Brillouin optical time domain reflection measuring device

Abstract

The utility model relates to the technical field of optical fiber sensing, and provides a Brillouin optical time domain reflection measuring device. The measuring device comprises a laser, a first coupler, a frequency shifter, a second coupler, a semiconductor optical amplifier, a circulator, a third coupler, a photoelectric detector, a first optical signal processing unit, a second optical signal processing unit and an acquisition processing module. Laser emitted by the laser device is subjected to frequency shift through the frequency shifter to obtain laser with various frequencies, the laser passes through the second coupler, is changed into pulsed light through the semiconductor optical amplifier, is amplified, passes through the first optical signal processing unit and the circulator, and then enters an optical fiber to be measured; according to the Brillouin optical time domain reflection measuring device, the pulse laser with multiple frequencies is used for carrying out sensing measurement on the optical fiber to be measured once to obtain multiple Brillouin frequency shift signals, and the obtained multiple Brillouin frequency shift signals are used for obtaining the physical state information of the optical fiber to be measured, so that the number of measurement times is reduced, and the measurement efficiency of the Brillouin optical time domain reflection measuring device is remarkably improved.

Description

Technical Field

[0001] The utility model relates to the technical field of optical fiber sensing, and more specifically to a Brillouin optical time domain reflection measurement device. Background Art

[0002] Brillouin Optical Time Domain Reflector (BOTDR) is a distributed fiber optic sensing technology based on the Brillouin scattering effect. It monitors physical information such as temperature and strain in optical fibers by measuring the characteristics of Brillouin scattered light.

[0003] There is a restrictive relationship between the measurement accuracy and measurement time of a Brillouin optical time-domain reflectometry device. Under the same conditions, to improve the measurement accuracy of a Brillouin optical time-domain reflectometry device, it is usually necessary to increase the measurement time to collect more backscattered signals for more accurate analysis of parameters such as the Brillouin frequency shift. While reducing the measurement cycle to shorten the measurement time can increase measurement efficiency, the measurement accuracy of the Brillouin optical time-domain reflectometry device will decrease due to insufficient signal collection and increased noise interference. Utility Model Content

[0004] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art and provide a Brillouin optical time domain reflectometry device, which improves the measurement efficiency of BOTDR without reducing the measurement accuracy of the Brillouin optical time domain reflectometry device.

[0005] The technical solution adopted by the utility model is a Brillouin optical time domain reflectometry device, which includes a laser, a first coupler, a frequency shifter, a second coupler, a semiconductor optical amplifier, a circulator, a third coupler, a photodetector, a first optical signal processing unit, a second optical signal processing unit and an acquisition and processing module;

[0006] The output end of the laser is connected to the input end of the first coupler, the first output end of the first coupler is optically connected to the first input end of the frequency shifter, the second output end of the first coupler is optically connected to the first input end of the second coupler, and the third output end of the first coupler is optically connected to the first input end of the third coupler; the output end of the frequency shifter is optically connected to the second input end of the second coupler, the output end of the second coupler is optically connected to the input end of the semiconductor optical amplifier, the output end of the semiconductor optical amplifier is optically connected to the first optical signal processing unit, the first optical signal processing unit is optically connected to the first transmission end of the circulator, the second transmission end of the circulator is used to optically connect to the optical fiber to be tested, the third transmission end of the circulator is optically connected to the second optical signal processing unit, and the second optical signal processing unit is optically connected to the second input end of the third coupler; the output end of the third coupler is optically connected to the photodetector, the photodetector is electrically connected to the acquisition and processing module, and the acquisition and processing module is electrically connected to the control end of the semiconductor optical amplifier; the acquisition and processing module is electrically connected to the second input end of the frequency shifter.

[0007] The laser light emitted by the laser of the utility model can be frequency-shifted by a frequency shifter to obtain laser light with a plurality of different frequencies. The laser light with a plurality of different frequencies enters the optical fiber to be measured after passing through a second coupler and a semiconductor optical amplifier. The Brillouin scattering effect can be used to obtain multiple Brillouin frequency-shifted signals at one time. The multiple Brillouin frequency-shifted signals obtained are used to obtain the physical state information of the optical fiber to be measured, thereby reducing the number of measurements and significantly improving the measurement efficiency of the Brillouin optical time-domain reflectometry measurement device.

