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

Abstract

The invention relates to a device and method for measuring an intrinsic brillouin line width of an optical fiber, which solves the problems of the requirement for a frequency scanning apparatus, the sensitivity to an optical fiber laser polarization state and the necessary consideration of the polarization pertinence of a gain in the prior art. The device for measuring the intrinsic brillouin line width of the optical fiber comprises an ultra narrow line width laser device, a first coupler, an EDFA (Erbium Doped Fiber Amplifier), a brillouin annular cavity, a first adjustable attenuator, a first polarization controller, an intensity modulator, a second adjustable attenuator, a second coupler, a unidirectional isolator, a second polarization controller, a first circulator and an oscilloscope. The method for measuring the intrinsic brillouin line width is realized based on the measuring device and comprises the following steps of: extracting a signal light gain and slow light delay information through acquiring waveforms of signal light and amplification light; and finally obtaining the intrinsic brillouin line width of the optical fiber to be measured by utilizing least squares fitting. The invention can be used for measuring the intrinsic brillouin line width in the optical fiber.

Description

Optical fiber intrinsic Brillouin linewidth measurement mechanism and measuring method

Technical field

The present invention relates to a kind of measurement mechanism and measuring method of optical fiber intrinsic Brillouin linewidth.

Background technology

At present, mainly utilize to the measurement of intrinsic Brillouin linewidth in the optical fiber and sweep spectral technology and realize.The high-frequency signal drive strength modulator that it utilizes microwave signal generator to produce makes the output laser of intensity modulator produce a certain amount of frequency displacement with respect to input laser, and frequency shift amount equals to regulate the frequency of modulation signal.Through regulating the frequency of modulation signal, thereby obtain the light signal output of different frequency displacements,, obtain the curve of frequency displacement and gain relationship through measuring the gain of light signal in Brillouin's amplification process under the different frequency displacements.From this curve, can record Brillouin linewidth.Because the influence of polarization mismatch, this measurement need be measured under polarization mismatch maximum case and minimum two states, just can record Brillouin linewidth.And maximum mismatch and minimum mismatch two states will rely on artificial observation to confirm, its accuracy Stimulated Light device itself float and human factor influences bigger.And this method needs data measured more, and source of error is also more.In addition, this method to the requirement of appointed condition than higher.Wherein, microwave signal generator costs an arm and a leg, and makes general laboratory not possess the condition of measuring the intrinsic Brillouin linewidth.

To sum up, the existing method and apparatus that is used for measuring the intrinsic Brillouin linewidth not only needs frequency sweeping equipment, and responsive to the optical-fiber laser polarization state, needs to consider the polarization correlated problem of gain.

Summary of the invention

The objective of the invention is to solve the existing method and apparatus that is used for measuring the intrinsic Brillouin linewidth; Exist need frequency sweeping equipment, responsive and needs are considered the polarization correlated problem that gains to the optical-fiber laser polarization state, and a kind of measurement mechanism and measuring method of optical fiber intrinsic Brillouin linewidth is provided.

The measurement mechanism of optical fiber intrinsic Brillouin linewidth, it is made up of super-narrow line width laser instrument, first coupling mechanism, EDFA, Brillouin's ring cavity, first adjustable attenuator, first Polarization Controller, intensity modulator, second adjustable attenuator, second coupling mechanism, one-way isolator, second Polarization Controller, first circulator and oscillograph;

The light output end of super-narrow line width laser instrument links to each other with the light input end of first coupling mechanism through optical fiber; First light output end of first coupling mechanism connects the light input end of EDFA through optical fiber; The light output end of EDFA connects the light input end of first adjustable attenuator through optical fiber; The light output end of first adjustable attenuator connects the light input end of first circulator through optical fiber; The light I/O end of first circulator is connected with an end of testing fiber through optical fiber, and the light output end of first circulator is connected with the light input end of photoelectric probe through optical fiber, and the electrical signal of said photoelectric probe connects oscillograph first signal input part;

Second light output end of first coupling mechanism connects the light input end of Brillouin's ring cavity through optical fiber; The light output end of Brillouin's ring cavity connects the light input end of first Polarization Controller through optical fiber; The light output end of first Polarization Controller is through the light input end of optical fiber strength of joint modulator; The light output end of intensity modulator connects the light input end of second adjustable attenuator through optical fiber, and the light output end of second adjustable attenuator connects the light input end of second coupling mechanism through optical fiber;

First light output end of second coupling mechanism is connected with the light input end of photoelectric probe through optical fiber; The electrical signal of said photoelectric probe connects oscillographic secondary signal input end; Second light output end of second coupling mechanism connects the light input end of one-way isolator through optical fiber; The light output end of one-way isolator connects the light input end of second Polarization Controller through optical fiber, and the light output end of second Polarization Controller is connected with the other end of testing fiber through optical fiber.

