JP2022075219A - Multi-core fiber having connector - Google Patents

Abstract

To provide a multi-core fiber having a connector, capable of preventing or relaxing a positional deviation caused on the end surface of a core when polishing the end surface of the multi-core fiber having at least one core spirally formed in a plurality of cores.SOLUTION: A multi-core fiber 1 having a connector includes: a multi-core fiber 10 having at least one core spirally formed in a plurality of cores; and a connector 20 provided in the end part of the multi-core fiber 10. The end part of the multi-core fiber 10 is served as a non-spiral part SP1 having a linear core (or a slack spiral part having a spiral frequency per unit length of the core less than that of a portion except the end of the multi-core fiber).SELECTED DRAWING: Figure 1

Description

The present invention relates to a multi-core fiber with a connector.

In recent years, a multi-core fiber in which at least one of a plurality of cores is formed in a spiral shape has been developed. This multi-core fiber is also called a spun multi-core fiber. Such span multi-core fibers are used, for example, in contact sensors, shape sensors, and medical applications. The following Patent Documents 1 and 2 and the following Non-Patent Document 1 disclose conventional span multi-core fibers.

Japanese Unexamined Patent Publication No. 2018-132421 US Pat. No. 8,773,650

P. S. Westbrook et al., “Integrated optical fiber shape senor modules based on twisted multicore fiber grating arrays”, Proc. SPIE 8938, Optical Fibers and Sensors for Medical Diagnostics and Treatment Applications XIV, 89380H (February 20 2014)

By the way, in the above-mentioned span multi-core fiber, when the end face is polished, the position (position in the circumferential direction) on the end face of the spirally formed core changes. The amount of change in the position of the core on the end face depends on the amount of polishing of the end face of the span multi-core fiber and the number of spirals of the core per unit length. If there is a misalignment between the cores of the two spanned multi-core fibers to be connected, there is a problem that the optical loss at the connection point (connection position) becomes large when these spanned multi-core fibers are connected. be.

The present invention has been made in view of the above circumstances, and prevents or prevents misalignment at the end face of the core that occurs when the end face of a multi-core fiber in which at least one core of a plurality of cores is formed in a spiral shape is polished. It is an object of the present invention to provide a multi-core fiber with a connector that can be relaxed.

In order to solve the above problems, the multi-core fiber with a connector according to one aspect of the present invention includes a multi-core fiber (10, 10A) in which at least one core of the plurality of cores (12) is formed in a spiral shape. The end of the multi-core fiber is provided with a connector (20, 20A, 21) provided at the end of the multi-core fiber, and the end of the multi-core fiber is a non-spiral portion (SP1) in which the core is linear, or the core. It is said that the number of spirals per unit length of the multi-core fiber is smaller than that of the portion other than the end portion of the multi-core fiber (SP2).

When the end face of the multi-core fiber with a connector according to one aspect of the present invention is polished, the non-spiral portion (the portion where the core is linear) or the loose spiral portion (the number of spirals per unit length) of the multi-core fiber is reduced. The part) will be polished. This makes it possible to prevent or alleviate the misalignment of the core on the end face that occurs when the end face is polished.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the multi-core fiber is a first multi-core fiber (FB1) in which at least one first core of the plurality of first cores (12) is formed in a spiral shape. ) And the second core (C12), each of which is optically coupled to the plurality of first cores, and is optically coupled to the first core formed in a spiral shape. The core is linear or the number of spirals per unit length is less than that of the first core formed in a spiral, and the second multi-core is the non-spiral portion or the loose spiral portion. It may be provided with a fiber (FB2).

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the first multi-core fiber and the second multi-core fiber are fused, and the connector is a combination of the first multi-core fiber and the second multi-core fiber. It may be provided at the end of the multi-core fiber so as to accommodate the fusion point (X) inside.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the plurality of first cores and the plurality of second cores, each of which is optically coupled to the first multi-core fiber and the second multi-core fiber, are used. It may be fixed to the connector in a state of being in contact with the connector.

Further, the multi-core fiber with a connector according to one aspect of the present invention may have different diameters from the plurality of first cores and the plurality of second cores.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the diameter of the clad may be different between the first multi-core fiber and the second multi-core fiber.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the first accommodating portion (H2) accommodating the first multi-core fiber of the connector and the second accommodating portion (H1) accommodating the second multi-core fiber are The inner diameter may be different.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the inner diameter of the first accommodating portion and the second accommodating portion is the size of the diameter of the clad between the first multi-core fiber and the second multi-core fiber. It may be different depending on the situation.

Further, the multi-core fiber with a connector according to one aspect of the present invention is provided at the end of the multi-core fiber so that the connector accommodates at least a part or all of the non-spiral portion or the loose spiral portion inside. You may have.

Further, in the multi-core fiber with a connector according to one aspect of the present invention, the connector may be a ferrule (21).