[0008] Optionally, the first optical signal processing unit includes a first erbium-doped fiber amplifier and a first optical filter, the output end of the first erbium-doped fiber amplifier is optically connected to the input end of the first optical filter, the input end of the first erbium-doped fiber amplifier is optically connected to the output end of the semiconductor optical amplifier, and the first optical filter is optically connected to the first transmission end of the circulator.

[0009] Optionally, the second optical signal processing unit includes a second erbium-doped fiber amplifier and a second optical filter, the third transmission end of the circulator is optically connected to the input end of the second erbium-doped fiber amplifier, the output end of the second erbium-doped fiber amplifier is optically connected to the input end of the second optical filter, and the output end of the second optical filter is optically connected to the second input end of the third coupler.

[0010] Optionally, the acquisition and processing module includes an acquisition unit and a signal processing unit, the acquisition unit is electrically connected to the signal processing unit, the photodetector is electrically connected to the acquisition unit, the first output end of the signal processing unit is electrically connected to the control end of the semiconductor optical amplifier, and the second output end of the signal processing unit is electrically connected to the second input end of the frequency shifter.

[0011] Optionally, the measuring device further includes a frequency shifter driving unit, and the second output end of the signal processing unit is electrically connected to the second output end of the frequency shifter through the frequency shifter driving unit.

[0012] The output frequency of the frequency shifter is dynamically adjusted by the frequency shifter driving unit, so that each pulse light contains lasers of multiple frequencies, effectively enhancing the ability to resist coherent fading during the measurement process, thereby reducing the impact of coherent fading on the measurement results of the Brillouin optical time-domain reflectometry measurement device.

[0013] Optionally, the frequency shifter driving unit includes a DDS signal generating module and a power amplifier connected in series, the input end of the DDS signal generating module is electrically connected to the second output end of the signal processing unit, and the output end of the power amplifier is electrically connected to the second input end of the frequency shifter.

[0014] The DDS signal generation module generates a sweep frequency signal, which is amplified by a power amplifier to drive the frequency shifter to generate a laser with multiple frequency shift frequencies.

[0015] Optionally, the splitting ratio of the first coupler is 1:1:1.

[0016] Optionally, the laser is a narrow linewidth laser.

[0017] By using a narrow-linewidth laser as the light source, the Brillouin optical time-domain reflectometry device can output laser light with an extremely narrow spectral width, effectively reducing the dispersion effect of the laser during transmission, improving the coherence and stability of the signal, and thus enhancing the detection sensitivity and accuracy of the Brillouin frequency shift signal.

[0018] Optionally, the frequency shifter is an electro-optical frequency shifter.

[0019] The frequency shifter adopts an electro-optical frequency shifter, which can use the electro-optic effect to achieve fast and accurate modulation of the laser frequency.

[0020] Optionally, the frequency shifter is an acousto-optic frequency shifter.

[0021] The acousto-optic frequency shifter can utilize the principle of acousto-optic interaction to achieve stable and precise shifting of the laser frequency, thereby maintaining good coherence of the laser and improving the accuracy of subsequent Brillouin frequency shift signal detection.

[0022] Optionally, the measuring device further includes an optical isolator, which is arranged between the laser and the first coupler.

[0023] An optical isolator is provided between the laser and the first coupler, which can effectively prevent reflected light from interfering with and damaging the laser, thereby improving the stability and safety of laser output.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The laser light emitted by the laser is frequency-shifted by a frequency shifter to obtain laser light with multiple frequencies. The laser light with multiple frequencies passes through a second coupler, is converted into pulsed light by a semiconductor optical amplifier, and is amplified. The pulsed light then passes through a first optical signal processing unit and a circulator before entering the optical fiber to be tested. A single sensing measurement using the pulsed laser light with multiple frequencies can obtain multiple Brillouin frequency shift signals. The obtained multiple Brillouin frequency shift signals are used to obtain physical state information of the optical fiber to be tested, thereby reducing the number of measurements and significantly improving the measurement efficiency of the Brillouin optical time-domain reflectometry device.

[0026] 2. The DDS signal generation module generates a frequency sweep signal, so that each pulse light contains lasers of multiple frequencies, which significantly enhances the system's ability to resist coherent fading and effectively avoids the coherent fading phenomenon, thereby improving measurement efficiency while ensuring measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure is a schematic diagram of the overall structure of a Brillouin optical time domain reflectometry device of the present invention.