The measuring method of optical fiber intrinsic Brillouin linewidth, it realizes that based on the measurement mechanism of intrinsic Brillouin linewidth the detailed process of said measuring method is:

Step 1, adjusting first adjustable attenuator make the luminous power I through the light signal of first adjustable attenuator _PMinimum; Make S1 represent the light signal that oscillographic first signal input part receives, S2 representes the light signal that oscillographic secondary signal input end receives, and utilizes oscillograph then, obtains the waveform of light signal S1 and the waveform of light signal S2;

Step 2, the waveform parameter that obtains light signal S1 and the waveform parameter of light signal S2, and then the decay G of acquisition light signal S1 this moment and light signal S2 ₀With time-delay T ₀

Step 3, under the distortionless condition of the waveform of light signal S1, adjust first adjustable attenuator, make the luminous power I of the light signal that sees through first adjustable attenuator _PBe increased to I ₁

Step 4, the waveform that obtains light signal S1 this moment and the waveform of light signal S2, and then obtain the waveform parameter of light signal S1 and the waveform parameter of light signal S2; Through calculating, obtain the gain G of light signal S1 then ₁And the time-delay of the actual measurement between light signal S1 and S2 T ₁, the data that define this step acquisition are the data of the 1st experimental point;

Step 5, adjusting first adjustable attenuator make the luminous power I through the light signal of first adjustable attenuator _PDrop to I successively ₂, I ₃..., I _Q, wherein, Q is the positive integer more than or equal to 5; Simultaneously, respectively at said luminous power I _PBe I ₂, I ₃..., I _QThe time, obtain the waveform of every kind of light signal S1 under the luminous power condition and the waveform of light signal S2; According to the waveform of the light signal S1 under said every kind of luminous power condition and the waveform of light signal S2, obtain every kind of waveform parameter under the luminous power condition, and then calculate the actual measurement gain G that obtains the light signal S1 under every kind of luminous power condition _iAnd the time-delay of the actual measurement between light signal S1 and S2 T _i, i=2,3,4 ... Q, the definition luminous power is respectively I ₂, I ₃..., I _QThe data that obtained under the condition be respectively data, the 3rd experimental point of the 2nd experimental point data ..., the Q experimental point data;

Step 6, according to luminous power I _PEqual I respectively ₁, I ₂, I ₃..., I _QThe time corresponding actual measurement time-delay T _i, the actual measurement gain G of light signal S1 _i, and G ₀And T ₀Brillouin linewidth is made least square fitting, finally obtain the Brillouin linewidth value of testing fiber 12.

Good effect of the present invention: the measurement mechanism and the measuring method of optical fiber intrinsic Brillouin linewidth of the present invention; Do not need frequency sweeping equipment; And it is insensitive to the optical-fiber laser polarization state; Need not to consider the polarization correlated problem that gains, it is measured intensity and time two kinds of physical quantitys only, measure simple.

Description of drawings

Fig. 1 is the structural representation of the measurement mechanism of optical fiber intrinsic Brillouin linewidth of the present invention; Fig. 2 is the process flow diagram of the measuring method of optical fiber intrinsic Brillouin linewidth of the present invention.

