A fiber end face DOE mode demultiplexing coupler and method of use

Abstract

The application discloses a kind of optical fiber end surface DOE mode demultiplexing coupler and use method, it is related to demultiplexing device and coupling device technical field, wherein, optical fiber end surface DOE mode demultiplexing coupler includes: few-mode fiber;Fiber beam expander is connected with the few-mode fiber, for amplifying the light spot in the few-mode fiber;Optical fiber end surface diffraction optical element DOE structure is set on the fiber beam expander, for different mode transmitted by few-mode fiber is demultiplexed, and different mode is focused to different spatial position by controlling phase distribution;Output waveguide is correspondingly arranged at the focusing position of the optical fiber end surface DOE structure, to realize coupling.The application can demultiplex and couple into output waveguide in the multiplexed mode in few-mode fiber.

Description

Technical Field

[0001] This invention relates to the field of optical access network technology, specifically to an optical fiber end-face DOE (Diffractive Optical Elements) mode demultiplexing coupler and its usage method. Background Technology

[0002] In recent years, the demand for communication network capacity has been increasing, and multiplexing technologies that can improve transmission capacity have received widespread attention. Spatial dimension, as the last reusable dimension besides polarization, frequency, amplitude, phase, and time, has attracted significant interest due to its potential to overcome the limitation of single-mode fiber communication capacity approaching the nonlinear Shannon limit.

[0003] Modular division multiplexing (MDM) is the key to spatial division multiplexing (SDM). It can utilize different spatial modes of light as independent channels to transmit information, which can multiply the system capacity and spectral efficiency.

[0004] In mode division multiplexing (MDD) systems, demultiplexers are crucial components for achieving MMD. Currently, mode demultiplexers mainly include those based on planar asymmetric parallel waveguides, multimode interference, silicon-based Y-type connection waveguides, and multi-plane optical converters. How to demultiplex the multiplexed modes in a few-mode fiber and couple them to the output waveguide is a pressing problem that needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the first aspect of this invention provides an optical fiber end-face DOE mode demultiplexing coupler that can demultiplex multiplexed modes in a few-mode fiber and couple them to an output waveguide.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A fiber optic end-face DOE mode demultiplexing coupler, comprising:

[0008] few-mode fiber;

[0009] An optical fiber expander, which is connected to the few-mode fiber, is used to amplify the light spot in the few-mode fiber;

[0010] The fiber end face diffractive optical element (DOE) structure is disposed on the fiber expander and is used to demultiplex different modes transmitted in the few-mode fiber and focus different modes to different spatial positions by controlling the phase distribution.

[0011] The output waveguide is positioned at the focal point of the DOE structure on the fiber end face to achieve coupling.

[0012] In some embodiments, the fiber endface DOE structure employs a phase distribution using a focusing lens:

[0013]

[0014] To make the incident light at a distance of f from the fiber end face DOE structure n Cross-sectional position (x) n ,y n Focus on the area.

[0015] In some embodiments, the few-mode fiber is used for transmitting LP (Liquid Crystal Fiber). 01 Patterns and LPs 11 Two-mode and few-mode optical fibers.

[0016] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0017] The first, second, and third portions are evenly distributed, and the phase distributions of the first, second, and third portions are as follows: and To make:

[0018] LP 01 After the pattern passes through the second part, it focuses at a focal length f2 and a cross-sectional position (x2, y2), and makes LP 01 The pattern undergoes destructive interference after passing through the first and third parts;

[0019] LP 11 After passing through the first and third parts, the pattern focuses at a focal length f1 and a cross-sectional position (x1, y1), and makes LP 11 The pattern undergoes destructive interference after passing through the second part.

[0020] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0021] The second part has an adjustable width, and the first and third parts are located on both sides of the second part and remain symmetrical.

[0022] A second aspect of the present invention provides a method for using the above-mentioned fiber end-face DOE mode demultiplexing coupler, which can demultiplex the multiplexed modes in a few-mode fiber and couple them to the output waveguide.

[0023] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0024] A method for using the above-mentioned fiber optic end-face DOE mode demultiplexing coupler, the method comprising the following steps:

[0025] The light spot in the few-mode fiber is amplified using an optical fiber expander;

[0026] The different modes transmitted in a few-mode fiber are demultiplexed by using the fiber end-face diffraction optical element (DOE) structure, and the different modes are focused to different spatial positions by controlling the phase distribution.

