Er-doped fiber-based high-sensitivity temperature detection device and detection method

Abstract

The invention discloses a high-sensitivity temperature detection device and method based on an Er-doped fiber, and the device comprises a light source output module, a first Er-doped fiber, a second Er-doped fiber, a first wavelength division multiplexing module, a second wavelength division multiplexing module, a photoelectric detector, and a signal processing module. The first erbium-doped optical fiber generates a first fluorescence signal for temperature detection; the second erbium-doped optical fiber generates a second fluorescence signal for temperature detection; the first erbium-doped fiber and the second erbium-doped fiber are different in length, the length of the first erbium-doped fiber meets the requirement that the fluorescence lifetime of the erbium-doped fiber is reduced along with temperature rise, and the length of the second erbium-doped fiber meets the requirement that the fluorescence lifetime of the erbium-doped fiber is increased along with temperature rise. Difference is carried out on light-emitting signals of the two erbium-doped optical fibers with different lengths, higher temperature detection sensitivity is obtained, and the higher temperature detection sensitivity is achieved on the premise that the system cost is controlled compared with a traditional erbium-doped optical fiber fluorescence temperature sensing system.

Description

Technical Field

[0001] The present invention relates to a highly sensitive fiber optic fluorescence temperature detection device and detection method based on erbium-doped fiber, which are used for daily temperature detection in scenarios such as transformers, windings, and switch cabinets in the power industry, to achieve the green and healthy development of industry and ensure the safety of people's lives and property. The device utilizes the characteristic that the response curves of the lifetimes of different lengths of erbium-doped fiber to temperature are different due to the different proportions of non-radiative transitions during the luminescence process, to achieve highly sensitive detection of temperature. Background Art

[0002] In the modern industrial field, the progress of temperature monitoring technology is crucial for ensuring equipment safety and improving operation efficiency. Especially in the power industry, the temperature monitoring of equipment such as transformers, windings, and switch cabinets is directly related to the stability and safety of the equipment. At present, although traditional temperature sensors are widely used, they have certain limitations in terms of high sensitivity and rapid response. In recent years, lifetime-based fiber optic fluorescence temperature sensors have received extensive attention due to their unique working principles and superior performance. As a new type of temperature sensing material, erbium-doped fiber has a close relationship between its luminescence characteristics and temperature changes. By utilizing the response characteristics of the proportion of non-radiative transitions changing with temperature, highly sensitive detection of temperature can be achieved. The advantage of this technology is that it can work stably under high temperatures and complex environments, and at the same time has strong anti-electromagnetic interference ability. This enables erbium-doped fiber fluorescence temperature sensors to perform excellently in the monitoring of power equipment, being able to detect potential overheating risks in a timely manner, thereby preventing safety hazards such as equipment failures and fires. In addition, with the development of industrial intelligence, the requirements for the accuracy and real-time performance of temperature monitoring are gradually increasing. The application of lifetime-based fiber optic fluorescence temperature sensors can not only improve the monitoring accuracy but also provide an important basis for realizing the intelligent management of industrial equipment. Currently, although this technology is still in the research and development stage, its application prospect in the power industry is broad. Through continuous technological innovation and optimization, this new type of temperature sensor is expected to play a greater role in future industrial applications, promoting the green and healthy development of industry and ensuring the safety of people's lives and property. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a highly sensitive fiber optic fluorescence temperature detection device and detection method for improving the sensitivity of a lifetime-based fiber optic fluorescence temperature detection system.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention first provides a highly sensitive fiber optic fluorescence temperature detection device based on erbium-doped fiber, comprising:

[0006] A light source output module for outputting pump light;

[0007] The first erbium-doped fiber is used to generate a first fluorescence signal for temperature detection under the excitation of pump light; the second erbium-doped fiber is used to generate a second fluorescence signal for temperature detection under the excitation of pump light; the lengths of the first erbium-doped fiber and the second erbium-doped fiber are different, and the length of the first erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber decreases with the increase of temperature, and the length of the second erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber increases with the increase of temperature;

[0008] The first wavelength division multiplexing module is used to separate the required first optical signal from the first fluorescence signal;

[0009] The second wavelength division multiplexing module is used to separate the required second optical signal from the second fluorescence signal;

[0010] The photodetector converts the first optical signal separated by the first wavelength division multiplexing module into a first digital signal and outputs it, and converts the second optical signal separated by the second wavelength division multiplexing module into a second digital signal and outputs it;

[0011] The signal processing module performs signal processing on the first digital signal output by the photodetector to obtain a first fluorescence lifetime, and performs signal processing on the second digital signal output by the photodetector to obtain a second fluorescence lifetime; performs a difference on the first fluorescence lifetime and the second fluorescence lifetime, and obtains the temperature to be measured according to the difference component.

