Dynamic BOTDA sensing method and system based on injection-locked high-order sideband output

Abstract

The embodiment of the present invention provides a dynamic BOTDA sensing method and system based on injection-locked high-order sideband output. The method includes: the laser output by the light source is divided into a first sub-beam and a second sub-beam; a channel of the arbitrary waveform generator generates a pulse signal, which is loaded into the first sub-beam through a first electro-optical modulator, and modulated from continuous light to pulse pump light to enter the optical fiber to be tested; another channel of the arbitrary waveform generator generates an arbitrary wave signal, and the second sub-beam is modulated by a second electro-optical modulator to generate multi-order sidebands, each order sideband enters the slave laser to lock the preset sideband, obtains the detection light that locks the preset sideband and enters the optical fiber to be tested to generate stimulated Brillouin scattering with the pulse pump light to receive the generated scattered light; each scanning frequency of the arbitrary wave signal corresponds to each pulse of the pulse signal. The above-mentioned technology of the present invention can reduce the arbitrary wave bandwidth requirement by one order of magnitude in dynamic measurement because the high-order sidebands are injection-locked.

Description

Technical Field

[0001] The present invention relates to the field of distributed optical fiber sensing, and more specifically, embodiments of the present invention relate to a dynamic BOTDA sensing method and system based on injection-locked high-order sideband output. Background Art

[0002] In recent years, cities in my country are in the peak period of infrastructure construction. For example, the durability and firmness of key projects such as plateau railways and cross-sea bridges have always been the focus of engineering attention. Long-term and effective monitoring of railways and bridges is necessary. Real-time and effective sensing systems play an extremely important role. They can monitor the stress and temperature changes of bridges, roads and buildings in real time and issue early warning information in time. In addition, in the construction of intelligent cities, the widespread laying of sensing tools can also play a role in intelligent perception of changes in target city roads and surrounding environments.

[0003] Therefore, it is particularly important to study a real-time, effective and low-cost sensing technology to improve the effectiveness and real-time nature of infrastructure monitoring and accelerate the construction of smart cities. In the sensing system, optical fiber sensing technology has unique advantages. Compared with traditional electronic sensing devices, it uses optical fiber as a sensing tool, which is small in size, light, and convenient for the laying of sensing devices. It also has strong resistance to electromagnetic interference and corrosion. In recent years, optical fiber sensing methods have been used in almost all modern engineering projects.

[0004] Among them, scattering-type distributed optical fiber sensing technology has developed rapidly in recent decades. Based on the Rayleigh, Brillouin and Raman scattering effects in optical fibers, it measures the disturbance of the external environment of optical fibers. This measurement method can realize the temperature and stress changes at different positions along the length of the optical fiber, and can truly realize distributed optical fiber sensing. This new sensing technology has been applied to the safety monitoring of major projects such as oil and gas pipelines, railway tunnels, and power cables. With the improvement of optical fiber sensing technology and the reduction of system costs, it will be more widely used in other fields such as national defense and communications.

[0005] Distributed Brillouin fiber optic sensing technology, based on the principle of Brillouin scattering, senses changes in temperature and stress in the external environment by measuring the Brillouin frequency shift and line width of backscattered light. It has high spatial resolution and measurement accuracy and can achieve long-distance fiber optic sensing. Among them, BOTDA technology is a typical distributed fiber optic sensing technology. It uses the stimulated Brillouin scattering effect to measure the gain intensity of the swept frequency detection light to obtain the frequency shift and line width of the scattered light, and finally obtain the Brillouin spectrum information.

[0006] The traditional BOTDA system takes about tens of seconds to several minutes to measure once, which is suitable for static temperature and strain measurement, but not for instantaneous fast measurement. In 2012, researchers proposed a technology for fast BOTDA, which brought the classic BOTDA method into the field of dynamic sensing. By using an arbitrary waveform generator that can quickly switch between frequencies, IQ upsampling technology is used to achieve fast frequency sweeping of the detection light, that is, optical frequency agility technology, which is only limited by the length of the optical fiber and the number of frequencies (Peled Yair, Motil Avi, and Tur Moshe, "Fast Brillouin optical time domain analysis for dynamic sensing," Optics. Express, 20, 8584-8591, 2012.). At present, it is possible to achieve fast measurement of the Brillouin system, and all Brillouin spectrum information can be obtained within a few hundred microseconds. It is widely used in fast dynamic measurement and can measure dynamic vibrations of several kilohertz. However, since the Brillouin frequency shift in the optical fiber is about 11 GHz, this usually requires high-bandwidth microwave generators and other microwave devices, which will introduce huge costs. For an emerging technology, reducing system costs is particularly important for the development and promotion of this technology. Summary of the invention

[0007] Therefore, an improved BOTDA technology is highly desired to reduce the system cost.

