JPH08201439A - Optical fiber sensor - Google Patents

Abstract

PURPOSE: To improve the measurement accuracy of an optical fiber sensor by reducing the fluctuation of the propagating loss, etc., of the sensor caused by the temperature dependency of the sensor. CONSTITUTION: An optical fiber sensor is provided with a light propagating optical fiber 3 which introduces the light emitted from a light source 1 to a sensor section 12, optical element 6 which is provided in the section 12 and changes the polarized state of the light in accordance with the fluctuation of a quantity to be measured, light receiving optical fibers 10 and 11 which introduce the light from the sensor section 12 to detecting sections 13 and 14, and arithmetic means 17 which calculates the quantity to be measured based on the output signals of the light detected at the detecting sections 13 and 14. The core diameter and numerical aperture of the light propagating optical fiber 3 are made smaller than those of the light receiving optical fibers 13 and 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber sensor for converting a physical quantity such as voltage or current into a change quantity of light for measurement.

[0002]

2. Description of the Related Art Optical fiber sensors for converting physical quantities such as voltage and current into light and measuring them are expected to be put to practical use in various fields because of their high electric insulation and resistance to electromagnetic induction interference. . Specifically, (1) an optical fiber voltage sensor utilizing the fact that when an electric field is applied to a piezoelectric crystal, a refractive index change proportional to the electric field strength occurs (Pockels effect), (2) linear polarization in a magnetic body An optical fiber current sensor that utilizes the fact that the plane of polarization rotates (Faraday effect) when a magnetic field exists in the same direction as the traveling direction of the wave when the wave passes, (3) The refractive index changes when strain occurs in the elastic body Then, there is an optical fiber pressure sensor that utilizes the fact that birefringence occurs (photoelastic effect). As a typical optical fiber sensor, there is an optical fiber magnetic sensor shown in Fig. 5.21 of "optical fiber sensor" p145 to p146 issued by Ohmsha Co., Ltd. on July 30, 1986. This optical fiber magnetic sensor uses the Faraday effect. Light emitted from a light source (LED) is guided to a sensor section of the optical fiber magnetic sensor using a multimode fiber, and a linearly polarized wave is formed by a polarizer, and then ZnSe is used. Inside the Faraday element made of a magnetic material such as, the plane of polarization is rotated according to the applied magnetic field. The rotation angle θf at this time is converted into light intensity by the analyzer and sent to the light receiving element (PD) by the multimode fiber. Now, if the relative angle between the polarizer and the analyzer is 45 (deg), the power P of the light on the light receiving element surface can be expressed by the following equation (1).

[0003]

## EQU1 ## P = P0 (1 + sin θf) (1) where P0 is the light intensity when no magnetic field is generated. The applied magnetic field can be found by measuring the photoelectrically converted signal from the above equation.

However, the following various problems have been pointed out in putting the optical fiber sensor thus constructed into practical use. First, the optical fiber used in the sensor configured as described above is often a multimode optical fiber having a large core diameter because it is desired to maximize the amount of light. The core diameter is generally about 100 to 200 μm. However, when an optical fiber with a large core diameter is used as the optical fiber for light transmission, it becomes difficult to design an optical system that can sufficiently narrow the beam diameter on the light transmission side (φ1 mm or less). In addition, not only the coupling loss between the light-transmitting side and the light-receiving side becomes worse, but also the coupling state (beam coupling) changes due to temperature change, which causes a measurement error.

For example, when a light source has a wavelength of 850 nm, a light-transmitting / receiving optical fiber has a core diameter of 100 μm, an NA of 0.28, and an optical path length of 35 mm, the light propagating in space is designed. The diameter of the beam is about 1.9 mm, and the diameter of the light beam at the end face of the receiving optical fiber is about 160 μm. Of course, various configurations can be considered for the beam diameter and the like depending on the selection of the lens, but in reality, many options cannot be expected because the sensor is desired to be as small as possible. Therefore, it is not possible to receive all of the light beam,
As a result, the light coupling efficiency becomes poor. Further, if the coupling state of light changes due to the temperature change, it may lead to a measurement error.

