Multi-parameter distributed optical fiber sensing device and measurement method based on chaotic laser

Abstract

The present invention relates to the field of distributed optical fiber sensing, and discloses a multi-parameter distributed optical fiber sensing device based on chaotic laser and a measuring method. The device includes a photon integrated chaotic laser, a narrow linewidth laser, a first optical switch, a first optical splitter, an electro-optic modulator, an erbium-doped optical fiber amplifier, a programmable optical delay line, an isolator, an SOA pulse modulator, a pulse optical amplifier, an optical switch, a first optical circulator, a bandpass filter, a first photodetector, an acquisition card, a computer, a Raman detection module, a second photodetector, and a third photodetector. The present invention can simultaneously realize the simultaneous real-time coordinated measurement of temperature, strain and loss along the optical fiber, and greatly improves the spatial resolution and sensing distance of the system.

Description

Technical Field

[0001] The invention relates to the field of distributed optical fiber sensing, and in particular to a multi-parameter distributed optical fiber sensing device and a measuring method based on chaotic laser. Background Art

[0002] Distributed fiber optic sensing technology has been widely used in the safety monitoring of linear infrastructure such as urban pipelines, oil / gas pipelines, bridges, rail transit, reservoirs and dams due to its advantages of distribution, electrical insulation, corrosion resistance, and electromagnetic resistance. The current distributed fiber optic sensing technology has the following limitations:

[0003] (1) Currently, distributed fiber optic sensing technology can only measure a single physical quantity. However, in actual engineering applications, abnormal conditions are often accompanied by the simultaneous changes of multiple physical parameters. Therefore, monitoring only a single physical parameter cannot meet the safety monitoring needs of the modern industrial field.

[0004] (2) Existing distributed fiber optic sensing technologies based on Rayleigh scattering and Raman scattering are limited by pulse width, and their spatial resolution is difficult to exceed 1m.

[0005] (3) The current detection method of distributed optical fiber sensing technology has a technical bottleneck of low signal-to-noise ratio, and its sensing distance cannot exceed 100 km.

[0006] Based on this, it is necessary to improve the existing fiber optic sensing technology in order to solve the technical bottleneck that the existing distributed fiber optic sensing technology cannot achieve multi-parameter collaborative detection, and at the same time optimize and improve the spatial resolution and sensing distance of the system. Summary of the invention

[0007] The present invention overcomes the shortcomings of the prior art and provides a multi-parameter distributed optical fiber sensing device and a measurement method based on chaotic laser in order to solve the technical bottleneck that the existing distributed optical fiber sensing device cannot realize multi-parameter collaborative detection and the problem that the spatial resolution and sensing distance of the system are limited.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: a multi-parameter distributed optical fiber sensing device based on chaotic laser, comprising: a photon integrated chaotic laser, a narrow linewidth laser, a first optical switch, a first optical splitter, an electro-optic modulator, an erbium-doped optical fiber amplifier, a programmable optical delay line, an isolator, a SOA pulse modulator, a pulse optical amplifier, an optical switch, a first optical circulator, a bandpass filter, a first photodetector, an acquisition card, a computer, a Raman detection module, a second photodetector, and a third photodetector;

[0009] The laser output ends of the photon integrated chaotic laser and the narrow linewidth laser are connected to the input end of the first optical splitter via an optical switch, the first output end of the first optical splitter is connected to the input end of the erbium-doped fiber optical amplifier via an electro-optical modulator, and the output end of the erbium-doped fiber optical amplifier is connected to interface a via a programmable optical delay line and an isolator; the second output end of the first optical splitter is connected to the input end of the pulse optical amplifier via an SOA pulse modulator, the output end of the pulse optical amplifier is connected to the first port of the first optical circulator via the first output end of the second optical switch, the second port of the first optical circulator is connected to interface b, and the third port is connected to the first photodetector via a bandpass filter;

[0010] The second output end of the second optical switch is connected to the first port of the wavelength division multiplexer, the second port of the wavelength division multiplexer is connected to the interface c, and the third port is connected to the Raman detection module;

[0011] The third output end of the second optical switch is connected to the input end of the coupler, the first output end of the coupler is connected to the first port of the second optical circulator, the first port of the second optical circulator is connected to the interface d, and the third port is connected to the third photodetector; the second output end of the coupler is connected to the second photodetector;

[0012] The interface a and the interface b are respectively connected to the two ends of the strain sensing optical fiber, the interface c is connected to one end of the temperature sensing optical fiber, and the interface d is connected to one end of the loss sensing optical fiber. The output signals of the first photodetector, the second photodetector, the third photodetector and the Raman detection module are connected to the computer via an acquisition card.

[0013] The multi-parameter distributed optical fiber sensing device based on chaotic laser also includes a bias control board and a second splitter. The second splitter is arranged between the electro-optic modulator and the erbium-doped fiber optical amplifier and is used to divide the optical signal output by the electro-optic modulator into two parts, one part is sent to the bias control board, and the other part is sent to the erbium-doped fiber optical amplifier.

