TWI855442B - A hybrid distributed optical fiber (sensing) system based on brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry - Google Patents

Abstract

The present invention discloses a distributed optical fiber sensing system that combines Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry. It uses the Rayleigh scattering principle and Brillouin frequency shift characteristics for sensing to measure the temperature value, tension and vibration parameters of the test point.

Description

A distributed optical fiber sensing system that combines Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry

The present invention is an optical fiber sensing system, in particular, a distributed optical fiber sensing system that combines Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry.

In the field of traditional measurement technology, when measurement is required, since a certain length needs to be measured, and each length has different temperature changes or different topography, if only optical fiber sensing is used for measurement, it is difficult to measure the exact position, and it is difficult to distinguish whether it is caused by adverse effects such as temperature or other stresses.

As shown in FIG1 , it is a Brillouin optical time domain analysis measurement system of the prior art, which includes the following components: first, the system light source 1001 provides a laser light source, such as a distributed feedback laser (DFB laser), and then the coupler 1002 separates the pump light source and the detection light source, and the first all-optical fiber element polarization controller 1003 and the second all-optical fiber element polarization controller 1004 adjust the optical polarization state to maximize the power output.

As shown in Figure 1, the signal generator 1005 generates a continuous wave signal to sense the Brillouin frequency of the optical fiber to be tested. The first electro-optical modulator 1006 and the second electro-optical modulator 1007 convert the electrical signal into an optical signal. The pulse pattern generator (PPG) 1008 and the arbitrary waveform generator (AWG) 1009 generate the pulse signal required by the system.

Still as shown in FIG. 1 , the variable optical attenuator 1010 is connected to the optical isolator 1014, and the variable optical attenuator 1010 can adjust the optical power, and the optical isolator 1014 limits the optical path to only connect to the optical fiber to be tested 1015 in a single direction, and the modulator bias controller (MBC) 1011 can automatically adjust the bias to generate a stable output of the pulse signal, and the modulator bias controller 1011 is connected to the computer 1012.

As shown in FIG1 , the computer 1012 is electrically connected to a digital phosphor oscilloscope (DPO) 1013, and the modulator bias controller 1011 is connected to a first erbium-doped optical fiber amplifier 1016, and the first erbium-doped optical fiber amplifier 1016 is connected to a polarization disruptor 1017, and the polarization disruptor 1017 can suppress polarization noise.

Then, as shown in FIG1 , the polarization polarizer 1017 is connected to the variable optical attenuator 1018, the variable optical attenuator 1018 is connected to the optical circulator 1019, connected to the second erbium-doped optical fiber amplifier 1020, and the second erbium-doped optical fiber amplifier 1020 is connected to the adjustable filter 1021, so that the adjustable filter 1021 filters out the required Brillouin scattered light wave band.

Finally, as shown in FIG1 , the adjustable filter 1021 is connected to the photodetector 1022, and the photodetector 1022 is connected to the DC blocker 1023.

Since traditional known technologies such as fiber optic sensing technology can be used to sense and measure any area that stretches over several kilometers to tens of kilometers, and the sensing range is quite wide, the more sensing heads there are, the higher the sensing cost will be, and it is easy to cause light energy insertion loss of the light source. Therefore, although point-by-point fiber optic sensing has precise accuracy in short distances and can determine the correct location of the disturbance, when used for long-distance measurements, the optical fiber to be measured is likely to have a breakpoint, making it impossible for the probe light and the pump laser to interact, which will cause the system to be unable to measure the signal. That is, the Brillouin optical time domain analysis measurement system of the previous technology cannot be used for long-distance measurements.

From the above, we can see that the existing distributed fiber optic sensing and point-by-point fiber optic sensing technologies still need to be improved and enhanced, so further review is needed to find feasible solutions. Therefore, it is necessary to study and improve new fiber optic measurement systems, and the fiber optic measurement systems still need to be updated and commercialized.

