KR101063337B1 - Fiber bragg grating sensing system using the multiplexer for multi-channel - Google Patents

Abstract

The present invention relates to an optical fiber Bragg grating (FBG) sensing system using a multi-channel multiplexer, and more particularly, a plurality of FBG sensors are molded into a secondary multi-channel of a multiplexer. By connecting the primary channel of the multiplexer to the optical wavelength meter, the radiated light emitted by the optical wavelength meter reaches the FBG sensor through the multiplexer, and the reflected light sensed and reflected by the FBG sensor is returned to the optical wavelength meter through the multiplexer. By returning, the optical wavelength value is measured, but the optical wavelength value is sent to the PC so that the PC recognizes the FBG sensor for each FBG sensor, thereby improving the accuracy and completely eliminating the error rate. It is about.

Description

FIBER BRAGG GRATING SENSING SYSTEM USING THE MULTIPLEXER FOR MULTI-CHANNEL}

The present invention relates to an optical fiber Bragg grating (FBG) sensing system using a multi-channel multiplexer. Specifically, a plurality of FBG sensors are molded into a secondary multi-channel of a multiplexer. By connecting the primary channel of the multiplexer to the optical wavelength meter, the radiation emitted by the optical wavelength meter reaches the FBG sensor through the multiplexer, and the reflected light sensed and reflected by the FBG sensor is returned to the optical wavelength meter through the multiplexer. By returning, the light wavelength value is measured. The optical wavelength measuring device does not distinguish which sensor the optical wavelength values reflected from each FBG sensor are measured, but the optical wavelength value is sent to a PC so that the PC recognizes each FBG sensor, and thus an optical fiber Bragg grating having high accuracy and low error rate Bragg Grating (FBG) is a multi-channel multiplexer using FBG sensing system.

The ship contains a myriad of tanks. In particular, crude oil or oil refining ships are used in cargo tanks for loading crude oil, ballast water tanks filled with water to maintain the equilibrium of ships, main engines and generator engines used for ship propulsion, and the like. It includes several types of tanks, such as fuel tanks in which fuel oil is stored.

In order for the ship to operate smoothly, it is necessary to know what level of liquid (crude oil, water, fuel, etc.) stored in the tank is. To this end, ships are equipped with sensors that can measure the liquid level, temperature, pressure, and the like. The values measured by the sensors are transferred to the ship's central control room for monitoring and an alarm is triggered if the measured values exceed the set values.

FBG sensor is currently used in many industrial fields because it is widely used in many industries, or one of the FBG sensors is connected in series between the FBG sensors. FBG sensors have the disadvantage of not being able to measure. In addition, the maximum number of sensors that can be connected in series is limited to 10-20.

Due to these shortcomings, FBG sensors have superior advantages over electrical and mechanical sensors in terms of their lifetime and performance, but they are not used in sensing systems that monitor and control a large number of sensors.

The present invention uses a multiplexer capable of star conncction rather than series connection, so that the optical wavelength measurement of the individual FBG sensors can be made independently, and the optical wavelength values thus measured are positioned for each sensor in the PC. By recognizing this, we provide a fiber Bragg grating sensing system using a multi-channel multiplexer using a high accuracy and low error rate Fiber Bragg Grating (FBG) sensor.

The present invention provides an optical wavelength measuring device that emits emitted light and receives reflected light, and measures an optical wavelength by analyzing a spectrum of the emitted light and the reflected light; And a plurality of FBG sensors that receive the radiation and generate reflected light at different refractive indices according to environmental variables, the optical fiber Bragg grating sensing system comprising: a plurality of FBG sensors connected to each of the plurality of FBGs by shaping; And a multiplexer for sequentially generating optical paths through which the radiated light and the reflected light are transmitted, corresponding to each sensor; and a measurement processor configured to measure and monitor the environmental variable based on the optical wavelength measured by the optical wavelength meter. The plurality of FBG sensors include a fiber Bragg grating sensing system using a multi-channel multiplexer, which further includes a reference FBG sensor for inducing the measurement processing unit to recognize a measurement start time.

The present invention of the optical fiber Bragg grating sensing system using the multi-channel multiplexer of the present invention enables the optical wavelength measurement by a multiplexer capable of star conncction rather than series connection. By recognizing the position of one optical wavelength per sensor in the PC, it increases the accuracy of the FBG (Fiber Bragg Grating) sensor and eliminates the error rate completely.