Here, the multi-core fiber with a connector according to one aspect of the present invention may include an alignment portion (21a to 21c) for aligning the ferrule with respect to another multi-core fiber to which the ferrule is connected.

Alternatively, the multi-core fiber with a connector according to one aspect of the present invention may include a ferrule (21) and a housing (22 to 25) for accommodating the ferrule.

Here, the multi-core fiber with a connector according to one aspect of the present invention may include an alignment portion (21c, 22a, 24a) for aligning the ferrule or the housing with respect to another multi-core fiber to which the ferrule or the housing is connected. ..

According to the present invention, there is an effect that it is possible to prevent or alleviate the misalignment at the end face of the core that occurs when the end face of the multi-core fiber in which at least one core of the plurality of cores is formed in a spiral shape is polished. be.

It is a perspective view which shows the structure of the multi-core fiber with a connector by 1st Embodiment of this invention. It is a figure for demonstrating the positional deviation in the end face of the outer peripheral core which occurs when the end face of a multi-core fiber is polished. It is a perspective perspective view which shows the structural example of the multi-core fiber in 1st Embodiment of this invention. It is a figure for demonstrating 1st manufacturing method of the multi-core fiber with a connector according to 1st Embodiment of this invention. It is a figure which shows the example of the alignment method based on the key in 1st Embodiment of this invention. It is a figure for demonstrating the 2nd manufacturing method of the multi-core fiber with a connector according to 1st Embodiment of this invention. It is a figure for demonstrating the 3rd manufacturing method of the multi-core fiber with a connector according to 1st Embodiment of this invention. It is a perspective view which shows the structure of the multi-core fiber with a connector by 2nd Embodiment of this invention. It is a perspective view which shows the structure of the multi-core fiber with a connector by the 3rd Embodiment of this invention. It is a figure for demonstrating the manufacturing method of the multi-core fiber with a connector according to the 3rd Embodiment of this invention. It is a perspective view which shows the structure of the multi-core fiber with a connector according to 4th Embodiment of this invention. It is a figure for demonstrating 1st manufacturing method of the multi-core fiber with a connector according to 4th Embodiment of this invention. It is a figure for demonstrating the 2nd manufacturing method of the multi-core fiber with a connector according to 4th Embodiment of this invention. It is a figure for demonstrating the modification of the 2nd manufacturing method of the multi-core fiber with a connector according to 4th Embodiment of this invention. It is a perspective perspective view which shows the multi-core fiber in 5th Embodiment of this invention. It is sectional drawing which shows the multi-core fiber with a connector according to the 6th Embodiment of this invention. It is sectional drawing which shows the multi-core fiber with a connector according to 7th Embodiment of this invention. It is sectional drawing which shows the multi-core fiber with a connector according to 8th Embodiment of this invention. It is sectional drawing which shows the multi-core fiber with a connector according to the 9th Embodiment of this invention, and the manufacturing method thereof. It is a figure for demonstrating the modification of the manufacturing method of the multi-core fiber with a connector according to 9th Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the multi-core fiber with a connector by 10th Embodiment of this invention.

Hereinafter, the multi-core fiber with a connector according to the embodiment of the present invention will be described in detail with reference to the drawings. In the drawings referred to below, in order to facilitate understanding, the scale of the dimensions of each member may be appropriately changed and shown.

[First Embodiment]
<Structure of multi-core fiber with connector>
FIG. 1 is a perspective view showing the configuration of a multi-core fiber with a connector according to the first embodiment of the present invention. As shown in FIG. 1, the multi-core fiber 1 with a connector according to the present embodiment includes a multi-core fiber 10 and a connector 20. In addition, in FIG. 1, in order to facilitate understanding, the multi-core fiber 10 is shown in a perspective perspective view.

The multi-core fiber 10 includes a central core 11, an outer peripheral core 12 (outer peripheral cores 12a to 12c), and a clad 13. The outer peripheral surface of the clad 13 may be covered with a coating (not shown). The central core 11 is a core formed in the center of the multi-core fiber 10 in parallel with the axis of the multi-core fiber 10. The central core 11 forms an optical path linear with respect to the longitudinal direction of the multi-core fiber 10 at the center of the multi-core fiber 10.

The central core 11 may be formed of, for example, quartz glass containing germanium (Ge). Further, an FBG (Fiber Bragg Grating) may be formed on the central core 11 over the entire length thereof. The diameter of the central core 11 is set in the range of, for example, about 5 to 7 [μm].

The outer peripheral core 12 is a core formed so as to spirally surround the circumference of the central core 11. Specifically, the outer peripheral cores 12 are separated from the central core 11 by a predetermined distance d (see FIG. 2), and are arranged at an angle θ (for example, 120 °) from each other in a cross section orthogonal to the longitudinal direction. It consists of three outer peripheral cores 12a to 12c. These outer peripheral cores 12a to 12c extend in the longitudinal direction of the multi-core fiber 10 so as to spirally surround the circumference of the central core 11 while maintaining a distance of an angle θ from each other. These outer peripheral cores 12a to 12c form three spiral optical paths surrounding the central core 11 in the multi-core fiber 10.