[0008] In this context, embodiments of the present invention are intended to provide a dynamic BOTDA sensing method and system based on injection-locked high-order sideband output.

[0009] In a first aspect of an embodiment of the present invention, a dynamic BOTDA sensing method based on injection-locked high-order sideband output is provided, the dynamic BOTDA sensing method comprising: dividing the laser output by a light source into a first sub-beam entering a first electro-optical modulator and a second sub-beam entering a second electro-optical modulator; causing a channel of an arbitrary waveform generator to generate a pulse signal, loading the first sub-beam through the first electro-optical modulator, modulating the first sub-beam from continuous light to pulse light, and entering the optical fiber to be tested as a pulse pump light; causing another channel of the arbitrary waveform generator to generate an arbitrary wave signal, modulating the second sub-beam through the second electro-optical modulator to generate multi-order sidebands, and causing the modulated light beam to enter a slave laser to lock a preset sideband in the multi-order sidebands, obtaining a detection light that locks the preset sideband and entering the optical fiber to be tested to undergo stimulated Brillouin scattering with the pulse pump light to receive the generated scattered light; each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal.

[0010] Furthermore, the operating bandwidth of the arbitrary waveform generator is any one of 1.2 GHz, 1.54 GHz, 2.16 GHz and 3.6 GHz.

[0011] Further, the preset sideband locked by the slave laser is a high-order sideband among the multi-order sidebands, and the high-order sideband is one or more of -9th order, -7th order, -5th order and -3rd order.

[0012] Furthermore, the preset sideband locked by the slave laser is a -1 order sideband among the multiple order sidebands.

[0013] In a second aspect of the embodiments of the present invention, a dynamic BOTDA system based on injection locked high-order sideband output is provided, the dynamic BOTDA system comprising a master laser, a slave laser, a beam splitting module, a first electro-optical modulator, a second electro-optical modulator, an arbitrary waveform generator and a receiving module; the light beam output by the master laser is divided into a first sub-beam and a second sub-beam by the beam splitting module, The first sub-beam enters the first electro-optical modulator, and one channel of the arbitrary waveform generator is used to generate a pulse signal to be loaded into the first sub-beam through the first electro-optical modulator, and the first sub-beam is modulated from continuous light to pulse light, and enters the optical fiber to be tested as a pulse pump light; the second sub-beam enters the second electro-optical modulator, and another channel of the arbitrary waveform generator is used to generate an arbitrary wave signal to modulate the second sub-beam through the second electro-optical modulator, and the modulated light beam enters the slave laser to lock the preset sideband in the multi-order sidebands, and obtains the detection light output by the slave laser, and the detection light enters the optical fiber to be tested and undergoes stimulated Brillouin scattering with the pulse pump light, and the generated scattered light is received by the receiving module; wherein each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal.

[0014] Further, the beam splitting module is a coupler; the dynamic BOTDA system also includes a first microwave amplifier, a second microwave amplifier, an erbium-doped fiber amplifier, a first circulator, a second circulator, an optical isolator, a photodetector and an oscilloscope; wherein, after the first sub-beam is output from the coupler, it enters the first electro-optic modulator, the pulse signal generated by the arbitrary waveform generator is amplified by the first microwave amplifier and then loaded into the first sub-beam through the first electro-optic modulator, the pulse light output from the first electro-optic modulator is amplified by the erbium-doped fiber amplifier and enters the optical fiber to be tested through the first circulator; after the second sub-beam is output from the coupler, it enters the second electro-optic modulator, the arbitrary wave signal generated by the arbitrary waveform generator is amplified by the second microwave amplifier and then modulated by the second electro-optic modulator, and the modulated light beam enters the slave laser after passing through the second circulator, the detection light output from the laser passes through the second circulator and then passes through the optical isolator to enter the optical fiber to be tested and undergoes stimulated Brillouin scattering with the pulse pump light, and the generated scattered light passes through the first circulator and the photodetector and is received by the oscilloscope.

[0015] Furthermore, the operating bandwidth of the arbitrary waveform generator is one of 1.2 GHz, 1.54 GHz, 2.16 GHz, and 3.6 GHz.

[0016] Further, the preset sideband locked by the slave laser is a high-order sideband among the multi-order sidebands, and the high-order sideband is one or more of -9th order, -7th order, -5th order and -3rd order.

