A fiber combiner device and method of using the same

Abstract

The application belongs to the technical field of space beam combining, and particularly relates to a fiber beam combining device and a use method thereof. The fiber beam combining device comprises a first off-axis parabolic mirror group and a second off-axis parabolic mirror group. The first off-axis parabolic mirror group comprises a plurality of off-axis parabolic mirrors, the focal points of the plurality of off-axis parabolic mirrors are respectively coincident with the cores of corresponding incident optical fibers, and the outgoing light rays of the plurality of incident optical fibers are collimated into parallel light rays. The focal point of the second off-axis parabolic mirror group is coincident with the core of an outgoing optical fiber. The light ray output directions of the plurality of off-axis parabolic mirrors are coincident with the light ray input directions of the second off-axis parabolic mirror group. The fiber beam combining device can realize high coupling efficiency and wide coupling waveband beam combining.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spatial beam combining, and particularly relates to a fiber beam combining device and a method thereof. BACKGROUND

[0002] With the rapid development of optical fiber communication technology, people's requirements for the transmission capacity and distance of optical signals are becoming higher and higher. In optical fiber communication systems, multiple optical signals need to be coupled into an optical fiber for transmission to increase the communication capacity. For example, in a wavelength division multiplexing (WDM) system, different wavelengths of optical signals represent different channels, and through fiber beam combining, these optical signals carrying different information can be combined into one optical fiber, thereby realizing the simultaneous transmission of multiple signals. This is like on a highway, the traffic flow of multiple lanes is combined in a reasonable way to fewer lanes to fully utilize the road resources.

[0003] Long-distance optical fiber transmission also requires fiber beam combining technology. When optical signals are transmitted in an optical fiber for a long distance, loss will occur. In order to compensate for these losses, an optical fiber amplifier can be used. Fiber beam combining technology can effectively combine pump light and signal light, so that the pump light can provide energy amplification for the signal light, thereby extending the transmission distance of the optical signal.

[0004] Therefore, there is an urgent need for a fiber beam combining device to improve the coupling efficiency and cope with a wide coupling wavelength band. SUMMARY

[0005] To solve the above problems, the application discloses a fiber beam combining device, which comprises a first off-axis parabolic mirror group and a second off-axis parabolic mirror group.

[0006] The first off-axis parabolic mirror group comprises a plurality of off-axis parabolic mirrors, and the focal points of the plurality of off-axis parabolic mirrors are respectively coincided with the cores of corresponding incident optical fibers, so as to collimate the outgoing light rays of the plurality of incident optical fibers into parallel light rays.

[0007] The focal point of the second off-axis parabolic mirror group is coincided with the core of the outgoing optical fiber.

[0008] The light output direction of the plurality of off-axis parabolic mirrors is coincided with the light input direction of the second off-axis parabolic mirror group.

[0009] Further, the aperture of the second off-axis parabolic mirror group is larger than the circumscribed circle diameter of the first off-axis parabolic mirror group.

[0010] Further, the core diameter of the outgoing optical fiber should be not less than the core diameter of the incident optical fiber 3.

[0011] Further, the circumscribed circle diameter D 外接 of the first off-axis parabolic mirror group and the core diameter D0 of the outgoing optical fiber are related as follows:

[0012]

[0013] Wherein, H is the distance between the first off-axis parabolic mirror group and the second off-axis parabolic mirror group, d1 is the incident fiber core diameter, and f1 is the focal length of the first off-axis parabolic mirror group.

[0014] Further, the focal length f1 and the aperture D1 of the first off-axis parabolic mirror group 1 and the NA value of the incident fiber satisfy the following relationship:

[0015]

[0016] Wherein, d1 is the incident fiber core diameter.

[0017] Further, the relationship between the core diameter D0 of the outgoing fiber and the core diameter d1 of the incident fiber satisfies:

[0018]

[0019] Wherein, f1 is the focal length of the first off-axis parabolic mirror group, and f2 is the focal length of the second off-axis parabolic mirror group.

[0020] Further, the incident fibers are arranged in a staggered manner.

[0021] Or the incident fibers are arranged in a tower structure.

[0022] Further, the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group and the second off-axis parabolic mirror group are 90° off-axis parabolic mirrors.

