Chip type multi-core optical fiber beam splitter

Abstract

The invention provides a chip type multi-core optical fiber beam splitter. The chip type multi-core optical fiber beam splitter is characterized in that the multi-core optical fiber beam splitter is composed of an optical fiber fixing quartz substrate, a quartz cover plate, a three-core optical fiber and three single-core optical fibers; wherein the optical fiber fixing quartz substrate is provided with two cross-shaped orthogonal V-shaped grooves, the cut flat end face of the three-core optical fiber and the first single-core optical fiber with the fiber end provided with a 45-degree reflection inclined plane are oppositely placed in the first V-shaped groove, and the flat end faces of the second single-core optical fiber and the third single-core optical fiber are oppositely placed in the second V-shaped groove; light transmitted by the middle core of the three-core optical fiber is output from the end face and then directly coupled into the core of the first single-core optical fiber, light transmitted by the two side cores is reflected by the 45-degree reflection inclined face of the first single-core optical fiber and then coupled into the fiber cores of the second single-core optical fiber and the third single-core optical fiber to be transmitted, and therefore beam splitting of the three-core optical fiber is achieved. The multi-core optical fiber beam splitter has the advantages of being small and exquisite in structure, stable in performance and capable of forming an array, and can be widely applied to the technical fields of data centers, optical fiber sensing and the like.

Description

Technical Field

[0001] The present invention relates to a chip-type multi-core optical fiber beam splitter, which can be used for beam splitting / combining of each core optical path of a three-core optical fiber and a double-core optical fiber, and belongs to the technical field of optical fiber integrated devices. Background Art

[0002] A multi-core fiber splitter is an integrated optical fiber device that separates the signal from each core of a multi-core optical fiber without interfering with each other and connects it to an ordinary standard single-mode optical fiber. In the application of multi-core optical fibers, multi-core fiber splitters are an important functional device that needs to be solved. Whether a multi-core optical fiber splitter with low loss, low crosstalk, small size and high reliability can be prepared is one of the key issues in the actual industrial application of multi-core optical fibers.

[0003] At present, the preparation methods of multi-core fiber splitters can be roughly divided into three categories, including spatial optics-based, on-chip waveguide-based and fiber bundle integration-based.

[0004] (1) Based on space optics

[0005] In 2012, Werner Klaus proposed a technical solution for a spatial optical lens-prism combined channel splitter (IEEE Photonics Technology Letters, 2012, 24 (21): 1902-1905.). The lens coupling system first uses a lens to spatially separate the multiple core output light beams of a multi-core optical fiber, then uses a steering prism to further separate them in layers, and finally uses a fiber collimator to receive them, thereby coupling each core optical channel of the multi-core optical fiber into each independent single-mode optical fiber. This method can reduce the crosstalk and loss of each optical channel through precise adjustment and control. The disadvantage of this multi-core optical fiber splitter is that the multi-core optical fiber splitter of this structure is large in size, complex in operation and adjustment, and high in cost, which is not suitable for large-scale production and use, and the more the number of cores, the more obvious this disadvantage is.

[0006] In order to make the multi-core fiber beam splitter compact, reliable, and more flexible and convenient to use, based on the above-mentioned spatial lens beam splitting coupling principle, Yusaku Tottori used a gradient refractive index self-focusing lens (GRIN) and a single-mode fiber collimator as discrete optical devices to achieve the miniaturization of a seven-core fiber beam splitter (IEEE Photonics Technology Letters, 2012, 24(21):1926-1928).

[0007] (2) Based on on-chip waveguide

[0008] Ultrafast lasers can be used to make high-quality optical waveguides in many dielectric materials. A typical example is the use of focused femtosecond lasers inside glass and crystal materials to make optical waveguides. However, although the geometric distribution of the waveguide structure at the output end of the beam splitter formed by femtosecond direct writing of waveguides can be very precise, the geometric shape and refractive index difference of the structural cross-section of each waveguide is difficult to match with the core structure of the optical fiber, so the insertion loss of the device is large.

