阅读说明：本技术 一种高模式数量且弱耦合的少模光纤 (High-mode-number and weak-coupling few-mode optical fiber ) 是由 彭楚宇 喻煌 郭浩 曲斌 郭君 刘旋 于 2021-08-27 设计创作，主要内容包括：本申请涉及一种高模式数量且弱耦合的少模光纤,其包括由内到外依次设置的椭圆芯层、椭圆环形芯层、椭圆环形下陷包层和外包层；在所述椭圆环形下陷包层上设有两个空气孔,两个所述空气孔关于所述椭圆环形芯层的短轴轴对称；在所述椭圆芯层、椭圆环形芯层和椭圆环形下陷包层中,三者的中心大致重合,三者的长轴位于同一直线上,三者的短轴位于同一直线上；所述椭圆芯层与所述椭圆环形芯层的折射率剖面的形状均为水平直线形；所述椭圆芯层的折射率小于所述椭圆环形芯层的折射率。本申请能够解决相关技术中光纤可用的模式数量较少,远不能满足长距离大容量扩容的需求的问题。(The application relates to a few-mode optical fiber with high mode number and weak coupling, which comprises an elliptical core layer, an elliptical annular sunken cladding layer and an outer cladding layer which are sequentially arranged from inside to outside; two air holes are arranged on the elliptical annular sunken cladding layer, and the two air holes are axially symmetrical about the short axis of the elliptical annular core layer; in the elliptical core layer, the elliptical annular core layer and the elliptical annular sunken cladding layer, the centers of the three layers are approximately superposed, the long axes of the three layers are positioned on the same straight line, and the short axes of the three layers are positioned on the same straight line; the shapes of the refractive index profiles of the elliptical core layer and the elliptical annular core layer are both horizontal straight lines; the refractive index of the elliptical core layer is smaller than that of the elliptical ring-shaped core layer. The method and the device can solve the problems that in the related technology, the number of available modes of the optical fiber is small, and the requirement for long-distance large-capacity expansion cannot be met.)

1. A high mode number and weakly coupled few-mode fiber, comprising: the core comprises an elliptical core layer (1), an elliptical annular core layer (2), an elliptical annular sunken cladding layer (3) and an outer cladding layer (4) which are arranged from inside to outside in sequence;

two air holes (5) are formed in the elliptical annular sunken cladding (3), and the two air holes (5) are axially symmetrical with respect to the short axis of the elliptical annular core layer (2);

in the elliptical core layer (1), the elliptical annular core layer (2) and the elliptical annular sunken cladding layer (3), the centers of the three layers are approximately superposed, the long axes of the three layers are positioned on the same straight line, and the short axes of the three layers are positioned on the same straight line;

the shapes of the refractive index sections of the elliptical core layer (1) and the elliptical annular core layer (2) are both horizontal straight lines;

the refractive index of the elliptical core layer (1) is smaller than that of the elliptical annular core layer (2).

2. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the elliptical core layer (1) and the elliptical annular core layer (2) are both doped with germanium, the elliptical annular sunken cladding layer (3) is doped with fluorine, and the outer cladding layer (4) is made of pure quartz.

3. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the two air holes (5) are positioned on the straight line of the long axis of the elliptical annular core layer (2).

4. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the ellipticity value range of the elliptical core layer (1), the elliptical annular core layer (2) and the elliptical annular sunken cladding layer (3) is 0.60-0.70.

5. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the major axis radius of the elliptical core layer (1) ranges from 1.5 to 4.0 microns, the major axis radius of the elliptical annular core layer (2) ranges from 5.0 to 8.5 microns, and the major axis radius of the elliptical annular sunken cladding layer (3) ranges from 12.0 to 17.0 microns.

6. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the radius of the air holes (5) ranges from 1.1 to 1.6 mu m.

7. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the distance between the air holes (5) and the outer edge of the elliptical annular core layer (2) ranges from 5 to 30 micrometers.

8. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the relative refractive index difference between the elliptical core layer (1) and the pure quartz ranges from 0.80% to 1.65%, and the relative refractive index difference between the elliptical annular core layer (2) and the pure quartz ranges from 1.60% to 2.20%.

9. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: the value range of the relative refractive index difference between the elliptical annular sunken cladding (3) and the pure quartz is-0.30% -0.65%.

10. The high mode number and weakly coupled few-mode fiber of claim 1, wherein: when the working wavelength is 1550nm, the maximum number of transmission modes available for the few-mode optical fiber is 16 modes, and the transmission loss of optical signals of all modes at 1550nm is not more than 0.25 dB/km.

Technical Field

The application relates to the technical field of space division multiplexing optical fiber communication, in particular to a few-mode optical fiber with high mode number and weak coupling.

Background

In the context of networks where multimedia and data applications are expanding rapidly and the demand for backbone network bandwidth is driving to grow rapidly, internet traffic is growing at a rate of about 100 times per 10 years. Through a series of technical innovations such as improvement of optical fiber transmission performance, erbium-doped optical fiber amplifiers, wavelength division multiplexing technology, high-spectrum-efficiency code modulation, space division multiplexing, coherent detection, digital signal processing and the like, the transmission capacity of the conventional single-mode single-core optical fiber is exponentially increased in the last decades, the bandwidth utilization rate of the single-mode optical fiber is close to the nonlinear shannon limit, and the bandwidth requirement which is continuously increased in the future is difficult to support. Multi-core optical fiber and few-mode optical fiber transmission technologies using fiber cores and modes as new spatial multiplexing dimensions are widely considered as the mainstream trend of next-generation optical fiber communication, and a new development direction is provided for further increasing the communication capacity of optical fibers.

In a spatial multiplexing transmission system, different signals can be transmitted simultaneously over multiple spatial paths. From the perspective of space division multiplexed fibers, there are two ways in which multiple spatial paths can be introduced into the fiber. The first method is to combine a plurality of individual cores into one optical fiber, and a cladding contains a plurality of cores, and the transmission capacity of the optical fiber is multiplied with the number of cores, and the optical fiber is called a multicore fiber. The second approach is to use a number of different modes in the fiber, the transmission capacity of which is multiplied as the number of modes grows, which is called few-mode fiber. The core radius of the few-mode fiber is slightly larger than that of a single-mode fiber, so that the few-mode fiber has a larger effective mode field area and has more advantages in the aspect of nonlinear tolerance. The preparation process and the welding technology of the few-mode optical fiber can directly use the related experience of the single-mode optical fiber, and have natural advantages in compatibility with the single-mode optical fiber, so that the mode division multiplexing system based on the few-mode optical fiber also becomes one of the most interesting research directions at present.

When multiple modes in few-mode optical fiber are transmitted simultaneously, under the combined action of distributed mode crosstalk and intermodal dispersion, a combined multiple-input multiple-output digital signal processing device (MIMO DSP) is required to separate received signals, and the calculation complexity is increased sharply and cannot be realized. For example, 100Gbps dual-polarization Quadrature Phase Shift Keying (QPSK) signals are transmitted for 100km in 10-mode optical fiber with differential mode delay value of 1ps/m, the delay is spread by about thousands of symbols, the complexity of MIMO-DSP between multiple modes is about 6 orders of magnitude higher than that of single-mode transmission, and continues to grow rapidly as the transmission distance and the number of modes increase. Considering the moore's law limit of the scale of the integrated circuit, the algorithm complexity is controlled to be only increased by a plurality of times compared with the existing single-mode transmission, and the method is a key technical bottleneck which needs to be broken through most by the few-mode transmission technology at present. To solve the problem, few-mode optical fiber and weak coupling mode division multiplexing transmission technologies based on mode regulation and control technologies are proposed, and the main idea is to adopt various means to improve the effective refractive index difference among different modes. When the effective refractive index difference between all adjacent modes is greater than 10^-3In time, cross talk between modes can be suppressed to be small enough, so that each mode can be independently detected without MIMO-DSP processing between modes. However, at present, the number of available modes is generally small, the transmission distance is extremely short, and the requirement of long-distance large-capacity expansion cannot be met.