[0027] Coupling is achieved using the output waveguide located at the focal position of the DOE structure on the fiber end face.

[0028] In some embodiments, the fiber endface DOE structure employs a phase distribution using a focusing lens:

[0029]

[0030] To make the incident light at a distance of f from the fiber end face DOE structure n Cross-sectional position (x) n ,y n Focus on the area.

[0031] In some embodiments, the few-mode fiber is used for transmitting LP (Liquid Crystal Fiber). 01 Patterns and LPs 11 Two-mode and few-mode optical fibers.

[0032] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0033] The first, second, and third portions are evenly distributed, and the phase distributions of the first, second, and third portions are as follows: and To make:

[0034] LP 01 After the pattern passes through the second part, it focuses at a focal length f2 and a cross-sectional position (x2, y2), and makes LP 01 The pattern undergoes destructive interference after passing through the first and third parts;

[0035] LP 11 After passing through the first and third parts, the pattern focuses at a focal length f1 and a cross-sectional position (x1, y1), and makes LP 11 The pattern undergoes destructive interference after passing through the second part.

[0036] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0037] The second part has an adjustable width, and the first and third parts are located on both sides of the second part and remain symmetrical.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] The fiber optic end-face DOE mode demultiplexing coupler of this invention includes: a few-mode fiber, a fiber expander, a fiber end-face DOE structure, and an output waveguide. The fiber expander is connected to the few-mode fiber and is used to amplify the light spot in the few-mode fiber. The fiber end-face diffractive optical element (DOE) structure is disposed on the fiber expander and is used to demultiplex different modes transmitted in the few-mode fiber, and to focus different modes to different spatial positions by controlling the phase distribution. The output waveguide is correspondingly disposed at the focusing position of the fiber end-face DOE structure to achieve coupling. This achieves the purpose of demultiplexing the multiplexed modes in the few-mode fiber and coupling them to the output waveguide. Attached Figure Description

[0040] Figure 1 This is a structural block diagram of the DOE mode demultiplexing coupler at the fiber end face in an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the phase distribution of the DOE structure at the fiber end face in an embodiment of the present invention;

[0042] Figure 3 This is a flowchart illustrating the usage method of the DOE mode demultiplexing coupler at the fiber optic end face in an embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] See Figure 1 As shown, an embodiment of the present invention provides a fiber end-face DOE mode demultiplexing coupler, including a few-mode fiber, a fiber expander, a fiber end-face diffractive optical element (DOE) structure, and an output waveguide.

[0045] Among them, few-mode fibers come in different types, capable of transmitting different numbers of modes. For example, a two-mode few-mode fiber can be used to transmit LP (Low Mode) signals. 01 Patterns and LPs 11 model.

[0046] An optical fiber expander is connected to the few-mode fiber to amplify the light spot in the few-mode fiber. It should be noted that for few-mode fibers, due to their core diameter of approximately 14 micrometers, the area is limited and insufficient to support a fiber end-face DOE structure. Therefore, in this embodiment of the invention, an optical fiber expander is connected to the few-mode fiber. This allows for uniform amplification of the light spot in the few-mode fiber, and the larger end-face area of ​​the optical fiber expander is sufficient to fabricate a fiber end-face DOE structure on it.

[0047] The fiber end face DOE structure is set on the fiber expander to demultiplex different modes of transmission in the few-mode fiber and to focus different modes to different spatial positions by controlling the phase distribution.

[0048] The output waveguide is positioned at the focal point of the DOE structure on the fiber end face to achieve coupling.

[0049] For example, for transmission LP 01 Patterns and LPs 11 Two-mode few-mode fiber, the fiber endface DOE structure can multiplex LP 01 Patterns and LPs 11 The modes are demultiplexed, and then the two modes are focused onto the end faces of two waveguides at different spatial locations to achieve coupling.

[0050] In specific implementations, in some embodiments, the fiber optic end-face DOE structure adopts the phase distribution of a focusing lens:

[0051]

[0052] To make the incident light at a distance of f from the fiber end face DOE structure n Cross-sectional position (x) n ,y n Focus on the area.

