CN109378687B - Stimulated Brillouin scattering suppression method for optical fiber laser amplifier system - Google Patents
Stimulated Brillouin scattering suppression method for optical fiber laser amplifier system Download PDFInfo
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- CN109378687B CN109378687B CN201811271517.9A CN201811271517A CN109378687B CN 109378687 B CN109378687 B CN 109378687B CN 201811271517 A CN201811271517 A CN 201811271517A CN 109378687 B CN109378687 B CN 109378687B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
- H01S3/0078—Frequency filtering
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Abstract
The invention provides a method for inhibiting stimulated Brillouin scattering of an optical fiber laser amplifier system, wherein the optical fiber laser amplifier system comprises a seed source and an optical fiber amplifier, and the stimulated Brillouin scattering is inhibited by accessing an inclined optical fiber grating into the optical fiber amplifier and filtering laser input into the inclined optical fiber grating by utilizing the high loss factor of the inclined optical fiber grating in a Brillouin wave band. The inclined fiber grating has high loss in a Brillouin waveband, has a good suppression effect on backward Stokes signal light generated by the fiber laser amplifier system, can improve the integral SBS threshold of the fiber laser amplifier system, greatly reduces risks caused by high-power backward light to the fiber laser amplifier system, and improves the performance of the fiber laser amplifier system.
Description
Technical field
The invention belongs to fiber laser technology field more particularly to a kind of fiber laser amplifier system excited Brillouins
Scatter suppression method.
Background technique
Optical fiber laser amplifier has high-efficient, good beam quality, small in size, non-maintaining, low operating cost, high beam matter
The advantages that amount, running life is long, is easy to modulate, compact-sized, is widely used in fields such as military affairs, industry.Gravitational wave detection,
The special application fields such as nonlinear frequency conversion, light beam synthesis, there have to the power of optical fiber laser, line width and polarization state to be special
Requirement.High power narrow linewidth optical fiber laser amplifier is the efficient light sources for meeting these special applications.
For high power narrow linewidth optical fiber laser amplifier, since fiber lengths are longer, fiber core sectional area is smaller, when
After transimission power reaches certain level, it is easy to generate all kinds of nonlinear effects.In various nonlinear effects, excited Brillouin
The threshold value for scattering (SBS) is minimum, is the primary limiting factor that current narrow linewidth booster output is promoted.Stimulated Brillouin scattering
(SBS) effect can be generated in optical fiber laser amplifier it is high-power after to Stokes light, cause optical fiber laser amplifier to export
Efficiency decline, seriously affects the normal work of optical fiber laser amplifier, and damage to prime device.
Currently, being suggested to inhibit stimulated Brillouin scattering (SBS) effect there are many method.Application is relatively more at present
Mainly have increase optical fiber effective core area, using highly doped or large mode field optical fiber to reduce optical fiber effective length, phase tune
System broadening seed laser line width and broadening brillouin gain spectrum inhibit.Wherein, the above two are limited to the manufacture craft of optical fiber, and
The bigger meeting of optical fiber mode fields area is unfavorable for the stabilization of optical fiber laser amplifier so that the threshold value of unstable (MI) effect of mode is lower
Property and power ascension, application are still extremely limited.Broadening seed laser line width by active phase modulation inhibits excited Brillouin to dissipate
The method for penetrating (SBS) effect needs to introduce additional electricity modulation device, and subsequent also needs to carry out linewidth narrowing, system
It is very complicated.By applying temperature, stress gradient broadens the side that brillouin gain spectrum inhibits stimulated Brillouin scattering (SBS) effect
Method, control difficulty is larger, and is easy to be influenced by extraneous factor, and system is also more complicated.
Summary of the invention
In view of the defects existing in the prior art, the present invention provides a kind of fiber laser amplifier system stimulated Brillouin scattering
Suppressing method.