Disclosure of Invention

The embodiment of the application provides a few-mode optical fiber with high mode number and weak coupling, so as to solve the problems that the number of available modes of the optical fiber is small and the requirement of long-distance large-capacity expansion cannot be met in the related technology.

The embodiment of the application provides a few-mode optical fiber with high mode number and weak coupling, which comprises an elliptical core layer, an elliptical annular sunken cladding layer and an outer cladding layer which are sequentially arranged from inside to outside;

two air holes are arranged on the elliptical annular sunken cladding layer, and the two air holes are axially symmetrical about the short axis of the elliptical annular core layer;

in the elliptical core layer, the elliptical annular core layer and the elliptical annular sunken cladding layer, the centers of the three layers are approximately superposed, the long axes of the three layers are positioned on the same straight line, and the short axes of the three layers are positioned on the same straight line;

the shapes of the refractive index profiles of the elliptical core layer and the elliptical annular core layer are both horizontal straight lines;

the refractive index of the elliptical core layer is smaller than that of the elliptical ring-shaped core layer.

In some embodiments, the elliptical core layer and the elliptical ring core layer are doped with germanium, the elliptical ring depressed cladding layer is doped with fluorine, and the outer cladding layer is made of pure quartz.

In some embodiments, two of the air holes are located on a straight line on which a long axis of the elliptical ring-shaped core layer is located.

In some embodiments, the ellipticity of the elliptical core layer, the elliptical annular core layer, and the elliptical annular depressed cladding layer ranges from 0.60 to 0.70.

In some embodiments, the major axis radius of the elliptical core layer ranges from 1.5 μm to 4.0 μm, the major axis radius of the elliptical ring-shaped core layer ranges from 5.0 μm to 8.5 μm, and the major axis radius of the elliptical ring-shaped sunken cladding layer ranges from 12.0 μm to 17.0 μm.

In some embodiments, the radius of the air holes ranges from 1.1 μm to 1.6 μm.

In some embodiments, the distance between the air holes and the outer edge of the elliptical annular core layer ranges from 5 μm to 30 μm.

In some embodiments, the relative refractive index difference between the elliptical core layer and the pure quartz ranges from 0.80% to 1.65%, and the relative refractive index difference between the elliptical annular core layer and the pure quartz ranges from 1.60% to 2.20%.

In some embodiments, the relative refractive index difference between the elliptical ring depressed cladding and pure quartz is in the range of-0.30% to-0.65%.

In some embodiments, the maximum number of transmission modes available for the few-mode fiber is 16 modes at an operating wavelength of 1550nm, and the transmission loss of optical signals of all modes at 1550nm is not greater than 0.25 dB/km.

The beneficial effect that technical scheme that this application provided brought includes:

the embodiment of the application provides a solution for an air hole-assisted high-mode-number and weakly-coupled few-mode optical fiber, on one hand, a circular fiber core is changed into an elliptical fiber core, the purpose is to break the symmetry of an optical fiber structure by adopting an elliptical fiber core design so as to introduce a birefringence effect, break the internal degeneracy of an LP mode, increase the propagation constant difference between two polarization modes and obviously improve the available mode number of the few-mode optical fiber; on the other hand, the air holes are added in the area outside the fiber core, namely the elliptical annular depressed cladding, so that the mode field distribution of the LP mode is changed, the effective refractive index distribution of each mode tends to be uniformly distributed, the minimum effective refractive index difference is obviously improved, the mode coupling among different modes is reduced, and the weak coupling characteristic of the modes is ensured.

The few-mode optical fiber of the embodiment has a simple profile structure, the relative refractive index difference between the core layer and the pure quartz material is relatively low, the preparation difficulty of the weak-coupling few-mode optical fiber is reduced, and the effective refractive index between the modes is ensured to be more than 10^-3On the premise of the (1), the maximum number of modes can reach 16 modes, and the spatial integration dimension density and the transmission capacity are greatly improved by increasing the mode multiplexing number.

