KR100933771B1 - Lattice-type photo sensor and Lattice-based mixed gas measurement method for mixed gas measurement - Google Patents

Abstract

A grating type optical sensor for measuring mixed gas is provided. A grating type optical sensor for measuring a concentration of a gas constituting a mixed gas, comprising: a light source for outputting an optical signal; A sensing unit including a long period grating coated with a material to receive an optical signal output from the light source and to output the long period grating transmission optical signal in which optical characteristics are changed in response to the mixed gas; A signal processing unit including a short period grating for inputting an optical signal output from the sensing unit to be output as a frequency modulated optical signal having a wavelength varying within a wavelength range defined by a speed of a modulation frequency f; And a concentration calculator configured to calculate a concentration for each gas of the mixed gas through the frequency-modulated optical signal. The grating-type optical sensor for measuring mixed gas may have a gas concentration irrespective of changes in the surrounding environment such as temperature and humidity. It can measure and can be applied to various purposes through simple change of sensing unit.

Gas, sensor, frequency, grating, reflection, transmission

Description

Optical grating sensor for measuring mixed gases and method for measuring mixed gases based on grating

The present invention relates to an optical sensor for measuring the concentration of a mixed material and a method for measuring the mixed material, and more particularly, a lattice type optical sensor for measuring a mixed gas for measuring the concentration of the mixed gas using a long period grating and a short period grating. And a grid-based mixed gas measurement method.

The conventional gas sensor for gas detection is largely divided into a semiconductor gas sensor and a contact combustion gas sensor. The semiconductor gas sensor uses the principle that the electrical conductivity of the semiconductor is changed when the gas contacts the surface of the specific semiconductor crystal element in which the defective region exists. That is, the concentration of the gas is measured by converting the change in the electrical conductivity of the semiconductor due to the contact of the gas into a voltage, current or resistance value.

Contact combustion gas sensors are mainly used to measure flammable gases. The combustible gas reacts with oxygen to generate heat of reaction, and the catalytic combustion gas sensor converts the heat of reaction into an electrical signal to measure the gas. At this time, since the combustible gas is hydrocarbon-based, the calorific value is greatest when completely oxidized to water (H ₂ O) and carbon dioxide (CO ₂ ). However, the complete oxidation of the gas is difficult to occur at low temperatures, and even if it occurs, the reaction rate is slow, making real-time measurement impossible. Therefore, a catalyst that promotes complete oxidation and sufficient oxygen are required for faster measurement, and the temperature of the sensor reaction section must be increased to increase the reaction rate.

In the case of a semiconductor gas sensor, since it is greatly influenced by environmental factors such as ambient temperature and humidity, there is a disadvantage in that an additional sensor that can compensate for this is installed. In addition, it is effective only when measuring a single gas because it is difficult to measure the gas-specific concentration of the mixed gas.

In addition, the contact combustion gas sensor is not significantly affected by the surrounding environment, and even if the gas to be measured is mixed, it is possible to accurately measure the concentration of the desired gas. However, because the measurement must go through a chemical process called combustion, secondary by-products are produced, and the process has a disadvantage in that accurate measurement is difficult in an environment where oxygen is deficient.

As such, the existing gas sensor is highly influenced by the surrounding environment, and thus, an additional stabilization system must be provided for accurate measurement. That is, in order to implement a multi-sensor, a remote sensor, and a distributed sensor in which sensing parts exist in various places to detect various kinds of gases, there is a problem in that system configuration cost is increased due to an additional facility for securing stability. In addition, the conventional gas sensor is a sensor based on the electronic circuit, there was a problem that is affected by the electromagnetic waves.

Therefore, in order to utilize the gas sensor in an environment where high stability is required, such as a gas detection sensor used in a nuclear power plant, a sensor having less influence on the surrounding environment fluctuation is required.

Accordingly, an object of the present invention is to propose a lattice-type optical sensor and a lattice-based mixed gas measuring method for measuring a mixed gas which can measure the concentration of each gas constituting the mixed gas separately.

In addition, another object of the present invention is to propose a grid type optical sensor and a grid-based mixed gas measuring method for measuring a stable mixed gas, which can measure the gas concentration irrespective of changes in the surrounding environment such as temperature and humidity changes. will be.

