CN100585438C - A highly nonlinear single-polarization single-mode photonic crystal fiber - Google Patents
A highly nonlinear single-polarization single-mode photonic crystal fiber Download PDFInfo
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- CN100585438C CN100585438C CN200810225319A CN200810225319A CN100585438C CN 100585438 C CN100585438 C CN 100585438C CN 200810225319 A CN200810225319 A CN 200810225319A CN 200810225319 A CN200810225319 A CN 200810225319A CN 100585438 C CN100585438 C CN 100585438C
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Abstract
一种高非线性的单偏振单模光子晶体光纤，横断面包括纤芯和包层。包层为与普通光子晶体光纤一致的由相同结构空气孔(2)均匀分布形成的外围区域。纤芯由位于光纤端面中心的基底材料(1)和四个排列紧密、互不交叠、呈矩形分布的大椭圆率空气孔(3)共同构成。本发明通过细微调整空气孔(3)的中心间距可以调节基模两个偏振模式的截止特性，使其中一个偏振模式在应用的波段内截止，实现大带宽的单偏振传输。同时空气孔(3)抑制了高阶模的产生，在保证光纤单模传输特性不变的前提下允许包层使用更大空气填充率，降低了模场面积和限制损耗。本发明解决了现有光子晶体光纤技术中，高非线性、低限制损耗与宽带单偏振单模特性三者无法兼顾的问题。
A highly nonlinear single-polarization single-mode photonic crystal fiber, the cross-section includes a core and a cladding. The cladding is the peripheral area formed by uniform distribution of air holes (2) with the same structure as the common photonic crystal fiber. The fiber core is composed of a base material (1) located at the center of the optical fiber end face and four air holes (3) with large ellipticity that are closely arranged, do not overlap each other, and are distributed in a rectangular shape. The present invention can adjust the cut-off characteristics of the two polarization modes of the fundamental mode by finely adjusting the distance between the centers of the air holes (3), so that one of the polarization modes can be cut off in the applied wave band, thereby realizing single-polarization transmission with large bandwidth. At the same time, the air hole (3) suppresses the generation of high-order modes, allowing the cladding to use a larger air filling rate under the premise of ensuring that the single-mode transmission characteristics of the optical fiber remain unchanged, reducing the mode field area and limiting loss. The invention solves the problem that high nonlinearity, low confinement loss and broadband single-polarization single-mode characteristic cannot be balanced in the existing photonic crystal fiber technology.
Description
Affiliated technical field
The present invention relates to a kind of photonic crystal waveguide structure, be specifically related to a kind of high non-linear single polarization single-mould photonic crystal fiber.
Background technology
Photonic crystal fiber is called porous optical fiber or microstructured optical fibers again.On fiber end face, regularly arranged many sizes are prolonged axial elongation at the airport of wavelength magnitude in base material, at airport of the center of optical fiber disappearance, replace solid optical fiber base material, perhaps insert the core that refractive index is higher than the other materials formation leaded light of base material, and the peripheral air hole is evenly distributed formation covering in base material, light field is limited at the center high-refractive-index regions substantially, this type optical fiber also can be thought by the total internal reflection principle leaded light, therefore is called the full-internal reflection type photonic crystal fiber again.By regulating covering airport size, the size of pitch of holes size, central entity, the refractive index of central entity can make photonic crystal fiber have flexile birefringence, non-linear and dispersion characteristics.Wherein nonlinear characteristic is main relevant with the nonlinear refractive index of effective mode field area of light field and optical fiber base material.It is generally acknowledged that covering airport dutycycle is big more, covering is strong more to the constraint ability of light field, and effective mould field mode field area of light field is more little, and the nonlinear fiber coefficient is big more.
Existing a large amount of studies have shown that, the refractive index difference of two basic polarization modes of high double-refraction photon crystal fiber is bigger, therefore can the limitation loss of the polarization mode that wherein refractive index is lower be raise by further optimization cladding structure be cut off until this pattern, thereby be implemented in the single-polarization single-mode transmission in certain wavelength coverage, such single polarization single-mode fiber has boundless application prospect in optical fiber telecommunications system and optical fiber sensing system.