1 is a block diagram showing an optical fiber Bragg grating sensing system using an FBG sensor according to an embodiment of the present invention.
2 is a configuration diagram showing the FBG structure of the FBG sensor.
3 is a block diagram showing an optical fiber Bragg grating sensing system according to another embodiment of the present invention.
FIG. 4 is a block diagram illustrating the optical fiber Bragg grating sensing system of FIG. 3 in more detail.
5 is a timing diagram for describing an operation of the switching controller.

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for illustrating the present invention, and the scope of rights of the present invention is not limited by these embodiments.

1 is a block diagram illustrating an optical fiber Bragg grating sensing system using a FBG sensor connected in a cascade connection according to an embodiment of the present invention.

As shown in FIG. 1, the optical fiber Bragg grating sensing system emits radiation to a plurality of FBG sensors 1 and a plurality of FBG sensors 1 that generate reflected light at different refractive indices according to environmental variables. And a measurement processor 3 for measuring and monitoring environmental variables based on the optical wavelength measured by the optical wavelength meter.

The plurality of FBG sensors 1 are connected in series by an optical fiber cable. The FBG sensor 1 generates reflected light at different refractive indices according to environmental variables such as strain, temperature and pressure. The FBG sensor 1 is also called an optical fiber Bragg grating array sensor, and several fiber Bragg gratings are carved over a certain length on one strand of optical fiber and then reflected from each grating according to environmental variables such as temperature and intensity. It is a sensor using the characteristic that the wavelength of light varies. In general, germanium (Ge) is added to the optical fiber core to increase the refractive index than the cladding. When the ultraviolet ray is irradiated to the optical fiber core, the refractive index of the optical fiber is changed as the bonding structure of the germanium is deformed.

The FBG sensor 1 has the following advantages compared to electrical and mechanical sensors. First, there is no noise in the signal because there is no effect of electromagnetic induction. Therefore, the reliability and measurement accuracy of the measured value are very excellent. Second, up to 30 sensors can be cascaded to a single fiber. Therefore, many environmental variables can be measured. Third, the FBG sensor 1 may extend the measurement distance by 10 times or more than about several tens of kilometers compared to the electric sensor. Fourth, it is not affected by lightning strikes and can be used in high voltage and ferromagnetic environments. Fifth, it does not corrode, has high durability, and there is no risk of ignition, so it can be safely used in a hazardous area. Sixth, sensor life is semi-permanent, and sensor calibration that needs to be repeated every year is unnecessary. Seventh, the optical wavemeter 2 and the FBG sensors 1 are connected by fusion splicing with an optical fiber cable so that problems such as poor connection do not occur as compared with a wire. Because of these advantages, the optical fiber Bragg grating sensing system according to the present embodiment has higher accuracy and lower error rate than conventional electrical and physical sensors.

On the other hand, the optical wavelength measuring device (2) measures the optical wavelength by comparing the spectrum of the reflected light generated by the FBG sensor 1 and the radiation emitted by the radiation transmitted to the FBG sensor (1). To this end, the optical wavelength measuring unit 2 includes a light source for generating emitted light and a light receiving unit for receiving the reflected light.

The measurement processor 3 calculates the measurement result transmitted from the optical wavelength measuring instrument 2 and projects the environmental change on the monitor based on the measurement result. For this purpose, the measurement processing unit 3 includes a computer having excellent data processing capability.

2 illustrates an FBG structure of the FBG sensor 1. Referring to this, in the state where the cladding 12 surrounds the optical fiber core 11, a plurality of FBGs 13 are disposed on the optical fiber core 11. You can check it. The FBG 13 reflects only light having a wavelength satisfying the Bragg condition (15), and transmits light having other wavelengths (14).

The optical fiber Bragg grating sensing system according to the embodiment as described above can use the FBG sensor (1) rather than the electrical, mechanical sensor can measure the environmental parameters better.

On the other hand, in the optical fiber Bragg grating sensing system according to an embodiment, since the FBG sensors 1 are connected in series, when the FBG sensors 1 are disconnected, they cannot receive light from the optical wavelength meter 2 and reflect the reflected light. Cannot be transmitted to the optical wavelength meter 2. That is, the environmental parameters cannot be measured for the FBG sensor 1 disconnected from the optical wavelength measuring instrument 2. In addition, the existing optical wavelength meter (2) does not exceed a maximum of four channels. That is, the number of FBG sensors 1 is bound to be limited. Thus, another embodiment is proposed as follows.

3 is a block diagram showing an optical fiber Bragg grating sensing system according to another embodiment of the present invention. In this case, since the plurality of FBG sensors 101 are the same as in the previous embodiment, description thereof will be omitted.