To realize the above-mentioned technical purpose, the technical scheme is that
Fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method, fiber laser amplifier system include seed source
And fiber amplifier, by by inclined optical fiber grating incoming fiber optic amplifier, using inclined optical fiber grating in Brillouin's wave
The high lossy of section is filtered the laser in input inclined optical fiber grating, to inhibit stimulated Brillouin scattering.Tilt optical fiber
Grating its Brillouin's wave band have high lossy, to fiber laser amplifier system generate backward Stokes signal light
With preferable inhibitory effect, it is able to ascend the SBS threshold of fiber laser amplifier system entirety, and is made due to after high power
Weaken significantly to light risk caused by fiber laser amplifier system, improves the performance of fiber laser amplifier system.
In the present invention: seed source includes pumping LD light source, pump combiner, Gao Fanguang grid, doped fiber, low reflective grid,
Pumping LD light source has multiple, and each output tail optical fiber for pumping LD light source is connected in each pumping arm of pump combiner, pumping conjunction beam
Be sequentially connected high reflective grid, doping grating and low reflective grid after the output tail optical fiber of device, the output tail optical fiber of pump combiner with
Between high reflective grid, between Gao Fanguang grid and doping grating and between doped fiber and low reflective grid by way of welding
It is attached.It is usually 2-4nm that the reflectivity of high reflective grid, which is typically larger than 99%, 3dB bandwidth,.The reflectivity of low reflective grid is logical
Often it is not more than 10%, three dB bandwidth is usually more than 1nm.Low its central wavelength of reflective grid is identical as the central wavelength of high reflective grid
Or central wavelength ± the 0.4nm no more than high reflective grid.Include signal light and Stokes signal in the output laser of seed source
Two kinds of ingredients of light.
The fiber amplifier includes signal pump combiner and doped fiber, in signal pump combiner and doped fiber
Between access inclined optical fiber grating.Its both ends of the inclined optical fiber grating by way of welding respectively with signal pump combiner
Output tail optical fiber and doped fiber input terminal connection.Or the inclined optical fiber grating is directly prepared on doped fiber,
Inclined optical fiber grating is inscribed on doped fiber optical fiber, inscribes the doped fiber for having inclined optical fiber grating and beam is closed in signal pumping
The output tail optical fiber of device connects.
Further, the fiber amplifier includes n grades of fiber amplifiers, n >=1.Letter in fiber amplifiers at different levels
Number inclined optical fiber grating is accessed between pump combiner and doped fiber, using inclined optical fiber grating its in Brillouin's wave band
High lossy is filtered the laser inputted in its inclined optical fiber grating of fiber amplifier at different levels, to inhibit excited Brillouin
Scattering effect promotes the working efficiency of fiber amplifiers at different levels, while can play buffer action between certain grade, to backward
Stokes signal light has stronger attenuation.Meanwhile in order to further decrease splice loss, splice attenuation, in fiber amplifiers at different levels
In, inclined optical fiber grating can directly be prepared on doped fiber further to promote fiber amplifier performances at different levels.For into
One step improves inhibitory effect, in fiber amplifiers at different levels, can be come further by way of increasing inclined optical fiber grating number
It improves and inhibits ratio.The identical inclined optical fiber grating of multiple parameters is one another in series by way of welding and is followed by together into each
Between signal pump combiner and doped fiber in grade fiber amplifier.It, can by the control to inclined optical fiber grating number
To accomplish that inhibition ratio is adjusted flexibly.
