CN100520466C - Multi-port coupler, optical amplifier, and fiber laser - Google Patents
Multi-port coupler, optical amplifier, and fiber laser Download PDFInfo
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- CN100520466C CN100520466C CNB2007101030733A CN200710103073A CN100520466C CN 100520466 C CN100520466 C CN 100520466C CN B2007101030733 A CNB2007101030733 A CN B2007101030733A CN 200710103073 A CN200710103073 A CN 200710103073A CN 100520466 C CN100520466 C CN 100520466C
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Abstract
A multi-port coupler for coupling an pumping light source to a cladding pump fiber for optical amplification, includes a central signal fiber and a plurality of pumping fibers arranged around the central signal fiber, the central signal fiber and the plurality of pumping fibers being unified and a front side is reduced in diameter, wherein an emitted light confining waveguide part is provided around a core of the signal fiber located at the center, and the emitted light confining waveguide part whose outer diameter is larger than that of the core has a higher refractive index than a cladding and a lower refractive index than the core and the emitted light confining waveguide part is formed continuously from a splicing point of the cladding pump fiber to a coupler front end branched into multiple fibers.
Description
Technical field
The present invention relates in optical communication, particularly fiber amplifier that uses in transfer system closely or the multiport coupler that uses in fiber laser etc. are with image intensifer that has used it and fiber laser.
The application advocates right of priority 2006-260881 number to Japan's patented claim 2006-149696 number of filing an application on May 30th, 2006 and Japan's patented claim of filing an application on September 26th, 2006, quotes its content here.
Background technology
In height output image intensifer, fiber laser etc., generally adopt cladding pumping (clad-pump) structure.It is the light that will propagate for the fibre core that is amplified in the optical fiber and essential exciting light is propagated in covering and the device of the structure that provides.When being adopted widely with this cladding pumping structure, the superpower laser diode of multimode optical fiber output (below, note is made LD.) used.Cladding-pumped fiber has used the double clad structure that has the multilayer covering in the periphery of the fibre core of the rare earth element that mixed.
For the light of high power multimode LD being sent in the cladding-pumped fiber that amplifies usefulness, use multiport coupler.Multiport coupler has following function, that is, assemble the light of the multimode optical fiber more than 2 and link to each other with cladding-pumped fiber, be connected simultaneously the single-mode fiber that normal signal light passes through (below, remember and make sm fiber.) with the fibre core separately of cladding-pumped fiber.Utilize the function of this multiport coupler,, also can obtain bigger output by several LD are linked to each other with cladding-pumped fiber even a LD is output as several W.To utilize the pie graph of the image intensifer of this multiport coupler to be shown among Fig. 1.
The image intensifer 1 of Fig. 1 has the multiport coupler 2 that is launched into flashlight and exciting light, carries out the cladding-pumped fiber 3 that head end has been connected with the output terminal of this multiport coupler 2.This multiport coupler 2 forms, with the signal that constitutes by sm fiber at center with optical fiber 5 be disposed at integrated around it by exciting of constituting of many multimode optical fibers with optical fiber 4, and head end side tube reducing, and can to this by tube reducing the cladding-pumped fiber 3 used of the light amplification that is connected of output terminal inject flashlight and exciting light.Signal at this multiport coupler 2 is used on the optical fiber 5, is connected with not shown signal optical source, excites with on the optical fiber 4 at many in addition, is connected with LD10 respectively.This image intensifer 1 is by (for example wavelength 910～980nm) is injected to the covering of cladding-pumped fiber 3 with exciting light by multiport coupler 2, and will be in the fibre core of cladding-pumped fiber 3 Doped Rare Earth class ion excitation, by injecting flashlight to the fibre core of cladding-pumped fiber 3 by multiport coupler 2, and the flashlight injected is amplified, and make this flashlight (high output signal) that has been exaggerated be able to output from cladding-pumped fiber 3.In this kind image intensifer, can reach more than the 20dB when being shown with, represent to reach 1W～1kW sometimes with the highest output with the water-glass that gains.
But in the employed in the past image intensifer that has made up multiport coupler and cladding-pumped fiber, in order to improve reliability, the long lifetime of LD is used as a problem and proposes.
In order to realize the long lifetime of LD, not only the design of the high reliability of LD self is very important, and temperature control is also very important as service condition.But in the image intensifer in the past, LD breaks down suddenly because of the influence of service condition sometimes, thereby the high reliabilityization of image intensifer integral body is caused very big obstacle.
The inventor etc. further investigate, and found that, the reason that catastrophic failure takes place the LD that excites is that the high output signal light of exporting returns to image intensifer from the reflection spot of outside from image intensifer.The reason of fault is, this reflection plain edge is propagated at the fibre core of cladding-pumped fiber, the limit is reversed amplification, and the light of revealing to covering because of the junction loss that produces in being connected of cladding-pumped fiber and multiport coupler arrives and excite the LD place, excites LD and destroy.Particularly, under the gain of image intensifer is situation more than the 20dB,, surpass 10% very big light having passed through also can become behind the image intensifer even reflectivity is about 1%.When the very strong reflected light of this kind returned, the situation of pulsed laser particularly excited the light of nearly 10 times power of the output of LD self to inject LD, and LD is destroyed thus falls.
So the inventor etc. return the structure that amplifier also can not excite the inefficacy of LD in order to address this problem even sought reflected light.