The outer peripheral cores 12a to 12c may be formed of, for example, quartz glass containing germanium (Ge), similarly to the central core 11. Further, FBG may be formed on the outer peripheral cores 12a to 12c over the entire length thereof. The outer peripheral cores 12a to 12c have the same diameter (or substantially the same diameter) as the central core 11, and are set in the range of, for example, about 5 to 7 [μm]. The outer peripheral cores 12a to 12c may have different diameters from the central core 11.

The distance d between the central core 11 and the outer peripheral cores 12a to 12c is the crosstalk between the cores, the optical path length difference between the central core 11 and the outer peripheral cores 12a to 12c, and the central core 11 and the outer peripheral core when the multi-core fiber 10 is bent. It is set in consideration of the difference in the amount of strain from 12a to 12c. The distance d between the central core 11 and the outer peripheral cores 12a to 12c is set to, for example, about 35 [μm]. The number of spirals of the outer peripheral cores 12a to 12c per unit length is set to, for example, about 50 [turns / m]. In other words, the length of one cycle of the outer peripheral cores 12a to 12c (more accurately, the length of the outer peripheral cores 12a to 12c in the longitudinal direction of the multi-core fiber 10 per turn) is set to about 20 [mm]. ..

The clad 13 is a common clad that covers the periphery of the central core 11 and the outer peripheral cores 12a to 12c and has a cylindrical outer diameter. Since the central core 11 and the outer peripheral cores 12a to 12c are covered with the common clad 13, it can be said that the central core 11 and the outer peripheral cores 12a to 12c are formed inside the clad 13. The clad 13 may be formed of, for example, quartz glass.

The end of the multi-core fiber 10 is a non-spiral portion SP1 in which the outer peripheral cores 12a to 12c are linearized. The reason for providing such a non-spiral portion SP1 is to prevent misalignment (positional misalignment in the circumferential direction on the end face) of the outer peripheral cores 12a to 12c when the end face of the multi-core fiber 10 is polished.

FIG. 2 is a diagram for explaining the positional deviation in the end face of the outer peripheral core that occurs when the end face of the multi-core fiber is polished. As shown in FIG. 2, consider a multi-core fiber whose end is not a non-spiral portion SP1. It is assumed that the distance between the central core 11 formed on the multi-core fiber and the outer peripheral cores 12a to 12c is d, and the length of one cycle of the outer peripheral cores 12a to 12c is L _spun .

The rotation angle α in the circumferential direction at the end faces of the outer peripheral cores 12a to 12c when the multi-core fiber shown in FIG. 2 is polished by L _porsh is represented by the following equation (1). Further, the displacement amount DP on the end faces of the outer peripheral cores 12a to 12c is expressed by the following equation (2).
α = 360 × L _porsh / L _spun … (1)
DP = 2 × d × sin (α / 2)… (2)

Here, it is assumed that the distance d between the central core 11 and the outer peripheral cores 12a to 12c is 35 [μm], and the length L _spun of one cycle of the outer peripheral cores 12a to 12c is 20 [mm]. Then, when the end face polishing amount L _polsh is 10 [μm], the misalignment amount DP becomes 0.11 [μm], and when the end face polishing amount L _polsh is 30 [μm], the misalignment amount DP becomes 30 [μm]. The amount DP is 0.55 [μm]. For example, when it is necessary to suppress the amount of misalignment DP due to end face polishing to within, for example, 0.2 [μm], a polishing accuracy on the order of 10 [μm] is required in the step of performing end face polishing of a multi-core fiber. ..

As described above, when the end portion of the multi-core fiber having the spiral outer peripheral cores 12a to 12c is not the non-spiral portion SP1, high polishing accuracy is required. The end of the multi-core fiber 10 of the present embodiment is a non-spiral portion SP1, and the outer peripheral cores 12a to 12c of the non-spiral portion SP1 are linearized together with the central core 11. Therefore, as long as the non-spiral portion SP1 is polished, the positional deviation on the end faces of the outer peripheral cores 12a to 12c described with reference to FIG. 2 basically does not occur, so that high polishing accuracy is required in the polishing step. not.

FIG. 3 is a perspective perspective view showing a configuration example of the multi-core fiber according to the first embodiment of the present invention. The multi-core fiber 10 exemplified in FIG. 3 is a fusion of a multi-core fiber FB1 (first multi-core fiber) and a multi-core fiber FB2 (second multi-core fiber). The multi-core fiber FB1 includes a central core 11 formed parallel to the axis of the multi-core fiber FB1, an outer peripheral core 12 (outer peripheral cores 12a to 12c) formed so as to spirally surround the center core 11, and a cladding. 13 is provided. The multi-core fiber FB1 occupies the main part of the multi-core fiber 10.

