CN112577627A - Distributed optical fiber temperature measurement system and temperature measurement method - Google Patents
Distributed optical fiber temperature measurement system and temperature measurement method Download PDFInfo
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- CN112577627A CN112577627A CN202011397812.6A CN202011397812A CN112577627A CN 112577627 A CN112577627 A CN 112577627A CN 202011397812 A CN202011397812 A CN 202011397812A CN 112577627 A CN112577627 A CN 112577627A
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- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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Abstract
The invention discloses a distributed optical fiber temperature measurement system and a temperature measurement method, which relate to the field of optical fiber sensing and comprise an excitation light source, a test light source, a wavelength division multiplexer, a control and signal processing circuit and a temperature measurement optical cable, wherein the control and signal processing circuit is electrically connected with the excitation light source and the test light source; the emergent end of the excitation light source is connected with a wavelength division multiplexer, and the wave combining end of the wavelength division multiplexer is connected with a temperature measuring optical cable; the light outlet end of each test light source is connected with an optical attenuator, the other end of each optical attenuator is connected with a first port of a circulator, a second port of each circulator is connected with the wavelength division multiplexer, a third port of each circulator is correspondingly connected with an optical detector, and the control and signal processing circuit is electrically connected with the output end of each optical detector. The invention adopts an on-line measurement mode of Raman scattering light propagation loss, and realizes high applicability and flexibility of the distributed optical fiber temperature measurement system to various optical cables and high-precision measurement of distributed temperature; simple structure, the integrated level is high, has engineering practical value.
Description
Technical Field
The invention relates to the field of optical fiber sensing, in particular to a distributed optical fiber temperature measurement system and a temperature measurement method.
Background
The distributed optical fiber temperature sensing technology mainly utilizes the correlation between the intensity of Raman scattering optical signals in the optical nonlinear effect and the temperature, and the measurement of the temperature of different positions of the optical fiber is realized by detecting and analyzing the Raman scattering optical signals generated by excitation of different positions of the optical fiber. The optical fiber in the distributed optical fiber temperature sensing technology is a sensor and an information transmission medium, and the technology has the characteristics of flexible sensor structure, continuous distribution, long monitoring distance, high working temperature and the like, so the technology has wide application prospect in the fields of fire fighting, fire early warning, oil well surveying and the like.
The distributed optical fiber temperature sensing technology is an intensity detection type temperature sensing technology, transmission loss of temperature measurement Stokes Raman scattering light and anti-Stokes Raman scattering light at each position point in sensing optical fibers is an important factor influencing the accuracy of distributed optical fiber temperature measurement, so that the fact that the transmission loss parameters of the temperature measurement Raman scattering light in a sensing optical cable are accurately obtained is an important ring of distributed optical fiber temperature measurement, and temperature measurement deviation can be generated when a distributed optical fiber temperature measurement system is applied to the sensing optical cable with unknown transmission loss information. Moreover, the propagation loss coefficient of the sensing optical cable can also change under the action of an external environment, for example, the sensing optical cable is deformed by the optical fiber structure when being subjected to mechanical action such as squeezing, pressing, pulling, twisting and the like, which causes the change of the propagation loss of the optical signal passing through the position point, and due to the dispersion effect of optical fiber propagation, the propagation loss of each component of the temperature-measuring raman scattering light optical signal when propagating at the position point will be different, thereby causing the reduction of the temperature-measuring precision of the distributed optical fiber. Therefore, how to quickly and accurately obtain the actual propagation loss parameters of the components of the temperature-measuring Raman scattering light in the sensing optical cable, the applicability of the temperature-measuring system to various optical cables is improved, and the high-precision temperature measurement has important significance and application value.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a distributed optical fiber temperature measurement system and a temperature measurement method, solves the problem of temperature measurement deviation caused by inaccurate acquisition of temperature measurement Raman scattering light propagation loss parameters in a sensing optical cable, improves the high applicability and flexibility of the distributed optical fiber temperature measurement system to various optical cables, and realizes high-precision temperature measurement of the distributed optical fiber temperature measurement system.