[0017] Furthermore, the preset sideband locked by the slave laser is a -1 order sideband among the multiple order sidebands.

[0018] According to the dynamic BOTDA sensing method and system based on injection-locked high-order sideband output according to the embodiment of the present invention, an ultrafast measurement scheme for distributed optical fiber strain or temperature is provided, which uses injection locking technology, uses low-frequency microwave signals for modulation, locks high-order sidebands or first-order sidebands to output amplified high-order sidebands for frequency sweeping to generate Brillouin signals, so that the microwave bandwidth requirements can be reduced. The present invention can reduce the microwave bandwidth requirements by one order of magnitude in dynamic measurement, from 10.8GHz to about 1.2GHz, and has higher stability and higher spatial resolution.

[0019] The dynamic BOTDA sensing method and system based on injection-locked high-order sideband output of the present invention have the following advantages:

[0020] 1. It can realize ultrafast measurement of distributed strain and temperature. Only low-bandwidth microwave devices are needed to realize dynamic BOTDA measurement, and its sampling frequency is only related to the length of the optical fiber to be measured and the average number of signals.

[0021] 2. The detection light utilizes the characteristics of injection locking and uses low-frequency microwaves for modulation to lock the first-order or high-order sidebands generated by the laser modulation, and outputs the amplified high-order sidebands, which can reduce the microwave modulation bandwidth by an order of magnitude.

[0022] 3. This patent can reduce the bandwidth requirements based on dynamic BOTDA, but can achieve other performance of traditional dynamic BOTDA. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0024] Figure 1 is a schematic diagram showing an example structure of a dynamic BOTDA system based on injection-locked high-order sideband output according to an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram showing another exemplary structure of a dynamic BOTDA system based on injection-locked high-order sideband output according to an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram showing a stimulated Brillouin scattering process of optical frequency-agile detection light and pump light in an optical fiber to be tested;

[0027] Figure 4 is a schematic diagram showing injection locked high-order sidebands.

[0028] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts. DETAILED DESCRIPTION

[0029] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided only to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0030] It should be understood herein that any number of elements in the drawings is for illustration rather than limitation, and any naming is only for distinction rather than having any limiting meaning.

[0031] The principle and spirit of the present invention are explained in detail below with reference to several representative embodiments of the present invention.

[0032] Exemplary Devices

[0033] An embodiment of the present invention provides a dynamic BOTDA system based on injection-locked high-order sideband output, the dynamic BOTDA system comprising a master laser, a slave laser, a beam splitting module, a first electro-optical modulator, a second electro-optical modulator, an arbitrary waveform generator and a receiving module; the light beam output by the master laser is divided into a first sub-beam and a second sub-beam by the beam splitting module, the first sub-beam enters the first electro-optical modulator, a channel of the arbitrary waveform generator is used to generate a pulse signal to be loaded into the first sub-beam through the first electro-optical modulator, the first sub-beam is modulated from continuous light to pulse light, and enters the optical fiber to be tested as a pulse pump light; the second sub-beam enters the second electro-optical modulator, another channel of the arbitrary waveform generator is used to generate an arbitrary wave signal to modulate the second sub-beam through the second electro-optical modulator, and the modulated light beam enters the slave laser to lock the preset sideband, and the detection light output by the slave laser is obtained, the detection light enters the optical fiber to be tested and undergoes stimulated Brillouin scattering with the pulse pump light, and the generated scattered light is received by the receiving module; wherein each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal.

[0034] Figure 1 An example of a dynamic BOTDA system based on injection-locked high-order sideband output according to an embodiment of the present disclosure is schematically shown.

[0035] like Figure 1 As shown, the dynamic BOTDA system includes a main laser 101 (i.e. Figure 1 Laser in), from laser 102 (ie Figure 1 SL in the beam splitter module 103, the first electro-optic modulator 107 (i.e. Figure 1 EOM1 in the embodiment of the present invention), the second electro-optic modulator 108 (i.e. Figure 1 EOM2 in), arbitrary waveform generator 109 (i.e. Figure 1 AWG in the receiver module.

[0036] The main laser 101 is used as a light source, and the laser frequency output is ν0. The laser output by the laser is divided into two beams by the beam splitting module 103, namely the first sub-beam and the second sub-beam. The first sub-beam is used in the first branch (such as Figure 1 The pulsed pump light is generated in the upper branch (shown in FIG. 1 ), and the second sub-beam is used to generate a pulsed pump light in the second branch (shown in FIG. Figure 1 A frequency-agile detection light, i.e., a detection light capable of rapidly changing frequency, is generated in the lower branch (as shown in FIG. 1 ).