But, as the conventional art of inhibitory reflex trimmed book body,, rely on optoisolator though optoisolator is also arranged, reflectivity can only be decayed to-20dB about, even also have and the corresponding very expensive problem of optoisolator of light more than the number W.
Because reflected light is the internal communication at fibre core in amplifying fiber, therefore needs only light and do not reveal, just not to exciting LD to radiate catoptrical situation from fibre core.So, investigating after why reflected light can be injected the reason of LD, find reflected light why by to exciting the LD radiation, chief reason is the fibre core junction loss to each other that has produced the coupling part of multiport coupler and cladding-pumped fiber.
Producing loss in this coupling part is because the fibre core footpath (size of intensity distributions) of two optical fiber has more different.In general high-power cladding-pumped fiber has the above fibre core footpath of diameter 20 μ m.On the other hand, the fibre core of the sm fiber that uses in the signal propagation is used directly is about 5 μ m (wavelength).Thus, particularly on the direction that reflected light is propagated, the size of the loss of connecting portion reaches more than the 5dB.
The bigger reason in fibre core footpath of cladding-pumped fiber is because the power density of light is very big in high-power amplifier, therefore to be subjected to the influence of nonlinear optical effect in optical fiber.For fear of this kind influence, in general be the diameter that increases the fibre core of cladding-pumped fiber, consequently, the luminous energy density in the optical fiber is designed as small as possible.But because in the bigger fibre core of this kind sectional area, single mode transmits very difficulty, and bending loss also becomes greatly, so is unsuitable for signal optical fiber.So, transmit with optical fiber long-pending little with core cross sections, amplify with optical fiber with core cross sections long-pending big serve as preferred.Owing in the centre of these two kinds of optical fiber multiport coupler is arranged,, just can reduce junction loss to a certain extent as long as therefore the core cross sections of this multiport coupler can be amassed the size of the centre of the sectional area that is made as two kinds of optical fiber.But, textural at multiport coupler, clearly be to reduce junction loss, not equal to be to increase junction loss.This is because because multiport coupler as a rule is with many optical fiber and an optical fiber coupling, so the external diameter of optical fiber diminishes.
Fig. 2 is the figure that represents in the past multiport coupler 2 and the structure of the connecting portion of cladding-pumped fiber 3.The cephalic par of a side that is connected with cladding-pumped fiber 3 of multiport coupler 2 forms following structure, promptly, the signal at center is excited with optical fiber 4 integrated with optical fiber 5 and around it many, and become conical surface shape, so that consistent with the external diameter of cladding-pumped fiber 3 towards the head end tube reducing.In this cephalic par, the signal at center further diminishes with the fibre core of optical fiber 5 footpath, with situation that the bigger cladding-pumped fiber 3 in fibre core footpath is connected under, the difference in the fibre core footpath of both optical fiber further becomes greatly.
If consider above situation, then on reality, be difficult to reduce junction loss as can be known in the connecting portion generation of multiport coupler.
Summary of the invention
The present invention forms in view of described situation, purpose is, be provided at the inefficacy that to eliminate the excitation source that causes by reflected light in the image intensifer that used multiport coupler or the fiber laser, the multiport coupler of the long lifetime of implement device is with image intensifer that has used it and fiber laser.
In order to reach described purpose, the invention provides a kind of multiport coupler, with the signal at center with optical fiber be disposed at around it many and excite with optical fiber integration and with head end side tube reducing and form, and the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein, outer edge at this multiport coupler is provided with covering, be provided with radiating light with the fibre core periphery of optical fiber with concentric circles at the signal that is positioned at the center and close incoming wave guide passage portion, it has the external diameter bigger than this fibre core, and it is high and than the value of described signal with the little refractive index of the described fibre core of optical fiber to have a described covering than described multiport coupler, this radiating light close incoming wave guide passage portion be formed at continuously from the connecting portion of described cladding-pumped fiber to the coupling mechanism portion end that branches into many optical fiber.
This multiport coupler can be provided with radiating light with concentric circles around with the fibre core of optical fiber at signal and close incoming wave guide passage portion.In addition, radiating light can be closed incoming wave guide passage portion is designed in the cross section that on every side have polygon of signal with the fibre core of optical fiber.
In addition, the invention provides a kind of multiport coupler, use kapillary and with the signal at center with optical fiber be disposed at its on every side many and excite and use optical fiber integration, described kapillary all is connected with the rear end of bridge joint (bridge) with optical fiber with optical fiber and described exciting with optical fiber with described signal, and the head end side tube reducing of described bridge joint with optical fiber formed, the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein be provided with radiating light with the fibre core periphery of optical fiber and close incoming wave guide passage portion at described bridge joint, it has the external diameter greater than this fibre core, and have be higher than described bridge joint with the covering of optical fiber less than the value of described bridge joint with the refractive index of the described fibre core of optical fiber, and described refractive index capillaceous is lower than the refractive index of described signal with the covering of optical fiber, and described kapillary is gone into effect for described signal with the pass that optical fiber has radiating light.
