CN113686366B - Optical frequency domain reflectometer device based on Fourier domain mode locking and measuring method - Google Patents
Optical frequency domain reflectometer device based on Fourier domain mode locking and measuring method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
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- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
Abstract
The invention provides an optical frequency domain reflectometer device and a measuring method based on Fourier domain mode locking, and belongs to the field of optical frequency domain reflectometers. The problems that the existing optical frequency domain reflectometer device and method are limited by low tuning speed, small tuning range and polarization sensitivity of a tuning light source are solved. The Fourier domain mode locking tuning light source is connected with an auxiliary interferometer, a biaxial working polarization splitting prism and a polarization maintaining optical amplifier after sequentially passing through a second optical isolator and a second polarization maintaining optical fiber coupler, the auxiliary interferometer is connected with a signal processing module, the biaxial working polarization splitting prism is connected with a fourth polarization maintaining optical fiber coupler and a fifth polarization maintaining optical fiber coupler respectively, and the polarization maintaining optical amplifier and a second delay line are connected with the fourth polarization maintaining optical fiber coupler and the fifth polarization maintaining optical fiber coupler respectively after sequentially passing through the polarization maintaining circulator and the uniaxial working polarization splitting prism. It is mainly used for optical frequency domain reflectometer.
Description
Technical Field
The invention belongs to the field of optical frequency domain reflectometers, and particularly relates to an optical frequency domain reflectometer device and a measuring method based on Fourier domain mode locking.
Background
In recent years, as the role of the intelligent flexible structure in the fields of aerospace, smart cities, smart medical treatment and the like is deepened, how to perform operations such as structural health monitoring and adaptive control on the intelligent flexible structure has become one of the problems to be solved. In this respect, the optical fiber sensor with the characteristics of flexibility, light weight, electromagnetic shielding and the like has good compatibility with the intelligent flexible structure; furthermore, the optical fiber itself can serve as a good medium for optical signal transmission, which enables the fiber optic sensor to make distributed measurements of stress/strain conditions in the smart flexible structure.
The existing distributed optical fiber measuring device and method mainly comprise an optical time domain reflection meter and an optical frequency domain reflectometer. The method is mainly limited in that the pulse width of the pulse reference beam cannot be infinitely narrowed, the spatial resolution is usually tens of centimeters or even a plurality of meters, and the measurement requirement of an intelligent flexible structure cannot be met. The optical frequency domain reflectometer measures with a continuous reference beam whose center wavelength is tunable and locates by calculating the back scattered beam from the continuous reference beam and the beat frequency between the continuous reference beam. The optical frequency domain reflectometer replaces the requirement of the optical time domain reflectometer for the pulsed reference beam by specifying a tuning curve between the time domain and the frequency domain, the spatial resolution of which is mainly dependent on the tuning range and the tuning accuracy of the pump beam/reference beam, and is expected to reach the millimeter order. It can be seen that the key to the ability of an optical frequency domain reflectometer to operate quickly, with high spatial resolution, and with high accuracy is to achieve large-scale, high-accuracy pump book/reference beam tuning.
However, the external cavity laser tuning technology ECL, the vertical cavity surface emitting laser tuning technology VCSEL, the distributed bragg reflection laser tuning technology DBR and the like adopted in the conventional optical frequency domain reflectometer device and method are used for realizing the tuning of the pump beam by repeatedly starting/stopping vibrating different laser longitudinal modes, so that the introduced time delay and phase noise restrict the improvement of the tuning speed and the tuning precision of the pump light source. In addition, when the interference method is used to demodulate the measurement signal of the optical frequency domain reflectometer apparatus and method, the deviation of the polarization state between the reference beam and the measurement beam will also result in a decrease in the accuracy of the measurement result.