[0037] The beam splitting module 103 is, for example, a coupler (eg Figure 2OC shown), the splitting ratio of the coupler can be, for example, 50:50, or can be other values, such as 40:60, or 20:80, etc.

[0038] The first sub-beam enters the first electro-optic modulator 107, and a channel (such as Figure 1 The CH1 shown in FIG. 1 is used to generate a pulse signal. Thus, the pulse signal is loaded into the first sub-beam through the first electro-optical modulator 107, and the first sub-beam is modulated from continuous light to pulse light, and enters the optical fiber to be tested 115 (such as FIG. 115 ) as a pulse pump light. Figure 1 FUT shown).

[0039] In one embodiment of the present invention, Figure 2 As shown, the dynamic BOTDA system may include an erbium-doped fiber amplifier 111 (i.e. Figure 2 EDFA in the first circulator 112 (i.e. Figure 2 CIR1 in), photodetector 116 (i.e. Figure 2 PD in) and oscilloscope 117 (i.e. Figure 2 DAQ in Figure 1 As shown, after the first sub-beam is output from the coupler 103, it enters the first electro-optic modulator 107. The pulse signal generated by the arbitrary waveform generator 109 is amplified by the first microwave amplifier (not shown in the figure) and then loaded into the first sub-beam through the first electro-optic modulator 107. The pulse light output from the first electro-optic modulator 107 is amplified by the erbium-doped fiber amplifier 111 and enters one side of the optical fiber 115 to be tested (as shown in the figure) through the first circulator 112 (entering from port 1 and exiting from port 2 of the first circulator 112). Figure 2 As shown, the light to be measured 115 enters from the upper branch).

[0040] See also Figure 1 The second sub-beam enters the second electro-optic modulator 108, and another channel (such as Figure 1 The CH2 shown in FIG. 1 is used to generate an arbitrary wave signal to modulate the second sub-beam through the second electro-optical modulator 108 to generate multi-order sidebands. Each scanning frequency of the arbitrary wave signal corresponds to each pulse of the pulse signal one by one. The modulated second sub-beam enters the slave laser 102 to lock the preset sideband in the second sub-beam through the slave laser 102, that is, the preset sideband in the multi-order sidebands mentioned above.

[0041] The preset sideband locked by the slave laser 102 may be a -1 order sideband among the above-mentioned multi-order sidebands, or a high-order sideband, such as -9 order, -7 order, -5 order, or -3 order.

[0042] It should be noted that the 1st order or higher order mentioned in the embodiments of the present invention all refer to the negative order, that is, negative 1st order, or negative higher order (such as -9th order, -7th order, -5th order, -3rd order). For convenience, the 1st order or higher order (such as 9th order, etc.) sometimes mentioned below also refers to the negative order sideband.

[0043] The slave laser 102 is an injection-locked laser. By adjusting the starting frequency interval of the slave laser 102 so that the desired sidebands (such as the first-order sideband and / or higher-order sidebands) of the modulated second sub-beam can fall into the starting frequency interval, the desired sidebands are locked and amplified.

[0044] like Figure 1 As shown, the detection light output from the laser 102 enters the optical fiber to be tested 115 and generates stimulated Brillouin scattering with the pulse pump light, and the generated scattered light is received by the receiving module.

[0045] In one embodiment of the present invention, Figure 2 As shown, the dynamic BOTDA system may include a second microwave amplifier (not shown in the figure), a second circulator 113 (CIR2), and an optical isolator 114 (ISO). After the second sub-beam is output from the coupler 103, it enters the second electro-optical modulator 108. The arbitrary wave signal generated by the arbitrary waveform generator 109 is amplified by the second microwave amplifier and then modulated by the second electro-optical modulator 108. The modulated light beam passes through the second circulator 113 and enters the laser 102. The detection light output from the laser 102 passes through the second circulator 113 and then passes through the optical isolator 114 and enters the optical fiber to be tested 115 to generate stimulated Brillouin scattering with the pulse pump light. The generated scattered light passes through the first circulator 112 (enters from port 2 and exits from port 3 of the first circulator) and is received by the oscilloscope 117 through the photodetector 116.

[0046] in, Figure 2 The “Pump pulse” shown in FIG. 1 represents a pump pulse, that is, the pulsed pump light mentioned above; and the “Probe wave” represents a probe light.

[0047] In an embodiment of the present invention, the operating bandwidth of the arbitrary wave generator may be one of 1.2 GHz, 1.54 GHz, 2.16 GHz, and 3.6 GHz.

