CN102589578B - Distributed optical fiber sensing device and method based on phase demodulation - Google Patents
Distributed optical fiber sensing device and method based on phase demodulation Download PDFInfo
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Abstract
The invention discloses a super large dynamic range distributed optical fiber sensing device and method based on phase demodulation. The super large dynamic range distributed optical fiber sensing device comprises a light source, a coupler, an acoustic optical modulator, an optical amplifier, a circulator, a detector, an automatic gain control device, a modulator driving device, a phase-locking amplifier, a sensing optical cable and a signal processing and signal outputting device. The automatic gain control device is adopted in the invention, large dynamic range signal detection can be realized; a phase demodulating detection device of the phase-locked amplifier is adopted, influence of intensity noise is reduced, and high flexibility high bandwidth vibration signal detection can be realized, thus large dynamic range distributed vibration sensing can be realized. The super large dynamic range distributed optical fiber sensing device disclosed by the invention has the beneficial effect that long-distance distributed sensing with the following advantages can be realized: dynamic range is large, locating accuracy is high, interference sensing sensitivity is high, bandwidth used for detecting a vibration signal is wide, multipoint location can be realized, and detection distance is long.
Description
Technical field
The present invention relates to Fibre Optical Sensor and safety protection field, relate in particular to distribution type optical fiber sensing equipment and the method for the super big dynamic range based on phase demodulating.
Background technology
1993, Φ-OTDR (Phase sensitive Opitcal Time Domain Reflector, phase sensitivity time-domain reflectomer) technology was by professor Taylor of agricultural machinery university of U.S. invention (US5194847).This technology, since invention, has received the concern of various countries distributed sensing researchist and company.Φ-OTDR technology is by detected intensity, indirectly realizes the detection to invasion signal.
For Φ-OTDR technology, if realize the long-distance distributed sensing of 80Km, calculate with the loss of 0.2dB/Km, altogether need testing circuit to there is the dynamic range of 32dB.If it is longer to detect distance, need larger dynamic range.This has just proposed very high requirement to detection method.For this problem, some patents have also proposed certain methods, as Hua Wei company applies for a patent: CN101603856A, utilize N photoswitch to realize the measurement of great dynamic range, but this method needs N road photodetector, causes light path system complexity, has greatly improved cost.Hua Wei company applies for a patent: CN101625264A, although utilize logarithmic amplifier to improve sensing range, follow-up still needs realizes and detecting by the way of ride gain, cannot realize automatic gain adjustment.
What in fact, invasion changed is the phase place that light transmits in optical fiber.And traditional Φ-OTDR technology is directly similar to by light intensity the variation that obtains light phase, be easily subject to the impact of light intensity self fluctuation and laser instrument intensity noise (Relative Intensity noise, RIN).
Summary of the invention
In order to solve deficiency of the prior art, the invention provides the distribution type optical fiber sensing equipment based on phase demodulating and method that a kind of dynamic range is large.
The object of the invention is to be achieved through the following technical solutions:
Based on the distribution type optical fiber sensing equipment of phase demodulating, comprise the light source and the sensor fibre that connect successively; Described sensing device further comprises:
The first coupling mechanism, described the first coupling mechanism is coupled into respectively photomodulator, the second coupling mechanism for the light that light source is sent;
Photomodulator, described photomodulator is for being adjusted into continuous light pulsed light and/or adjusting light frequency, and the light after adjustment enters described sensor fibre;
Driver module, the output terminal of described driver module connects respectively described photomodulator, lock-in amplifier;
The second coupling mechanism, the couple light to detector of described the second coupling mechanism for the scattered light of sensor fibre, the first coupling mechanism are sent;
Detector, described detector is used for the scattered light signal receiving to be converted to electric signal, and is sent to automatic gain control module;
Automatic gain control module, described automatic gain control module is for the signal of amplitudes such as described electric signal being adjusted into relatively, and is sent to lock-in amplifier;
Lock-in amplifier, described lock-in amplifier is for the signal of the amplitude such as relative described in demodulation, and reference signal is from described driver module;
Signal processing module, the signal that described signal processing module sends for the treatment of described lock-in amplifier, for knowing the information of described sensor fibre perception.
According to above-mentioned distribution type optical fiber sensing equipment, preferably, described automatic gain control module further comprises:
Gain controlled amplification submodule, the input end of described gain controlled amplification submodule connects described detector, and output terminal connects respectively the input end of described lock-in amplifier, the input end of controlled voltage shaping submodule;
Controlled voltage shaping submodule, the output terminal of described controlled voltage shaping submodule connects the input end of described gain controlled amplification submodule.
According to above-mentioned distribution type optical fiber sensing equipment, alternatively, described sensing device further comprises:
Circulator, the emergent light of described photomodulator enters described sensor fibre by circulator, and the scattered light signal in described sensor fibre is transferred to described the second coupling mechanism.