The multi-core fiber FB2 includes a central core C11 formed parallel to the axis of the multi-core fiber FB2, an outer peripheral core C12 (outer peripheral cores C12a to C12c) formed parallel to the central core C11 around the central core C11, and a cladding. It is equipped with C13. The central core C11 corresponds to the central core 11 of the multi-core fiber FB1, and the outer peripheral cores C12a to C12c correspond to the outer peripheral cores 12a to 12c of the multi-core fiber FB1, respectively.

The multi-core fiber FB1 and the multi-core fiber FB2 are fused so that the central core 11 and the outer peripheral cores 12a to 12c of the multi-core fiber FB1 and the central core C11 and the outer peripheral cores C12a to C12c of the multi-core fiber FB2 are optically coupled to each other. Will be done. In this way, a multi-core fiber 10 having a non-spiral portion SP1 in which the outer peripheral cores 12a to 12c are linearized at the end portion is obtained.

The connector 20 includes a ferrule 21 and a housing 22, and is provided at the end of the multi-core fiber 10. The ferrule 21 is an annular pillar-shaped member having a fiber hole into which the multi-core fiber 10 is inserted. The housing 22 is a substantially rectangular parallelepiped member that houses the ferrule 21. The housing 22 is formed with a key 22a (alignment portion) for alignment with respect to other multi-core fibers while preventing erroneous connection to other multi-core fibers to be connected. The positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are aligned with respect to the key 22a formed on the housing 22.

Here, the ferrule 21 is fixed to the end of the multi-core fiber 10 so that one end side is flush with (or substantially flush with) the end face of the multi-core fiber 10 and is integrated with the multi-core fiber 10. The ferrule 21 is axially movable but is housed in the housing 22 so as not to rotate around the axis. Since the ferrule 21 is housed in the housing 22 so as not to rotate around the shaft, the multi-core fiber 10 fixed to be integral with the ferrule 21 also does not rotate around the shaft.

As shown in FIG. 1 (a), the length of the non-spiral portion SP1 of the multi-core fiber 10 may be such that the entire non-spiral portion SP1 is accommodated in the connector 20, and is shown in FIG. 1 (b). As shown, the length may be such that only a part of the non-spiral portion SP1 is accommodated in the connector 20. When the length of the non-spiral portion SP1 of the multi-core fiber 10 is set to the length shown in FIG. 1 (a), the fusion point of the multi-core fiber 10 (the fusion of the multi-core fibers FB1 and FB2 shown in FIG. 3). Since the landing point) is housed in the connector 20, it is advantageous in terms of strength.

<Manufacturing method of multi-core fiber with connector>
<< First manufacturing method >>
FIG. 4 is a diagram for explaining a first manufacturing method of a multi-core fiber with a connector according to the first embodiment of the present invention. First, as shown in FIG. 4A, a step of preparing a multi-core fiber 10, a ferrule 21, and a housing 22 and temporarily assembling the multi-core fiber with a connector is performed. Specifically, a step is performed in which the end portion of the multi-core fiber 10 is inserted into a fiber hole formed in the ferrule 21, and the ferrule 21 in which the multi-core fiber 10 is inserted is housed in the housing 22.

Here, the multi-core fiber 10 is made rotatable around the axis. For example, the multi-core fiber 10 is not fixed to the ferrule 21 and only the multi-core fiber 10 is rotatable around the axis. Alternatively, the multi-core fiber 10 is fixed to the ferrule 21 so that the multi-core fiber 10 and the ferrule 21 are integrally rotatable about the axis. In the former case, the ferrule 21 is housed in the housing 22 so as not to rotate around the axis. In the latter case, the ferrule 21 is housed in the housing 22 so that it can rotate around an axis.

Next, as shown in FIG. 4B, a step of aligning the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 is performed. Specifically, only the multi-core fiber 10 is rotated around the shaft, or the multi-core fiber 10 and the ferrule 21 are integrally rotated around the shaft, and the multi-core fiber 10 is based on the key 22a formed on the housing 22. A step of aligning the positions of the outer peripheral cores 12a to 12c on the end face of the is performed.

FIG. 5 is a diagram showing an example of a key-based alignment method according to the first embodiment of the present invention. As the centering method shown in FIG. 5A, a camera CM or a microscope (not shown) is used, and the multi-core fiber 10 is formed while observing an image of the end face of the multi-core fiber 10 and the key 22a of the housing 22 taken by the camera CM or the like. It is a method of aligning by rotating.