The "distributed optical fiber sensing system combining hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry" of the present invention uses the Brillouin scattering principle and Brillouin frequency shift for sensing to measure the temperature value of the object to be measured at any position.

The first embodiment of the present invention, "a distributed optical fiber sensing system combining Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry", comprises the following components: a narrow linewidth optical fiber laser light source, the narrow linewidth optical fiber laser light source is connected to a coupler, and the coupler is connected to a first all-optical fiber element polarization controller, and is simultaneously connected to a second all-optical fiber element polarization controller, a signal generator is connected to an electro-optic modulator, and the first all-optical fiber element polarization controller is connected to the electro-optic modulator, and the electro-optic modulator is further connected to a first variable optical The attenuator is then connected to the optical isolator and the switch, and then to the receiving optical fiber. The second all-optical fiber element polarization controller is used to connect the acousto-optic modulator, and then to the first erbium-doped optical fiber amplifier, and then to the second variable optical attenuator, followed by the optical circulator, and then to the second erbium-doped optical fiber amplifier, and then to the adjustable filter, and then to the photodetector, and then to the DC blocker, and finally to the digital fluorescent oscilloscope. The acousto-optic modulator is connected to the driver, and then to the pulse generator.

The second embodiment of the present invention is a "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflection method", which includes the following elements: a narrow line width optical fiber laser light source, and the narrow line width optical fiber laser light source is connected to a coupler, and then a pump light source and a detection light source are separated by the first coupler, and the first coupler is connected to a first all-optical fiber element polarization controller, and at the same time connected to a second all-optical fiber element polarization controller, and a signal generator is connected to an electro-optic modulator, and the first all-optical fiber element polarization controller is connected to the electro-optic modulator, and the electro-optic modulator is connected to a first variable optical attenuator, and then connected to an optical isolator, and connected to The optical fiber is connected to the switch, and then connected to the receiving optical fiber. The second all-optical fiber element polarization controller is used to connect the acousto-optic modulator, and then connected to the first erbium-doped optical fiber amplifier, and then connected to the second variable optical attenuator, followed by the optical circulator, and then connected to the second erbium-doped optical fiber amplifier, and then connected to the second coupler, and then connected to the first tunable filter and the second tunable filter at the same time, wherein the first tunable filter is connected to the first photodetector, and finally, connected to the digital fluorescent oscilloscope, and the second tunable filter is connected to the second photodetector, and finally, connected to the digital fluorescent oscilloscope, wherein the acousto-optic modulator is connected to the driver, and then connected to the pulse generator.

In order to make the above features of the present invention more clearly understood, the following is a specific example and a detailed description with the accompanying drawings.

1001: System light source

1002: Coupler

1003: All-fiber component polarization controller

1004: All-fiber component polarization controller

1005:Signal generator

1006: The first electro-optical modulator

1007: Second electro-optical modulator

1008: Pulse mode generator

1009: Arbitrary waveform generator

1010: Variable optical attenuator

1011: Modulator bias controller

1012: Computer

1013: Digital fluorescent oscilloscope

1014: Optical isolator

1015: Optical fiber to be tested

1016: The first erbium-doped optical fiber amplifier

1017: Polarization deflector

1018: Variable optical attenuator

1019:Light Circulator

1020: The second erbium-doped optical fiber amplifier

1021:Adjustable filter

1022: Photodetector

1023: DC blocker

200: Distributed fiber optic sensing system based on hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry

2001: Narrow linewidth fiber laser source

2002: Coupler

2003: The first all-optical fiber component polarization controller

2004: The second all-optical fiber polarization controller

2005:Signal Generator

2006:Electro-optical modulator

2007: The first variable optical attenuator

2008: Optical isolator

2009:Switch

2010: Optical fiber to be tested

2011: Sound and light modulator

2012: The first erbium-doped optical fiber amplifier

2013: The second variable optical attenuator

2014: Light Circulator

2015:Driver

2016: Pulse Generator

2017: The second erbium-doped optical fiber amplifier

2018: Tunable filter

2019: Photodetector

2020: DC Blocker

2021: Digital Fluorescent Oscilloscope

2022: Computer

300: Distributed fiber optic sensing system based on hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry

3001: Narrow linewidth fiber laser source

3002: Coupler

3003: The first all-optical fiber component polarization controller

3004: The second all-optical fiber element polarization controller

3005:Signal generator

3006:Electro-optical modulator

3007: The first variable optical attenuator

3008: Optical isolator

3009:Switch

3010: Optical fiber to be tested

3011: Sound and light modulator

3012: The first erbium-doped optical fiber amplifier

3013: Second variable optical attenuator

3014:Light Circulator

3015:Driver

3016: Pulse generator

3017: The second erbium-doped optical fiber amplifier

3018: Second coupler

3019: The first adjustable filter

3020: Second adjustable filter

3021: The first photodetector

3022: Second photodetector

3023: Digital fluorescent oscilloscope

3024: Computer

The aforementioned and other advantages of the present invention will be more clearly presented in the following detailed description of a preferred embodiment with reference to the following figures, as follows: FIG. 1 shows a Brillouin optical time domain analysis measurement system of the prior art; FIG. 2 shows a schematic diagram of a "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflection method" of the first embodiment of the present invention; and FIG. 3 shows a schematic diagram of a "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflection method" of the second embodiment of the present invention.

Since the various aspects and embodiments are only illustrative and non-restrictive, after reading this specification, a person with ordinary knowledge may also have other aspects and embodiments without departing from the scope of the invention. The features and advantages of these embodiments will be more prominent according to the following detailed description and patent application scope.

The "distributed optical fiber sensing system combining hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry" of the present invention uses the Brillouin scattering principle and the Brillouin frequency shift principle to measure the temperature value of the object to be measured at any position.

First, please refer to the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflection method" 200 of the first embodiment of the present invention shown in FIG2. As shown in FIG2, the following components are included: first, a narrow linewidth fiber laser light source (NLFL) 2001 provides a laser light source, and the narrow linewidth fiber laser light source 2001 is connected to a coupler 2002, and then the coupler 2002 separates a pump light source and a detection light source, and the coupler 2002 is connected to a first all-optical fiber element polarization controller (PC) 2003, and is simultaneously connected to a second all-optical fiber element polarization controller (PC). controller, PC) 2004, wherein the first all-optical fiber element polarization controller 2003 and the second all-optical fiber element polarization controller 2004 can adjust the optical polarization state to maximize the power output.

2 shows a schematic diagram of a distributed optical fiber sensing system 200 of the present invention using a hybrid Brillouin optical time domain analysis method and a phase-sensitive optical time domain reflectometry method. A signal generator (SG) 2005 is connected to an electro-optic modulator (EOM) 2006, and the first all-optical fiber element polarization controller 2003 is connected to the electro-optic modulator (EOM) 2006 to generate a continuous wave signal, which can then sense the Brillouin frequency of the optical fiber to be tested. The electro-optic modulator (EOM) 2006 is then connected to a first variable optical attenuator (VOA). attenuator (VOA) 2007, then connect to optical isolator (ISO) 2008, and connect to switch (switch) 2009, and then connect to fiber under test (FUT) 2010.

As shown in FIG. 2 , the schematic diagram of the “distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry” 200 of the present invention is shown. The second all-optical fiber element polarization controller 2004 is connected to an acousto-optic modulator (AOM) 2011, and then connected to a first erbium-doped fiber amplifier (EDFA) 2012, and then connected to a second variable optical attenuator (VOA) 2013, followed by an optical circulator (OC) 2014, and then connected to a second erbium-doped fiber amplifier (EDFA) 2017, and then connected to a tunable filter (tunable filter) 2018, then connected to the photodetector (PD) 2019, then connected to the DC block (DC Block) 2020, and finally connected to the digital phosphor oscilloscope (DPO) 2021.