The purpose of the invention is achieved by the following technical scheme: the distributed optical fiber temperature measurement system comprises an excitation light source, at least two test light sources, a wavelength division multiplexer, a control and signal processing circuit and a temperature measurement optical cable, wherein the control and signal processing circuit is respectively electrically connected with the excitation light source and each test light source and is used for outputting a pulse modulation signal to generate pulse excitation light; the working wavelength of the wavelength division multiplexer corresponds to the wavelengths of the excitation light source and the test light sources, the emergent end of the excitation light source is connected with a port of the wavelength division multiplexer with the same working wavelength, and the wave combining end of the wavelength division multiplexer is connected with a temperature measuring optical cable; the light outlet end of each test light source is correspondingly connected with an optical attenuator, the other end of each optical attenuator is correspondingly connected with a first port of a circulator, a second port of each circulator is connected with a working port, which is arranged on the wavelength division multiplexer and has the same wavelength as the corresponding test light source, a third port of each circulator is correspondingly connected with an optical detector, and the control and signal processing circuit is electrically connected with the output end of each optical detector, so that Raman scattering light signals and Rayleigh scattering light signals output by each optical detector are synchronously collected.
As a preferred technical scheme, the number of the test light sources is two, namely a test light source A and a test light source B, and the excitation light source is a pulse laser with the wavelength of 1064nm or 1550 nm; according to the optical wavelength of the excitation light source, the wavelengths selected by the test light source A and the test light source B are respectively 850nm and 1300nm or 1450nm and 1660nm, and the working wavelengths selected by the wavelength division multiplexer are respectively 850nm/1064nm/1300nm or 1450nm/1550nm/1660 nm.
A distributed optical fiber temperature measurement method comprises the following steps:
1) connecting an excitation light source with a port with the same working wavelength in the wavelength division multiplexer; connecting the optical output end of a test light source A with the input end of an optical attenuator A, connecting the output end of the optical attenuator A with a first port of a circulator A, connecting a second port of the circulator A with a port, which is in the wavelength division multiplexer and is the same as that of the test light source A, and connecting a third port of the circulator A with the optical input end of an optical detector A; connecting the optical output end of a test light source B with the input end of an optical attenuator B, connecting the output end of the optical attenuator B with a first port of a circulator B, connecting a second port of the circulator B with a port in a wavelength division multiplexer, which has the same wavelength as the test light source B, and connecting a third port of the circulator B with the optical input end of an optical detector B; connecting the wave combining end of the wavelength division multiplexer with a temperature measuring optical cable; the output ends of the optical detector A and the optical detector B are respectively and electrically connected with a control and signal processing circuit;
2) the pulse modulation signal is output to the excitation light source through the control and signal processing circuit to realize the generation of pulse excitation light, and Raman scattering optical signals output by the optical detector A and the optical detector B are synchronously collected;
3) the pulse modulation signals are output to the test light source A and the test light source B through the control and signal processing circuit to realize the generation of pulse excitation light, and Rayleigh scattering light signals output by the detector A and the optical detector B are synchronously collected;
4) the control and signal processing circuit collects and accumulates the collected Raman scattering optical signals and Rayleigh scattering optical signals for multiple times to obtain the relative strength information of the temperature measuring optical cable at different positions and relative to the temperature;
5) and the control and signal processing circuit completes the calculation of the temperature in an interpolation and fitting mode according to the relative intensity calibration data at different temperatures to the obtained relative intensity result.
As a preferred technical scheme, the excitation light source is a high-speed pulse laser with the wavelength of 1064nm or 1550 nm; according to the wavelength of the excitation light source, the working wavelengths of the test light source and the wavelength division multiplexer are correspondingly selected; when the excitation light source wavelength is 1064nm, the wavelengths of the test light source A and the test light source B are 850nm and 1300nm respectively, and the working wavelength selected by the wavelength division multiplexer is 850nm/1064nm/1300 nm; when the wavelength of the excitation light source is 1550nm, the wavelengths of the test light source A and the test light source B are 1450nm and 1660nm respectively, and the working wavelength selected by the wavelength division multiplexer is 1450nm/1550nm/1660 nm.
As a preferred technical solution, the photo detector a and the photo detector B are avalanche diodes.
As a preferred technical scheme, the control and signal processing circuit modulates the excitation light source, the test light source a and the test light source B and controls the detection and acquisition of corresponding signals by adopting an alternate working mode.