The centering method shown in FIG. 5B is a method of centering using a multi-core fiber MS with a connector as a master and an optical power meter PM. Specifically, the power of light propagating from the master multi-core fiber MS with a connector to the temporarily assembled multi-core fiber by connecting the multi-core fiber MS with a connector to be a master and the multi-core fiber with a temporarily assembled connector. Is a method of aligning by monitoring while rotating the multi-core fiber 10. In this method, the key 22a of the multi-core fiber MS with a connector to be a master and the key 22a of the temporarily assembled multi-core fiber with a connector are accurately aligned by using an adapter or the like.

In the alignment method shown in FIG. 5B, one optical power meter PM may be used to monitor the total power of light propagating through each core, and a plurality of optical power meter PMs may be used to monitor each core. The power of propagating light may be monitored individually. Alternatively, an optical switch may be used to switch the cores that propagate the light, and the power of the light propagating through each core may be sequentially monitored. It should be noted that the cores that propagate light may be limited to one or two specific cores, and only the power of light propagating through these limited cores may be monitored.

Subsequently, as shown in FIG. 4C, a step of fixing the multi-core fiber 10 is performed. For example, in the step shown in FIG. 4A, when only the multi-core fiber 10 is made rotatable around the shaft, for example, a step of fixing the multi-core fiber 10 to the ferrule 21 using an adhesive is performed. .. Alternatively, in the step shown in FIG. 4A, when the multi-core fiber 10 and the ferrule 21 are integrally rotatable around the shaft, the ferrule 21 is housed in the housing 22 so as not to rotate around the shaft. The process is carried out. When this step is performed, the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are fixed with reference to the key 22a formed on the housing 22.

Subsequently, as shown in FIG. 4D, a step of polishing the end face of the multi-core fiber 10 is performed. Specifically, the end surface of the multi-core fiber 10 (one end side of the ferrule 21) is brought into contact with the polishing surface so that the axis of the multi-core fiber 10 is perpendicular to the polishing surface of the polishing apparatus PD, and the multi-core fiber 10 is formed. A step of polishing the end face is performed. For polishing in this step, for example, PC (Physical Contact) polishing, SPC (Super Physical Contact), and UPC (Ultra Physical Contact) polishing can be used.

The end faces of the multi-core fibers 10 may be polished one by one, or a plurality of them may be polished at the same time. By simultaneously polishing the end faces of the multi-core fiber 10, the time can be shortened, which is efficient. Through the above steps, the multi-core fiber 1 with a connector is manufactured. Finally, a step of inspecting the manufactured multi-core fiber 1 with a connector is performed.

<< Second manufacturing method >>
FIG. 6 is a diagram for explaining a second method of manufacturing a multi-core fiber with a connector according to the first embodiment of the present invention. First, as shown in FIG. 6A, a step of preparing the multi-core fiber 10 and the ferrule 21 and fixing the ferrule 21 to the end of the multi-core fiber 10 is performed. For example, an adhesive is used to fix the ferrule 21 to the multi-core fiber 10.

Next, as shown in FIG. 6B, a step of polishing the end faces of the ferrule 21 and the multi-core fiber 10 is performed. Specifically, as in the process shown in FIG. 4D, the end face of the multi-core fiber 10 (one end of the ferrule 21) so that the axis of the multi-core fiber 10 is perpendicular to the polishing surface of the polishing apparatus PD. The step of polishing the end face of the multi-core fiber 10 by bringing the side) into contact with the polishing surface is performed. Similar to the process shown in FIG. 4D, the end face polishing of the multi-core fiber 10 may be performed one by one, or may be performed at the same time.

Subsequently, the ferrule 21 is housed in the housing 22 so as to be rotatable around the axis, and as shown in FIG. 6 (c), the steps of aligning the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are performed. Will be. Specifically, the multi-core fiber 10 and the ferrule 21 are integrally rotated around the shaft, and the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are aligned with respect to the key 22a formed on the housing 22. The process is carried out. As the specific alignment method in this step, the one described with reference to FIG. 5 can be used.

Subsequently, a step of accommodating the ferrule 21 in the housing 22 so as not to rotate around the shaft is performed. When this step is performed, the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are fixed with reference to the key 22a formed on the housing 22. Through the above steps, the multi-core fiber 1 with a connector is manufactured. Finally, a step of inspecting the manufactured multi-core fiber 1 with a connector is performed.

<< Third manufacturing method >>
FIG. 7 is a diagram for explaining a third method for manufacturing a multi-core fiber with a connector according to the first embodiment of the present invention. The manufacturing method shown in FIG. 7 is a case where the housing 22 is composed of the inner housing 23 and the outer housing 24. The manufacturing method shown in FIG. 7 is basically the same as the manufacturing method shown in FIG.