Inclined optical fiber grating is to be presented periodic refractive index modulation along optical fiber axial direction in fibre core, but its grating planar
With optical fiber tangentially in certain inclination angle.It is preceding to the fibre core intermode with reverse transfers in addition to existing due to the presence of tilt angle
Coupling is outer, and there is also the cladding modes or radiation mode of the core mode of fl transmission and reverse transfers (assuming that cladding diameter is infinitely great
In the case of) between coupling.It will appear many discrete resonance peaks in the transmitted spectrum intermediate waves region of inclined optical fiber grating.These
Discrete resonance peak bandwidth in 0.2nm magnitude, can be used as fiber grating narrow-band filter.It in this way can will be special
The long core light of standing wave is filtered out into covering.In general, influence inclined optical fiber grating transmitted spectral characteristics because be known as screen periods,
Tilt angle, modulation depth etc. are balanced by the selection to these factors, its resonance peak wave-length coverage can be adjusted,
And it is used as fiber grating filter.It is analogous to the condition of resonance of Bragg fiber grating, for common Bragg light
Fine grating, the resonance wavelength for meeting Bragg diffraction conditions can indicate are as follows:
WhereinIt is the effective refractive index of core mode, ΛgIt is screen periods.It can be seen that screen periods determine grating
Central wavelength.For inclined optical fiber grating, Bragg resonance wavelength expression formula are as follows:
In formula, θ is inclined optical fiber grating tilt angle.Due to the presence at inclination angle, Bragg resonance wavelength can change
Become, while the core mode for having part fl transmission is coupled in the cladding mode of reverse transfer, resonance wavelength can be expressed as:
WhereinIt is the effective refractive index of the i-th rank cladding mode.
Screen periods determine raster center wavelength.Currently, 1,1.5,2 micron of operation wavelength is often used for fiber oscillator device,
The covering of inclined optical fiber grating operation wavelength can be realized by the adjustment to screen periods.With the increase of tilt angle,
Will appear more high-order cladding mode resonants, it is whole mobile to shortwave direction spectrally to show as resonance envelope, and bandwidth with
Widen, but the depth shallower of transmission spectrum.The modulation depth of inclined optical fiber grating directly determines the depth of transmission peaks, transmission
The depth at peak is to filter out the important indicator of Brillouin's Stokes signal light.The modulation depth of inclined optical fiber grating is stronger, transmission peaks
Depth is deeper, it is meant that better to the filtration result of Brillouin's Stokes signal light.The maximum that inclined optical fiber grating can achieve
Modulation depth depends primarily on the photosensitive amount of optical fiber used by inscribing inclined optical fiber grating, and the photosensitive amount of optical fiber is bigger, carves
It is bigger to write the attainable maximum percentage modulation of inclined optical fiber grating institute.Although optical fiber itself has light sensitivity, it is still desirable to pass through
The mode for carrying hydrogen can further enhance its light sensitivity, and it is different because of optical fiber concrete type to carry the hydrogen time.Mould big for big core diameter
Field optical fiber, Chang Wei 8 weeks.Therefore the filtration result that can reach according to actual needs treats the optical fiber for inscribing inclined optical fiber grating
Selection is suitable to carry the hydrogen time.But the difficulty that excessive tilt angle can be such that inclined optical fiber grating inscribes increases, therefore wants root
Tilt angle is reasonably selected according to required operation wavelength, to reach optimal filtration result.In general, when SBS effect occurs, light
Stokes signal light and signal light are spaced in 0.08nm magnitude in spectrum, can be carried out according to this to the parameter of inclined optical fiber grating
It calculates.Typically for inclined optical fiber grating, it is contemplated that its effective refractive index desirable 1.443 after inclination, according to wavelength and period
Corresponding relationship λ=2neffΛ can calculate its screen periods of inclined optical fiber grating.For the tilt angle of inclined optical fiber grating, examine
Consider wavelength interval, inscribe the various factors such as complexity, generally takes between 4-6 °；Specific value should inscribe production according to practical
Inclined optical fiber grating spectrum out is accepted or rejected.