The application does not need special material coating, and can meet the requirements of high-speed large-capacity optical fiber transmission systems in future.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic cross-sectional structural diagram of a weakly coupled few-mode optical fiber with a high number of modes according to an embodiment of the present disclosure;

FIG. 2 is a schematic cross-sectional view of the refractive index of a high-mode-number and weakly-coupled few-mode fiber according to an embodiment of the present invention.

In the figure: 1. an elliptical core layer; 2. an elliptical ring-shaped core layer; 3. an elliptical ring-shaped depressed cladding; 4. an outer cladding; 5. and (4) air holes.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a few-mode optical fiber with high mode number and weak coupling, which can solve the problems that the number of available modes of the optical fiber is small and the requirement of long-distance large-capacity expansion cannot be met in the related technology.

Referring to fig. 1 and fig. 2, the low-mode optical fiber with high mode number and weak coupling provided in the embodiment of the present application includes an elliptical core layer 1, an elliptical annular core layer 2, an elliptical annular depressed cladding layer 3, and an outer cladding layer 4, which are sequentially disposed from inside to outside, two air holes 5 are disposed on the elliptical annular depressed cladding layer 3, and the two air holes 5 are axisymmetric with respect to a short axis of the elliptical annular core layer 2, where the elliptical core layer 1 is located at a central position of the low-mode optical fiber and is a main region for optical signal transmission, the elliptical annular core layer 2 is an annular region located outside the elliptical core layer 1 and can be used to regulate mode distribution of the low-mode optical fiber and is a main region for optical signal transmission, and the elliptical annular depressed cladding layer 3 is an annular region located outside the elliptical annular core layer 2 and can be used to regulate mode distribution of the low-mode optical fiber and improve bending resistance of the low-mode optical fiber, the outer side of the elliptical ring-shaped sunken cladding 3 is provided with an outer cladding 4 of the few-mode optical fiber, and the air holes 5 are through holes and can introduce air.

As shown in fig. 1, in the elliptical core layer 1, the elliptical annular core layer 2, and the elliptical annular depressed cladding layer 3, the centers of the three are approximately coincident, the major axes of the three are located on the same straight line, the minor axes of the three are located on the same straight line, the refractive index distributions of the elliptical core layer 1 and the elliptical annular core layer 2 are in step-like distribution, specifically, as shown in fig. 2, the refractive index profiles of the elliptical core layer 1 and the elliptical annular core layer 2 are both in a horizontal linear shape, and the refractive index of the elliptical core layer 1 is smaller than the refractive index of the elliptical annular core layer 2.

According to the solution of the air hole assisted high-mode-number and weak-coupling few-mode optical fiber, on one hand, a circular fiber core is changed into an elliptical fiber core, and the purpose is to break the symmetry of an optical fiber structure by adopting an elliptical fiber core design so as to introduce a birefringence effect, break the internal degeneracy of an LP mode, increase the propagation constant difference between two polarization modes and obviously improve the available mode number of the few-mode optical fiber; on the other hand, the air holes are added in the area outside the fiber core, namely the elliptical annular depressed cladding, so that the mode field distribution of the LP mode is changed, the effective refractive index distribution of each mode tends to be uniformly distributed, the minimum effective refractive index difference is obviously improved, the mode coupling among different modes is reduced, and the weak coupling characteristic of the modes is ensured.

In addition, the sunken cladding is also designed to be elliptical, and the advantage is that, on one hand, after deposition of each layer is completed during manufacturing, the sunken cladding changes along with the deposition to form an elliptical shape in the subsequent process of adjusting the shape of the core region, which is natural, so that the shape change process of the sunken cladding is not formed by specially adding processes, and relatively speaking, a mode regulation step is reduced, and on the other hand, the sunken cladding is designed to be elliptical or can further introduce a birefringence effect, so that the propagation constant difference between polarization modes is increased, and the abnormal mode coupling plays a certain role.

