JP2014035359A - Optical fiber connection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber connection method capable of low-loss connection of multi-core fibers by using a compact device.SOLUTION: An optical fiber connection method is provided with a plurality of cores and connects multi-core fibers whose cross sections are almost regular even-numbered polygons. The multi-core fibers have the same rotation symmetry where placement of the plurality of cores and fiber outlines share a fiber central shaft as a center. By observing the respective multi-core fibers from two different directions and moving and rotating fixed members fixing the multi-core fibers, adjustment is made so that two multi-core fiber positions and angles of rotation match, and adjusting the angle of rotation is based on a width of the multi-core fibers observed.

Description

  The present invention relates to an optical fiber connection method, and more particularly to an optical fiber connection method in which multi-core fibers having a plurality of cores and whose cross section is a substantially positive and even square are connected to each other.

  In recent years, in wired data communication, an optical fiber is generally used as the communication path. An optical fiber for data communication has a core through which light passes and a clad that surrounds the core and confines light in the core. Initially, a single core fiber having only one core was used for one optical fiber, but recently, it has been studied to use a multi-core fiber capable of transmitting and receiving a large amount of data through one optical fiber. A multi-core fiber is an optical fiber in which a plurality of cores are surrounded by a clad to constitute one optical fiber.

  In optical data communication, it is difficult to perform communication using only one optical fiber, and it is necessary to connect the optical fibers. When connecting single-core fibers, it is relatively easy to connect the cores because there is one core, but in the case of multi-core fibers, all the cores of the two fibers are aligned. If the connection is not made after that, the loss at the connection portion will increase, but such alignment is a difficult task.

  As a technique for low-loss fusion splicing of multi-core fibers, Non-Patent Document 1 discloses a technique using an apparatus for observing the fiber end face.

Arakawa et al., Proceedings of the IEICE General Conference 2 (2011) B-10-25, p348

  However, the apparatus for observing the fiber end face has a problem that it is large and expensive. Multi-core fiber connection is generally performed at construction sites and needs to be performed in a narrow space. Therefore, it is desirable to use the current small-sized fusion device that performs connection by observing the side of the fiber. It is rare.

  The present invention has been made in view of such a point, and an object of the present invention is to provide an optical fiber connection method capable of performing low-loss connection between multi-core fibers using a small device. is there.

  The optical fiber connecting method of the present invention is an optical fiber connecting method for connecting multi-core fibers each having a plurality of cores and having a cross section of a substantially regular even number of fibers, each of the two multi-core fibers being fixed members. Fixing each of the two multi-core fibers in a direction perpendicular to the central axis from the side, respectively, by aligning the directions of the central axes to face each other and facing each other's end faces. The position of the multi-core fiber in a direction perpendicular to the axis, the adjusting step of adjusting the rotation angle of the multi-core fiber around the central axis, and the end faces of the two multi-core fibers whose positions and rotation angles are adjusted are matched Connecting the multi-core fibers to each other, and the multi-core fibers are The arrangement of the core and the outer shape of the fiber have the same rotational symmetry about the center axis of the fiber, and in the adjusting step, the multi-core fiber is observed from two different directions, and the fixing member is By moving and rotating, the position of the two multi-core fibers is adjusted so that the rotation angle coincides, and the adjustment of the rotation angle is performed based on the width of the observed multi-core fiber. I have. Here, the substantially positive and even square means a shape in which the corner of the positive and even square is dropped and rounded, or each side is not a strict straight line but gently curved. In addition, in the cross section of the multi-core fiber, the arrangement of the plurality of cores and the fiber outer shape have the same rotational symmetry about the fiber center axis because the fiber outer shape is a regular even-numbered square. It means rotational symmetry (for example, 4-fold rotational symmetry, 6-fold rotational symmetry), and the arrangement of the cores is the same even-numbered rotational symmetry.

  The observation direction of one of the multicore fibers and the observation direction of one of the other multicore fibers are the same or different from each other by 180 degrees, and the widths of the two multicore fibers are the smallest in these observation directions. The structure which adjusts the said rotation angle so that it may become may be sufficient.

  The two different directions for observation may be orthogonal to each other.

  The substantially regular even polygon may be a substantially square or a substantially regular hexagon.

  The multi-core fiber is installed in a V-groove between the fixing member and the end surface, and the opening angle of the V-groove is the same as one outer angle of the regular even-numbered polygon. Good.

  Since the position and rotation angle of the multicore fiber are adjusted by observation in two directions from the side of the multicore fiber, it can be adjusted with an inexpensive and small device, and the rotation angle is adjusted based on the width of the multicore fiber. Can be adjusted.