Embodiment

Embodiment one: the measurement mechanism of the optical fiber intrinsic Brillouin linewidth of this embodiment, it is made up of super-narrow line width laser instrument 1, first coupling mechanism 2, EDFA3, Brillouin's ring cavity 4, first adjustable attenuator 5, first Polarization Controller 6, intensity modulator 7, second adjustable attenuator 8, second coupling mechanism 9, one-way isolator 10, second Polarization Controller 11, first circulator 13 and oscillograph 14;

The light output end of super-narrow line width laser instrument 1 links to each other with the light input end of first coupling mechanism 2 through optical fiber; First light output end of first coupling mechanism 2 connects the light input end of EDFA3 through optical fiber; The light output end of EDFA3 connects the light input end of first adjustable attenuator 5 through optical fiber; The light output end of first adjustable attenuator 5 connects the light input end 13-1 of first circulator 13 through optical fiber; The light I/O end 13-2 of first circulator 13 is connected with an end of testing fiber 12 through optical fiber; The light output end 13-3 of first circulator 13 is connected with the light input end of photoelectric probe through optical fiber, and the electrical signal of said photoelectric probe connects oscillograph 14 first signal input parts;

Second light output end of first coupling mechanism 2 connects the light input end of Brillouin's ring cavity 4 through optical fiber; The light output end of Brillouin's ring cavity 4 connects the light input end of first Polarization Controller 6 through optical fiber; The light output end of first Polarization Controller 6 is through the light input end of optical fiber strength of joint modulator 7; The light output end of intensity modulator 7 connects the light input end of second adjustable attenuator 8 through optical fiber, and the light output end of second adjustable attenuator 8 connects the light input end of second coupling mechanism 9 through optical fiber;

First light output end of second coupling mechanism 9 is connected with the light input end of photoelectric probe through optical fiber; The electrical signal of said photoelectric probe connects the secondary signal input end of oscillograph 14; Second light output end of second coupling mechanism 9 connects the light input end of one-way isolator 10 through optical fiber; The light output end of one-way isolator 10 connects the light input end of second Polarization Controller 11 through optical fiber, and the light output end of second Polarization Controller 11 is connected through the other end of optical fiber with testing fiber 12.

The principle of work of this measurement mechanism is following:

The laser beam of super-narrow line width laser instrument 1 output is divided into two bundles behind first coupling mechanism 2, wherein a branch of being injected among the EDFA3, and another bundle is injected in Brillouin's ring cavity 4;

EDFA3 amplifies the light beam after back output is amplified with the light beam that receives; Light beam after the amplification is incident to the light input end 13-1 of first circulator 13 again after 5 decay of first adjustable attenuator, be incident to the right-hand member of testing fiber 12 again as pump light by the light I/O end 13-2 output back of first circulator 13;

Be incident to the light beam generation stimulated Brillouin scattering in Brillouin's ring cavity 4; The stokes light beam that produces exports first Polarization Controller 6 to by Brillouin's ring cavity 4; After first Polarization Controller 6 is adjusted to the polarization state that is complementary with intensity modulator 7, from first Polarization Controller 6, export intensity modulator 7 to, intensity modulator 7 exports second adjustable attenuator 8 to after the stokes beam modulation that receives is become pulsed stokes light beam; After decaying, 8 pairs of light that receive of second adjustable attenuator export second coupling mechanism 9 to; The light that second coupling mechanism 9 will receive is divided into two bundles, and light is by a signal end reception of oscillograph 14 as a reference in wherein a branch of output, and another Shu Zuowei flashlight exports second Polarization Controller 11 to through behind one-way isolator 10; Second Polarization Controller 11 light to the received signal carries out the polarization adjusting; Said signal polarization state of light and pumping polarization state of light are complementary, then flashlight are exported to the left end of testing fiber 12, make flashlight and pump light that excited Brillouin take place in testing fiber 12 and amplify; The time-delay of generation slower rays; Flashlight after the amplification exports the light I/O end 13-2 of first circulator 13 to from the right-hand member of testing fiber 12, and from the light output end 13-3 output of first circulator 13, is received by another signal end of oscillograph 14.

The measurement mechanism of intrinsic Brillouin linewidth of the present invention; Do not need frequency sweeping equipment; Can measure the intrinsic Brillouin linewidth, and insensitive, need not to consider the polarization correlated problem that gains the optical-fiber laser polarization state; It is measured intensity and time two kinds of physical quantitys only, measure simple.

Embodiment two: this embodiment is the further qualification to the measurement mechanism of the optical fiber intrinsic Brillouin linewidth of embodiment one, and the output Wavelength of Laser of said super-narrow line width laser instrument 1 is that 1550.12nm, live width are less than 100kHz.