Secondly, when the output fluctuation of the light source, the optical connector loss, and the transmission loss of the optical fiber fluctuate, the output signal drifts, leading to a measurement error. In order to prevent such drift, various drift compensation methods have been proposed.

As an example of the drift compensation method, 1986
"Optical fiber sensor" issued by Ohmsha Co., Ltd. July 30, p131
There is a method shown in Fig. 5.4 (c) of p133. This method measures the two orthogonal polarization components output from the analyzer and divides them by the signal processing unit to change the output of the light source.
The output fluctuation of the optical sensor unit is removed. This method can compensate for the drift of the light source, but when actually laying the sensor outdoors in a place where it is desired to measure, it becomes necessary to connect it via an optical connector.
In this case, an accurate measurement cannot be performed because the output signal drifts at the connector connecting portion.

Thirdly, the temperature dependence of the sensor is increased. This temperature dependence is caused by the following reasons.
As a method for fixing optical components such as a polarizer, a Faraday element, and an analyzer on the sensor base, a method using adhesion is generally used. The reason why the bonding method is used is to prevent mechanical stress from being applied to the optical component, and the adhesive used for bonding the optical component is often made of epoxy resin. In addition, the light-transmitting collimator for collimating the light from the optical fiber, the light-receiving collimator for receiving the beam, and the sensor base for arranging the optical parts are made of aluminum or stainless steel with emphasis on the strength of the material. It is used.

Although the optical fiber sensor as described above has a reasonable measurement accuracy at the laboratory level, in the environment where the user actually wants to measure, for example, outdoors, the output error with respect to the temperature change is as described above. Becomes large, which makes the measuring instrument unreliable.

Here, the reason why the output characteristic of the conventional optical fiber sensor depends on the temperature change will be described. FIG. 7 shows an apparatus for investigating the influence of an adhesive on an optical component, and shows an optical element evaluation apparatus disclosed in Japanese Patent Laid-Open No. 188038/1992. FIG. 8 shows a sample 120 for investigating the influence of the adhesive on the optical component. Figure 7
Sample 120 shown in Fig. 7 is prepared by bonding quartz glass 121, which is often used as an optical component, and stainless steel plate 122, which is often used as a sensor base, with an epoxy adhesive 123, and is shown in Fig. 7. The temperature characteristics are evaluated using an optical element evaluation device. Since the optical element evaluation device shown in FIG. 7 is publicly known, detailed description thereof will be omitted.
101, LED102, lens 103, polarizer 104, analyzer 10
7, lens 108, imaging device 109, monitor TV 110, A
/ D converter 111, arithmetic and control unit 112, memory unit 11
3, 114, a printer 115, and a fine movement device 116. The sample 120 shown in FIG. 8 is placed on the fine movement device 116 for evaluation.

As a result of the evaluation, it was found that the quartz glass was distorted due to the curing shrinkage of the adhesive even in the normal temperature state where the temperature was not changed, and it was confirmed that the point where the distortion was caused was widened when the temperature was further changed. did it. This means that the polarization state of light is changed only by the temperature change, which leads to an output error of the sensor.

[0012]

As described above, various problems have occurred in putting the optical fiber sensor into practical use, and when the optical fiber sensor is constructed, the core is tried to maximize the amount of light. Even if an optical fiber with a large diameter is used, the coupling efficiency of the light will eventually deteriorate, the drift of the optical connector cannot be compensated, and the coupling between the light on the sending side and the light on the receiving side due to temperature changes. Changes the state of the optical components, which leads to measurement errors, and when fixing the optical components to the sensor base, the use of epoxy resin adhesive causes distortion in the optical components and changes the polarization state. Due to such problems, it was not possible to obtain sufficient measurement accuracy. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide an optical fiber sensor that has good light coupling efficiency and that can perform accurate measurement even with temperature changes.