[0023] Further, the application also discloses a use method of the optical fiber beam combining device in any of the above embodiments, which specifically comprises the following steps:

[0024] A first flange is mounted at one end of each incident fiber, the relative position of the first flange and the first off-axis parabolic mirror group is adjusted and fixed, so that the focal points of the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group are respectively coincided with the fiber cores of the corresponding incident fibers;

[0025] A second flange is mounted at one end of the outgoing fiber, the relative position of the first flange and the second off-axis parabolic mirror group is adjusted and fixed, so that the focal point of the second off-axis parabolic mirror group is coincided with the fiber core of the outgoing fiber;

[0026] The relative position of the first off-axis parabolic mirror and the second off-axis parabolic mirror group is adjusted and fixed, so that the light output direction of the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group is coincided with the light input direction of the second off-axis parabolic mirror group.

[0027] Further, the multiple incident optical fibers are arranged in staggered or tower structure.

[0028] The present application can realize high coupling efficiency and wide coupling waveband.

[0029] Other features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and claims. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0031] Figure 1 A propagation diagram of meridian light in an optical fiber according to the prior art is shown;

[0032] Figure 2 A propagation diagram of oblique light in an optical fiber according to the prior art is shown;

[0033] Figure 3 A light path diagram of an optical fiber beam combining device according to an embodiment of the present application is shown;

[0034] Figure 4 A transverse sectional view of a first off-axis parabolic mirror group and a second off-axis parabolic mirror group in an optical fiber beam combining device according to an embodiment of the present application is shown.

[0035] In the figure: 1, first off-axis parabolic mirror group; 2, second off-axis parabolic mirror group; 3, incident optical fiber; 4, outgoing optical fiber. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0037] When light propagates in an optical fiber, it can be divided into two cases according to its propagation path, i.e. meridian light and oblique light.

[0038] 1. Propagation of Meridian Fiber in Optical Fiber

[0039] like Figure 1 As shown, the meridional ray refers to the ray passing through the central axis of the optical fiber. Figure 1 Schematic diagram of the propagation of meridional light in a step-index fiber, where n0 is the refractive index of the medium surrounding the fiber, n1 and n2 are the refractive indices of the fiber core and cladding respectively. According to the law of total reflection, the output light must be limited to the incident angle at the interface between the core and cladding in the fiber waveguide. Must be greater than or equal to the critical angle . Then we have:

[0040]

[0041]

[0042] It can also be expressed as

[0043]

[0044] in,

[0045]

[0046] Using the law of refraction

[0047] ,

[0048] Available,

[0049]

[0050] When n0 is air, the maximum incident angle corresponding to the meridional ray is:

[0051]

[0052] It is called the maximum aperture angle of the optical fiber, which reflects the size of the fiber laser energy and determines the numerical aperture NA of the optical fiber in the meridian plane.

[0053] 2. Propagation of oblique light in optical fibers

[0054] Any light ray in an optical fiber that is not transmitted in the meridian plane is called an oblique ray. The oblique ray is neither intersecting nor parallel to the optical axis of the optical fiber. The optical path is a left-handed or right-handed broken line in space, and the distance from the oblique ray to the central axis of the optical fiber is equal.

[0055] According to the principles of geometric optics, the conditions for total reflection of oblique light can be obtained, such as Figure 2 As shown, KQ is the oblique light incident on the step-index optical fiber, and point H on the optical fiber cross section is the projection of the incident point K. The total reflection condition of the oblique light is:

[0056]

[0057] According to the law of refraction of light,

[0058] ,

[0059] The above formula will become:

[0060] The numerical aperture expression of the oblique light is as follows:

[0061]

[0062] Since Therefore, the NA of the oblique light is larger than that of the meridian light.

[0063] Therefore, in the spatial beam combination, in order to couple the light into the optical fiber efficiently, there are two necessary conditions:

[0064] 1. The incident angle of the light meets the requirement of the numerical aperture (NA) of the optical fiber

[0065] 2. At the end plane of the optical fiber, the incident point of the light is in the core of the optical fiber, and the light incident outside the core of the optical fiber cannot enter the optical fiber even if it meets the NA of the optical fiber.

[0066] As shown in Figure 3 and Figure 4 , the embodiment discloses a fiber beam combination device, which comprises a first off-axis parabolic mirror group 1 and a second off-axis parabolic mirror group 2.

[0067] The first off-axis parabolic mirror group 1 comprises a plurality of off-axis parabolic mirrors, the focal points of the plurality of off-axis parabolic mirrors are respectively coincided with the cores of corresponding incident optical fibers 3, and the emergent light of the plurality of incident optical fibers 3 is collimated into parallel light.

[0068] The focal point of the second off-axis parabolic mirror group 2 is coincided with the core of the emergent optical fiber 4.