First, as shown in FIG. 7A, a step of preparing a multi-core fiber 10, a ferrule 21, and an internal housing 23 and temporarily assembling them is performed. Here, the multi-core fiber 10 is made rotatable around a shaft, as in the first manufacturing method. For example, the multi-core fiber 10 is not fixed to the ferrule 21 and only the multi-core fiber 10 is rotatable around the axis. Alternatively, the multi-core fiber 10 is fixed to the ferrule 21 so that the multi-core fiber 10 and the ferrule 21 are integrally rotatable about the axis. In the former case, the ferrule 21 is housed in the inner housing 23 so as not to rotate around the axis. In the latter case, the ferrule 21 is housed in the inner housing 23 so that it can rotate around an axis.

Next, as shown in FIG. 7B, a step of aligning the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 is performed. This step is the same as the configuration shown in FIG. 4 (b). However, the alignment of the positions of the outer peripheral cores 12a to 12c is performed with reference to the temporary key. As the temporary key, for example, the corner portion K of the inner housing 23 can be used. As the specific alignment method in this step, the one described with reference to FIG. 5 can be used.

Next, a step of fixing the multi-core fiber 10 is performed. This step is the same as the step shown in FIG. 4 (c). By performing this step, the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber 10 are fixed with reference to the corner portion K (temporary key) of the inner housing 23. Subsequently, a step of polishing the end face of the multi-core fiber 10 (a step similar to the step shown in FIG. 4D) is performed, and then, as shown in FIG. 7B, the inner housing 23 is attached to the outer housing 24. The process of accommodating is carried out. Alternatively, as shown in FIG. 7B, a step of accommodating the inner housing 23 in the outer housing 24 is performed, and then a step of polishing the end face of the multi-core fiber 10 (similar to the step shown in FIG. 4D). Step) is performed.

Here, in the state where the inner housing 23 is housed in the outer housing 24, the positional relationship between the corner portion K of the inner housing 23 used as a temporary key and the key 24a formed in the outer housing 24 does not change. Therefore, as a key that serves as a reference for the positions of the outer peripheral cores 12a to 12c, a key 24a formed on the outer housing 24 can be used instead of the corner portion K (temporary key) of the inner housing 23.

As described above, in the present embodiment, the end of the multi-core fiber 10 having the outer peripheral core 12 formed so as to spirally surround the central core 11 is referred to as the non-spiral portion SP1. , The outer peripheral core 12 is made linear like the central core 11. A connector 20 is provided at the end of the multi-core fiber 10 which is the non-spiral portion SP1. Therefore, even if the end face of the multi-core fiber 10 to which the connector 20 is attached is polished, the positional deviation on the end faces of the outer peripheral cores 12a to 12c can be eliminated (almost eliminated).

[Second Embodiment]
<Structure of multi-core fiber with connector>
FIG. 8 is a perspective view showing the configuration of a multi-core fiber with a connector according to the second embodiment of the present invention. In FIG. 8, the same reference numerals are given to the configurations similar to those shown in FIG. As shown in FIG. 8, the multi-core fiber 2 with a connector according to the present embodiment includes the multi-core fiber 10A instead of the multi-core fiber 10 shown in FIG. In FIG. 8, as in FIG. 1, the multi-core fiber 10A is shown in a perspective perspective view for ease of understanding.

Similar to the multi-core fiber 10 shown in FIG. 1, the multi-core fiber 10A includes a central core 11, an outer peripheral core 12 (outer peripheral cores 12a to 12c), and a clad 13. However, unlike the multi-core fiber 10 shown in FIG. 1, the end portion of the multi-core fiber 10A is a loose spiral portion SP2 in which the outer peripheral cores 12a to 12c are gently spiraled. The reason why such a gentle spiral portion SP2 is provided is to alleviate the occurrence of misalignment on the end faces of the outer peripheral cores 12a to 12c (positional misalignment in the circumferential direction on the end face) when the end face of the multi-core fiber 10A is polished.

Here, the number of spirals per unit length of the outer peripheral cores 12a to 12c in the loose spiral portion SP2 is smaller than the number of spirals per unit length of the outer peripheral cores 12a to 12c in the portions other than the loose spiral portion SP2. .. For example, the number of spirals per unit length of the outer peripheral cores 12a to 12c in the loose spiral portion SP2 is set to half or less of the number of spirals per unit length of the outer peripheral cores 12a to 12c in the portion other than the loose spiral portion SP2. ..

The multi-core fiber 10A is formed by fusing two types of multi-core fibers in the same manner as the multi-core fiber 10 shown in FIG. Specifically, it is formed by fusing the multi-core fiber FB1 shown in FIG. 3 and the multi-core fiber FB2 in which the outer peripheral cores C12 (outer peripheral cores C12a to C12c) are gently spiraled. In the present embodiment, the central core 11 and the outer peripheral cores 12a to 12c of the multi-core fiber FB1 and the central core C11 of the multi-core fiber FB2 and the outer peripheral cores C12a to C12c formed in a gentle spiral are optically coupled to each other. Be made to do. In this way, a multi-core fiber 10A having a loose spiral portion SP2 in which the outer peripheral cores 12a to 12c are gently spiraled at the end portions can be obtained.

