KR101195596B1 - Detecting System for Physical Quantity of Structure - Google Patents

Abstract

The present invention is a measurement system for real-time monitoring of physical changes such as temperature, strain, etc. of large structures (tunnels, bridges, buildings, etc.) by using light that is not affected by electromagnetic waves, as a light source, optical fiber Bragg grating sensor, and light water. It consists of a system including a light source control unit for optical frequency modulation and generation of optical pulses, and an optical filter for measuring and correcting optical frequencies. The measurement system of this configuration can maintain the accuracy of the measured value even when the temperature changes in the external environment, so that the constant monitoring of the physical quantity change is possible, and the sensor maintains the center wavelength of the Bragg grating sensor within 1 nm and the plurality are in series. Since the fiber optic Bragg grating sensor is used, it is easy to manufacture and install the sensor and has a low cost effect.

Description

Detecting System for Physical Quantity of Structure}

The present invention relates to a measurement system for real-time monitoring of physical changes such as temperature, strain, and the like of large structures (tunnels, bridges, buildings, etc.) using light that is not affected by electromagnetic waves. In general, this is a system using a signal processing method used in OTDR (OPTICAL TIME DOMAIN REFLECTOMETER) that can measure the abnormality such as damage of optical communication network.

Prior arts include the DISTRIBUTED MULTIPLEEXED OPTICAL FIBER BRAGG GRATING SENSOR ARRANGEEMENT (A) in the United States and the fire detection system using an optical fiber Bragg grating sensor (B, application number: KR 10-2003-0002842).

A technology illustrates an external resonator type laser consisting of a laser diode and a variable Bragg grating to implement a tunable pulsed light source. However, such a light source has a disadvantage in that the accuracy of the oscillation wavelength is not good and even includes an instability of the output wavelength due to mode hopping. Therefore, there is a disadvantage in that the specific oscillation wavelength is not reliable and the determination of the central wavelength variation of the FBG sensor is limited depending on the magnitude of the stress applied to the variable FBG.

On the other hand, B technology uses a laser diode as a light source and intends to apply it to a fire detection system based on the determination of the amount of change in wavelength of light reflected from a FBG of a specific wavelength. However, even in this case, the sensitivity of the sensor was limited due to the lack of a means for measuring the accurate wavelength of the tunable pulsed light source.

An object of the present invention for solving the above-described conventional problems, by using a semiconductor laser diode as a light source, by continuously and repeatedly controlling the temperature of the laser diode to continuously change the oscillation wavelength of the light source to measure a stable optical frequency modulation To provide a system.

In addition, by providing an optical filter as a means for precisely identifying the wavelength of the continuously changing light source, it is possible to improve the wavelength accuracy of the tunable pulsed light source to improve the sensitivity and accuracy of physical quantity measurement using the optical fiber Bragg grating sensor. To provide a system.