As shown in FIG. 3, in the optical fiber Bragg grating sensing system, a plurality of FBG sensors 101 and a plurality of FBG sensors 101 which generate reflected light with different refractive indices according to environmental variables are connected to each other by molding and a plurality of FBG sensors. A multiplexer 102 sequentially generating optical paths corresponding to each of the optical waveguides 103 emits radiation to a plurality of FBG sensors 101 and receives reflected light generated by the FBG sensor 101 to measure an optical wavelength. And a measurement processor 104 for measuring and monitoring environmental variables based on the optical wavelength measured by the optical wavelength measuring instrument 103. Here, the optical wavelength measuring instrument 103 has a scan rate of 1000 Hz, and when power is transmitted, the optical wavelength measuring instrument 103 continuously transmits and receives light 1000 times per second, and measures the optical wavelength value measured 1000 times per second. Forward to 104. When the power is transmitted, the multiplexer 102 applies a control signal to an optical switch therein to form an optical path for passing the radiated light transmitted from the optical wavelength meter 103 and transmitting the reflected light to the optical wavelength meter 103 for 0 to 10 msec. . After 0 ~ 10msec elapses, the next optical path is formed, and this process is performed sequentially.

FIG. 4 is a block diagram illustrating the optical fiber Bragg grating sensing system of FIG. 3 in more detail. In this case, it is assumed that the optical fiber Bragg grating sensing system includes 32 FBG sensors 101. In practice, if an optical path is formed between 0 and 10 msec, 100 FBG sensors can be sensed in one second.

As shown in FIG. 4, the multiplexer 102 includes first to fifth switching units 1021 to 1025, a reference FBG sensor 1026, and a switching controller 1027. Here, the reference FBG sensor 1026 is a sensor for inducing the role of the initial identifier, that is, the optical wavelength measuring instrument 103 or the measurement processing unit 104 to recognize the position of the start sensor.

The first switching unit 1021 is connected in series with the optical wavelength measuring instrument 103 and is connected in a type with the second to fifth switching units 1022 to 1025. In addition, the first switching unit 1021 sequentially connects the optical paths between the optical wavelength meter 103 and each of the second to fifth switching units 1022 to 1025 under the control of the switching controller 1027. To this end, the first switching unit 1021 includes an optical switch.

The second switching unit 1022 is connected in series with the first switching unit 1021, and is molded in connection with the reference FBG sensor 1026 and FBG sensors 1 to FBG sensor 8. The second switching unit 1022 sequentially connects the optical paths between the first switching unit 1021, the reference FBG sensor 1026, and the FBG sensors 1 to FBG sensors 8 under the control of the switching control unit 1027. . To this end, the second switching unit 1022 includes an optical switch.

The third switching unit 1023 is connected in series with the first switching unit 1021, and is connected to the FBG sensors 9 to FBG sensors 16 by molding. The third switching unit 1023 sequentially connects the optical paths between the first switching unit 1021 and each of the FBG sensors 9 to FBG sensors 16 under the control of the switching controller 1027. To this end, the third switching unit 1023 includes an optical switch.

The fourth switching unit 1024 is connected in series with the first switching unit 1021, and is connected to the FBG sensors 17 to FBG sensors 24 by molding. The fourth switching unit 1024 sequentially connects the optical paths between the first switching unit 1021 and each of the FBG sensors 17 to FBG sensors 24 under the control of the switching controller 1027. To this end, the fourth switching unit 1024 includes an optical switch.

The fifth switching unit 1025 is connected in series with the first switching unit 1021, and is molded in connection with the FBG sensors 25 to FBG sensors 32. The fifth switching unit 1025 sequentially connects the optical paths between the first switching unit 1021 and each of the FBG sensors 25 to FBG sensors 32 under the control of the switching control unit 1027. To this end, the fifth switching unit 1025 includes an optical switch.

The switching controller 1027 activates the first to fifth control signals CONT1 <1: 4> to CONT5 <1: 8> according to a condition to provide the first to fifth switching units 1021 to 1025. To pass. In this case, the condition means that the optical wavelength measuring unit 103 and each of the FBG sensors 1 to FBG sensors 32 are controlled to individually form an optical path. That is, it means that the optical wavelength measuring unit 103 and the optical path of each of the FBG sensors 1 to FBG sensors 32 do not overlap. To this end, the switching control unit 1027 operates as follows.

The light wavelength measurer 103 includes a light source 1031 that emits radiated light, a light receiver 1032 that receives reflected light, and a spectrum comparator 1033 that compares the spectrum of the emitted light and the reflected light. The optical wavelength measuring instrument 103 includes one channel, and one channel of the optical wavelength measuring instrument 103 is connected to one multiplexer 102. The light source 1031 may be an LED or a laser, and the light receiver 1032 includes an interrogation module.

