JP2005300594A - Fiber fuse stopper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber fuse stopper which is low in cost, has a wide light intensity application range, and can be easily replaced.
A refractive index distribution type lens 6 is provided on a connecting member that butt-connects optical fibers to widen the mode field diameter of the optical fiber to stop the progress of the fiber fuse, and the optical fiber 5 is inserted through the refractive index distribution type lens. , 5 are connected to each other, a fiber fuse stopper.
[Selection] Figure 1

Description

  The present invention relates to a fiber fuse stopper for protecting an optical waveguide / component in a system for guiding high output light to an optical waveguide (optical communication field, laser processing field, etc.).

  In recent years, a dramatic increase in transmission capacity has been realized in the field of optical communications. As the transmission capacity increases, the intensity of light flowing through optical fibers and devices also increases, and fiber fuses are generated due to the attachment of minute debris etc. to the optical connection surface, etc. There is a possibility that the device is also destroyed (for example, see Non-Patent Documents 1 to 4).

As a conventional technique for solving this problem, a technique described in Patent Document 1 has been proposed. The technique described in Patent Document 1 is a fiber fuse by providing a core expansion part having a taper part in a part of an optical fiber to increase a mode field diameter (MFD) and lowering an energy density of light. There has been proposed a fiber fuse blocking member that stops the progress of the above.
Seo et al., 2003 IEICE Communication Society Conference, p. 321 Seo et al., National Fiber Optics Engineers Conference, 2003 Technical Proceedings, p.22-30 Maeda et al., 2003 IEICE Communication Society Conference, p. 320 DPHand and P.St.J.Russell, OPTICS LETTERS, Vol.13, No.9, September 1988, p.767-769 JP 2002-372636 A

However, the prior art described in Patent Document 1 has the following problems.
In order to realize the structure of the prior art, when the core is expanded by heating the optical fiber, it takes a long time at a considerably high temperature, so there is a cost demerit and the fiber is used to coat and remove the intermediate portion of the fiber. Due to the deterioration of strength and the deterioration of strength due to heating, there is a problem that the probability of fracture in a normal use state is increased and the reliability of the entire system is lowered. In addition, providing a reinforcing structure for reinforcing the strength-degraded portion has a problem of increasing costs.

  In addition, the conventional technology reduces only the optical energy in the core among the factors that cause fiber fuse, but the other factor is the inability to prevent heat transfer, so there is a limit to the system light intensity that can prevent fiber fuse. is there. Furthermore, in an optical fiber such as a single-mode optical fiber, the expansion of the mode field diameter obtained by dopant diffusion is about three times, so that the reduction in optical energy density is at most about 1/9. There is a limit to the reduction in light energy density, and there is a problem that the applicable range is narrow.

  In the prior art, an optical fiber having a core expansion portion in the middle is manufactured, and optical connector terminal processing is applied to both ends of the optical fiber to connect to a transmission line or a transmission device / device. There is a problem that the connection loss and the cost are disadvantageous.

  In addition, in the conventional technology, an optical fiber having a core expansion portion in the middle is manufactured, and optical connector terminal processing is applied to both ends of the optical fiber to connect to a transmission line or a transmission device / device. If this is performed outside the equipment casing, the installation location is required. In addition, when installed in the housing of the device, there is a problem that it takes time to replace the fiber fuse stopper when a fiber fuse occurs.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a fiber fuse stopper that is low in cost, has a wide range of application of light intensity, and can be easily replaced.

In order to achieve the above object, according to the present invention, a refractive index distribution type lens having a mode field diameter larger than that of an optical fiber is provided in a connecting member that butt-connects optical fibers, and the optical fibers are connected via the refractive index distribution type lens. A fiber fuse stopper is provided.
In the fiber fuse stopper of the present invention, the connection member is an optical adapter for connecting optical connectors terminated to an optical fiber, and the gradient index lens is housed in a split sleeve for fixing a ferrule. Is preferable.
In the fiber fuse stopper of the present invention, the connecting member may be a plug jack, and the gradient index lens may be housed in a split sleeve for fixing a ferrule.
In the fiber fuse stopper of the present invention, it is preferable that a structure in which a pipe is put on the outer periphery of the gradient index lens and has the same diameter as the ferrule is housed in a split sleeve.