The generation of SBS effect can be described as pump light and Stokes signal light by acoustic wavefield carry out it is non-linear mutually
Effect.It can cause the generation of refractive-index grating in optical fiber when pumping light power reaches certain level, which passes through Prague
Diffraction scattering pump light, to Stokes signal light after formation.Backward Stokes signal light is interfered with pump light, passes through electricity
Flex effect is caused to generate sound wave, the acoustic wavefield back scattering of modulated media refractive index and enhancing to pumping laser in turn.Pass through
Inclined optical fiber grating introduces the loss near Stokes signal light wavelength, even if the power density of pump light reaches in optical fiber laser
To its power threshold, the Stokes signal light of generation is depleted, apparent stimulated Brillouin scattering phenomenon will not be generated,
Apparent stimulated Brillouin scattering phenomenon can be just seen under higher power level, to obtain higher SBS threshold value.Cause
This is lost Stokes signal light wavelength nearby larger by adjusting the tilt angle of inclined optical fiber grating,
To the intensity of Stokes signal light after capable of being significantly inhibited in fiber amplifier；Meanwhile near signal light wavelength, loss
It is minimum, will not introduce it is higher other loss to influence efficiency of amplitude so that under higher output power just it is observed that
SBS improves the SBS threshold of amplifier, to achieve the purpose that inhibit SBS so as to improve the output characteristics of amplifier.
It pumps LD light source and pump light necessary to generating laser is provided, pump light couples supreme reflective via pump combiner
At grid, pump light is injected into doped fiber via high reflective grid, and doped fiber can absorb pump light and inspire signal light,
And it is exported via low reflective grid；Seed source output signal light is injected into optical fiber through the signal pump combiner in fiber amplifier and puts
In doped fiber in big device, the pump light of signal pump combiner is also injected into the doped fiber in fiber amplifier and is passed through
Doped fiber absorbs, and pump light is converted to signal light rapidly, when the signal light intensity in fiber amplifier is more than certain threshold value,
SBS effect can be generated, the pump light for continuing to inject doped fiber at this time can be converted to Stokes light rapidly, be formed stronger backward
Stokes light, include the laser of signal light and backward two kinds of light of Stokes light by inclined optical fiber grating when, due to oblique light
Fine grating fibers are lost small in signal light-wave strong point, have high lossy in Stokes signal light-wave strong point, in laser
Stokes signal is optically coupled to fibre cladding and loses, and the Stokes signal light intensity in laser can generate decaying, to press down
The generation of excited Brillouin process processed, so that excited Brillouin process could be generated under the conditions of higher level-one amplifying power,
To have the function that improve SBS threshold.
Compared with the prior art, the advantages of the present invention are as follows:
1, inclined optical fiber grating is simple for production, and screen periods, tilt angle, modulation can be adjusted flexibly according to actual needs deeply
The parameters such as degree, to match different inhibition wave bands.
2, inclined optical fiber grating is lost small in signal light-wave strong point, has high lossy in Stokes signal light-wave strong point.
Inclined optical fiber grating is convenient simultaneously is prepared on different type optical fiber, and stability is good, has wide range of applications.Tilt optical fiber light
Grid can be prepared directly on doped fiber, and overall losses are further decreased.
3, by controlling the number of the concatenated inclined optical fiber grating of welding, inhibition ratio is adjusted flexibly.
4, the addition of inclined optical fiber grating can play good buffer action to Stokes signal light to rear.
Detailed description of the invention
Fig. 1 is the schematic diagram of the embodiment of the present invention 1；
Fig. 2 is the schematic diagram of the embodiment of the present invention 2；
Fig. 3 is the schematic diagram of the embodiment of the present invention 3；
Fig. 4 is the schematic diagram of the embodiment of the present invention 4；
Fig. 5 is the schematic illustration of inclined optical fiber grating used in the present invention；
Fig. 6 is the typical transmission spectrogram and partial enlarged view of inclined optical fiber grating used in the present invention；
Specific embodiment
With reference to the accompanying drawing, embodiments of the present invention are described in further detail.