[0069] The light output direction of the plurality of off-axis parabolic mirrors is coincided with the light input direction of the second off-axis parabolic mirror group 2.

[0070] Specifically, the plurality of incident optical fibers 3 correspond to one of the first off-axis parabolic mirrors in the first off-axis parabolic mirror group 1. The incident optical fiber 3 refers to a small optical fiber that needs to be coupled. The center of the core of the incident optical fiber 3 coincides with the focal point of the corresponding off-axis parabolic mirror. The outgoing light in the incident optical fiber 3 is reflected by the off-axis parabolic mirror and is collimated into a parallel light beam from the original scattered light. The light output direction of the first off-axis parabolic mirror group 1 coincides with the light input direction of the second off-axis parabolic mirror group 2, so that the plurality of parallel light beams coupled by the first off-axis parabolic mirror group 1 are transmitted to the second off-axis parabolic mirror group 2. After the parallel light beams enter the second off-axis parabolic mirror group 2, they converge at the focal point of the second off-axis parabolic mirror group 2. The focal point of the second off-axis parabolic mirror group 2 coincides with the core of the outgoing optical fiber 4, and the beam combining is completed. The outgoing optical fiber 4 refers to the output optical fiber after coupling. Preferably, the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group 1 and the second off-axis parabolic mirror group 2 are 90° off-axis parabolic mirrors.

[0071] Further, in order to make all the outgoing light of the incident optical fiber 3 enter the outgoing optical fiber 4, the aperture of the second off-axis parabolic mirror group 2 is larger than the circumscribed circle diameter of the first off-axis parabolic mirror group 1.

[0072] Specifically, the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group 1 are uniformly arranged. The output directions of all the off-axis parabolic mirrors are located within the input range of the second off-axis parabolic mirror group 2, so as to avoid the outgoing light of the incident optical fiber 3 after being converted into a parallel light beam from entering the second off-axis parabolic mirror group 2, and to avoid the outgoing light of the incident optical fiber 3 from overflowing.

[0073] Further, the circumscribed circle diameter D 外接 The relationship between the circumscribed circle diameter D

[0074]

[0075] Wherein, H is the distance between the first off-axis parabolic mirror group 1 and the second off-axis parabolic mirror group 2, d1 is the core diameter of the incident incident optical fiber 3, and f1 is the focal length of the first off-axis parabolic mirror group 1.

[0076] Specifically, each off-axis parabolic mirror in the first off-axis parabolic mirror group 1 is of the same shape and size. The focal length f1 and the aperture D1 of the first off-axis parabolic mirror group 1 refer to the focal length and the aperture of each off-axis parabolic mirror in the first off-axis parabolic mirror group 1. The circumscribed circle diameter D 外接 refers to the diameter of the circumscribed circle obtained by compactly arranging a plurality of off-axis parabolic mirrors. According to the previous propagation mode of light in the optical fiber, only the circumscribed circle diameter D 外接The relationship between the core diameter D0 of the exit optical fiber 4 meets the above requirements, and the coupled light can completely enter the exit optical fiber 4.

[0077] It can be known from the above relationship that the larger the diameter of the circumscribed circle is, the larger the diameter of the exit optical fiber 4 is, and in actual production, it is necessary to maximize the reduction of the diameter of the exit optical fiber 4 in order to control the cost, and the diameter of the circumscribed circle is reduced. The incident optical fibers 3 are arranged in a staggered manner; or the incident optical fibers 3 are arranged in a tower structure.

[0078] Further, the focal length f1 and the aperture D1 of the first off-axis parabolic mirror group 1 and the NA value of the incident optical fiber 3 meet the following relationship:

[0079]

[0080] Wherein d1 is the core diameter of the incident optical fiber 3.

[0081] Specifically, it can be known from the previous light propagation mode in the optical fiber that only when the focal length and the aperture of the first off-axis parabolic mirror meet the above relationship, the incident angle of the optical fiber can meet the requirement of the numerical aperture NA of the optical fiber.

[0082] Further, the core diameter of the exit optical fiber 4 should be not less than the core diameter of the incident optical fiber 3.

[0083] Specifically, the larger the core diameter of the optical fiber is, the higher the light flux is. The core diameter of the exit optical fiber 4 is greater than the core diameter of the incident optical fiber 3, so that the exit optical fiber 4 after coupling can transmit more light.

[0084] Further, the relationship between the core diameter D0 of the exit optical fiber 4 and the core diameter d1 of the incident optical fiber 3 meets:

[0085]

[0086] Wherein f1 is the focal length of the first off-axis parabolic mirror group 1, and f2 is the focal length of the second off-axis parabolic mirror group 2.