[0012] The lengths of the first erbium-doped fiber and the second erbium-doped fiber are determined as follows:

[0013] Determine the critical length L0 at which the fluorescence lifetime is related to the doping concentration of the erbium-doped fiber;

[0014] Set the length of the first erbium-doped fiber to be shorter than the critical length L0;

[0015] Set the length of the second erbium-doped fiber to be greater than L0.

[0016] The light source output module includes a signal generator and a laser. The signal generator generates a square wave pulse signal according to the set output frequency and amplitude and sends it to the laser. The laser generates a pump light pulse under the drive of the signal generator.

[0017] The light source output module further includes an optical fiber coupler. The optical fiber coupler is used to divide the pump light pulse generated by the laser into two beams and output them. One beam is output to the first wavelength division multiplexing module, and the other beam is output to the second wavelength division multiplexing module.

[0018] Both the first wavelength division multiplexing module and the second wavelength division multiplexing module are 980 / 1550 wavelength division multiplexers. The 980 / 1550 wavelength division multiplexer filters the pump light, and then the two optical signals respectively reach the first erbium-doped fiber and the second erbium-doped fiber.

[0019] In the signal processing module, the processing methods for processing digital signals to obtain fluorescence lifetimes include the fitting method, the fast Fourier transform method, and the phase method.

[0020] The present invention also provides a highly sensitive fiber optic fluorescence temperature detection method based on erbium-doped fiber, including:

[0021] Using two erbium-doped fibers with different lengths as two detection units, where the length of one erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber decreases with the increase of temperature, and the length of the other erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber increases with the increase of temperature; obtaining the fluorescence detection signals emitted by the two detection units;

[0022] Processing the two fluorescence detection signals respectively to obtain two fluorescence lifetimes;

[0023] Performing differential processing on the two obtained fluorescence lifetimes to obtain a difference component;

[0024] Obtaining the temperature to be measured according to the difference component.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] In the temperature detection device of the present invention, the first erbium-doped fiber and the second erbium-doped fiber with different lengths are selected. The length of the first erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber decreases with the increase of temperature, and the length of the second erbium-doped fiber satisfies that the fluorescence lifetime of the erbium-doped fiber increases with the increase of temperature; performing differential processing on the two sets of fluorescence lifetimes obtained after data processing, then due to the different non-radiative transition ratios, the values of their fluorescence lifetimes will be different, resulting in different temperature-lifetime response curves for erbium-doped fibers with different lengths. Performing differential processing on the two sets of fluorescence lifetimes, then the difference component is negatively correlated with the temperature and the sensitivity of the difference component to temperature changes is much greater than that of the ordinary single-ended fluorescence lifetime temperature sensing method. Description of the Drawings

[0027] Figure 1 It is the system connection diagram of the detection device of the present invention;

[0028] Figure 2 It is the graph of the temperature measurement sensitivity changing with the length of the erbium-doped fiber;

[0029] Figure 3 It is the graph of the temperature measurement result of the fluorescence lifetime of the shorter erbium-doped fiber;

[0030] Figure 4 It is the graph of the temperature measurement result of the fluorescence lifetime of the longer erbium-doped fiber;

[0031] Figure 5 It is the graph of the temperature measurement example result of the differential fluorescence lifetime. Detailed Embodiments

[0032] The following further describes in detail the specific embodiments of the present invention in conjunction with the accompanying drawings. The following embodiments are used to illustrate the present invention, but the protection scope of the present invention should not be limited thereby.

[0033] Figure 1 It is an overall schematic diagram of a high-sensitivity fiber fluorescence temperature detection device based on erbium-doped fiber provided in this embodiment. Taking erbium-doped fiber as an example, this embodiment provides a lifetime-type fiber fluorescence temperature detection device based on a dual optical path. The connection relationships of each device are as follows:

[0034] The output end of the signal generator 9 is connected to the laser 1, the output end of the laser 1 is connected to the fiber coupler 2, the two output ends of the fiber coupler 2 are respectively connected to the 980 / 1550 nm wavelength division multiplexer 3 and the 980 / 1550 nm wavelength division multiplexer 5. The common ends of the 980 / 1550 nm wavelength division multiplexer 3 and the 980 / 1550 nm wavelength division multiplexer 5 are connected to two erbium-doped fibers 4 and 6 with different lengths. The 1550 nm output ends of the 980 / 1550 nm wavelength division multiplexer 3 and the 980 / 1550 nm wavelength division multiplexer 5 are both connected to the photodetector 7. The photodetector 7 converts the signal into a digital signal to be measured and inputs it into the computer 8. The signal to be measured is processed in the computer 8 and then the result is output.

