CN101995222B - Device and method for measuring intrinsic brillouin line width of optical fiber - Google Patents

Abstract

Optical fiber intrinsic Brillouin linewidth measurement device and measurement method, relates to a fiber optic intrinsic Brillouin linewidth measurement device and measurement method, which solves the problems in the prior art that require frequency scanning equipment and the polarization state of optical fiber laser Sensitive and need to consider the polarization dependence of the gain. A measuring device for the intrinsic Brillouin linewidth of an optical fiber, which consists of an ultra-narrow linewidth laser, a first coupler, an EDFA, a Brillouin ring cavity, a first adjustable attenuator, a first polarization controller, an intensity modulator, It consists of a second adjustable attenuator, a second coupler, a one-way isolator, a second polarization controller, a first circulator and an oscilloscope. The measurement method of the intrinsic Brillouin linewidth is realized based on the above-mentioned measuring device. By obtaining the waveforms of the signal light and the amplified light, the signal light gain and slow light delay information are extracted, and the least squares fitting is used to finally obtain the optical fiber to be tested. Intrinsic Brillouin linewidth. The invention can be used to measure the intrinsic Brillouin line width in the optical fiber.

Description

Optical fiber intrinsic Brillouin linewidth measurement device and measurement method

technical field

The invention relates to a measuring device and a measuring method for the intrinsic Brillouin line width of an optical fiber.

Background technique

At present, the measurement of the intrinsic Brillouin linewidth in an optical fiber is mainly realized by scanning spectrum technology. It uses the high-frequency signal generated by the microwave signal generator to drive the intensity modulator, so that the output laser of the intensity modulator produces a certain amount of frequency shift relative to the input laser, and the frequency shift is equal to the frequency of the modulation signal. By adjusting the frequency of the modulation signal, the optical signal output with different frequency shifts can be obtained, and by measuring the gain of the optical signal under different frequency shifts during the Brillouin amplification process, the curve of the relationship between the frequency shift and the gain is obtained. The Brillouin line width can be measured from this curve. Due to the influence of polarization mismatch, this measurement needs to be measured in the two states of the maximum polarization mismatch and the minimum situation to measure the Brillouin linewidth. The two states of maximum mismatch and minimum mismatch are determined by human observation, and their accuracy is greatly affected by the drift of the laser itself and human factors. Moreover, this method requires more measurement data and more sources of error. In addition, this method has relatively high requirements on equipment conditions. Among them, microwave signal generators are expensive, so that ordinary laboratories do not have the conditions to measure the intrinsic Brillouin linewidth.

To sum up, the existing methods and equipment for measuring the intrinsic Brillouin linewidth not only require frequency scanning equipment, but also are sensitive to the polarization state of the fiber laser, and the polarization dependence of the gain needs to be considered.

Contents of the invention

The purpose of the present invention is to solve the problems existing in the existing method and equipment for measuring the intrinsic Brillouin linewidth that require frequency scanning equipment, be sensitive to the polarization state of the fiber laser, and need to consider the polarization dependence of the gain, and provide A measuring device and measuring method for the intrinsic Brillouin linewidth of an optical fiber.

A measuring device for the intrinsic Brillouin linewidth of an optical fiber, which consists of an ultra-narrow linewidth laser, a first coupler, an EDFA, a Brillouin ring cavity, a first adjustable attenuator, a first polarization controller, an intensity modulator, Composed of a second adjustable attenuator, a second coupler, a one-way isolator, a second polarization controller, a first circulator and an oscilloscope;

The optical output end of the ultra-narrow linewidth laser is connected to the optical input end of the first coupler through an optical fiber, the first optical output end of the first coupler is connected to the optical input end of the EDFA through an optical fiber, and the optical output end of the EDFA is connected to the optical input end through an optical fiber. The optical input end of an adjustable attenuator, the optical output end of the first adjustable attenuator is connected to the optical input end of the first circulator through an optical fiber, and the optical input/output end of the first circulator is connected to one end of the optical fiber to be tested through an optical fiber connected, the optical output end of the first circulator is connected to the optical input end of the photoelectric probe through an optical fiber, and the electrical signal output end of the photoelectric probe is connected to the first signal input end of the oscilloscope;