In addition, another object of the present invention is to propose a grating-type optical sensor and a grating-based mixed gas measurement method for the mixed gas measurement that can easily detect a gas from a distant or several places.

According to an aspect of the invention, the optical sensor for measuring the concentration of the gas constituting the mixed gas, the light sensor outputs an optical signal; A sensing unit including a long period grating coated with a material to receive an optical signal output from the light source and to output the long period grating transmission optical signal in which optical characteristics are changed in response to the mixed gas; A signal processing unit including a short-period grating for inputting a long-period grating transmission optical signal output from the sensing unit to output a frequency-modulated optical signal having a wavelength varying within a wavelength range defined by the speed of the modulation frequency f; And a concentration calculator configured to calculate a concentration for each gas of the mixed gas through the frequency-modulated optical signal.

In this case, the concentration calculator comprises a signal converter for converting the frequency-modulated optical signal into an electrical signal; And a band pass filter for separating frequency components of the frequency-modulated optical signal from the electrical signal, and the minimum number of the sensing units may be equal to the number of types of the mixed gas to be measured.

The sensing unit and the signal processor may be formed inside the optical waveguide, and the concentration calculator may calculate the concentration of each gas of the mixed gas through the magnitude of the frequency modulated optical signal. In addition, the material for coating the long period lattice may be different depending on the type of gas to be measured.

According to another aspect of the invention, a method for measuring the concentration of the gas constituting the mixed gas, comprising the steps of: outputting an optical signal; Receiving the optical signal and outputting the optical signal as a long-period grating transmission optical signal in which an optical characteristic is changed in response to the mixed gas; Receiving the optical signal transmitted through the long-period lattice and outputting the optical signal as a frequency-modulated optical signal having a wavelength that changes at a rate of a modulation frequency f within a limited wavelength range; And calculating a concentration of each gas of the mixed gas through the frequency-modulated optical signal.

In this case, calculating the concentration of each gas of the mixed gas through the frequency modulated optical signal may include converting the frequency modulated optical signal into an electrical signal; Separating frequency components of the frequency modulated optical signal from the electrical signal; And calculating a concentration of gas through the separated electrical signal.

In the calculating of the gas concentration of the gas mixture using the frequency modulated optical signal, the gas concentration of the gas mixture may be calculated through the magnitude of the frequency modulated optical signal.

According to another aspect of the invention, the optical sensor for measuring the concentration of the material constituting the mixed material, the light sensor outputs an optical signal; A sensing unit including a long period grating coated with a material to receive an optical signal output from the light source and to output the long period grating transmission optical signal in which optical characteristics are changed by reacting the input optical signal with the mixed material; A signal processing unit including a short-period grating for inputting a long-period grating transmission optical signal output from the sensing unit to output a frequency-modulated optical signal having a wavelength varying within a wavelength range defined by the speed of the modulation frequency f; And a concentration calculator configured to calculate a concentration for each material of the mixed material through the frequency-modulated optical signal.

In this case, the concentration calculator comprises a signal converter for converting the frequency-modulated optical signal into an electrical signal; And a band pass filter for separating frequency components of the frequency modulated optical signal from the electrical signal, and the minimum number of the sensing units may be equal to the number of types of the mixed materials to be measured.

In addition, the sensing unit and the signal processor may be formed inside the optical waveguide, the concentration calculator may calculate the concentration for each material of the mixed material through the magnitude of the frequency-modulated optical signal. In addition, the material for coating the long period lattice may be different depending on the type of material to be measured.

According to another aspect of the present invention, a method for measuring the concentration of a material constituting a mixed material, comprising: outputting an optical signal; Receiving the optical signal and outputting the optical signal as a long-period lattice transmission optical signal in which optical characteristics are changed by reacting with the mixed material; Receiving the optical signal transmitted through the long-period lattice and outputting the optical signal as a frequency-modulated optical signal having a wavelength that changes at a rate of a modulation frequency f within a limited wavelength range; And calculating a concentration of each material of the mixed material through the frequency-modulated optical signal.

In this case, calculating the concentration of each substance of the mixed material through the frequency modulated optical signal may include converting the frequency modulated optical signal into an electrical signal; Separating frequency components of the frequency modulated optical signal from the electrical signal; And calculating a concentration of a substance through the separated electrical signal.

In addition, calculating the concentration of each substance of the mixed material through the frequency modulated optical signal may calculate the concentration of each substance of the mixed substance through the magnitude of the frequency modulated optical signal.