[0014] The first optical splitter is a 1×2 polarization-maintaining coupler.

[0015] The multi-parameter distributed optical fiber sensing device based on chaotic laser also includes an attenuator for attenuating the optical signal entering the SOA pulse modulator.

[0016] In addition, the present invention also provides a multi-parameter distributed optical fiber sensing method based on chaotic laser, which is implemented based on the multi-parameter distributed optical fiber sensing device based on chaotic laser, including: temperature detection, strain detection and loss detection;

[0017] The steps of strain detection are:

[0018] S101, controlling the first optical switch to allow the chaotic laser emitted by the photon integrated chaotic laser to pass through, and controlling the second optical switch to allow the first output end thereof to output an optical signal; and collecting the Brillouin signal containing strain information detected by the first photodetector through an acquisition card;

[0019] S102, using a computer to analyze and process the Brillouin signal to obtain a strain change at a certain point of the detection optical fiber, and finally obtain a stress distribution along the optical fiber;

[0020] The steps of temperature detection are:

[0021] S201, Calibration stage:

[0022] S2011, setting the temperature of the temperature sensing optical fiber to T0;

[0023] S2012, control the first optical switch to allow the chaotic laser emitted by the photon integrated chaotic laser to pass through, control the second optical switch to allow the second output end of the optical switch to output an optical signal; then modulate the chaotic laser into a chaotic pulse laser with a pulse width of W through the SOA pulse modulator; collect the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module through the acquisition card;

[0024] S2013, control the first optical switch to allow the laser emitted by the narrow linewidth laser to pass through, control the second optical switch to allow the second output end of the switch to output an optical signal; then modulate the switch into a chaotic pulse laser with a pulse width of W+△ through the SOA pulse modulator; collect the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module through the acquisition card; △ represents the pulse width difference;

[0025] S2014, calculating and obtaining a calibrated anti-Stokes signal intensity difference and a calibrated Stokes signal intensity difference along the temperature sensing optical fiber;

[0026] S202, measurement phase:

[0027] S2021, repeat the operation of step S2012 to obtain a first measured anti-Stokes signal strength and a first measured Stokes signal strength along the temperature sensing optical fiber;

[0028] S2022, repeating the operation of step S2013 to obtain a second measured anti-Stokes signal strength and a second measured Stokes signal strength along the temperature sensing optical fiber;

[0029] S2023, calculating and obtaining a measured anti-Stokes signal strength difference and a measured Stokes signal strength difference;

[0030] S203, calculating the temperature along the sensing optical fiber, the calculation formula is:

[0031]

[0032] Where Δν is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant; φ as (L) and φ s (L) represents the difference between the measured anti-Stokes signal intensity and the measured Stokes signal intensity at the temperature sensing optical fiber L position; φ asc (L) and φ sc (L) represents the difference in the intensity of the calibrated anti-Stokes signal and the difference in the intensity of the calibrated Stokes signal at the position L of the temperature sensing optical fiber;

[0033] The steps of loss detection are:

[0034] S301, controlling the first optical switch to allow the chaotic laser emitted by the photon integrated chaotic laser to pass through, and controlling the second optical switch to allow the third output end thereof to output an optical signal; collecting the chaotic reference pulse signal and the Rayleigh scattering signal respectively detected by the second photodetector and the third photodetector through an acquisition card;

[0035] S302, using a computer to calculate and obtain loss variation information along the loss sensing optical fiber.

[0036] In step S2014, the calculation formula of the calibrated anti-Stokes signal strength difference and the calibrated Stokes signal strength difference along the temperature sensing optical fiber is:

[0037] φ asc (L) = φ asc2 (L)-φ asc1 (L);

[0038] φ sc (L) = φ sc2 (L)-φ sc1 (L);

[0039] Among them, φ asc1 (L) and φ sc1 (L) represents the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity at the temperature sensing optical fiber L position; φ asc2 (L) and φ sc2 (L) represents the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity at the position of the temperature sensing optical fiber L;

[0040] In step S2023, the calculation formula for the measured anti-Stokes signal strength difference and the measured Stokes signal strength difference along the temperature sensing optical fiber is:

[0041] φ as (L) = φ as2 (L)-φ as1 (L);

[0042] φ s (L) = φ s2 (L)-φ s1 (L);

[0043] Among them, φ as1 (L) and φ s1 (L) respectively represent the first measured anti-Stokes signal intensity and the first measured Stokes signal intensity at the temperature sensing optical fiber L position; φ s2 (L) and φ as2 (L) represent the second measured anti-Stokes signal intensity and the second measured Stokes signal intensity at the temperature sensing optical fiber L position, respectively.

[0044] The value of △ is 0.1ns.