Preferably, in step 4), a processing method of performing a square root operation on the accumulated and averaged rayleigh scattered light signal, comparing the raman scattered light with rayleigh scattered light of a corresponding wavelength, and comparing the anti-stokes raman light signal with the stokes raman scattered light signal is performed.
The invention has the beneficial effects that:
1. the on-line measurement mode of the Raman scattering light propagation loss is adopted, so that the high applicability and flexibility of the distributed optical fiber temperature measurement system to various optical cables and the high-precision measurement of distributed temperature are realized;
2. simple structure, the integrated level is high, has engineering practical value.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Description of reference numerals: the device comprises an excitation light source 1, a test light source A2, a test light source B3, a light detector A4, a light detector B5, a light attenuator A6, a light attenuator B7, a circulator A8, a circulator B9, a wavelength division multiplexer 10, a control and signal processing circuit 11 and a temperature measurement optical cable 12.
Detailed Description
The invention will be described in detail below with reference to the following drawings:
example (b): as shown in fig. 1, taking two test light sources as an example, a distributed optical fiber temperature measurement system includes an excitation light source 1, a test light source a2, a test light source B3, a light detector a4, a light detector B5, an optical attenuator a6, an optical attenuator B7, a circulator A8, a circulator B9, a wavelength division multiplexer 10, a control and signal processing circuit 11, and a temperature measurement optical cable 12. The control and signal processing circuit 11 is electrically connected to the excitation light source 1, the test light source a2, and the test light source B3, respectively, and is configured to output a pulse modulation signal to generate pulsed excitation light. The working wavelength of the wavelength division multiplexer 10 corresponds to the wavelengths of the excitation light source 1, the test light source a2 and the test light source B3, the emergent end of the excitation light source 1 is connected with the port of the wavelength division multiplexer 10 with the same working wavelength, and the wave combining end of the wavelength division multiplexer 10 is connected with the temperature measuring optical cable 12. The light outlet end of the test light source A2 is correspondingly connected with the optical attenuator A6, and the light outlet end of the test light source B3 is correspondingly connected with the optical attenuator B7; the other end of the optical attenuator A6 is correspondingly connected with a first port of the circulator A8, and the other end of the optical attenuator B7 is correspondingly connected with a first port of the circulator B9; a second port of the circulator A8 is connected with a working port on the wavelength division multiplexer 10, which has the same wavelength as the test light source A2, and a second port of the circulator B9 is connected with a working port on the wavelength division multiplexer 10, which has the same wavelength as the test light source B3; the third port of the circulator A8 is correspondingly connected with the photodetector A4, and the third port of the circulator B9 is correspondingly connected with the photodetector B5. The control and signal processing circuit 11 is electrically connected with the output ends of the light detector a4 and the light detector B5, so as to synchronously collect raman scattering light signals and rayleigh scattering light signals output by the light detector a4 and the light detector B5.
Preferably, the excitation light source 1 is a pulse laser with a wavelength of 1064nm or 1550 nm; the wavelengths selected by the test light source A2 and the test light source B3 are 850nm and 1300nm or 1450nm and 1660nm respectively; correspondingly, the wavelength division multiplexer 10 selects the working wavelength of 850nm/1064nm/1300nm or 1450nm/1550nm/1660 nm.
A distributed optical fiber temperature measurement method comprises the following steps:
1) connecting an excitation light source 1 with a port with the same working wavelength in a wavelength division multiplexer 10; the optical output end of a test light source A2 is connected with the input end of an optical attenuator A6, the output end of an optical attenuator A6 is connected with a first port of a circulator A8, a second port of the circulator A8 is connected with a port, in the wavelength division multiplexer 10, of the same wavelength as that of the test light source A2, and a third port of a circulator A8 is connected with the optical input end of a light detector A4; the optical output end of a test light source B3 is connected with the input end of an optical attenuator B7, the output end of an optical attenuator B7 is connected with a first port of a circulator B9, a second port of the circulator B9 is connected with a port, in the wavelength division multiplexer 10, of the same wavelength as that of the test light source B3, and a third port of a circulator B9 is connected with the optical input end of a light detector B5; connecting the wave combining end of the wavelength division multiplexer 10 with a temperature measuring optical cable 12; the output ends of the light detector A4 and the light detector B5 are respectively and electrically connected with the control and signal processing circuit 11;
2) the pulse modulation signal is output to the excitation light source 1 through the control and signal processing circuit 11 to realize the generation of pulse excitation light, and the Raman scattering optical signals output by the optical detector A4 and the optical detector B5 are synchronously collected;
3) the pulse modulation signals are output to the test light source A2 and the test light source B3 through the control and signal processing circuit 11 to realize the generation of pulse excitation light, and Rayleigh scattered light signals output by the detector A4 and the light detector B5 are synchronously collected;
4) the control and signal processing circuit 11 adopts a processing method of collecting and accumulating the collected raman scattering light signals and rayleigh scattering light signals for multiple times, performing square root operation on the rayleigh scattering light signals after accumulating the average, comparing the raman scattering light with corresponding wavelength rayleigh scattering light, and comparing the anti-stokes raman light signals with stokes raman scattering light signals, thereby obtaining relative intensity information related to temperature at different positions of the temperature measuring optical cable 12;
5) the control and signal processing circuit 11 completes the calculation of the temperature by means of interpolation and fitting according to the relative intensity calibration data at different temperatures to the obtained relative intensity result.