Disclosure of Invention
The invention provides an optical frequency domain reflectometer device and a measuring method based on Fourier domain mode locking in order to solve the problems in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme: the Fourier domain mode locking-based optical frequency domain reflectometer device comprises a Fourier domain mode locking tuning light source, a second optical isolator, a second polarization maintaining optical fiber coupler, an auxiliary interferometer, a dual-axis working polarization splitting prism, a fourth polarization maintaining optical fiber coupler, a first balanced detector, a signal processing module, a second balanced detector, a fifth polarization maintaining optical fiber coupler, a single-axis working polarization splitting prism, a polarization maintaining circulator, a second delay line and a polarization maintaining amplifier, wherein the Fourier domain mode locking tuning light source sequentially passes through the second optical isolator and the second polarization maintaining optical fiber coupler and then is respectively connected with the auxiliary interferometer, the dual-axis working polarization splitting prism and the polarization maintaining optical fiber amplifier, the auxiliary interferometer is connected with the signal processing module, the dual-axis working polarization splitting prism is respectively connected with the fourth polarization maintaining optical fiber coupler and the fifth polarization maintaining optical fiber coupler, the fourth delay line sequentially passes through the polarization maintaining circulator and the single-axis working polarization splitting prism and then is respectively connected with the fourth polarization maintaining optical fiber coupler and the fifth polarization maintaining optical fiber coupler, and the fourth delay line is connected with the first polarization maintaining optical fiber coupler and the second polarization maintaining optical fiber coupler to form a signal processing channel.
Further, the fourier domain mode-locked tuning light source comprises an optical amplifier, a tunable optical filter, a polarization dispersion management delay line, a first optical isolator, a first polarization maintaining optical fiber coupler and a narrow linewidth optical filter which are sequentially connected, wherein the tunable optical filter is connected with the function generator, and the narrow linewidth optical filter is connected with the second optical isolator.
Further, the transmission and polarization characteristics of the polarization dispersion management delay line are adjustable.
Furthermore, the polarization dispersion management delay line regulates and controls transmission and polarization characteristics by writing chirped gratings, serial dispersion shift optical fibers, dispersion compensation optical fibers, glass slides, optical fiber cones or polarization controllers.
Still further, auxiliary interferometer includes third polarization maintaining optical fiber coupler, first time delay line, photoelectric detector, first Faraday speculum and second Faraday speculum, second polarization maintaining optical fiber coupler links to each other with third polarization maintaining optical fiber coupler, third polarization maintaining optical fiber coupler links to each other with photoelectric detector, first Faraday speculum and second Faraday speculum respectively, be provided with first time delay line between third polarization maintaining optical fiber coupler and the first Faraday speculum, photoelectric detector links to each other with signal processing module.
The invention also provides a measuring method of the optical frequency domain reflectometer device based on Fourier domain mode locking, which comprises the following steps:
step 1: the second optical isolator and the second polarization maintaining fiber coupler are divided into a trigger beam T, a reference beam R and a pumping beam P, and the three beams respectively flow into an auxiliary interferometer, a biaxial working polarization beam splitter prism and a polarization maintaining amplifier;
step 2: the triggering light beam T enters a signal processing module after being processed by an auxiliary interferometer and is used as a triggering signal of the signal processing module;
step 3: the reference beam R is divided into a slow axis alignment reference beam R1 and a fast axis alignment reference beam R2 with equal amplitude by a biaxial working polarization beam splitter prism;
step 4: the pump beam P flows into the second delay line through the 1 port and the 2 port of the polarization-preserving circulator, and the pump beam P and the second delay line generate a measuring beam S through Rayleigh scattering interaction;
step 5: the measuring beam S is divided into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a single-axis working polarization beam splitter prism;
step 6: the slow axis alignment reference beam R1 and the slow axis alignment measuring beam S1 are converted into a slow axis interference signal A by a first balance detector after beam combination and interference of a fourth polarization maintaining fiber coupler, and the slow axis interference signal A is input into a signal processing module;
step 7: the fast axis alignment reference beam R2 and the fast axis alignment measuring beam S2 are converted into a fast axis interference signal B by a second balance detector after beam combination and interference of a fifth polarization maintaining fiber coupler, and the fast axis interference signal B is input into a signal processing module;
step 8: and the signal processing module integrates the slow axis interference signal A and the fast axis interference signal B to obtain stress/strain information to be detected.