According to above-mentioned distribution type optical fiber sensing equipment, preferably, described light source is continuous light source.
According to above-mentioned distribution type optical fiber sensing equipment, preferably, described photomodulator is acousto-optic modulator.
The object of the invention is to be also achieved through the following technical solutions:
Distributing optical fiber sensing method based on phase demodulating, said method comprising the steps of:
(A1) the light part that light source sends enters photomodulator by the first coupling mechanism, and another part enters the second coupling mechanism;
(A2) described photomodulator is modulated to continuous light pulsed light and/or adjusts pulse light frequency under driver module effect, and the light after adjustment enters sensor fibre;
(A3) detector is entered in the optically-coupled that the second coupling mechanism sends the scattered light in described sensor fibre, the first coupling mechanism, between the light that described scattered light, the first coupling mechanism send, interferes;
(A4) light signal is converted to electric signal by detector, and be sent to automatic gain control module;
(A5) automatic gain control module is the signal of the amplitudes such as described electric signal is adjusted into relatively, and is sent to lock-in amplifier;
(A6) signal of the amplitude such as relative described in lock-in amplifier demodulation, reference signal is from described driver module;
(A7) signal processing module is processed the signal that described lock-in amplifier sends, thereby knows the information of described sensor fibre perception.
According to above-mentioned method, preferably, described light source is narrow linewidth laser.
According to above-mentioned method, alternatively, described method is further comprising the steps:
(B1) the output light of described photomodulator enters described sensor fibre by circulator, and the scattered light signal in described sensor fibre is transferred to described the second coupling mechanism.
According to above-mentioned method, alternatively, described method is further comprising the steps:
(C1) judge module judges whether the vibration that described signal processing module sends exceeds threshold value, if exceed threshold value, prompting is reported to the police.
Compared with prior art, the present invention has following beneficial effect:
The present invention is on the basis of original Φ-OTDR technology, has proposed to utilize lock-in amplifier to carry out the way of phase demodulating, has realized the Real-time demodulation to light phase.Utilize the method can reduce the intensity noise (RIN) of laser instrument, the noise that the changes in amplitude that minimizing causes due to a variety of causes causes, has improved signal to noise ratio (S/N ratio) greatly.Meanwhile, adopt automatic gain control equipment, can meet great dynamic range required in long distance test, and simple in structure.Based on above improvement, finally realize the distributed measurement of the super big dynamic range based on phase demodulating.
Dynamic range is large, and positioning precision is high, and interference sensing is highly sensitive, detects being with of vibration signal roomy, and can multipoint positioning etc.
Brief description of the drawings
With reference to accompanying drawing, disclosure of the present invention will be easier to understand.Those skilled in the art hold intelligible: these accompanying drawings are only for illustrating technical scheme of the present invention, and are not intended to protection scope of the present invention to be construed as limiting.In figure:
Fig. 1 is the basic block diagram of the distribution type optical fiber sensing equipment of the embodiment of the present invention 1;
Fig. 2 is the process flow diagram of the method for the embodiment of the present invention 1;
Fig. 3 is the basic block diagram of the distribution type optical fiber sensing equipment of the embodiment of the present invention 2;
Fig. 4 is the process flow diagram of the method for the embodiment of the present invention 2.
Embodiment:
Fig. 1-4 and following declarative description optional embodiment of the present invention to instruct those skilled in the art how to implement and to reproduce the present invention.In order to instruct technical solution of the present invention, simplify or omitted some conventional aspects.Those skilled in the art should understand that be derived from these embodiments modification or replace will be within the scope of the invention.Those skilled in the art should understand that following characteristics can combine to form multiple modification of the present invention in every way.Thus, the present invention is not limited to following optional embodiment, and is only limited by claim and their equivalent.
Embodiment 1:
Fig. 1 has schematically provided the basic block diagram of the distribution type optical fiber sensing equipment based on phase demodulating of the embodiment of the present invention, and as shown in Figure 1, described sensing device comprises the light source and the sensor fibre that connect successively; Described light source can adopt laser instrument, as the continous way semiconductor laser of narrow linewidth; Described sensing device further comprises:
The first coupling mechanism, described the first coupling mechanism is coupled into respectively photomodulator, the second coupling mechanism for the light that light source is sent;
Photomodulator, described photomodulator is for being adjusted into continuous light pulsed light and/or adjusting light frequency, and the light after adjustment enters described sensor fibre; Preferably, described photomodulator adopts acousto-optic modulator.