2 is a diagram illustrating an end face of a multicore fiber in Embodiment 1. FIG. It is a typical figure showing a fiber connecting device concerning an embodiment. It is a figure which shows the relationship between the fiber width and rotation angle of the multi-core fiber which concerns on Embodiment 1. FIG. It is a schematic diagram which shows observing the multi-core fiber which concerns on Embodiment 1 from the side. It is another schematic diagram which shows observing the multi-core fiber which concerns on Embodiment 1 from the side. It is a figure which shows the end surface of the multi-core fiber in Embodiment 2. FIG. 6 is a diagram illustrating an end face of a multi-core fiber in Embodiment 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity.

(Embodiment 1)
FIG. 1 shows an end face of a multicore fiber to be connected in the first embodiment. In the multi-core fiber 100 according to the present embodiment, nine cores 10, 10,... Are surrounded by the clad 20, and the outer shape (outer shape of the clad 20) of the end surface (the surface perpendicular to the central axis appearing at the end) is increased. It is approximately square. The clad 20 is made of quartz, and the cores 10, 10,... Are made of a member having a refractive index higher than that of quartz by adding Ge or the like to quartz.

  An optical fiber made of quartz is likely to be chipped when a polygonal corner portion is present in the cross section, and if it is chipped, the optical fiber is likely to break. Therefore, the corners of the polygon in the cross section are rounded with the corners dropped. This square shape with rounded corners is expressed as an “substantially” square.

  In the multi-core fiber 100 according to the present embodiment, the nine cores 10, 10,... Are arranged at each vertex of the square, the center of each side of the square, and the center of the square in the fiber cross section. The square formed by the cores 10, 10,... And the square that is the outer shape of the clad 20 are concentric and have parallel sides. Due to such an arrangement, the cores 10, 10,... In the cross section are four-fold rotationally symmetric with the fiber center axis as the axis of rotation, like the substantially square shape that is the outer shape of the cladding 20.

  When connecting the multi-core fibers 100 in the present embodiment with the end faces butting each other, the connection loss is large unless the nine cores 10, 10,... turn into. Therefore, in the present embodiment, connection is performed by adjusting the position and rotation angle of the end faces of the two multi-core fibers 100 using the apparatus shown in FIG. As described above, in the cross section of the fiber, the cores 10, 10,... And the fiber outer shape are rotationally symmetric four times with the fiber central axis as the axis of rotation. .., The cores 10, 10,... Are similarly adjusted.

  The connecting device shown in FIG. 2 is a device for connecting two multi-core fibers 100, 100, and clamps (fixing members) 30, 30 for fixing the multi-core fibers 100, 100, and a guide in which a V-groove 41 is formed. Members 40 and 40 and discharge electrodes 35 and 35 are provided. A CCD camera for adjusting the position / rotation angle of the multi-core fibers 100, 100 is also provided, but is omitted because the figure becomes complicated. The arrangement of the CCD camera is shown in FIGS. 4 and 5, and will be described later.

  A portion of the multi-core fibers 100 and 100 sandwiched between the clamps 30 and 30 is covered and protected. A coating 101 is applied to the outer surface of the fiber extending from the clamps 30 and 30 on the side opposite to the end where the multi-core fibers 100 and 100 are connected.

  A connection method for connecting the two multi-core fibers 100 and 100 will be described below.

  First, two multi-core fibers 100 and 100 from which the coating 101 on the tip portion is removed are prepared.

  Then, the portion where the coating 101 of the two multi-core fibers 100 and 100 exists is sandwiched by the clamps 30 and 30 and fixed. Since the two clamps 30 and 30 are installed so that the center axis directions of the sandwiched fibers coincide with each other, the two multi-core fibers 100 and 100 are fixed when the two multi-core fibers 100 and 100 are fixed by the clamps. The direction of the central axis will coincide. And the mutual end surfaces to be connected are fixed facing each other. At this time, the portion where the coating 101 at the tip of the two multi-core fibers 100, 100 is removed is placed in the V grooves 41, 41 of the guide members 40, 40, and the most advanced portion to be connected is the V grooves 41, 41. It is in a state protruding from. Discharge electrodes 35 and 35 for fusion splicing are placed beside the opposite ends of the two multi-core fibers 100 and 100.

  Next, the single multi-core fiber 100 is observed with two CCD cameras, and the position in the plane orthogonal to the central axis of the multi-core fiber 100 and the rotation angle around the central axis are adjusted. . The CCD camera will be specifically described. As shown in FIG. 4, two CCD cameras 51 and 52 are placed along the end surface of the guide member 40 on the discharge electrode side, and the multi-core fiber placed in the V-groove 41. 100 is observed from the side. The two CCD cameras 51 and 52 have a direction perpendicular to the fiber central axis as an observation direction, and the observation directions form an angle of 90 degrees with each other. The V groove 41 also forms an angle of 90 degrees, and the observation direction of the CCD cameras 51 and 52 is parallel to the groove wall surface of the V groove 41, respectively.