[0013]

In order to solve the above problems, in the invention described in claim 1, the optical fiber for light transmission for guiding the light emitted from the light source to the sensor section and the sensor section are provided. An optical element that changes the polarization state of light according to changes in the quantity to be measured, an optical fiber for receiving light that guides light from the sensor section to the detection section, and a quantity to be measured based on the output signal of the light detected by the detection section. In an optical fiber sensor having a calculating means for calculating, the values of the core diameter and numerical aperture of the light-transmitting optical fiber are set to be smaller than the core diameter and numerical aperture of the light-receiving optical fiber. There is.

According to the second aspect of the present invention, in the optical fiber sensor, the sine value of the incident angle when the light emitted from the light source is incident on the optical fiber for light transmission is the value of the optical fiber for light transmission. It is characterized in that it is configured such that the incident light is set smaller than the numerical aperture value.

According to a third aspect of the present invention, in the above optical fiber sensor, the sine value of the incident angle when light is incident on the light receiving optical fiber from the sensor portion is the numerical aperture of the light receiving optical fiber. It is characterized in that it is configured to be set smaller than the above and incident.

According to another aspect of the present invention, a light-transmitting optical fiber that guides the measurement light having the first wavelength and the reference light having the second wavelength emitted from the light source means to the sensor section independently of each other. Means, an optical element provided in the sensor section for changing the polarization state of the measurement light in response to a change in the quantity to be measured, and the measurement light after passing through the optical element provided in the sensor section and the optical fiber means for transmitting light. Separation means for separating the separated reference light into first and second polarized light, respectively, light-receiving optical fiber means for individually guiding the first and second polarized light to the detection section, and detection by the detection section And a calculating means for calculating the measured quantity based on the respective output signals of the first and second polarized lights.

According to the fifth aspect of the invention, a light-transmitting optical fiber that guides the light emitted from the light source to the sensor section, and the polarization state of the light that is provided in the sensor section and changes according to the change in the quantity to be measured. An optical component including an optical element, a light-receiving optical fiber that guides light from the sensor unit to the detection unit, and a calculation unit that calculates a change in the measured amount based on an output signal of the light detected by the detection unit. In the provided optical fiber sensor, the sensor unit is characterized in that the optical component is bonded and fixed to the base with a silicone adhesive.

According to a sixth aspect of the present invention, in the above-mentioned optical fiber sensor, the sensor portion has the optical component on a base made of ceramics having a thermal expansion coefficient close to that of quartz glass forming the optical component. It is characterized by being arranged.

[0019]

According to the first aspect of the present invention, the values of the core diameter and the numerical aperture of the light transmitting optical fiber are made smaller than the values of the core diameter and the numerical aperture of the light receiving optical fiber. It is possible to improve the coupling between the light beams on the light receiving side and the light receiving side. At this time, it is desirable that the numerical aperture of the optical fiber for light transmission is as small as possible because it allows a margin when designing the optical system. As a result, the design of the optical system is facilitated and a degree of freedom is created. Therefore, it is possible to design so that the transmitted beam is entirely received by the end face of the receiving optical fiber. Also,
With such a design, even if the coupling between the light-transmitting side beam and the light-receiving side beam changes due to the temperature change, it is possible to sufficiently cope with the change.

According to the second and third aspects of the invention, the value of the sine of the incident angle when the light emitted from the light source is incident on the light transmitting optical fiber is defined as the aperture of the light transmitting optical fiber. It is configured so that the incident light is set smaller than the numerical value, and the sine value of the incident angle when the light is incident on the receiving optical fiber from the sensor unit is smaller than the numerical aperture of the receiving optical fiber. Since the incident light is set to be small, it is possible to reduce the change in the propagation loss caused by the temperature change in the optical fiber itself.

According to the fourth aspect of the invention, it is possible to compensate the output fluctuation in the connector connecting portion of the light receiving optical fiber, that is, the drift in the connector connecting portion of the light receiving optical fiber.

According to the fifth aspect of the present invention, by using a soft silicone adhesive even after curing as an adhesive used for adhering the optical component to the base, the optical component cures and shrinks. It is possible to prevent the influence of distortion due to.

According to the sixth aspect of the present invention, the material used for the base on which the optical component is arranged is made of free-cutting ceramics having a thermal expansion coefficient close to that of silica glass, which is widely used for optical components. It is possible to reduce the difference between the coefficients as much as possible, and it is possible to prevent the optical component from being cracked or distorted due to stress due to temperature change.