Further, the measuring beam S in the step 5 is an arbitrarily polarized beam, whereinPolarization mode and->The polarization mode is split into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a uniaxial working polarization beam splitter prism.
Further, the signal processing method of the signal processing module in the step 8 includes the following steps:
step 8.1: the signal processing module records the I A I in a single wavelength tuning period by calculating the square sum of the slow axis interference signal A and the fast axis interference signal B 2 +|B| 2 Trend over time;
step 8.2: using fast fourier transforms for |a| within a single wavelength tuning period 2 +|B| 2 The trend of change with time is processed to obtain |A| 2 +|B| 2 Distribution of different beat frequency components;
step 8.3: the sensing positions in the second delay line are combined with |A|| 2 +|B| 2 The beat frequency components in the filter are in one-to-one correspondence through the pair of |A| 2 +|B| 2 The beat frequency component in the second delay line is subjected to local inverse fast Fourier transform to access each sensing position in the second delay line, and stress/strain information of the sensing position is obtained by performing cross correlation operation on the local inverse fast Fourier transform result when stress/strain exists or not.
Further, when continuous, repetitive spectral analysis is desired, the output waveform of the function generator is arranged in a zigzag pattern.
Compared with the prior art, the invention has the beneficial effects that: the invention solves the problems that the existing optical frequency domain reflectometer device and method are limited by low tuning speed and small tuning range of a tuning light source and have polarization sensitivity, so that the measurement speed, the spatial resolution and the measurement precision are difficult to improve.
The invention suppresses material dispersion and polarization mode dispersion among longitudinal mode modes in the Fourier domain mode-locked tuning light source by regulating and controlling the transmission and polarization characteristics of the polarization dispersion management delay line, and can control the reference beam, the pumping beam and the triggering beam to be linear polarization beams; the tuning period of the function generator is matched with the single-pass transition time of each longitudinal mode in the Fourier domain mode locking tuning light source, so that each longitudinal mode can be stably evolved in the Fourier domain mode locking tuning light source; the longitudinal mode modes are controlled to be sequentially output according to the wavelength sequence by a tunable optical filter. The invention avoids the repeated starting and stopping vibration of the reference beam, the pumping beam and the triggering beam in the measuring process in the prior optical frequency domain reflectometer device and method, and can realize large-scale, rapid and stable tuning of the reference beam, the pumping beam and the triggering beam, thereby improving the measuring speed and the spatial resolution of the optical frequency domain reflectometer.
The invention divides the linear polarized reference beam into a slow axis alignment reference beam and a fast axis alignment reference beam with equal amplitude through a biaxial working polarization beam splitter prism; the measuring beam is divided into a plurality of measuring beams by a single-axis working polarization beam splitter prismPolarization mode and->The polarization mode is divided into a slow axis alignment measuring beam and a fast axis alignment measuring beam; the first balance detector and the second balance detector are used for respectively and independently detecting the slow axis interference signal and the fast axis interference signal, so that the optical frequency domain reflectometer device and the optical frequency domain reflectometer method can be prevented from being +.>Polarization mode and->And the influence of polarization mode crosstalk is further improved, so that the measurement accuracy of the optical frequency domain reflectometer is improved.
Drawings
FIG. 1 is a schematic diagram of an optical frequency domain reflectometer device based on Fourier domain mode locking according to the present invention;
FIG. 2 is a schematic view of a dual axis working polarizing beamsplitter according to the present invention;
FIG. 3 is a schematic view of a single axis polarizing beamsplitter according to the present invention;
FIG. 4 is a schematic diagram of a signal processing method according to the present invention;
fig. 5 is a schematic diagram of an output waveform of a function generator according to the present invention.