The few-mode optical fiber of the embodiment has a simple profile structure, the relative refractive index difference between the core layer and the pure quartz material is relatively low, the preparation difficulty of the weak-coupling few-mode optical fiber is reduced, and the effective refractive index between the modes is ensured to be more than 10^-3Under the premise that the maximum number of modes can reach 16 modes, the modes are increasedThe multiplexing quantity greatly improves the spatial integration dimension density and the transmission capacity. Meanwhile, special materials are not needed to be coated, and the requirements of high-speed and high-capacity optical fiber transmission systems in future can be met.

When the working wavelength is 1550nm, the maximum transmission mode number of the few-mode optical fiber is 16 modes, and the transmission loss of optical signals of all modes at 1550nm is not more than 0.25 dB/km.

In some preferred embodiments, the elliptical core layer 1 and the elliptical annular core layer 2 are both doped with germanium, and the relative refractive index difference is high due to the doping of germanium, so that the few-mode optical fiber allows a smaller cut-off wavelength, and meanwhile, in order to ensure good bending performance, the elliptical annular depressed cladding layer 3 doped with fluorine is designed on the outer periphery of the elliptical annular core layer 2, so that the bending resistance of the few-mode optical fiber is realized, and the outer cladding layer 4 is made of pure quartz.

The air holes are introduced into the few-mode optical fiber with the elliptical core, because the few-mode optical fiber with the air hole auxiliary type elliptical core has larger birefringence effect and wider adjustment range of the mode refractive index than the few-mode optical fiber with the conventional elliptical core. The closer the air holes are to the core region, the larger the aperture of the air holes is, the more obvious the birefringence effect is introduced, so that the mode field distribution of the mode is easier to adjust; the farther the air holes are from the core, the smaller the air hole diameter, and the weaker the birefringence effect it introduces. However, strong birefringence effects, while beneficial for increasing the refractive index difference between the modes, tend to cut off the higher order modes or modes of a certain polarization direction, resulting in a reduced number of modes in the fiber. Therefore, the distance between the air holes and the core area and the core diameter need to be reasonably adjusted, and the compatibility of high mode quantity and low mode coupling is guaranteed. Based on this, in some preferred embodiments, the two air holes 5 are located on a straight line where the major axis of the elliptical ring-shaped core layer 2 is located, and the distance between the air holes 5 and the outer edge of the elliptical ring-shaped core layer 2 is in a range of 5 to 30 μm.

Referring to fig. 1, in some preferred embodiments, the ellipticity of the elliptical core layer 1, the elliptical annular core layer 2, and the elliptical annular depressed cladding layer 3 ranges from 0.60 to 0.70, wherein ellipticity is the ratio of the major axis radius to the minor axis radiusValue, major axis radius R of elliptical core layer 1_1XThe value range is 1.5-4.0 mu m, and the major axis radius R of the elliptical annular core layer 2_2XThe value range is 5.0-8.5 mu m, and the major axis radius R of the elliptical annular sunken cladding 3_3XThe value range is 12.0-17.0 mu m, the radius of the outer cladding layer 4 is usually 62.5 mu m, and the radius of the air hole 5 is 1.1-1.6 mu m.

The application calculates the relative refractive index difference delta by adopting the following formula_i：

Wherein i is 1, 2, 3, n₀Is the refractive index of pure quartz, when i is 1, n₁Is the refractive index, Δ, of the elliptical core layer 1₁The relative refractive index difference between the elliptical core layer 1 and the pure quartz; when i is 2, n₂Is the refractive index, Delta, of the elliptical annular core layer 2₂The relative refractive index difference between the elliptical annular core layer 2 and the pure quartz is obtained; when i is 3, n₃Is the refractive index, Delta, of the elliptical ring-shaped depressed cladding 3₃The relative refractive index difference of the elliptical ring-shaped depressed cladding 3 and pure quartz.