5 is a timing diagram for describing an operation of the switching controller 1027. In this case, it is assumed that the optical fiber Bragg grating sensing system measures only FBG sensors 1 to FBG sensors 8.

As shown in FIG. 5, the switching control unit 1027 connects the optical wavelength measuring instrument 103 with the optical paths of the reference FBG sensor 1026 and the FBG sensors 1 to FBG sensors 8 at the time of the first control signal. Enable bit CONT1 <1> to the high level. The switching controller 1027 deactivates the bits CONT1 <2: 4> of the first control signal to a low level. The first switching unit 1021, which receives the first bit CONT1 <1> of the activated first control signal, connects the optical wavelength detector 103 with the optical paths of the reference FBG sensor 1026 and FBG sensors 1 to FBG sensor 8. do.

The switching controller 1027 sequentially activates the high level from the first bit CONT2 <1> to the last bit CONT2 <8> of the second control signal at the time T1. In this case, the activation time of the last bit CONT2 <8> of the second control signal is preferably within the activation period of the first bit CONT1 <1> of the first control signal. Accordingly, the second switching unit 1022 sequentially connects the optical paths with the first switching unit 1021 and the optical wavelength meter 103 from the reference FBG sensor 1026 to the FBG sensor 8. At this time, the remaining control signals CONT3 <1: 8> to CONT5 <1: 8> are deactivated to a low level.

Table 1 below shows an identification method for recognizing the FBG sensors 1 to FBG sensors 32 in the measurement processing unit 104. In this case, the following Table 1 assumes that the optical path is formed for 10msec, and it is assumed that only the FBG sensors 1 to FBG sensor 8 are measured as in FIG. 5.

To the measurement processing unit 104
Data passed Measured
Sensor name
Contents Of the measurement processing unit 104
Identification method TIME 1 / 1000s VALUE (nm) 120000 000 0000.000 none The switching units 1021 to 1025 do not operate
No reflected light none 120000 010 1530.100 standard
FBG sensor
(1026) Between the light receiver 1032 and the reference FBG sensor 1026
Optical path formation Since the VALUE (1530.100) of the measured time (010) is within the VALUE (1529.000 to 1531.000) of the preset start range, it is recognized that the measurement starts from the measured time (010). 120000 020 1540.500 FBG Sensor 1 Between the light receiving unit 1032 and the FBG sensor 1
Optical path formation The reflected light input between 11 and 20 msec from the time when the start of measurement is recognized is recognized as the FBG sensor 1 reflected light. 120000 030 1538.200 FBG Sensor 2 Between the light receiving unit 1032 and the FBG sensor 2
Optical path formation The reflected light input between 21 and 30 msec from the time when the measurement is started is recognized as the FBG sensor 2 reflected light. 120000 040 1543.300 FBG sensor 3 Between the light receiving unit 1032 and the FBG sensor 3
Optical path formation The reflected light input between 31 and 40 msec is recognized as the FBG sensor 3 reflected light. 120000 050 1540.500 FBG sensor 4 Between the light receiving unit 1032 and the FBG sensor 4
Optical path formation The reflected light input between 41 and 50 msec is recognized as the FBG sensor 4 reflected light from the time when the start of measurement is recognized. 120000 060 1538.200 FBG sensor 5 Between the light receiving unit 1032 and the FBG sensor 5
Optical path formation The reflected light input between 51 and 60 msec is recognized as the FBG sensor 5 reflected light from the time when the start of measurement is recognized. 120000 070 1543.300 FBG Sensor 6 Between the light receiving unit 1032 and the FBG sensor 6
Optical path formation The reflected light input between 61 and 70 msec from the time when the start of measurement is recognized is recognized as the reflected light of FBG sensor 6. 120000 080 1540.500 FBG Sensor 7 Between the light receiving unit 1032 and the FBG sensor 7
Optical path formation The reflected light input between 71 and 80 msec from the time when the start of measurement is recognized is recognized as the reflected light of FBG sensor 7. 120000 090 1538.200 FBG Sensor 8 Between the light receiving unit 1032 and the FBG sensor 8
Optical path formation The reflected light input between 81 and 90 msec from the time when the start of measurement is recognized is recognized as the reflected light of FBG sensor 8.

Referring to [Table 1], the measurement processing unit 104 sets the VALUE in advance, and recognizes that the measurement of the reference FBG sensor 1026 is performed when the measured VALUE exists within the set VALUE range. That is, the measurement starts. Subsequently, the measurement of the FBG sensor 2 is performed for 10 msec from the time when the start of the measurement is recognized, and the measurements of the remaining FBG sensors 3 to FBG sensor 8 are sequentially performed for 10 msec.