The second optical output end of the first coupler is connected to the optical input end of the Brillouin ring cavity through an optical fiber, and the optical output end of the Brillouin ring cavity is connected to the optical input end of the first polarization controller through an optical fiber, and the first polarization controller The optical output end of the intensity modulator is connected to the optical input end of the intensity modulator through an optical fiber, the optical output end of the intensity modulator is connected to the optical input end of the second adjustable attenuator through an optical fiber, and the optical output end of the second adjustable attenuator is connected to the optical input end of the second adjustable attenuator through an optical fiber. The optical input end of the two couplers;

The first optical output end of the second coupler is connected to the optical input end of the photoelectric probe through an optical fiber, the electrical signal output end of the photoelectric probe is connected to the second signal input end of the oscilloscope, and the second optical output end of the second coupler The optical input end of the one-way isolator is connected through an optical fiber, the optical output end of the one-way isolator is connected with the optical input end of the second polarization controller through an optical fiber, and the optical output end of the second polarization controller is connected to the other end of the optical fiber to be tested through an optical fiber. connected at one end.

A method for measuring the intrinsic Brillouin linewidth of an optical fiber is implemented based on a measuring device for the intrinsic Brillouin linewidth. The specific process of the measurement method is:

Step 1. Adjust the first adjustable attenuator so that the optical power _IP of the optical signal passing through the first adjustable attenuator is the lowest; let S1 represent the optical signal received by the first signal input end of the oscilloscope, and S2 represent the optical signal of the oscilloscope. The optical signal received by the second signal input end, and then use the oscilloscope to obtain the waveform of the optical signal S1 and the waveform of the optical signal S2;

Step 2, obtaining the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2, and then obtaining the attenuation G ₀ and the delay T ₀ of the optical signal S1 and the optical signal S2 at this time;

Step 3. Under the condition that the waveform of the optical signal S1 is not distorted, adjust the first adjustable attenuator to increase the optical power _IP of the optical signal passing through the first adjustable attenuator to I ₁ ;

Step 4. Obtain the waveform of the optical signal S1 and the waveform of the optical signal S2 at this time, and then obtain the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2; and then obtain the gain _G1 of the optical signal S1 and the optical signals S1 and S2 through calculation The measured time delay T ₁ between defines the data obtained in this step as the data of the first experimental point;

Step 5. Adjust the first adjustable attenuator so that the optical power _IP of the optical signal passing through the first adjustable attenuator decreases to I ₂ , I ₃ , ..., I _Q sequentially, where Q is greater than or equal to 5 positive integer; at the same time, when the optical power I _P is I ₂ , I ₃ , ..., I _Q respectively, obtain the waveform of the optical signal S1 and the waveform of the optical signal S2 under each optical power condition; according to each The waveform of the optical signal S1 and the waveform of the optical signal S2 under different optical power conditions, obtain the waveform parameters under each optical power condition, and then calculate and obtain the measured gain G _i and optical signal S1 of the optical signal S1 under each optical power condition The measured delay T _i between S1 and S2, i=2, 3, 4...Q, the data obtained under the conditions of defining the optical power as I ₂ , I ₃ ,..., _IQ are respectively the second experimental point Data, the data of the 3rd experimental point, ..., the data of the Qth experimental point;

Step 6: According to the measured delay T _i corresponding to when the optical power _IP is equal to I ₁ , I ₂ , I ₃ , ..., I _Q respectively, the measured gain G _i of the optical signal S1, and the pair of G ₀ and T ₀ The Brillouin linewidth is fitted by least squares, and finally the Brillouin linewidth value of the optical fiber 12 to be tested is obtained.

Positive effects of the present invention: The measuring device and measuring method of the intrinsic Brillouin linewidth of the optical fiber of the present invention do not require frequency scanning equipment, and are not sensitive to the polarization state of the fiber laser, and do not need to consider the polarization dependence of the gain. Measuring two physical quantities of intensity and time, the measurement is simple and easy.

Description of drawings

Fig. 1 is a schematic structural diagram of a measuring device for the intrinsic Brillouin linewidth of an optical fiber of the present invention; Fig. 2 is a flowchart of a measuring method for the intrinsic Brillouin linewidth of an optical fiber of the present invention.