Structure physical quantity measurement system according to the present invention for solving the above-described conventional problems and solves the object according to the present invention, in the measurement system for measuring the physical quantity of the structure using a plurality of optical fiber Bragg grating sensor, the laser diode is a light source A light source control unit including a temperature controlled wavelength modulation device for modulating the optical frequency of the light source through temperature control and a pulse generator for generating an output of the light source in a pulse form; A temperature controller for maintaining a temperature of a light frequency modulated light source through the temperature control within a specific condition; An optical receiver including a photo detector therein for detecting the optical signal; An optical filter for improving the sensitivity of the Bragg grating sensor and the accuracy of the measured physical quantity: and measuring the physical variation of the measurement point through the analysis of the optical signal that is incident on the Bragg grating sensor and returned to the Bragg grating sensor And an optical signal control and detection unit, wherein the optical signal control and detection unit reflects a wavelength of an optical pulse output from the light source to a plurality of pulse-shaped optical signals that are reflected by the sensor and reach the optical receiver. Analyzing based on time, the center wavelength change of the Bragg grating sensor is calculated, and the wavelength value of the optical pulse output from the light source is measured and corrected.
In the structure physical quantity measurement system of the present invention, it is characterized in that it further comprises an optical switch for using a multi-path Bragg grating sensor.
In addition, the structure physical quantity measurement system of the present invention is a measurement system for measuring a physical quantity using a plurality of optical fiber Bragg grating sensor, the temperature control type that modulates the optical frequency of the light source through the temperature control, the laser diode as a light source A light source controller including a wavelength modulator and a pulse generator for generating an output of the light source in a pulse form; A temperature controller for maintaining a temperature of a light frequency modulated light source through the temperature control within a specific condition; An optical receiver including a photo detector therein for detecting the optical signal; An optical filter for improving the sensitivity of the Bragg grating sensor and the accuracy of the measured physical quantity: and measuring the physical variation of the measurement point through the analysis of the optical signal that is incident on the Bragg grating sensor and returned to the Bragg grating sensor And a device for measuring and correcting a wavelength value of an optical pulse output from a light source and a temperature maintaining device for maintaining a temperature of the temperature controlled wavelength modulator within a specific condition. And the sensors connected to the system are a plurality of Bragg grating sensors connected in series with a center wavelength within 1 nm.
In the structure physical quantity measurement system of the present invention, the Bragg grating sensor has a reflectance of 1% or less.
In the structure physical quantity measurement system of the present invention, the light source and the Bragg grating sensor is configured in plural to improve the spatial resolution and increase the measurement point of the measurement system, the light of the plurality of wavelengths is multi-wavelength using a multi-wavelength coupling The Bragg grating sensor has a plurality of center wavelengths having different center wavelengths, and the center wavelength range of each wavelength type is within 1 nm and between Bragg grating sensors having the same wavelength type. Has a structure in which Bragg grating sensors having different wavelength types are inserted in a space, and the light receiving unit is configured to detect an optical signal reflected from each Bragg grating sensor for each wavelength type to improve spatial resolution. It is characterized in that.
In the structure physical quantity measurement system of the present invention, in the optical signal control and detection unit, the wavelength and the arrival time of the optical pulse outputted from the light source are a plurality of pulse-shaped optical signals that are reflected by the Bragg grating sensor and reach the optical receiver. It is characterized by calculating the central wavelength change of the Bragg grating sensor by measuring based on and measuring and correcting the wavelength value of the optical pulse output from the light source.

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As described above, in the case of the measurement system according to the present invention, the physical quantity (temperature, strain) can be measured for a wide distribution of a large structure (tunnel, bridge, building, etc.) using light that is not affected by electromagnetic waves. It is possible to maintain the accuracy of the measured values even when the temperature changes in the external environment, allowing constant monitoring of changes in physical quantities.

In addition, the sensor maintains the center wavelength of the Bragg grating sensor within 1 nm and uses a plurality of fiber Bragg grating sensors connected in series, making it easy to manufacture and install the sensor and low cost.

1 is a configuration of a system for measuring physical quantity by analyzing an optical signal in a method similar to that used in a time domain light reflectometer using a plurality of Bragg grating sensors connected in series having a low reflectance and a central wavelength of 1 nm or less Degree.
2 is a system configuration for connecting a multi-path Bragg grating sensor in the present invention.
FIG. 3 is a system diagram to which a light source and Bragg grating sensor composed of plural kinds of wavelengths are used to improve spatial resolution and measurement point in the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1 is a configuration of a system for measuring physical quantity by analyzing an optical signal in a method similar to that used in a time domain light reflectometer using a plurality of Bragg grating sensors connected in series having a low reflectance and a central wavelength range of 1 nm or less 2 is a diagram illustrating a system configuration for connecting a multi-path Bragg grating sensor in the present invention, and FIG. 3 is a system in which a light source and a Bragg grating sensor composed of a plurality of wavelengths are used to improve spatial resolution and measurement point in the present invention. It is a block diagram.

1 shows a system for measuring physical quantities (temperature, strain) using a plurality of optical fiber Bragg grating sensors connected in series.

Here, the optical fiber Bragg grating sensor 180 serves to reflect light of a specific wavelength and according to the physical change applied to the sensor 180, the wavelength of the light reflected from the sensor 180, that is, of the Bragg grating sensor 180. The center wavelength changes, and this characteristic is used to measure physical quantities.

The configuration of the measurement system includes a fiber Bragg grating sensor 180, a laser diode used as the light source 140, and a temperature modulation of the light source 140, in which a plurality of sensors having a reflectance of less than 1% and a center wavelength within 1 nm range are connected in series. And a light source controller 110 for generating pulses, a light receiver 155, and a system 100 for signal processing.

In addition, the light source < RTI ID = 0.0 > control section 110 < / RTI > It is divided into two parts of the pulse generator 125 to generate.