[0035] The length of the erbium-doped fiber 4 satisfies that the fluorescence lifetime of the erbium-doped fiber decreases with the increase of temperature, and the length of the erbium-doped fiber 6 satisfies that the fluorescence lifetime of the erbium-doped fiber increases with the increase of temperature.

[0036] The fluorescence lifetime of the erbium-doped fiber is determined by both the radiative transition lifetime and the non-radiative transition lifetime. The change in the proportion of non-radiative transitions caused by the length of the erbium-doped fiber during the luminescence process will affect the magnitude of the fluorescence lifetime and its temperature sensitivity. As shown in the attached Figure 2 figure, the fluorescence lifetime of the highly doped erbium-doped fiber shows a non-linear change trend with the length of the erbium-doped fiber. There is a critical length L0 = 64 cm related to the doping concentration of the erbium-doped fiber. When the length of the erbium-doped fiber used is shorter than the critical length L0 (0 < L < 64 cm), the fluorescence lifetime of this section of the erbium-doped fiber decreases with the increase of temperature, while for the erbium-doped fiber with a length greater than L0 (64 cm < L < 500 cm), the fluorescence lifetime will increase with the increase of temperature. Taking the difference between the fluorescence lifetimes of two erbium-doped fibers with different lengths will greatly increase the detection sensitivity of its lifetime-temperature.

[0037] The specific implementation method has the following steps:

[0038] Step 1: Select the corresponding pump laser according to the type of doped fiber, and the central wavelength of the absorption spectrum is λ;

[0039] Step 2: Use a signal generator to generate a low-frequency pulse wave to drive the laser, so that the laser outputs a pump square wave with a wavelength of λ; the frequency, duty cycle, and amplitude of the waveform should be appropriately selected according to the characteristics of the selected fluorescent material and the driving requirements of the laser;

[0040] Step 3: Use a fiber optic coupler with a 50% / 50% ratio to equally divide the pump light into two paths, and ensure that the pump light with equal power in the two paths is respectively incident on the pump light input end of the wavelength division multiplexer for filtering;

[0041] Step 4: Connect two erbium-doped fibers with different lengths to the common end of the wavelength division multiplexer; taking the path with the shorter erbium-doped fiber as an example, after the erbium-doped fiber is excited by the pump light, it emits a fluorescence decay signal with the same frequency as the pump light signal but different intensities and phases. After filtering by the wavelength division multiplexer, a single-wavelength fluorescence decay signal is output. This fluorescence signal can be expressed as:

[0042] I(t) = I0 exp(-t / τ)

[0043] where I(t) is the fluorescence intensity corresponding to time t, I0 is the peak fluorescence intensity, and τ is the fluorescence lifetime of this section of erbium-doped fiber;

[0044] Perform photoelectric conversion on the collected fluorescence signal, and perform data processing on the obtained digital signal to obtain the value of the fluorescence lifetime. Taking the fast Fourier transform method as an example, the fluorescence signal f k (t) can be expressed as:

[0045] f k (t) = Aexp(-k*Δt / τ) + B

[0046] k = 0, 1, ···, N - 1

[0047] where Δt is the data sampling time interval, B is the background signal, A is a constant coefficient related to the fluorescent material, and N is the number of sampling points

[0048] Performing a direct Fourier transform on the above formula can obtain the 0th term F0 as:

[0049]

[0050] F0 is related to the background signal B.

[0051] The other terms can be simplified as:

[0052]

[0053] Except for the 0th term F0, the remaining terms are all independent of the background signal. The first non-zero term is used to calculate the fluorescence lifetime:

[0054]

[0055] This item is plural, and its argument value The tangent function Q1 of is:

[0056]

[0057] where Im refers to the imaginary part of the complex number F1, and Re refers to the real part of the complex number F1;

[0058] It can be seen that the phase tangent function Q1 of the first non-zero Fourier transform term F1 is a single-valued function of the fluorescence lifetime τ, independent of the initial light intensity A and the background noise B. Then the fluorescence lifetime can be expressed as:

[0059]

[0060] So far, the fluorescence lifetime τ1 of this shorter erbium-doped fiber is obtained;

[0061] Step 5: By calculating the fluorescence lifetime of the erbium-doped fiber in another optical path in the same data processing manner, the fluorescence lifetime τ2 of a longer erbium-doped fiber can be obtained;

[0062] Step 6: Take the difference between the fluorescence lifetimes of the above two erbium-doped fibers of different lengths to get τ0 = τ1 - τ2. Since both τ2 and τ1 change with the increase of temperature and the change trends are opposite, the obtained differential lifetime τ0 decreases with the increase of temperature and the sensitivity is higher than the above two fluorescence lifetimes.