<Manufacturing method of multi-core fiber with connector>
The manufacturing method of the multi-core fiber 2 with a connector according to the present embodiment is the same as that of the first embodiment, except that the multi-core fiber 10A is provided in place of the multi-core fiber 10 shown in FIG. Therefore, the description of the manufacturing method of the multi-core fiber 2 with a connector will be omitted.

As described above, in the present embodiment, the end of the multi-core fiber 10A having the outer peripheral core 12 formed so as to spirally surround the central core 11 is the loose spiral portion SP2, and the loose spiral portion SP2. The number of spirals per unit length of the outer peripheral core 12 is smaller than the number of spirals per unit length of the outer peripheral core 12 in the portion other than the loose spiral portion SP2. A connector 20 is provided at the end of the multi-core fiber 10A, which is the gentle spiral portion SP2. Therefore, even if the end face of the multi-core fiber 10A to which the connector 20 is attached is polished, the positional deviation on the end faces of the outer peripheral cores 12a to 12c can be reduced (alleviated).

[Third Embodiment]
<Structure of multi-core fiber with connector>
FIG. 9 is a perspective view showing the configuration of a multi-core fiber with a connector according to a third embodiment of the present invention. In FIG. 9, the same reference numerals are given to the configurations similar to those shown in FIGS. 1 and 8. As shown in FIG. 9, in the multi-core fiber 3 with a connector according to the present embodiment, the end faces of the multi-core fibers 10 and 10A are APC (Angled Physical Contact) polished (for example, diagonally polished by a predetermined angle (for example, 8 degrees)). ) Is different from the multi-core fibers 1 and 2 with connectors shown in FIGS. 1 and 8. In the present embodiment, the end face 21c of the APC-polished ferrule 21 is used as a so-called key (alignment portion).

In the multi-core fiber 3 with a connector shown in FIG. 9A, the same connector 20 (connector 20 including the ferrule 21 and the housing 22 on which the key 22a is formed) as shown in FIGS. 1 and 8 is the multi-core fiber 10, 10A. It is provided at the end of the. In the multi-core fiber 3 with a connector shown in FIG. 9B, a connector 20A including a ferrule 21 and an annular pillar-shaped housing 25 on which a key is not formed is provided at an end portion of the multi-core fibers 10 and 10A.

<Manufacturing method of multi-core fiber with connector>
FIG. 10 is a diagram for explaining a method for manufacturing a multi-core fiber with a connector according to a third embodiment of the present invention. Here, a method of manufacturing the multi-core fiber 3 with a connector shown in FIG. 9A will be described as an example. The temporary assembly process shown in FIG. 10 (a), the centering process shown in FIG. 10 (b), and the fixing process shown in FIG. 10 (c) are shown in FIGS. 4 (a), 4 (b), and 4 (c). The same as that shown in FIG. 10 (d), but the polishing step shown in FIG. 10 (d) is different from that shown in FIG. 4 (e).

In this embodiment, as shown in FIG. 10D, the multi-core fiber has a predetermined angle φ (for example, 8 degrees) with respect to the perpendicular line of the polishing surface of the polishing apparatus PD so that the axes of the multi-core fibers 10 and 10A form a predetermined angle φ (for example, 8 degrees). A step of polishing the end face of the multi-core fiber 10, 10A by bringing the end face of the 10 and 10A (one end side of the ferrule 21) into contact with the polishing surface is performed. The orientation of the connector 20 is set with reference to the key 22a formed on the housing 22. For example, the one-sided SF of the housing 22 on which the key 22a is formed is set to be parallel to the surface including the shaft of the multi-core fibers 10 and 10A and the perpendicular line of the polishing surface of the polishing apparatus PD.

In order to facilitate the end face polishing of the multi-core fibers 10 and 10A, a ferrule having one end side formed diagonally (for example, formed at the same angle as the above angle φ) may be used. When such a ferrule is used, in the temporary assembly process shown in FIG. 10A, it is necessary to align the direction of the ferrule (direction around the axis) with the key 22a of the housing 22 to some extent.

As described above, the multi-core fiber 3 with a connector of the present embodiment is different from the multi-core fibers 1 and 2 with a connector of the first and second embodiments in that the end face of the multi-core fiber 10.10A is APC-polished. However, the connector 20 (20A) is provided at the end of the multi-core fibers 10 and 10A having the non-spiral portion SP1 or the loose spiral portion SP2. Therefore, even if the end faces of the multi-core fibers 10 and 10A to which the connector 20 (20A) is attached are polished, the positional deviation on the end faces of the outer peripheral cores 12a to 12c is eliminated (almost eliminated) or reduced (relaxed). can do.