Driver module, the output terminal of described driver module connects respectively described photomodulator, lock-in amplifier, for sending modulation signal to photomodulator, provides reference signal to lock-in amplifier;
The second coupling mechanism, the couple light to detector of described the second coupling mechanism for the scattered light of sensor fibre, the first coupling mechanism are sent; Between the scattered light in sensor fibre, the light that the first coupling mechanism sends, interfere;
Detector, described detector is used for the scattered light signal receiving to be converted to electric signal, and is sent to automatic gain control module;
Automatic gain control module, described automatic gain control module is for the signal of amplitudes such as described electric signal being adjusted into relatively, and is sent to lock-in amplifier;
Preferably, described automatic gain control module further comprises:
Gain controlled amplification submodule, the input end of described gain controlled amplification submodule connects described detector, and output terminal connects respectively the input end of described lock-in amplifier, the input end of controlled voltage shaping submodule;
Controlled voltage shaping submodule, the output terminal of described controlled voltage shaping submodule connects the input end of described gain controlled amplification submodule.Because the output of detector is directly connected with the input of gain controlled circuit.The output voltage U o of gain controlled amplifying circuit, through detection and after wave filter filtering low frequency modulations component and noise, produces the output voltage U c of gain controlled amplifying circuit.In the time that input signal Ui increases, Uo and Uc also increase thereupon.Uc increases declines the gain of gain controlled amplifying circuit, thereby makes the variable quantity of amplitude output signal Uo be significantly smaller than the variable quantity of input signal amplitude Ui, reaches automatic gain control object.As long as input optical power is enough strong, the dynamic range of the detection of whole system depends primarily on automatic gain control equipment, for example reach 60dB for the input dynamic range of automatic gain control equipment, the dynamic range of whole detection system can reach 60dB, meets the length of 150Km (calculating with 0.2dB/Km) apart from detection demand;
Lock-in amplifier, described lock-in amplifier is for the signal of the amplitude such as relative described in demodulation, and reference signal is from described driver module;
Signal processing module, the signal that described signal processing module sends for the treatment of described lock-in amplifier, for knowing the information of described sensor fibre perception.
Fig. 2 has schematically provided the distributing optical fiber sensing method based on phase demodulating of utilizing above-mentioned sensing device, as shown in Figure 2, said method comprising the steps of:
(A1) the light part that light source sends enters photomodulator by the first coupling mechanism, and another part enters the second coupling mechanism;
(A2) described photomodulator is modulated to continuous light pulsed light and/or adjusts pulse light frequency under driver module effect, and the light after adjustment enters sensor fibre;
(A3) detector is entered in the optically-coupled that the second coupling mechanism sends the scattered light in described sensor fibre, the first coupling mechanism, between the light that described scattered light, the first coupling mechanism send, interferes;
(A4) light signal is converted to electric signal by detector, and be sent to automatic gain control module;
(A5) automatic gain control module is the signal of the amplitudes such as described electric signal is adjusted into relatively, and is sent to lock-in amplifier;
(A6) signal of the amplitude such as relative described in lock-in amplifier demodulation, reference signal is from described driver module.The reference signal of lock-in amplifier derives from the drive unit of modulator, and the output signal entering signal of lock-in amplifier gathers and treating apparatus, and signals collecting and treating apparatus are by synchronizing signal control modulator drive unit; Modulator drive unit exports the reference edge of lock-in amplifier to, by lock-in amplifier, the interference signal of amplitude stabilization is carried out to Real-time demodulation.Due to lock-in amplifier demodulation be the phase information of interference signal, therefore this demodulation method has suppressed amplitude noise.The phase information that demodulation output packet has contained optical fiber changes (((t).And the phase place that invasion action causes changes the variation that comprises refractive index n (t) and length L (t), that is:
In formula (1), (be the wavelength of laser instrument, n is refractive index, and L is fiber lengths.Therefore, by the real-time detection to restituted signal, just can realize the detection that the light phase to causing due to invasion action changes, thereby indirectly realize the detection to invasion action;
(A7) signal processing module is processed the signal that described lock-in amplifier sends, thereby knows the information of described sensor fibre perception.
Embodiment 2:
The basic block diagram of the distribution type optical fiber sensing equipment of measuring vibrations when Fig. 3 has schematically provided the embodiment of the present invention, as shown in Figure 3, as different from Example 1:
1, connect successively image intensifer, circulator in the downstream of described photomodulator, described circulator is transferred to the output light of image intensifer in sensor fibre, and the Rayleigh scattering light in sensor fibre is transferred to the second coupling mechanism;
2, described sensing device further comprises judge module and alarm module:
Judge module, described judge module judges whether the parameter that described signal processing module sends exceeds threshold value; Described judge module can adopt circuit or software to realize, and specific implementation is the state of the art, does not repeat them here.
Alarm module, when the judged result of described judge module is when being, described alarm module prompting is reported to the police, can employing sound, the pattern of light or electricity reports to the police.
Fig. 4 has schematically provided the method for utilizing above-mentioned distribution type optical fiber sensing equipment to detect vibration, as shown in Figure 4, and as different from Example 1:
1, the output light of described photomodulator enters described sensor fibre by circulator, and the scattered light signal in described sensor fibre is transferred to described the second coupling mechanism.