According to the grating type optical sensor and the grating-based mixed gas measuring method for measuring the mixed gas according to the present invention, the concentration of each gas constituting the mixed gas at a long distance and at a dispersed place can be measured through a simple configuration. .

In addition, according to the grating-type optical sensor and the grating-based mixed gas measuring method for measuring the mixed gas according to the present invention, it is possible to accurately measure the concentration of each gas in spite of the influence of the electromagnetic wave and the change of the surrounding environment such as temperature and humidity change. Can be.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

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

First, a configuration of a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a block diagram of a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention.

The grating type optical sensor for measuring the mixed gas according to the present exemplary embodiment includes a light source 110, a detector 120, a signal processor 130, and a concentration calculator 140.

The light source 110 according to the present embodiment may be a broadband light source, and may be an LED or a white light source. The light source 110 may be used in addition to the LED or white light source, various light sources within the scope of the present invention. The light signal 112 is output from the light source 110, and the light signal 112 thus output is input to the sensing unit 120.

The sensing unit 120 is coated with a material such that the optical signal 112 input to the sensing unit 120 is outputted as a long-period grating transmission optical signal 114 whose optical characteristics have changed in response to the mixed gas to be measured. Contains a long period grid. At this time, the optical signal 112 that has passed through the long period grating, the partial wavelength region is transferred to the outside disappears, the optical properties are changed. Hereinafter, in the present specification, the long period grating transmission optical signal 114 clarifies that the optical signal 112 inputted to the sensing unit 120 passes through the long period grating to change the optical characteristic to output the optical signal.

In this case, the material for coating the long-period lattice varies depending on the type of gas to be detected by the optical sensor, such as using SnO ₂ as a coating material in order to detect ethylene (C ₂ H ₅ OH) gas. The material coated on the long-period grating reacts with the external mixed gas, and the optical signal 112 passing through the long-period grating is output as the long-period grating transmission optical signal 114 having changed optical characteristics. According to the present embodiment, the missing wavelength region of the long period grating transmission optical signal 114 in which some wavelength regions disappear while passing through the long period grating is changed according to the concentration of the external material, that is, the mixed gas. By measuring the amount of change in the disappeared wavelength region, an external mixed gas can be detected. This will be described in more detail with reference to FIG. 2.

As such, the long-period grating transmission optical signal 114 outputted by reacting the optical signal with the mixed gas is input to the signal processor 130 and output as the frequency-modulated optical signal 116. The signal processor 130 according to the present exemplary embodiment outputs the input long-period grating transmission optical signal 114 as a frequency modulated optical signal 116 having a wavelength that varies within a wavelength range defined by the speed of the modulation frequency f. It includes a short period lattice. Hereinafter, the frequency-modulated optical signal 116 is a signal in which the long-period grating transmission optical signal 114 is input to the signal processing unit 130 and has a wavelength value that varies within a range limited by the speed of the variation frequency f. To clarify. The short-period grating according to the present embodiment has a characteristic of reflecting an optical signal having a specific wavelength, and the period or refractive index of the short-period grating is changed according to a control signal applied to the short-period grating to change the reflected wavelength value. have.

The frequency modulated optical signal 116 output from the signal processor 130 is input to the concentration calculator 140, and the concentration calculator 140 calculates the gas concentration of the mixed gas through the frequency modulated optical signal 116. I will do it. The signal processor according to the present exemplary embodiment includes a signal converter configured to convert the frequency modulated optical signal 116 into an electrical signal, and a bandpass filter that separates frequency components of the frequency modulated optical signal 116 from the converted electrical signal. can do.

As described above, the concentration of each gas of the mixed gas may be measured by the operations of the light source 110, the detector 120, the signal processor 130, and the concentration calculator 140. In this case, according to the present embodiment, the sensing unit 120 and the signal processing unit 130 may be manufactured in the optical waveguide, respectively. An optical waveguide is a structure capable of guiding optical power, and refers to an optical fiber designed to transmit an optical signal in optical communication. Since the optical sensor according to the present exemplary embodiment may form components in an optical waveguide, it may be easily implemented as a distributed sensor capable of detecting gas at each point by distributing a remote sensor and a sensing unit that can be measured at a long distance. have.

