CN114235016B - Dynamic BOTDA sensing method and system based on injection-locked high-order sideband output - Google Patents
Dynamic BOTDA sensing method and system based on injection-locked high-order sideband output Download PDFInfo
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- G—PHYSICS
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- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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- G01D5/268—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light using optical fibres
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- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35364—Sensor working in reflection using backscattering to detect the measured quantity using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
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Abstract
本发明的实施方式提供了一种基于注入锁定高阶边带输出的动态BOTDA传感方法及系统。该方法包括：光源输出的激光分为第一子束和第二子束；任意波形发生器的一个信道产生脉冲信号，通过第一电光调制器加载到第一子束，将其从连续光调制为脉冲泵浦光进入待测光纤；任意波形发生器的另一信道产生任意波信号，通过第二电光调制器对第二子束进行调制，产生多阶边带，各阶边带进入从激光器以锁定预设边带，得到锁定预设边带的探测光并进入待测光纤与脉冲泵浦光发生受激布里渊散射，以接收产生的散射光；任意波信号的每个扫描频率与脉冲信号的每个脉冲一一对应。本发明的上述技术，由于注入锁定了高阶边带，可以将任意波带宽要求在动态测量中降低一个量级。
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
The invention relates to the field of distributed optical fiber sensing, in particular to a dynamic BOTDA sensing method and system based on injection locking high-order sideband output.
Background
In recent years, each city in China is in the peak period of infrastructure, such as the key engineering of plateau railways and cross-sea bridges, the durability and the firmness of the key engineering are always key points of engineering attention, and long-term effective monitoring on the railways and the bridges is required. The real-time effective sensing system plays an extremely important role, and can monitor the stress and the temperature change of the bridge road and the building in real time and send out early warning information in time. In addition, in intelligent city construction, widely laid sensing tools can also play a role in intelligent perception on the change of the target city road and the surrounding environment.
Therefore, it is important to research a real-time, effective and low-cost sensing technology, so as to improve the effectiveness and real-time performance of infrastructure monitoring and accelerate the promotion of intelligent city construction. In the sensing system, the optical fiber sensing technology has unique superiority, compared with the traditional electronic sensing device, the optical fiber sensing device has the advantages that the optical fiber is used as a sensing tool, the volume is small, the optical fiber sensing device is portable, the laying of the sensing device is convenient, the electromagnetic interference resistance and the corrosion resistance are high, and in recent years, the optical fiber sensing mode is almost spread in various modern engineering projects.
The scattering type distributed optical fiber sensing technology has been developed rapidly in the last decades, and based on the Rayleigh, brillouin and Raman scattering effects in the optical fiber, the disturbance of the external environment of the optical fiber is measured, and the temperature and stress changes at different positions along the length of the optical fiber can be realized by the measuring mode, so that the distributed optical fiber sensing can be truly realized. The novel sensing technology has been applied to the safety monitoring of major projects such as oil and gas pipelines, rail tunnels, power cables and the like. With the improvement of the optical fiber sensing technology and the reduction of the system cost, the optical fiber sensor can be widely applied to other fields such as national defense, communication and the like.
The distributed Brillouin optical fiber sensing technology senses the change of the temperature and the stress of the external environment by measuring the Brillouin frequency shift and the linewidth of back scattered light based on the Brillouin scattering principle, has high spatial resolution and measurement precision, and can realize long-distance optical fiber sensing. The BOTDA technology is a typical distributed optical fiber sensing technology, and utilizes the stimulated Brillouin scattering effect to obtain the frequency shift and the line width of scattered light by measuring the gain intensity of sweep detection light, so as to finally obtain Brillouin spectrum information.
The conventional BOTDA system measures once for about several tens of seconds to several minutes, and is suitable for static temperature and strain measurement, but is not suitable for instantaneous and rapid measurement. In 2012, researchers have proposed a technology for rapidly implementing BOTDA, bringing the classical BOTDA method into the dynamic sensing field. By using an arbitrary waveform generator capable of rapidly switching between frequencies, the IQ frequency-up technology is utilized to realize rapid frequency sweep of detection light, namely the optical agile technology is limited by the length of an 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.)., so that the rapid measurement of a BOTDA system can be realized, all information of a Brillouin spectrum can be obtained within hundreds of microseconds, and dynamic vibration of thousands of hertz can be measured in rapid dynamic measurement. However, since the brillouin shift in an optical fiber is about 11 GHz, this results in microwave generators and other microwave devices that typically require high bandwidths, which would introduce significant costs. For an emerging technology, reducing the cost of the system is particularly important for the development and popularization of the technology.