[0009] (3) Fiber bundle integration

[0010] The simplest way to form a beam splitter is to closely arrange multiple thin-diameter optical fibers with cladding diameters equal to the core spacing of multi-core optical fibers according to the same core geometry distribution to form a fiber bundle, and then grind the end face of the fiber bundle flat so that it can be spliced ​​with the multi-core optical fiber to obtain a beam splitter with excellent performance. There are two methods for preparing thin-diameter optical fibers. One is to take a standard single-mode and etch it to obtain a thin-diameter end with an outer diameter equal to the core spacing; the other is to directly draw a non-standard thin-diameter optical fiber with a suitable diameter. Since non-standard diameter thin-diameter optical fibers are relatively fragile, it is not easy to operate and align them, and the device preparation is quite difficult. Summary of the invention

[0011] The object of the present invention is to provide a chip-type multi-core optical fiber splitter.

[0012] like Figure 1 As shown, the multi-core optical fiber splitter is composed of an optical fiber fixing quartz substrate 1, a quartz cover plate 2, a three-core optical fiber 3, and three single-core optical fibers 4, 5-1 and 5-2.

[0013] The optical fiber is fixed to a quartz substrate 1 such as Figure 2 As shown, it has two V-grooves 1-1 and 1-2 that are orthogonal to each other, and a circular hole 1-3 for observation and adjustment is provided at the intersection of the V-grooves.

[0014] like Figure 3 As shown, the three cores of the three-core optical fiber 3 are arranged in a line, and the core spacings are equal.

[0015] like Figure 4 As shown, the flattened end face of the three-core optical fiber 3 is placed relative to the first single-core optical fiber 4 with a 45° reflective bevel at the fiber end in the first V-groove 1-1, and the flat end faces of the second and third single-core optical fibers (5-1 and 5-2) are placed relative to each other in the second V-groove 1-2; the light output end face of the middle core of the three-core optical fiber 3 is directly coupled into the core of the first single-core optical fiber 4, and the light transmitted by the two side cores is reflected by the 45° reflective bevels 4-1 and 4-2 of the first single-core optical fiber, and then coupled into the cores of the second and third single-core optical fibers (5-1 and 5-2) for transmission, thereby realizing the splitting of the three-core optical fiber; the quartz cover plate is used for packaging the multi-core optical fiber splitter after adjusting the relative position relationship of the four optical fibers.

[0016] like Figure 5 As shown, the end face of the first single-core optical fiber 4 has 45° symmetrical reflective inclined surfaces 4-1 and 4-2, and a reflective film is coated on the inclined surfaces.

[0017] like Figure 6 As shown, the multi-core optical fiber may be a symmetrical dual-core optical fiber 6 ( Figure 6 (a)) or partial double core fiber 7 ( Figure 6 (b)).

[0018] like Figure 7 As shown, the multi-core optical fiber can also be a holey three-core optical fiber 8 ( Figure 7 (a)) or holey double-core optical fiber 9 ( Figure 7 Any one of (b)).

[0019] The core of the multi-core optical fiber is a single-mode core or a multi-mode core, such as a single-mode three-core optical fiber or a multi-mode three-core optical fiber.

[0020] like Figure 8 As shown, the core of the three-core optical fiber is a mixture of partially single-mode and partially multi-mode, for example, the middle core is multi-mode and the side core is single-mode. Figure 8 (a)) or partial double core fiber 11 ( Figure 8 (b)).

[0021] like Fig. 9 As shown, the present invention also provides a chip-type multi-core optical fiber beam splitter array, wherein the chip-type multi-core optical fiber beam splitter array is an array composed of a plurality of the above-mentioned chip-type multi-core optical fiber beam splitters.

[0022] The significant beneficial effects of the present invention are:

[0023] (1) The present invention adopts a V-groove limit alignment method, the device has a small size and high integration, and can be easily integrated into a multi-core optical fiber splitter array.

[0024] (2) The present invention is not limited by the number of modes of the multi-core optical fiber core, and is suitable for the optical path splitting / combining of multi-core single-mode optical fibers, as well as the optical path splitting / combining of few-mode and multi-mode multi-core optical fibers, and even for the optical path splitting / combining of single-mode and multi-mode hybrid multi-core optical fibers with different core sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural diagram of a chip-type multi-core fiber splitter.