The fiber fuse stopper of the present invention does not require a process of removing the coating of the optical fiber or heating and expanding the core, and the optical fiber itself is not subjected to any treatment, so that the mechanical strength and the like are deteriorated. There is no reliability.
In addition, since the mode field diameter can be greatly enlarged by using the gradient index lens, the light intensity at which the progress of the fiber fuse can be stopped can be remarkably increased.
In addition, since a gradient index lens can be connected to a PC by incorporating a refractive index distribution lens in an adapter and abutting with a connector ferrule, an additional process such as an AR coating is not required and can be provided at low cost.
Moreover, since there is no addition of a connector or a connection part, it can provide at low cost.
Further, there is no increase in connection loss because there is no additional connector or connection part.
Also, by incorporating it in the optical adapter, it is not time-consuming to replace parts when a fiber fuse occurs.
In addition, by installing in the adapter, no extra installation space is required.
Further, by incorporating a gradient index lens into a plug jack or mechanical splice type as a connecting member, it can be easily applied to an existing system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the fiber fuse stopper of the present invention, a refractive index distribution type lens having a mode field diameter larger than that of an optical fiber is provided on a connection member that butt-connects optical fibers, and the optical fibers are connected via the refractive index distribution type lens. It is characterized by that. Examples of the connection member include an optical adapter, a plug jack, and a mechanical splice that connect optical connectors terminated to an optical fiber.

  FIG. 1 is a view showing a first embodiment of a fiber fuse stopper according to the present invention. In this example, an optical adapter 1 for connecting optical connectors 2A and 2B whose connecting members are terminated to optical fibers 5 and 5 is shown. The refractive index distribution type lens 6 is housed in the split sleeve 4 for fixing the ferrules 3 and 3, and the end surfaces of the optical fibers and the refractive index distribution type lens 6 exposed at the center of the end surfaces of the ferrules 3 and 3 are provided. It has a butt-connected configuration.

  The optical adapter 1 has holes for receiving optical connectors 3 and 3 on the left and right, respectively, and a split sleeve 4 in which a gradient index lens 6 is housed in the center. Each optical connector 3, 3 attached to the optical adapter 1 has the ferrule 3, 3 tip inserted into the split sleeve 4, and the end face of the ferrule 3, 3 and the end face of the gradient index lens 6 are brought into contact with each other. ing. In this abutment, the optical fiber end face and the gradient index lens 6 exposed at the center of each end face of the ferrules 3 and 3 with an appropriate pressure by the elastic repulsive force of the springs 7 built in the optical connectors 2A and 2B. And butt connection (PC connection; Physical Contact connection).

As the optical connectors 4A and 2B, various conventionally known optical connectors can be used. For example, all commonly used optical connectors such as SC type optical connectors, FC type optical connectors, MU type optical connectors, LC type optical connectors and the like. It is applicable to.
The material, dimensions, etc. of the ferrules 3 and 3 are not particularly limited, and can be selected from various conventionally known ferrules for optical connectors.
The optical adapter 1 can be of an appropriate type according to the optical connectors 2A and 2B.
Further, the split sleeve 4 can be selected from conventionally known ones according to the outer shape of the ferrules 3 and 3 and used.

  The gradient index lens 6 is a cylindrical lens having a refractive index distribution in the radial direction, and is a type of lens also called a GRIN lens or a rod lens. The refractive index distribution type lens 6 is made of multicomponent glass such as Selfoc (trademark of Nippon Sheet Glass Co., Ltd.), or refraction made of quartz glass described in Japanese Patent Application No. 2001-104929 previously filed by the present applicant. A rate distribution lens or the like can be used. For example, among the gradient index lenses described in Japanese Patent Application No. 2002-256160 filed earlier by the present applicant, it is preferable to use a gradient index lens having a pitch of about 0.5 pitch. Note that the length of one pitch in the gradient index lens is the meandering cycle of light rays traveling in the gradient index lens.

The gradient index lens 6 preferably has the same diameter as the ferrule 3 and can be stored in the split sleeve 4 as it is.
In the case where the outer diameter of the gradient index lens 6 is smaller than the ferrule 3, a pipe made of metal, ceramics, resin or the like is put around the gradient index lens 6 in advance so as to have the same diameter as the ferrule 3. It is desirable to store in the split sleeve 4.

  This optical adapter type fiber fuse stopper has a configuration in which the refractive index distribution type lens 6 capable of greatly expanding the mode field diameter of the optical fiber 5 is disposed so as to contact the fiber end surface of the optical connector. The upper limit of the light intensity that can prevent the light is greatly expanded. For example, when the quartz rod lens described in the above-mentioned Japanese Patent Application No. 2002-256160 is used, the mode field diameter is about 150 μm with a diameter of 0.4 mm, and the light energy density can be reduced to about 1/200. It is possible to use up to about 20 times the light intensity with respect to the fiber fuse stopper using the optical fiber core expansion. In addition, by using a lens with a diameter of 2.5 mm that matches the outer diameter of the ferrule, the optical energy density can be reduced to about 1/15000, so that the fiber fuse stopper using the optical fiber core expansion can be reduced. The light intensity up to about 1500 times can be used.