1-Fourier domain mode-locked tuning light source, 101-optical amplifier, 102-tunable optical filter, 103-function generator, 104-polarization dispersion management delay line, 105-first optical isolator, 106-first polarization maintaining fiber coupler, 107-narrow linewidth optical filter, 2-second optical isolator, 3-second polarization maintaining fiber coupler, 4-auxiliary interferometer, 401-third polarization maintaining fiber coupler, 402-first delay line, 403-photodetector, 404-first Faraday mirror, 405-second Faraday mirror, 5-dual-axis working polarization splitting prism, and the system comprises a 6-fourth polarization maintaining fiber coupler, a 7-first balance detector, an 8-signal processing module, a 9-second balance detector, a 10-fifth polarization maintaining fiber coupler, an 11-single-axis working polarization splitting prism, a 12-polarization maintaining circulator, a 13-second delay line, a 14-polarization maintaining amplifier, an R-reference beam, an R1-slow axis alignment reference beam, an R2-fast axis alignment reference beam, an S-measuring beam, an S1-slow axis alignment measuring beam, an S2-fast axis alignment measuring beam, a T-trigger beam, a P-pumping beam, an A-slow axis interference signal and a B-fast axis interference signal.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Referring to fig. 1, the optical frequency domain reflectometer device based on fourier domain mode locking includes a fourier domain mode locking tuning light source 1, a second optical isolator 2, a second polarization maintaining optical coupler 3, an auxiliary interferometer 4, a dual-axis working polarization splitting prism 5, a fourth polarization maintaining optical coupler 6, a first balance detector 7, a signal processing module 8, a second balance detector 9, a fifth polarization maintaining optical coupler 10, a single-axis working polarization splitting prism 11, a polarization maintaining circulator 12, a second delay line 13 and a polarization maintaining amplifier 14, wherein the fourier domain mode locking tuning light source 1 is sequentially connected with the auxiliary interferometer 4, the dual-axis working polarization splitting prism 5 and the polarization maintaining optical amplifier 14 after sequentially passing through the second optical isolator 2 and the second polarization maintaining optical coupler 3, the auxiliary interferometer 4 is connected with the signal processing module 8, the dual-axis working polarization splitting prism 5 is respectively connected with the fourth polarization maintaining optical coupler 6 and the fifth polarization maintaining optical coupler 10, and the second delay line 13 is sequentially connected with the fifth polarization maintaining optical coupler 8 and the fifth polarization maintaining optical coupler 8 after sequentially passing through the second delay line polarization maintaining optical coupler 12 and the first polarization maintaining optical coupler 8 and the fifth polarization maintaining optical coupler 10, and the signal processing module 10 is respectively connected with the fourth polarization maintaining optical coupler 8, and the signal processing module is formed.
The fourier domain mode-locked tuning light source 1 according to this embodiment includes an optical amplifier 101, a tunable optical filter 102, a polarization dispersion management delay line 104, a first optical isolator 105, a first polarization maintaining fiber coupler 106, and a narrow linewidth optical filter 107 which are sequentially connected, the tunable optical filter 102 is connected to a function generator 103, the narrow linewidth optical filter 107 is connected to a second optical isolator 2, the transmission and polarization characteristics of the polarization dispersion management delay line 104 are adjustable, and the polarization dispersion management delay line 104 regulates and controls the transmission and polarization characteristics by writing chirped gratings, serial dispersion displacement fibers, dispersion compensation fibers, glass slides, fiber cones, or polarization controllers, so as to inhibit material dispersion between longitudinal mode modes in the fourier domain mode-locked tuning light source 1, and limit material dispersion between longitudinal mode modesTransmission of polarization modes within fourier domain mode-locked tuned light source 1, suppressingPolarization mode and->Polarization mode dispersion between the polarization modes, and the polarization states of the reference beam R, the pump beam P, and the trigger beam T can be controlled as shown in fig. 2.
The auxiliary interferometer 4 comprises a third polarization maintaining fiber coupler 401, a first delay line 402, a photoelectric detector 403, a first Faraday reflector 404 and a second Faraday reflector 405, the second polarization maintaining fiber coupler 3 is connected with the third polarization maintaining fiber coupler 401, the third polarization maintaining fiber coupler 401 is respectively connected with the photoelectric detector 403, the first Faraday reflector 404 and the second Faraday reflector 405, a first delay line 402 is arranged between the third polarization maintaining fiber coupler 401 and the first Faraday reflector 404, and the photoelectric detector 403 is connected with the signal processing module 8.
