阅读说明：本技术 基于光纤端面微结构的LP01-LPmn全光纤模式转换器及其制备方法 (LP based on fiber end face micro-structure01-LPmnAll -fiber mode converter and preparation method thereof ) 是由 付松年 张聪 唐明 刘德明 于 2019-08-15 设计创作，主要内容包括：本发明公开了一种基于光纤端面微结构的LP_(01)-LP_(mn)全光纤模式转换器及其制备方法,全光纤模式转换器包括依次相连的单模输入光纤、少模激励光纤、少模输出光纤,在少模激励光纤的尾端具有端面微结构。制备方法包括由聚焦后的飞秒激光对少模激励光纤端面进行纤芯材料选择性去除加工,纤芯材料去除之后形成的空气层和未被激光去除的纤芯共同形成少模激励光纤端面微结构；将单模输入光纤,具有端面微结构的少模激励光纤,少模输出光纤依次熔接在一起,形成全光纤模式转换器。本发明提供的光纤模式转换器利用端面微结构产生的在少模激励光纤纤芯横截面上具有不同空间分布的π相位差,从而在少模输出光纤中激励起对应的LP_(mn)模式,结构简单,稳定性好。(The invention discloses a kind of LP based on fiber end face micro-structure 01 ‑LP mn All -fiber mode converter and preparation method thereof, all -fiber mode converter include the single mode input fiber being sequentially connected, few mould excitation optical fiber, few mould output optical fibre, have end face micro-structure in the tail end of few mould excitation optical fiber.Preparation method includes carrying out the processing of core material selective removal to few mould excitation fiber end face by the femtosecond laser after focusing, and core material, which removes the air layer formed later and few mould is not collectively formed by the fibre core of laser ablation, motivates fiber end face micro-structure；By single mode input fiber, few mould with end face micro-structure motivates optical fiber, and few mould output optical fibre is successively welded together, and forms all -fiber mode converter.The π phase difference with different spaces distribution on few mould excitation fiber core cross section that optical fibre mode converter provided by the invention is generated using end face micro-structure, to motivate corresponding LP in few mould output optical fibre mn Mode, structure is simple, and stability is good.)

1. a kind of LP based on fiber end face micro-structure₀₁-LP_mnAll -fiber mode converter, which is characterized in that including being sequentially connected Single mode input fiber, few mould excitation optical fiber, few mould output optical fibre, there is the micro- knot in end face in the tail end of few mould excitation optical fiber Structure；

The single mode input fiber is for sending LP₀₁Mode；

Few mould excitation optical fiber is used in LP₀₁Mode transmitted scriptures end face micro-structure when, introduce different spaces distribution π phase Difference, to motivate corresponding LP in few mould output optical fibre_mnMode；

Few mould output optical fibre is used for transmission the LP of excitation_mnMode.

2. all -fiber mode converter according to claim 1, which is characterized in that the end face micro-structure and excitation LP_mnMode corresponds, by processing the common shape of fibre core to form air layer and not be removed to core material selective removal At end face micro-structure.

3. all -fiber mode converter according to claim 1, which is characterized in that the LP₀₁Mode is basic mode, described LP_mnMode is high-order mode.

4. all -fiber mode converter according to claim 1, which is characterized in that the single mode input fiber is single-mode optics Fibre, few mould excitation optical fiber and few mould output optical fibre are same less fundamental mode optical fibre.

5. a kind of few mould with end face micro-structure motivates optical fiber, which is characterized in that including covering and fibre core, fibre core one end end face Air layer is formed and end face micro-structure that the fibre core that is not removed is collectively formed by processing to core material selective removal.

6. a kind of preparation method based on few mould excitation optical fiber described in claim 5 characterized by comprising

The processing of core material selective removal is carried out to few mould excitation fiber end face by the femtosecond laser after focusing, core material is gone Except the air layer formed later and few mould is not collectively formed by the fibre core of laser ablation and motivates fiber end face micro-structure.