Still as shown in FIG. 2, the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" 200 of the present invention, wherein the acousto-optic modulator (AOM) 2011 is connected to the driver (driver) 2015, and then connected to the pulse generator (pulse generator, PG) 2016, so as to load the required sine wave signal to generate the detection light, and the computer 2022 transmits signals to and from the driver 2015 and the adjustable filter 218.

In addition, please refer to the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" 300 of the second embodiment of the present invention shown in FIG3. As shown in FIG3, the following components are included: first, a narrow line width optical fiber laser light source 3001 provides a laser light source, and the narrow line width optical fiber laser light source 3001 is connected to a coupler 3002, and then the first coupler 300 2 separates the pump light source and the detection light source, and the first coupler 3002 is connected to the first all-optical fiber element polarization controller 3003 and the second all-optical fiber element polarization controller 3004 at the same time, wherein the first all-optical fiber element polarization controller 3003 and the second all-optical fiber element polarization controller 3004 can adjust the polarization state of the light source so that the power injected into the electro-optic modulator 3006 and the acousto-optic modulator 3011 are both maximum.

As shown in FIG. 3, the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" 300 of the present invention, the signal generator 3005 is connected to the electro-optic modulator 3006, and the first all-optical fiber element polarization controller 3003 is connected to the electro-optic modulator 3006 to generate a continuous wave signal, which can then sense the Brillouin frequency of the optical fiber to be tested. The electro-optic modulator 3006 is then connected to the first variable optical attenuator 3007, then to the optical isolator 3008, and then to the switch 3009, and then to the optical fiber to be tested 3010.

As shown in FIG. 3, the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" 300 of the present invention is shown. The second all-optical fiber element polarization controller 3004 is connected to the acousto-optic modulator 3011, and then connected to the first erbium-doped optical fiber amplifier 3012, and then connected to the second variable optical attenuator 3013, followed by the optical circulator 3014, and then connected to the second erbium-doped optical fiber amplifier. 3017, continues to connect to the second coupler 3018, and simultaneously connects to the first adjustable filter 3019 and the second adjustable filter 3020, wherein the first adjustable filter 3019 is connected to the first photodetector 3021, and finally, is connected to the digital fluorescent oscilloscope 3023, and the second adjustable filter 3020 is connected to the second photodetector 3022, and finally, is connected to the digital fluorescent oscilloscope 3023.

Still as shown in FIG. 3, the schematic diagram of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" 300 of the present invention, wherein the acousto-optic modulator 3011 is connected to the driver 3015, and then connected to the pulse generator 3016, so as to load the required sine wave signal to generate the detection light. The computer 3024 controls the driver 3015 to transmit the signal to the acousto-optic modulator 3011.

The "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry" of the present invention can produce the effect of electro-optic modulator 3006, because electro-optic modulator 3006 has a good light wave frequency shifting effect. Since the present invention requires the frequency difference of two light waves to be matched by Brillouin gain, the characteristics of the light wave frequency shifting effect can be utilized to use electro-optic modulator 3006 to perform optical modulation on the optical path of the laser carrier wave. At this time, the pump laser can generate a pulse signal through the pulse generator 3016, connect to the acousto-optic modulator driver 3015, and modulate the acousto-optic modulator 3011 to the required pump laser. Then, through the first erbium-doped optical fiber amplifier 3012, the pump laser passes through the second variable optical attenuator 3013 to adjust the pump laser and detection light power ratio, and through the optical isolator to limit the pump laser to prevent the pump laser from being transmitted to the non-test area. Therefore, the pump laser of the other path is loaded into the electro-optic modulator 3006 by the sine wave signal generator 3005 to generate the required sine wave signal as the detection light.