The polarization dispersion management delay line 104 has adjustable transmission and polarization characteristics, can inhibit material dispersion and polarization mode dispersion among longitudinal mode modes in the fourier domain mode-locked tuning light source 1, and can control an output light beam of the fourier domain mode-locked tuning light source 1 to be a linear polarization light beam; the tuning period of the function generator 103 is matched with the single-pass transit time of each longitudinal mode in the Fourier domain mode-locked tuning light source 1, and each longitudinal mode can be stably evolved in the Fourier domain mode-locked tuning light source 1 by matching the tuning period of the function generator 103 with the single-pass transit time of each longitudinal mode in the Fourier domain mode-locked tuning light source 1; the tunable optical filter 102 controls each longitudinal mode in the fourier domain mode-locked tuned light source 1 to be output sequentially in wavelength order. The tunable optical filter 102 controls each longitudinal mode to be sequentially output according to the wavelength sequence, so that repeated starting and stopping of vibration of the reference beam R, the pump beam P and the trigger beam T in the measuring process in the conventional coherent spectrum analysis device and method are avoided, large-scale, rapid and stable tuning of the reference beam R, the pump beam P and the trigger beam T can be realized, and further the measuring speed and the spatial resolution of the optical frequency domain reflectometer are improved.
The embodiment is a measuring method of an optical frequency domain reflectometer device based on Fourier domain mode locking, which comprises the following steps:
step 1: the second optical isolator 2 and the second polarization maintaining fiber coupler 3 are divided into a trigger beam T, a reference beam R and a pump beam P, and the three beams respectively flow into the auxiliary interferometer 4, the biaxial working polarization beam splitter prism 5 and the polarization maintaining amplifier 14;
step 2: the trigger light beam T enters the signal processing module 8 after being processed by the auxiliary interferometer 4 and is used as a trigger signal of the signal processing module 8;
step 3: the reference beam R is divided into a slow axis alignment reference beam R1 and a fast axis alignment reference beam R2 with equal amplitude by a biaxial working polarization beam splitter prism 5;
step 4: the pump beam P flows into the second delay line 13 through the 1 port and the 2 port of the polarization-preserving circulator 12, and the pump beam P and the second delay line 13 generate a measuring beam S through Rayleigh scattering interaction;
step 5: the measuring beam S is divided into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a single-axis working polarization beam splitter prism 11;
step 6: the slow axis alignment reference beam R1 and the slow axis alignment measuring beam S1 are subjected to beam combination and interference by the fourth polarization maintaining fiber coupler 6, converted into a slow axis interference signal A by the first balance detector 7, and input into the signal processing module 8;
step 7: the fast axis alignment reference beam R2 and the fast axis alignment measuring beam S2 are subjected to beam combination and interference by the fifth polarization maintaining fiber coupler 10, converted into a fast axis interference signal B by the second balance detector 9, and input into the signal processing module 8;
step 8: the signal processing module 8 integrates the slow axis interference signal A and the fast axis interference signal B to obtain stress/strain information to be detected.
In the embodiment, the measuring beam S in the step 5 is an arbitrarily polarized beamPolarization mode and->The polarization mode is split into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a uniaxial working polarization beam splitter prism 11. As shown in fig. 2 and 3, the biaxial working polarizing beam splitter prism 5 splits the linearly polarized reference beam R into a slow axis alignment reference beam R1 and a fast axis alignment reference beam R2 of equal amplitude; the uniaxially working polarizing beam splitter prism 11 splits the measuring beam S +.>Polarization mode and->The polarization mode is divided into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2; the first balanced detector 7 and the second balanced detector 9 detect the slow axis interference signal a and the fast axis interference signal B independently, respectively, which detection method enables to isolate the coherence spectrum analysis device and method from +.>Polarization mode and->And the influence of polarization mode crosstalk is further improved, so that the measurement accuracy of the optical frequency domain reflectometer is improved.