[0024]

EXAMPLE An example of the optical fiber sensor of the present invention will be described below. (First Embodiment) FIG. 1 shows a first embodiment of the optical fiber sensor of the present invention.
It is a figure for explaining an example, and is a schematic structure figure of an optical fiber magnetic field sensor for measuring the size of a magnetic field using a Faraday effect.

The light emitted from the light source 1 is guided to the collimator lens 18 by the transmission optical fiber 2 and shaped into a parallel beam. A spherical lens 19 is used to collimate the parallel beam, and the incident aperture of the light beam is numerical aperture (NA).
The NA of the incident light will be described later in detail) so that it is smaller than the numerical aperture (hereinafter referred to as NA) of the light transmitting optical fiber 3 and is incident on the light transmitting optical fiber 3.

Then, the light beam is guided to the sensor section 12 through the light-transmitting optical fiber 3, shaped into a parallel beam by the collimator 4, a polarizer 5 (this polarizer 5 can be omitted), and a Faraday element. After passing through 6, the light is separated into two polarized waves (P wave and S wave) orthogonal to each other by the analyzer 7, and is incident on the light receiving optical fibers 10 and 11. The polarized light separated in this way is detected by the photodiodes 10 and 11
The light is guided to 13 and 14 and is received by the photodiodes 13 and 14, converted into light intensities Is and Ip and output. After the outputs of the photodiodes 13 and 14 are amplified by the amplifiers 15 and 16, the signal processing device 17 calculates and outputs the magnetic field strength.

When the magnetic field H is applied to the Faraday element 6, the polarization plane of the linearly polarized light after passing through the polarizer 5 is θ.
Just rotate. The Farade rotation angle θ at this time is as shown in the following equation (2).

[0028]

## EQU2 ## θ = VHL is given by (2). Where V is the Verdet constant of the Faraday element,
H is the strength of the magnetic field in the optical path direction, and L is the Faraday element length. By measuring the light intensities of P wave and S wave, respectively, the Farade rotation angle θ can be calculated as shown in the following equation (3).

[0029]

(Equation 3) Is asked. Since θ is proportional to the magnetic field H as shown in equation (2),
By calculating θ from the equation (3), the magnitude of the magnetic field H applied to the optical fiber magnetic field sensor can be known.

In the first embodiment, as a configuration for making the NA of the incident light entering the transmission optical fiber 2 from the light source 1 smaller than the NA of the light transmission optical fiber 3, specifically, FIG. The configuration shown is applied. The light emitted from the light source 1 and carried by the transmission optical fiber 2 is guided to the collimator lens 18 and shaped into a parallel beam, which is narrowed down using the spherical lens 19 and is incident on the light transmission optical fiber 3. Let Assuming that the refractive index of the core is n1 and the refractive index of the clad is n2, the NA of the optical fiber is as shown in the following equation (4).

[0031]

[Equation 4] Is defined as

As shown schematically in FIG. 3, the configuration of FIG.
When the light beam from the spherical lens 19 is incident on the center of the end face of the light transmitting optical fiber 3 at the incident angle θ, the value of the sine (sin θ) of the incident angle θ (the sine value of the incident angle θ is incident The NA of the light is referred to as the NA of the light. The NA of the light transmitting optical fiber 3 is defined by the above formula (4) (the refractive index of the core 20 of the light transmitting optical fiber 3 is n1 as shown in FIG. The spherical lens 19 is set so that its refractive index becomes smaller than n2). With such a configuration, the light source 1
Therefore, the amount of light incident on the light transmitting optical fiber 3 can be made extremely large.

