阅读说明：本技术 一种用于光纤与各向异性波导的偏振无关耦合的装置 (Device for polarization-independent coupling of optical fiber and anisotropic waveguide ) 是由 飒米穆萨 刘永 于 2020-05-26 设计创作，主要内容包括：本发明涉及光纤技术领域,具体公开了一种用于光纤与各向异性波导的偏振无关耦合的装置,其中,包括：光纤、模斑转换器和波导,所述模斑转换器的一端与所述光纤连接,所述模斑转换器的另一端与所述波导连接,所述光纤与所述模斑转换器连接的一端为楔形端头,所述模斑转换器的一端的水平方向模场直径与所述楔形端头的水平方向模场直径相匹配,所述模斑转换器的一端的垂直方向模场直径与所述楔形端头的垂直方向模场直径相匹配。本发明提供的用于光纤与各向异性波导的偏振无关耦合的装置能够实现匹配各向异性波导中TE和TM模式的模场直径,其中的楔形端头可以通过自动打磨处理来获得,因此不需要显著增加产品成本即可实现。(The invention relates to the technical field of optical fibers, and particularly discloses a device for polarization-independent coupling of an optical fiber and an anisotropic waveguide, wherein the device comprises: the optical fiber module comprises an optical fiber, a spot size converter and a waveguide, wherein one end of the spot size converter is connected with the optical fiber, the other end of the spot size converter is connected with the waveguide, one end of the optical fiber, which is connected with the spot size converter, is a wedge-shaped end, the diameter of a horizontal mode field at one end of the spot size converter is matched with the diameter of a horizontal mode field at the wedge-shaped end, and the diameter of a vertical mode field at one end of the spot size converter is matched with the diameter of a vertical mode field at the wedge-shaped end. The device for polarization-independent coupling of the optical fiber and the anisotropic waveguide can realize matching of mode field diameters of TE and TM modes in the anisotropic waveguide, and the wedge-shaped end can be obtained through automatic polishing treatment, so that the device can be realized without remarkably increasing the product cost.)

1. An apparatus for polarization independent coupling of an optical fiber to an anisotropic waveguide, comprising: the optical fiber module comprises an optical fiber, a spot size converter and a waveguide, wherein one end of the spot size converter is connected with the optical fiber, the other end of the spot size converter is connected with the waveguide, one end of the optical fiber, which is connected with the spot size converter, is a wedge-shaped end, the diameter of a horizontal mode field at one end of the spot size converter is matched with the diameter of a horizontal mode field at the wedge-shaped end, and the diameter of a vertical mode field at one end of the spot size converter is matched with the diameter of a vertical mode field at the wedge-shaped end.

2. The apparatus of claim 1, wherein the wedge angle of the wedge tip is adjusted in a range of 10 ° -80 °.

3. The apparatus of claim 1, wherein the waveguide comprises an anisotropic waveguide.

4. The apparatus of claim 1, wherein the optical fiber comprises a standard single mode fiber.

Technical Field

The invention relates to the technical field of optical fibers, in particular to a device for polarization-independent coupling of an optical fiber and an anisotropic waveguide.

Background

Currently, to achieve effective end-face coupling between an optical fiber and a planar waveguide, the Mode Field Diameters (MFDs) of the two must be matched. Standard single mode fibers have a large mode field diameter, typically about 9 μm, and are isotropic, i.e. the TE and TM polarization modes have almost the same MFD, whereas the MFD of planar waveguides is typically less than 2 μm. To match the MFD of the fiber to the planar waveguide, a spot-size converter (SSC), a waveguide that is tapered in both the vertical and horizontal directions, is typically introduced on the waveguide chip.