[0028] Figure 2 This is another structural schematic diagram of a Brillouin optical time-domain reflectometry device of the present invention. DETAILED DESCRIPTION

[0029] The drawings in this utility model are for illustrative purposes only and are not to be construed as limiting the scope of this utility model. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced in size, and do not represent the actual dimensions of the products. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted from the drawings.

[0030] Example 1

[0031] like Figure 1As shown, this embodiment provides a Brillouin optical time domain reflectometry device, which includes a laser 1, a first coupler 2, a frequency shifter 3, a second coupler 4, a semiconductor optical amplifier SOA5, a first optical signal processing unit 6, a circulator 7, a third coupler 16, a photodetector PD15, a second optical signal processing unit 9 and an acquisition and processing module 10.

[0032] In which, the output end of the laser 1 is optically connected to the input end of the first coupler 2, the first output end of the first coupler 2 is optically connected to the first input end of the frequency shifter 3, the second output end of the first coupler 2 is optically connected to the first input end of the second coupler 4, and the third output end of the first coupler 2 is optically connected to the first input end of the third coupler 16.

[0033] The output end of the frequency shifter 3 is optically connected to the second input end of the second coupler 4, the output end of the second coupler 4 is optically connected to the first input end of the semiconductor optical amplifier SOA5, the output end of the semiconductor optical amplifier SOA5 is optically connected to the first optical signal processing unit 6, the first optical signal processing unit 6 is optically connected to the first transmission end of the circulator 7, the second transmission end of the circulator 7 is used to be optically connected to the optical fiber 8 to be tested, the third transmission end of the circulator 7 is optically connected to the second optical signal processing unit 9, and the second optical signal processing unit 9 is optically connected to the second input end of the third coupler 16.

[0034] The output end of the third coupler 16 is optically connected to the photodetector PD15, the photodetector PD15 is electrically connected to the acquisition and processing module 10, and the acquisition and processing module 10 is electrically connected to the control end of the semiconductor optical amplifier SOA5; the acquisition and processing module 10 is electrically connected to the second input end of the frequency shifter 3.

[0035] like Figure 2 As shown, in this embodiment, the first optical signal processing unit 6 includes a first erbium-doped fiber amplifier EDFA601 and a first optical filter 602. The output end of the first erbium-doped fiber amplifier EDFA601 is optically connected to the input end of the first optical filter 602. The first erbium-doped fiber amplifier EDFA601 is optically connected to the output end of the semiconductor optical amplifier SOA5. The first optical filter 602 is optically connected to the first transmission end of the circulator 7.

[0036] The acquisition and processing module 10 includes an acquisition unit 101 and a signal processing unit 102. The acquisition unit 101 is electrically connected to the signal processing unit 102, the photodetector PD15 is electrically connected to the acquisition unit 101, the first output end of the signal processing unit 102 is electrically connected to the control end of the semiconductor optical amplifier SOA5, and the second output end of the signal processing unit 102 is connected to the second input end of the frequency shifter 3.

[0037] Furthermore, the measuring device further comprises a frequency shifter driving unit 11 , an input end of the frequency shifter driving unit 11 is electrically connected to the second output end of the signal processing unit 102 , and an output end of the frequency shifter driving unit 11 is electrically connected to the frequency shifter 3 .

[0038] It can be understood that the frequency shifter driving unit 11 is used to drive the optical signal passing through the frequency shifter 3 to perform frequency shift.

[0039] The output frequency of the frequency shifter 3 is dynamically adjusted by the frequency shifter driving unit 11, so that each pulse light contains lasers of multiple frequencies, which effectively enhances the anti-coherent fading capability during the measurement process, thereby reducing the impact of coherent fading on the measurement results of the Brillouin optical time domain reflectometry device.

[0040] Furthermore, the frequency shifter driving unit 11 includes a DDS signal generating module 112 and a power amplifier 111 connected in series, the input end of the DDS signal generating module 112 is electrically connected to the second output end of the signal processing unit 102, and the output end of the power amplifier 111 is electrically connected to the second input end of the frequency shifter 3.

[0041] It can be understood that the DDS signal generating module 112 is implemented by a signal generator using direct digital frequency synthesis (DDS) technology. Direct digital frequency synthesis technology DDS can improve the frequency stability and accuracy generated by the signal generator to the same level as the reference frequency, and can also finely adjust the frequency generated by the signal generator.