[0026] Figure 2 This is a structural diagram of the optical fiber fixed to the quartz substrate.

[0027] Figure 3 This is the end face structure diagram of the three-core optical fiber.

[0028] Figure 4 This is a diagram showing the relative positions of the optical fibers inside a three-core optical fiber splitter.

[0029] Figure 5 It is a structural diagram of the 45° reflecting surface at the end of the first single-core optical fiber.

[0030] Figure 6 (a) is the end face diagram of the symmetrical dual-core optical fiber. Figure 6 (b) is the end face view of the partial dual-core optical fiber.

[0031] Figure 7 (a) is the end view of the three-core double-hole optical fiber. Figure 7 (b) is the end face view of the partial dual-core dual-hole optical fiber.

[0032] Figure 8 (a) and (b) are the end-face views of a three-core optical fiber and a two-core optical fiber, respectively, with the middle core being multimode and the side cores being single-mode.

[0033] Fig. 9 It is an array diagram composed of chip-type multi-core fiber optic splitters.

[0034] Fig.10 This is the first single-core optical fiber end 45° reflection surface grinding preparation process.

[0035] Fig.11 It is a method for aligning and assembling the optical fibers of a multi-core optical fiber splitter.

[0036] Fig.12 This is the optical path simulation result of the three-core fiber splitter. DETAILED DESCRIPTION

[0037] The present invention is further illustrated by the following specific examples.

[0038] Embodiment 1: Symmetrical dual-core optical fiber splitter and its preparation method.

[0039] The end face structure of the symmetrical dual-core optical fiber is as follows: Figure 6 As shown in (a), the fiber cladding diameter is 125 μm, the two single-mode fiber cores are symmetrically distributed inside the fiber, and the core spacing is 80 μm. The preparation method of the symmetrical dual-core fiber splitter is as follows:

[0040] Step 1: Preparation of optical fiber fixing quartz substrate 1. Select a quartz glass sheet with a length, width and height of 10mm×10mm×1mm, and use a scriber to cut two vertical and orthogonal V-grooves 1-1 and 1-2 on one side. Ensure that the depth of the V-grooves is consistent and can just accommodate an optical fiber with a cladding diameter of 125μm. Drill a through hole 1-3 at the intersection of the two V-grooves for the optical fiber adjustment observation window.

[0041] Step 2: Preparation of 45° reflection slope at the end of single-mode optical fiber. Fig.10 As shown, a single-core optical fiber 4 is selected, and the coating layer at one end is removed and cut flat. The single-core optical fiber is installed on the fiber end grinding device, and the angle between the optical fiber axis and the plane of the grinding disk 12 is adjusted to 45°, and then the grinding disk 12 is turned on to rotate, and a 45° bevel 4-1 is ground at the end of the single-core optical fiber. Then the single-core optical fiber is rotated 180° along the axis, and another 45° bevel 4-2 is ground. Observe under a microscope to ensure that the two bevels are symmetrically distributed. Finally, in the magnetron sputtering coating center, a gold reflective film is plated on the 45° bevel at the end of the single-core optical fiber.

[0042] Step 3: Assembly and adjustment of the dual-core fiber optic beam splitter.

[0043] The symmetrical dual-core optical fiber 3 and the single-core optical fiber 4 with a 45° reflection bevel are coaxially placed in a V-groove of the optical fiber fixing quartz substrate. The other two single-core optical fibers 5-1 and 5-2 are coaxially placed in another V-groove after the end faces are cut flat, so that the end faces of the four optical fibers are all located in the observation window of the optical fiber fixing quartz substrate 1 and appear in the field of view of the microscope 14. Under the illumination light source 13 and the microscope 14, the core angle of the dual-core optical fiber 3 and the angle of the 45° reflection bevel are rotated and adjusted, and the spacing between the end faces of the four optical fibers is adjusted so that the four optical fibers are arranged as shown in the figure. Fig.11 As shown in the figure on the right, a certain power of light is input through the single-core optical fiber end, and an optical power meter is used to read the optical power at the output end of the symmetrical dual-core optical fiber to determine whether each fiber core is well aligned, and fine-tuning is performed until the coupling efficiency of each fiber core reaches the maximum.