[0048] In the embodiment of the present invention, when sensing slow signals, a microwave source can be used instead of an AWG. The microwave source drives the electro-optic modulator to generate various sidebands to shift the carrier frequency, and the electro-optic modulator is driven by a pulse generator to generate pulsed light. The high-order sidebands are locked by injection from the laser, which can also reduce the microwave bandwidth requirements.

[0049] In one example, the working bandwidth of the arbitrary wave generator is 1.2 GHz, the preset sideband locked from the laser 102 is the 9th order, and the bandwidth of the 9th order is 1.2 GHz×9=10.8 GHz. In this example, the bandwidth of the detection light after the laser 102 locks the 9th order sideband output is 10.8 GHz. When the detection light output after injection locking in this example is input into the optical fiber to be tested and Brillouin scattering occurs with the pulse pump light, the Brillouin gain can be measured, and the device bandwidth requirement is only 1.2 GHz, which greatly reduces the cost of the device. In the prior art, the cost of microwave generators (arbitrary waveform generators) and other microwave devices for realizing 10.8 GHz bandwidth measurement is very huge, while this embodiment only requires microwave generators (arbitrary waveform generators) and other microwave devices that meet the 1.2 GHz bandwidth requirement, which greatly reduces the system cost.

[0050] In addition, in another example, the working bandwidth of the arbitrary wave generator is 1.2 GHz, the preset sideband locked by the laser 102 is the 1st order, the bandwidth of the 1st order is 1.2 GHz, and the bandwidth of the 9th order is 1.2 GHz×9=10.8 GHz. In this example, the bandwidth of the detection light after the laser 102 locks the 1st order sideband output (corresponding to the 1st order sideband) is 1.2 GHz, but part of the 9th order sideband is still amplified (some other high-order sidebands are also amplified, such as the 3rd to 7th order). When the probe light output after injection locking in this example is input into the optical fiber to be tested and generates Brillouin scattering with the pulse pump light, the 1.2GHz 1st-order sideband cannot measure the Brillouin gain, and the bandwidth of the 3rd-7th-order sidebands does not meet the Brillouin gain. At the same time, because it is far away from the 9th-order sideband (for example, the 7th-order is 2.4GHz away from the 9th-order, the 5th-order is 4.8GHz away from the 9th-order, and the 3rd-order is 6GHz away from the 9th-order), it will not affect the Brillouin gain spectrum (that is, Brillouin gain will not occur near the 3rd-7th-order sidebands). In the experiment, the feasibility of this solution was confirmed, and very good measurement results were obtained.

[0051] In the above two examples, no matter whether the 1st-order or 9th-order sideband is locked, the 9th-order sideband is actually used for Brillouin gain measurement. Only a microwave generator (arbitrary waveform generator) with a bandwidth of 1.2 GHz and other microwave devices are needed to achieve the measurement of 10.8 GHz Brillouin gain. Therefore, the measurement bandwidth can be reduced from 10.8 GHz to 1 / 9, that is, to 1.2 GHz, which is close to 1 order of magnitude.

[0052] In the embodiment of the present invention, in addition to the 9th order sideband, the 3rd to 7th order sideband or higher order sideband may also be used. However, compared with the 3rd to 7th order sideband or the 11th order or above (including the 11th order), the 9th order sideband has the best effect of measurement, because: for the 3rd to 7th order sideband, the required bandwidth requirements are 10.8GHz÷3=3.6GHz, 10.8GHz÷5=2.16GHz, 10.8GHz÷7=1.54GHz, respectively, and the bandwidth is also reduced, but not as much as the 1.2GHz of the 9th order, so the cost of the 9th order is higher; and for the 11th order or above sideband, taking the 11th order as an example, 10.8GHz÷11=0.98GHz, that is, if the 11th order sideband is used for measurement, the bandwidth of the adjacent 9th order sideband is only 0.98GHz away from it, and it is likely to fall into the Brillouin gain spectrum, so two gain peaks may be obtained in the measurement, making the measurement inaccurate.

[0053] Exemplary Methods

[0054] An embodiment of the present invention provides a dynamic BOTDA sensing method based on injection-locked high-order sideband output, the dynamic BOTDA sensing method comprising: dividing the laser output by a light source into a first sub-beam entering a first electro-optical modulator and a second sub-beam entering a second electro-optical modulator; enabling a channel of an arbitrary waveform generator to generate a pulse signal, loading the first sub-beam through the first electro-optical modulator, modulating the first sub-beam from continuous light to pulse light, and entering the optical fiber to be tested as a pulse pump light; enabling another channel of the arbitrary waveform generator to generate an arbitrary wave signal, modulating the second sub-beam through the second electro-optical modulator to generate multi-order sidebands, and allowing the modulated light beam to enter a slave laser to lock a preset sideband in the multi-order sidebands, obtaining a detection light that locks the preset sideband and entering the optical fiber to be tested to generate stimulated Brillouin scattering with the pulse pump light, so as to receive the generated scattered light; each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal.

