JP5958068B2 - Multi-core optical fiber mounting method - Google Patents

Description

  The present invention relates to a method for mounting a multi-core optical fiber.

  Single-core optical fibers have a single core extending along the fiber axis in a common cladding, whereas multi-core optical fibers have multiple cores extending along the fiber axis in a common cladding. Have. Patent Documents 1 and 2 disclose a method of bending and mounting a single core optical fiber to a small diameter. Patent Document 1 discloses a reduction in loss when a multimode optical fiber having a small diameter (70 to 90 μm) is bent to a curvature radius of 5 mm. Patent Document 2 discloses a fiber that has a bending loss of 1 dB / turn or less at a wavelength of 1100 nm when bent with a radius of curvature of 1 mm.

International Publication No. 2009/022479 Japanese Patent No. 4444177

  The method of mounting a single core optical fiber employs a thin cladding. However, since the multi-core optical fiber has a plurality of cores arranged at appropriate intervals in the fiber cross section, there is a limit to simultaneously realizing the number of cores, low crosstalk, low loss, and high reliability.

  In other words, in a multi-core optical fiber, if an inter-core pitch necessary for suppressing cross-core between cores is ensured and a large number of cores are arranged in the fiber cross section, the cladding outer diameter increases. When such a multi-core optical fiber is bent to a small diameter, breakage is more likely to occur than an optical fiber having a normal outer diameter. Further, since bending loss tends to occur when the multi-core optical fiber is bent, it is also important to suppress bending loss.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a multi-core optical fiber mounting method that can have high reliability even when bent to a small diameter.

  The multi-core optical fiber mounting method of the present invention is a method for mounting a multi-core optical fiber having a plurality of cores extending along the fiber axis in a common cladding, and a partial range of the multi-core optical fiber in the fiber axis direction. The coating removal process to remove the coating, the thinning process to selectively thin the cladding in the range where the coating has been removed by the chemical removal process, and the thinning of the cladding through the thinning process And a bending step of bending the multi-core optical fiber within the specified range.

In the multi-core optical fiber mounting method of the present invention, it is preferable to bend the multi-core optical fiber with a bending radius of 10 mm or less in the bending step, and it is also preferable to bend the multi-core optical fiber with a bending radius of 5 mm or less in the bending step. Multi-core optical fiber mounting method of the present invention, the core is preferred that has a refractive index profile of the trench, the core is also preferred to have a W-shaped refractive index profile, the refractive index of the core gas step type It is also preferred to have a profile.

  The multi-core optical fiber mounting method of the present invention preferably further includes a fixing step of fixing the multi-core optical fiber after the diameter reducing step. The multi-core optical fiber mounting method of the present invention preferably further includes a re-coating step of re-coating the clad in the range where the coating has been removed after the thinning step. In the multi-core optical fiber mounting method of the present invention, it is preferable that the diameter of the cladding is reduced in a taper shape in the diameter reduction process.

  The multi-core optical fiber mounting method of the present invention is a method of mounting a multi-core optical fiber having a plurality of cores extending along the fiber axis in a common cladding, and is a method of mounting the multi-core optical fiber in the fiber axis direction. A coating removing process for removing the coating of the partial area, a bending process for bending the multi-core optical fiber in the range where the coating is removed in the coating removing process, and a heating process for heating the multi-core optical fiber in the range bent in the bending process; A fixing step of fixing the multi-core optical fiber after the heating step.

  According to the multi-core optical fiber mounting method of the present invention, high reliability can be obtained even when bent to a small diameter.