In addition to this structure, in the optical fiber sensor of the first embodiment, the core diameter and NA of the light transmitting optical fiber 3 are smaller than the core diameter and NA of the light receiving optical fibers 10 and 11. Is configured as follows. Specifically, as an example, a light-transmitting optical fiber having a core diameter of 50 μm and NA = 0.18, and a light-receiving optical fiber having a core diameter of 200 μm and NA =
I chose the one of 0.5. Using this combination of light-transmitting and light-receiving optical fibers, the diameter of the light beam is approximately 1.3 mm, the beam diameter at the end face of the light-receiving optical fiber is 57 μm, and the NA of the incident light entering the light-receiving optical fiber is 0.23. Thus, the focal length of the light receiving collimator lens is set. In this case as well, if it is schematically shown, the spherical lens 19 of FIG. 3 corresponds to a collimator lens for light reception, similar to that shown in FIG.
The light transmitting optical fiber 3 shown in FIG. 3 is the light receiving optical fiber 1.
Equivalent to 0 and 11.

By designing the optical system in this way, the NA of the light beam incident on the receiving optical fiber (NA = 0.23)
On the other hand, since the NA (NA = 0.5) of the optical fiber for receiving light can be made large enough, even if the coupling state of the light-transmitting side and the light-receiving side changes a little, the light beam from the light-transmitting side has a margin on the light-receiving side. It is possible to receive light and thus improve the light coupling efficiency.

As described above, according to the first embodiment,
Even if the coupling state changes due to temperature changes or the like in the environment in which the light-receiving optical fiber is arranged, the propagation loss fluctuation can be prevented. (Second Embodiment) A second embodiment of the present invention will be described below.

FIG. 4 is a diagram for explaining an optical fiber sensor according to a second embodiment of the present invention, and is a schematic configuration diagram of an optical fiber magnetic field sensor for measuring the magnitude of a magnetic field by using the Farade effect. Is.

In the second embodiment, the light emitted from the light source 31 (wavelength λ1: LED of 850 nm, for example) used as the measurement light is transmitted through the optical fiber 33 for light transmission to the sensor section 55.
The collimator 34 to form a parallel beam,
35 (this polarizer 35 can be omitted), a Faraday element 36, and two polarized waves (P
Wave and S wave), and guides them to the light receiving optical fibers 42 and 43. On the other hand, the light emitted from the light source 32 (wavelength λ2: LED having a wavelength of 650 nm, for example) used as the reference light is guided to the sensor unit 55 via the optical fiber 41 for light transmission, and the two polarized waves (P Wave, S wave) and guides them to the optical fibers 42 and 43 for receiving light.

The light propagating in the light receiving optical fiber 42 is guided to the dichroic mirror 47 via the optical fiber 44 connected through the connector 46, and is separated into S polarized light of wavelength λ1 and P polarized light of wavelength λ2. , Photodiodes 49,5
The light is received at 0, converted into light intensities I1s and I2p, and output. Similarly, the light propagating in the light receiving optical fiber 43 is guided to the dichroic mirror 48 via the optical fiber 45 connected via the connector 46, and is separated into P polarized light of wavelength λ1 and S polarized light of wavelength λ2. , The light intensity I1p, I2s received by the photodiodes 51, 52
Is converted to and output. And the photodiode 49,
Based on the outputs of 50, 51 and 52, the strength of the magnetic field is calculated and output in the signal processing device 53.

When the magnetic field H is applied to the Faraday element 36, the polarization plane of the linearly polarized light after passing through the analyzer 37 is θ.
Just rotate. As in the first embodiment, the Farade rotation angle θ is given by the equation (2), and the Farade rotation angle θ is calculated by the following equation (5) by measuring the light intensities of the P wave and the S wave, respectively. The street

[0040]

(Equation 5) Is asked. Since θ is proportional to the magnetic field H, from the equation (5), θ
The magnitude of the magnetic field H can be known by finding

With the above-mentioned structure, the disturbance (temperature / temperature) generated in the light-receiving optical fibers 42, 43 and the connector 46 is generated.
It is possible to compensate for light intensity fluctuation caused by pressure, vibration, etc.). For example, if the disturbance generated in the light receiving optical fiber 42 is f1, and the disturbance generated in the light receiving optical fiber 43 is f2,

[0042]

(Equation 6)