[0087] In another embodiment of the present application, the use method of the optical fiber beam combining device in any of the above embodiments is also disclosed, and the use method specifically includes the following steps:

[0088] A first flange is mounted at one end of each incident optical fiber, the relative position of the first flange and the first off-axis parabolic mirror group is adjusted and fixed, so that the focal points of the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror group respectively coincide with the cores of the corresponding incident optical fibers;

[0089] A second flange is installed at one end of the exit optical fiber, the relative position of the first flange and the second off-axis parabolic mirror set is adjusted and fixed, so that the focal point of the second off-axis parabolic mirror set coincides with the core of the exit optical fiber;

[0090] The relative position of the first off-axis parabolic mirror and the second off-axis parabolic mirror set is adjusted and fixed, so that the light output direction of the plurality of off-axis parabolic mirrors in the first off-axis parabolic mirror set coincides with the light input direction of the second off-axis parabolic mirror set.

[0091] Further, the plurality of incident optical fibers are arranged in an interleaved manner or in a tower structure.

[0092] Although the present application is described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A fiber optic bundle combining device, characterized in that: The optical fiber beam combining device comprises a first off-axis parabolic mirror group (1) and a second off-axis parabolic mirror group (2); The first off-axis parabolic mirror group (1) comprises a plurality of off-axis parabolic mirrors, the focal points of the plurality of off-axis parabolic mirrors respectively coincide with the cores of the corresponding incident optical fibers (3), and collimate the outgoing light rays of the plurality of incident optical fibers (3) into parallel light rays; The focus of the second off-axis parabolic mirror group (2) coincides with the core of the output optical fiber (4); The light output direction of the plurality of off-axis parabolic mirrors coincides with the light input direction of the second off-axis parabolic mirror group (2); The aperture of the second off-axis parabolic mirror group (2) is larger than the diameter of the circumscribed circle of the first off-axis parabolic mirror group (1); The core diameter of the output optical fiber (4) should not be less than the core diameter of the input optical fiber (3); The circumscribed circle diameter D of the first off-axis parabolic mirror group (1) 外接 The relationship with the core diameter D0 of the output optical fiber (4) is as follows: ， Wherein, H is the distance between the first off-axis parabolic mirror group (1) and the second off-axis parabolic mirror group (2), d1 is the core diameter of the incident optical fiber (3), and f1 is the focal length of the first off-axis parabolic mirror group (1); The relationship between the core diameter D0 of the output optical fiber (4) and the core diameter d1 of the input optical fiber (3) satisfies: ， Wherein, f1 is the focal length of the first off-axis parabolic mirror group (1), and f2 is the focal length of the second off-axis parabolic mirror group (2).

2. The optical fiber combining device according to claim 1, characterized in that: The focal length f1 and aperture D1 of the first off-axis parabolic mirror group (1) and the NA value of the incident optical fiber (3) satisfy the following relationship: , Wherein, d1 is the core diameter of the incident optical fiber (3).

3. The optical fiber combining device according to claim 1, characterized in that: The incident optical fibers (3) are arranged in a staggered manner; Or the incident optical fibers (3) are arranged in a tower structure.

4. The optical fiber combining device according to claim 1, characterized in that: The multiple off-axis parabolic mirrors in the first off-axis parabolic mirror group (1) and the second off-axis parabolic mirror group (2) are all 90° off-axis parabolic mirrors.

5. The method for using the optical fiber bundle combining device according to any one of claims 1 to 4, characterized in that: The method of use specifically comprises the following steps: A first flange is installed at one end of each input optical fiber, and the relative position of the first flange and the first off-axis parabolic mirror group is adjusted and fixed so that the focal points of the multiple off-axis parabolic mirrors in the first off-axis parabolic mirror group coincide with the cores of the corresponding input optical fibers; Installing a second flange at one end of the output optical fiber, adjusting the relative position of the first flange and the second off-axis parabolic mirror group and fixing them so that the focus of the second off-axis parabolic mirror group coincides with the core of the output optical fiber; The relative positions of the first off-axis parabolic mirror and the second off-axis parabolic mirror group are adjusted and fixed so that the light output direction of the multiple off-axis parabolic mirrors in the first off-axis parabolic mirror group coincides with the light input direction of the second off-axis parabolic mirror group.

6. The method of use according to claim 5, characterized in that: Arrange multiple input optical fibers in a staggered or tower-like structure.

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