Hereinafter, the configuration and operation of a sensing unit according to an embodiment of the present invention will be described with reference to FIGS. 2A and 2B. 2A is a block diagram illustrating a configuration of a sensing unit according to an embodiment of the present invention, and FIG. 2B illustrates a change in transmittance according to a wavelength of a first modulated light signal output from the sensing unit according to an embodiment of the present invention. It is a graph.

As described above in FIG. 1, the optical signal 112 output from the light source 110 is input to the sensing unit 120. In this case, the sensing unit may be formed in the optical waveguide, as shown in FIG. 2A. The optical waveguide includes a core 171, which is a central portion, and a cladding 172 surrounding the core. The optical signal 112 inputted to the optical waveguide proceeds along the core 171 according to the principle of total reflection, and mode conversion occurs at a portion corresponding to the long period grating 121 included in the detector 120.

Since the refractive index of the core 171 has a larger value than that of the cladding 172, the optical signal input to the sensing unit 120 formed in the optical waveguide proceeds to the inside of the core 171 according to the principle of total reflection. In the part where the long period grating 121 is formed, the optical signal 112 input due to the change in the refractive index of the core 171 and the cladding 172 does not proceed to the inside of the core 171, but proceeds to the outside. Such a change in refractive index between the core 171 and the cladding 172 region by the long period grating 121 is hereinafter referred to as mode conversion between core mode and cladding mode.

Mode conversion of the core 171 mode and the cladding 172 mode occurs only in some wavelength regions depending on the period of the long period lattice 121 and the material 123 coated on the outside of the cladding 172 region or the refractive index. As a result of the mode conversion, the input optical signal 112 travels out of the cladding 172 in some wavelength region and disappears. In this case, a portion of the wavelength region of the optical signal that is carried out and disappears from the cladding 172 is referred to as the reaction wavelength region of the long period grating 121, and the reaction wavelength region is used herein in the same meaning as described above. Looking at the characteristics of the optical signal 112 passed through the long period grid 121, that is, the long period grating transmission optical signal 114 output through the long period grid 121, as shown in Figure 2b, corresponding to the reaction wavelength region It can be seen that the optical signal having a wavelength value that disappears due to the mode conversion.

When the type or refractive index of the material 123 coated on the exterior of the cladding 172 is changed, the reaction wavelength region is changed as shown in the long-term grating transmission optical signals 114 (1) and 114 (2) shown in FIG. 2B. Will change. Since the change value of the changed reaction wavelength region is closely related to the refractive index change of the material 123 coated on the outside of the cladding 172 region, the mixed gas existing outside the detection unit 120 by measuring the change amount of the reaction wavelength region. The amount of change in can be measured.

The principle of basically detecting the gas in the optical sensor according to the present embodiment is as follows. First, a material 123 is coated on the outside of the long period grating 121 to react with a gas constituting the mixed gas to change optical characteristics such as refractive index. In this case, the coating material 123 is changed according to the type of gas to be detected as described above. Therefore, the number of detectors 120 varies according to the number of gas types to be detected. For example, if there are three types of gas to be measured, at least three detectors 120 are required. Since the material 123 coated on the long period grating 121 included in the detector 120 is determined according to the type of gas, the minimum number of the detector 120 is determined according to the type of gas to be measured. Will be.

In addition, when various materials react to one type of gas, when a plurality of sensing units 120 coated with different materials 123 are allocated to one type of gas, a specific sensing unit 120 may fail. Even if the whole system can be operated continuously without stopping, the stability and precision can be increased. Therefore, in this case, the number of the sensing unit 120 may be larger than the type of gas to be measured.

As described above, by coating the material 123 whose optical properties change in response to the gas on the long period grating, the wavelength change of the long period grating transmitted optical signal according to the gas concentration change as shown in FIG. 2B can be measured. The measured wavelength change includes information on the concentration of the gas.

The detector 120 may be applied to a place where a material other than gas is measured. When optical fluctuations in the external environment surrounding the long period grating 121 occur, the wavelength region disappeared by the long period grating 121, that is, the reaction wavelength region is changed. When a material reacting to a specific material is coated on the outside of the long period grating 121 and exposed to the material, the optical variation varies depending on the concentration of the material. Is determined.