The disturbances f1 and f2 can be canceled as in the equation (6). The output variation that occurs in the preceding stage of the receiving optical fiber, such as the output variation of the light source and the propagation loss of the transmitting optical fiber, can be already canceled by separating and measuring the P wave and S wave. By using the drift compensation configuration shown in the example, more accurate measurement is possible. (Third Embodiment) Next, referring to FIG. 5, a third embodiment of the present invention will be described.
Examples will be described. FIG. 5 is a diagram showing the configuration of the collimator in the optical fiber sensor, which is characterized by the assembling method. The collimator is used to transmit the light propagating through the optical fiber through the lens into a parallel beam. The light transmitting collimator according to the third embodiment is the light transmitting optical fiber 60, Ferrule 61, lens 63 used for centering the fiber, and these optical fibers for light transmission
It is composed of a collimator body (base) 62 for fixing the lens 60 and the lens 63 with a silicone adhesive 64.

In such a structure, the collimator body (base) 62 is a quartz glass (eg BK7 glass: thermal expansion coefficient 7.4 × 10 ⁻ ) which is often used as an optical component (lens, polarizer, Farade element, analyzer, etc.). ⁶ (/ ° C.) relatively close machinable thermal expansion coefficient) (machinable) ceramics (e.g., trade name of Sumitomo Metals ho ton ceramics Co. "Photoveel" (thermal expansion coefficient of 8.5 × 10 ^-6 (/ ℃)
): Fluorine phlogopite, a composite mica ceramic produced by a melting method in which zirconia microcrystals are uniformly deposited, or the like), using glass as a matrix. Furthermore, as an adhesive to bond the lens 63 to the collimator body 62, a silicone adhesive that is soft even after curing (for example, hardness 35 (JIS A standard), tensile strength 30 (Kgf / cm
² ) Degree) 64 is used.

As shown in FIG. 6, the material of the sensor base 65 of the sensor portions 12 and 55 shown in the first and second embodiments is also free-cutting similarly to the structure shown in the third embodiment. In addition to using ceramics, polarizers 5,3
If the silicon-based adhesive 64 is used also when fixing optical components such as 5, Faraday elements 6, 36, and analyzers 7, 37 to the sensor base 65, distortion caused in the optical components due to the difference in thermal expansion coefficient. Can be reduced.

Although the first to third embodiments have been described above, it is needless to say that the embodiments are combined to form an optical fiber sensor, and the present invention is variously modified without departing from the scope of the invention. It is possible.

[0047]

As described above, according to the present invention,
Since it is possible to reduce the fluctuation of the propagation loss caused by the temperature change applied to the light transmitting / receiving optical fiber, it is possible to provide an optical fiber sensor having good temperature characteristics and good measurement accuracy. Further, it is possible to compensate for the drift of the output of the light source and the temperature fluctuation of the connector connection loss, and it is possible to eliminate the fluctuation of the output caused by the distortion of the optical components due to the temperature fluctuation. A good fiber optic sensor can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of an optical fiber sensor of the present invention.

FIG. 2 is a schematic configuration diagram showing a main part of a first embodiment of an optical fiber sensor of the present invention.

FIG. 3 is a schematic diagram showing a main part of a first embodiment of the optical fiber sensor of the present invention.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the optical fiber sensor of the present invention.

FIG. 5 is a schematic configuration diagram showing a main part of a third embodiment of an optical fiber sensor of the present invention.

FIG. 6 is a schematic configuration diagram showing a main part of a third embodiment of an optical fiber sensor of the present invention.

FIG. 7 is a schematic configuration diagram of an optical element evaluation apparatus.

8 is a schematic diagram showing a sample evaluated by the optical element evaluation apparatus shown in FIG.