Detailed ways

Specific embodiment one: the measuring device of the fiber intrinsic Brillouin linewidth of the present embodiment, it is made of ultra-narrow linewidth laser 1, the first coupler 2, EDFA3, Brillouin ring cavity 4, the first adjustable attenuation 5, the first polarization controller 6, the intensity modulator 7, the second adjustable attenuator 8, the second coupler 9, the one-way isolator 10, the second polarization controller 11, the first circulator 13 and the oscilloscope 14 composition;

The optical output end of the ultra-narrow linewidth laser 1 is connected to the optical input end of the first coupler 2 through an optical fiber, the first optical output end of the first coupler 2 is connected to the optical input end of the EDFA3 through an optical fiber, and the optical output end of the EDFA3 is passed through The optical fiber is connected to the optical input end of the first adjustable attenuator 5, and the optical output end of the first adjustable attenuator 5 is connected to the optical input end 13-1 of the first circulator 13 by an optical fiber, and the optical input of the first circulator 13/ The output end 13-2 is connected with one end of the optical fiber 12 to be tested through an optical fiber, and the optical output end 13-3 of the first circulator 13 is connected with the optical input end of the photoelectric probe through an optical fiber, and the electrical signal output end of the photoelectric probe is Connect the first signal input end of the oscilloscope 14;

The second optical output end of the first coupler 2 is connected to the optical input end of the Brillouin ring cavity 4 through an optical fiber, and the optical output end of the Brillouin ring cavity 4 is connected to the optical input end of the first polarization controller 6 through an optical fiber. The optical output end of a polarization controller 6 is connected to the optical input end of the intensity modulator 7 through an optical fiber, and the optical output end of the intensity modulator 7 is connected to the optical input end of the second adjustable attenuator 8 through an optical fiber, and the second adjustable attenuator The optical output end of 8 is connected to the optical input end of the second coupler 9 through an optical fiber;

The first light output end of the second coupler 9 is connected with the optical input end of the photoelectric probe through the optical fiber, and the electrical signal output end of the photoelectric probe is connected with the second signal input end of the oscilloscope 14, and the second signal input end of the second coupler 9 The optical output end is connected to the optical input end of the one-way isolator 10 through an optical fiber, the optical output end of the one-way isolator 10 is connected to the optical input end of the second polarization controller 11 through an optical fiber, and the optical output end of the second polarization controller 11 passes through The optical fiber is connected with the other end of the optical fiber 12 to be tested.

The measuring device works as follows:

The laser beam output by the ultra-narrow linewidth laser 1 is divided into two beams by the first coupler 2, one of which is injected into the EDFA3, and the other beam is injected into the Brillouin ring cavity 4;

EDFA3 amplifies the received light beam and outputs the amplified light beam, and the amplified light beam is attenuated by the first adjustable attenuator 5, and then enters the optical input end 13-1 of the first circulator 13, and then the first circulator The optical input/output port 13-2 of 13 is output as pumping light and is incident to the right end of the optical fiber 12 to be tested;

The light beam incident into the Brillouin ring cavity 4 undergoes stimulated Brillouin scattering, and the generated stokes beam is output from the Brillouin ring cavity 4 to the first polarization controller 6, and adjusted to the intensity modulation by the first polarization controller 6 After the polarization state matched by the polarizer 7, it is output from the first polarization controller 6 to the intensity modulator 7, and the intensity modulator 7 modulates the received stokes beam into a pulsed stokes beam and then outputs it to the second adjustable attenuator 8 , the second adjustable attenuator 8 attenuates the received light and outputs it to the second coupler 9, and the second coupler 9 divides the received light into two beams, one of which is output as a reference light by the oscilloscope 14 One signal end is received, and the other beam is output to the second polarization controller 11 after passing through the one-way isolator 10 as signal light, and the second polarization controller 11 performs polarization adjustment on the received signal light to make the polarization of the signal light The state matches the polarization state of the pump light, and then the signal light is output to the left end of the optical fiber 12 to be tested, so that the signal light and the pump light undergo stimulated Brillouin amplification in the optical fiber 12 to be tested, resulting in a slow light delay , the amplified signal light is output from the right end of the optical fiber 12 to be tested to the optical input/output end 13-2 of the first circulator 13, and is output from the optical output end 13-3 of the first circulator 13, and is output by the oscilloscope 14 The other signal terminal receives.

