JP2012032524A - Multicore optical fiber and axis alignment method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicore optical fiber that can uniquely define a rotation angle in connecting multicore optical fibers.SOLUTION: A multicore optical fiber 1 is constituted of multiple cores 2, and a clad 3 that covers the periphery of the multiple cores 2 and has a refractive index smaller than that of the core 2. The arrangement of a core group 100 including multiple cores 2 is symmetrical only to a 2π rotation to an optical fiber axis.

Description

  The present invention relates to a multi-core optical fiber having a plurality of cores in an optical fiber cross section and an axis alignment method using the same, and more particularly, a multi-core capable of uniquely determining a rotation angle when connecting multi-core optical fibers. The present invention relates to an optical fiber and an axis alignment method using the same.

  With increasing demand for optical communication in recent years, it is required to increase the capacity and multiplexing of optical transmission lines, and various methods are being studied. Space division multiplexing is effective as a means for further expansion of transmission capacity in the future.

  A multi-core optical fiber has been studied as a method of performing space division multiplex transmission in a single optical fiber (see, for example, Patent Document 1). In this multi-core optical fiber, a plurality of core regions are provided in a clad having a uniform refractive index so that a plurality of optical transmission regions are provided, and stable space division multiplexing is achieved in a single optical fiber. Transmission can be performed.

JP-A-5-341147 JP-A-63-55505 JP 2010-55028 A

  By the way, when handling an optical fiber, it is important to consider the connection.

  In the case of a single core optical fiber, it is only necessary to accurately connect one core.

  On the other hand, when connecting a multi-core optical fiber, it must be noted that there are a plurality of cores to be connected. That is, it is necessary to determine the relative positions in the vertical direction, the horizontal direction, and the rotation direction so that the cores of the multi-core optical fibers to be connected coincide with each other and the light transmission loss is minimized.

  In particular, when performing maintenance that requires connection of multi-core optical fibers to a system in which multi-core optical fibers are operated, it is essential to maintain the order of cores (correspondence between cores of optical fibers). Become.

  Thus, when connecting multi-core optical fibers, alignment is a problem, unlike the case of single-core optical fibers.

  For example, in Patent Document 2, when two optical fibers are brought together, light is incident from one side, and the optical fibers are rotated relative to each other, the shaft is aligned at a position where the power is maximized on the receiving side. Has been proposed.

  Although this axis alignment method is epoch-making, the arrangement of the cores is symmetric with respect to the rotation angle θ <2π such as π / 3 rotation or π / 4 rotation around the optical fiber axis. There was a degree of freedom, and the rotation angle when connecting the multi-core optical fibers could not be determined uniquely. Also, the order of cores cannot be kept.

  Accordingly, an object of the present invention is to provide a multicore optical fiber capable of uniquely determining a rotation angle when connecting the multicore optical fibers and an axis alignment method using the same.

  The present invention devised to achieve this object is a multi-core optical fiber comprising a plurality of cores and a clad covering the periphery of the plurality of cores and having a refractive index lower than that of the cores. The arrangement of the core group including the core is a multi-core optical fiber that is symmetric only with respect to 2π rotation with respect to the optical fiber axis.

  The present invention is also directed to an axis alignment method using a multi-core optical fiber, wherein end faces of the first multi-core optical fiber and the second multi-core optical fiber are opposed to each other, and light from a light source is applied to the core of the first multi-core optical fiber. , The light emitted from the first multi-core optical fiber is incident on the second multi-core optical fiber, the light emitted from the second multi-core optical fiber is incident on a cladding mode remover, The light from which the clad mode has been removed by the clad mode remover is measured by an optical loss measuring instrument, and the first and second multi-core optical fibers are aligned so that the amount of light from which the clad mode has been removed is maximized. This is an axis alignment method using a multi-core optical fiber that adjusts the angle.