That is, the sensing unit according to the present embodiment may be variously applied by coating a material reacting to a material to be sensed in addition to the gas. In addition, when the liquid-based material is located outside the long-period grating 121, the reaction wavelength region of the long-period grating 121 is changed according to the refractive index change of the liquid material even without coating a specific material. This allows the concentration of liquid substances to be measured.

Hereinafter, the configuration and operation of a signal processor according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3A and 3B. 3A is a block diagram illustrating a signal processing unit according to an embodiment of the present invention, and FIG. 3B illustrates a change in reflectance according to a wavelength of a second modulated light signal output from a signal processing unit according to an embodiment of the present invention. The graph shown.

According to an embodiment of the present invention, the signal processor 130 may be formed inside the optical waveguide. Hereinafter, a case in which the signal processor 130 is formed inside the optical waveguide will be described with reference to FIG. 3A.

The signal processor 130 includes a short period grating 131 formed inside the optical waveguide. The short period grating 131 has a characteristic of reflecting an optical signal having a specific wavelength value, as shown in FIG. 3B.

By applying a control signal to the short period grating 131, the reflected wavelength may be changed by changing the period or refractive index of the short period grating. In this case, the reflected wavelength may be changed by applying a control signal to the material 133 attached to the outside of the short period grating.

A control signal having a frequency f is applied to the short period grating 131 to modulate the wavelength reflected by the short period grating to a modulation frequency f within a limited wavelength range. The long period grating transmitted optical signal 114 (1) input to the short period grating 131 passes through the short period grating 131 to the optical signal 116 (1) that is reflected at the wavelength lambda 1 and is frequency-modulated. Is output. As the period or refractive index of the short-period grating is changed by a control signal applied to the short-period grating 131, the reflection wavelength reflected by the short-period grating 131 is changed. That is, the long-period grating transmission optical signal is reflected by the short-period grating 131 by a control signal having a modulation frequency f and is a frequency-modulated optical signal 116 having a wavelength value that varies within a wavelength range of λ 1 to λ 2. 2)), wherein the rate at which the frequency-modulated optical signal changes within a limited wavelength range of λ 1 to λ 2 is equal to the modulation frequency f.

Referring to FIG. 2B, the reflected wavelength reflected by the short-period grating 131 is a frequency-modulated optical signal having a wavelength value that varies within a range of a limited wavelength region λ1 to λ2 according to a control signal applied thereto. 116 (1), 116 (2)). The signal processor 130 receives the long-period grating transmitted optical signal output from the sensing unit and outputs the frequency-modulated optical signal having a wavelength that changes within a wavelength range defined by the speed of the modulation frequency f. That is, the short-period grating 131 included in the signal processor 130 outputs the frequency modulated optical signal 116 having the reflected wavelength, and at this time, the wavelength reflected by the control signal applied to the short-period grating 131. The value changes, and the rate of change of the wavelength of the frequency modulated optical signal 116 may be represented by a modulation frequency f having the same value as the frequency of the control signal.

The frequency modulated optical signal having a wavelength that is changed within the wavelength range defined by the speed of the modulation frequency f is input to the concentration calculation unit, and the concentration calculation unit uses the frequency modulated optical signal to determine the concentration of each gas of the mixed gas. Will be calculated. In this case, the concentration calculator may include a signal converter for converting the frequency-modulated optical signal into an electrical signal and a band pass filter for separating frequency components of the frequency-modulated optical signal from the electrical signal. This will be described in more detail with reference to FIG. 4.

4 is a graph illustrating a principle of concentration calculation of a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention.

The optical signal 112 output from the light source 110 is input to the detector 120. The input optical signal 112 is output by the long period grating 121 included in the sensing unit 120 as a long period grating transmission optical signal in which the optical signal in the reaction wavelength region disappears, as shown by curves 410 and 411 shown in FIG. 4. do

The long period grating transmitted optical signal output from the detector 120 is input to the signal processor 130. By applying a control signal to the short-period grating 131 included in the signal processing unit 130, the frequency-modulated optical signal 430 having a wavelength in a limited wavelength range from lambda 1 to lambda 2, as described above, has a speed of modulation frequency f. Will output

The long-period grating transmission optical signal 410 input from the sensing unit 120 to the signal processing unit 130 is output as a frequency-modulated optical signal having a wavelength of λ1 to λ2 in the short-period grating of the signal processing unit 130. At this time, the frequency-modulated optical signal has a light intensity between the transmittance 403 of the wavelength λ 1 and the transmittance 401 of the wavelength λ 2, as shown in 420, and has a modulation frequency f. Therefore, when no gas is present, the frequency modulated optical signal input to the concentration calculator has a light intensity between the transmittance 403 of the wavelength λ 1 and the transmittance 401 of the wavelength λ 2, and has a modulation frequency f. In this case, the signal converter included in the concentration calculator converts and outputs a current and a voltage having a value proportional to the intensity of the frequency-modulated optical signal.