The measuring device of the intrinsic Brillouin linewidth of the present invention can measure the intrinsic Brillouin linewidth without frequency scanning equipment, and is insensitive to the polarization state of the fiber laser, without considering the polarization dependence of the gain, It only measures two physical quantities of intensity and time, and the measurement is simple and easy.

Embodiment 2: This embodiment is a further limitation of the measuring device for the intrinsic Brillouin linewidth of the optical fiber in Embodiment 1. The output laser of the ultra-narrow linewidth laser 1 has a wavelength of 1550.12nm and a linewidth of less than 100kHz .

Specific embodiment three: this embodiment is a further limitation to the measurement device of the fiber intrinsic Brillouin linewidth of embodiment one or two, the output splitting ratio of the first coupler 2 is 50%: 50%, the second coupling The output splitting ratio of the device 9 is 90%:10%, and the 90% output end is used as the second light output end of the second coupler 9, and the 10% output end is used as the first light output end of the second coupler 9.

Embodiment 4: This embodiment is a further limitation of the measurement device for the intrinsic Brillouin linewidth of the optical fiber in Embodiment 1, 2 or 3. The Brillouin ring cavity 4 is composed of a second circulator 4-1, Composed of a third polarization controller 4-2, a gain medium fiber 4-3 and a third coupler 4-4;

The optical input end 4-1-1 of the second circulator 4-1 is used as the optical input end of the Brillouin ring cavity 4, and the optical input/output end 4-1-2 of the second circulator 4-1 passes through the optical fiber One optical input/output end of the third polarization controller 4-2, the other optical input/output end of the third polarization controller 4-2 is connected to one end of the gain medium fiber 4-3 through an optical fiber, and the gain medium fiber 4- The other end of 3 is connected to the first optical output end of the third coupler 4-4 through an optical fiber;

The optical output end 4-1-3 of the second circulator 4-1 is connected to the optical input end of the third coupler 4-4 through an optical fiber, and the second optical output end of the third coupler 4-4 serves as a Brillouin The optical output end of the ring cavity 4; the output light splitting ratio of the third coupler 4-4 is 95%: 5%, and the output end of 5% is used as the first output end of the third coupler 4-4, and the output of 95% end as the second light output end of the third coupler 4-4.

Specific embodiment five: the method for measuring the intrinsic Brillouin linewidth of an optical fiber in this embodiment is implemented based on a measuring device for the intrinsic Brillouin linewidth of an optical fiber. The specific process of the measurement method is:

Step 1, adjust the first adjustable attenuator 5, so that the optical power _IP of the optical signal passing through the first adjustable attenuator 5 is the lowest; let S1 represent the optical signal received by the first signal input end of the oscilloscope 14, and S2 Represent the optical signal received by the second signal input end of the oscilloscope 14, and then use the oscilloscope 14 to obtain the waveform of the optical signal S1 and the waveform of the optical signal S2;

Step 2, obtaining the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2, and then obtaining the attenuation G ₀ and the delay T ₀ of the optical signal S1 and the optical signal S2 at this time;

Step 3. Under the condition that the waveform of the optical signal S1 is not distorted, adjust the first adjustable attenuator 5 to increase the optical power _IP of the optical signal passing through the first adjustable attenuator 5 to I ₁ ;

Step 4. Obtain the waveform of the optical signal S1 and the waveform of the optical signal S2 at this time, and then obtain the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2; and then obtain the gain _G1 of the optical signal S1 and the optical signals S1 and S2 through calculation The measured time delay T ₁ between defines the data obtained in this step as the data of the first experimental point;

Step 5. Adjust the first adjustable attenuator 5, so that the optical power _IP of the optical signal transmitted through the first adjustable attenuator 5 is sequentially reduced to I ₂ , I ₃ , ..., I _Q , where Q is greater than or equal to a positive integer of 5; at the same time, when the optical power _IP is I ₂ , I ₃ , ..., I _Q respectively, obtain the waveform of the optical signal S1 and the waveform of the optical signal S2 under each optical power condition; according to the Describe the waveform of the optical signal S1 and the waveform of the optical signal S2 under each optical power condition, obtain the waveform parameters under each optical power condition, and then calculate and obtain the measured gain G _i of the optical signal S1 under each optical power condition and The measured delay T _i between the optical signals S1 and S2, i=2, 3, 4...Q, the data obtained under the conditions of defining the optical power as I ₂ , I ₃ ,..., _IQ are respectively the second experiment The data of the point, the data of the 3rd experimental point, ..., the data of the Qth experimental point;

Step 6: According to the measured delay T _i corresponding to when the optical power _IP is equal to I ₁ , I ₂ , I ₃ , ..., I _Q respectively, the measured gain G _i of the optical signal S1, and the pair of G ₀ and T ₀ The Brillouin linewidth is fitted by least squares, and finally the Brillouin linewidth value of the optical fiber 12 to be tested is obtained.