  The end surfaces are brought together so that the central axes in the longitudinal direction of the first and second multi-core optical fibers coincide with each other, and the first and second multi-core optical fibers are physically contacted or measured by the optical loss measuring device. Maintain a distance that does not affect the value, and rotate the central axis in the longitudinal direction of the first and second multi-core optical fibers so that the amount of light from which the cladding mode is removed becomes maximum. The first and second multi-core optical fibers may be aligned with each other.

  According to the present invention, the rotation angle when connecting the multi-core optical fibers can be uniquely determined.

It is sectional drawing which shows the multi-core optical fiber which concerns on embodiment of this invention. It is sectional drawing which shows the multi-core optical fiber which concerns on the modification of this invention. It is a figure explaining the axis alignment method using the multi-core optical fiber which concerns on embodiment of this invention.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing a multi-core optical fiber according to a preferred embodiment of the present invention, and FIG. 2 is a modification thereof.

  As shown in FIG. 1, a multicore optical fiber 1 according to the present embodiment covers a plurality of (19 in FIG. 1) cores 2 and the periphery of the plurality of cores 2 and has a refractive index higher than that of the cores 2. The arrangement of the core group 100 including the low clad 3 and including the plurality of cores 2 is symmetric only with respect to 2π rotation with respect to the optical fiber axis.

  In order to make the arrangement of the core group 100 symmetrical only with respect to 2π rotation with respect to the optical fiber axis, the core group 100 may be configured by forming the position detection core 4 in addition to the plurality of cores 2. Moreover, as shown in FIG. 2, it is good also as the multi-core optical fiber 5 which remove | eliminated one core other than a center from the several core 2. As shown in FIG.

  The plurality of cores 2 and the position detection core 4 have the same refractive index, and germanium may be added. The clad 3 has a refractive index lower than that of the plurality of cores 2 and the position detection core 4 and may be added with fluorine.

  Next, an axis alignment method using the multi-core optical fiber 1 (or 5) will be described.

  The measurement system for performing axis alignment includes an incident light source E1, a measurement optical fiber E2, large MFD (mode field diameter) optical fibers E4 and E8, multi-core optical fibers E6 and E7, and a cladding mode remover E9. And an optical loss measuring device E10.

  The measurement optical fiber E2 and the large MFD optical fiber E4 are connected by a V-groove connection E3, and light from the light source E1 leaks from the V-groove connection E3. Thereby, an operator can visually recognize ON / OFF of the light source E1.

  The large MFD optical fibers E4 and E8 are necessary for making light incident on all the cores of the multi-core optical fibers E6 and E7.

  The large MFD optical fiber E4 and the multi-core optical fiber E6, and the multi-core optical fiber E7 and the large MFD optical fiber E8 are connected by fusion splicing E5, respectively. The multi-core optical fiber E6 and the multi-core optical fiber E7 are connected by fusion splicing E11 after alignment.

  As a light propagation mode, in addition to a mode propagating through the core group 100, there is a mode propagating through the cladding 3. The value to be detected by the optical loss measuring device E10 at the time of connection and measurement is only the mode that propagates through the plurality of cores 2 and the position detection core 4, and the mode that propagates through the cladding 3 causes measurement errors. It is desirable to remove. The clad mode remover E9 is used to remove a mode propagating through the clad 3 that causes measurement errors.

  When connecting the first and second multi-core optical fibers E6 and E7 (both E6 and E7 are the above-described multi-core optical fibers 1) using this measurement system, the first multi-core optical fiber E6 and the second multi-core optical fibers E6 and E7 are connected to each other. The end face of the multi-core optical fiber E7 is made to face, light is incident on the position detection core 4 (or all the cores 2 and 4) of the first multi-core optical fiber E6 from the light source, and is emitted from the first multi-core optical fiber E6. The incident light is incident on the second multi-core optical fiber E7, the light emitted from the second multi-core optical fiber E7 is incident on the cladding mode remover E9, and the cladding mode remover E9 removes the cladding mode. Are measured by the optical loss measuring device E10, and the first and second multi-core optical fibers E6, E6, 7 to adjust the alignment of.