In addition, when there is a gas to be detected outside the sensing unit 120, as described above, the optical characteristics of the material 123 coated on the long period grating 121 included in the sensing unit 120 are changed. The response wavelength of the optical signal transmitted through the long period grating is changed as shown in 411 of FIG. 4.

In the present specification, it is assumed that the reaction wavelength of the long-period lattice changes toward the longer wavelength when the concentration of the gas increases, but the present invention is not limited thereto, and the present invention can be applied even when the reaction wavelength changes to the shorter wavelength when the concentration of the gas increases. Is apparent to those skilled in the art. If there is no gas but gas is the same as the case where the concentration of the gas is increased, the reaction wavelength of the sensing unit 120 is longer toward the longer wavelength than the case where no gas is present (410) as shown in FIG. 4. Change.

In this case, the short-period grating 131 included in the signal processing unit 130 changes the long-period grating transmission optical signal to have a wavelength value limited to a speed of the modulation frequency f, that is, a wavelength within a range of λ 1 to λ 2. The optical signal is output. As described above, the response wavelength of the long-period grating transmission optical signal is changed toward the longer wavelength as the concentration of the gas increases, so that the frequency-modulated optical signal output from the signal processing unit 130 has a wavelength λ 2 at a transmittance 403 of the wavelength λ 1. It has a light intensity between transmittance 402 and a modulation frequency f. That is, referring to FIG. 4, when the gas concentration is increased, the frequency-modulated optical signal 421 outputted is reduced in size compared to the frequency-modulated optical signal 420 when no gas is present. Able to know.

The frequency modulated optical signal output from the reduced and output signal converter is converted into an electrical signal proportional to the magnitude of the frequency modulated optical signal, and the converted electrical signal may be included in the density calculator. A bandpass filter separates the frequency components of the frequency-modulated optical signal. The concentration of each gas of the mixed gas is more accurately calculated based on the electrical signal passing through the bandpass filter.

In the optical sensor according to the present exemplary embodiment, the optical signal input to the sensing unit 120 is output as a long-period grating optical signal in which the reaction wavelength is changed according to the gas concentration by reacting with the gas, and the signal is processed by the signal processor 70 and the concentration calculator. By processing, the gas concentration can be calculated.

In addition, in the case of a lattice type optical sensor for measuring a mixed gas according to the present embodiment, it can be used as an optical sensor for detecting a gas by coating a material reacting with a specific gas, when coating a material reacting with other materials It can also be used as a sensor to measure the concentration and optical properties of materials.

5 and 6, an application example of a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention will be described. 5 is a conceptual diagram illustrating an application example in which a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention is applied to multiple sensors, and FIG. 6 is a grating type for measuring a mixed gas according to an embodiment of the present invention. This is a conceptual diagram showing an example of application of the optical sensor as a distributed sensor.

Referring to the multi-sensor according to the embodiment of the present invention shown in Figure 5, the response wavelengths of the long-period grating different from the detection unit (120a, 120b, 120c ..., hereinafter referred to as 120) and the reflection wavelength according to the response wavelength of the long-period grating And a signal processor 130a, 130b, 130c, hereinafter referred to as 130, including a short-period grating. The bandpass filter 143 converts an optical signal frequency-modulated by the signal converter 141 included in the concentration calculator 140 into an electrical signal and then combines the modulation frequency of each signal processor 130. By using these, the concentration of the gas may be calculated through an electrical signal corresponding to the concentration of the gas sensed by each detector 120.

In this case, when the material coated on the long-period lattice included in each sensing unit 120 is changed to a material reacting to different gases, the sensing unit 120 may be implemented as a multi-sensor for measuring mixed gas. A distributed sensor can be implemented that is distributed in several places. Of course, it will be apparent to those skilled in the art that both multi- and distributed sensors can be implemented together.