[0053] See Figure 2 As shown, the principle of the fiber optic end-face DOE mode demultiplexing coupler in this embodiment of the invention will be explained below with a specific example:

[0054] To transmit LP 01 Patterns and LPs 11 Taking a two-mode few-mode fiber as an example, in order to focus the two modes onto the end faces of two waveguides at different spatial locations, one feasible approach is:

[0055] The phase distribution of the fiber endface DOE structure is configured as follows:

[0056] The first, second, and third parts are uniformly distributed (corresponding to I, II, and III in the figure), and the phase distributions of the first, second, and third parts are as follows: and To make:

[0057] LP 01 After the pattern passes through the second part, it focuses at a focal length f2 and a cross-sectional position (x2, y2), and makes LP 01 The pattern undergoes destructive interference after passing through the first and third parts.

[0058] It is understandable that, because the phase difference between I and III is π, destructive interference will occur, thus LP 01 The pattern cannot focus and couple at (x1, y1, f1).

[0059] LP 11 After passing through the first and third parts, the pattern focuses at a focal length f1 and a cross-sectional position (x1, y1), and makes LP 11 The pattern undergoes destructive interference after passing through the second part.

[0060] It is also understandable that, due to LP 11 The two mode lobes of the mode have a phase difference of π, therefore LP 11 The mode will be focused at (x1, y1, f1) by the actions of I and III, and coupled to the waveguide at that point. However, under the action of II, destructive interference occurs, and the mode cannot be focused at (x2, y2, f2). Thus, mode demultiplexing is achieved based on the above steps.

[0061] Furthermore, for the fiber end face DOE structure, the phase distribution mode obtained in the design is modified by taking the remainder of 2π. By using the refractive index of the DOE material and the parameters of the working wavelength, the height distribution of the fiber end face DOE structure is finally obtained.

[0062] In the above steps, the phase distribution of the fiber endface DOE structure is uniformly divided into three parts. In some embodiments, the width of region II can be adjusted while maintaining symmetry to achieve power distribution in two modes. That is, the phase distribution of the fiber endface DOE structure is configured as follows: a second part with an adjustable region width, and a first and third part located on both sides of the second part and maintaining symmetry.

[0063] It is understood that the position of the output waveguide in the embodiments of the present invention can be flexibly configured within a suitable range, and it is relatively easy to modify. Only the design parameters (x1,y1,f1) and (x2,y2,f2) of the DOE need to be changed.

[0064] It is worth noting that, in addition to the two modes of demultiplexing described in this invention, for demultiplexing of multiple modes, the phase distribution can be reasonably designed according to the symmetry between different modes to achieve demultiplexing between different modes. The specific principle is similar and can be referred to the above two-mode few-mode fiber.

[0065] In summary, the fiber end-face DOE mode demultiplexing coupler of this invention includes: a few-mode fiber, a fiber expander, a fiber end-face DOE structure, and an output waveguide. The fiber expander is connected to the few-mode fiber and is used to amplify the light spot in the few-mode fiber; the fiber end-face diffractive optical element (DOE) structure is disposed on the fiber expander and is used to demultiplex the different modes transmitted in the few-mode fiber, and to focus the different modes to different spatial positions by controlling the phase distribution; the output waveguide is correspondingly disposed at the focusing position of the fiber end-face DOE structure to achieve coupling. This achieves the purpose of demultiplexing the multiplexed modes in the few-mode fiber and coupling them to the output waveguide.

[0066] Meanwhile, see Figure 3 As shown, this embodiment of the invention also provides a method for using the above-mentioned fiber optic end-face DOE mode demultiplexing coupler, the method comprising the following steps:

[0067] S1. Use an optical fiber expander to amplify the light spot in the few-mode optical fiber.

[0068] S2. The different modes transmitted in a few-mode fiber are demultiplexed using the fiber end-face diffraction optical element (DOE) structure, and the different modes are focused to different spatial positions by controlling the phase distribution.

[0069] S3. Coupling is achieved by using the output waveguide located at the focal position of the DOE structure on the fiber end face.

[0070] In some embodiments, the fiber endface DOE structure employs a phase distribution using a focusing lens:

[0071]

[0072] To make the incident light at a distance of f from the fiber end face DOE structure n Cross-sectional position (x) n ,y n Focus on the area.

[0073] In some embodiments, the few-mode fiber is used for transmitting LP (Liquid Crystal Fiber). 01 Patterns and LPs 11 Two-mode and few-mode optical fibers.

[0074] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0075] The first, second, and third portions are evenly distributed, and the phase distributions of the first, second, and third portions are as follows: and To make:

[0076] LP 01 After the pattern passes through the second part, it focuses at a focal length f2 and a cross-sectional position (x2, y2), and makes LP 01 The pattern undergoes destructive interference after passing through the first and third parts;

[0077] LP 11 After passing through the first and third parts, the pattern focuses at a focal length f1 and a cross-sectional position (x1, y1), and makes LP 11 The pattern undergoes destructive interference after passing through the second part.

