature of the deformation part from the strain value applied to the sensing optical fiber grating.

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