In recent years, researchers have designed and implemented SSCs on waveguides of various materials and geometries. Fig. 1 shows the SSC structure of a silicon-on-insulator (SOI) material waveguide, in which the SOI waveguide is first tapered in the horizontal direction so that its width gradually decreases until the transmission condition of the optical waveguide mode is no longer satisfied, and then a section of polymer waveguide with a large cross-sectional size is used to collect the light wave radiated from the end of the SOI waveguide, which is easily MFD-matched with a lensed fiber, thereby achieving efficient coupling of the waveguide and the fiber. However, typical planar waveguides are anisotropic, resulting in unequal MFDs for TE and TM modes. The SSC can only ensure that the fiber is matched with the TE or TM mode of the planar waveguide, and cannot simultaneously match the TE and TM modes of the planar waveguide. If the optical signal in the optical fiber has an indeterminate polarization state, the efficiency of coupling into the anisotropic waveguide will be low, i.e. the polarization dependent loss will be large.

And the prior art approach to the above problem is to use Polarization Maintaining (PM) fiber. Polarization maintaining optical fibers can only transmit optical signals of one specific polarization direction, and thus can be efficiently coupled into a planar waveguide. However, this method has the disadvantage that the price of the polarization maintaining fiber is higher than that of the standard single mode fiber, thereby increasing the cost of the product. In addition, in some applications (such as wavelength division multiplexing), the polarization state of the optical signal is uncertain, and the polarization maintaining fiber cannot be used as a field.

Disclosure of Invention

The invention provides a device for polarization-independent coupling of an optical fiber and an anisotropic waveguide, which solves the problem that the polarization-independent coupling of the optical fiber and the anisotropic waveguide cannot be realized at low cost in the related technology.

As an aspect of the present invention, there is provided an apparatus for polarization independent coupling of an optical fiber to an anisotropic waveguide, comprising: the optical fiber module comprises an optical fiber, a spot size converter and a waveguide, wherein one end of the spot size converter is connected with the optical fiber, the other end of the spot size converter is connected with the waveguide, one end of the optical fiber, which is connected with the spot size converter, is a wedge-shaped end, the diameter of a horizontal mode field at one end of the spot size converter is matched with the diameter of a horizontal mode field at the wedge-shaped end, and the diameter of a vertical mode field at one end of the spot size converter is matched with the diameter of a vertical mode field at the wedge-shaped end.

Further, the wedge angle of the wedge-shaped end head is adjusted within the range of 10-80 degrees.

Further, the waveguide comprises an anisotropic waveguide.

Further, the optical fiber comprises a standard single mode optical fiber.

According to the device for polarization-independent coupling of the optical fiber and the anisotropic waveguide, the end, in contact with the mode spot converter, of the optical fiber is processed into the wedge-shaped end, so that the symmetry of the optical fiber can be broken, the geometric structures of TE and TM modes in transmission are not the same, and the mode field constraint conditions are different, so that the TE and TM modes have different effective refractive indexes (propagation constants) and mode field distributions, and the MFD matching with the TE and TM modes in the anisotropic waveguide can be realized. In addition, the device for polarization-independent coupling of the optical fiber and the anisotropic waveguide, provided by the embodiment of the invention, has the advantages that the wedge-shaped end can be obtained through automatic polishing treatment, so that the device can be realized without significantly increasing the product cost.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

Fig. 1 is a schematic diagram of the SSC structure of a prior art SOI waveguide.

FIG. 2 is a side view of the coupling between a wedge-tipped optical fiber and a waveguide provided by the present invention.

FIG. 3 is a top view of the coupling between a wedge-terminated optical fiber and a waveguide provided by the present invention.

Fig. 4 is a schematic view of the wedge angle of the wedge-shaped end provided by the invention.

FIG. 5 is a schematic longitudinal section of an optical fiber with a wedge-shaped tip according to the present invention.

FIG. 6 is a schematic cross-sectional view of a fiber optic waveguide and a wedge tip provided in accordance with the present invention.

FIG. 7 is a schematic diagram of the mode field distribution of TE and TM modes in the fiber waveguide provided by the present invention.