In addition, the invention provides a kind of multiport coupler, use kapillary and with the signal at center with optical fiber be disposed at its on every side many and excite and use optical fiber integration, described kapillary all is connected with the rear end of bridge joint with optical fiber with optical fiber and described exciting with optical fiber with described signal, and the head end side tube reducing of described bridge joint with optical fiber formed, the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein be provided with radiating light with the fibre core periphery of optical fiber and close incoming wave guide passage portion at described bridge joint, it has the external diameter greater than this fibre core, and have be higher than described bridge joint with the covering of optical fiber less than the value of described bridge joint with the refractive index of the described fibre core of optical fiber, and described refractive index capillaceous is identical with the refractive index of the covering of optical fiber with described signal, and describedly exciting described covering to be lower than refractive index capillaceous with optical fiber, described exciting with the covering of optical fiber gone into effect for described signal with the pass that optical fiber and described kapillary have radiating light.
This multiport coupler can be provided with radiating light with concentric circles around with the fibre core of optical fiber at bridge joint and close incoming wave guide passage portion.In addition, radiating light can be closed incoming wave guide passage portion is designed in the cross section that on every side have polygon of bridge joint with the fibre core of optical fiber.
In the multiport coupler of the present invention, be preferably radiating light and close the external diameter of incoming wave guide passage portion less than the external diameter of the signal that is connected with multiport coupler with optical fiber.
In the multiport coupler of the present invention, be preferably to be provided with signal is crossed over the radiating light decay portion that suitable distance is reeled with optical fiber.
In addition, the invention provides a kind of image intensifer, it has and relates to cladding-pumped fiber, the excitation source that described multiport coupler of the present invention, light amplification are used.
In addition, the invention provides a kind of fiber laser, it has and relates to cladding-pumped fiber, the excitation source that described multiport coupler of the present invention, light amplification are used.
Multiport coupler of the present invention is owing to be the structure that is provided with radiating light pass incoming wave guide passage portion at the signal that is positioned at the center with the fibre core periphery of optical fiber, it has the external diameter greater than this fibre core, and have and be higher than covering and less than the value of the refractive index of fibre core, therefore the reflected light that returns to LD can be closed into this radiating light and close incoming wave guide passage portion, the inefficacy of the excitation source that elimination is caused by reflected light, the long lifetime of implement device.
Image intensifer of the present invention owing to be to use relates to the structure that cladding-pumped fiber that described multiport coupler of the present invention uses exciting light and flashlight and light amplification is coupled, therefore the reflected light that returns to LD can be closed into this radiating light and close incoming wave guide passage portion, the inefficacy of the excitation source that elimination is caused by reflected light, the long lifetime of implement device.
Description of drawings
Fig. 1 is the pie graph of an example of expression image intensifer.
Fig. 2 is the sectional view of the structure of expression multiport coupler.
Fig. 3 is the sectional view of an embodiment of expression multiport coupler of the present invention.
Fig. 4 A is the drawing in side sectional elevation of the multiport coupler of Fig. 3.
Fig. 4 B～D is that expression radiating light pass incoming wave guide passage portion is the sectional view of the variation of polygon.
Fig. 5 is the exploded perspective view of second embodiment of expression multiport coupler of the present invention.
Fig. 6 is the sectional view along the A-A cut surface of Fig. 5.
Fig. 7 A is the sectional view along the B-B cut surface of Fig. 5.
Fig. 7 B～D is that expression radiating light pass incoming wave guide passage portion is the sectional view of the variation of polygon.
Fig. 8 is expression is connected the multiport coupler of Fig. 5 situation about using with non-dope DCF a exploded perspective view.
Fig. 9 is the result's of expression embodiment a chart.
Embodiment
Below, with reference to the accompanying drawings embodiments of the present invention are described.
Fig. 3 is the figure of an embodiment of expression multiport coupler of the present invention, and Fig. 3 A is the sectional view of structure of the head end side of expression multiport coupler 2, and Fig. 3 B is the sectional view of another distolateral structure of expression multiport coupler 2.
The multiport coupler 2 of present embodiment with the signal at center with optical fiber 5 be disposed at around it many and excite integrated and head end side tube reducing formed with optical fiber 4, and the cladding-pumped fiber 3 that excitation source and light amplification are used linked to each other, it is characterized in that, be provided with radiating light with fibre core 6 peripheries of optical fiber 5 with concentric circles at the signal that is positioned at the center and close incoming wave guide passage portion 7, it has the external diameter bigger than this fibre core 6, and have a value of the refractive index high and littler than fibre core 6 than covering 8, this radiating light close incoming wave guide passage portion 7 be formed at continuously from the connecting portion of cladding-pumped fiber 3 to branching into many optical fiber 4,5 coupling mechanism portion end.
The inventor etc. have analyzed and have caused the LD Failure Mechanism, produce the structure that junction loss also can not cause the inefficacy of LD even invented in multiport coupler.What the inventor etc. had in mind is the internal structure of multiport coupler.
As shown in Figure 2, multiport coupler 2 be made as with signal with optical fiber 5 be the center and around it many of proper alignment excite with optical fiber 4 and integrated.So as can be known, as shown in Figure 3, around the fibre core 6 of using optical fiber 5 at signal, when the formation radiating light slightly higher than its peripheral part refractive index closes incoming wave guide passage portion 7, even produce junction loss and produce the light of radiation towards periphery at connecting portion, also can effectively radiating light be closed in the higher zone of this refractive index into, to stop to exciting entering of port.