[0055] A laser (equivalent to the main laser mentioned below) is used as a light source, and the output laser frequency is ν0. The laser output by the laser is divided into two beams, namely a first sub-beam and a second sub-beam. The first sub-beam is used to generate pulsed pump light in a first branch (such as the upper branch described below), and the second sub-beam is used to generate agile frequency detection light in a second branch (such as the lower branch described below), that is, detection light that can quickly change frequency.

[0056] The first sub-beam enters the first electro-optic modulator, and the second sub-beam enters the second electro-optic modulator.

[0057] A channel of the arbitrary waveform generator generates a pulse signal, which is loaded into the first sub-beam through the first electro-optical modulator, and the first sub-beam is modulated from continuous light to pulse light, which enters the optical fiber to be tested as pulse pump light.

[0058] In addition, another channel of the arbitrary waveform generator is made to generate an arbitrary wave signal, and the second sub-beam is modulated by the second electro-optical modulator to generate multi-order sidebands, and the modulated light beam is made to enter the slave laser to lock the preset sideband in the multi-order sidebands, and the light output by the slave laser to lock the preset sideband is used as the detection light for locking the preset sideband, and the detection light for locking the preset sideband is made to enter the optical fiber to be tested and generate stimulated Brillouin scattering with the pulse pump light to generate scattered light. Wherein, each scanning frequency of the arbitrary wave signal corresponds to each pulse of the pulse signal one by one.

[0059] As an example, the operating bandwidth of the arbitrary wave generator may be one of 1.2 GHz, 1.54 GHz, 2.16 GHz, and 3.6 GHz.

[0060] As an example, the preset sideband locked by the slave laser is a high-order sideband among the above-mentioned multi-order sidebands, and the high-order sideband is one of -9th order, -7th order, -5th order, and -3rd order.

[0061] As an example, the preset sideband locked by the slave laser is the -1 order sideband among the above-mentioned multiple order sidebands.

[0062] The dynamic BOTDA sensing method based on injection locked high-order sideband output of the present invention can be based on the above combined Figure 1 The described dynamic BOTDA system based on injection locked high-order sideband output is implemented and can achieve similar functions and the same effects, which will not be described in detail here.

[0063] Preferred Embodiments

[0064] Combine the following Figure 2 To describe this preferred embodiment, in this preferred embodiment, a laser is used as a light source, the output laser frequency is ν0, the upper branch is used to generate pulse pump light, and the lower branch is used to generate frequency-agile detection light.

[0065] The dynamic BOTDA system based on injection-locked high-order sideband output includes a master laser, a slave laser, a 50:50 coupler, two electro-optic modulators (the first and second electro-optic modulators), an arbitrary waveform generator, two microwave amplifiers (the first and second microwave amplifiers), an erbium-doped fiber amplifier, two circulators (the first and second circulators), an optical isolator, a photodetector with a bandwidth of 350 MHz, and an oscilloscope. In the preferred embodiment, a 33 m optical fiber to be tested is used.

[0066] In this preferred embodiment, the laser source is a DFB laser with a wavelength of ν0 (for example, 1530nm), and the emitted laser power is 6mw. It is divided into two paths through an optical coupler, and the uplink light (i.e., the first sub-beam) enters EOM1 (as pump light); the AWG generates a pulse signal, which is amplified by the first microwave amplifier and then loaded into the pump light, modulating the continuous pump light into a pulse pump light. The peak power of the pulse light after modulation by EOM1 is relatively small, and then it enters the erbium-doped fiber amplifier for amplification, and the amplification current parameters are set so that the peak power of the pulse light after amplification is 800mw; then, it is connected to port 1 of CIR1, and enters the inside of the optical fiber to be tested after a section of single-mode jumper after port 2.

[0067] Optionally, before the added light enters the EOM1, it may first pass through a first polarization controller (not shown in the figure) to adjust the polarization state of the light beam so that the polarization state is adjusted to be able to cooperate with the EOM1.