FIG. 8 is a schematic diagram of the mode field distribution of TE and TM modes in the wedge tip provided by the present invention.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In this embodiment, an apparatus for polarization independent coupling of an optical fiber to an anisotropic waveguide is provided, and fig. 2 and 3 are a side view and a top view, respectively, of an apparatus for polarization independent coupling of an optical fiber to an anisotropic waveguide provided according to an embodiment of the present invention, as shown in fig. 2 and 3, including: the optical fiber module comprises an optical fiber, a spot size converter and a waveguide, wherein one end of the spot size converter is connected with the optical fiber, the other end of the spot size converter is connected with the waveguide, one end of the optical fiber, which is connected with the spot size converter, is a wedge-shaped end, and the horizontal mode field diameter MFD of one end of the spot size converter_xAnd the horizontal mode field diameter MFD of the wedge-shaped end_xMatching, the perpendicular mode field diameter MFD of one end of the spot size converter_yMode field diameter MFD in the direction perpendicular to the wedge-shaped end_yAnd (4) matching.

According to the device for polarization-independent coupling of the optical fiber and the anisotropic waveguide, provided by the embodiment of the invention, one end of the optical fiber, which is in contact with the mode spot converter, is processed into a wedge-shaped end, so that the symmetry of the optical fiber can be broken, the geometric structures of TE and TM modes in transmission are not the same, and the mode field constraint conditions are different, so that the TE and TM modes have different effective refractive indexes (propagation constants) and mode field distributions, and the MFD matching with the TE and TM modes in the anisotropic waveguide can be finally realized. In addition, the device for polarization-independent coupling of the optical fiber and the anisotropic waveguide, provided by the embodiment of the invention, has the advantages that the wedge-shaped end can be obtained through automatic polishing treatment, so that the device can be realized without significantly increasing the product cost.

As shown in fig. 4, a wedge-shaped tip can be made by polishing the fiber tip at an angle relative to the optical axis. Wherein a change in the wedge angle may cause a change in the dimension of the wedge-shaped planar waveguide in the vertical direction. This wedge breaks the symmetry of the fiber, resulting in the MFD of the TE and TM modes no longer being the same. Fig. 5-8 show waveguide cross-sections and mode field distributions for typical standard optical fibers and tapered fiber ends. The left cross-sectional view of fig. 6 corresponds to the cross-section at the left dotted line position of fig. 5, and the right cross-sectional view of fig. 6 corresponds to the cross-section at the right dotted line position of fig. 5. Fig. 7 is a schematic diagram of the mode field distribution of a standard single mode fiber, and fig. 8 is a schematic diagram of the mode field distribution of a wedge tip. As shown in fig. 5 and 6, a standard optical fiber has a circular geometry, and light waves in TE and TM modes will pass through the same geometry when traveling in the fiber, and will therefore have the same effective refractive index and mode field distribution. Whereas a tapered end is a planar waveguide in which the TE and TM modes travel through the same geometry and are subject to different mode field constraints, resulting in TE and TM modes having different effective refractive indices (propagation constants) and mode field distributions. The size of the planar waveguide in the vertical direction can be changed by adjusting the wedge angle, and the mode field distribution in the wedge can be changed accordingly. In summary, the MFDs of the TE and TM modes can be controlled and adjusted by changing the angle of the wedge tip to match the MFDs of the TE and TM modes in the anisotropic waveguide. As shown in fig. 8, the mode field distributions of TE and TM modes in the tapered fiber stub are different and can be adjusted by changing the wedge angle.

By adjusting the wedge angle and the width and thickness of the SSC, efficient coupling of TE and TM modes can be achieved simultaneously.

Preferably, the wedge angle of the wedge-shaped end is adjusted within the range of 10-80 degrees, and the specific size depends on the material and the geometric structure of the SSC. The coupling loss after optimizing the parameters can be as low as 0.5 dB.

Preferably, the waveguide comprises an anisotropic waveguide.

Preferably, the optical fibre comprises a standard single mode fibre.

Therefore, the device for polarization-independent coupling of the optical fiber and the anisotropic waveguide provided by the embodiment of the invention can realize efficient coupling of TE and TM modes in the anisotropic waveguide at the same time, and the cost is not increased remarkably.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.