[0044] Step 4: After adjusting the relative position of the four optical fibers, apply glue in the V-groove to fix the geometric position of each optical fiber. Then bond the quartz cover plate to the optical fiber fixing quartz substrate to achieve a single-stage package of the device. Finally, put a rubber stress relief sleeve on the optical fiber pigtail and encapsulate the entire device in a metal shell to ensure mechanical strength.

[0045] Embodiment 2: Three-core optical fiber splitter and its preparation method.

[0046] The structure of the single-mode three-core optical fiber is as follows Figure 3 As shown, the difference between it and the symmetrical dual-core optical fiber in Example 1 is that there is an additional middle core.

[0047] The preparation method of the three-core beam splitter is basically the same as that in Example 1, except that the middle core of the three-core optical fiber needs to be optically coupled with the core of the single-mode optical fiber with a 45° bevel. Fig.12The figure shows the simulation results of the optical path coupling of the three cores of the three-core fiber splitter. The arrows represent the direction of the light beam. It can be seen that the light beams in the two side cores of the three-core fiber are respectively coupled with the second and third single-core fiber cores after being reflected by two symmetrical 45° reflection bevels after exiting the fiber end face; the output light of the middle core of the three-core fiber is coupled with the opposite first single-mode fiber core.

[0048] Example 3: Method for preparing a three-core optical fiber beam splitter array.

[0049] like Fig. 9 As shown, a plurality of packaged three-core optical fiber splitters in Example 2 are stacked and bonded together, and then packaged in a metal housing to form a three-core optical fiber splitter array.

Claims

1. A chip-type multi-core optical fiber splitter, characterized in that: The multi-core optical fiber beam splitter is composed of an optical fiber fixing quartz substrate, a quartz cover plate, a three-core optical fiber, and three single-core optical fibers; wherein the optical fiber fixing quartz substrate has two cross-orthogonal V-grooves, and a circular hole for observation and adjustment is provided at the intersection of the V-grooves; the flattened end face of the three-core optical fiber and the first single-core optical fiber with a 45° reflection bevel at the fiber end are placed in the first V-groove relative to each other, and the flat end faces of the second and third single-core optical fibers are placed in the second V-groove relative to each other; the light output end face of the middle core of the three-core optical fiber is directly coupled into the core of the first single-core optical fiber, and the light transmitted by the two side cores is reflected by the 45° reflection bevel of the first single-core optical fiber and coupled into the cores of the second and third single-core optical fibers for transmission, thereby realizing the beam splitting of the three-core optical fiber; The quartz cover is used for packaging the multi-core fiber splitter after adjusting the relative position relationship of the four optical fibers; The three cores of the three-core optical fiber are arranged in a line, and the core spacing is equal; The end face of the first single-core optical fiber has a 45° symmetrical reflection inclined surface, and a reflection film is coated on the inclined surface.

2. The chip-type multi-core optical fiber splitter according to claim 1, characterized in that: The three-core optical fiber can be replaced by any one of a symmetrical dual-core optical fiber, a partial dual-core optical fiber, a three-core optical fiber with a hole, a symmetrical dual-core optical fiber with a hole, and a partial dual-core optical fiber with a hole.

3. The chip-type multi-core optical fiber splitter according to claim 1, characterized in that: The core of the three-core optical fiber is a single-mode core or a multi-mode core.

4. The chip-type multi-core optical fiber splitter according to claim 1, characterized in that: The core of the three-core optical fiber is a mixed core of single mode and multimode.

5. A chip-type multi-core optical fiber beam splitter array, characterized in that: The chip-type multi-core optical fiber beam splitter array is an array formed by combining a plurality of chip-type multi-core optical fiber beam splitters according to any one of claims 1 to 4.

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