[0042] In this embodiment, the sweep signal generated by the DDS signal generating module 112 can be a linear sweep signal, or a logarithmic sweep signal, or other sweep signals. The sweep signal is generated by the DDS signal generating module 112, and the sweep signal is amplified by the power amplifier 12, thereby driving the frequency shifter 3 to generate a laser signal with multiple shift frequencies.

[0043] In this embodiment, the laser 1 can be a narrow-linewidth laser. Using a narrow-linewidth laser as a light source allows the Brillouin optical time-domain reflectometry device to output laser light with an extremely narrow spectral width, effectively reducing the dispersion effect of the laser during transmission, improving the coherence and stability of the signal, and thus enhancing the detection sensitivity and accuracy of the Brillouin frequency shift signal.

[0044] In this embodiment, the frequency shifter 3 can be an electro-optical frequency shifter or an acousto-optic frequency shifter. Electro-optic frequency shifters can utilize the electro-optic effect to achieve rapid and precise modulation of the laser frequency. Acousto-optic frequency shifters can utilize the principle of acousto-optic interaction to achieve stable and precise shifting of the laser frequency, thereby maintaining good laser coherence and improving the accuracy of subsequent Brillouin frequency shift signal detection. In specific implementations, the appropriate frequency shifter can be selected based on actual needs.

[0045] like Figure 2 As shown, in this embodiment, the second optical signal processing unit 9 includes a second erbium-doped fiber amplifier (EDFA) 901 and a second optical filter 902. Specifically, the third transmission end of the circulator 7 is optically connected to the input end of the second erbium-doped fiber amplifier (EDFA) 901, the output end of the second erbium-doped fiber amplifier (EDFA) 901 is optically connected to the input end of the second optical filter 902, and the output end of the second optical filter 902 is optically connected to the second input end of the third coupler 16. The second erbium-doped fiber amplifier (EDFA) 901 is used to amplify the Brillouin scattered signal transmitted by the circulator 7, and the second optical filter 902 is used to filter the pulsed light output by the second erbium-doped fiber amplifier (EDFA) 901.

[0046] In an optional embodiment, the splitting ratio of the first coupler 2 can be 1:1:1, that is, one-third of the light intensity of the continuous laser emitted by the laser 1 enters the second coupler 4, the frequency shifter 3 and the third coupler 16 respectively, thereby meeting the measurement requirements.

[0047] In order to prevent the reflected light from interfering with and damaging the laser 1 , in this embodiment, the measuring device may further include an optical isolator (not shown in the figure), wherein the optical isolator is disposed between the laser 1 and the first coupler 2 .

[0048] The Brillouin optical time-domain reflectometry device of the present invention operates as follows: During operation, the optical signal emitted by laser 1 is distributed by first coupler 2. The first path enters third coupler 16 as reference light, while the second path undergoes frequency shifting by frequency shifter 3 and is combined with the third path in second coupler 4. The signal is then amplified by semiconductor optical amplifier (SOA) 5. After amplification and filtering, the signal passes through first erbium-doped fiber amplifier (EDFA) 601 and first optical filter (602) in first optical signal processing unit 6 before entering circulator 7, where it is injected into optical fiber 8 under test. Brillouin scattered light in optical fiber 8 under test returns to circulator 7, passes through second erbium-doped fiber amplifier (EDFA) 901 and second optical filter (902) in second optical signal processing unit, and enters third coupler 16. Third coupler 16 directs the scattered light signal to photodetector PD15, which converts the optical signal into an electrical signal. This signal is collected by acquisition unit 101 of acquisition and processing unit 10 and sent to signal processing unit 102 for processing, thereby generating measurement data.

[0049] In the above workflow, the laser light with multiple sweep frequencies is amplified and modulated by the semiconductor optical amplifier SOA5 to become a pulse light. This pulse light has multiple sweep frequencies, so after entering the optical fiber 8 to be tested, it can effectively eliminate coherent fading and will not cause the scattered light signal-to-noise ratio to be extremely low, resulting in inaccurate measurement.