Preferably, the excitation light source 1 is a high-speed pulse laser with a wavelength of 1064nm or 1550 nm; according to the wavelength of the excitation light source 1, the working wavelengths of the test light source and the wavelength division multiplexer 10 are correspondingly selected; when the wavelength of the excitation light source 1 is 1064nm, the wavelengths of the test light source A2 and the test light source B3 are 850nm and 1300nm respectively, and the working wavelength selected by the wavelength division multiplexer 10 is 850nm/1064nm/1300 nm; when the wavelength of the excitation light source 1 is 1550nm, the wavelengths of the test light source A2 and the test light source B3 are 1450nm and 1660nm respectively, and the working wavelength selected by the wavelength division multiplexer 10 is 1450nm/1550nm/1660 nm. The light detector A4 and the light detector B5 adopt high-bandwidth avalanche diodes; the control and signal processing circuit 11 alternately works the modulation of the excitation light source 1, the test light source a2 and the test light source B3 and the control of the corresponding signal detection acquisition.
The working process of the invention is as follows: the test light source is driven by the control and signal processing circuit to generate pulse laser for exciting Rayleigh scattering light of the temperature measuring optical cable; the two optical attenuators are used for adjusting the optical power input from the test light source to the temperature measuring optical cable, so that the Rayleigh scattered light power returned by the temperature measuring optical cable meets the input requirement of the optical detector; the circulator and the wavelength division multiplexer guide the light signals with different wavelengths emitted by the excitation light source and the test light source to the temperature measuring optical cable, distinguish different wavelength components in the light signals returned by the temperature measuring optical cable and respectively introduce the light signals into the optical detector; the optical detector converts Raman scattering optical signals generated by excitation of the excitation light source and Rayleigh scattering optical signals generated by excitation of the test light source into electric signals; the control and signal processing circuit is used for controlling the generation of signals, the acquisition of detection signals and the processing and operation of data.
It should be understood that equivalent substitutions and changes to the technical solution and the inventive concept of the present invention should be made by those skilled in the art to the protection scope of the appended claims.
Claims (7)
1. A distributed optical fiber temperature measurement system is characterized in that: the device comprises an excitation light source (1), at least two test light sources, a wavelength division multiplexer (10), a control and signal processing circuit (11) and a temperature measuring optical cable (12), wherein the control and signal processing circuit (11) is respectively and electrically connected with the excitation light source (1) and each test light source and is used for outputting pulse modulation signals to generate pulse excitation light; the working wavelength of the wavelength division multiplexer (10) corresponds to the wavelengths of the excitation light source (1) and the test light sources, the emergent end of the excitation light source (1) is connected with a port with the same working wavelength of the wavelength division multiplexer (10), and the wave combining end of the wavelength division multiplexer (10) is connected with a temperature measuring optical cable (12); the light outlet end of each test light source is correspondingly connected with an optical attenuator, the other end of each optical attenuator is correspondingly connected with a first port of a circulator, a second port of each circulator is connected with a working port, with the same wavelength as the corresponding test light source, on the wavelength division multiplexer (10), a third port of each circulator is correspondingly connected with an optical detector, and a control and signal processing circuit (11) is electrically connected with the output end of each optical detector, so that Raman scattering light signals and Rayleigh scattering light signals output by each optical detector are synchronously collected.