Embodiment three: this embodiment is the further qualification to the measurement mechanism of embodiment one or two optical fiber intrinsic Brillouin linewidth; The output splitting ratio of first coupling mechanism 2 is 50%: 50%; Second coupling mechanism, 9 output splitting ratios are 90%: 10%; And 90% output terminal is as second light output end of second coupling mechanism 9, and 10% output terminal is as first light output end of second coupling mechanism 9.

Embodiment four: this embodiment is the further qualification to the measurement mechanism of embodiment one, two or three optical fiber intrinsic Brillouin linewidth, and said Brillouin's ring cavity 4 is made up of the second circulator 4-1, the 3rd Polarization Controller 4-2, gain media optical fiber 4-3 and the 3rd coupling mechanism 4-4;

The light input end 4-1-1 of the said second circulator 4-1 is as the light input end of Brillouin's ring cavity 4; The light I/O end 4-1-2 of the second circulator 4-1 is through the light I/O end of optical fiber and the 3rd Polarization Controller 4-2; Another light I/O end of the 3rd Polarization Controller 4-2 is through the end of optical fiber connection gain media optical fiber 4-3, and the other end of gain media optical fiber 4-3 connects first light output end of the 3rd coupling mechanism 4-4 through optical fiber;

The light output end 4-1-3 of the said second circulator 4-1 connects the light input end of the 3rd coupling mechanism 4-4 through optical fiber, and second light output end of the 3rd coupling mechanism 4-4 is as the light output end of Brillouin's ring cavity 4; The output splitting ratio of the 3rd coupling mechanism 4-4 is 95%: 5%, and 5% output terminal is as first output terminal of the 3rd coupling mechanism 4-4, and 95% output terminal is as second light output end of the 3rd coupling mechanism 4-4.

Embodiment five: the measuring method of the optical fiber intrinsic Brillouin linewidth of this embodiment, it realizes that based on the measurement mechanism of optical fiber intrinsic Brillouin linewidth the detailed process of said measuring method is:

Step 1, adjusting first adjustable attenuator 5 make the luminous power I through the light signal of first adjustable attenuator 5 _PMinimum; Make S1 represent the light signal that first signal input part of oscillograph 14 receives, S2 representes the light signal that the secondary signal input end of oscillograph 14 receives, and utilizes oscillograph 14 then, obtains the waveform of light signal S1 and the waveform of light signal S2;

Step 2, the waveform parameter that obtains light signal S1 and the waveform parameter of light signal S2, and then the decay G of acquisition light signal S1 this moment and light signal S2 ₀With time-delay T ₀

Step 3, under the distortionless condition of the waveform of light signal S1, adjust first adjustable attenuator 5, make the luminous power I of the light signal that sees through first adjustable attenuator 5 _PBe increased to I ₁

Step 4, the waveform that obtains light signal S1 this moment and the waveform of light signal S2, and then obtain the waveform parameter of light signal S1 and the waveform parameter of light signal S2; Through calculating, obtain the gain G of light signal S1 then ₁And the time-delay of the actual measurement between light signal S1 and S2 T ₁, the data that define this step acquisition are the data of the 1st experimental point;

Step 5, adjusting first adjustable attenuator 5 make the luminous power I through the light signal of first adjustable attenuator 5 _PDrop to I successively ₂, I ₃..., I _Q, wherein, Q is the positive integer more than or equal to 5; Simultaneously, respectively at said luminous power I _PBe I ₂, I ₃..., I _QThe time, obtain the waveform of every kind of light signal S1 under the luminous power condition and the waveform of light signal S2; According to the waveform of the light signal S1 under said every kind of luminous power condition and the waveform of light signal S2, obtain every kind of waveform parameter under the luminous power condition, and then calculate the actual measurement gain G that obtains the light signal S1 under every kind of luminous power condition _iAnd the time-delay of the actual measurement between light signal S1 and S2 T _i, i=2,3,4 ... Q, the definition luminous power is respectively I ₂, I ₃..., I _QThe data that obtained under the condition be respectively data, the 3rd experimental point of the 2nd experimental point data ..., the Q experimental point data;

Step 6, according to luminous power I _PEqual I respectively ₁, I ₂, I ₃..., I _QThe time corresponding actual measurement time-delay T _i, the actual measurement gain G of light signal S1 _i, and G ₀And T ₀Brillouin linewidth is made least square fitting, finally obtain the Brillouin linewidth value of testing fiber 12.