Disclosure of Invention
For this reason, an improved BOTDA technology is highly desirable to be able to reduce system costs.
In this context, embodiments of the present invention desirably provide a method and system for dynamic BOTDA sensing based on injection locked higher order sideband output.
In a first aspect of the embodiment of the invention, a dynamic BOTDA sensing method based on injection locking high-order sideband output is provided, and the dynamic BOTDA sensing method comprises the steps of dividing 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 one channel of an arbitrary waveform generator to generate a pulse signal, loading the first sub-beam into the first sub-beam through the first electro-optical modulator, continuously modulating the first sub-beam into pulse light, enabling the pulse light to serve as pulse pump light to enter an optical fiber to be detected, enabling the other 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, enabling the modulated light beam to enter preset sidebands in the multi-order sidebands, obtaining detection light locking the preset sidebands, enabling the detection light entering the optical fiber to be detected and the pulse pump light to generate stimulated Brillouin scattering to receive generated scattered light, and enabling each scanning frequency of the arbitrary wave signal to correspond to each pulse of the pulse signal one by one.
Further, the operating bandwidth of the arbitrary waveform generator is any one of 1.2GHz, 1.54GHz, 2.16GHz and 3.6 GHz.
Further, the preset sidebands locked by the slave laser are higher-order sidebands in the multi-order sidebands, and the higher-order sidebands are one or more of-9 th order, -7 th order, -5 th order and-3 th order.
Further, the preset sideband locked by the slave laser is a-1-order sideband in the multi-order sidebands.
In a second aspect of the embodiment of the invention, a dynamic BOTDA system based on injection locking high-order sideband output is provided, the dynamic BOTDA system comprises 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, a light beam output by the master laser is split into a first sub-beam and a second sub-beam through the beam splitting module, the first sub-beam enters the first electro-optical modulator, one channel of the arbitrary waveform generator is used for generating a pulse signal to be loaded to the first sub-beam through the first electro-optical modulator, the first sub-beam is modulated from continuous light into pulse light as pulse pumping light to enter an optical fiber to be detected, the second sub-beam enters the second electro-optical modulator, the other channel of the arbitrary waveform generator is used for generating an arbitrary wave signal, the second sub-beam is modulated through the second electro-optical modulator, the modulated light beam enters the slave laser to lock preset sidebands in the multi-order sideband, the probe light output by the slave laser is obtained, the probe light enters the optical fiber to be detected, and the pulse scattering light is generated by the optical fiber to be detected, and the pulse scattering light is received by the optical fiber to be detected, and each pulse scattering signal is scanned by the optical fiber to be detected.
The dynamic BOTDA system further comprises a first microwave amplifier, a second microwave amplifier, a erbium-doped fiber amplifier, a first circulator, a second circulator, an optical isolator, a photoelectric detector and an oscilloscope, wherein the first sub-beam is output from the coupler and enters the first electro-optical modulator, pulse signals generated by the arbitrary waveform generator are amplified by the first microwave amplifier and then loaded to the first sub-beam through the first electro-optical modulator, pulse light output by the first electro-optical modulator is amplified by the erbium-doped fiber amplifier and then enters an optical fiber to be detected through the first circulator, the second sub-beam is output from the coupler and then enters the second electro-optical modulator, arbitrary wave signals generated by the arbitrary waveform generator are modulated by the second electro-optical modulator and then enter the laser from the second circulator, and pulse light output from the laser enters the optical fiber to be detected through the optical isolator and then enters the optical fiber to be detected through the optical fiber to be detected, and then the second sub-beam is scattered through the laser pump.
Further, the working bandwidth of the arbitrary waveform generator is one of 1.2GHz, 1.54GHz, 2.16GHz and 3.6 GHz.
Further, the preset sidebands locked from the laser are higher-order sidebands of the multi-order sidebands, and the higher-order sidebands are one or more of-9, -7, -5 and-3.
Further, the preset sideband locked by the slave laser is a-1-order sideband in the multi-order sidebands.