7. preparation method according to claim 6, which is characterized in that the selective removal processing includes that will remove coating Few mould excitation optical fiber after layer is cut, and smooth fiber end face and fixation are obtained；Femtosecond laser focuses on few mould and swashs It encourages in the fibre core of fiber end face, selective material is carried out in the fibre core and removes the few mould excitation to be formed with end face micro-structure Optical fiber.

8. a kind of preparation method based on the described in any item all -fiber mode converters of Claims 1-4, which is characterized in that Include:

The processing of core material selective removal is carried out to few mould excitation fiber end face by the femtosecond laser after focusing, core material is gone Except the air layer formed later and few mould is not collectively formed by the fibre core of laser ablation and motivates fiber end face micro-structure；

By single mode input fiber, few mould with end face micro-structure motivates optical fiber, and few mould output optical fibre is successively welded together, shape Help optical fibre mode converter.

9. preparation method according to claim 8, which is characterized in that the selective removal processing includes that will remove coating Few mould excitation optical fiber after layer is cut, and smooth fiber end face and fixation are obtained；Femtosecond laser focuses on few mould and swashs It encourages in the fibre core of fiber end face, selective material is carried out in the fibre core and removes to form fiber end face micro-structure.

10. preparation method according to claim 8, which is characterized in that few mould excitation light with end face micro-structure Fine and few mould output optical fibre is same less fundamental mode optical fibre.

Technical field

The invention belongs to fiber optic communication fields, more particularly, to a kind of LP based on fiber end face micro-structure₀₁-LP_mn All -fiber mode converter and preparation method thereof.

Background technique

With the fast development of the technologies such as the 5G communication technology, big data, Internet of Things, exponentially type increases data communication service It is long, its non-linear aromatic limit is gradually approached by the message capacity of carrier of single mode optical fiber, existing standard single-mode fiber is logical There is capacity crisis in the near future in letter system.In order to cope with upcoming capacity crisis, employs new technology and realize optical fiber Message capacity is obviously improved, it appears particularly important.Mode division multiplexing technology, using the different higher order eigenmode formula conducts in optical fiber The different data flow of independent transmission channel parallel transmission, so that the message capacity in single fibre core be promoted, this technology is obtained The communications field is widely paid close attention to and is studied.It is transmitted using higher order eigenmode formula, with regard to inevitable requirement in multimode fibre or few mould Higher order mode is effectively motivated and transmitted in optical fiber, this is just needed the basic mode (LP transmitted in optical fiber₀₁Mode) it is converted into height Rank mode, it is therefore desirable to use mode converter.

The mode conversion method being currently used in mode division multiplexing system has transverse method, i.e., based on the free space of phase disk Optical mode converter technology is drawn by the transverse height of control phase disk different zones in the lateral position of optical signal transmission Enter controlled phase jump, efficient LP may be implemented₀₁Mode is to LP_mnThe conversion of mode.But this mode converter designs is multiple Miscellaneous, mode excitation loss height, relative volume are huge sensitive to extraneous ambient vibration, accordingly, it is difficult to stable for extended periods of time sex work.

Secondly, there are also longitudinal methods, i.e., periodically disturbance is introduced in the direction of optical signal transmission, periodically disturb meeting So that the basic mode LP in optical fiber₀₁Mode and higher order mode couple, so that basic mode is converted into high-order mode.But this mode Switching device bandwidth is smaller, often only several nm, is unsatisfactory for the requirement of communication system broadband communication.

Summary of the invention

In view of the drawbacks of the prior art, the purpose of the present invention is to provide a kind of LP based on fiber end face micro-structure₀₁- LP_mnAll -fiber mode converter and preparation method thereof, it is intended to solve existing LP₀₁-LP_mnStructure is complicated for mode converter, stability The problem of difference.

To achieve the above object, it is an aspect of this invention to provide that providing a kind of LP based on fiber end face micro-structure₀₁- LP_mnAll -fiber mode converter, including single mode input fiber, the few mould excitation optical fiber, few mould output optical fibre being sequentially connected, few Mould motivates the tail end of optical fiber to have end face micro-structure；

Single mode input fiber is for sending LP₀₁Mode；

Few mould excitation optical fiber is used in LP₀₁Mode transmitted scriptures end face micro-structure when, introduce different spaces distribution π phase Difference, to motivate corresponding LP in few mould output optical fibre_mnMode；

Few mould output optical fibre is used for transmission the LP of excitation_mnMode.