In addition, after further research, find to close for radiating light the refractive index contrast of incoming wave guide passage portion 7 and covering 8, preferably the diameter of this radiating light pass incoming wave guide passage portion 7 is big more then more little, and the diameter that opposite radiating light closes incoming wave guide passage portion 7 is more little then big more.
Find that the diameter D and the radiating light pass incoming wave guide passage portion 7 of closing incoming wave guide passage portion 7 at radiating light keep following formula (1) with respect to the relation of the refractive index contrast Δ of covering 8 this moment
D[μ m] * Δ [%]=certain value A ... (1)
Relation and when changing, then radiating light is closed into effect will reach certain.
At this moment, certain value A so long as with which kind of degree close into determining according to the radiating light that will spill gets final product.In addition, the fibre core footpath of the cladding-pumped fiber 3 that also can use along with light amplification of A and change with the refractive index contrast of covering.This is because the angle of the light of radiation or intensity are by fibre core 9 decision of cladding-pumped fiber 3.
This radiating light close incoming wave guide passage portion 7 need be arranged on from the connecting portion of cladding-pumped fiber 3, to signal with optical fiber 5 with excite usefulness optical fiber 4 separate areas dispersedly separately.This be because, radiating light can't be closed fashionablely when on the way, then radiating light will be coupled to exciting with optical fiber 4 from this.
In addition, radiating light closes the diameter of incoming wave guide passage portion 7, preferably less than the covering external diameter of signal with optical fiber 5.This is because if the diameter of radiating light pass incoming wave guide passage portion 7 is bigger, the radiating light of going at this waveguide road Nei Guan can and excite with optical fiber 4 couplings at the coupling mechanism terminal part.
Close the radiating light that closed in the incoming wave guide passage portion 7 shown in Fig. 3 B at radiating light, with in the optical fiber 5 during backpropagation, can be absorbed at leisure, eliminate by the resin of glass-clad outside at signal.To absorb in order promoting energetically, preferably signal to be crossed over suitable length ground with optical fiber 5 and reel with the curvature of certain limit.For example, when φ 50mm, preferably be made as about 1m.
In addition, under the situation of the optical fiber that is difficult to use suitable length, also can in clad section, add in order to the adulterant that absorbs radiating light and absorb radiating light.For example, for the light of absorbing wavelength 1064nm, the optical fiber of the Sm that mixed is effective.
To in the multiport coupler 2 of present embodiment, be provided with radiating light and close the effect that incoming wave guide passage portion 7 brought and describe.
For example, at fibre core directly is that 20 μ m, fibre core-covering refractive index contrast be 0.1% cladding-pumped fiber 3 with the fibre core of head end directly are that 2.5 μ m, fibre core-covering refractive index contrast are in being connected of 0.4% multiport coupler 2, by being made as A=3[μ m * %], just 92% of radiating light can be closed, the light that outwards radiates is made as about 8%.At this moment, the distribution example of the refractive index of multiport coupler 2 is, it is 0.4% that fibre core-radiating light closes incoming wave guide passage portion refractive index contrast, and radiating light closes the incoming wave guide passage, and portion-the covering refractive index contrast is 0.05%, and it is 60 μ m that radiating light closes incoming wave guide passage portion diameter.Described effect is when not implementing any countermeasure, if there is the reflected light about 50W to return, then it can be reduced to 4W.
In the past, in the case that causes exciting LD to lose efficacy, owing to have the situation of inefficacy under the power more than 2 times of the output that excites LD self, it was very big therefore to be reduced to 8% effect.As a rule, exciting is about 5～10W.
In addition, if be made as A=1.5[μ m * %], then in identical case, just can close into 85% of radiating light.This is 20W at for example reflected light, excites LD to take place reflected light to be reduced to 15% of 20W in the case of inefficacy, and just 3W is still effective for the protection that excites LD.
In addition, the multiport coupler 2 of present embodiment can be assembled exciting light effectively by in the radiating light pass incoming wave guide passage portion 7 that is provided with on every side of signal with optical fiber 5 to the fibre core 9 of cladding-pumped fiber 3.Under the situation of the light amplification that utilizes cladding-pumped fiber 3 to carry out, the exciting light that will distribute equably in covering absorbs extremely important with fibre core 9 effectively.As long as this exciting light can be assembled (owing to only absorbing) to fibre core 9 in fibre core, just exciting light can be absorbed effectively.For example, at signal with the fibre core periphery of optical fiber 5, be provided with diameter and be 50 μ m and refractive index contrast to be 0.1% radiating light close under the situation of incoming wave guide passage portion 7, can improve 20% by the absorption efficiency of the exciting light of the fibre core 9 of cladding-pumped fiber 3.
In addition, under the situation of multiport coupler shown in Figure 32, signal closes incoming wave guide passage portion 7 shown in Fig. 4 A with the fibre core 6 of optical fiber and radiating light of being located at around it, cross section with concentric circles, but, the present invention distinguishingly is not confined to this, and radiating light closes the cross section that incoming wave guide passage portion 7 also can have hexagonal configuration shown in Fig. 4 B, the dimetric shape shown in Fig. 4 C, the polygons such as pentagon shape shown in Fig. 4 D.Even it is polygon that radiating light closes the cross sectional shape of incoming wave guide passage portion 7, also can be identical with the situation of concentric circles, performance is closed signal with in the optical fiber 5 with reflected light, and reduces to the effect of injecting power that excites with optical fiber 4.