[0078] In some embodiments, the phase distribution of the fiber endface DOE structure is configured as follows:

[0079] The second part has an adjustable width, and the first and third parts are located on both sides of the second part and remain symmetrical.

[0080] In summary, the method of using the fiber end-face DOE mode demultiplexing coupler of the present invention involves the following steps: amplifying the light spot in the few-mode fiber using a fiber expander; demultiplexing the different modes transmitted in the few-mode fiber using a fiber end-face diffractive optical element (DOE) structure, and focusing the different modes to different spatial positions by controlling the phase distribution; and achieving coupling using an output waveguide correspondingly located at the focusing position of the DOE structure on the fiber end-face. This achieves the purpose of demultiplexing the multiplexed modes in the few-mode fiber and coupling them to the output waveguide.

[0081] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0082] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. The above descriptions are merely specific implementations of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A fiber optic end-face DOE mode demultiplexing coupler, characterized in that, include: few-mode fiber; An optical fiber expander, which is connected to the few-mode fiber, is used to amplify the light spot in the few-mode fiber; The fiber end face (DOE) structure is disposed on the fiber expander and is used to demultiplex different modes of transmission in the few-mode fiber and focus different modes to different spatial positions by controlling the phase distribution. An output waveguide is positioned at the focal point of the DOE structure on the fiber end face to achieve coupling. The phase distribution of the fiber endface DOE structure is configured as follows: The first, second, and third portions are evenly distributed, and the phase distributions of the first, second, and third portions are as follows: , and So that: LP 01 After the pattern passes through the second part, at focal length Cross-sectional position Focusing on the point and making LP 01 The pattern undergoes destructive interference after passing through the first and third parts; LP 11 After the pattern passes through the first and third parts, at the focal length Cross-sectional position Focusing on the point and making LP 11 The pattern undergoes destructive interference after passing through the second part.

2. The fiber optic end-face DOE mode demultiplexing coupler as described in claim 1, characterized in that: The fiber optic DOE structure employs a phase distribution using a focusing lens: To make the incident light at a distance from the fiber end face DOE structure Cross-sectional position Focusing on the area.

3. The fiber optic end-face DOE mode demultiplexing coupler as described in claim 2, characterized in that: The few-mode fiber is used for transmitting LP. 01 Patterns and LPs 11 Two-mode and few-mode optical fibers.

4. The fiber optic end-face DOE mode demultiplexing coupler as described in claim 3, characterized in that: The phase distribution of the fiber endface DOE structure is configured as follows: The second part has an adjustable width, and the first and third parts are located on both sides of the second part and remain symmetrical.

5. A method of using the fiber optic end-face DOE mode demultiplexing coupler as described in claim 1, characterized in that, The method includes the following steps: The light spot in the few-mode fiber is amplified using an optical fiber expander; The different modes of transmission in few-mode fiber are demultiplexed by using the fiber end face DOE structure, and the different modes are focused to different spatial positions by controlling the phase distribution. Coupling is achieved by utilizing the output waveguide located at the focal position of the DOE structure on the fiber end face. Furthermore, the phase distribution of the fiber endface DOE structure is configured as follows: The first, second, and third portions are evenly distributed, and the phase distributions of the first, second, and third portions are as follows: , and So that: LP 01 After the pattern passes through the second part, at focal length Cross-sectional position Focusing on the point and making LP 01 The pattern undergoes destructive interference after passing through the first and third parts; LP 11 After the pattern passes through the first and third parts, at the focal length Cross-sectional position Focusing on the point and making LP 11 The pattern undergoes destructive interference after passing through the second part.

6. The method of use as described in claim 5, characterized in that: The fiber optic DOE structure employs a phase distribution using a focusing lens: To make the incident light at a distance from the fiber end face DOE structure Cross-sectional position Focusing on the area.

7. The method of use as described in claim 5, characterized in that: The few-mode fiber is used for transmitting LP. 01 Patterns and LPs 11 Two-mode and few-mode optical fibers.

8. The method of use as described in claim 7, characterized in that: The phase distribution of the fiber endface DOE structure is configured as follows: The second part has an adjustable width, and the first and third parts are located on both sides of the second part and remain symmetrical.

Images