Fig. 1 is the structural schematic diagram of the embodiment of the present invention 1.High fiber laser amplifier system includes seed source 8 and
Level-one fiber amplifier 9, the first order fiber amplifier 9 include signal pump combiner 10 and doped fiber 4, are pumped in signal
Inclined optical fiber grating 6 is accessed between Pu bundling device 10 and doped fiber 4.By the way that inclined optical fiber grating 6 is accessed first order optical fiber
In amplifier 9, using inclined optical fiber grating 6 Brillouin's wave band high lossy, to input inclined optical fiber grating 6 in laser
It is filtered, to inhibit stimulated Brillouin scattering.
Seed source 8 includes pumping LD light source 1, pump combiner 2, Gao Fanguang grid 3, doped fiber 4, low reflective grid 5.Pumping
LD light source has multiple, and each output tail optical fiber for pumping LD light source 1 is connected in each pumping arm of pump combiner 2.Shown in Fig. 1
For schematic diagram, parameter, selection wavelength, output power of LD light source etc. are pumped because practical and different, without particular/special requirement.
High reflective grid 3, doping grating 4 and low reflective grid 5, pump are sequentially connected after the output tail optical fiber of pump combiner 2
Between the output tail optical fiber of Pu bundling device 2 and high reflective grid 3, between Gao Fanguang grid 3 and doping grating 4 and doped fiber 4 with it is low
It is attached by way of welding between reflective grid 5, forms fusing point 7 at posetionof weld.Pump LD light source 1, beam is closed in pumping
The fiber oscillator device that device 2, Gao Fanguang grid 3, doped fiber 4, low reflective grid 5 and fusing point 7 are constituted, as high power optical fibre laser
The seed source 8 of amplifier system.1 grade of fiber amplifier, i.e. n=1 are introduced in embodiment shown in FIG. 1.Inclined optical fiber grating 6 is logical
The mode for crossing welding is connected between the signal pump combiner 10 in first order fiber amplifier 9 and doped fiber 4.Wherein:
Currently, most common pumping source wavelength has 976nm, 915nm.The LD pumping source of both wavelength can be selected in pumping LD light source 1,
Output power is in hectowatt magnitude.Pump combiner 2 be 7*1 fiber pump combiner, pump LD light source 1 in 976nm,
The output tail optical fiber of 915nmLD pumping source is connected by way of welding to be connected with the pumping arm of pump combiner 2, pump combiner
2 output optical fibre is large mode field optical fiber.Typically, the output optical fibre of pump combiner 2 is the LMA-GDF- of Nufern company
20/400-M optical fiber.Such as common wavelengths 1080nm at laser works wavelength, reflectivity is typically larger than high reflective grid 3
99%, three dB bandwidth is usually 2-4nm, and Gao Fanguang grid 3 are prepared on the identical optical fiber of output optical fibre of same pump combiner 2.
Doped fiber 4 should choose the doped fiber to match with high reflective 3 fiber size of grid, numerical aperture, be typically Nufern company
LMA-YDF-20/400-M optical fiber.Output optical fibre of the low reflective grid 5 as seed source, the reflectivity of low reflective grid 5 is usually not
Greater than 10%, three dB bandwidth is usually more than 1nm, the difference of low reflective its central wavelength of grid 5 and the central wavelength of high reflective grid 3
No more than ± 0.4nm.
It pumps LD light source 1 and pump light necessary to generating laser is provided, pump light couples supreme anti-via pump combiner 2
At grating 3.High reflective grid and low reflective grid are only in signal light-wave strong point, as there is reflection at 1080nm, in pump wavelength
Place is not reflected, only lossy.Pump light is injected into doped fiber 4 via high reflective grid 3, and doped fiber usually adulterates ytterbium etc.