[0045] In step S302, the method for calculating the loss change information along the loss sensing optical fiber is:

[0046] The chaotic pulse reference signal and the Rayleigh scattering signal are cross-correlated to obtain the cross-correlation coefficient, which is calculated as follows:

[0047]

[0048] in, represents the mutual correlation coefficient at the sensing fiber l, N represents the time length of the received Rayleigh scattered signal and the chaotic pulse reference signal, Z(l, t) represents the intensity of the Rayleigh scattered light generated at the loss sensing fiber l at time t, and X(t) represents the intensity of the chaotic pulse reference signal at time t;

[0049] Then, the loss factor is obtained from the slope of the cross-correlation coefficient.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. Compared with the existing distributed optical fiber sensing device, the present invention can simultaneously realize the real-time coordinated measurement of temperature, strain and loss along the optical fiber;

[0052] 2. The detection signal used by the device of the present invention is composed of chaotic laser and differential pulse signal. The chaotic signal is a laser signal with low coherence state, and its coherence function presents the shape of delta function. In theory, this coherence length determines that the spatial resolution of the present invention is independent of the sensing distance. This fundamentally solves the technical problem that the spatial resolution of the existing distributed optical fiber sensing technology is limited by the pulse width. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A schematic structural diagram of a multi-parameter distributed optical fiber sensing device based on chaotic laser provided in an embodiment of the present invention;

[0054] In the figure, 1: photon integrated chaotic laser; 2: narrow linewidth laser; 3: first optical switch; 4: first spectrometer; 5: microwave signal source; 6: electro-optic modulator; 7: bias control board; 8: second spectrometer; 9: erbium-doped fiber optical amplifier; 10: programmable optical delay line; 11: isolator; 12: attenuator; 13: signal generator; 14: SOA pulse modulator; 15: pulse optical amplifier; 16: second optical switch; 17: first optical circulator; 18: bandpass filter; 19: photodetector; 20: computer; 21: acquisition card; 22: Raman detection module; 23: wavelength division multiplexer; 24: coupler; 25: photodetector; 26: photodetector; 27: second optical circulator; a: optical fiber strain interface; b: optical fiber strain interface; c: optical fiber temperature interface; d: optical fiber loss interface. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0056] like Figure 1 As shown, an embodiment of the present invention provides a multi-parameter distributed optical fiber sensing device based on chaotic laser, including: a photon integrated chaotic laser 1, a narrow linewidth laser 2, a first optical switch 3, a first optical splitter 4, an electro-optical modulator 6, an erbium-doped fiber optical amplifier 9, a programmable optical delay line 10, an isolator 11, an SOA pulse modulator 14, a pulse optical amplifier 15, a second optical switch 16, a first optical circulator 17, a bandpass filter 18, a first photodetector 19, an acquisition card 21, a computer 20, a Raman detection module 22, a second photodetector 25, and a third photodetector 26.

[0057] The laser output ends of the photon integrated chaotic laser 1 and the narrow linewidth laser 2 are connected to the input end of the first optical splitter 4 via the first optical switch 3, the first output end of the first optical splitter 4 is connected to the input end of the erbium-doped fiber optical amplifier 9 via the electro-optical modulator 6, and the output end of the erbium-doped fiber optical amplifier 9 is connected to the interface a via the programmable optical delay line 10 and the isolator 11; the second output end of the first optical splitter 4 is connected to the input end of the pulse optical amplifier 15 via the SOA pulse modulator 14, the output end of the pulse optical amplifier 15 is connected to the first port of the first optical circulator 17 via the first output end of the second optical switch 16, the second port of the first optical circulator 17 is connected to the interface b, and the third port is connected to the first photodetector 19 via the bandpass filter 18.

[0058] The second output end of the second optical switch 16 is connected to the first port of the wavelength division multiplexer 23, the second port of the wavelength division multiplexer 23 is connected to the interface c, and the third port is connected to the Raman detection module 22; the third output end of the second optical switch 16 is connected to the input end of the coupler 24, the first output end of the coupler 24 is connected to the first port of the second optical circulator 27, the first port of the second optical circulator 27 is connected to the interface d, and the third port is connected to the third photodetector 26; the second output end of the coupler 24 is connected to the second photodetector 25; the interface a and the interface b are respectively connected to the two ends of the strain sensing optical fiber, the interface c is connected to one end of the temperature sensing optical fiber, and the interface d is connected to one end of the loss sensing optical fiber; the output signals of the first photodetector 19, the second photodetector 25, the third photodetector 26 and the Raman detection module 22 are connected to the computer 20 via the acquisition card 21.

[0059] Specifically, a multi-parameter distributed optical fiber sensing device based on chaotic laser in this embodiment further includes a bias control board 7 and a second optical splitter 8, wherein the second optical splitter 8 is arranged between the electro-optic modulator 6 and the erbium-doped fiber optical amplifier 9, and is used to divide the optical signal output by the electro-optic modulator 6 into two parts, one part is sent to the bias control board 7, and the other part is sent to the erbium-doped fiber optical amplifier 9. The bias control board 7 controls the bias voltage of the electro-optic modulator 6 according to the output light intensity of the electro-optic modulator 6, thereby keeping the output light intensity of the electro-optic modulator 6 stable.

[0060] Specifically, in this embodiment, the first optical splitter 4 is a 1×2 polarization-maintaining coupler.