Further, the LP of end face micro-structure and excitation_mnMode corresponds, by adding to core material selective removal The end face micro-structure that work formation air layer and the fibre core not being removed are collectively formed.

Further, LP₀₁Mode is basic mode, the LP_mnMode is high-order mode.

Further, single mode input fiber is single mode optical fiber, and few mould excitation optical fiber and few mould output optical fibre are same few Mode fiber.

It is another aspect of this invention to provide that providing a kind of few mould excitation optical fiber of end face micro-structure, including covering and fibre Core, fibre core one end end face are collectively formed by processing the fibre core to form air layer and not be removed to core material selective removal End face micro-structure.I.e. fibre core is made of the core structure and normal core structure of femtosecond laser removal at fibre core, wherein not The core region fiber core refractive index N that stimulated light influences_coThere are refractive indices n=for structure after being removed with core material (N_coIt -1) is, λ/2 d=(N by the depth d of control removal material_co- 1), wherein λ is the wavelength of the light transmitted in fibre core.When When the depth of control removal material is the odd-multiple of above-mentioned formula value, the light for being transferred through end face micro-structure is transmitted in fibre core Light will generate the phase difference of π.By motivating optical fiber end face fiber core to introduce the micro- knot in end face with different cross direction profiles in few mould Structure can obtain the full fiber type phase-plate of different higher order modes.

Another aspect according to the invention provides a kind of preparation of above-mentioned few mould excitation optical fiber with end face micro-structure Method, including carrying out the processing of core material selective removal, fibre core to few mould excitation fiber end face by the femtosecond laser after focusing The air layer and few mould excitation fiber end face micro-structure is not collectively formed by the fibre core of laser ablation that material removal is formed later.

Further, selective removal processing includes cutting few mould excitation optical fiber after removal coat, Obtain smooth fiber end face and fixation；Femtosecond laser focuses in the fibre core of few mould excitation fiber end face, carries out in fibre core Selective material removes the few mould excitation optical fiber to be formed with end face micro-structure.

Another aspect according to the invention provides a kind of preparation method based on above-mentioned all -fiber mode converter, packet It includes:

The processing of core material selective removal, fibre core material are carried out to few mould excitation fiber end face by the femtosecond laser after focusing The air layer and few mould excitation fiber end face micro-structure is not collectively formed by the fibre core of laser ablation that material removal is formed later；

By single mode input fiber, few mould with end face micro-structure motivates optical fiber, few mould output optical fibre successively welding one It rises, forms all -fiber mode converter.

Further, selective removal processing includes cutting few mould excitation optical fiber after removal coat, Obtain smooth fiber end face and fixation；Femtosecond laser focuses in the fibre core of few mould excitation fiber end face, carries out in fibre core Selective material removes to form fiber end face micro-structure.

Further, few mould excitation optical fiber with end face micro-structure and few mould output optical fibre are same less fundamental mode optical fibre.

Mode converter provided by the invention has no requirement to less fundamental mode optical fibre in preparation method, the mode converter There are the end face micro-structures of a laser writing for few mould excitation optical fiber end face fiber core, from the point of view of the cross section of the segment core, It is made of the normal core structure that the end face micro-structure of laser writing and other non-stimulated lights are inscribed.It is managed according to optical path difference When region by, light by possessing different refractivity, different phase delay can be generated, the control different refractivity is passed through The depth in region can introduce controllable phase difference.In few mould excitation fiber end face micro-structure, pass through laser writing Region, core material is removed, which is filled by air, and refractive index becomes 1, is not rolled over by the core region of laser writing Rate is penetrated still to remain unchanged.Therefore when by end face micro-structure, the light by different zones can pass through different the light in optical fiber Light path, by the depth of control removal material, phase difference may be controlled to π between the light in two kinds of regions, that is so substantially The phase-plate of a full fiber type is formd on the end face of few mould excitation optical fiber.By the shape for changing fiber end face micro-structure And depth, the full fiber type phase-plate of different higher order modes can be obtained, to motivate in few mould output optical fibre specific High-order LP_mnMode.