The cross section of closing incoming wave guide passage portion 7 at radiating light is under the situation of polygon, so-called radiating light closes the external diameter of incoming wave guide passage portion 7 less than the external diameter (covering footpath) of the signal that is connected with multiport coupler 2 with optical fiber 5, can be understood as radiating light and closes the inscribe diameter of a circle of incoming wave guide passage portion 7 less than the external diameter of signal with optical fiber 5.This be because, in this case, because of radiating light close incoming wave guide passage portion 7 on the gross section is long-pending all by in be wrapped in signal with in the cladding regions of optical fiber 5, thereby close radiating light close radiating lights in the incoming wave guide passage portion 7 will be all with signal with optical fiber 5 couplings, suppress radiating light and excite the equal effect of using optical fiber 4 to be coupled thereby can play in coupling terminal portion.
As previously mentioned, in the structure of the waveguide road of multiport coupler inside, by be provided with at the fibre core periphery with light close into the zone, just can prevent from effectively the situation that excites LD to lose efficacy further exciting light can also be distributed in the fibre core periphery effectively because of reflected light.In addition, by adopting this kind structure, just exciting light can be assembled to the fibre core periphery effectively.
In addition, multiport coupler of the present invention also can be constructed as follows, and, signal is constructed pack with exciting with optical fiber with kapillary with optical fiber that is, further its cephalic par is connected with optical fiber with the bridge joint with radiating light pass incoming wave guide passage portion and head end tube reducing portion.Below, for second embodiment of the present invention, describe with reference to Fig. 5～Fig. 8.
Fig. 5 and multiport coupler 11 shown in Figure 6 are to use kapillary 14 and excite with optical fiber 13 integrated with optical fiber 12 with many that are disposed at configuration around it signal at center, kapillary 14 with signal with optical fiber 12 and excite with optical fiber 13 and all be connected with the rear end of bridge joint with optical fiber 15, and the head end side tube reducing of bridge joint with optical fiber 15 formed, the multiport coupler 11 that the cladding-pumped fiber 16 that excitation source and light amplification are used links to each other, it is provided with radiating light at bridge joint with the fibre core 15a periphery of optical fiber 15 and closes incoming wave guide passage portion 17, it has the external diameter greater than this fibre core 15a, and has and be higher than covering 15b and less than the value of the refractive index of fibre core 15a.
Here, kapillary 14 is to have can insert signal with optical fiber 12 and excite porous capillary with a plurality of through holes (pore) of optical fiber 13.Porous capillary is in order to be connected with optical fiber fusion, is preferably by quartz glass or quartzy class glass of having added adulterant etc. to constitute.Fusion for example connects and can be undertaken by using thermals source such as arc discharge, carbon dioxide laser, oxyhydrogen flame.Inserted kapillary 14 central authorities pore signal with the fibre core 12a of optical fiber 12 by and bridge joint with the fibre core 15a coupling of optical fiber 15, inserted pore around it excite with the fibre core 13a of optical fiber 13 by and bridge joint with the covering 15b coupling of optical fiber 15.Bridge joint for example can be stretched as conical surface shape by heating with the tube reducing portion of the head end side of optical fiber 15 and form.
In this multiport coupler 11, excite the formation of using optical fiber 13 as avoiding reflected light to inject, following (1) and (2) are arranged.
(1) refractive index of kapillary 14 is lower than the refractive index of signal with the covering 12b of optical fiber 12.Under this situation, kapillary 14 is gone into effect with optical fiber 12 with regard to the pass with radiating light for signal.Thus, the refractive index of kapillary 14 is arbitrarily with exciting the magnitude relationship with the refractive index of the covering 13b of optical fiber 13, and no matter specific refractivity is higher or lower mutually with the covering 13b that excites usefulness optical fiber 13 for kapillary 14, perhaps identical can.
During this constitutes, because kapillary 14 plays the effect that radiating light closes incoming wave guide passage portion, therefore when making it to close incoming wave guide passage portion when merging with bridge joint with the radiating light of optical fiber 15, radiating light pass incoming wave guide passage portion will become by the part that forms continuously to the coupling mechanism portion end that branches into many optical fiber 12,13 from the connecting portion with cladding-pumped fiber 16.
(2) refractive index of kapillary 14 and signal are identical with the refractive index of the covering 12b of optical fiber 12, and excite the refractive index that is lower than kapillary 14 with the refractive index of the covering 13b of optical fiber 13.
Under this situation, excite covering 13b that signal is gone into effect with optical fiber 12 and kapillary 14 with regard to the pass with radiating light with optical fiber 13.
During this constitutes, when between kapillary 14 and bridge joint usefulness optical fiber 15, producing junction loss, radiating light just might be coupled with kapillary 14, yet, therefore just can suppress radiating light and situation about exciting with optical fiber 13 couplings owing to excite covering 13b that effect is gone in the pass that kapillary 14 has radiating light with optical fiber 13.
In any formation of (1), (2), be located at bridge joint and close the diameter (external diameter) of incoming wave guide passage portion 17 all preferably less than the external diameter (covering footpath) of signal with optical fiber 12 with the radiating light in the optical fiber 15.This is because if the diameter of radiating light pass incoming wave guide passage portion 17 is bigger, the radiating light that then closes in this waveguide road will and excite with optical fiber 13 couplings at the coupling mechanism terminal part.