[0061] Furthermore, the chaotic laser-based multi-parameter distributed optical fiber sensing device of this embodiment further includes an adjustable attenuator 12 for adjusting the intensity of the optical signal entering the SOA pulse modulator 14 .

[0062] Specifically, in this embodiment, the operating wavelength of the photon integrated chaotic laser 1 and the narrow linewidth laser 2 is 1550nm. The linewidth of the narrow linewidth laser is less than MHz, and in this application, it is specifically 2.9KHz. The second port of the wavelength division multiplexer 23 is a com port, and the wavelengths of the first port and the third port are 1550nm and 1450nm respectively.

[0063] The working principle of this embodiment is described in detail below.

[0064] 1. Strain detection along the optical fiber.

[0065] This embodiment uses a chaotic modulated Brillouin light coherence domain analysis system to achieve ultra-long distance and high-resolution stress detection, which uses the frequency shift and power change of Brillouin scattered light and the strain change inside the optical fiber to obtain the spatial stress field distribution along the optical fiber. The specific measurement method is as follows:

[0066] The photon integrated chaotic laser 1 emits a chaotic laser of 1550nm, passes through the first optical switch 3, and is divided into two paths by the optical splitter 4, one path is used as pump light, and the other path is used as detection light. The pump light is injected into the electro-optic modulator 6 for modulation, passes through the second optical splitter 8, is amplified by the erbium-doped fiber optical amplifier 9, passes through the programmable optical delay line 10, and finally is injected into one end of the strain sensing optical fiber through the isolator 11 and the interface a; the detection light is injected into the SOA pulse modulator 14 through the attenuator 12 for modulation into a pulse light, and the pulse light is amplified by the pulse amplifier 15, enters the circulator 17 through the second optical switch 16, and is injected into the other end of the strain sensing optical fiber through the interface b. Then the pump light and the detection light interfere with each point of the sensing fiber. The interfered light carries the Brillouin signal containing strain information and enters the bandpass filter 18, where it is filtered out. It undergoes photoelectric conversion through the first photodetector 19, and finally the Brillouin Stokes signal intensity power is collected through the acquisition card 21. The power information is demodulated to obtain the Brillouin gain spectrum, so that the computer 20 analyzes and processes the signal to obtain the strain change at a certain point of the detection fiber, and finally obtains the stress distribution along the fiber. (The frequency shift and power change of the Brillouin scattered light in the optical fiber have a certain linear relationship with the strain change inside the optical fiber. When the temperature / strain at a certain point of the detection fiber changes, the frequency and power of the backward Brillouin scattered signal light change accordingly.)

[0067] The chaotic detection light is sideband modulated by an electro-optical modulator 6 to generate frequency-detuned Brillouin-Stokes light, and the Stokes light and pump light transmitted in opposite directions in the optical fiber are used to generate stable stimulated Brillouin scattering, and the power information of stimulated Brillouin scattering is collected in real time by a data acquisition card. During the detection process, the pump light and the detection light interact sequentially at correlation peaks at different positions, so the Brillouin gain at different correlation peaks can be obtained by analyzing the timing of the detection light, and the programmable optical delay line 10 is used to select the order of the correlation peak to achieve distributed measurement along the optical fiber.

[0068] 2. Temperature detection along the optical fiber line.

[0069] Calibration stage: (i) The chaotic laser emitted by the photon integrated chaotic laser 1 passes through the first optical switch 3, and is injected into the SOA pulse modulator 14 through the optical splitter 4 and the attenuator 12 for pulse modulation into a pulse chaotic laser with a pulse width of W. After being amplified by the pulse amplifier 15, it passes through the second optical switch 16 and the wavelength division multiplexer 23, and then is injected into the temperature sensing optical fiber through the interface c, wherein the incident light collides inelasticly with the molecules in the optical fiber to generate spontaneous Raman scattering, thereby generating spontaneous Raman scattered light at each position of the temperature sensing optical fiber. The backward spontaneous Raman scattered light passes through the wavelength division multiplexer 23, and the Raman detection module 22 collects the required anti-Stokes signal intensity and Stokes signal intensity to the acquisition card 21. The temperature along the temperature sensing optical fiber is controlled to be T0.

[0070] Among them, the first calibration Raman anti-Stokes signal intensity is obtained as:

[0071]

[0072] The intensity of the first calibrated Raman-Stokes signal intensity is obtained as:

[0073]