According to the dynamic BOTDA sensing method and system based on injection locking high-order sideband output, provided by the embodiment of the invention, an ultra-fast measurement scheme of distributed optical fiber strain or temperature is provided, the ultra-fast measurement scheme is modulated by using a low-frequency microwave signal through an injection locking technology, and the high-order sideband or the first-order sideband is locked to output the amplified high-order sideband to carry out frequency sweeping so as to generate a Brillouin signal, so that the reduction of the microwave bandwidth requirement can be realized. The invention can reduce the microwave bandwidth requirement by one order of magnitude in dynamic measurement from 10.8GHz to about 1.2GHz, and has higher stability and higher spatial resolution.
The dynamic BOTDA sensing method and system based on injection locking high-order sideband output have the following advantages:
1. ultra-fast measurements of distributed strain and temperature can be achieved. The dynamic BOTDA measurement can be realized by only a low-bandwidth microwave device, and the sampling frequency of the dynamic BOTDA measurement is only related to the length of the optical fiber to be measured and the average signal number of times.
2. The detection light is modulated by using low-frequency microwaves by utilizing the characteristic of injection locking, so that the first-order or high-order sidebands generated by locking modulation of a laser are output, and the bandwidth of microwave modulation can be reduced by one order of magnitude.
3. The patent can reduce the bandwidth requirement on the basis of dynamic BOTDA, but can realize other performances of the traditional dynamic BOTDA.
Drawings
The above, as well as additional purposes, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description when read in conjunction with the accompanying drawings. Several embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:
FIG. 1 is a schematic diagram illustrating one example structure of a dynamic BOTDA system based on injection locked high order sideband output according to one embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating another example structure of a dynamic BOTDA system based on injection locked high order sideband output according to an embodiment of the present invention;
FIG. 3 is a schematic diagram showing the stimulated Brillouin scattering process of optical agile probe light and pump light in an optical fiber under test;
Fig. 4 is a schematic diagram illustrating injection locking of high order sidebands.
In the drawings, the same or corresponding reference numerals indicate the same or corresponding parts.
Detailed Description
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 presented merely to enable those skilled in the art to better understand and practice the invention and are not intended to limit the scope of the invention in any way. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In this document, it should be understood that any number of elements in the drawings is for illustration and not limitation, and that any naming is used for distinction only and not for any limiting sense.
The principles and spirit of the present invention are explained in detail below with reference to several representative embodiments thereof.
Exemplary apparatus
The embodiment of the invention provides a dynamic BOTDA system based on injection locking high-order sideband output, which comprises a main laser, a slave laser, a beam splitting module, a first electro-optic modulator, a second electro-optic modulator, an arbitrary waveform generator and a receiving module, wherein a beam output by the main laser is divided into a first sub-beam and a second sub-beam through the beam splitting module, the first sub-beam enters the first electro-optic modulator, one channel of the arbitrary waveform generator is used for generating a pulse signal to be loaded to the first sub-beam through the first electro-optic modulator, the first sub-beam is modulated continuously into pulse light as pulse pumping light to enter an optical fiber to be detected, the second sub-beam enters the second electro-optic modulator, the other channel of the arbitrary waveform generator is used for generating an arbitrary wave signal to modulate the second sub-beam through the second electro-optic modulator, the modulated beam enters the slave laser to lock a preset sideband to obtain detection light output by the slave laser, the detection light enters the optical fiber to be detected and the pulse pump to generate a pulse signal, and the pulse signal is scattered by the arbitrary waveform generator to be scanned by the receiving module, and each pulse signal is scattered by the arbitrary wave scanning module.
Fig. 1 schematically illustrates one example of a dynamic BOTDA system based on injection locked high order sideband output in accordance with an embodiment of the present disclosure.
As shown in fig. 1, the dynamic BOTDA system includes a master Laser 101 (i.e., laser in fig. 1), a slave Laser 102 (i.e., SL in fig. 1), a beam splitting module 103, a first electro-optic modulator 107 (i.e., EOM1 in fig. 1), a second electro-optic modulator 108 (i.e., EOM2 in fig. 1), an arbitrary waveform generator 109 (i.e., AWG in fig. 1), and a receiving module.
The main laser 101 is used as a light source, and the frequency of the laser output is v 0, and the laser output is split into two beams, namely a first sub-beam and a second sub-beam by the beam splitting module 103, wherein the first sub-beam is used for generating pulse pumping light in a first branch (an upper branch shown in fig. 1), and the second sub-beam is used for generating agile detection light in a second branch (a lower branch shown in fig. 1), namely detection light with a fast frequency changing.