[59] oppositely (advance from right to left among Fig. 5) in optical fiber 12 when propagating at signal closing radiating light that radiating light closes incoming wave guide passage portion 17, understand and be absorbed at leisure, eliminate by the resin of signal with the outside of the covering 12b of optical fiber 12.To absorb in order promoting energetically, preferably signal to be crossed over suitable length ground with optical fiber 12 and reel with the curvature of certain limit.For example, when φ 50mm, preferably be made as about 1m.
[60] in addition,, also can add in order to the adulterant that absorbs radiating light in the part of the covering 12b of optical fiber 12 radiating light is absorbed with under the situation of optical fiber 12 at the signal that is being difficult to use suitable length to signal.For example, for the light of absorbing wavelength 1064nm, the optical fiber of the Sm that mixed is effective.
[61], be provided with radiating light in optical fiber 15 at bridge joint and close the effect that incoming wave guide passage portion 17 brought and describe in the multiport coupler 11 of present embodiment.
[62] in kapillary 14 and signal formation with the refractive index of the covering 12b of optical fiber 12 identical (2), with the covering 12b of signal with optical fiber 12, kapillary 14 and excite fibre core 13a all to use quartz (refractive index is about 1.448) making with optical fiber 13, to excite refractive index to be made as 1.436 (refractive index contrast of fibre core 13a and kapillary 14 is 0.8%) with the covering 13b of optical fiber 13, thickness is made as 10 μ m, its result is, compare with situation about exciting with the low-refraction portion of optical fiber 13 covering 13b is not set, can reduce about 20dB (being one of about percentage) with exciting the catoptrical intensity that is coupled with optical fiber 13.
[63] in kapillary 14 and signal formation with covering 12b specific refractivity is lower mutually (1) of optical fiber 12, with signal with the covering 12b of optical fiber 12 with excite fibre core 13a all to use quartz (refractive index is about 1.448) making with optical fiber 13, to excite refractive index to be made as 1.436 with the covering 13b of optical fiber 13, thickness is made as 10 μ m, refractive index with kapillary 14 also is made as 1.436 further, its result is, compare with the formation of (2), will reduce 8dB again with exciting catoptrical intensity with optical fiber 13 couplings.If compare with the situation that low-refraction portion is not set, then reduced about 28dB.
[64] in addition, for the situation of multiport coupler shown in Figure 5 11, bridge joint closes incoming wave guide passage portion 17 with the fibre core 15a of optical fiber 15 shown in Fig. 7 A with being located at its radiating light on every side, is the structure with cross section of concentric circles.But the present invention distinguishingly is not confined to this, and radiating light closes the cross section that incoming wave guide passage portion 17 also can have hexagonal configuration shown in Fig. 7 B, the square shape shown in Fig. 7 C, the polygons such as pentagon shape shown in Fig. 7 D.Even it is polygon that radiating light closes the cross sectional shape of incoming wave guide passage portion 17, also can be identical with the situation of concentric circles, with reflected light close into bridge joint with the fibre core 15a of optical fiber 15 and with signal with optical fiber 12 couplings, performance reduces to the effect of injecting power that excites with optical fiber 13.
The cross section of closing incoming wave guide passage portion 17 at radiating light is under the situation of polygon, so-called radiating light closes the external diameter of incoming wave guide passage portion 17 less than the external diameter (covering footpath) of the signal that is connected with multiport coupler 11 with optical fiber 12, can be understood as radiating light and closes the inscribe diameter of a circle of incoming wave guide passage portion 17 less than the external diameter of signal with optical fiber 12.This be because, in this case, because of radiating light close incoming wave guide passage portion 17 on the gross section is long-pending all by in be wrapped in signal with in the cladding regions of optical fiber 12, thereby close radiating light close radiating lights in the incoming wave guide passage portion 17 will be all with signal with optical fiber 12 couplings, suppress radiating light and excite the equal effect of using optical fiber 13 to be coupled thereby can play in coupling terminal portion.
Further, in the multiport coupler 11 of present embodiment, close incoming wave guide passage portion 17 by with the periphery of the fibre core 15a of optical fiber 15 radiating light being set at bridge joint, just self-excitation in the future with the exciting light of optical fiber 13 effectively to the fibre core 16a of cladding-pumped fiber 16 convergence.Under the situation of the light amplification that utilizes cladding-pumped fiber 16 to carry out, the exciting light that will distribute equably in covering absorbs extremely important with fibre core 16a effectively.As long as this exciting light can be assembled (owing to only absorbing) to fibre core 16a in fibre core, just exciting light can be absorbed effectively.
In the example shown in Figure 5, as the cladding-pumped fiber 16 that is connected with multiport coupler 11, used following double clad structure optical fiber (DCF), promptly, in fibre core 16a, be added with rare earth element, around this fibre core 16a, have inboard covering 16b and outside covering 16c.But the multiport coupler 11 of present embodiment example is as shown in Figure 8, and it also is effective being connected with under the situation of the cladding-pumped fiber (non-dope DCF) 18 that does not add rare earth element in fibre core 18a.In this configuration example, be connected with the DCF16 of rare earth doped dvielement, be connected with the head end tube reducing portion of bridge joint with optical fiber 15 at the other end of non-dope DCF18 at the end of non-dope DCF18.