[0063] To illustrate the feasibility of the method of the present invention, actual experimental data are used for illustration as follows:

[0064] Select a laser with a central wavelength of 980 nm and an adjustable light intensity of 0 - 80 mW. The modulation signal amplitude is selected as 2.5 V, and the modulation signal frequency is selected as 50 Hz. Erbium-doped fibers with lengths of 20 cm and 200 cm are respectively selected as the fluorescence-emitting materials, and the above method of the present invention is used for temperature detection. The relationship between the fluorescence lifetime of the 20-cm erbium-doped fiber and temperature is plotted as an image, as Figure 3 shown. It can be seen that when the temperature rises from 37 °C to 223 °C, the fluorescence lifetime of the 20-cm erbium-doped fiber decreases from 6.6421 ms to 6.5016 ms, and the lifetime-temperature change sensitivity is 0.00076 ms / °C; the relationship between the fluorescence lifetime of the 200-cm erbium-doped fiber and temperature is plotted as an image, as Figure 4 shown. It can be seen that when the temperature rises from 37 °C to 223 °C, the fluorescence lifetime of the 200-cm erbium-doped fiber increases from 1.87197 ms to 1.98221 ms, and the lifetime-temperature change sensitivity is 0.00059 ms / °C; the graph of the differential fluorescence lifetime changing with temperature is obtained by taking the difference between the fluorescence lifetimes of these two erbium-doped fibers asFigure 5 As shown, it can be seen that when the temperature rises from 37°C to 223°C, the differential fluorescence lifetime decreases from 4.77013 ms to 4.51939 ms, and the lifetime-temperature change sensitivity is 0.00135 ms / °C. The sensitivity has been greatly improved compared with the sensitivity of the fluorescence lifetimes of the above two sections of erbium-doped fiber varying with temperature. Finally, high-sensitivity detection of temperature can be achieved through the differential fluorescence lifetime. There is a linear relationship between the differential fluorescence lifetime and temperature, which can be obtained through simple fitting.

[0065] This embodiment relates to a high-sensitivity fiber fluorescence temperature detection device and detection method based on erbium-doped fiber, which is used for daily temperature detection in scenarios such as transformers, windings, and switch cabinets in the power industry to achieve the green and healthy development of industry. The device utilizes the characteristic that the proportion of non-radiative transitions in the light-emitting process of erbium-doped fibers with different lengths results in different response curves of their lifetimes to temperature, so as to achieve high-sensitivity detection of temperature.

[0066] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A high-sensitivity optical fiber fluorescence temperature detection device based on erbium-doped optical fiber, characterized in that: include: A light source output module, used for outputting pump light; A first erbium-doped optical fiber, used for generating a first fluorescence signal for temperature detection under the stimulation of pump light; a second erbium-doped optical fiber, used to generate a second fluorescence signal for temperature detection under the stimulation of the pump light; the first erbium-doped optical fiber and the second erbium-doped optical fiber have different lengths, the length of the first erbium-doped optical fiber satisfies that the fluorescence lifetime of the erbium-doped optical fiber decreases with increasing temperature, and the length of the second erbium-doped optical fiber satisfies that the fluorescence lifetime of the erbium-doped optical fiber increases with increasing temperature; A first wavelength division multiplexing module, used for separating a desired first optical signal from a first fluorescent signal; A second wavelength division multiplexing module, used for separating a desired second optical signal from the second fluorescent signal; A photoelectric detector, which converts the first optical signal separated by the first wavelength division multiplexing module into a first digital signal and outputs it, and converts the second optical signal separated by the second wavelength division multiplexing module into a second digital signal and outputs it; The signal processing module performs signal processing on the first digital signal output by the photodetector to obtain a first fluorescence lifetime, and performs signal processing on the second digital signal output by the photodetector to obtain a second fluorescence lifetime; and performs a difference between the first fluorescence lifetime and the second fluorescence lifetime, and obtains a temperature to be measured according to the difference.

