KR20190042218A - Apparatus for detecting light temperature using polarization maintaining optical fiber - Google Patents

Abstract

According to an embodiment of the present invention, the present invention relates to an apparatus for measuring light temperatures using a polarization-maintaining optical fiber, which comprises: a light source for generating light; a first polarization-maintaining optical fiber connected to the light source, transmitting the light, and including a first slow axis and a first fast axis perpendicular to the first slow axis; a temperature measurement unit including a second polarization-maintaining optical fiber which transmits the light received from the first polarization-maintaining optical fiber and includes a second slow axis and a second fast axis perpendicular to the second slow axis, disposed to have a predetermined angle with the first slow axis and the first fast axis by being fused to the first polarization-maintaining optical fiber to have a predetermined angle, and a mirror disposed at an end of the second polarization-maintaining optical fiber to reflect the received light; a first light detection unit connected to the first polarization-maintaining optical fiber, and reflected by the mirror to detect power of the light passing through the second and first polarization-maintaining optical fibers; and a temperature calculation unit for calculating a difference value between power of light at a reference temperature and that of light measured by the first light detection unit, calculating a temperature change amount compared to the reference temperature on the basis of the calculated difference value, and calculating a temperature of the light received by the temperature measurement unit.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a device for measuring optical temperature using a polarization maintaining optical fiber,

The present invention can measure a light temperature using a characteristic that a polarization difference between the light oscillating in the slow axis and the light oscillating in the fast axis is changed by changing the length of the polarization maintaining optical fiber according to the temperature change Maintaining optical fiber using a polarization maintaining optical fiber.

In the existing technology, it is very difficult to apply the conventional electric thermometer in the environment where strong EMI (electromagnetic interference) occurs, since the malfunction and the measurement error are severe. In order to measure temperature more precisely in this environment, many temperature sensors using light have been studied and commercialized.

However, a commercially available temperature sensor uses a fiber Bragg grating (FBG) to confirm the wavelength change reflected by the temperature. The temperature sensor using this method is a light source that outputs an expensive broadband wavelength or a wavelength variable light source And a wavelength analyzer for measuring the change in wavelength, and are sold at a very high price.

Therefore, in order to overcome the above problems, it is necessary to research and develop a technology for measuring temperature at low cost with accurate temperature measurement and simple structure even in a strong EMI environment.

SUMMARY OF THE INVENTION The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a polarization maintaining optical fiber which can measure a polarization change generated by a temperature dependency of a polarization maintaining optical fiber by using only a polarizer and a photodetector, And an optical temperature measuring device using the polarization maintaining optical fiber.

Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

An apparatus for measuring optical temperature using a polarization maintaining optical fiber according to the present invention comprises a light source for generating light, a light source connected to the light source, for transmitting light, and having a first slow axis and a second light source perpendicular to the first slow axis A first polarization maintaining optical fiber including a first fast axis and a first polarization maintaining optical fiber that transmits light received from the first polarization maintaining optical fiber and is fused so as to have a certain angle with the first polarization maintaining optical fiber, a slow axis and a second fast axis perpendicular to the second slow axis that are arranged to have a certain angle with the first fast axis and a slow axis that is perpendicular to the second slow axis, a second polarization maintaining optical fiber including a first polarization maintaining optical fiber and a second polarization maintaining optical fiber, and a mirror disposed at an end of the second polarization maintaining optical fiber and reflecting the received light; And the second polarized light A first optical detector for detecting the output of light passing through the holding optical fiber and the first polarization maintaining optical fiber, and a difference value between the output of light at the reference temperature and the output of light measured at the first optical detector, And a temperature calculator for calculating a temperature change amount with respect to a reference temperature based on the difference value and calculating a temperature of light currently received by the temperature measurement unit.

 An apparatus for measuring optical temperature using a polarization maintaining optical fiber includes a light distribution unit for distributing light received from the light source, and a light source disposed between the light source and the light distribution unit, the first slow axis and the first fast axis fast axis of the first polarized light holding fiber and the second polarized light holding axis of the first polarized light holding fiber and the first polarized light holding fiber, Since the two polarization maintaining optical fibers are fused at a constant angle, linearly polarized light traveling along any one axis of the first slow axis and the first fast axis passing through the first polarizer And two linearly polarized lights passing through the second slow axis and the two fast axes while passing through the second polarization maintaining optical fiber, and the phase difference between the two linearly polarized light is Lt; / RTI >

The optical temperature measuring device using the polarization maintaining optical fiber is connected to the optical distributor and is reflected by the mirror and passes through the second polarization maintaining optical fiber, the first polarization maintaining optical fiber, and the second slow axis slow and a second polarizer which passes only linearly polarized light proceeding along any one of two linear polarized light proceeding along the first fast axis and the second linear polarized light, It is possible to detect the output power of the motor.