The beam splitting module 103 is, for example, a coupler (OC shown in fig. 2), and the beam splitting ratio of the coupler may be, for example, 50:50, or may be another value, for example, 40:60, or 20:80.
The first sub-beam enters the first electro-optical modulator 107, and one channel (CH 1 shown in fig. 1) of the arbitrary waveform generator 109 is used to generate a pulse signal, so that the pulse signal is loaded into the first sub-beam by the first electro-optical modulator 107, and the first sub-beam is modulated from continuous light into pulse light, and enters the optical fiber to be measured 115 (FUT shown in fig. 1) as pulse pump light.
In one embodiment of the present invention, as shown in fig. 2, the dynamic BOTDA system may include a erbium doped fiber amplifier 111 (i.e., the EDFA in fig. 2), a first circulator 112 (i.e., the CIR1 in fig. 2), a photodetector 116 (i.e., the PD in fig. 2), and an oscilloscope 117 (i.e., the DAQ in fig. 2), as shown in fig. 1, so that the first sub-beam is output from the coupler 103 and enters the first electro-optical modulator 107, the pulse signal generated by the arbitrary waveform generator 109 is amplified by a first microwave amplifier (not shown in the figure) and then is loaded into the first sub-beam by the first electro-optical modulator 107, and the pulse light output from the first electro-optical modulator 107 is amplified by the erbium doped fiber amplifier 111 and then enters one side of the optical fiber 115 to be measured (as shown in fig. 2) through the first circulator 112 (1-port and 2-port exit from the upper branch).
Referring to fig. 1, the second sub-beam enters the second electro-optic modulator 108, and another channel (CH 2 as shown in fig. 1) of the arbitrary waveform generator 109 is used to generate an arbitrary wave signal to modulate the second sub-beam by the second electro-optic modulator 108 to generate multi-order sidebands. Each sweep frequency of the arbitrary wave signal is in one-to-one correspondence with each pulse of the pulse signal. The modulated second sub-beam enters the slave laser 102 to lock a predetermined sideband in the second sub-beam, i.e., the predetermined sideband in the multi-order sidebands, by the slave laser 102.
The predetermined sideband locked from the laser 102 may be the-1-order sideband of the multi-order sidebands described above, or may be the higher-order sideband. The higher order sidebands are, for example, one of-9 th order, -7 th order, -5 th order, and-3 rd order.
It should be noted that, in the embodiments of the present invention, the 1 st order or the higher order refers to the negative order, that is, the negative 1 st order, or the negative higher order (e.g., -9 th order, -7 th order, -5 th order, -3 th order), and for convenience, the 1 st order or the higher order (e.g., 9 th order, etc.) sometimes referred to hereinafter also refers to the negative sideband.
The slave laser 102 is an injection locked laser that is locked and amplifies the desired sidebands (e.g., 1 st order sidebands and/or higher order sidebands) of the modulated second sub-beam by adjusting the frequency range of the slave laser 102's oscillation so that the desired sidebands fall within the oscillation frequency range.
As shown in fig. 1, the probe light output from the laser 102 enters the optical fiber to be measured 115 and the pulse pumping light to generate stimulated brillouin scattering, and the generated scattered light is received by the receiving module.
In one embodiment of the invention, as shown in FIG. 2, the dynamic BOTDA system may include a second microwave amplifier (not shown), a second circulator 113 (CIR 2), and an optical isolator 114 (ISO). The second sub-beam is output from the coupler 103, then enters the second electro-optical modulator 108, any wave signal generated by any wave generator 109 is amplified by the second microwave amplifier, then the second sub-beam is modulated by the second electro-optical modulator 108, the modulated light beam enters the slave laser 102 after passing through the second circulator 113, the detection light output from the laser 102 enters the optical fiber 115 to be detected after passing through the second circulator 113, and then enters the optical isolator 114 to be stimulated Brillouin scattering with the pulse pumping light, and the generated scattered light is received by the oscilloscope 117 through the first circulator 112 (from the 2 port inlet and the 3 port outlet of the first circulator) and the photoelectric detector 116.
Here, "Pump pulse" shown in fig. 2 represents a pumping pulse, i.e., the above-described pulsed pumping light, and "Probe wave" represents Probe light.
In an embodiment of the present invention, the operating bandwidth of the arbitrary wave generator may be one of 1.2GHz, 1.54GHz, 2.16GHz, 3.6 GHz.