2. The optical fiber fluorescence temperature detection device according to claim 1, characterized in that: The lengths of the first erbium-doped optical fiber and the second erbium-doped optical fiber are determined as follows: Determine the critical length L0 of the fluorescence lifetime related to the doping concentration of the erbium-doped fiber; The length of the first erbium-doped optical fiber is set to be shorter than the critical length L0; The length of the second erbium-doped optical fiber is set to be greater than L0.

3. The optical fiber fluorescence temperature detection device according to claim 1, characterized in that: The light source output module includes a signal generator and a laser. The signal generator generates a square wave pulse signal to the laser according to the set output frequency and amplitude. The laser generates a pump light pulse under the drive of the signal generator.

4. The optical fiber fluorescence temperature detection device according to claim 3, characterized in that: The light source output module also includes a fiber coupler, which is used to divide the pump light pulse generated by the laser into two output beams, one beam is output to the first wavelength division multiplexing module, and the other beam is output to the second wavelength division multiplexing module.

5. The optical fiber fluorescence temperature detection device according to any one of claims 1 to 4, characterized in that: The first wavelength division multiplexing module and the second wavelength division multiplexing module are both 980 / 1550 wavelength division multiplexers. The 980 / 1550 wavelength division multiplexers filter the pump light, and then the two optical signals reach the first erbium-doped optical fiber and the second erbium-doped optical fiber respectively.

6. The optical fiber fluorescence temperature detection device according to claim 1, characterized in that: In the signal processing module, the processing methods for processing the digital signal to obtain the fluorescence lifetime include fitting method, fast Fourier transform method and phase method.

7. A high-sensitivity optical fiber fluorescence temperature detection method based on erbium-doped optical fiber, characterized in that: include: Two erbium-doped optical fibers of different lengths are used as two detection units, wherein the length of one erbium-doped optical fiber satisfies that the fluorescence lifetime of the erbium-doped optical fiber decreases with increasing temperature, and the length of the other erbium-doped optical fiber satisfies that the fluorescence lifetime of the erbium-doped optical fiber increases with increasing temperature; and fluorescence detection signals emitted by the two detection units are obtained; The two fluorescence detection signals are processed separately to obtain two fluorescence lifetimes; The two fluorescence lifetimes obtained are subjected to differential processing to obtain a differential value; The temperature to be measured is obtained according to the differential value.

8. The high-sensitivity optical fiber fluorescence temperature detection method based on erbium-doped optical fiber according to claim 7 is characterized in that: The length determination method of two erbium-doped optical fibers of different lengths is: Determine the critical length L0 of the fluorescence lifetime related to the doping concentration of the erbium-doped fiber; Setting the length of the first erbium-doped optical fiber (4) to be shorter than the critical length L0; The length of the second erbium-doped optical fiber (6) is set to be greater than L0.

9. The high-sensitivity optical fiber fluorescence temperature detection method based on erbium-doped optical fiber according to claim 7, characterized in that: The steps of processing the two fluorescence detection signals respectively to obtain two fluorescence lifetimes include: Perform Fourier transform on the collected first fluorescence signal I1 to obtain the first-order term F 11 Wherein, Δt is the data sampling time interval, N is the number of sampling points, and τ1 is the fluorescence lifetime corresponding to the first fluorescence signal; According to the first fluorescence signal, the first-order term F is obtained 11 , and obtain the tangent function Q of the first fluorescence signal 11 : Among them, ImF 11 Represents the first-order term F 11 The imaginary part, ReF 11 Represents the first-order term F 11 The real part of According to the tangent function Q of the first fluorescence signal 11， Get the first fluorescence lifetime: Wherein, τ1 is the fluorescence lifetime of the first erbium-doped fiber; Perform Fourier transform on the collected second fluorescence signal to obtain the first-order term F 12 Wherein, τ2 is the fluorescence lifetime corresponding to the second fluorescence signal; The first-order term F is obtained according to the second fluorescence signal 12 , and obtain the tangent function Q of the second fluorescence signal 12 : Among them, ImF 12 Represents the first-order term F 12 The imaginary part, ReF 12 Represents the first-order term F 12 The real part of According to the tangent function Q of the second fluorescence signal 12 , and the second fluorescence lifetime is obtained: Wherein, τ2 is the fluorescence lifetime of the second erbium-doped fiber.

10. The high-sensitivity optical fiber fluorescence temperature detection method based on erbium-doped optical fiber according to claim 9, characterized in that: The difference between the two fluorescence lifetimes is: τ0=τ1-τ2 Here, τ0 is the difference in fluorescence lifetime.

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