The method for measuring the intrinsic Brillouin linewidth of the present invention does not require frequency scanning equipment, is insensitive to the polarization state of the fiber laser, and does not need to consider the polarization correlation problem of the gain. It only measures two physical quantities of intensity and time, and the measurement is simple easy.

Specific embodiment six: this embodiment is a further description of the method for measuring the intrinsic Brillouin linewidth of an optical fiber in embodiment five, and the waveform parameters described in step 2, step 4 and step 5 refer to the peak value and peak value of the waveform Time, and pulse width three parameters.

Specific embodiment seven: This embodiment is a further description of the method for measuring the intrinsic Brillouin linewidth of an optical fiber in embodiment five or six, in step two:

其中R_S1为光信号S1波形的峰值，P_S2为光信号S2波形的峰值；The attenuation of the optical signal S1 and the optical signal S2

Where R _S1 is the peak value of the optical signal S1 waveform, and P _S2 is the peak value of the optical signal S2 waveform;

The time delay T ₀ is equal to the difference between the peak time of the waveform of the optical signal S1 minus the peak time of the waveform of the optical signal S2 .

Embodiment 8: This embodiment is a further description of the method for measuring the intrinsic Brillouin linewidth of an optical fiber in Embodiment 5, 6 or 7. The calculation described in step 5 obtains the optical signal under each optical power condition The specific process of the measured gain Gi of S1 and the measured delay T _i between optical signals S1 and S2 is:

Under each optical power condition, the peak-to-peak ratio P(X) of the optical signal S1 and the optical signal S2 is obtained, where X=I ₁ , I ₂ , I ₃ , ... or I _Q , then under the optical power condition The gain G _i of the optical signal S1 = 10log(P(X))-G ₀ ;

At the same time, under each of the optical power conditions, the peak time difference T(X) of the waveforms of the optical signals S1 and S2 is obtained, where X=I ₁ , I ₂ , I ₃ , ... or I _Q , that is, T(X) =peak time of optical signal S1 waveform-peak time of optical signal S2 waveform;

At this time, the measured delay between optical signals S1 and S2 is T _i =T(X)-T ₀ , where T(X) is the peak time of the optical signal S1 waveform minus the peak time of the optical signal S2 waveform when the optical power is X difference.

Specific Embodiment Nine: This embodiment is a further description of any method for measuring the intrinsic Brillouin linewidth of an optical fiber in Embodiments five to eight, and the specific process of the content described in step six is:

Step 61. Generate a line width value sequence {γ ^(J) , J=1, 2, ...}, the line width value sequence is composed of a plurality of equally spaced line width values, namely γ ^(J+1) -γ ^(J) = Δ, where Δ is a fixed value;

Step 62. According to the measured pulse width of the optical signal S1, the fast Fourier transform (FFT) is used to generate an amplitude-normalized optical field intensity spectrum A _S (ω, 0) of the input signal, wherein the signal light The pulse width is provided by the experimental measurement data;

Step 63. For each line width value γ ^(J) in the line width value sequence, calculate the cumulative error between the theoretical delay and the experimentally measured delay: Where T _i is the slow light delay of the signal light measured experimentally, Td _i is the slow light delay obtained by theoretical calculation, and then the error delay sequence {E ^J , J=1, 2,...} is obtained;

Step 64: Take the smallest error delay in the error delay sequence {E ^J , J=1, 2, ...}, then let the line width corresponding to the error delay be the layout of the optical fiber to be tested Rieouin line width value.