2, judge module judges whether the vibration that described signal processing module sends exceeds threshold value, if exceed threshold value, points out alarm module to report to the police.
Embodiment 3:
Based on the distribution type optical fiber sensing equipment of phase demodulating, as different from Example 2: adopt pulsed light source, as the semiconductor laser of narrow linewidth, photomodulator is used for adjusting pulse light frequency.
Claims (9)
1. the distribution type optical fiber sensing equipment based on phase demodulating, comprises the light source and the sensor fibre that connect successively; It is characterized in that: described sensing device further comprises:
The first coupling mechanism, described the first coupling mechanism is coupled into respectively photomodulator, the second coupling mechanism for the light that light source is sent;
Photomodulator, described photomodulator is for being adjusted into continuous light pulsed light and/or adjusting light frequency, and the light after adjustment enters described sensor fibre;
Driver module, the output terminal of described driver module connects respectively described photomodulator, lock-in amplifier;
The second coupling mechanism, the couple light to detector of described the second coupling mechanism for the scattered light of sensor fibre, the first coupling mechanism are sent;
Detector, described detector is used for the scattered light signal receiving to be converted to electric signal, and is sent to automatic gain control module;
Automatic gain control module, described automatic gain control module is for the signal of amplitudes such as described electric signal being adjusted into relatively, and is sent to lock-in amplifier;
Lock-in amplifier, described lock-in amplifier is for the signal of the amplitude such as relative described in demodulation, and reference signal is from described driver module;
Signal processing module, the signal that described signal processing module sends for the treatment of described lock-in amplifier, for knowing the information of described sensor fibre perception.
2. distribution type optical fiber sensing equipment according to claim 1, is characterized in that: described automatic gain control module further comprises:
Gain controlled amplification submodule, the input end of described gain controlled amplification submodule connects described detector, and output terminal connects respectively the input end of described lock-in amplifier, the input end of controlled voltage shaping submodule;
Controlled voltage shaping submodule, the output terminal of described controlled voltage shaping submodule connects the input end of described gain controlled amplification submodule.
3. distribution type optical fiber sensing equipment according to claim 1, is characterized in that: described sensing device further comprises:
Circulator, the emergent light of described photomodulator enters described sensor fibre by circulator, and the scattered light signal in described sensor fibre is transferred to described the second coupling mechanism.
4. distribution type optical fiber sensing equipment according to claim 1, is characterized in that: described light source is continuous light source.
5. distribution type optical fiber sensing equipment according to claim 1, is characterized in that: described photomodulator is acousto-optic modulator.
6. the distributing optical fiber sensing method based on phase demodulating, said method comprising the steps of:
(A1) the light part that light source sends enters photomodulator by the first coupling mechanism, and another part enters the second coupling mechanism;
(A2) described photomodulator is modulated to continuous light pulsed light and/or adjusts pulse light frequency under driver module effect, and the light after adjustment enters sensor fibre;
(A3) detector is entered in the optically-coupled that the second coupling mechanism sends the scattered light in described sensor fibre, the first coupling mechanism, between the light that described scattered light, the first coupling mechanism send, interferes;
(A4) light signal is converted to electric signal by detector, and be sent to automatic gain control module;
(A5) automatic gain control module is the signal of the amplitudes such as described electric signal is adjusted into relatively, and is sent to lock-in amplifier;
(A6) signal of the amplitude such as relative described in lock-in amplifier demodulation, reference signal is from described driver module;
(A7) signal processing module is processed the signal that described lock-in amplifier sends, thereby knows the information of described sensor fibre perception.
7. method according to claim 6, is characterized in that: described light source is narrow linewidth laser.
8. method according to claim 6, is characterized in that: described method is further comprising the steps:
(B1) the output light of described photomodulator enters described sensor fibre by circulator, and the scattered light signal in described sensor fibre is transferred to described the second coupling mechanism.
9. method according to claim 6, is characterized in that: described method is further comprising the steps:
(C1) judge module judges whether the vibration that described signal processing module sends exceeds threshold value, if exceed threshold value, prompting is reported to the police.
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| CN103472003A (en) * | 2013-09-27 | 2013-12-25 | 山东大学 | Novel method used for phase lock voltage subtraction of micro water vapor detection |
| CN104991180A (en) * | 2015-07-15 | 2015-10-21 | 国网智能电网研究院 | Photoelectric detector assembly bandwidth detecting method and device |
| CN106323448B (en) * | 2016-11-23 | 2019-12-03 | 重庆大学 | High-frequency vibration distributed optical fiber sensing system based on stochastical sampling |
| CN106932374A (en) * | 2017-04-17 | 2017-07-07 | 大连理工大学 | Based on the microscope that lock mutually amplifies |
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