[0050] The Brillouin optical time-domain reflectometry device of this embodiment operates as follows: a series of frequency-sweep signals f1 to fn are generated by a DDS signal generator module 112. These signals pass through a power amplifier 111 and undergo frequency shifting by a frequency shifter 3, generating lasers with multiple shifted frequencies. These laser signals interact with the Brillouin frequency shift fv and are demodulated in a sweeping sequence to obtain 2n+1 frequency components including fv: fv-f1, fv, fv+f1; fv-f2, fv, fv+f2; ...; fv-fn, fv, fv+fn. Compared to conventional measurement methods that can only obtain one frequency fv at a time, the Brillouin optical time-domain reflectometry device of the present invention can obtain 2n+1 frequencies at a time, thereby increasing measurement efficiency by 2n+1 times.

[0051] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A Brillouin optical time-domain reflectometry device, characterized in that: The measuring device includes a laser, a first coupler, a frequency shifter, a second coupler, a semiconductor optical amplifier, a circulator, a third coupler, a photodetector, a first optical signal processing unit, a second optical signal processing unit and an acquisition processing module; The output end of the laser is optically connected to the input end of the first coupler, the first output end of the first coupler is optically connected to the first input end of the frequency shifter, the second output end of the first coupler is optically connected to the first input end of the second coupler, and the third output end of the first coupler is optically connected to the first input end of the third coupler; the output end of the frequency shifter is optically connected to the second input end of the second coupler, the output end of the second coupler is optically connected to the input end of the semiconductor optical amplifier, the output end of the semiconductor optical amplifier is optically connected to the first optical signal processing unit, the first optical signal processing unit is optically connected to the first transmission end of the circulator, the second transmission end of the circulator is used to be optically connected to the optical fiber to be tested, the third transmission end of the circulator is optically connected to the second optical signal processing unit, and the second optical signal processing unit is optically connected to the second input end of the third coupler; the output end of the third coupler is optically connected to the photodetector, the photodetector is electrically connected to the acquisition and processing module, and the acquisition and processing module is electrically connected to the control end of the semiconductor optical amplifier; The acquisition and processing module is electrically connected to the second input end of the frequency shifter.

2. The Brillouin optical time-domain reflectometry device according to claim 1, characterized in that: The first optical signal processing unit includes a first erbium-doped fiber amplifier and a first optical filter. The output end of the first erbium-doped fiber amplifier is optically connected to the input end of the first optical filter. The input end of the first erbium-doped fiber amplifier is optically connected to the output end of the semiconductor optical amplifier. The first optical filter is optically connected to the first transmission end of the circulator.

3. The Brillouin optical time-domain reflectometry device according to claim 1, characterized in that: The second optical signal processing unit includes a second erbium-doped fiber amplifier and a second optical filter. The third transmission end of the circulator is optically connected to the input end of the second erbium-doped fiber amplifier, the output end of the second erbium-doped fiber amplifier is optically connected to the input end of the second optical filter, and the output end of the second optical filter is optically connected to the second input end of the third coupler.

4. The Brillouin optical time-domain reflectometry device according to claim 2, wherein: The acquisition and processing module includes an acquisition unit and a signal processing unit, the acquisition unit is electrically connected to the signal processing unit, the photodetector is electrically connected to the acquisition unit, the first output end of the signal processing unit is electrically connected to the control end of the semiconductor optical amplifier, and the second output end of the signal processing unit is electrically connected to the second input end of the frequency shifter.

5. The Brillouin optical time-domain reflectometry device according to claim 4, characterized in that: The measuring device further includes a frequency shifter driving unit, and the second output end of the signal processing unit is electrically connected to the second input end of the frequency shifter through the frequency shifter driving unit.

6. The Brillouin optical time-domain reflectometry device according to claim 5, characterized in that: The frequency shifter driving unit includes a DDS signal generating module and a power amplifier connected in series, the input end of the DDS signal generating module is electrically connected to the second output end of the signal processing unit, and the output end of the power amplifier is electrically connected to the second input end of the frequency shifter.

7. The Brillouin optical time-domain reflectometry device according to any one of claims 1 to 6, characterized in that: The splitting ratio of the first coupler is 1:1:

1.

8. The Brillouin optical time-domain reflectometry device according to any one of claims 1 to 6, characterized in that: The laser is a narrow linewidth laser.

9. The Brillouin optical time-domain reflectometry device according to any one of claims 1 to 6, characterized in that: The frequency shifter is an electro-optical frequency shifter.

10. The Brillouin optical time domain reflectometry device according to any one of claims 1 to 6, characterized in that: The frequency shifter is an acousto-optic frequency shifter.

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