[Explanation of symbols]

 1 Light Source 2 Transmission Optical Fiber 3 Transmission Optical Fiber 4 Transmission Collimator 5 Polarizer 6 Farade Element 7 Analyzer 8 P-wave Receiving Collimator 9 S-wave Receiving Collimator 10 P-wave Receiving Optical Fiber 11 S-wave Receiving Light Fibers 13 and 14 Photodiodes 17 Signal processing device 18 Collimator lens 19 Spherical lens 31 Light source (wavelength λ1) 32 Light source (wavelength λ2) 33 Optical fiber for transmitting light 34 Collimator for transmitting light 35 Polarizer 36 Farade element 37 Analyzer 38 Transmitting Light collimator 39 Light receiving collimator 40 Light receiving collimator 41 Light transmitting optical fiber 42, 43, 44, 45 Light receiving optical fiber 47, 48 Dichroic mirror 49, 50, 51, 52 Photodiode 53 Signal processor 60 Optical fiber 61 Ferrule 62 Collimator body 63 Lens 64 Silicone adhesive

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G01R 33/032 9307-2G G02B 6/00

Claims (6)

[Claims] 1. An optical fiber for transmitting light, which guides light emitted from a light source to a sensor section, an optical element which is provided in the sensor section and changes a polarization state of light according to a change in an amount to be measured, and the sensor section. In the optical fiber sensor including a light-receiving optical fiber that guides light from the detector to the detector, and a calculating unit that calculates the measured amount based on the output signal of the light detected by the detector, An optical fiber sensor, wherein the values of the core diameter and the numerical aperture of the use optical fiber are set to be smaller than the values of the core diameter and the numerical aperture of the light receiving optical fiber. 2. A light-transmitting optical fiber for guiding light emitted from a light source to a sensor section, an optical element provided in the sensor section for changing the polarization state of light according to a change in a measured amount, and the sensor section. From the light source, in an optical fiber sensor including a light receiving optical fiber that guides light from the detector to a detection unit, and a calculation unit that calculates the measured amount based on the output signal of the light detected by the detection unit. The sine value of the incident angle when the emitted light is incident on the light transmitting optical fiber is set to be smaller than the numerical aperture value of the light transmitting optical fiber, and the light is incident. And an optical fiber sensor. 3. A light-transmitting optical fiber for guiding light emitted from a light source to a sensor section, an optical element provided in the sensor section for changing the polarization state of light according to a change in a measured amount, and the sensor section. An optical fiber sensor including a light-receiving optical fiber that guides light from a detector to a detection unit, and a calculation unit that calculates the measured amount based on an output signal of the light detected by the detection unit. From the sine value of the incident angle when the light is incident on the receiving optical fiber from,
An optical fiber sensor, wherein the optical fiber sensor is configured to be set smaller than a numerical aperture value of the light receiving optical fiber so as to be incident. 4. A light-transmitting optical fiber means for independently guiding a measuring light having a first wavelength and a reference light having a second wavelength, which are emitted from a light source means, to a sensor section, and provided in the sensor section. An optical element that changes the polarization state of the measurement light according to a change in the measured amount; and the measurement light that has been provided in the sensor unit and has passed through the optical element and is guided from the optical fiber means for light transmission. Separation means for separating the reference light into first and second polarized lights respectively;
And the light receiving optical fiber means for independently guiding the second polarized light to the detecting section, and the measured quantity is calculated based on the respective output signals of the first and second polarized light detected by the detecting section. An optical fiber sensor, comprising: 5. An optical fiber for transmitting light, which guides light emitted from a light source to a sensor section, and an optical component including an optical element, which is provided in the sensor section and changes a polarization state of light according to a change in an amount to be measured. An optical fiber sensor including a light-receiving optical fiber that guides light from the sensor unit to a detection unit, and a calculation unit that calculates the measured amount based on an output signal of the light detected by the detection unit. The optical fiber sensor is characterized in that the sensor unit is configured by adhering and fixing the optical component to a base with a silicone adhesive. 6. An optical component for transmitting light, which guides light emitted from a light source to a sensor section, and an optical component including an optical element which is provided in the sensor section and changes a polarization state of light according to a change in an amount to be measured. An optical fiber sensor including a light-receiving optical fiber that guides light from the sensor unit to a detection unit, and a calculation unit that calculates the measured amount based on an output signal of the light detected by the detection unit. The optical fiber sensor is characterized in that the sensor part is formed by arranging the optical part on a base made of ceramics having a coefficient of thermal expansion close to that of quartz glass forming the optical part. .