The temperature calculating unit changes the length of the second polarization maintaining optical fiber according to the change of the temperature of the light beam received by the temperature measuring unit and changes the phase difference between the two linearly polarized light according to the change of the length, Since the output power of the light measured by the first photodetector unit changes, the current value of the light received by the current temperature measurement unit is received by the current temperature measurement unit based on the difference between the power of the light at the reference temperature and the power of the light measured by the first photodetector unit. It is possible to calculate the temperature of the light.

According to the disclosed invention, it is possible to easily measure the temperature by using a simple structure by measuring only the optical output by using the polarizer and the optical detection unit for the polarization change generated by the temperature dependency of the polarization maintaining optical fiber.

In addition, the measurement time can be shortened by directly measuring the output of the light without changing the wavelength and measuring the temperature.

1 is a view for explaining an optical temperature measuring apparatus using a polarization maintaining optical fiber according to an embodiment of the present invention.
FIGS. 2 and 3 are diagrams for explaining a change in optical output according to a phase difference between two linearly polarized lights. FIG.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a view for explaining an optical temperature measuring apparatus using a polarization maintaining optical fiber according to an embodiment of the present invention.

1, an optical temperature measuring apparatus 100 using a polarization maintaining optical fiber includes a light source 110, a first polarization unit 120, a light distribution unit 130, a first polarization maintaining optical fiber 140, A first optical detector 170, a temperature calculator 180, and a second optical detector 190. The first optical detector 150, the second polarizer 160, the first optical detector 170,

The light source 110 may generate light.

The first polarizing portion 120 may be disposed between the light source 110 and the optical splitter 130.

The first polarization section 120 can transmit only linearly polarized light traveling along any one of a first slow axis and a first fast axis included in the first polarization maintaining optical fiber 140 have. For example, the first polarizing section 120 can pass only linear polarized light traveling in a first slow axis included in the first polarization maintaining optical fiber 140. It is possible to select a polarizing unit which passes through either the first slow axis or the first fast axis depending on the implementation.

The light distribution unit 130 can distribute the received light. The optical distributor 130 may be disposed between the first polarization section 120, the second polarization section 160, the temperature measurement section 150, and the second optical detection section 180.

The light distribution unit 130 may distribute the light received from the light source 110 to the temperature measurement unit 150 and the second optical detection unit 180. For example, the light distribution unit 130 may distribute the light received from the light source 110 to the temperature measurement unit 150 and the second optical detection unit 180 at a ratio of 50:50.

The light distribution unit 130 may distribute the light received from the temperature measurement unit 150 to the first optical detection unit 170.

The first polarization maintaining optical fiber 140 is connected to the light source 110 and transmits light and has a first fast axis perpendicular to a first slow axis and a first slow axis . On the first slow axis, there is a portion having a relatively higher refractive index than the other portion, so that light can be transmitted slower than the second fast axis.

The first polarization maintaining optical fiber 140 includes a light source 110, a first polarization unit 120, a light distribution unit 130, a temperature measurement unit 150, a second polarization unit 160, a first optical detection unit 170, And the second optical detecting unit 180. [0050]

The temperature measuring unit 150 includes a second polarization maintaining fiber 151 and a mirror 152.

The second polarization maintaining fiber 151 may transmit light received from the first polarization maintaining optical fiber 140 or may reflect reflected light from the mirror 152.

The second polarization maintaining fiber 151 includes a second slow axis and a second fast axis perpendicular to the second slow axis.

The second polarization maintaining fiber 151 is fused to the first polarization maintaining optical fiber 140 at a predetermined angle. Accordingly, the second slow axis and the second fast axis can be staggered to have a constant angle with the first slow axis and the first fast axis. For example, as shown in FIG. 1, the second slow axis and the second fast axis are disposed at a 45 degree angle with the first slow axis and the first fast axis, As shown in Fig.