[0074] In the formula, φ asc1 (L) represents the first anti-Stokes signal intensity collected by the data acquisition card 21 at the temperature sensing optical fiber L position during the calibration phase, φ sc1 (L) represents the Stokes signal intensity collected by the acquisition card 21 at the temperature sensing optical fiber L position during the calibration phase. When the pulse width is W, L i The light intensity information collected by the acquisition card 21 at position L is the accumulation of light intensity information from the length [L-Wc / 2n~L]. (Because the positioning principle used is the pulse time flight method, this method makes the information collected by the acquisition card at a certain moment not the light intensity information of a point at the optical fiber position L, but the superposition of the light intensity information of a section of optical fiber with a sensing distance equal to half the pulse scale). P is the incident power of the pulse laser, K as , Ks They represent the coefficients related to the Raman anti-Stokes signal intensity, the Raman Stokes signal intensity backscattering cross section, S is the backscattering factor of the optical fiber, ν as , ν s They represent the frequencies of Raman anti-Stokes scattering signal and Raman Stokes scattering signal, respectively, e represents the pulsed laser flux coupled into the optical fiber, Δν is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, T0 is the ambient temperature of the entire sensing optical fiber during the calibration phase, α0, α as , α s are the loss coefficients of incident light, anti-Stokes light and Stokes light per unit length in the temperature measuring optical fiber, n represents the refractive index of the sensing optical fiber, and c represents the speed of light.

[0075] (II) After the laser emitted by the narrow linewidth laser 2 passes through the same path as in the previous (I), a laser with a pulse width of W+△ is injected into the temperature sensing optical fiber through the interface c, and the pulse width is controlled by the SOA pulse modulator. The Raman anti-Stokes signal intensity and Raman Stokes signal intensity generated in the temperature sensing optical fiber are collected into the acquisition card 21. Due to the change in pulse width, what the acquisition card 21 collects at the L position is the accumulation of light intensity information from the optical fiber with a length of [L-(W+0.1)c / 2n~L]. In this embodiment, the value of △ is 0.1ns and the value of W is 100ns.

[0076] Then the second calibration anti-Stokes signal strength is:

[0077]

[0078] The second calibration Stokes signal strength is:

[0079]

[0080] (iii) By performing difference calculation on the intensities of the anti-Stokes and Stokes signals generated by the two different pulse width pulse lasers, the light intensity information along the sensing optical fiber in the calibration phase can be collected, namely, the difference in the intensity of the calibrated anti-Stokes signal and the difference in the intensity of the calibrated Stokes signal.

[0081] The calculation formula is:

[0082]

[0083]

[0084] φ asc (L) and φ sc(L) represents the difference between the calibrated anti-Stokes signal intensity and the calibrated Stokes signal intensity at the temperature sensing optical fiber L position; φ asc1 (L) and φ sc1 (L) represents the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity at the temperature sensing optical fiber L position; φ asc2 (L) and φ sc2 (L) represents the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity at the temperature sensing optical fiber L position.

[0085] Measurement phase: Repeat the same measurement process as the calibration phase above, obtain the Raman anti-Stokes and Raman Stokes signal intensities twice for processing, and use the light intensity information along the sensing optical fiber collected in the measurement phase as the collected light intensity information. The measured anti-Stokes signal intensity difference and the measured Stokes signal intensity difference are obtained by the above difference calculation method.

[0086] The calculation formula is:

[0087]

[0088]

[0089] Where T is the temperature along the sensing optical fiber. as (L) and φ s (L) represents the difference between the measured anti-Stokes signal intensity and the measured Stokes signal intensity at the temperature sensing optical fiber L position; φ as1 (L) and φ s1 (L) respectively represent the first measured anti-Stokes signal intensity and the first measured Stokes signal intensity at the temperature sensing optical fiber L position; φ s2 (L) and φ as2 (L) represent the second measured anti-Stokes signal intensity and the second measured Stokes signal intensity at the temperature sensing optical fiber L position, respectively.

[0090] Calculation stage: The light intensity information in the calibration stage and the measurement stage is subjected to temperature demodulation, and finally the distributed temperature information along the sensing optical fiber is obtained. The calculation method is as follows:

[0091] Dividing formula (5) by (6), we can obtain:

[0092]

[0093] Dividing formula (7) by (8), we can get:

[0094]

[0095] Calculate formulas (9) and (10) to obtain the distributed temperature information along the optical fiber:

[0096]

[0097] In the formula, φ as (L) and φ s (L) represents the difference between the measured anti-Stokes signal intensity and the measured Stokes signal intensity at the temperature sensing optical fiber L position; φ asc (L) and φ sc (L) represents the difference in the calibrated anti-Stokes signal intensity and the difference in the calibrated Stokes signal intensity at the position L of the temperature sensing optical fiber.

[0098] 3: Detection of optical fiber loss along the line.

[0099] The chaotic laser emitted by the photon integrated chaotic laser 1 passes through the first optical switch 3, the first optical splitter 4, enters the attenuator 12, and is injected into the 14 SOA pulse modulator for modulation. After being amplified by the pulse amplifier 15, it passes through the second optical switch 16, and then passes through the coupler 24 to be divided into two paths of chaotic pulse reference light and chaotic pulse pump light. The chaotic pulse reference light passes through the second photodetector 25 and enters the acquisition card 21. The chaotic pulse pump light is injected into the loss sensing optical fiber through the second optical circulator 27 and the interface d. The backward Rayleigh scattered signal in the loss sensing optical fiber carries the loss information of various places on the sensing optical fiber. Then the backward Rayleigh scattered signal passes through the second optical circulator 27, and the signal with loss information is obtained through the third photodetector 26 and enters the acquisition card 21. Finally, the computer 20 performs cross-correlation operation on the chaotic pulse reference light signal and the Rayleigh scattered signal of the reference path, and finally obtains the loss change information along the optical fiber. The cross-correlation formula is as follows:

[0100]

[0101] In the formula, represents the mutual correlation coefficient at the sensing fiber l, N represents the time length of the backscattered signal generated by the received chaotic pulse pump light and the chaotic pulse reference light, Z(l, t) represents the intensity of the Rayleigh scattered light generated at the fiber l at time t, and X(t) represents the intensity of the chaotic pulse reference signal at time t. The graph of is a straight line with a slope equal to the loss coefficient.

[0102] Based on the principle of pulse time-of-flight method, the spatial resolution in traditional systems is limited by the pulse width; while the sensing device of this invention uses a chaotic laser, whose coherence function presents a delta function-like shape. Based on this principle, the spatial resolution is determined by the half-maximum full width of the chaotic laser; therefore, the spatial resolution of this system depends on the half-maximum full width of the peak on the cross-correlation curve between the chaotic laser's own signal and the Rayleigh signal scattered in the optical fiber, that is, it is determined by the bandwidth of the chaotic laser and is no longer limited by the pulse width of the light source in traditional systems.

[0103] In summary, this embodiment provides a multi-parameter distributed optical fiber sensing device based on chaotic laser, which integrates temperature sensing, strain sensing and loss sensing, and realizes the integration of multi-parameter sensing.

[0104] Embodiment 2

[0105] Embodiment 2 of the present invention provides a multi-parameter distributed optical fiber sensing method based on chaotic laser, which is implemented based on a multi-parameter distributed optical fiber sensing device based on chaotic laser described in Embodiment 1, and includes: temperature detection, strain detection and loss detection.

[0106] The steps of strain detection are:

[0107] S101, controlling the first optical switch 3 to allow the chaotic laser emitted by the photon integrated chaotic laser 1 to pass through, and controlling the second optical switch 16 to allow the first output end thereof to output an optical signal; and collecting the Brillouin signal containing strain information detected by the first photodetector 19 through the acquisition card 21;

[0108] S102, using the computer 20 to analyze and process the Brillouin signal to obtain the strain variation at a certain point of the detection optical fiber, and finally obtain the stress distribution along the optical fiber.

[0109] The steps of temperature detection are:

[0110] S201, Calibration stage:

[0111] S2011. Set the temperature of the temperature sensing optical fiber to T0.

[0112] S2012, control the first optical switch 3 to allow the chaotic laser emitted by the photon integrated chaotic laser 1 to pass through, control the second optical switch 16 to allow the second output end of the optical switch to output an optical signal; then modulate the chaotic laser into a chaotic pulse laser with a pulse width of W through the SOA pulse modulator 14; collect the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module 22 through the acquisition card 21

[0113] S2013, control the first optical switch 3 to allow the laser emitted by the narrow linewidth laser 2 to pass through, control the second optical switch 16 to allow its second output end to output an optical signal; then modulate it into a chaotic pulse laser with a pulse width of W+△ through the SOA pulse modulator 14; collect the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module 22 through the acquisition card 21; △ represents the pulse width difference; the value of △ is 0.1ns.

[0114] S2014. Calculate and obtain a calibrated anti-Stokes signal intensity difference and a calibrated Stokes signal intensity difference along the temperature sensing optical fiber.

[0115] Among them, the calculation formula of the calibrated anti-Stokes signal intensity difference and the calibrated Stokes signal intensity difference along the temperature sensing optical fiber is:

[0116] φ asc (L) = φ asc2 (L)-φ asc1 (L); (13)

[0117] φ sc (L) = φ sc2 (L)-φ sc1 (L); (14)

[0118] Among them, φ asc1 (L) and φ sc1 (L) represents the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity at the temperature sensing optical fiber L position; φ asc2 (L) and φ sc2 (L) represents the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity at the position of the temperature sensing optical fiber L;

[0119] In step S2023, the calculation formula for the measured anti-Stokes signal strength difference and the measured Stokes signal strength difference along the temperature sensing optical fiber is:

[0120] φ as (L) = φ as2 (L)-φ as1 (L); (15)

[0121] φ s (L) = φ s2 (L)-φ s1 (L); (16)

[0122] Among them, φ as1 (L) and φ s1(L) respectively represent the first measured anti-Stokes signal intensity and the first measured Stokes signal intensity at the temperature sensing optical fiber L position; φ s2 (L) and φ as2 (L) represent the second measured anti-Stokes signal intensity and the second measured Stokes signal intensity at the temperature sensing optical fiber L position, respectively.