2. The distributed optical fiber temperature measurement system of claim 1, wherein: the two test light sources are respectively a test light source A (2) and a test light source B (3), and the excitation light source (1) is a pulse laser with the wavelength of 1064nm or 1550 nm; according to the optical wavelength of the excitation light source (1), the wavelengths selected by the test light source A (2) and the test light source B (3) are respectively 850nm and 1300nm or 1450nm and 1660nm, and the working wavelengths selected by the wavelength division multiplexer (10) are respectively 850nm/1064nm/1300nm or 1450nm/1550nm/1660 nm.
3. A distributed optical fiber temperature measurement method is characterized in that: the method comprises the following steps:
1) connecting an excitation light source (1) with ports with the same working wavelength in a wavelength division multiplexer (10); the optical output end of a test light source A (2) is connected with the input end of an optical attenuator A (6), the output end of the optical attenuator A (6) is connected with a first port of a circulator A (8), a second port of the circulator A (8) is connected with a port, which is in the wavelength same with that of the test light source A (2), in a wavelength division multiplexer (10), and a third port of the circulator A (8) is connected with the optical input end of an optical detector A (4); the optical output end of a test light source B (3) is connected with the input end of an optical attenuator B (7), the output end of the optical attenuator B (7) is connected with a first port of a circulator B (9), a second port of the circulator B (9) is connected with a port, which is in the wavelength same with that of the test light source B (3), in a wavelength division multiplexer (10), and a third port of the circulator B (9) is connected with the optical input end of an optical detector B (5); connecting the wave combining end of the wavelength division multiplexer (10) with a temperature measuring optical cable (12); the output ends of the optical detector A (4) and the optical detector B (5) are respectively and electrically connected with a control and signal processing circuit (11);
2) the pulse modulation signal is output to the excitation light source (1) through the control and signal processing circuit (11) to realize the generation of pulse excitation light, and Raman scattering optical signals output by the optical detector A (4) and the optical detector B (5) are synchronously collected;
3) the pulse modulation signals are output to a test light source A (2) and a test light source B (3) through a control and signal processing circuit (11) to realize the generation of pulse excitation light, and Rayleigh scattering light signals output by a detector A (4) and a light detector B (5) are synchronously collected;
4) the control and signal processing circuit (11) collects and accumulates the collected Raman scattering light signals and Rayleigh scattering light signals for multiple times to obtain the relative strength information related to the temperature at different positions of the temperature measuring optical cable (12);
5) the control and signal processing circuit (11) completes the calculation of the temperature by means of interpolation and fitting according to the relative intensity calibration data at different temperatures to the obtained relative intensity result.
4. The distributed optical fiber temperature measurement method according to claim 3, wherein: the excitation light source (1) is a high-speed pulse laser with the wavelength of 1064nm or 1550 nm; according to the wavelength of the excitation light source (1), the working wavelengths of the test light source and the wavelength division multiplexer (10) are correspondingly selected; when the wavelength of the excitation light source (1) is 1064nm, the wavelengths of the test light source A (2) and the test light source B (3) are 850nm and 1300nm respectively, and the working wavelength selected by the wavelength division multiplexer (10) is 850nm/1064nm/1300 nm; when the wavelength of the excitation light source (1) selects 1550nm, the wavelengths of the test light source A (2) and the test light source B (3) are 1450nm and 1660nm respectively, and the working wavelength selected by the wavelength division multiplexer (10) is 1450nm/1550nm/1660 nm.
5. The distributed optical fiber temperature measurement method according to claim 3, wherein: the light detector A (4) and the light detector B (5) adopt avalanche diodes.
6. The distributed optical fiber temperature measurement method according to claim 3, wherein: the control and signal processing circuit (11) adopts an alternate working mode for modulating the excitation light source (1), the test light source A (2) and the test light source B (3) and controlling the detection and acquisition of corresponding signals.
7. The distributed optical fiber temperature measurement method according to claim 3, wherein: and 4) in step 4), performing a square root operation on the Rayleigh scattered light signals subjected to the accumulation averaging, comparing the Raman scattered light with Rayleigh scattered light with corresponding wavelength, and comparing the anti-Stokes Raman light signals with the Stokes Raman scattered light signals.
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