At this moment, for at the connecting portion of the DCF16 of non-dope DCF18 and rare earth doped dvielement not to the covering 18b of non-dope DCF18, the situation that 18c emits radiating light, and it is closed among the fibre core 18a, between fibre core 18a and covering 18b, 18c, also need to be provided with the radiating light that has than the value of covering 18b, refractive index that 18c is higher and lower than fibre core 18a and close incoming wave guide passage portion 19.No matter the cross sectional shape that radiating light closes incoming wave guide passage portion 19 is that concentric circles or polygon can with respect to fibre core 18a.Even the multiport coupler with this kind structure with multiport coupler is directly compared with the situation that the DCF of rare earth doped dvielement is connected, also can be with identical horizontal inhibitory reflex light to exciting injecting with optical fiber 13.
As previously mentioned, in the structure of the waveguide road of multiport coupler inside, by be provided with at the fibre core periphery with light close into the zone, just can prevent the situation that excites LD to lose efficacy effectively, even exciting light can also be distributed in the fibre core periphery effectively because of reflected light.In addition, by adopting this kind structure, exciting light can be focused at the fibre core periphery effectively.
Embodiment
In excitation wavelength is that 915nm, signal wavelength are in the image intensifer of 1064nm, uses multiport coupler of the present invention (multiport coupler shown in Figure 3), and has studied the effect that LD lost efficacy and suppresses.
Use the doubly clad optical fiber of the Yb that mixed as cladding-pumped fiber.
The size of the optical fiber of this moment is as follows.
The fibre core footpath: 20 μ m, fibre core-inboard covering refractive index contrast Δ: 0.1%, inboard covering external diameter: 400 μ m.
In addition, excite in used LD used the LD of 6 wavelength: 915nm, output: 5W.
In addition, with this fibre core footpath that excites usefulness optical fiber that excites LD to link to each other: 105 μ m, fibre core-covering refractive index contrast Δ: 0.55%.
At this moment, be provided with reflection spot, be set at about 5% of the light from image intensifer, exported and be back to image intensifer once more in the end of image intensifer.In this kind formation, two following coupling mechanisms have been installed, be respectively with multiport coupler as shown in the present with fibre core footpath: 2.5 μ m, radiating light close incoming wave guide passage portion diameter: 30 μ m, radiating light close incoming wave guide passage portion refractive index contrast: 0.1% coupling mechanism of making; Do not have radiating light and close the coupling mechanism of incoming wave guide passage portion, and test.
Consequently, do not have under the situation of coupling mechanism that radiating light closes incoming wave guide passage portion having used, with begin to test in, excite LD to have 4/6 to lose efficacy, become and can't use.
On the other hand, using under the situation that relates to coupling mechanism of the present invention that is provided with radiating light pass incoming wave guide passage portion,, the fault of LD is not taking place yet even continue to inject reflected light more than 1 hour.
Utilize computing machine to confirm this result, its result is, as shown in Figure 9, is provided with in the coupling mechanism (Fig. 9 A) that radiating light closes incoming wave guide passage portion, compares with the coupling mechanism (Fig. 9 B) that does not have radiating light to close incoming wave guide passage portion, and radiating light is closed significantly, and LD is protected.
Below, in Fig. 5, multiport coupler 11 shown in Figure 6, the embodiment that the radiating light that is provided with hexagonal configuration shown in Fig. 7 B closes incoming wave guide passage portion 17 describes.
Is 400 μ m at bridge joint with the external diameter of the covering 15b of optical fiber 15, when the diameter of fibre core 15a is 7 μ m, is that the radiating light of 45 μ m closes incoming wave guide passage portion 17 on one side formed around fibre core 15a.With in the optical fiber 15, the refractive index contrast that radiating light closes incoming wave guide passage portion 17 and covering 15b is 0.1% at this bridge joint, and the refractive index contrast that fibre core 15a and radiating light close incoming wave guide passage portion 17 is 0.18%.When the external diameter that radiating light is closed incoming wave guide passage portion 17 is similar to the diameter of a circle of hexagonal incircle and circumscribed centre, then be 42 μ m.As cladding-pumped fiber 16, having prepared fibre core directly is that 30 μ m, fibre core-covering refractive index contrast are 0.12% optical fiber.Confirmed bridge joint with the radiating light that can see which kind of degree in being connected of optical fiber 15 and cladding-pumped fiber 16 close into effect, its result is, 95% of radiating light can be gone into the fibre core 15a of bridge joint with optical fiber 15 with shangguan.
Though more than preferred embodiment of the present invention is illustrated, the present invention is not limited to these embodiment.In the scope that does not break away from purport of the present invention, can implement to constitute additional, omit, displacement and other change.The present invention is not limited to by described explanation, and the scope of the technical scheme of only being added is limited to.
Claims (12)
1. multiport coupler excites the signal at center with optical fiber integration and with head end side tube reducing and forms with being disposed at around it many with optical fiber, and the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein,
Outer edge at this multiport coupler is provided with covering,
Be provided with radiating light at the described signal that is positioned at the center with the fibre core periphery of optical fiber and close incoming wave guide passage portion, it has the external diameter bigger than this fibre core, and it is high and than the value of described signal with the little refractive index of the described fibre core of optical fiber to have a described covering than described multiport coupler, this radiating light close incoming wave guide passage portion be formed at continuously from the connecting portion of described cladding-pumped fiber to the coupling mechanism portion end that branches into many optical fiber.