LP provided by the present invention based on fiber end face micro-structure₀₁-LP_mnAll -fiber mode converter is motivated in few mould Controllable phase change is laterally introduced on the end face of optical fiber transmission, to realize the LP in any less fundamental mode optical fibre₀₁Mode and LP_mn Any efficient conversion of mode carries out special designing and drawing without to optical fiber, has wide applicability.

Contemplated above technical scheme through the invention can obtain following compared with prior art

The utility model has the advantages that

1, optical fibre mode converter provided by the invention has not on fiber core cross section using what end face micro-structure generated The π phase difference of isospace distribution, realizes LP₀₁Mould and higher order mode LP_mnBetween conversion, do not need to increase additional device, In The phase-plate of full fiber type is formed on the end face of few mould excitation optical fiber, stability is more preferable；

2, the optical fiber used by optical fibre mode converter provided by the invention with end face micro-structure is commonly to lack mould light Fibre is process by femtosecond laser, is carried out special designing and drawing, simple process and low cost without to optical fiber, is easy to batch Production；

3, mode converter provided by the invention is full fiber type mode converter, is matched, is disobeyed based on modal phase Rely Mode Coupling, realizes basic mode LP₀₁With high-order mode LP_mnConversion, therefore mode transfer zone is roomy.

Detailed description of the invention

Fig. 1 is the structural schematic diagram of the full fiber type mode converter provided by the invention based on end face micro-structure；

Fig. 2 is realization basic mode LP provided in an embodiment of the present invention₀₁It is transformed into LP_mnThe knot of fiber end face required for mode Structure schematic diagram；

Fig. 3 is all -fiber mode converter (LP that the embodiment of the present invention 1 provides₀₁-LP₁₁) mode conversion efficiency with Femtosecond laser removes depth of material variation relation；

Fig. 4 is all -fiber mode converter (LP that the embodiment of the present invention 2 provides₀₁-LP₂₁) mode conversion efficiency with Femtosecond laser removes depth of material variation relation；

Fig. 5 is all -fiber mode converter (LP that the embodiment of the present invention 3 provides₀₁-LP₀₂) mode conversion efficiency with Femtosecond laser removes depth of material variation relation；

Fig. 6 is the preparation method of all -fiber mode converter provided in an embodiment of the present invention based on fiber end face micro-structure The structural schematic diagram of the inscription system of use；

Specific embodiment

In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below Not constituting conflict each other can be combined with each other.

As shown in Figure 1, the present invention provides a kind of LP based on fiber end face micro-structure₀₁-LP_mnThe conversion of all -fiber mode Device, including for sending LP₀₁The lacking with end face micro-structure of the single mode input fiber 111 of mode, implementation pattern conversion function Mould excitation optical fiber 112, the LP for being used for transmission excitation_mnFew mould output optical fibre 113 of mode, to achieve the purpose that mode is converted.Base Mould LP₀₁Among from single mode input fiber low-loss transmission into few mould excitation optical fiber with end face micro-structure, being transferred through has When few mould of end face micro-structure motivates fiber end face, since the refractive index by region is different, then the optical path difference passed through is not yet Together, so that phase difference can be caused, and then motivate corresponding higher order mode in few mould output optical fibre 113.

Specifically, the LP of end face micro-structure and excitation_mnMode corresponds, by processing to core material selective removal The end face micro-structure that formation air layer and the fibre core not being removed are collectively formed.

Specifically, LP₀₁Mode is basic mode, the LP_mnMode is high-order mode.

Specifically, single mode input fiber is single mode optical fiber, and few mould excitation optical fiber and few mould output optical fibre are same few mould Optical fiber.