It is a figure explaining the coating removal process and diameter reduction process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the coating removal process and diameter reduction process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the coating removal process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the fixing process and re-coating process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the re-coating process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the bending process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the bending process in the multi-core optical fiber mounting method of this embodiment. It is a figure explaining the bending process and heating process in the multi-core optical fiber mounting method of this embodiment. It is a graph which shows the relationship between a bending radius and a fracture probability. It is a graph which shows the relationship between a bending radius and a bending loss.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  Multi-core optical fibers have, for example, seven cores extending along the fiber axis in a common cladding. Each core may have a trench-type refractive index profile, a W-type refractive index profile, or a high Δn step-type refractive index profile. . In order to suppress crosstalk between cores, the pitch between cores needs to be 30 μm or more. In order to reduce the occurrence of loss due to optical coupling to the coating, the distance from the center of the core farthest from the center of the fiber cross section to the cladding surface must be 30 μm or more. Therefore, the outer diameter of the clad needs to be 120 μm or more. In order to further suppress the crosstalk between the cores, the pitch between the cores needs to be 35 μm or more, and in this case, the cladding outer diameter needs to be 130 μm or more. This cladding outer diameter of 130 μm is larger than the cladding outer diameter of a normal optical fiber.

  The multi-core optical fiber mounting method according to the present embodiment includes a coating removal process for removing a partial range of coating in the fiber axis direction of the multi-core optical fiber, and a method for selectively chemically coating the cladding in a range where the coating has been removed in the coating removal process. And a bending step of bending the multi-core optical fiber in a range in which the cladding is reduced in the diameter reduction step. In addition, the multi-core optical fiber mounting method of the present embodiment may further include a fixing step of fixing the multi-core optical fiber after the thinning step, or a clad in a range where the coating is removed after the thinning step. You may further provide the recoating process which recoats.

  Alternatively, the multi-core optical fiber mounting method according to the present embodiment includes a coating removing step of removing a partial range of coating in the fiber axial direction of the multi-core optical fiber, and bending the multi-core optical fiber in a range where the coating is removed in the coating removing step. A bending step, a heating step of heating the multi-core optical fiber in a range bent in the bending step, and a fixing step of fixing the multi-core optical fiber after the heating step.

  In the coating removal step, the coating of a part of the multi-core optical fiber is removed. At this time, a partial range of coating around the bent portion of the multicore optical fiber may be removed, or a partial range of coating in the middle of the multicore optical fiber may be removed. In the diameter reduction step after the coating removal step, the cladding in the range where the coating has been removed is selectively reduced in diameter by a chemical method (etching). At this time, etching does not reach the core.

  As shown in FIG. 1, in the coating removal step, the coating 12 in a partial range in the middle of the multi-core optical fiber 10 may be removed, and the cladding 11 in the range from which the coating has been removed may be reduced in diameter. In order to reduce the diameter of the clad 11, the surface of the clad 11 may be etched with hydrofluoric acid.

  As shown in FIG. 2, in the coating removal step, the coating 12 in a part of the periphery of the bent portion of the multi-core optical fiber 10 is removed, and the cladding 11 in the range where the coating has been removed is tapered to reduce the diameter. (The closer to the periphery of the bent portion, the thinner). In order to reduce the diameter of the clad 11 in a tapered shape, the periphery of the bent portion of the clad 11 may be immersed in hydrofluoric acid and gradually lifted.

  As shown in FIG. 3, in the coating removal step, only a partial range of the coating 12 around the bent portion of the multicore optical fiber 10 may be removed.

  As shown in FIG. 4, the periphery of the bent portion of the multi-core optical fiber 10 may be fixed with the ferrule 20 in the fixing step, and the clad may be recoated in the recoating step for the unfixed portion.

  As shown in FIG. 5, the cladding may be recoated in the recoating step without fixing the periphery of the bent portion of the multi-core optical fiber 10 in the fixing step.

  As shown in FIG. 6, the multi-core optical fiber 10 may be bent and fixed by the fixing portion 30 in the bending step.

  As shown in FIG. 7, the multi-core optical fiber 10 may be bent and fixed by the fixing portion 30 in the bending process, or may be further subjected to ferrule processing.