[0068] As the pulsed pump light for generating stimulated Brillouin scattering, it is set so that each pulse corresponds to a frequency in the frequency-agile signal, such as Figure 3 As shown in the figure, the pulse width determines the spatial resolution of the system. After being amplified by the erbium-doped fiber amplifier, it enters the optical fiber to be tested. Figure 3 Here, f1, f2 and f3 represent three frequencies in the detection light (but the frequencies of the detection light are not limited to three, and may be more), and p1, p2 and p3 represent three corresponding pulses in the pump light.

[0069] The downlink light is used as the frequency-agile detection light. The scanning frequency required in the experiment is written into the program, and the AWG is controlled by a computer to perform the frequency sweep. The two are connected by a network cable, including the scanning time of a single frequency, the number of frequencies, and the frequency sweep range. All frequencies are written into the program to control the AWG frequency sweep. Each scanning frequency corresponds to a pulse signal as the modulation signal of the pump light. The pulse signal and the frequency sweep signal should be in a one-to-one correspondence. Each frequency has a pulse interacting with it in the optical fiber to be tested. In addition, the output intensity of the pulse and arbitrary wave signal generated by the AWG is small, and a microwave amplifier can be used to amplify it.

[0070] like Figure 2As shown, the downlink light enters the electro-optic modulator. In the frequency-agile BOTDA system, an AWG is used to generate the modulation signal of the detection light. The duration of each frequency is 650ns, and the frequency sweep range of different sidebands is different. The length of the entire cycle is 400μs. The output intensity of the AWG microwave used in the experiment is 27dBm after amplification. The operating voltage of the electro-optic modulator is adjusted to suppress the carrier. The output light intensity of the electro-optic modulator at the working point is about 200μw. The modulated light enters the circulator (CIR2) port 1, and then enters the slave laser (SL) through port 2. The frequency interval of the slave laser is adjusted to correspond to the swept sideband, so that it can lock and amplify the required sideband. The injection locked output light intensity is the output light intensity of the slave laser 4mw. The detection light enters the optical isolator and then enters the optical fiber to be tested.

[0071] Optionally, before the downlink light enters the EOM2, it may first pass through a second polarization controller (not shown in the figure) to adjust the polarization state of the light beam so that the polarization state is adjusted to be able to cooperate with the EOM2.

[0072] In addition, optionally, a third polarization controller can be arranged between the second circulator 113 and the optical isolator 114, so that the polarization state of the light output from the laser is adjusted by the third polarization controller so that the adjusted polarization state can undergo Brillouin scattering with the pump light in the optical fiber to be tested.

[0073] The modulated light after being modulated by the electro-optic modulator (such as Figure 4 The injected light (shown in Figure 2) enters the slave laser, and the slave laser is injected to lock a certain sideband, such as Figure 4 As shown, as the detection light, it can be modulated with a low-frequency electrical signal to obtain a high-order sideband output, which can reduce the bandwidth of the arbitrary wave and enter the optical fiber to produce a Brillouin scattering effect with the pump light.

[0074] In this preferred embodiment, the pump light and the detection light in the optical fiber to be tested generate Brillouin scattering, and the detection light generates Brillouin gain, enters port 2 of CIR1, and then enters the AC photodetector (PD) through port 3, with a bandwidth of 350MHz, and the experimental results are collected by an oscilloscope. Before data collection, the AWG generates an external trigger signal synchronized with the frequency agility cycle and outputs it to the oscilloscope. When the detection light starts to sweep, it will interact with the pump light. With the sweep time, different gain signals will be recorded on the oscilloscope, and the signal of a sweep cycle will be collected.

[0075] The scattered light is detected by a photodetector and collected by an oscilloscope, so that the Brillouin information of the optical fiber to be tested can be obtained and the state of the optical fiber can be quickly measured.

[0076] According to the embodiments of the present invention, by reducing the bandwidth of microwave devices required in the dynamic distributed Brillouin optical fiber sensing system, the instrument cost of the system can be reduced. Therefore, the above-mentioned technology of the present invention can effectively reduce the bandwidth of microwave devices required, realize dynamic measurement, and provide a dynamic BOTDA system with strong stability and low cost. It will also broaden the application field of the technology and has important economic value and research significance.

[0077] It should be noted that although several units or components of the multimedia object viewing device are mentioned in the above detailed description, this division is only exemplary and not mandatory. In fact, according to an embodiment of the present invention, the features and functions of two or more units or components described above can be embodied in one module. Conversely, the features and functions of one unit or component described above can be further divided into multiple modules for embodiment.

[0078] In addition, although the operations of the method of the present invention are described in a specific order in the drawings, this does not require or imply that the operations must be performed in this specific order, or that all the operations shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps.