The "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry" of the present invention can observe the Brillouin scattered light and the optical signal-to-noise ratio (OSNR) of Rayleigh scattered light under each channel by adjusting the filter channel, and observe the gain of the Brillouin scattered light. In addition, since the incident pump power and the detection light power are both as large as possible, the Brillouin scattered light gain can be improved after the two interact, and the signal-to-noise ratio can be improved. Therefore, when changing the detection light power, the pulse amplitude of the electrical signal should also be paid attention to, as shown in Table 1. By fixing the pump light power, the present invention can observe the gain effect of the Brillouin scattered light as the power of the detection light changes, thereby improving the sensing distance. Table 1 below shows the experimental values:

The basic operating principle of the "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" of the present invention is that when the switch 3009 is set to an open circuit, it is a Brillouin optical time domain analysis method architecture. This architecture uses stimulated Brillouin scattering to pass through the electrostrictive effect in the optical fiber 3010 to be tested, that is, when the interference between the pump light and the back Brillouin scattered light, a beat frequency electric field will be caused. When the power of the Brillouin scattered light itself is relatively small, a beam of reverse incident continuous detection light can be used to interact with the pump light, thereby ensuring that the two beams of light maintain a specific frequency and polarization. When the two beams of light meet, they will produce stimulated Brillouin scattering and transfer energy. The optical signal is received through the first photodetector 3021 and observed through the digital fluorescent oscilloscope 3023. When the switch 3009 is short-circuited, the detection optical path of Brillouin optical time domain analysis (BOTDA) will be blocked. This architecture is the architecture of phase-sensitive optical time domain reflectometry. The narrow linewidth laser 3001 is used as the light source, and the pulse signal required for the experiment is loaded into the acousto-optic modulator 3011. The modulated signal will have a great power loss, so the optical signal is amplified for the first time through the first erbium-doped optical fiber amplifier 3012. Since the detection principle of phase-sensitive optical time domain reflectometry is to use Rayleigh backscattering, and the Rayleigh scattered light is an elastic collision that makes the incident light and the scattered light coherent, the scattered light is received for signal processing. When the incident light enters the optical fiber 3010 to be tested, excessive power will cause stimulated Brillouin scattering light effect and other unnecessary nonlinear effects, making it difficult to process the scattered signal and reducing the SNR of the system. Therefore, the power of the incident light is adjusted through an optical attenuator, and the quality of the incident light is observed using an optical spectrum analyzer. After the light enters the optical fiber to be tested 3010, the back Rayleigh scattered light will be output from port 3 of the optical circulator 3014. After the optical spectrum analyzer observes the light without Rayleigh scattered light, it enters the second erbium-doped optical fiber amplifier 3017 to amplify the optical signal that has been lost due to long-distance transmission for the second time. However, because the second erbium-doped optical fiber amplifier 3017 is used to amplify the optical signal, the optical signal contains a wide-spectrum light source, and the required Rayleigh scattered light is filtered out through the second tunable filter 3020. Finally, it is received by the second photodetector 3022, and the digital fluorescent oscilloscope 3023 is used to capture the signal, and finally the signal is processed.

The advantage of the above embodiment of "distributed optical fiber sensing system of hybrid Brillouin optical time domain analysis method and phase-sensitive optical time domain reflectometry method" is that it is different from traditional detection technology. It can use optical fiber sensing alone for measurement, which is easy to measure the precise position and avoid the influence of other factors. In addition, the above embodiment uses optical fiber sensing technology that can be extended to any interval from several kilometers to tens of kilometers as sensing measurement, and the sensing range is quite wide. In addition, the above embodiment can reduce the sensing cost and reduce the light energy insertion loss of the light source. The optical fiber sensing of the above embodiment has a very precise accuracy over a long distance, and can also determine the correct position where the disturbance occurs.