6 is an application example of a distributed sensor system based on a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention. As shown in FIG. 6, a plurality of detectors 120a, 120b, 120c..., 120 are referred to as 120 in one optical waveguide, and distributed in various places such as an office room to detect gas. . Unlike conventional sensors, since it is a gas sensor based on an optical waveguide such as an optical fiber, it is possible to form several sensing units on one optical fiber, even if the number of sensing units 120 increases, one light source 110 and one Since the system can be configured using the signal processor 130 and the concentration calculator 140, the multi-distributed sensor system can be implemented at low cost. In addition, as described above, the optical sensor may be implemented based on the optical fiber, and since the insertion loss of the optical signal of the optical fiber itself is considerably small, the optical signal may be transmitted over a long distance. That is, the present invention can be applied to a remote gas detector capable of detecting a gas concentration in a distant place.

Hereinafter, a grating-based grating-based grating-based mixed gas measuring method according to another embodiment of the present invention will be described with reference to FIG. 7. 7 is a control flowchart of a grating-based grating-based mixed gas measuring method according to another exemplary embodiment of the present invention. In the case of a lattice-based lattice-based mixed gas measuring method, since the lattice-based mixed gas measurement method has the same principle and the same operation process as that of the lattice-type optical sensor, the overlapping description will be omitted and briefly described.

First, an optical signal is output (S710). The optical signal output in this way is input, and the optical signal reacts with the mixed gas and outputs a long-period grating transmission optical signal in which optical characteristics are changed (S720). Then, the long period grating receives the transmission optical signal and outputs it as a frequency-modulated optical signal having a wavelength that changes within a wavelength range defined by the speed of the modulation frequency f (S730). Then, the concentration of each gas of the mixed gas is calculated through the frequency modulated optical signal (S740). In this case, calculating the concentration of each gas of the mixed gas through the frequency-modulated optical signal (S740) may calculate the concentration of each gas through the magnitude of the frequency-modulated optical signal, and may include three steps. .

First, the frequency-modulated optical signal is converted into an electrical signal (S741), and the frequency component of the frequency-modulated optical signal is separated from the electrical signal (S742), and the concentration of gas is calculated through the separated electrical signal (S743). ). This method is the same for the lattice-based mixed material measurement method.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

1 is a block diagram of a grating type optical sensor for measuring a mixed gas according to an embodiment of the present invention.

Figure 2a is a block diagram showing the configuration of a sensing unit according to an embodiment of the present invention.

Figure 2b is a graph showing the change in transmittance according to the wavelength of the long-period grating transmission optical signal output from the sensing unit according to an embodiment of the present invention.

Figure 3a is a block diagram showing the configuration of a signal processing unit according to an embodiment of the present invention.

3B is a graph illustrating a change in reflectance according to a wavelength of a frequency modulated optical signal output from a signal processor according to an exemplary embodiment of the present invention.

Figure 4 is a graph showing the principle of the concentration calculation of the grating type optical sensor for measuring the mixed gas, according to an embodiment of the present invention.

5 is a conceptual diagram illustrating an application example in which a grating-type optical sensor for measuring a mixed gas according to an embodiment of the present invention is applied to multiple sensors.

6 is a conceptual diagram illustrating an application example in which a grating-type optical sensor for measuring a mixed gas according to an embodiment of the present invention is applied as a dispersion sensor.

7 is a control flow chart of a grating-based grating-based mixed gas measurement method according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110: light source 140: concentration calculation unit

120: detector

130: signal processing unit

Claims (18)