Since the first polarization maintaining optical fiber 140 and the second polarization maintaining optical fiber 151 are fusion-bonded at a predetermined angle, the first slow axis passing through the first polarization section 120, the linearly polarized light proceeding along any one of the fast axis and the fast axis passes through the second polarization maintaining optical fiber 151 and passes through the second slow axis and the second fast axis, . Thus, the phase difference of the two linearly polarized lights can be generated.

The mirror 152 is disposed at the end of the second polarization maintaining optical fiber 151 and can reflect the received light. That is, the mirror 152 can reflect the light received through the first polarization maintaining optical fiber 140 and the second polarization maintaining optical fiber 151.

The second polarizer 160 may be connected to the optical splitter 130.

The second polarized light portion 160 is reflected by the mirror 152 and passes through a second slow axis passing through the second polarization maintaining optical fiber 151, the first polarization maintaining optical fiber 140, and the optical splitter 130, And the linearly polarized light proceeding along any one axis of the two linearly polarized light proceeding along the second fast axis.

The first optical detecting unit 170 is connected to the optical splitter 130 and detects the output power of the light reflected by the mirror 152 and passed through the second polarization maintaining optical fiber 151 and the first polarization maintaining optical fiber 140, Can be detected.

The principle that the temperature arithmetic unit 180 calculates the temperature of the light is as follows. The length of the second polarization maintaining optical fiber 151 is changed according to the change of the temperature of the light beam received by the temperature measuring unit 150. As the length of the second polarization maintaining optical fiber 151 changes, the phase difference between the two linearly polarized light beams generated by the second polarization maintaining optical fiber 151 changes, and as the phase difference changes, The power changes. The temperature calculation unit 180 calculates the temperature of the light received by the current temperature measurement unit 150 based on the difference between the output power of the light at the reference temperature and the output power of the light measured at the first optical detection unit 170 The temperature can be calculated.

The temperature calculator 180 can calculate the difference between the output power of the light at the reference temperature and the output power of the light measured at the current first optical detector 170. [ For example, the temperature calculating unit 180 detects the power of light at 25 degrees using the first optical detecting unit 170, sets the detected power as a reference value, and calculates the difference between the set reference value and the output power of the currently measured light Value can be calculated.

The temperature arithmetic unit 180 can calculate the temperature change amount with respect to the reference temperature based on the calculated difference value. For example, when the difference value of the power of light is changed by A, the temperature arithmetic unit 180 can calculate the temperature change amount based on the correlation between the power change of the light and the temperature change.

The temperature arithmetic unit 180 can calculate the temperature of light that is currently received by the temperature measurement unit based on the calculated temperature change amount. For example, when the temperature change amount is +0.5 degrees, the temperature arithmetic unit 180 can calculate the current temperature at 25.5 degrees. It is assumed that the temperature changes by 1 degree each time the output of the light differs by A. If the difference between the set reference value and the power of the currently measured light is changed by 2A, the temperature calculator 180 may add +2 at the reference temperature (25 degrees) to measure the current temperature at 27 degrees.

The second optical detector 180 may detect the power of the light received through the optical splitter 130. The characteristics of the light generated by the light source 110 can be monitored by the output power of the light detected by the second light detecting unit 180. For example, by observing the optical characteristics of the light source 110 measured by the second optical detection unit 180, it is possible to determine whether the change in the optical output generated by the first optical detection unit 170 is due to the output change of the light source 110 , It can be known whether the optical output change is caused by the length change of the second polarization maintaining optical fiber. Specifically, when the output of the light source 110 is changed by A, the second light detecting unit 180 may measure a change in the output of the light source 110 and recognize a change by A. Therefore. When the change value measured by the first optical detector 170 is A, it can be understood that the cause is caused by the output change of the light source 110, not the optical output change according to the length change of the second polarization maintaining optical fiber.

According to the optical temperature measuring apparatus of the present invention, the temperature dependence of the polarization maintaining optical fiber is generated by using the temperature dependency (the property that the length changes according to the temperature change and the phase difference of the two linearly polarized light changes according to the change in length) By simply measuring the optical output using the polarizer and the optical detector, the temperature can be easily measured using a simple structure.

Further, according to the optical temperature measuring apparatus according to the present invention, the measurement time can be shortened by directly measuring the output of light without changing the wavelength and measuring the temperature.

FIGS. 2 and 3 are diagrams for explaining a change in optical output according to a phase difference between two linearly polarized lights. FIG.

Referring to FIGS. 1, 2 and 3, the blue line represents the power of light passing through the second fast axis, and the red line represents the light passing through the second slow axis And the output of light.