Rare earth element, doped fiber 4 can absorb pump light and inspire signal light, and export via low reflective grid 5.Seed source output
Signal light is injected into the doping in first order fiber amplifier 9 through the signal pump combiner 10 in first order fiber amplifier 9
In optical fiber 4, passed through in the doped fiber 4 that the pump light of signal pump combiner 10 is also injected into first order fiber amplifier 9
Doped fiber 4 absorbs, and pump light is converted to signal light rapidly.When the signal light intensity in fiber amplifier is more than certain threshold value
When, SBS effect can be generated, the pump light for continuing to inject doped fiber at this time can be converted to Stokes light rapidly, be formed stronger
Backward Stokes light, as shown in figure 1 shown in hollow arrow.It include the laser of two kinds of light of signal light and backward Stokes light by inclining
When oblique fiber grating 6, since inclined optical fiber grating optical fiber 6 is small in the loss of signal light-wave strong point, in Stokes signal light-wave strong point
With high lossy, the Stokes signal in laser is optically coupled to fibre cladding and loses, the Stokes signal light in laser
Intensity can generate decaying, to inhibit the generation of excited Brillouin process, so that under the conditions of higher level-one amplifying power
Excited Brillouin process can be generated, to have the function that improve SBS threshold.
Inclined optical fiber grating 6 is due to its unique Mode Coupling characteristic, the interior Stokes signal light meeting transmitted of fiber core
It intercouples with the mode in covering, it is caused to be coupled to fibre cladding and is scattered and lost, so that 6 in Stokes signal light-wave strong point
There are the narrow loss spectra of a very bandwidth, the Stokes signal light intensity in laser can generate decaying, as shown in figure 1 filled arrows institute
Show.In this way, being decayed by introducing high loss at Stokes wavelength to Stokes signal strength, to inhibit to be excited cloth
In deep process generation.So that excited Brillouin process could be generated under the conditions of higher level-one amplifying power, to reach
Improve the effect of SBS threshold.The addition of inclined optical fiber grating 6 has inhibiting effect to Stokes light to rear, so that risk is reduced,
And play buffer action.In order to further enhance amplifier SBS inhibitory effect, the identical inclined optical fiber grating of multiple parameters can be with
The signal pump combiner in fiber amplifier is accessed after being together in series by way of welding and between doped fiber, is inhibited
Inhibit the superposition of ratio than being equivalent to multiple inclined optical fiber gratings.By the control to inclined optical fiber grating number, can accomplish pair
Inhibit being adjusted flexibly for ratio.
Fig. 2 is the structural schematic diagram of the embodiment of the present invention 2.Difference from example 1 is that in embodiment 2, first
The directly preparation of inclined optical fiber grating 6 in grade fiber amplifier 9 inscribes oblique light on doped fiber 4 on doped fiber 4
Fine grating 6, inscription have the doped fiber 4 of inclined optical fiber grating 6 to connect with the output tail optical fiber of signal pump combiner 10.It inhibits
Process and principle are same as Example 1, are not repeating herein.
Fig. 3 is the structural schematic diagram of the embodiment of the present invention 3.In embodiment shown in Fig. 3, in Fig. 1 or 2 illustrated embodiments
On the basis of, introduce the 2nd grade of fiber amplifier 11, i.e. n=2.In first order fiber amplifier 9 and the 2nd grade of first order optical fiber
Inclined optical fiber grating 6 is accessed between signal pump combiner 10 in amplifier 11 and doped fiber 4.