  As shown in FIG. 8, the multi-core optical fiber 10 may be bent in the bending step, the stress may be relaxed by heating the bent portion with a gas burner or a heater in the heating step, and fixed in the fixing step. When fixing, a fixing part may be used or a resin mold may be used.

  FIG. 9 is a graph showing the relationship between the bending radius and the fracture probability. Here, the breaking probability is a probability that an optical fiber bent by 0.5 turn with a predetermined bending radius will break by the end of 10 years. As shown in this figure, the smaller the bending radius, the greater the probability of fracture. The smaller the cladding diameter, the lower the probability of fracture and the higher the reliability.

  FIG. 10 is a graph showing the relationship between the bending radius and the bending loss. The figure shows a core having a refractive index profile conforming to ITU-T G.657.A1, a core having a refractive index profile conforming to ITU-T G.657.A2, and ITU-T G.657.A2. For each core having a refractive index profile according to B3, the relationship between the bending radius and bending loss is shown. The bending loss is the loss increase amount of the optical fiber when bent by 0.5 turn at a predetermined bending radius. A core having these refractive index profiles has low bending loss.

  As described above, the multicore optical fiber that is bent and mounted by the multicore optical fiber mounting method of the present embodiment can have high reliability and low bending loss.

  DESCRIPTION OF SYMBOLS 10 ... Multi-core optical fiber, 11 ... Cladding, 12 ... Resin, 20 ... Ferrule, 30 ... Fixed part

Claims (15)

A method of mounting a multi-core optical fiber having a plurality of cores extending along a fiber axis in a common cladding,
A coating removing step of removing a partial range of coating in the fiber axial direction of the multi-core optical fiber;
A diameter reduction step of selectively reducing the diameter of the clad in the range where the coating has been removed in the coating removal step by a chemical method;
A bending step of bending the multi-core optical fiber in a range where the cladding is thinned in the thinning step;
A multi-core optical fiber mounting method comprising:   The multi-core optical fiber mounting method according to claim 1, wherein the multi-core optical fiber is bent at a bending radius of 10 mm or less in the bending step.   The multi-core optical fiber mounting method according to claim 1, wherein the multi-core optical fiber is bent at a bending radius of 5 mm or less in the bending step.   The multi-core optical fiber mounting method according to claim 1, wherein the core has a trench type refractive index profile.   The multi-core optical fiber mounting method according to claim 1, wherein the core has a W-type refractive index profile. Multi-core optical fiber mounting method according to claim 1, characterized in that it comprises a refractive index profile of the core gas step type.   The multicore optical fiber mounting method according to claim 1, further comprising a fixing step of fixing the multicore optical fiber after the diameter reducing step.   The multi-core optical fiber mounting method according to claim 1, further comprising a recoating step of recoating the clad in a range where the coating is removed after the diameter reducing step.   The multi-core optical fiber mounting method according to claim 1, wherein the diameter of the clad is reduced in a taper shape in the diameter reduction step. A method of mounting a multi-core optical fiber having a plurality of cores extending along a fiber axis in a common cladding,
A coating removing step of removing a partial range of coating in the fiber axial direction of the multi-core optical fiber;
A bending step of bending the multi-core optical fiber in a range where the coating is removed in the coating removing step;
A heating step of heating the multi-core optical fiber in a range bent in the bending step;
A fixing step of fixing the multi-core optical fiber after the heating step;
A multi-core optical fiber mounting method comprising:   The multi-core optical fiber mounting method according to claim 10, wherein the multi-core optical fiber is bent at a bending radius of 10 mm or less in the bending step.   The multi-core optical fiber mounting method according to claim 10, wherein the multi-core optical fiber is bent at a bending radius of 5 mm or less in the bending step.   The multi-core optical fiber mounting method according to claim 10, wherein the core has a trench-type refractive index profile.   The multi-core optical fiber mounting method according to claim 10, wherein the core has a W-type refractive index profile. Multi-core optical fiber mounting method according to claim 10, characterized in that it has a refractive index profile of the core gas step type.

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