  A specific method for adjusting the position in the plane orthogonal to the central axis of the multi-core fiber 100 is to observe the positions of the two multi-core fibers 100 and 100 in the plane with the CCD cameras 51 and 52, respectively. The clamps 30 and 30 and the guide members 40 and 40 are moved in the X and Y directions shown in FIG. 2 so that their positions coincide with each other.

  A specific method for adjusting the rotation angle around the central axis of the multi-core fiber 100 is to observe and measure the outer diameter of the multi-core fiber 100 with the CCD cameras 51 and 52, and clamp the outer diameter (width) to be minimized. This is a method of rotating 30 (adjustment of θ in FIG. 2). As the fiber rotates, the fiber outer diameter (width) observed from the side changes. FIG. 3 shows the relationship between the rotation angle and the normalized fiber width observed from the side when the multi-core fiber 100 is rotated around the central axis. Considering adjusting the rotation angle around the central axis according to the size of the outer diameter of the fiber, it is necessary to adjust so that the outer diameter becomes maximum or minimum. This is because when the outer diameter is other than the maximum or minimum, it is impossible to distinguish between the two states shown in FIGS. 5 (a) and 5 (b), for example.

  As shown in FIG. 4, since the V-groove 41 is opened at 90 degrees, the two side surfaces of the multi-core fiber 100 can be in contact with both groove wall surfaces. In this state, both CCD cameras 51 and 52 are outside the fiber. The minimum value of the diameter will be observed. As described above, the fiber is such that the CCD cameras 51 and 52 observe the minimum value of the outer diameter of the fiber while the fiber in which the two side surfaces of the multi-core fiber 100 are in contact with both wall surfaces of the V-groove 41 is stable. The rotation angle is preferably adjusted so that the outer diameter of the fiber is minimized. Furthermore, as shown in FIG. 3, at the rotation angle at which the outer diameter of the fiber is maximum, the change in the outer diameter of the fiber is small even if it is slightly rotated from this rotation angle, whereas at the rotation angle at which the outer diameter of the fiber is minimum. Since the outer diameter of the fiber changes greatly when it is slightly rotated from this rotation angle, the rotation angle that minimizes the outer diameter of the fiber can be found more easily and accurately. Also in this respect, it is preferable to adjust the rotation angle of the fiber so that the outer diameter of the fiber is minimized.

  If the position in the plane orthogonal to the central axis of the two multi-core fibers 100 and 100 and the rotation angle around the central axis can be adjusted, the end faces of the two multi-core fibers 100 and 100 are brought into contact with each other to form the discharge electrode 35. , 35 for fusion splicing. In this way, the two multi-core fibers 100, 100 can be connected by bringing the nine cores 10, 10,.

  Here, considering the case where the outer shape of the cladding is circular, the rotation angle cannot be determined by the outer diameter of the fiber, and when viewed from the side of the fiber, a plurality of cores overlap each other, and the arrangement of multi-cores Since it is difficult to accurately identify the core, it is necessary to determine the core arrangement by observing the fiber end face and adjust the rotation angle.

  Considering the case where the clad outer shape is an odd-numbered polygon, if the rotation angle when one CCD camera observes the minimum fiber outer diameter is α °, the fiber can be used even at a rotation angle of (α + 180) °. Although the outer diameter is minimized, the arrangement of the cores on the end face is different between α ° and (α + 180) °. Therefore, in order to connect a plurality of cores without misalignment, it is necessary to distinguish between α ° and (α + 180) °. However, since the two CCD cameras cannot distinguish this, it is also necessary to observe the end face of the fiber by observing the fiber end face. It is necessary to determine the arrangement and adjust the rotation angle.

  In the present embodiment, the multi-core fiber to be connected has the same rotational symmetry about the fiber center axis in the cross section of the arrangement of the plurality of cores and the outer shape of the fiber. If the adjustment is made according to the outer shape, the core is adjusted in the same way.

(Embodiment 2)
FIG. 6 shows an end face of the multi-core fiber to be connected in the second embodiment. In the multi-core fiber 110 according to the present embodiment, seven cores 10, 10,... Are surrounded by the clad 21, and the end face (the face perpendicular to the central axis appearing at the end) has the outer shape (the outer shape of the clad 21). It is a substantially regular hexagon. The cores 10, 10,... Are arranged at the center and each vertex of the regular hexagon on the fiber end surface, and the regular hexagon formed by the cores 10, 10,. The sides are parallel.

  The present embodiment is different from the first embodiment in the shape of the end face of the multi-core fiber 110, the number of cores 10, 10,... If the observation directions of the two CCD cameras are different by 90 °, the outer diameter of the multi-core fiber 110 of this embodiment is such that when one CCD camera observes the maximum diameter, the other CCD camera has the minimum diameter. Will observe.