In addition, it is preferable to further configure the temperature control unit 130 to ensure the stability of the optical frequency modulation even in the temperature change of the external environment, the optical filter for improving the sensitivity of the sensor 180 and the accuracy of the measured physical quantity Using 170, the optical frequency of the light pulses output from the light source 140 may be measured and corrected using the control and signal detection system 100.

That is, the optical receiver 155 including the photo detector 150 therein and the optical signal in the form of a plurality of pulses reflected by the sensor 180 and reaching the optical receiver 155 to detect the optical signal are included in the light source. Based on the wavelength and the arrival time of the light pulse output from the 140, the central wavelength change of the sensor 180 is calculated by the control and signal detection system 100, and is output from the light source 140 using the optical filter. The wavelength measurement and correction of the optical pulses are performed, and the optical frequency-modulated optical pulses are incident on the Bragg grating sensor 180 to measure the amount of physical change at a specific position by analyzing the signal of the optical pulses coming back.

The measurement principle is to inject the optical frequency-modulated light pulses into the Bragg grating sensor 180 and to measure the change in wavelength of the light pulses output from the light source 140 and the temporal arrival and intensity change of the light pulses reflected from the sensor 180 and returned. It measures the physical quantity at the point where the sensor is located by measuring and analyzing it.

That is, the optical frequency modulated optical pulse is incident on the Bragg grating sensor 180 to measure the physical change amount of the measuring point through the analysis of the optical signal returned and the temperature control for the stability of the optical frequency modulation according to the temperature change in the external environment. The optical filter 170 is added to improve the reliability and measurement sensitivity of the measured value by adding a portion and securing optical frequency accuracy of the optical pulse output from the light source 140.

 2 is a structure for measuring physical quantity using the Bragg grating sensor 180 composed of multiple light paths.

In this case, the optical switch 190 is added to configure the connection with the Bragg grating sensor 180 in multiple channels.

3 shows a measurement system consisting of a light source 140 and a Bragg grating sensor 180 having two kinds of wavelengths.

In order to increase the measuring point, the light source 140 and the Bragg grating sensor 180 are configured with a plurality of wavelengths. In this case, the Bragg grating sensor 180 has a structure in which Bragg grating sensors 180 of different wavelength types are inserted in the space between the Bragg grating sensors 180 having the same wavelength type.

At this time, the optical fiber Bragg grating sensor 180 is located in the space alternately FBG 1 and FBG 2, the distance between the FBG 1 sensor and the FBG 2 sensor should be more than the minimum unit of the resolution of the measurement system.

Therefore, the distance between FBG 1 sensors should be more than the minimum unit of system resolution. If FBG 2 is located between FBG 1 sensors and the distance between FBG 2 sensors is installed at a distance greater than the minimum resolution, the resolution and the measurement point of the system will be doubled. Will increase. That is, FBG 1 and FBG 2 are located at intervals of 1/2 the distance of the minimum resolution distance of the measurement system.

The light receiver 155 is configured to detect the optical signals reflected from each Bragg grating sensor 180 for each wavelength type, and analyzes the signals of the optical pulses returned from each sensor 180 for each wavelength. Summing up the measured results increases spatial resolution and measurement points compared to the case of using a single wavelength light source and Bragg grating sensor 180.

That is, the light pulses generated from the light source 140 of the plurality of wavelengths are combined into one light path through the multi-wavelength coupling component and are incident on the plurality of Bragg grating sensors 180 configured of the multiple wavelengths.

In the system according to the present invention, the light pulses output from the light source 1 are only reflected by the FBG 1 to reach the photodetector 1, and the light pulses output from the light source 2 are only reflected at the FBG 2 to reach the photodetector 2. At this time, the wavelength change of the light pulse generated in each light source and the temporal arrival and intensity change of the light pulse reflected from FBG 1 and FBG 2 and returned to each light receiving unit are measured and the results are merged.

As described above, in the present invention, the semiconductor laser diode is used as a light source, and the temperature of the light source is added for stable optical frequency modulation by continuously changing the oscillation wavelength of the light source by continuously and repeatedly controlling the temperature of the laser diode. It was. In addition, by providing an optical filter as a means for precisely identifying the wavelength of the continuously changing light source, the wavelength accuracy of the tunable pulsed light source is improved to obtain the effect of improving the sensitivity and accuracy for physical quantity measurement using the optical fiber Bragg grating sensor. Can be.