Referring to FIG. 2, the relative refractive index difference Δ between the elliptical core layer 1 and pure quartz₁The value range of the elliptical ring-shaped core layer 2 is 0.80 to 1.65 percent, and the relative refractive index difference delta between the elliptical ring-shaped core layer 2 and the pure quartz is delta₂The value range of the elliptical ring-shaped sunken cladding 3 is 1.60-2.20%, and the relative refractive index difference delta between the elliptical ring-shaped sunken cladding 3 and the pure quartz is delta₃The value range of the (B) is-0.30 to-0.65 percent.

The present application will be described in further detail with reference to specific examples.

The first embodiment is as follows:

the few-mode optical fiber is designed by adopting step index distribution, the elliptical core layer 1 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical core layer 1 and pure quartz is delta₁It was 1.05%. The elliptical annular core layer 2 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical annular core layer and pure quartz₂It was 1.98%. The elliptical ring-shaped sunken cladding 3 is made of fluorine-doped quartz material and is folded relative to pure quartzDifference in refractive index Δ₃Is-0.56%. The outer cladding 4 is made of pure quartz. Major axis radius R of elliptical core layer 1_1X3.2 μm, an ellipticity of 0.64, and a major axis radius R of the elliptical ring-shaped core layer 2_2X6.0 μm, the major axis radius R of the elliptical ring-shaped depressed cladding 3_3XIt was 13.0. mu.m. The radius of the air holes 5 is 1.2 μm and the radius of the outer cladding 4 is 62.5 μm. The few-mode core region of the few-mode optical fiber of the embodiment supports ten modes.

Example two:

the few-mode optical fiber is designed by adopting step index distribution, the elliptical core layer 1 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical core layer 1 and pure quartz is delta₁Is 0.95%. The elliptical annular core layer 2 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical annular core layer and pure quartz₂The content was 2.20%. The elliptical ring-shaped depressed cladding 3 is made of fluorine-doped quartz material, and has a relative refractive index difference delta from that of pure quartz₃Is-0.62%. The outer cladding 4 is made of pure quartz. Major axis radius R of elliptical core layer 1_1X3.6 μm, an ellipticity of 0.62, and a major axis radius R of the elliptical ring-shaped core layer 2_2X7.8 μm, major axis radius R of the elliptical ring-shaped depressed cladding 3_3XIt was 15.0. mu.m. The radius of the air holes 5 is 1.5 μm and the radius of the outer cladding 4 is 62.5 μm. In the present embodiment, fourteen modes are supported in the few-mode core region of the few-mode fiber.

Example three:

the few-mode optical fiber is designed by adopting step index distribution, the elliptical core layer 1 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical core layer 1 and pure quartz is delta₁Is 0.95%. The elliptical annular core layer 2 is made of germanium-doped quartz material, and the relative refractive index difference delta between the elliptical annular core layer and pure quartz₂The content was 2.08%. The elliptical ring-shaped depressed cladding 3 is made of fluorine-doped quartz material, and has a relative refractive index difference delta from that of pure quartz₃Is-0.60%. The outer cladding 4 is made of pure quartz. Major axis radius R of elliptical core layer 1_1X4.0 μm, an ellipticity of 0.62, and a major axis radius R of the elliptical ring-shaped core layer 2_2X8.5 μm, the major axis radius R of the elliptical ring-shaped depressed cladding 3_3X16.5 μm. The radius of the air holes 5 is 1.5 μm and the radius of the outer cladding 4 is 62.5 μm. The few-mode optical fiber of the embodiment has internal support in the few-mode core regionSixteen modes.

According to the three embodiments, the minimum effective refractive index difference among different modes can be effectively adjusted by adjusting the radius, the refractive index and the ellipticity of the ring core and the position and the radius of the air hole. Effective refractive index > 10 between guaranteed modes^-3On the premise of the (1), the maximum number of modes can reach 16 modes, and the transmission capacity of the optical fiber is greatly improved by increasing the multiplexing number of the modes.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.