[0079] Although the spirit and principle of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the disclosed specific embodiments, and the division of various aspects does not mean that the features in these aspects cannot be combined to benefit, and such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the attached claims.

Claims

1. A dynamic BOTDA sensing method based on injection-locked high-order sideband output, characterized in that: The dynamic BOTDA sensing method comprises: Splitting the laser light outputted by the light source into a first sub-beam entering the first electro-optic modulator and a second sub-beam entering the second electro-optic modulator; A channel of the arbitrary waveform generator generates a pulse signal, which is loaded into the first sub-beam through the first electro-optical modulator, and the first sub-beam is modulated from continuous light to pulse light, which enters the optical fiber to be tested as pulse pump light; another channel of the arbitrary waveform generator generates an arbitrary wave signal, modulates the second sub-beam through a second electro-optical modulator to generate multi-order sidebands, and makes the modulated light beam enter the slave laser to lock a preset sideband in the multi-order sidebands, obtains the detection light locked with the preset sideband and enters the optical fiber to be tested to generate stimulated Brillouin scattering with the pulse pump light, so as to receive the generated scattered light; Wherein, each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal; The preset sideband locked by the slave laser is a high-order sideband among the multi-order sidebands, and the high-order sideband is one or more of -9th order, -7th order, -5th order and -3rd order; The operating bandwidth of the arbitrary waveform generator is any one of 1.2 GHz, 1.54 GHz, 2.16 GHz and 3.6 GHz.

2. A dynamic BOTDA system based on injection-locked high-order sideband output, characterized in that: The dynamic BOTDA system comprises a master laser (101), a slave laser (102), a beam splitting module (103), a first electro-optical modulator (107), a second electro-optical modulator (108), an arbitrary waveform generator (109) and a receiving module; The light beam output by the main laser (101) is divided into a first sub-beam and a second sub-beam by a beam splitting module (103), the first sub-beam enters a first electro-optic modulator (107), a channel of an arbitrary waveform generator (109) is used to generate a pulse signal to be loaded into the first sub-beam through the first electro-optic modulator (107), and the first sub-beam is modulated from continuous light to pulse light, and enters the optical fiber (115) to be tested as pulse pump light; The second sub-beam enters the second electro-optic modulator (108), and another channel of the arbitrary waveform generator (109) is used to generate an arbitrary wave signal, so as to modulate the second sub-beam through the second electro-optic modulator (108) to generate multi-order sidebands, and the modulated light beam enters the slave laser (102) to lock the preset sidebands in the multi-order sidebands, so as to obtain the detection light output by the slave laser (102), and the detection light enters the optical fiber to be tested (115) to generate stimulated Brillouin scattering with the pulse pump light, and the generated scattered light is received by the receiving module; Wherein, each scanning frequency of the arbitrary wave signal corresponds one-to-one to each pulse of the pulse signal; The preset sideband locked by the slave laser is a high-order sideband among the multi-order sidebands, and the high-order sideband is one or more of -9th order, -7th order, -5th order and -3rd order; The operating bandwidth of the arbitrary waveform generator is one of 1.2 GHz, 1.54 GHz, 2.16 GHz, and 3.6 GHz.

3. The dynamic BOTDA system according to claim 2, characterized in that: The beam splitting module (103) is a coupler; the dynamic BOTDA system further comprises a first microwave amplifier, a second microwave amplifier, an erbium-doped fiber amplifier (111), a first circulator (112), a second circulator (113), an optical isolator (114), a photodetector (116) and an oscilloscope (117); wherein, after being output from the coupler, the first sub-beam enters the first electro-optic modulator (107); the pulse signal generated by the arbitrary waveform generator (109) is amplified by the first microwave amplifier and then loaded into the first sub-beam through the first electro-optic modulator (107); the pulse light output from the first electro-optic modulator (107) is amplified by the erbium-doped fiber amplifier (111) and enters the optical fiber to be tested (115) through the first circulator (112); After being output from the coupler, the second sub-beam enters the second electro-optic modulator (108). The arbitrary wave signal generated by the arbitrary waveform generator (109) is amplified by the second microwave amplifier and then modulated by the second electro-optic modulator (108). The modulated light beam enters the slave laser (102) through the second circulator (113). The detection light output from the laser (102) enters the optical fiber to be tested (115) after passing through the second circulator (113) and then through the optical isolator (114) to generate stimulated Brillouin scattering with the pulse pump light. The generated scattered light passes through the first circulator (112) and the photoelectric detector (116) and is received by the oscilloscope (117).

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