As shown in fig. 4, the signal processing method of the signal processing module 8 in step 8 includes the steps of:
step 8.1: the signal processing module 8 records the I A I in a single wavelength tuning period by calculating the square sum of the slow axis interference signal A and the fast axis interference signal B 2 +|B| 2 Trend over time;
step 8.2: tuning of |A| for a single wavelength period using a Fast Fourier Transform (FFT) 2 +|B| 2 The trend of change with time is processed to obtain |A| 2 +|B| 2 Distribution of different beat frequency components;
step 8.3: the sensing positions in the second delay line 13 are correlated with |A| | 2 +|B| 2 The beat frequency components in the filter are in one-to-one correspondence through the pair of |A| 2 +|B| 2 The beat frequency component in (a) is subjected to local inverse fast fourier transform (local ift) to access each sensing position in the second delay line 13, and the stress/strain information of the sensing position is obtained by performing a cross-correlation operation on the local inverse fast fourier transform (local ift) result when there is stress/strain.
When continuous, repetitive spectral analysis is required, the output waveform of the function generator 103 is arranged in a zigzag shape as shown in fig. 5.
The optical frequency domain reflectometer device and the measuring method based on the Fourier domain mode locking provided by the invention are described in detail, and specific examples are applied to illustrate the principle and the implementation mode of the invention, and the description of the above examples is only used for helping to understand the method and the core idea of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.
Claims (5)
1. An optical frequency domain reflectometer device based on fourier domain mode locking, characterized in that: the device comprises a Fourier domain mode-locking tuning light source (1), a second optical isolator (2), a second polarization maintaining optical fiber coupler (3), an auxiliary interferometer (4), a biaxial working polarization splitting prism (5), a fourth polarization maintaining optical fiber coupler (6), a first balance detector (7), a signal processing module (8), a second balance detector (9), a fifth polarization maintaining optical fiber coupler (10), a uniaxial working polarization splitting prism (11), a polarization maintaining circulator (12), a second delay line (13) and a polarization maintaining amplifier (14), wherein the Fourier domain mode-locking tuning light source (1) is sequentially connected with the auxiliary interferometer (4), the biaxial working polarization splitting prism (5) and the polarization maintaining amplifier (14) after sequentially passing through the second optical isolator (2) and the second polarization maintaining optical fiber coupler (3), the auxiliary interferometer (4) is connected with the signal processing module (8), the biaxial working polarization splitting prism (5) is respectively connected with the fourth polarization maintaining optical fiber coupler (6) and the fifth polarization maintaining optical fiber coupler (10), the second delay line (13) is respectively connected with the fifth polarization maintaining optical fiber coupler (10) after sequentially passing through the second optical isolator (2) and the second polarization maintaining optical fiber coupler (14), the fourth polarization maintaining optical fiber coupler (6) is connected with the first balance detector (7) and the signal processing module (8) to form a passage, the fifth polarization maintaining optical fiber coupler (10) is connected with the second balance detector (9) and the signal processing module (8) to form a passage, the Fourier domain mode-locked tuning light source (1) comprises an optical amplifier (101), a tunable optical filter (102), a polarization dispersion management delay line (104), a first optical isolator (105), a first polarization maintaining optical fiber coupler (106) and a narrow linewidth optical filter (107) which are sequentially connected, the tunable optical filter (102) is connected with the function generator (103), the narrow linewidth optical filter (107) is connected with the second optical isolator (2), the transmission and polarization characteristics of the polarization dispersion management delay line (104) are adjustable, the polarization adjustment and control delay line (104) is used for transmitting and polarization characteristics by means of a write-down grating, a series dispersion displacement optical fiber, a dispersion compensation optical fiber, a glass, a taper or a polarization controller, the auxiliary polarization maintaining optical fiber (4) comprises a third polarization maintaining optical fiber (403), a first polarization maintaining optical fiber (401), a second polarization maintaining optical fiber (401) and a second polarization maintaining optical fiber (405) are connected with the second polarization maintaining optical fiber (401) and a second polarization maintaining optical fiber (404) are connected with the second polarization maintaining optical fiber (405), the third polarization maintaining fiber coupler (401) is respectively connected with the photoelectric detector (403), the first Faraday reflector (404) and the second Faraday reflector (405), a first delay line (402) is arranged between the third polarization maintaining fiber coupler (401) and the first Faraday reflector (404), and the photoelectric detector (403) is connected with the signal processing module (8).