  In the fiber fuse stopper using the optical adapter 1, the light transmitted through one of the optical fibers 5 normally passes through the gradient index lens 6 interposed between the connectors 2 A and 2 B and the ferrules 3 and 3. The optical fiber is sent to the other optical fiber 5 and functions as a normal optical connection part. On the other hand, when a fiber fuse occurs, the light emitted from the optical connector is enlarged by the gradient index lens 6 and the optical energy density is lowered, so that the progress of the fiber fuse can be prevented.

Since this fiber fuse stopper has a fiber fuse blocking function, it is not necessary to remove the coating of the optical fiber 5 or to expand the core by heating, and the optical fiber 5 itself is not subjected to any processing. Since it is not applied, there is no deterioration in mechanical strength and the reliability is high.
Further, since the mode field diameter can be greatly enlarged by using the gradient index lens 6, the light intensity at which the progress of the fiber fuse can be stopped can be remarkably increased.
Further, the refractive index distribution type lens 6 is incorporated in the optical adapter 1 and can be PC-connected by being sandwiched between the ferrules 3 and 3 of the optical connectors 2A and 2B. It is not necessary to add an anti-reflection film such as an AR coating to the end face, and can be manufactured at low cost.
Moreover, since there is no addition of a connector and a connection part compared with a prior art, it can provide at low cost.
Moreover, since there is no addition of a connector and a connection part compared with a prior art, there is no increase in connection loss.
Further, by incorporating the optical adapter 1 in the optical adapter 1, it is not time-consuming to replace parts when a fiber fuse occurs.
Further, by incorporating the gradient index lens 6 into the optical adapter 1, no extra installation space is required.

  FIG. 2 is a view showing a second embodiment of the fiber fuse stopper according to the present invention. In this example, the connecting member is the plug jack 8 and the gradient index lens 10 is in the split sleeve 9 for fixing the ferrule. It is configured to be stored in.

  The plug jack 8 has an optical connector and a refractive index distribution type by attaching an optical connector (not shown) terminated to an optical fiber to the optical connector mounting side and connecting the plug side to an optical fiber of a desired device or the like. The lens 10 is butt-connected.

  In the plug jack 8, similarly to the optical adapter 1 according to the first embodiment, when a fiber fuse is generated, the light emitted from the optical connector is expanded by the gradient index lens 10 and the optical energy density is increased. Is lowered, the progress of the fiber fuse can be prevented.

  As a modification of the present example, a fiber fuse stopper made of a gradient index lens can be disposed in advance in the mechanical splice.

  The fiber fuse stopper according to the second embodiment can obtain substantially the same effect as the first embodiment, and further, by incorporating a gradient index lens into a plug jack or mechanical splice type as a connection member, It can be easily applied to existing systems.

It is a figure which shows the 1st Example of the fiber fuse stopper of this invention, and is sectional drawing of the optical adapter incorporating the fiber fuse stopper. It is a figure which shows 2nd Example of the fiber fuse stopper of this invention, and is a side view of the plug jack incorporating the fiber fuse stopper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical adapter, 2A, 2B ... Optical connector, 3 ... Ferrule, 4 ... Split sleeve, 5 ... Optical fiber, 6 ... Gradient index lens, 7 ... Spring, 8 ... Plug jack, 9 ... Split sleeve, 10 ... Gradient index lens.

Claims (4)

  A fiber fuse stopper characterized in that a refractive index distribution type lens having a mode field diameter larger than that of an optical fiber is provided in a connecting member for connecting and connecting optical fibers, and the optical fibers are connected via the refractive index distribution type lens. .   The connection member is an optical adapter for connecting optical connectors terminated to an optical fiber, and the gradient index lens is housed in a split sleeve for fixing a ferrule. The fiber fuse stopper described.   The fiber fuse stopper according to claim 1, wherein the connecting member is a plug jack, and the gradient index lens is housed in a split sleeve for fixing a ferrule. 4. The fiber fuse stopper according to claim 2, wherein a pipe having a pipe covering the outer periphery of the gradient index lens and having the same diameter as the ferrule is housed in a split sleeve.

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