After the 1st grade of first order fiber amplifier 9 amplifies, the output laser power of the 1st grade of first order fiber amplifier 9
It is higher, in some instances it may even be possible to Raman threshold is had reached, wherein remaining Stokes signal light intensity is equally also amplified, optical fiber
Laser power is higher, in some instances it may even be possible to SBS threshold is had reached, after the amplification of second level fiber amplifier, it is most likely that
There is stronger backward Stokes signal, as shown in hollow arrow in figure.When it is by the inclination optical fiber in second level fiber amplifier
When grating 6, due to its unique Mode Coupling characteristic, the Stokes signal transmitted in fiber core can be with the mode phase in covering
Mutual coupling causes it to be coupled to fibre cladding and is scattered and lost, so that inclined optical fiber grating 6 exists in Stokes signal light-wave strong point
The narrow loss spectra of one very bandwidth, the Stokes signal strength in laser can generate decaying, as shown in filled arrows in figure.By right
The adjustment of the parameters such as screen periods, tilt angle, the modulation depth of inclined optical fiber grating 6, makes at its Stokes wavelength that there are one
Pole narrowband loss spectra, decays to Stokes signal strength, during the entire process of Stokes light is generated and is transmitted, to its into
Row inhibits, to have the function that improve SBS threshold.In first order fiber amplifier 9 and the 2nd grade of first order fiber amplifier
After inclined optical fiber grating 6 is added in 11, the 2nd grade of first order fiber amplifier efficiency can be promoted, while can be played certain
Grade between buffer action, to it is rear to Stokes signal light have stronger attenuation, to seed source and first order fiber amplifier
Device plays a protective role.
Fig. 4 is the structural schematic diagram of the embodiment of the present invention 4.In embodiment shown in Fig. 4, embodiment shown in Fig. 3
On the basis of, introduce 3rd level fiber amplifier 12, i.e. n=3.In first order fiber amplifier 9, the 2nd grade of first order fiber amplifier
11 and the signal pump combiner 10 in 3rd level fiber amplifier 12 and inclined optical fiber grating is accessed between doped fiber 4
6.Its process of inhibition and principle are similar to Example 3, are not repeating herein.
Fig. 5 is the schematic illustration of inclined optical fiber grating used in the present invention.It is similar with common Bragg fiber grating,
Inclined optical fiber grating is also that periodic refractive index modulation is presented along optical fiber axial direction in fibre core, be a difference in that grating planar with
Optical fiber is tangentially in certain inclination angle.Due to the presence of tilt angle, in addition to there is the preceding coupling to the fibre core intermode with reverse transfers
Outside closing, there is also the cladding modes or radiation mode of the core mode of fl transmission and reverse transfers (assuming that the feelings of cladding diameter infinity
Under condition) between coupling.It will appear many discrete resonance peaks in the transmitted spectrum intermediate waves region of inclined optical fiber grating, here it is
The coupling phenomenon of core mode and covering intermode.
Fig. 6 is that the typical transmission spectrum for the inclined optical fiber grating that the present invention uses and partial enlarged view, wave band are selected as inhibiting
The backward Stokes signal light wavelength 1064.06nm of 1064nm laser.In actual use, the central wavelength of inclined optical fiber grating is needed
Actual needs is matched by design.Its fiber type should flexible choice according to actual needs.
When accessing inclined optical fiber grating, under higher pump power, just it is observed that apparent Stokes light echo,
SBS threshold, which has, to be obviously improved；With the further promotion of pump power, the power of Stokes light echo is not compared to accessing grating
When, it is decreased obviously, and as inclined optical fiber grating welding serial number purpose increases, Stokes light echo power can be further
Decline.
The foregoing is merely a preferred embodiment of the present invention, are not intended to restrict the invention, for this field
For technical staff, the invention may be variously modified and varied.All within the spirits and principles of the present invention, made any
Modification, equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.