In embodiments of the present invention, a microwave source may be used in place of the AWG in sensing the slow signal. The microwave source drives the electro-optic modulator to generate each sideband to shift the carrier frequency, and the pulse generator drives the electro-optic modulator to generate pulse light, so that the high-order sidebands are locked by injection from the laser, and the reduction of the microwave bandwidth requirement can be realized.
In one example, the working bandwidth of the arbitrary wave generator is 1.2GHz, the preset sideband locked by the laser 102 is 9 th order, the bandwidth of the 9 th order is 1.2ghz×9=10.8 GHz, in this example, the bandwidth of the detection light after the output of the laser 102 locking the 9 th order sideband is 10.8GHz, and when the detection light after injection locking in this example is input into the optical fiber to be tested and the pulse pump light generates brillouin scattering, the measurement of the brillouin gain can be realized, the requirement on the bandwidth of the device is only 1.2GHz, and the cost of the device is greatly reduced. In the prior art, the microwave generator (arbitrary waveform generator) and other microwave devices for realizing the 10.8GHz bandwidth measurement are huge in cost, and the embodiment only needs the microwave generator (arbitrary waveform generator) and other microwave devices for meeting the 1.2GHz bandwidth requirement, so that the system cost is greatly reduced.
In addition, in another example, the operating bandwidth of the arbitrary wave generator is 1.2GHz, the preset sideband locked from the laser 102 is 1 st order, the bandwidth of 1 st order is 1.2GHz, the bandwidth of 9 th order is 1.2ghz×9=10.8 GHz, in this example, the bandwidth of the probe light after the laser 102 locks the 1 st order sideband output (the portion corresponding to the 1 st order sideband) is 1.2GHz, but some 9 th order sidebands are still amplified (some other higher order sidebands are amplified, such as 3 rd order to 7 th order), when the probe light outputted after the injection locking in this example is inputted into the optical fiber to be detected and the pulse pump light is subjected to the brillouin scattering, the 1 st order sideband of 1.2GHz is not able to measure the brillouin gain, and the bandwidth of 3 rd to 7 th order sidebands is not in accordance with the brillouin gain, and the brillouin gain is not affected because it is far from the 9 th order sidebands (e.g., 7 th order to 9 th order 2.4GHz,5 th order to 9 th order 4.8GHz,3 th order to 9 GHz), and the brillouin gain is not affected (i.e.e.g., the brillouin gain is not affected). In experiments, the feasibility of this protocol was confirmed, yielding very good measurements.
In the above two examples, no matter the 1 st order or the 9 th order sidebands are locked, the 9 th order sidebands which are used for actually performing the brillouin gain measurement are all used, and only a microwave generator (any waveform generator) with a bandwidth of 1.2GHz and other microwave devices are needed to realize the measurement of the brillouin gain of 10.8GHz, so that the measurement bandwidth can be reduced from 10.8GHz to 1/9, namely to 1.2GHz, which is close to 1 order of magnitude.
In embodiments of the present invention, in addition to the 9 th order sidebands, 3-7 th order sidebands or higher order sidebands may also be employed. But the effect of measuring with the 9 th order sidebands is best compared to the 3-7 th order sidebands or more than 11 th order (including 11 th order), because the bandwidth requirements for the 3-7 th order sidebands are respectively 10.8GHz +.3=3.6 GHz,10.8GHz +.5=2.16 GHz,10.8GHz +.7=1.54 GHz, the bandwidths are respectively reduced, but there is no more reduction of the 1.2GHz of the 9 th order, so the cost of the 9 th order corresponding reduction is higher, and for the 11 th order more sidebands, taking the 11 th order as an example, 10.8GHz +.11=0.98 GHz, that is, if the 11 th order sidebands are used for measurement, the adjacent 9 th order sidebands are only 0.98GHz from the distance, and likely fall within the brillouin gain spectrum, so two gain peaks can be obtained in the measurement, and the measurement is inaccurate.