2. A method of measuring a fourier domain mode locked optical frequency domain reflectometer apparatus in accordance with claim 1, wherein: it comprises the following steps:
step 1: the second optical isolator (2) and the second polarization maintaining fiber coupler (3) are divided into a trigger beam T, a reference beam R and a pumping beam P, and the three beams respectively flow into an auxiliary interferometer (4), a biaxial working polarization beam splitter prism (5) and a polarization maintaining amplifier (14);
step 2: the trigger light beam T enters a signal processing module (8) after being processed by an auxiliary interferometer (4) and is used as a trigger signal of the signal processing module (8);
step 3: the reference beam R is divided into a slow axis alignment reference beam R1 and a fast axis alignment reference beam R2 with equal amplitude by a biaxial working polarization beam splitter prism (5);
step 4: the pump beam P flows into the second delay line (13) through the 1 port and the 2 port of the polarization-preserving circulator (12), and the pump beam P and the second delay line (13) generate a measuring beam S through Rayleigh scattering interaction;
step 5: the measuring beam S is divided into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a single-axis working polarization beam splitter prism (11);
step 6: the slow axis alignment reference beam R1 and the slow axis alignment measuring beam S1 are converted into a slow axis interference signal A by a first balance detector (7) after being combined and interfered by a fourth polarization maintaining fiber coupler (6), and are input into a signal processing module (8);
step 7: after beam combination and interference of the fast axis alignment reference beam R2 and the fast axis alignment measuring beam S2 by a fifth polarization maintaining fiber coupler (10), the fast axis alignment reference beam R2 and the fast axis alignment measuring beam S2 are converted into a fast axis interference signal B by a second balance detector (9) and input into a signal processing module (8);
step 8: and the signal processing module (8) integrates the slow axis interference signal A and the fast axis interference signal B to obtain stress/strain information to be detected.
3. The method for measuring an optical frequency domain reflectometer device based on fourier domain mode locking as in claim 2, wherein: the measuring beam S in the step 5 is an arbitrarily polarized beam, whereinPolarization mode and->The polarization mode is split into a slow axis alignment measuring beam S1 and a fast axis alignment measuring beam S2 by a uniaxial working polarization beam splitter prism (11).
4. The method for measuring an optical frequency domain reflectometer device based on fourier domain mode locking as in claim 2, wherein: the signal processing method of the signal processing module (8) in the step 8 comprises the following steps:
step 8.1: the signal processing module (8) records the I A I in a single wavelength tuning period by calculating the square sum of the slow axis interference signal A and the fast axis interference signal B 2 +|B| 2 Trend over time;
step 8.2: using fast fourier transforms for |a| within a single wavelength tuning period 2 +|B| 2 The trend of change with time is processed to obtain |A| 2 +|B| 2 Distribution of different beat frequency components;
step 8.3: the sensing positions in the second delay line (13) are correlated with |A| 2 +|B| 2 The beat frequency components in the filter are in one-to-one correspondence through the pair of |A| 2 +|B| 2 The beat frequency component in (1) is subjected to local inverse fast Fourier transform to access each sensing position in the second delay line (13), and stress/strain information of the sensing position is obtained by performing cross correlation operation on the local inverse fast Fourier transform result when stress/strain exists or not.
5. The method for measuring an optical frequency domain reflectometer device based on fourier domain mode locking as in claim 2, wherein: when continuous, repetitive spectral analysis is required, the output waveform of the function generator (103) is arranged in a zigzag.
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