But, when a basic mode polarization mode being cut off by the design cladding structure, also cause the declining to a great extent of ability of photonic crystal fiber local light, thereby caused another basic mode polarization mode that is not cut off to have bigger effective mode field area and bigger limitation loss usually.Big mode field area can reduce the nonlinear effect of optical fiber, is widely used under some traditional high power applications conditions.But along with being the development of the emerging smooth industry of representative with new technologies such as full light signal processing, the application of high non-linearity single polarization single-mode fiber is expanded day by day, becomes the focus that new technology is paid close attention to.This has proposed a new difficult problem just for traditional single polarization single-mould photonic crystal fiber design.On the other hand, the limitation loss that basic mode is bigger in traditional single polarization single-mode fiber has also limited the transmission range and the bandwidth of its effective single-polarization single-mode, makes the broadband single-polarization single-mode transmission be difficult to realize.
The angle of the present invention from obtaining single polarization characteristic and high non-linearity simultaneously and being convenient to processing and manufacturing proposed a kind of novel four photonic crystal fibers of arranging the big ellipticity airport of tight rectangular distribution that use in the core district.The high non-linear single polarization single-mould photonic crystal fiber that the present invention proposes, thoroughly solved traditional on the basis of high birefringence by when optimizing cladding structure and realize that single polarization single-mould photonic crystal fiber is being realized the single-polarization single-mode characteristic, can't take into account little mode field area and the low contradiction that limits loss, can in very wide spectral range, realize single polarization transmission easily and have the higher non-linearity coefficient, have broad application prospects at aspects such as optical fiber telecommunications system and sensory field of optic fibre.
Summary of the invention
Technical matters
The technical problem to be solved in the present invention is after four big ellipticity airports replace the center airport closely with the arrangement of fibre core place, spacing by the described airport of trickle adjustment, realization is to the adjusting of basic mode cut-off characteristics, finally in certain wavelength coverage, realize having only a polarization mode to end, another polarization mode still can transmit, thereby obtains to support the photonic crystal fiber of single-polarization single-mode transmission.
The objective of the invention is: solve the difficulty that single-polarization single-mode transport property and little mode field area and low restriction loss characteristic can't be taken into account simultaneously in the present asymmetric single polarization single-mould photonic crystal fiber of cladding structure, a kind of high non-linear single polarization single-mould photonic crystal fiber of simple in structure and easy making is provided.
Technical scheme
Ultimate principle of the present invention is: for realizing high non-linearity (little mode field area), photonic crystal fiber utilizes the covering of its periodic structure, and light field is focused on end centre of optic fibre's zone transmission.The dutycycle of cladding structure airport is big more, and is strong more to the constraint of light field, and the effective mode field area and the limitation loss of optical fiber are low more.Simultaneously, use compact arranged big ellipticity airport to form new inner cladding, reduced the mean refractive index in core district on the one hand, suppressed higher order mode, make unimodular property under the big air filling fraction situation of surrounding layer, still keep in core region; On the other hand, utilize the shape asymmetry of the oval airport of inner cladding, under the very little situation of center distance, make that the spacing of airport outer rim is relatively large on the short-axis direction, thereby the mould field that makes basic mode prolong the polarization state of short-axis direction distribution is cut off at the shorter wavelength place, and the mould field that prolongs the polarization state of direction of principal axis distribution still can be transmitted, the final ultra broadband single-polarization single-mode transmission that realizes covering communication band.Than the normal optical photonic crystal fiber, the present invention utilizes four big ellipticity airports of closely arranging to replace the big airport of absence of heart in the normal optical photonic crystal fiber.By the space distribution of described four airports of trickle adjustment, can realize meticulous adjusting to the cut-off characteristics of basic mode.Because the asymmetry of elliptical shape itself, under the certain situation of center distance, the spacing of elliptical aperture outer rim on its major and minor axis direction is also different.When ellipticity was big, the outer rim spacing on the ellipse short shaft direction was more much bigger than outer rim spacing on the long axis direction.In this case, even center distance is less, but owing to airport outer rim spacing on the short-axis direction is relatively large, the polarization mode that distributes along the transverse direction in the basic mode no longer ends, and another vertical with it polarization mode then still ends.So under certain structural condition, described photonic crystal fiber can provide the transmission of single-polarization single-mode in big wavelength coverage.Thereby core district inner cladding has also reduced the transmission that the mean refractive index in core district has suppressed higher order mode on the other hand, and then making the fibre cladding structure can use bigger air dutycycle and unimodular property still can be kept, this can reduce limitation loss and mode field area effectively.