The measuring method of intrinsic Brillouin linewidth of the present invention does not need frequency sweeping equipment, and insensitive to the optical-fiber laser polarization state, need not to consider the polarization correlated problem that gains, and it is measured intensity and time two kinds of physical quantitys only, measure simple.

Embodiment six: this embodiment is that the waveform parameter described in step 2, step 4 and the step 5 is meant peak value, time to peak and three parameters of pulsewidth of waveform to the further specifying of the measuring method of the optical fiber intrinsic Brillouin linewidth of embodiment five.

Embodiment seven: this embodiment is to the further specifying of the measuring method of embodiment five or six optical fiber intrinsic Brillouin linewidth, in step 2:

The decay of described light signal S1 and light signal S2

R wherein _S1Be the peak value of light signal S1 waveform, P _S2Peak value for light signal S2 waveform;

Described time-delay T ₀, the time to peak that equals light signal S1 waveform deducts the difference of the time to peak of light signal S2 waveform.

Embodiment eight: this embodiment is to the further specifying of the measuring method of embodiment five, six or seven optical fiber intrinsic Brillouin linewidth, and the calculating described in the step 5 obtains actual measurement gain G i and the time-delay of the actual measurement between light signal S1 and the S2 T of the light signal S1 under every kind of luminous power condition _iDetailed process be:

Under said every kind of luminous power condition, obtain the peak-to-peak ratio P (X) of light signal S1 and light signal S2, wherein X=I ₁, I ₂, I ₃... Or I _Q, the gain G of the light signal S1 under this kind luminous power condition then _i=10log (P (X))-G ₀

Simultaneously, under said every kind of luminous power condition, obtain the time to peak difference T (X) of the waveform of light signal S1 and S2, wherein X=I ₁, I ₂, I ₃... Or I _Q, i.e. the time to peak of the time to peak of T (X)=light signal S1 waveform-light signal S2 waveform;

The T of actual measurement between light signal S1 and S2 time-delay at this moment _i=T (X)-T ₀, when T (X) is X for luminous power, the time to peak of light signal S1 waveform deducts the difference of the time to peak of light signal S2 waveform.

Embodiment nine: this embodiment is that the detailed process of the said content of step 6 is to the further specifying of the measuring method of any one intrinsic Brillouin linewidth of the optical fiber in the embodiment five to eight:

Step 6 one, generation line width values sequence { γ ^(J), J=1,2 ..., said line width values sequence is made up of a plurality of equally spaced line width values, i.e. γ ^(J+1)-γ ^(J)=Δ, wherein Δ is a fixed value;

Step 6 two, according to the pulsewidth of measured light signal S1, utilize Fast Fourier Transform (FFT) (FFT), generate the normalized input signal light electric field intensity of amplitude frequency spectrum A _S(ω, 0), wherein the flashlight pulsewidth is provided by measured data of experiment;

Step 6 three, for each the line width values γ in the line width values sequence ^(J), the cumulative errors of theory of computation time-delay and experiment measuring time-delay: T wherein _iBe the flashlight slower rays time-delay that experiment measuring obtains, Td _iFor the slower rays that Theoretical Calculation obtains is delayed time, and then obtain error time-delay sequence { E ^J, J=1,2 ...;

Step 6 four, at said error time-delay sequence { E ^J, J=1,2 ... } and in get minimum error time-delay, then making the corresponding line width values of this error time-delay is the Brillouin linewidth value of testing fiber.

Embodiment ten: this embodiment is that the detailed process of step 6 three said contents is to the further specifying of the measuring method of the optical fiber intrinsic Brillouin linewidth of embodiment nine:

Step 631, to each line width values r ^(J), execution in step 632 to step 6 three or six obtains corresponding cumulative errors;

Going on foot the yield value that gathers 632, chooses in the 1st experimental point data is target gain, is made as G _AimMake G=g ₀I _pZ is as known variables, and the value of choosing G is as trial solution G _Try

G wherein ₀Be the gain coefficient of optical fiber, I _PBe pump light intensities, z is a testing fiber length;

Step 6 three or three, with G _TryThe substitution following formula:

$A_S(\mathrm{\ω},z)=A_S(\mathrm{\ω},0)\×\exp \left[\frac{G_{\mathrm{try}}/2}{1-\mathrm{i\ω}/\left({\mathrm{\γ}}^{\left(J\right)}\mathrm{\π}\right)}\right]$