[0123] S202, measurement phase:

[0124] S2021, repeat the operation of step S2012 to obtain a first measured anti-Stokes signal strength and a first measured Stokes signal strength along the temperature sensing optical fiber;

[0125] S2022, repeating the operation of step S2013 to obtain a second measured anti-Stokes signal strength and a second measured Stokes signal strength along the temperature sensing optical fiber;

[0126] S2023, calculating and obtaining a measured anti-Stokes signal strength difference and a measured Stokes signal strength difference;

[0127] S203, calculating the temperature along the sensing optical fiber, the calculation formula is:

[0128]

[0129] Where Δν is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant; φ as (L) and φ s (L) represents the difference between the measured anti-Stokes signal intensity and the measured Stokes signal intensity at the temperature sensing optical fiber L position; φ asc (L) and φ sc (L) represents the difference in the calibrated anti-Stokes signal intensity and the difference in the calibrated Stokes signal intensity at the position L of the temperature sensing optical fiber.

[0130] The steps of loss detection are:

[0131] S301, controlling the first optical switch 3 to allow the chaotic laser emitted by the photon integrated chaotic laser 1 to pass through, and controlling the second optical switch 16 to allow the third output end thereof to output an optical signal; collecting the chaotic reference pulse signal and the Rayleigh scattering signal detected by the second photodetector 25 and the third photodetector 26 respectively through the acquisition card 21;

[0132] S302, using the computer 20 to calculate and obtain loss variation information along the loss sensing optical fiber.

[0133] Among them, the chaotic pulse reference signal and the Rayleigh scattering signal are cross-correlated to obtain the cross-correlation coefficient, and the calculation formula is:

[0134]

[0135] in, represents the mutual correlation coefficient at the sensing fiber l, N represents the time length of the received Rayleigh scattered signal and the chaotic pulse reference signal, Z(l, t) represents the intensity of the Rayleigh scattered light generated at the loss sensing fiber l at time t, and X(t) represents the intensity of the chaotic pulse reference signal at time t;

[0136] Then, the loss factor is obtained from the slope of the cross-correlation coefficient.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-parameter distributed optical fiber sensing device based on chaotic laser, characterized in that: include: Photon integrated chaotic laser (1), narrow linewidth laser (2), first optical switch (3), first optical splitter (4), electro-optic modulator (6), erbium-doped fiber optical amplifier (9), programmable optical delay line (10), isolator (11), SOA pulse modulator (14), pulse optical amplifier (15), second optical switch (16), first optical circulator (17), bandpass filter (18), first photodetector (19), acquisition card (21), computer (20), Raman detection module (22), second photodetector (25), third photodetector (26); The laser output ends of the photon integrated chaotic laser (1) and the narrow linewidth laser (2) are connected to the input end of the first optical splitter (4) via the first optical switch (3); the first output end of the first optical splitter (4) is connected to the input end of the erbium-doped fiber optical amplifier (9) via the electro-optic modulator (6); the output end of the erbium-doped fiber optical amplifier (9) is connected to the interface a via the programmable optical delay line (10) and the isolator (11); the second output end of the first optical splitter (4) is connected to the input end of the pulse optical amplifier (15) via the SOA pulse modulator (14); the output end of the pulse optical amplifier (15) is connected to the first port of the first optical circulator (17) via the first output end of the second optical switch (16); the second port of the first optical circulator (17) is connected to the interface b; and the third port is connected to the first photodetector (19) via the bandpass filter (18); The second output end of the second optical switch (16) is connected to the first port of the wavelength division multiplexer (23), the second port of the wavelength division multiplexer (23) is connected to the interface c, and the third port is connected to the Raman detection module (22); The third output end of the second optical switch (16) is connected to the input end of the coupler (24), the first output end of the coupler (24) is connected to the first port of the second optical circulator (27), the first port of the second optical circulator (27) is connected to the interface d, and the third port is connected to the third photodetector (26); the second output end of the coupler (24) is connected to the second photodetector (25); The interface a and the interface b are respectively connected to two ends of a strain sensing optical fiber, the interface c is connected to one end of a temperature sensing optical fiber, and the interface d is connected to one end of a loss sensing optical fiber. The output signals of the first photodetector (19), the second photodetector (25), the third photodetector (26) and the Raman detection module (22) are connected to a computer (20) via an acquisition card (21).

2. According to claim 1, a multi-parameter distributed optical fiber sensing device based on chaotic laser is characterized in that: It also includes a bias control board (7) and a second optical splitter (8), wherein the second optical splitter (8) is arranged between the electro-optic modulator (6) and the erbium-doped fiber optical amplifier (9) and is used to split the optical signal output by the electro-optic modulator (6) into two parts, one part is sent to the bias control board (7), and the other part is sent to the erbium-doped fiber optical amplifier (9).

3. The multi-parameter distributed optical fiber sensing device based on chaotic laser according to claim 1, characterized in that: The first optical splitter (4) is a 1×2 polarization-maintaining coupler.

4. The multi-parameter distributed optical fiber sensing device based on chaotic laser according to claim 1, characterized in that: It also includes an attenuator (12) for attenuating the optical signal entering the SOA pulse modulator (14).