A kind of high non-linear single polarization single-mould photonic crystal fiber that the present invention proposes, the transversal section of optical fiber comprises fibre core and covering.Described covering is consistent with the normal optical photonic crystal fiber, for surrounding the outer peripheral areas that is uniform-distribution with the same structure airport of fibre core, described airport is periodic arrangement in the optical fiber base material, be of a size of wavelength magnitude, and every three adjacent airport unit constitute an equilateral triangle.The airport diameter and the OC ratio of cladding structure are not more than 0.76, to realize covering the single mode transport characteristic of communication band.Described fibre core is made of the big ellipticity airport that the tight permutation inter of the optical fiber base material that is positioned at the end centre of optic fibre position and four rectangular distributions does not overlap, the long axis direction of described oval airport must be parallel with the length of its rectangular distribution or wide direction, its major diameter is not more than OC 0.45 times of covering airport, and the minor axis diameter is not less than 300 nanometers and propagates to avoid light field to concentrate in the airport.The ratio of long axis to short axis of described big ellipticity airport is slight in 2, minimum center distance on its short-axis direction is not less than OC 0.45 times of covering airport, center distance on its minor axis and long axis direction all is not more than OC 0.5 times of covering airport, to guarantee that the polarization mode that basic mode prolongs the elliptical aperture long axis direction in the central area of fiber end face is supported, another vertical polarization mode is cut off simultaneously.
Beneficial effect
The beneficial effect of photonic crystal fiber of the present invention is mainly reflected in: under the help of core region inner cladding, the periodicity cladding structure of symmetry can use higher air filling fraction, thereby light field is strapped in core region well, by the further constraint of inner cladding, can obtain little mode field area and low restriction loss to the mould field in addition.Core region is only used four large-sized relatively airports, when realizing the transmission of ultra broadband list polarization and suppressing higher order mode, has taken into account the convenience of actual fabrication, thereby has finally obtained the ultra broadband single polarization single-mould photonic crystal fiber of feasible high non-linearity.Have make simple, be convenient to realize that single polarization characteristic, nonlinear characteristic and loss characteristic excellent characteristics simultaneously can be used for realizing the ultra broadband single polarization single-mode fiber and the related device thereof of high non-linearity.
Description of drawings
Fig. 1 is the cross sectional representation of one embodiment of the invention, wherein has: the airport 2 in optical fiber base material 1, the covering; The rectangular oval airport 3 of closely arranging in fibre core place;
Fig. 2 is the mould field pattern of the photonic crystal fiber of Fig. 1 example at the single-polarization single-mode at 1.55 mum wavelength places;
Fig. 3 is the key property figure of the photonic crystal fiber of Fig. 1 example, comprises dispersion curve and limitation loss characteristic.
Embodiment
Embodiment:
With reference to accompanying drawing 1～3, a kind of photonic crystal fiber that uses the big ellipticity airport of four arrangement rectangular distributions closely in core region, end face structure as shown in Figure 1, the base material 1 of optical fiber is quartzy, 1.55 μ m place refractive index is 1.4457, airport 2 is evenly distributed in base material 1 according to the equilateral triangle rule that normal optical photonic crystal fiber well-known in the art adopts usually in the covering, the diameter of each airport 2 is d=0.76 Λ, and wherein Λ=2.2 μ m are the center distance of adjacent vacant pore.The little airport xsect of the rectangular distribution of core region is oval, and its major axis is a=0.45 Λ, and minor axis is b=0.2 Λ, and center distance is Λ on the elliptical aperture vertical direction
1=0.5 Λ, center distance is Λ on the horizontal direction
2=0.5 Λ.Utilize and cooperate the full vector finite element method analysis of complete matching layer to get, described photonic crystal fiber in the mould field distribution at 1.55 mum wavelength places as shown in Figure 2, this moment, x polarization mode and other higher order modes of basic mode all ended, and the effective refractive index of illustrated basic mode y polarization mode is 1.322548-4.465161 * 10
-12I.The limitation loss of the described fiber mode of Ji Suaning is 0.1dB/km thus, and mode field area is 6 μ m
2Nonlinear refractive index (2.6x10 according to base material 1
-20m
2/ W), the nonlinear factor that can further calculate described photonic crystal fiber is 18W
-1Km
-1The photonic crystal fiber of said structure in the chromatic dispersion at different wave length place and limitation loss characteristic thereof as shown in Figure 3.Under the help of inner cladding, the x polarization mode of basic mode ends in 0.6 mum wavelength place, and the y polarization mode of second order mode ends in 1.1 mum wavelength places.Therefore when wavelength during greater than 1.1 μ m, described photonic crystal fiber supports single-polarization single-mode to transmit.In long wavelength's direction, the single-polarization single-mode transmission mainly is subject to the increase of limitation loss.In the present embodiment, in 1.1 μ m-1.62 mum wavelength scopes, limitation loss can be applied to multiple fields such as optical communication, sensing all less than 0.24dB/km.This moment, the single-polarization single-mode bandwidth of described photonic crystal fiber was 520 nanometers (1.1 μ m～1.62 μ m), had covered whole communication band commonly used.