In summary, the optical fiber Bragg grating sensing system according to another embodiment of the present invention uses an FBG sensor. Compared to electrical and mechanical sensors, the FBG sensor has no effect of electromagnetic induction, so there is no noise in the signal, and up to 30 sensors can be cascaded to a single fiber, so that many environmental variables can be measured. In addition, the FBG sensor can extend the measuring distance 10 times or more than about tens of kilometers compared to the electric sensor, and is free from the effects of lightning and can be used in high voltage and ferromagnetic environments. There is no risk, so it can be used safely in explosion-proof area. In addition, the sensor life is semi-permanent, and the sensor correction that is repeated every year is unnecessary, and the connection between the optical wavelength measuring device and the FBG sensors is fusion-spliced with an optical fiber cable, so that problems such as poor connection do not occur. Because of these advantages, the optical fiber Bragg grating sensing system according to the present embodiment has higher accuracy and lower error rate than conventional electrical and physical sensors.

Further, because of the multiplexer, the FBG sensor is molded into the optical wavelength measuring device so that even if one FBG sensor fails or is disconnected, the remaining FBG sensor operates normally. Therefore, compared with the prior art, the optical fiber Bragg grating sensing system of the present embodiment has a significantly low error occurrence rate. In addition, the measurement processor recognizes the measurement start time through the reference FBG sensor, and subsequently recognizes the FBG sensors sequentially through time division.

The optical fiber Bragg grating sensing system of the present embodiment can be connected to more FBG sensors than the conventional one through a multiplexer, even using a conventional optical wavelength meter. As described above, the current optical wavelength meter is connected to the FBG sensor in up to four channels. In this process, FBG sensors were connected in series in order to be connected to more FBG sensors. Therefore, in case of disconnection in the middle, many FBG sensors were inoperative. However, in the optical fiber Bragg grating sensing system of the present embodiment, since the multiplexer is disposed in one channel of the optical wavelength meter, and the multiplexer is connected to a large amount of FBG sensors depending on the arrangement of the switching unit, the channel limit of the optical wavelength meter is overcome.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill.

101: FBG sensor 102: multiplexer
103: light wavelength measuring instrument 104: measurement processing unit

Claims (7)

An optical wavelength measuring device for emitting emitted light and receiving reflected light, and measuring an optical wavelength by analyzing a spectrum of the emitted light and the reflected light; In the optical fiber Bragg grating sensing system comprising: a plurality of FBG sensors for receiving the emitted light to generate reflected light at different refractive indices according to environmental variables,
A multiplexer connected to each of the plurality of FBG sensors by molding and sequentially generating an optical path through which the radiated light and the reflected light are transmitted corresponding to each of the plurality of FBG sensors; and
And a measurement processor configured to measure and monitor the environmental variable based on the optical wavelength measured by the optical wavelength measuring instrument.
The plurality of FBG sensors further comprises a reference FBG sensor for inducing the measurement processing unit to recognize the measurement start time, the optical fiber Bragg grating sensing system using a multi-channel multiplexer.
The method of claim 1,
The optical wavelength measuring device includes a channel through which the radiated light and the reflected light are transmitted, and the channel is connected to the multiplexer in series, wherein the optical fiber Bragg grating sensing system using the multiplexer for multiple channels.
delete delete The method of claim 1,
The measurement processing unit recognizes that the measurement is performed by the reference FBG sensor when the first measurement is within a preset measurement range, and subsequently performs the measurement on the remaining FBG sensors sequentially. Optical Fiber Bragg Grating Sensing System.
The method of claim 1,
The multiplexer
A first switching connected in series with the optical wavelength measuring instrument and in a shaping manner with the second to fifth switching portions, and forming an optical path between the optical wavelength measuring instrument and the second and third switching portions in response to a first control signal; part;
The first switching unit and the reference FBG sensor and the FBG sensor are connected in series with the first FBG sensor and the FBG sensor 1 to FBG sensor 8 in a molded form, and sequentially in response to a second control signal. A second switching unit forming an optical path with each of 1 to FBG sensors 8;
An optical path between the first switching unit and the FBG sensors 9 to FBG sensor 16 is sequentially connected to the first switching unit, and is connected to the FBG sensors 9 to FBG sensors 16 in a shaping manner, and sequentially in response to a third control signal. A third switching unit forming a; And
And a switching controller for activating the first to third control signals sequentially activated over time.
The method according to claim 6,
The optical fiber Bragg grating sensing system using a multi-channel multiplexer, characterized in that the first to third switching unit comprises an optical switch.

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