The power of light can be obtained by the following equations.

Here, y ₁ is the output power of the light output to the second slow axis, and y ₂ is the output power of the light output to the second fast axis.

_Eox is the electric field magnitude of the light of the second slow axis output from the second polarization section 160 and E _oy is the magnitude of the electric field of the second fast axis fast output from the second polarization section 160 E _ix is the electric field magnitude of the light of the second slow axis input to the second polarizer 160 and E _iy is the magnitude of the electric field of the second polarizer 160 The electric field magnitude of the second fast axis, and? Denotes the phase difference.

When the phase difference between the two linearly polarized light is between 0 and 90 degrees, the power of the light passing through the second fast axis increases as the phase difference increases. This phenomenon is repeated based on 90 degrees.

The length of the second polarization maintaining optical fiber 151 changes in accordance with the change of the temperature of the light beam received by the temperature measuring unit 150, and finally the phase difference of the two linearly polarized light is changed. 2 and 3, the temperature arithmetic unit 180 calculates a temperature change amount based on a change in power of light in accordance with a change in phase difference, and calculates a current temperature based on the calculated temperature change amount . As shown in FIG. 3, a reference point is set as a reference point in which a change ('slope') of the power of light according to a change in phase difference is large ('around 45 degrees'), Can be calculated. The use of the section in which the power of the light varies with the change of the phase difference makes the change in the power of the light large even when the phase difference is small, can do.

The embodiments described may be constructed by selectively combining all or a part of each embodiment so that various modifications can be made.

It should also be noted that the embodiments are for explanation purposes only, and not for the purpose of limitation. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

100: Optical temperature measurement device using polarization maintaining optical fiber
110: Light source
120: first polarization section
130:
140: First polarization maintaining optical fiber
150: Temperature measuring unit
151: second polarization maintaining fiber
152: mirror
160: second polarizing portion
170:
180:
190:

Claims (4)

A light source for generating light;
A first polarization maintaining optical fiber coupled to the light source and transmitting light and including a first slow axis and a first fast axis perpendicular to the first slow axis;
And a second polarization maintaining optical fiber for transmitting light received from the first polarization maintaining optical fiber and fused so as to have a predetermined angle with the first polarization maintaining optical fiber to form a constant angle with the first slow axis and the first fast axis A second polarization maintaining optical fiber including a second slow axis arranged to have a second axis and a second fast axis perpendicular to the second slow axis, A temperature measuring unit disposed at an end of the light source and including a mirror for reflecting the received light;
A first optical detector connected to the first polarization maintaining optical fiber and detecting a power of light reflected by the mirror and having passed through the second polarization maintaining optical fiber and the first polarization maintaining optical fiber; And
Calculating a difference value between a power of light at a reference temperature and a power of light currently measured at the first optical detector, calculating a temperature change amount with respect to a reference temperature based on the calculated difference value, And a temperature calculation unit for calculating a temperature of light received by the polarization maintaining optical fiber.
The method according to claim 1,
A light distribution unit for distributing light received from the light source; And
And a first polarizer disposed between the light source and the light distribution unit and passing only linearly polarized light traveling along any one of the first slow axis and the first fast axis, ,
Since the first polarization maintaining optical fiber and the second polarization maintaining optical fiber are fused at a certain angle, it is preferable that the first slow axis and the first fast axis, which pass through the first polarization section, A linear polarized light traveling on one axis is divided into two linear polarized lights passing through the second slow axis and the two fast axes while passing through the second polarization maintaining optical fiber, Wherein the phase difference is generated by using the polarization maintaining optical fiber.
3. The method of claim 2,
And the second slow axis and the second fast axis that are reflected by the mirror and pass through the second polarization maintaining optical fiber, the first polarization maintaining optical fiber, and the optical splitter, and a second polarizer for passing only linearly polarized light proceeding along any one of the two linear polarized lights proceeding in the direction of the axis,
Wherein the first optical detecting unit detects power of linearly polarized light having passed through the second polarizing unit.
The method of claim 3,
The temperature calculation unit calculates,
The length of the second polarization maintaining optical fiber is changed according to a change in the temperature of the light beam received by the temperature measuring unit, the phase difference between the two linearly polarized light changes according to the change in length, The temperature of the light that is currently received by the temperature measuring unit based on the difference between the power of the light at the reference temperature and the power of the light measured at the first optical detecting unit, Holding optical fiber.

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