Specific Embodiment Ten: This embodiment is a further description of the method for measuring the intrinsic Brillouin linewidth of an optical fiber in Embodiment 9, and the specific process of the content described in step 63 is:

Step 631, for each line width value r ^(J) , execute step 632 to step 636 to obtain the corresponding cumulative error;

Step six three two, select the gain value in the data of the first experimental point as the target gain, and set it as G _aim ; make G=g ₀ I _p z as the unknown variable, and select the value of G as the trial solution G _try ;

Where g ₀ is the gain coefficient of the fiber, I _P is the intensity of the pump light, and z is the length of the fiber to be tested;

Step 633, substitute G _try into the following formula:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; try</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i\&omega;</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>$

Where A _S (ω, z) is the frequency-domain electric field amplitude of the output signal light, ω is the signal light frequency, r ^(J) is the Jth item of the Brillouin linewidth sequence;

Perform Fourier inverse transform on the above formula to obtain the signal light output after Brillouin amplification, and calculate the gain of the output amplified signal light;

Step 634, judge whether the gain obtained in step 633 is equal to the target gain G _aim , if not, use the dichotomy method to generate a new G _try value, return to execute step 633; if equal, then G _try The value is the gain parameter that matches the data of the experimental point; let the gain value in the data of the next experimental point be the target gain G _aim , and reselect the initial value of G as the tentative solution G _try , and return to step 633 until Complete the matching of all Q experimental point data; then perform steps six to three;

Step 635. For each experimental point data, substitute the matching gain parameter G _try into the formula in step 633, and perform Fourier transform on it, calculate the signal light delay Td _i , and calculate the delay Error E _i =(T _i -Td _i ) ² , where T _i is the slow light delay of signal light measured experimentally, and Td _i is the slow light delay obtained by theoretical calculation;

Step 636, calculate and obtain the cumulative error corresponding to the line width value r ^(J) :

Claims (9)