A wherein _S(ω z) is the frequency domain electric field amplitude of output flashlight, and ω is the flashlight frequency, r ^(J)J item for the Brillouin linewidth sequence;

Following formula is carried out inverse Fourier transform, obtain through the flashlight output after Brillouin's amplification, the gain of the flashlight after the amplification of calculating output;

Gain and target gain G that step 6 three or four, determining step 633 obtain _AimWhether equate,, then utilize dichotomy to generate new G if unequal _TryValue is returned to carry out to go on foot and is gathered 633; If equate, then G _TryValue is the gain parameter that is complementary with these experimental point data; Making the yield value in next experimental point data is target gain G _Aim, and the initial value of reselecting G is as trial solution G _Try, return execution in step 633, up to the coupling of accomplishing all Q experimental point data; Execution in step 635 then;

Step 6 three or five, to each experimental point data, the gain parameter G that will be complementary _TryThe substitution step is gathered formula in 633, and it is made Fourier transform, signal calculated light time-delay Td _i, and calculate delay time error E _i=(T _i-Td _i) ², T wherein _iBe the flashlight slower rays time-delay that experiment measuring obtains, Td _iFor the slower rays that Theoretical Calculation obtains is delayed time;

Step 6 three or six, calculating obtain line width values r ^(J)Corresponding cumulative errors:

Claims (9)

1. the measurement mechanism of optical fiber intrinsic Brillouin linewidth is characterized in that it is made up of super-narrow line width laser instrument (1), first coupling mechanism (2), EDFA (3), Brillouin's ring cavity (4), first adjustable attenuator (5), first Polarization Controller (6), intensity modulator (7), second adjustable attenuator (8), second coupling mechanism (9), one-way isolator (10), second Polarization Controller (11), first circulator (13) and oscillograph (14);

The light output end of super-narrow line width laser instrument (1) links to each other with the light input end of first coupling mechanism (2) through optical fiber; First light output end of first coupling mechanism (2) connects the light input end of EDFA (3) through optical fiber; The light output end of EDFA (3) connects the light input end of first adjustable attenuator (5) through optical fiber; The light output end of first adjustable attenuator (5) connects the light input end (13-1) of first circulator (13) through optical fiber; The light I/O end (13-2) of first circulator (13) is connected through the end of optical fiber with testing fiber (12); The light output end (13-3) of first circulator (13) is connected with the light input end of photoelectric probe through optical fiber, and the electrical signal of said photoelectric probe connects oscillograph (14) first signal input parts;

Second light output end of first coupling mechanism (2) connects the light input end of Brillouin's ring cavity (4) through optical fiber; The light output end of Brillouin's ring cavity (4) connects the light input end of first Polarization Controller (6) through optical fiber; The light output end of first Polarization Controller (6) is through the light input end of optical fiber strength of joint modulator (7); The light output end of intensity modulator (7) connects the light input end of second adjustable attenuator (8) through optical fiber, and the light output end of second adjustable attenuator (8) connects the light input end of second coupling mechanism (9) through optical fiber;

First light output end of second coupling mechanism (9) is connected with the light input end of photoelectric probe through optical fiber; The electrical signal of said photoelectric probe connects the secondary signal input end of oscillograph (14); Second light output end of second coupling mechanism (9) connects the light input end of one-way isolator (10) through optical fiber; The light output end of one-way isolator (10) connects the light input end of second Polarization Controller (11) through optical fiber, and the light output end of second Polarization Controller (11) is connected through the other end of optical fiber with testing fiber (12);

Said Brillouin's ring cavity (4) is made up of second circulator (4-1), the 3rd Polarization Controller (4-2), gain media optical fiber (4-3) and the 3rd coupling mechanism (4-4);

The light input end (4-1-1) of said second circulator (4-1) is as the light input end of Brillouin's ring cavity (4); The light I/O end (4-1-2) of second circulator (4-1) is through a light I/O end of optical fiber and the 3rd Polarization Controller (4-2); Another light I/O end of the 3rd Polarization Controller (4-2) is through an end of optical fiber connection gain media optical fiber (4-3), and the other end of gain media optical fiber (4-3) connects first light output end of the 3rd coupling mechanism (4-4) through optical fiber;

The light output end (4-1-3) of said second circulator (4-1) connects the light input end of the 3rd coupling mechanism (4-4) through optical fiber, and second light output end of the 3rd coupling mechanism (4-4) is as the light output end of Brillouin's ring cavity (4); The output splitting ratio of the 3rd coupling mechanism (4-4) is 95%: 5%, and 5% output terminal is as first output terminal of the 3rd coupling mechanism (4-4), and 95% output terminal is as second light output end of the 3rd coupling mechanism (4-4).