As described above, although the present invention has been described by way of limited embodiments and drawings, the terms or words used in the present specification and claims are not to be construed as being limited to ordinary or dictionary meanings, and are consistent with the technical spirit of the present invention. It must be interpreted as meaning and concept. Therefore, the embodiments described in the specification and the configuration shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical idea of the present invention, various equivalents that may be substituted for them at the time of the present application It should be understood that there are water and variations.

100: light signal control and detection unit 110: light source control unit
120: temperature controlled wavelength modulator 125: pulse generator
130: temperature control unit 140: light source 150: photodetector 155: light receiving unit 170: optical filter 180: Bragg grating sensor
190: optical switch 300: DeMUX

Claims (6)

In the measurement system for measuring the physical quantity of the structure using a plurality of optical fiber Bragg grating sensor,
A light source controller comprising a laser diode as a light source, a temperature controlled wavelength modulator for modulating the optical frequency of the light source through temperature control, and a pulse generator for generating an output of the light source in a pulse form;
A temperature controller for maintaining a temperature of a light frequency modulated light source through the temperature control within a specific condition;
An optical receiver including a photo detector therein for detecting the optical signal;
An optical filter for improving the sensitivity of the Bragg grating sensor and the accuracy of the measured physical quantity; And
And an optical signal control and detection unit configured to measure an amount of physical change of a measurement point by analyzing an optical signal that is incident on the Bragg grating sensor by returning an optical frequency-modulated optical pulse to the Bragg grating sensor.
The optical signal control and detection unit analyzes a plurality of pulse-shaped optical signals that are reflected by the Bragg grating sensor and arrive at the light receiving unit based on the wavelength and the arrival time of the optical pulses output from the light source. A physical quantity measurement system for a structure comprising calculating a central wavelength change and measuring and correcting a wavelength value of an optical pulse output from a light source. The method of claim 1,
Structure physical quantity measurement system further comprises an optical switch for using a multi-path optical fiber Bragg grating sensor In the measurement system for measuring a physical quantity using a plurality of optical fiber Bragg grating sensor,
A light source controller comprising a laser diode as a light source, a temperature controlled wavelength modulator for modulating the optical frequency of the light source through temperature control, and a pulse generator for generating an output of the light source in a pulse form;
A temperature controller for maintaining a temperature of a light frequency modulated light source through the temperature control within a specific condition;
An optical receiver including a photo detector therein for detecting the optical signal;
An optical filter for improving the sensitivity of the Bragg grating sensor and the accuracy of the measured physical quantity; And
And an optical signal control and detection unit configured to measure an amount of physical change of a measurement point by analyzing an optical signal that is incident on the Bragg grating sensor by returning an optical frequency-modulated optical pulse to the Bragg grating sensor.
A device for measuring and correcting the wavelength value of the optical pulse output from the light source and a temperature maintaining device for maintaining the temperature of the temperature controlled wavelength modulator within a specific condition,
The Bragg grating sensor connected to the system is a plurality of Bragg grating sensors connected in series with a center wavelength within 1 nm. The method of claim 3, wherein
The reflectivity of the Bragg grating sensor is less than 1% structure physical quantity measurement system, characterized in that. The method of claim 3, wherein
The light source and Bragg grating sensor is composed of a plurality for improving the spatial resolution of the measurement system and the increase of the measurement point,
The light of the plurality of wavelengths is incident on a plurality of Bragg grating sensors composed of multiple wavelengths by using a multi-wavelength coupling,
The Bragg grating sensor has a plurality of types of center wavelengths having different center wavelengths, and a Bragg grating sensor having different wavelength types between Bragg grating sensors having the same wavelength type within the center wavelength range of each wavelength type is within 1 nm. It has a structure inserted into
And the optical receiver is configured to detect the optical signal reflected from each Bragg grating sensor for each wavelength type to improve spatial resolution. 6. The method according to any one of claims 3 to 5,
The optical signal control and detection unit analyzes a plurality of pulse-shaped optical signals that are reflected by the Bragg grating sensor and arrive at the light receiving unit based on the wavelength and the arrival time of the optical pulses output from the light source. A physical quantity measurement system for a structure comprising calculating a central wavelength change and measuring and correcting a wavelength value of an optical pulse output from a light source.

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