Exemplary method
The embodiment of the invention provides a dynamic BOTDA sensing method based on injection locking high-order sideband output, which comprises the steps of dividing 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 one channel of an arbitrary waveform generator to generate pulse signals, loading the first sub-beam into the first sub-beam through the first electro-optical modulator, modulating the first sub-beam from continuous light into pulse light as pulse pumping light, enabling the other channel of the arbitrary waveform generator to generate arbitrary wave signals, modulating the second sub-beam through the second electro-optical modulator to generate multi-order sidebands, enabling the modulated light beam to enter a preset sideband in the multi-order sidebands, obtaining detection light locking the preset sidebands and enabling the detection light entering the optical fiber to be tested and the pulse pumping light to generate stimulated Brillouin scattering so as to receive the generated scattered light, and enabling each scanning frequency of the arbitrary wave signals to correspond to each pulse of the pulse signals one by one.
The laser (corresponding to the main laser mentioned below) is used as a light source, and the frequency of the laser output is v 0, and the laser output is divided into two beams, namely a first sub-beam and a second sub-beam, wherein the first sub-beam is used for generating pulse pumping light in a first branch (an upper branch described below), and the second sub-beam is used for generating frequency agile detection light in a second branch (a lower branch described below), i.e. detection light capable of rapidly changing the frequency.
Wherein the first sub-beam enters the first electro-optic modulator and the second sub-beam enters the second electro-optic modulator.
A channel of the arbitrary waveform generator is enabled to generate a pulse signal, the pulse signal is loaded to a first sub-beam through a first electro-optical modulator, the first sub-beam is modulated into pulse light from continuous light, and the pulse light is used as pulse pump light to enter an optical fiber to be tested.
In addition, another channel of the random waveform generator is made to generate random wave signals, the second sub-beam is modulated by the second electro-optical modulator to generate multi-order sidebands, the modulated light beam enters the slave lasers to lock preset sidebands in the multi-order sidebands, light which is output from the lasers and locks the preset sidebands is used as detection light for locking the preset sidebands, and the detection light which locks the preset sidebands enters the optical fiber to be tested and is stimulated Brillouin scattering is generated 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.
By way of example, the operating bandwidth of the arbitrary wave generator may be one of 1.2GHz, 1.54GHz, 2.16GHz, 3.6 GHz.
As an example, the preset sidebands locked from the laser are the higher-order sidebands of the above-mentioned multi-order sidebands, and the higher-order sidebands are one of-9 th order, -7 th order, -5 th order, and-3 th order.
As an example, the preset sideband locked from the laser is the-1 st order sideband of the above-mentioned multi-order sidebands.
The dynamic BOTDA sensing method based on injection locking high-order sideband output can be realized based on the dynamic BOTDA system based on injection locking high-order sideband output described above in connection with FIG. 1, and can achieve similar functions and achieve the same effects, and the details are not repeated here.
PREFERRED EMBODIMENTS
The preferred embodiment is described below in conjunction with fig. 2, in which a laser is used as the light source and outputs laser light having a frequency v 0, an upper arm for generating pulsed pump light, and a lower arm for generating agile probe light.
The dynamic BOTDA system based on injection locking high order sideband output comprises a master laser, a slave laser, a 50:50 coupler, two electro-optic modulators (first and second electro-optic modulators), an arbitrary waveform generator, two microwave amplifiers (first and second microwave amplifiers), a erbium-doped fiber amplifier, two circulators (first and second circulators), an optical isolator, a 350MHz bandwidth photodetector and an oscilloscope, and in the preferred embodiment, a 33m fiber under test is used.
In the preferred embodiment, the laser source is a DFB laser with wavelength of v 0 (for example, 1530 nm), the emitted laser power is 6mw, the laser is divided into two paths by an optical coupler, the upper light (namely, the first sub beam) enters EOM1 (as pump light), the AWG generates pulse signals, the pulse signals are amplified by a first microwave amplifier and then loaded to the pump light, and the continuous pump light is modulated into pulse pump light. The pulse light peak power after EOM1 modulation is smaller, then enters an erbium-doped fiber amplifier to be amplified, and an amplifying current parameter is set to enable the pulse light peak power after amplification to be 800mw, then, a1 port of CIR1 is connected, and a section of single-mode jumper after 2 ports enters the inside of an optical fiber to be detected.
Alternatively, the uplink light may be passed through a first polarization controller (not shown) to adjust the polarization state of the beam of light before entering EOM1, so that the polarization state is adjusted to work with EOM 1.