2. multiport coupler according to claim 1 wherein, is provided with radiating light with concentric circles at signal around with the fibre core of optical fiber and closes incoming wave guide passage portion.
3. multiport coupler according to claim 1 wherein, closes incoming wave guide passage portion with radiating light and is designed in the cross section that on every side have polygon of signal with the fibre core of optical fiber.
4. multiport coupler, use kapillary and with the signal at center with optical fiber be disposed at its on every side many and excite and use optical fiber integration, described kapillary all is connected with the rear end of bridge joint with optical fiber with optical fiber and described exciting with optical fiber with described signal, and the head end side tube reducing of described bridge joint with optical fiber formed, the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein
Be provided with radiating light at described bridge joint with the fibre core periphery of optical fiber and close incoming wave guide passage portion, it has the external diameter greater than this fibre core, and have be higher than described bridge joint with the covering of optical fiber less than the value of described bridge joint with the refractive index of the described fibre core of optical fiber, and described refractive index capillaceous is lower than the refractive index of described signal with the covering of optical fiber, and described kapillary is gone into effect for described signal with the pass that optical fiber has radiating light.
5. multiport coupler, use kapillary and with the signal at center with optical fiber be disposed at its on every side many and excite and use optical fiber integration, described kapillary all is connected with the rear end of bridge joint with optical fiber with optical fiber and described exciting with optical fiber with described signal, and the head end side tube reducing of described bridge joint with optical fiber formed, the cladding-pumped fiber that excitation source and light amplification are used links to each other, wherein
Be provided with radiating light at described bridge joint with the fibre core periphery of optical fiber and close incoming wave guide passage portion, it has the external diameter greater than this fibre core, and have be higher than described bridge joint with the covering of optical fiber less than the value of described bridge joint with the refractive index of the described fibre core of optical fiber, and described refractive index capillaceous is identical with the refractive index of the covering of optical fiber with described signal, and describedly exciting covering to be lower than described refractive index capillaceous with optical fiber, described exciting with the described covering of optical fiber gone into effect for described signal with the pass that optical fiber and described kapillary have radiating light.
6. multiport coupler according to claim 4 wherein, is provided with radiating light with concentric circles at bridge joint around with the fibre core of optical fiber and closes incoming wave guide passage portion.
7. according to claim 4 or 5 described multiport couplers, wherein, radiating light is closed incoming wave guide passage portion be designed in the cross section that has polygon on every side of bridge joint with the fibre core of optical fiber.
8. according to any described multiport coupler in the claim 1～6, wherein, described radiating light closes the external diameter of incoming wave guide passage portion less than the external diameter of the described signal that is connected with described multiport coupler with optical fiber.
9. multiport coupler according to claim 7, wherein, described radiating light closes the external diameter of incoming wave guide passage portion less than the external diameter of the described signal that is connected with described multiport coupler with optical fiber.
10. multiport coupler according to claim 1 wherein, is provided with described signal is crossed over the radiating light decay portion that suitable distance is reeled with optical fiber.
11. an image intensifer, it has cladding-pumped fiber, excitation source that the described multiport coupler of claim 1, light amplification are used.
12. a fiber laser, it has cladding-pumped fiber, excitation source that the described multiport coupler of claim 1, light amplification are used.
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| JP2006149696 | 2006-05-30 | ||
| JP2006149696 | 2006-05-30 | ||
| JP2006260881 | 2006-09-26 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100585966C (en) * | 2008-06-04 | 2010-01-27 | 中国科学院上海光学精密机械研究所 | Laser device of optical fiber with automatic protection of semiconductor pumping sources |
| WO2010055700A1 (en) * | 2008-11-14 | 2010-05-20 | 株式会社フジクラ | Ytterbium-doped optical fiber, fiber laser and fiber amplifier |
| EP2477284B1 (en) * | 2009-10-27 | 2019-09-18 | Fujikura Ltd. | Light combiner and fiber laser device using same |
| WO2012106624A2 (en) * | 2011-02-03 | 2012-08-09 | 3Sae Technologies, Inc. | Side pump fiber, method of making same, and optical devices using same |
| US8908682B2 (en) * | 2012-02-02 | 2014-12-09 | International Business Machines Corporation | Switch discovery protocol for a distributed fabric system |
| US10603744B2 (en) * | 2017-12-18 | 2020-03-31 | Lumentum Operations Llc | Aiming beam side-coupler |
| JP7119611B2 (en) * | 2018-06-12 | 2022-08-17 | 住友電気工業株式会社 | fiber optic amplifier |
| JP7291501B2 (en) * | 2019-03-11 | 2023-06-15 | 株式会社フジクラ | Laser processing equipment |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US5864644A (en) * | 1997-07-21 | 1999-01-26 | Lucent Technologies Inc. | Tapered fiber bundles for coupling light into and out of cladding-pumped fiber devices |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5864644A (en) * | 1997-07-21 | 1999-01-26 | Lucent Technologies Inc. | Tapered fiber bundles for coupling light into and out of cladding-pumped fiber devices |
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