1. The measurement device of optical fiber intrinsic Brillouin linewidth is characterized in that it consists of ultra-narrow linewidth laser (1), first coupler (2), EDFA (3), Brillouin ring cavity (4), The first adjustable attenuator (5), the first polarization controller (6), the intensity modulator (7), the second adjustable attenuator (8), the second coupler (9), the one-way isolator (10 ), a second polarization controller (11), a first circulator (13) and an oscilloscope (14); The optical output end of the ultra-narrow linewidth laser (1) is connected to the optical input end of the first coupler (2) through an optical fiber, and the first optical output end of the first coupler (2) is connected to the optical fiber of the EDFA (3) through an optical fiber. Input end, the optical output end of EDFA (3) connects the optical input end of the first adjustable attenuator (5) through the optical fiber, the optical output end of the first adjustable attenuator (5) connects the first circulator (13) through the optical fiber ), the optical input/output end (13-2) of the first circulator (13) is connected with one end of the optical fiber to be tested (12) through an optical fiber, and the first circulator (13) The optical output end (13-3) of the optical fiber is connected with the optical input end of the photoelectric probe, and the electrical signal output end of the photoelectric probe is connected with the first signal input end of the oscilloscope (14); The second optical output end of the first coupler (2) is connected to the optical input end of the Brillouin ring cavity (4) through an optical fiber, and the optical output end of the Brillouin ring cavity (4) is connected to the first polarization controller ( 6), the optical output end of the first polarization controller (6) is connected to the optical input end of the intensity modulator (7) through an optical fiber, and the optical output end of the intensity modulator (7) is connected to the second adjustable polarization end through an optical fiber. The optical input end of the attenuator (8), the optical output end of the second adjustable attenuator (8) is connected to the optical input end of the second coupler (9) through an optical fiber; The first optical output end of the second coupler (9) is connected with the optical input end of the photoelectric probe through the optical fiber, and the electrical signal output end of the photoelectric probe is connected with the second signal input end of the oscilloscope (14), and the second coupler The second optical output end of (9) connects the optical input end of the one-way isolator (10) through the optical fiber, and the optical output end of the one-way isolator (10) connects the optical input end of the second polarization controller (11) through the optical fiber , the optical output end of the second polarization controller (11) is connected to the other end of the optical fiber to be tested (12) through an optical fiber; The Brillouin ring cavity (4) is composed of a second circulator (4-1), a third polarization controller (4-2), a gain medium fiber (4-3) and a third coupler (4-4) composition; The optical input end (4-1-1) of the second circulator (4-1) is used as the optical input end of the Brillouin ring cavity (4), and the optical input/output of the second circulator (4-1) One end (4-1-2) is connected to an optical input/output end of the third polarization controller (4-2) through an optical fiber, and another optical input/output end of the third polarization controller (4-2) is connected through an optical fiber One end of the gain medium fiber (4-3), the other end of the gain medium fiber (4-3) is connected to the first light output end of the third coupler (4-4) through an optical fiber; The optical output end (4-1-3) of the second circulator (4-1) is connected to the optical input end of the third coupler (4-4) through an optical fiber, and the optical input end of the third coupler (4-4) Two light output ends are as the light output end of Brillouin ring cavity (4); The output light splitting ratio of the third coupler (4-4) is 95%: 5%, and the output end of 5% is as the third coupler ( 4-4) of the first output end, 95% of the output end is used as the second light output end of the third coupler (4-4). 2. The device for measuring the intrinsic Brillouin linewidth of an optical fiber according to claim 1, characterized in that the output laser of the ultra-narrow linewidth laser (1) has a wavelength of 1550.12nm and a linewidth of less than 100kHz. 3. The measuring device of optical fiber intrinsic Brillouin linewidth according to claim 1, characterized in that the output splitting ratio of the first coupler (2) is 50%: 50%, and the output of the second coupler (9) The light splitting ratio is 90%:10%, and the 90% output end is used as the second light output end of the second coupler (9), and the 10% output end is used as the first light output end of the second coupler (9). 4. the optical fiber measurement method of intrinsic Brillouin linewidth, it realizes based on the measuring device of optical fiber intrinsic Brillouin linewidth according to claim 1, it is characterized in that the concrete process of described measurement method is: Step 1, adjust the first adjustable attenuator (5), so that the optical power _IP of the optical signal passing through the first adjustable attenuator (5) is the lowest; let S1 represent that the first signal input terminal of the oscilloscope (14) receives The optical signal received, S2 represents the optical signal received by the second signal input end of the oscilloscope (14), and then utilizes the oscilloscope (14) to obtain the waveform of the optical signal S1 and the waveform of the optical signal S2; Step 2, obtaining the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2, and then obtaining the attenuation G ₀ and the delay T ₀ of the optical signal S1 and the optical signal S2 at this time; Step 3, under the condition that the waveform of the optical signal S1 is not distorted, adjust the first adjustable attenuator (5), so that the optical power IP of the optical signal passing through the first adjustable attenuator (5) is raised _to I ₁ ; Step 4. Obtain the waveform of the optical signal S1 and the waveform of the optical signal S2 at this time, and then obtain the waveform parameters of the optical signal S1 and the waveform parameters of the optical signal S2; and then obtain the gain _G1 of the optical signal S1 and the optical signals S1 and S2 through calculation The measured time delay T ₁ between defines the data obtained in this step as the data of the first experimental point; Step 5. Adjust _the first adjustable attenuator (5), so that the optical power IP of the optical signal passing through the first adjustable attenuator (5) decreases to I ₂ , I ₃ , ..., I _Q sequentially, wherein, Q is a positive integer greater than or equal to 5; at the same time, when the optical power _IP is I ₂ , I ₃ , ..., _IQ , respectively, the waveform of the optical signal S1 and the waveform of the optical signal S2 under each optical power condition are obtained Waveform: According to the waveform of the optical signal S1 and the waveform of the optical signal S2 under each optical power condition, obtain the waveform parameters under each optical power condition, and then calculate and obtain the actual measurement of the optical signal S1 under each optical power condition The gain G _i and the measured delay T _i between the optical signals S1 and S2, i=2, 3, 4...Q, the data obtained under the conditions of defining the optical power as I ₂ , I ₃ ,..., _IQ respectively It is the data of the 2nd experimental point, the data of the 3rd experimental point, ..., the data of the Qth experimental point; Step 6: According to the measured delay T _i corresponding to when the optical power _IP is equal to I ₁ , I ₂ , I ₃ , ..., I _Q respectively, the measured gain G _i of the optical signal S1, and the pair of G ₀ and T ₀ The Brillouin linewidth is fitted by least squares, and finally the Brillouin linewidth value of the optical fiber 12 to be tested is obtained. 5. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4 is characterized in that the waveform parameter described in step 2, step 4 and step 5 refers to the peak value, peak time and pulse width of waveform Three parameters. 6. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4, is characterized in that in step 2: The attenuation of the optical signal S1 and the optical signal S2 Wherein P _S1 is the peak value of the optical signal S1 waveform, and P _S2 is the peak value of the optical signal S2 waveform; The time delay T ₀ is equal to the difference between the peak time of the waveform of the optical signal S1 minus the peak time of the waveform of the optical signal S2 . 7. The method for measuring the intrinsic Brillouin linewidth of an optical fiber according to claim 4, characterized in that the calculation described in step 5 obtains the measured gain Gi and the optical signal S1 of the optical signal S1 under each optical power condition The specific process of the measured delay T _i between S2 and S2 is: Under each optical power condition, the peak-to-peak ratio P(X) of the optical signal S1 and the optical signal S2 is obtained, where X=I ₁ , I ₂ , I ₃ , ... or I _Q , then under the optical power condition The gain G _i of the optical signal S1 = 10log(P(X))-G ₀ ; At the same time, under each of the optical power conditions, the peak time difference T(X) of the waveforms of the optical signals S1 and S2 is obtained, where X=I ₁ , I ₂ , I ₃ , ... or I _Q , that is, T(X) =peak time of optical signal S1 waveform-peak time of optical signal S2 waveform; At this time, the measured delay time between optical signals S1 and S2 is T _i =T(X)-T ₀ , where T(X) is the peak time of the optical signal S1 waveform minus the peak time of the optical signal S2 waveform when the optical power is X difference. 8. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4, is characterized in that the concrete process of content described in step 6 is: Step 61. Generate a line width value sequence {γ ^(J) , J=1, 2, ...}, the line width value sequence is composed of a plurality of equally spaced line width values, namely γ ^(J+1) -γ ^(J) = Δ, where Δ is a fixed value; Step 62: According to the measured pulse width of the optical signal S1, the fast Fourier transform (FFT) is used to generate an amplitude-normalized optical field intensity spectrum A _S (ω, 0) of the input signal, wherein the signal light The pulse width is provided by the experimental measurement data; Step 63. For each line width value γ ^(J) in the line width value sequence, calculate the cumulative error between the theoretical delay and the experimentally measured delay:

Where T _i is the measured delay, Td _i is the slow light delay obtained by theoretical calculation, and then the error delay sequence {E ^J , J=1, 2,...} is obtained; Step 64: Take the smallest error delay in the error delay sequence {E ^J , J=1, 2, ...}, then let the line width corresponding to the error delay be the layout of the optical fiber to be tested Rieouin line width value. 9. The measuring method of optical fiber intrinsic Brillouin linewidth according to claim 8, is characterized in that the concrete process of content described in step six three is: Step 631, for each line width value r ^(J) , execute step 632 to step 636 to obtain the corresponding cumulative error; Step six three two, select the gain value in the data of the first experimental point as the target gain, and set it as G _aim ; make G=g ₀ I _p z as the unknown variable, and select the value of G as the trial solution G _try ; Where g ₀ is the gain coefficient of the fiber, I _P is the intensity of the pump light, and z is the length of the fiber to be tested; Step 633, substitute G _try into the following formula: ${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; try</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i\&omega;</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; J</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ]</span>$ Where A _S (ω, z) is the frequency-domain electric field amplitude of the output signal light, ω is the frequency of the signal light, and γ ^(J) is the Jth item of the Brillouin linewidth sequence; Perform Fourier inverse transform on the above formula to obtain the signal light output after Brillouin amplification, and calculate the gain of the output amplified signal light; Step 634, judge whether the gain obtained in step 633 is equal to the target gain G _aim , if not, use the dichotomy method to generate a new G _try value, return to execute step 633; if equal, then G _try The value is the gain parameter that matches the data of the experimental point; let the gain value in the data of the next experimental point be the target gain G _aim , and reselect the initial value of G as the tentative solution G _try , and return to step 633 until Complete the matching of all Q experimental point data; then perform steps six to three; Step 635. For each experimental point data, substitute the matching gain parameter G _try into the formula in step 633, and perform Fourier transform on it, calculate the signal light delay Td _i , and calculate the delay Error E _i =(T _i -Td _i ) ² , where T _i is the measured delay, and Td _i is the theoretically calculated slow light delay; Step 636, calculate and obtain the cumulative error corresponding to the line width value r ^(J) :

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