In the optical sensor for measuring the concentration of the gas constituting the mixed gas, A light source for outputting an optical signal; A sensing unit including a long period grating coated with a material to receive an optical signal output from the light source and to output the long period grating transmission optical signal in which optical characteristics are changed in response to the mixed gas; A signal processing unit including a short-period grating for inputting a long-period grating transmission optical signal output from the sensing unit to output a frequency-modulated optical signal having a wavelength varying within a wavelength range defined by the speed of the modulation frequency f; And And a concentration calculator configured to calculate a concentration for each gas of the mixed gas through the frequency-modulated optical signal. The method of claim 1, The concentration calculation unit A signal converter converting the frequency modulated optical signal into an electrical signal; And And a bandpass filter for separating frequency components of the frequency-modulated optical signal from the electrical signal. The method of claim 1, The minimum number of the detector The grating type optical sensor for measuring the mixed gas, characterized in that the same as the number of types of the mixed gas to be measured. The method of claim 1, The sensing unit and the signal processing unit is a grid type optical sensor for measuring the mixed gas, characterized in that formed in the optical waveguide. The method of claim 1, The concentration calculation unit is a grid-type optical sensor for measuring the mixed gas, characterized in that for calculating the concentration for each gas of the mixed gas through the magnitude of the frequency-modulated optical signal. The method of claim 1, The grating type optical sensor for measuring the mixed gas, characterized in that the material for coating the long-period grating is different depending on the type of gas to be measured. In the method for measuring the concentration of the gas constituting the mixed gas, Outputting an optical signal; Receiving the optical signal and outputting the optical signal as a long-period grating transmission optical signal in which an optical characteristic is changed in response to the mixed gas; Receiving the optical signal transmitted through the long-period lattice and outputting the optical signal as a frequency-modulated optical signal having a wavelength that changes at a rate of a modulation frequency f within a limited wavelength range; And Comprising a grid-based mixed gas measurement method comprising the step of calculating the concentration of each gas of the mixed gas through the frequency-modulated optical signal. The method of claim 7, wherein Calculating the concentration of each gas of the mixed gas through the frequency modulated optical signal Converting the frequency modulated optical signal into an electrical signal; Separating frequency components of the frequency modulated optical signal from the electrical signal; And Comprising the step of calculating the concentration of the gas through the separated electrical signal characterized in that the grid-based mixed gas measurement method. The method of claim 7, wherein The step of calculating the gas concentration of the mixed gas through the frequency-modulated optical signal may include calculating the concentration of the mixed gas by gas through the magnitude of the frequency-modulated optical signal. How to measure. In the optical sensor for measuring the concentration of the material constituting the mixed material, A light source for outputting an optical signal; A sensing unit including a long period grating coated with a material to receive an optical signal output from the light source and to output the long period grating transmission optical signal in which optical characteristics are changed by reacting the input optical signal with the mixed material; A signal processing unit including a short-period grating for inputting a long-period grating transmission optical signal output from the sensing unit to output a frequency-modulated optical signal having a wavelength varying within a wavelength range defined by the speed of the modulation frequency f; And And a concentration calculator configured to calculate a concentration for each material of the mixed material through the frequency-modulated optical signal. The method of claim 10, The concentration calculation unit A signal converter converting the frequency modulated optical signal into an electrical signal; And And a bandpass filter for separating frequency components of the frequency-modulated optical signal from the electrical signal. The method of claim 10, The minimum number of the detector A grating type optical sensor for measuring a mixed material, the same as the number of types of mixed materials to be measured. The method of claim 10, The sensing unit and the signal processing unit is a grid type optical sensor for measuring a mixed material, characterized in that formed in the optical waveguide. The method of claim 10, The concentration calculator is a grid-type optical sensor for measuring the mixed material, characterized in that for calculating the concentration for each material of the mixed material through the magnitude of the frequency-modulated optical signal. The method of claim 10, The grating-type optical sensor for measuring the mixed material, characterized in that the material for coating the long period grating is different depending on the type of material to be measured. In the method for measuring the concentration of a substance constituting the mixed substance, Outputting an optical signal; Receiving the optical signal and outputting the optical signal as a long-period lattice transmission optical signal in which optical characteristics are changed by reacting with the mixed material; Receiving the long period lattice transmission optical signal and outputting the long period lattice transmission optical signal as a frequency modulated optical signal having a wavelength varying at a rate of a modulation frequency f within a limited wavelength range; And Comprising a step of calculating the material-specific concentration of the mixed material through the frequency-modulated optical signal. The method of claim 16, Calculating the concentration of each substance of the mixed material through the frequency modulated optical signal Converting the frequency modulated optical signal into an electrical signal; Separating frequency components of the frequency modulated optical signal from the electrical signal; And Comprising the step of calculating the concentration of the material through the separated electrical signal characterized in that the grid-based mixed material measurement method. The method of claim 16, Computing the concentration of each material of the mixed material through the frequency-modulated optical signal, the grid-based mixed material, characterized in that for calculating the concentration of the mixed material material by the magnitude of the frequency-modulated optical signal How to measure.

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