One of the advantages of the above embodiments is that it utilizes the increase and decrease of the Brillouin frequency of the optical fiber itself, which is caused by the change of the diameter of the optical fiber and the change of the density of the optical fiber. The above is only a preferred embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention; any other equivalent changes or modifications that are completed without departing from the spirit disclosed by the present invention should be included in the scope of the patent application below.

200: Distributed fiber optic sensing system based on hybrid Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry

2001: Narrow linewidth fiber laser source

2002: Coupler

2003: The first all-optical fiber component polarization controller

2004: The second all-optical fiber polarization controller

2005:Signal Generator

2006:Electro-optical modulator

2007: The first variable optical attenuator

2008: Optical isolator

2009:Switch

2010: Optical fiber to be tested

2011: Sound and light modulator

2012: The first erbium-doped optical fiber amplifier

2013: The second variable optical attenuator

2014: Light Circulator

2015:Driver

2016: Pulse Generator

2017: The second erbium-doped optical fiber amplifier

2018: Tunable filter

2019: Photodetector

2020: DC Blocker

2021: Digital Fluorescent Oscilloscope

2022: Computer

Claims (6)

A distributed optical fiber sensing system that combines Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry at least comprises: a narrow linewidth optical fiber laser light source, the narrow linewidth optical fiber laser light source is connected to a coupler, the coupler is connected to a first all-optical fiber element polarization controller, and, at the same time, is connected to a second all-optical fiber element polarization controller, a signal generator is connected to an electro-optic modulator, the first all-optical fiber element polarization controller is connected to the electro-optic modulator, the electro-optic modulator is connected to a first variable optical attenuator, Connect an optical isolator, and connect a switch, connect an optical fiber to be tested, connect an acousto-optic modulator with the second all-optical fiber element polarization controller, connect a first erbium-doped optical fiber amplifier, connect a second variable optical attenuator, connect an optical circulator, connect the second erbium-doped optical fiber amplifier, connect an adjustable filter, connect a photoelectric detector, connect a DC blocker, connect a digital fluorescent oscilloscope, and wherein the acousto-optic modulator is connected to a driver and a pulse generator. The optical fiber sensing system as described in claim 1, wherein the first all-optical fiber element polarization controller and the second all-optical fiber element polarization controller can adjust the optical polarization state so that a power output is maximized. The optical fiber sensing system as described in claim 1, wherein the acousto-optic modulator is connected to the driver and then connected to the pulse generator to load a required sine wave signal to generate a detection light. A distributed optical fiber sensing system that combines Brillouin optical time domain analysis and phase-sensitive optical time domain reflectometry at least comprises: a narrow linewidth optical fiber laser light source, the narrow linewidth optical fiber laser light source is connected to a coupler, the coupler is connected to a first all-optical fiber element polarization controller, and, at the same time, is connected to a second all-optical fiber element polarization controller, a signal generator is connected to an electro-optic modulator, the first all-optical fiber element polarization controller is connected to the electro-optic modulator, the electro-optic modulator is connected to a first variable optical attenuator, connected to an optical isolator, and, connected to a switch, connected to an optical fiber to be tested, and connected to the The second all-optical fiber element polarization controller is connected to an acousto-optic modulator, a first erbium-doped optical fiber amplifier, a second variable optical attenuator, an optical circulator, the second erbium-doped optical fiber amplifier, a second coupler, and a first tunable filter and a second tunable filter, wherein the first tunable filter is connected to a first photodetector and a digital fluorescent oscilloscope, the second tunable filter is connected to a second photodetector and a digital fluorescent oscilloscope, and the acousto-optic modulator is connected to a driver and a pulse generator. The optical fiber sensing system as described in claim 4, wherein the first all-optical fiber element polarization controller and the second all-optical fiber element polarization controller can adjust the optical polarization state so that a power output is maximized. The optical fiber sensing system as described in claim 4, wherein the acousto-optic modulator is connected to the driver and then connected to the pulse generator to load the required sine wave signal to generate a detection light.