5. A multi-parameter distributed optical fiber sensing method based on chaotic laser, characterized in that: A multi-parameter distributed optical fiber sensing device based on chaotic laser according to claim 1 is implemented, including: temperature detection, strain detection and loss detection; The steps of strain detection are: S101, controlling the first optical switch (3) to allow the chaotic laser emitted by the photon integrated chaotic laser (1) to pass through, and controlling the second optical switch (16) to allow the first output end thereof to output an optical signal; and collecting the Brillouin signal containing strain information detected by the first photodetector (19) through the acquisition card (21); S102, using a computer (20) to analyze and process the Brillouin signal to obtain a strain change at a certain point of the detection optical fiber, and finally obtain a stress distribution along the optical fiber; The steps of temperature detection are: S201, Calibration stage: S2011, setting the temperature of the temperature sensing optical fiber to T0; S2012, controlling the first optical switch (3) to allow the chaotic laser emitted by the photon integrated chaotic laser (1) to pass through, and controlling the second optical switch (16) to allow the second output end of the optical switch to output an optical signal; then modulating the chaotic laser into a chaotic pulse laser with a pulse width of W through the SOA pulse modulator (14); and collecting the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module (22) through the acquisition card (21); S2013, controlling the first optical switch (3) to allow the laser light emitted by the narrow linewidth laser (2) to pass through, and controlling the second optical switch (16) to allow the second output end of the optical switch to output an optical signal; then modulating the optical signal into a chaotic pulse laser light with a pulse width of W+△ through the SOA pulse modulator (14); collecting the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity along the temperature sensing optical fiber detected by the Raman detection module (22) through the acquisition card (21); △ represents the pulse width difference; S2014, calculating and obtaining a calibrated anti-Stokes signal intensity difference and a calibrated Stokes signal intensity difference along the temperature sensing optical fiber; S202, measurement phase: S2021, repeat the operation of step S2012 to obtain a first measured anti-Stokes signal strength and a first measured Stokes signal strength along the temperature sensing optical fiber; S2022, repeating the operation of step S2013 to obtain a second measured anti-Stokes signal strength and a second measured Stokes signal strength along the temperature sensing optical fiber; S2023, calculating and obtaining a measured anti-Stokes signal strength difference and a measured Stokes signal strength difference; S203, calculating the temperature along the temperature sensing optical fiber, the calculation formula is: ； in, is the Raman frequency shift, h is the Planck constant, and k is the Boltzmann constant; and represents the difference in the intensity of the anti-Stokes signal and the difference in the intensity of the Stokes signal at the position of the temperature sensing optical fiber L; and represents the difference in the intensity of the calibrated anti-Stokes signal and the difference in the intensity of the calibrated Stokes signal at the position of the temperature sensing optical fiber L; The steps of loss detection are: S301, controlling the first optical switch (3) to allow the chaotic laser emitted by the photon integrated chaotic laser (1) to pass through, and controlling the second optical switch (16) to allow the third output end thereof to output an optical signal; and collecting, through the acquisition card (21), the chaotic reference pulse signal and the Rayleigh scattering signal detected respectively by the second photodetector (25) and the third photodetector (26); S302, using a computer (20) to calculate and obtain loss variation information along the loss sensing optical fiber.

6. The multi-parameter distributed optical fiber sensing method based on chaotic laser according to claim 5 is characterized in that: In step S2014, the calculation formula of the calibrated anti-Stokes signal strength difference and the calibrated Stokes signal strength difference along the temperature sensing optical fiber is: ； ； in, and represents the first calibrated anti-Stokes signal intensity and the first calibrated Stokes signal intensity at the position of the temperature sensing optical fiber L; and represents the second calibrated anti-Stokes signal intensity and the second calibrated Stokes signal intensity at the position of the temperature sensing optical fiber L; In step S2023, the calculation formula for the measured anti-Stokes signal strength difference and the measured Stokes signal strength difference along the temperature sensing optical fiber is: ； ； in, and represent the first measured anti-Stokes signal intensity and the first measured Stokes signal intensity at the position of the temperature sensing optical fiber L, respectively; and They respectively represent the second measured anti-Stokes signal intensity and the second measured Stokes signal intensity at the position of the temperature sensing optical fiber L.

7. The multi-parameter distributed optical fiber sensing method based on chaotic laser according to claim 5 is characterized in that: The value of △ is 0.1ns.

8. The multi-parameter distributed optical fiber sensing method based on chaotic laser according to claim 5 is characterized in that: In step S302, the method for calculating the loss change information along the loss sensing optical fiber is: The chaotic pulse reference signal and the Rayleigh scattering signal are cross-correlated to obtain the cross-correlation coefficient, which is calculated as follows: ； in, Indicates loss sensing fiber l The mutual correlation coefficient, N represents the time length of the received Rayleigh scattering signal and the chaotic pulse reference signal, Z ( l，t ) represents the loss of the sensing fiber at time t l The intensity of Rayleigh scattered light generated at X(t) represents the chaotic pulse reference signal strength at time t; Then, the loss factor is obtained from the slope of the cross-correlation coefficient.

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