The present invention also provides a kind of few moulds of end face micro-structure to motivate optical fiber, including covering and fibre core, fibre core one end end Face to form air layer and end face micro-structure that the fibre core that is not removed is collectively formed by processing to core material selective removal.

The preparation method for few mould excitation optical fiber that the present invention also provides above-mentioned with end face micro-structure, including by focusing after Femtosecond laser to few mould excitation fiber end face carry out the processing of core material selective removal, core material removal after formed It air layer and few mould is not collectively formed by the fibre core of laser ablation motivates fiber end face micro-structure.

Specifically, selective removal processing includes cutting few mould excitation optical fiber after removal coat, is obtained Obtain smooth fiber end face and fixation；Femtosecond laser focuses in the fibre core of few mould excitation fiber end face, is selected in fibre core Selecting property material removes the few mould excitation optical fiber to be formed with end face micro-structure.

It is the few mould with end face micro-structure for all -fiber mode converter that the embodiment of the present invention 1 to 3 provides shown in Fig. 2 The end view of optical fiber is motivated, including realizes LP₀₁Mode is to LP₁₁Mode, LP₀₁Mode is to LP₂₁Mode, LP₀₁Mode is to LP₀₂ Few mould with end face micro-structure of mode motivates fiber end face micro-structure schematic diagram.In figure, the expression of black region 210 is removed The core region fallen, after core material is removed, script core material position is replaced by air, refractive index 1, such fibre core In light when by the air fibre core adjacent with its, since there are refringences for the two, pass through the light of the two parts Different light paths can be undergone, and then generates phase difference, by the shape and depth in control removal core material region, can control The phase difference for undergoing the light in two regions is π.By being motivated in optical fiber end face fiber core structure in few mould, selective removal fibre core Material can motivate fiber end face to form any high-order LP in few mould_mnMode all -fiber phase-plate structure, and then exporting few mould Optical fiber underexcitation is motivated to play corresponding high-order LP_mnMode.

Further, on the basis of the removal material cross-section of Fig. 2 determines, to LP₀₁Mould is to LP₁₁Mode, LP₀₁Mode To LP₂₁Mode, LP₀₁Mode is to LP₀₂Mode conversion has carried out theoretical validation.

Shown in Fig. 3 is LP₀₁Mode is to LP₁₁The degree of conversion of mode and the relationship of removal depth of material, the few mould used Optical fiber parameter are as follows: the refractive index of covering and fibre core is respectively 1.444 and 1.45, and diameter is respectively 125 microns and 8 microns, fibre core A length of 1.55 microns of the light wave of middle transmission.As shown in figure 3, remove depth of material reach particular value when, such as 1.75 microns or LP at 5.25 microns, in few mould output optical fibre₁₁Mode will be got up by complete excitation.Similarly, as shown in Figure 4, Figure 5, it uses Less fundamental mode optical fibre parameter are as follows: the refractive index of covering and fibre core is respectively 1.444 and 1.45, and diameter is respectively that 125 microns and 16 are micro- Meter, a length of 1.55 microns of light wave transmitted in fibre core.In the case where removal depth of material reaches certain, in few mould output optical fibre LP₂₁And LP₀₂Mode will also be got up by complete excitation.It will be appreciated that above-mentioned selected optical fiber parameter is only to illustrate the present invention Example does not limit the parameter of optical fiber.

As shown in fig. 6, the embodiment of the invention also provides a kind of, all -fiber mode based on fiber end face micro-structure is converted The production method of device, applied to above-mentioned all -fiber mode converter, which comprises

After few mould excitation optical fiber is stripped coat, is cut with cutter and obtain smooth end face, be fixed on three-dimensional tune It saves on platform.Femtosecond laser is focused on fiber end face, the movement of the power and optical fiber of laser is controlled, completes going for material It removes, selective material is carried out in fibre core and removes to form fiber end face micro-structure, by single mode input fiber, there is end face micro-structure Few mould motivate optical fiber, few mould output optical fibre is successively welded together, and forms all -fiber mode converter.

As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include Within protection scope of the present invention.