Claims (9)
1. a kind of fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method, which is characterized in that optical fiber laser amplifier
System includes seed source and fiber amplifier, by utilizing inclination optical fiber in inclined optical fiber grating incoming fiber optic amplifier
Grating is filtered the laser in input inclined optical fiber grating in the high lossy of Brillouin's wave band, to inhibit to be excited in cloth
Deep pool scattering；
The fiber amplifier includes signal pump combiner and doped fiber, between signal pump combiner and doped fiber
Access inclined optical fiber grating；
Seed source output signal light is injected into the doping light in fiber amplifier through the signal pump combiner in fiber amplifier
In fibre, the pump light of signal pump combiner is also injected into the doped fiber in fiber amplifier by doped fiber absorption,
Pump light is converted to signal light rapidly, when the signal light intensity in fiber amplifier is more than certain threshold value, can generate SBS effect
It answers, the pump light for continuing to inject doped fiber at this time can be converted to Stokes light rapidly, form stronger backward Stokes light, packet
When laser containing signal light and backward two kinds of light of Stokes light passes through inclined optical fiber grating, since inclined optical fiber grating optical fiber exists
The loss of signal light-wave strong point is small, has high lossy in Stokes signal light-wave strong point, the Stokes signal optical coupling in laser
It to fibre cladding and loses, the Stokes signal light intensity in laser can generate decaying, to inhibit excited Brillouin process
Generation improve SBS threshold to reach so that excited Brillouin process could be generated under the conditions of higher level-one amplifying power
The effect of value.
2. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 1, which is characterized in that
Its both ends of the inclined optical fiber grating by way of welding respectively with the output tail optical fiber of signal pump combiner and doping light
Fine input terminal connection.
3. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 1, which is characterized in that
The inclined optical fiber grating is directly prepared inscribes inclined optical fiber grating on doped fiber on doped fiber optical fiber, and inscription has
The doped fiber of inclined optical fiber grating is connect with the output tail optical fiber of signal pump combiner.
4. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 1, which is characterized in that
The fiber amplifier includes n grades of fiber amplifiers, n >=1；Signal pump combiner and doping in fiber amplifiers at different levels
Inclined optical fiber grating is accessed between optical fiber.
5. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 4, which is characterized in that
In fiber amplifiers at different levels, after the identical inclined optical fiber grating of multiple parameters is one another in series together by way of welding
The signal pump combiner in fiber amplifiers at different levels is accessed and between doped fiber, by adjusting inclined optical fiber grating number
Mode realizes the adjustment for inhibiting ratio.
6. pressing down according to claim 1 to fiber laser amplifier system stimulated Brillouin scattering described in any claim in 5
Method processed, which is characterized in that seed source includes pumping LD light source, pump combiner, Gao Fanguang grid, doped fiber, low reflective grid,
Pumping LD light source has multiple, and each output tail optical fiber for pumping LD light source is connected in each pumping arm of pump combiner, pumping conjunction beam
Be sequentially connected high reflective grid, doping grating and low reflective grid after the output tail optical fiber of device, the output tail optical fiber of pump combiner with
Between high reflective grid, between Gao Fanguang grid and doping grating and between doped fiber and low reflective grid by way of welding
It is attached.
7. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 6, which is characterized in that
It pumps LD light source and pump light necessary to generating laser is provided, pump light couples at supreme reflective grid via pump combiner, pump
Pu light is injected into doped fiber via high reflective grid, and doped fiber can absorb pump light and inspire signal light, and via
Low reflective grid output.
8. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 7, which is characterized in that
By the adjustment of screen periods, tilt angle, modulation depth to inclined optical fiber grating to match different inhibition wave bands, In
Stokes signal light wavelength nearby introduces high loss.
9. fiber laser amplifier system stimulated Brillouin scattering (SBS) suppression method according to claim 1, which is characterized in that
The tilt angle of inclined optical fiber grating takes 4-6 °.
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|---|---|---|---|
| CN201811271517.9A CN109378687B (en) | 2018-10-29 | 2018-10-29 | Stimulated Brillouin scattering suppression method for optical fiber laser amplifier system |
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| CN111564750B (en) * | 2020-05-18 | 2021-05-07 | 中国人民解放军国防科技大学 | System and method for inhibiting stimulated Brillouin scattering effect in high-power narrow-linewidth optical fiber laser amplifier |
| CN115395362B (en) * | 2022-10-27 | 2023-03-24 | 中国航天三江集团有限公司 | System and method for inhibiting SBS (styrene butadiene styrene) in optical fiber |
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