As pulsed pump light generating stimulated brillouin scattering, which is set so that each pulse corresponds to one frequency in the agile signal, as shown in fig. 3, the pulse width thereof determines the spatial resolution of the system, the pulses are amplified by the erbium-doped fiber amplifier and then enter the fiber under test, where f1, f2 and f3 in fig. 3 represent 3 frequencies (but the frequencies of the probe light are not limited to 3, but may be more) in the probe light, and p1, p2 and p3 represent 3 pulses corresponding thereto in the pump light, respectively.
The light of the lower road is used as frequency agility detection light, the scanning frequency needed in the experiment is written into the program, the computer is used for controlling the AWG to sweep frequency, the two are connected by a network cable, the scanning time of single frequency, the number of frequencies and the sweeping range are included, and all the frequencies are written into the program for controlling the AWG to sweep frequency. Each scanning frequency corresponds to a pulse signal to be used as a modulation signal of the pump light, the pulse signal and the sweep frequency signal are in one-to-one correspondence, and each frequency has a pulse interaction with the pulse signal in the optical fiber to be tested. In addition, the output intensity of the pulse and the arbitrary wave signal generated by the AWG is small, and the pulse and the arbitrary wave signal can be amplified by using a microwave amplifier.
As shown in fig. 2, the drop light enters an electro-optic modulator, and an AWG is used in a frequency agile BOTDA system to generate modulated signals of probe light, each frequency duration is 650ns, different sideband sweep ranges are different, and the whole period length is 400 mus. The output intensity of the AWG microwaves used in the experiment is 27dBm after being amplified, the working voltage of the electro-optical modulator is adjusted to inhibit carrier wave, and the output light intensity of the electro-optical modulator at the working point is about 200 mu w. The modulated light enters the 1 port of the circulator (CIR 2), then enters the Slave Laser (SL) through the 2 port, the frequency interval of the slave laser is adjusted to correspond to the frequency sweep sideband, the required sideband can be locked and amplified, and the injection locking output light intensity is 4 mw of the output light intensity of the slave laser. The probe light enters the optical isolator and then enters the optical fiber to be tested.
Alternatively, the downlink light may be passed through a second polarization controller (not shown) to adjust the polarization state of the beam of light before entering EOM2, so that the polarization state is adjusted to work with EOM 2.
In addition, a third polarization controller may be optionally disposed between the second circulator 113 and the optical isolator 114, so that the light output from the laser may be polarized by the third polarization controller, so that the polarized light after being adjusted may be brillouin scattered with the pump light in the optical fiber to be measured.
The modulated light (the injected light shown in fig. 4) modulated by the electro-optical modulator enters the slave laser, and the slave laser injects and locks a certain sideband, as shown in fig. 4, as the probe light, the modulated light can be modulated by using a low-frequency electric signal, high-order sideband output can be obtained, the reduction of any wave bandwidth can be realized, and the brillouin scattering effect occurs between the entering optical fiber and the pump light.
In the preferred embodiment, the pump light and the probe light in the optical fiber to be tested generate brillouin scattering, the probe light generates brillouin gain, the probe light enters the 2 ports of the CIR1, then enters the alternating current Photoelectric Detector (PD) from the three ports, the bandwidth is 350MHz, and the experimental result is acquired through the oscilloscope. Before data acquisition, the AWG generates an external trigger signal synchronous with the frequency agility period and outputs the external trigger signal to the oscilloscope, and the external trigger signal interacts with pump light when the frequency sweeping of the probe light is started. Along with the sweep frequency time, different gain signals are recorded on an oscilloscope, and signals of one sweep frequency period are collected.
The scattered light is detected by the photoelectric detector and is collected by the oscilloscope, so that Brillouin information of the optical fiber to be detected can be obtained, and the state of the optical fiber can be rapidly measured.
According to the embodiment of the invention, the instrument cost of the system can be reduced through the reduction of the bandwidth of the microwave device required by the dynamic distributed Brillouin optical fiber sensing system, so that the bandwidth of the microwave device required by the technology can be effectively reduced, dynamic measurement is realized, a dynamic BOTDA system with strong stability and low cost is provided, the application field of the technology can be widened, and the technology has important economic value and research significance.
It should be noted that while several units or components of the multimedia object viewing apparatus are mentioned in the above detailed description, such a division is merely exemplary and not mandatory. Indeed, the features and functions of two or more units or components described above may be embodied in one module in accordance with embodiments of the invention. Conversely, the features and functions of one unit or component described above may be further divided into a plurality of modules to be embodied.