2. the measurement mechanism of optical fiber intrinsic Brillouin linewidth according to claim 1, the output Wavelength of Laser that it is characterized in that said super-narrow line width laser instrument (1) are that 1550.12nm, live width are less than 100kHz.

3. the measurement mechanism of optical fiber intrinsic Brillouin linewidth according to claim 1; The output splitting ratio that it is characterized in that first coupling mechanism (2) is 50%: 50%; Second coupling mechanism (9) output splitting ratio is 90%: 10%; And 90% output terminal is as second light output end of second coupling mechanism (9), and 10% output terminal is as first light output end of second coupling mechanism (9).

4. the optical fibre measuring method of intrinsic Brillouin linewidth, it is realized based on the measurement mechanism of the described optical fiber intrinsic of claim 1 Brillouin linewidth, it is characterized in that the detailed process of said measuring method is:

Step 1, adjusting first adjustable attenuator (5) make the luminous power I through the light signal of first adjustable attenuator (5) _PMinimum; Make S1 represent the light signal that first signal input part of oscillograph (14) receives, S2 representes the light signal that the secondary signal input end of oscillograph (14) receives, and utilizes oscillograph (14) then, obtains the waveform of light signal S1 and the waveform of light signal S2;

Step 2, the waveform parameter that obtains light signal S1 and the waveform parameter of light signal S2, and then the decay G of acquisition light signal S1 this moment and light signal S2 ₀With time-delay T ₀

Step 3, under the distortionless condition of the waveform of light signal S1, adjust first adjustable attenuator (5), make the luminous power I of the light signal that sees through first adjustable attenuator (5) _PBe increased to I ₁

Step 4, the waveform that obtains light signal S1 this moment and the waveform of light signal S2, and then obtain the waveform parameter of light signal S1 and the waveform parameter of light signal S2; Through calculating, obtain the gain G of light signal S1 then ₁And the time-delay of the actual measurement between light signal S1 and S2 T ₁, the data that define this step acquisition are the data of the 1st experimental point;

Step 5, adjusting first adjustable attenuator (5) make the luminous power I through the light signal of first adjustable attenuator (5) _PDrop to I successively ₂, I ₃..., I _Q, wherein, Q is the positive integer more than or equal to 5; Simultaneously, respectively at said luminous power I _PBe I ₂, I ₃..., I _QThe time, obtain the waveform of every kind of light signal S1 under the luminous power condition and the waveform of light signal S2; According to the waveform of the light signal S1 under said every kind of luminous power condition and the waveform of light signal S2, obtain every kind of waveform parameter under the luminous power condition, and then calculate the actual measurement gain G that obtains the light signal S1 under every kind of luminous power condition _iAnd the time-delay of the actual measurement between light signal S1 and S2 T _i, i=2,3,4 ... Q, the definition luminous power is respectively I ₂, I ₃..., I _QThe data that obtained under the condition be respectively data, the 3rd experimental point of the 2nd experimental point data ..., the Q experimental point data;

Step 6, according to luminous power I _PEqual I respectively ₁, I ₂, I ₃..., I _QThe time corresponding actual measurement time-delay T _i, the actual measurement gain G of light signal S1 _i, and G ₀And T ₀Brillouin linewidth is made least square fitting, finally obtain the Brillouin linewidth value of testing fiber 12.

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 the step 5 is meant peak value, time to peak and three parameters of pulsewidth of waveform.

6. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4 is characterized in that in step 2:

The decay of described light signal S1 and light signal S2 P wherein _S1Be the peak value of light signal S1 waveform, P _S2Peak value for light signal S2 waveform;

Described time-delay T ₀, the time to peak that equals light signal S1 waveform deducts the difference of the time to peak of light signal S2 waveform.

7. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4 is characterized in that the calculating described in the step 5 obtains actual measurement gain G i and the time-delay of the actual measurement between light signal S1 and the S2 T of the light signal S1 under every kind of luminous power condition _iDetailed process be:

Under said every kind of luminous power condition, obtain the peak-to-peak ratio P (X) of light signal S1 and light signal S2, wherein X=I ₁, I ₂, I ₃... Or I _Q, the gain G of the light signal S1 under this kind luminous power condition then _i=10log (P (X))-G ₀

Simultaneously, under said every kind of luminous power condition, obtain the time to peak difference T (X) of the waveform of light signal S1 and S2, wherein X=I ₁, I ₂, I ₃... Or I _Q, i.e. the time to peak of the time to peak of T (X)=light signal S1 waveform-light signal S2 waveform;

The T of actual measurement between light signal S1 and S2 time-delay at this moment _i=T (X)-T ₀, when T (X) is X for luminous power, the time to peak of light signal S1 waveform deducts the difference of the time to peak of light signal S2 waveform.

8. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 4 is characterized in that the detailed process of the said content of step 6 is:

Step 6 one, generation line width values sequence { γ ^(J), J=1,2 ..., said line width values sequence is made up of a plurality of equally spaced line width values, i.e. γ ^(J+1)-γ ^(J)=Δ, wherein Δ is a fixed value;

Step 6 two, according to the pulsewidth of measured light signal S1, utilize Fast Fourier Transform (FFT) (FFT), generate the normalized input signal light electric field intensity of amplitude frequency spectrum A _S(ω, 0), wherein the flashlight pulsewidth is provided by measured data of experiment;

Step 6 three, for each the line width values γ in the line width values sequence ^(J), the cumulative errors of theory of computation time-delay and experiment measuring time-delay:

T wherein _iBe actual measurement time-delay, Td _iFor the slower rays that Theoretical Calculation obtains is delayed time, and then obtain error time-delay sequence { E ^J, J=1,2 ...;

Step 6 four, at said error time-delay sequence { E ^J, J=1,2 ... } and in get minimum error time-delay, then making the corresponding line width values of this error time-delay is the Brillouin linewidth value of testing fiber.

9. the measuring method of optical fiber intrinsic Brillouin linewidth according to claim 8 is characterized in that the detailed process of step 6 three said contents is:

Step 631, to each line width values r ^(J), execution in step 632 to step 6 three or six obtains corresponding cumulative errors;

Going on foot the yield value that gathers 632, chooses in the 1st experimental point data is target gain, is made as G _AimMake G=g ₀I _pZ is as known variables, and the value of choosing G is as trial solution G _Try

G wherein ₀Be the gain coefficient of optical fiber, I _PBe pump light intensities, z is a testing fiber length;

Step 6 three or three, with G _TryThe substitution following formula:

$A_S(\mathrm{\ω},z)=A_S(\mathrm{\ω},0)\×\exp \left[\frac{G_{\mathrm{try}}/2}{1-\mathrm{i\ω}/\left({\mathrm{\γ}}^{\left(J\right)}\mathrm{\π}\right)}\right]$

A wherein _S(ω z) is the frequency domain electric field amplitude of output flashlight, and ω is the flashlight frequency, γ ^(J)J item for the Brillouin linewidth sequence;

Following formula is carried out inverse Fourier transform, obtain through the flashlight output after Brillouin's amplification, the gain of the flashlight after the amplification of calculating output;

Gain and target gain G that step 6 three or four, determining step 633 obtain _AimWhether equate,, then utilize dichotomy to generate new G if unequal _TryValue is returned to carry out to go on foot and is gathered 633; If equate, then G _TryValue is the gain parameter that is complementary with these experimental point data; Making the yield value in next experimental point data is target gain G _Aim, and the initial value of reselecting G is as trial solution G _Try, return execution in step 633, up to the coupling of accomplishing all Q experimental point data; Execution in step 635 then;

Step 6 three or five, to each experimental point data, the gain parameter G that will be complementary _TryThe substitution step is gathered formula in 633, and it is made Fourier transform, signal calculated light time-delay Td _i, and calculate delay time error E _i=(T _i-Td _i) ², T wherein _iBe actual measurement time-delay, Td _iFor the slower rays that Theoretical Calculation obtains is delayed time;

Step 6 three or six, calculating obtain line width values r ^(J)Corresponding cumulative errors:

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