  In this embodiment, it is preferable that the V-groove is opened at an angle of 120 ° or 60 °. This is because if the V-groove is opened at an angle of 120 ° or 60 °, the two outer surfaces of the multi-core fiber 110 come into contact with both groove wall surfaces of the V-groove and the multi-core fiber 110 becomes stable.

(Embodiment 3)
FIG. 7 shows an end face of the multi-core fiber to be connected in the third embodiment. In the multi-core fiber 120 in the present embodiment, nine cores 10, 10,... Are surrounded by the clad 22, and the outer shape (outer shape of the clad 22) of the end surface (the surface perpendicular to the central axis appearing at the end) is increased. It is a substantially regular octagon. The cores 10, 10,... Are arranged at the center and each vertex of the regular octagon on the fiber end face, and the regular octagon formed by the cores 10, 10,. The sides are parallel.

  The present embodiment is different from the first embodiment in the shape of the end face of the multi-core fiber 120, the number of cores 10, 10,... If the observation directions of the two CCD cameras are different by 90 °, the outer diameter of the multi-core fiber 120 of this embodiment is such that when one CCD camera observes the maximum diameter, the other CCD camera has the minimum diameter. Will observe.

  In the present embodiment, the V-groove is preferably opened at an angle of 90 ° or 135 °. This is because if the V-groove is opened at an angle of 90 ° or 135 °, the two outer surfaces of the multi-core fiber 120 come into contact with both groove wall surfaces of the V-groove and the multi-core fiber 120 becomes stable.

(Other embodiments)
The above-described embodiment is an exemplification of the present invention, and the present invention is not limited to these examples, and these examples may be combined or partially replaced with known techniques, common techniques, and known techniques. Also, modified inventions easily conceived by those skilled in the art are included in the present invention.

  The material constituting the clad is not limited to quartz, but may be a material obtained by adding other materials to quartz or plastic. The material constituting the core is not limited to the material in which Ge is added to quartz, and may be a material to which a material other than Ge is added, a material to which Ge and another material are added, or a plastic.

  The number of cores is not particularly limited as long as it is plural. Further, the core may be arranged in any arrangement as long as it has the same rotational symmetry as the outer shape of the fiber (around the fiber center axis).

  Observation from the side of the fiber may use an observation device other than a CCD camera as long as the position and width of the fiber can be observed. The observation direction is not limited to two directions that differ by 90 °, and the different angles of the observation direction may be any angles as long as the width of the core observed in both directions is different. There may be more than two observation devices. In addition to the fusion splicing, the fibers may be connected by a method of abutting the end faces and fixing with an adhesive or a fixing jig.

  As described above, since the optical fiber connection method according to the present invention can connect all the cores of a multi-core fiber with low loss, it is useful as a communication optical fiber connection method and the like.

10 core 20 clad 30 clamp (fixing member)
41 V groove 51, 52 CCD camera 100 Multi-core fiber 110 Multi-core fiber 120 Multi-core fiber

Claims (5)

An optical fiber connection method comprising a plurality of cores and connecting multi-core fibers whose cross sections are substantially positive and even squares,
Fixing each of the two multi-core fibers with a fixing member, matching the directions of the central axes of each other, and facing each other's end faces;
The two multi-core fibers are observed from the side in a direction orthogonal to the central axis, and the position of the multi-core fiber in the direction orthogonal to the central axis and the rotation angle of the multi-core fiber around the central axis are determined. An adjustment step to adjust;
A connection step of connecting the multi-core fibers by abutting end faces of the two multi-core fibers whose positions and rotation angles are adjusted, and
In the cross section of the multi-core fiber, the arrangement of the plurality of cores and the outer shape of the fiber have the same rotational symmetry about the fiber central axis,
In the adjustment step, the position of the two multi-core fibers and the rotation angle are matched by observing each multi-core fiber from two different directions and moving and rotating the fixing member. Adjust
The rotation angle is adjusted based on the width of the observed multi-core fiber.   The observation direction of one of the multicore fibers and the observation direction of one of the other multicore fibers are the same or different from each other by 180 degrees, and the widths of the two multicore fibers are the smallest in these observation directions. The optical fiber connection method according to claim 1, wherein the rotation angle is adjusted so that   The optical fiber connection method according to claim 1, wherein the two different directions for observation are orthogonal to each other.   The optical fiber connection method according to any one of claims 1 to 3, wherein the substantially regular even-numbered square is a substantially square or a substantially regular hexagon. The multi-core fiber is installed in a V-groove between the fixing member and the end face,
5. The optical fiber connection method according to claim 1, wherein an opening angle of the V-groove is the same angle as one outer angle of the regular even-numbered polygon.

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