  More specifically, the end surfaces of the first and second multicore optical fibers E6 and E7 are brought together so that the central axes in the longitudinal direction coincide with each other (for example, while adjusting the outer diameter). The first and second optical fibers E6 and E7 are physically contacted or kept at a distance that does not affect the measurement value of the optical loss measuring device E10, and the light quantity of the light from which the cladding mode is removed is maximized. The first and second multi-core optical fibers E6 and E7 are aligned by rotating relative to the central axis in the longitudinal direction of the second multi-core optical fibers E6 and E7, and the rotation angle at which the optical loss is minimized. The first and second multi-core optical fibers E6 and E7 are connected by fusion splicing E11.

  Further, when the above-described multi-core optical fibers 5 and 5 are used as the first and second multi-core optical fibers E6 and E7, the end surfaces of the first and second multi-core optical fibers E6 and E7 are opposed to each other. After making light incident on the core 2 and adjusting the axial alignment of the first and second multicore optical fibers E6 and E7, the first and second multicore optical fibers E6 and E7 are connected to each other.

  In either case, since the arrangement of the core group 100 of the first and second multi-core optical fibers E6 and E7 is symmetric only with respect to 2π rotation with respect to the optical fiber axis, the rotation angle can be uniquely determined. There is only one degree of freedom.

  That is, by using the multi-core optical fiber 1 (or 5) according to the present embodiment, the rotation angle when connecting the multi-core optical fibers 1 (or 5) can be uniquely determined, and there is a correspondence relationship. Since the cores 2 can be connected to each other, the order of the cores can be maintained. Therefore, connection between multi-core optical fibers can be easily performed.

  In addition, according to the axis alignment method according to the present embodiment, the multi-core optical fibers can be easily connected to each other, so that a great effect can be obtained in a field that requires fusion connection of the optical fiber core wires. In particular, when performing transmission loss, cut-off wavelength, MFD, macrobend, and band measurement of a multi-core optical fiber, an effect of improving measurement accuracy can be obtained by using the clad mode remover E9.

  The axis alignment method of the present invention may be applied to an optical fiber having a hole structure and an optical fiber that performs wavelength division multiplexing transmission. Moreover, you may apply to the connection of a multi-core optical fiber and a single core optical fiber.

1 Multi-core optical fiber 2 Multiple cores 3 Clad 4 Position detection core 100 Core group

Claims (3)

In a multi-core optical fiber comprising a plurality of cores and a cladding covering the periphery of the plurality of cores and having a refractive index lower than that of the cores,
The multi-core optical fiber is characterized in that the arrangement of the core group including the plurality of cores is symmetric only with respect to 2π rotation with respect to the optical fiber axis. In an alignment method using a multi-core optical fiber,
The end surfaces of the first multicore optical fiber and the second multicore optical fiber are opposed to each other,
Incident light from a light source into the core of the first multi-core optical fiber;
Incident light emitted from the first multi-core optical fiber is incident on the second multi-core optical fiber;
The light emitted from the second multi-core optical fiber is incident on a cladding mode remover;
The light from which the cladding mode is removed by the cladding mode remover is measured with an optical loss measuring device,
An axis alignment method using a multi-core optical fiber, wherein the axis alignment of the first and second multi-core optical fibers is adjusted so that the amount of light from which the cladding mode is removed is maximized. The end surfaces are brought together so that the central axes in the longitudinal direction of the first and second multi-core optical fibers coincide,
The first and second multi-core optical fibers are in physical contact with each other, or the distance is kept so as not to affect the measurement value in the optical loss measuring device,
The first and second multi-core optical fibers are rotated by being rotated with respect to the central axis in the longitudinal direction of the first and second multi-core optical fibers so that the amount of light from which the cladding mode is removed becomes maximum. The axis alignment method using the multi-core optical fiber according to claim 2, wherein the axis alignment is performed.

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