Claims (7)
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| CN200810225319A CN100585438C (en) | 2008-10-30 | 2008-10-30 | A highly nonlinear single-polarization single-mode photonic crystal fiber |
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| CN200810225319A CN100585438C (en) | 2008-10-30 | 2008-10-30 | A highly nonlinear single-polarization single-mode photonic crystal fiber |
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| CN100585438C true CN100585438C (en) | 2010-01-27 |
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Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101832793A (en) * | 2010-04-26 | 2010-09-15 | 北京航空航天大学 | Photonic crystal optical fiber sensor based on polarization interference |
| CN102778723B (en) * | 2011-05-13 | 2013-12-18 | 聊城大学 | Single-mode single-polarization photonic crystal fiber with elliptical air hole array with gradually-reduced minor axis |
| CN102914299A (en) * | 2012-09-24 | 2013-02-06 | 北京航空航天大学 | Fiber-optic gyroscope based on single-mode single polarized photon crystal optical fiber |
| CN103472527B (en) * | 2013-09-27 | 2015-08-05 | 天津理工大学 | A kind of High-birefringence low-confinement-lossphotonic photonic crystal fiber |
| CN103454720A (en) * | 2013-09-27 | 2013-12-18 | 天津理工大学 | Photonic crystal fiber with high birefringence characteristic |
| CN103913801B (en) * | 2014-03-05 | 2016-04-06 | 合肥工业大学 | A kind of New-type photon crystal optical fiber |
| CN105954830A (en) * | 2016-01-28 | 2016-09-21 | 合肥工业大学 | Broadband single polarization single-mode photonic crystal fiber |
| CN106199826B (en) * | 2016-08-03 | 2019-04-23 | 清华大学 | Polarization-Maintaining Ring Core Fiber |
| CN106707405B (en) * | 2017-01-26 | 2019-04-26 | 燕山大学 | High Birefringence Large Core Diameter Porous Core Photonic Crystal Fiber |
| CN107329204B (en) * | 2017-08-21 | 2020-03-06 | 北京航空航天大学 | A single-mode transmission method based on the mode cut-off characteristic in the photonic band gap |
| CN108318966B (en) * | 2018-04-13 | 2019-08-20 | 南京航空航天大学 | A photonic crystal fiber with high birefringence and high Brillouin gain |
| CN108333670A (en) * | 2018-05-04 | 2018-07-27 | 中国电子科技集团公司第四十六研究所 | A kind of active microstructured optical fibers of aperiodicity coarse pitch single mode |
| WO2020056821A1 (en) * | 2018-09-20 | 2020-03-26 | 通鼎互联信息股份有限公司 | Gradient photonic crystal polarization maintaining fiber |
| CN110426780A (en) * | 2019-07-31 | 2019-11-08 | 中国船舶重工集团公司第七0七研究所 | A kind of monomode single-polarization photonic crystal fiber of small sircle hole star-arrangement |
| CN111129923B (en) * | 2019-12-20 | 2022-02-25 | 江苏师范大学 | Single-frequency and single-polarization optical fiber distributed feedback laser |
| CN111323869A (en) * | 2020-03-05 | 2020-06-23 | 华南师范大学 | A microstructure optical fiber for co-transmission of optical information and optical energy |
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Non-Patent Citations (1)
| Title |
|---|
| 有源光纤脉冲复制器系统误差分析. 杨义，郑铮，李铮，陈宇晓.北京航空航天大学学报，第34卷第5期. 2008 * |
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