Furthermore, although the operations of the methods of the present invention are depicted in the drawings in a particular order, this is not required or implied that the operations be performed in that particular order or that all of the illustrated operations be performed to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step to perform, and/or one step decomposed into multiple steps to perform.
While the spirit and principles of the present invention have been described with reference to several particular embodiments, it is to be understood that the invention is not limited to the disclosed embodiments nor does it imply that features of the various aspects are not useful in combination, nor are they useful in any combination, such as for convenience of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (3)
1. The dynamic BOTDA sensing method based on injection locking high-order sideband output is characterized by comprising the following steps of:
Dividing the laser output by the light source into a first sub-beam entering the first electro-optical modulator and a second sub-beam entering the second electro-optical modulator;
a channel of an arbitrary waveform generator generates a pulse signal, the pulse signal is loaded to a first sub-beam through a first electro-optical modulator, the first sub-beam is modulated into pulse light from continuous light, and the pulse light is used as pulse pump light to enter an optical fiber to be tested;
Enabling another channel of the random waveform generator to generate random wave signals, modulating a second sub-beam through a second electro-optical modulator to generate multi-order sidebands, enabling the modulated light beams to enter a slave laser to lock preset sidebands in the multi-order sidebands, obtaining detection light locking the preset sidebands, entering an optical fiber to be tested and generating stimulated Brillouin scattering with the pulse pumping light, and receiving generated scattered light;
wherein, each scanning frequency of the arbitrary wave signal corresponds to each pulse of the pulse signal one by one;
the preset sidebands locked by the slave laser are high-order sidebands in the multi-order sidebands, and the high-order sidebands are one or more of-9 th order, -7 th order, -5 th order and-3 th order;
The operating bandwidth of the arbitrary waveform generator is any one of 1.2GHz, 1.54GHz, 2.16GHz and 3.6 GHz.
2. The dynamic BOTDA system based on injection locking high-order sideband output is characterized by comprising a master laser (101), a slave laser (102), a beam splitting module (103), a first electro-optic modulator (107), a second electro-optic 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-optical modulator (107), one channel of an arbitrary waveform generator (109) is used for generating a pulse signal so as to be loaded to the first sub-beam through the first electro-optical modulator (107), and the first sub-beam is modulated into pulse light from continuous light and enters an optical fiber (115) to be tested as pulse pump light;
the second sub-beam enters a second electro-optical modulator (108), the other channel of the arbitrary waveform generator (109) is used for generating an arbitrary wave signal, the second sub-beam is modulated by the second electro-optical modulator (108) to generate multi-order sidebands, the modulated light beam enters a slave laser (102) to lock preset sidebands in the multi-order sidebands, the detection light output by the slave laser (102) is obtained, the detection light enters an optical fiber (115) to be detected and the pulse pump light are subjected to stimulated Brillouin scattering, and the generated scattered light is received by a receiving module;
wherein, each scanning frequency of the arbitrary wave signal corresponds to each pulse of the pulse signal one by one;
the preset sidebands locked by the slave laser are high-order sidebands in the multi-order sidebands, and the high-order sidebands are one or more of-9 th order, -7 th order, -5 th order and-3 th order;
The working bandwidth of the arbitrary waveform generator is one of 1.2GHz, 1.54GHz, 2.16GHz and 3.6 GHz.
3. The dynamic BOTDA system of claim 2, wherein the beam splitting module (103) is a coupler, the dynamic BOTDA system further comprising a first microwave amplifier, a second microwave amplifier, a erbium-doped fiber amplifier (111), a first circulator (112), a second circulator (113), an optical isolator (114), a photodetector (116), and an oscilloscope (117);
The first sub-beam is output from the coupler and enters the first electro-optical modulator (107), a pulse signal generated by the arbitrary waveform generator (109) is amplified by the first microwave amplifier and then is loaded to the first sub-beam by the first electro-optical modulator (107), and pulse light output from the first electro-optical modulator (107) is amplified by the erbium-doped optical fiber amplifier (111) and enters the optical fiber (115) to be tested by the first circulator (112);
the second sub-beam is output from the coupler and enters the second electro-optical modulator (108), any wave signal generated by the random wave generator (109) is amplified by the second microwave amplifier and then modulated by the second electro-optical 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 (115) to be detected through the optical isolator (114) and is subjected to stimulated Brillouin scattering with the pulse pumping light, and the generated scattered light is received by the oscilloscope (117) through the first circulator (112) and the photoelectric detector (116).
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