[Fourth Embodiment]
<Structure of multi-core fiber with connector>
FIG. 11 is a perspective view showing the configuration of a multi-core fiber with a connector according to a fourth embodiment of the present invention. In FIG. 11, the same reference numerals are given to the configurations similar to those shown in FIGS. 1, 8, and 9. As shown in FIG. 11, in the multi-core fiber 4 with a connector according to the present embodiment, the connector 20 is composed of only the ferrule 21, and the housing 22 is omitted, that is, the connectors shown in FIGS. 1, 8, and 9. It is different from the multi-core fibers 1 to 3 with connectors.

The multi-core fiber 4 with a connector shown in FIG. 11A includes a ferrule 21 having a convex key 21a formed on a part of a side surface as a connector 20. The multi-core fiber 4 with a connector shown in FIG. 11B is provided with a ferrule 21 having a notch formed in a part of a side surface thereof and the notch being a key 21b as a connector 20.

The multi-core fiber 4 with a connector shown in FIG. 11 (c) includes a ferrule 21 having an APC-polished end face as a connector 20. In the multi-core fiber 4 with a connector shown in FIG. 11 (c), the APC-polished end face 21c is used as a so-called key (alignment portion). The multi-core fiber 4 with a connector shown in FIG. 11 (d) has a key 21a added to the ferrule 21 of the multi-core fiber 4 with a connector shown in FIG. 11 (c).

In the multi-core fiber 4 with a connector of the present embodiment, the ferrule 21 is used as a connector, but a SUS tube or a zirconia tube is used for connection with another multi-core fiber. That is, the multi-core fiber 4 with a connector of the present embodiment has a multi-core fiber with a connector by inserting the ferrule 21 into the SUS tube or the zirconia tube in a state where the core is aligned with the other multi-core fiber. Be connected.

<Manufacturing method of multi-core fiber with connector>
<< First manufacturing method >>
FIG. 12 is a diagram for explaining a first manufacturing method of a multi-core fiber with a connector according to a fourth embodiment of the present invention. The manufacturing method shown in FIG. 12 is for the multi-core fiber 4 with a connector shown in FIGS. 11 (a), 11 (b), and 11 (d) (that is, the multi-core fiber 4 with a connector in which the keys 21a and 21b are formed on the ferrule 21). It is a manufacturing method. In the following, a case of manufacturing the multi-core fiber 4 with a connector shown in FIGS. 11A and 11C will be described as an example.

First, as shown in FIG. 12A, a step of preparing a multi-core fiber 10 or a multi-core fiber 10A and a ferrule 21 and temporarily assembling a multi-core fiber with a connector is performed. Here, the multi-core fibers 10, 10A are not fixed to the ferrule 21 and are made rotatable around the axis. Next, as shown in FIG. 12B, the multi-core fibers 10 and 10A are rotated around the axis, and the outer peripheral cores 12a to 12c at the end faces of the multi-core fibers 10 and 10A are referred to the key 21a formed on the ferrule 21. The process of aligning the position of is performed. As the specific alignment method in this step, the one described with reference to FIG. 5 can be used.

Subsequently, as shown in FIG. 12 (c), a step of fixing the multi-core fibers 10 and 10A to the ferrule 21 using, for example, an adhesive is performed. As a result, the positions of the outer peripheral cores 12a to 12c on the end faces of the multi-core fibers 10 and 10A are fixed with reference to the key 21a formed on the ferrule 21. Subsequently, a step of polishing the end faces of the multi-core fibers 10 and 10A is performed.

Here, in the case of manufacturing the multi-core fiber 4 with a connector shown in FIG. 11A, the axes of the multi-core fibers 10 and 10A are set to be perpendicular to the polishing surface of the polishing apparatus PD so that the multi-core fibers 10 and 10A are perpendicular to the polishing surface. A step of polishing the end face of 10A is performed. That is, the same process as that shown in FIG. 4 (d) is performed.

On the other hand, in the case of manufacturing the multi-core fiber 4 with a connector shown in FIG. 11 (d), as shown in FIG. The step of polishing the end faces of the multi-core fibers 10 and 10A is performed so as to form a predetermined angle φ (for example, 8 degrees). At this time, the orientation of the ferrule 21 is set with reference to the key 21a, as in the process shown in FIG. 10 (d). As in the third embodiment, in order to facilitate the end face polishing of the multi-core fibers 10 and 10A, a ferrule having one end side formed diagonally may be used.

<< Second manufacturing method >>
FIG. 13 is a diagram for explaining a second method of manufacturing a multi-core fiber with a connector according to a fourth embodiment of the present invention. The manufacturing method shown in FIG. 13 is a multi-core fiber 4 with a connector shown in FIG. 11 (c) (that is, a multi-core fiber 4 with a connector in which keys 21a and 21b are not formed on the ferrule 21 and the end faces are APC-polished). It is a manufacturing method of.

First, as shown in FIG. 13A, a step of preparing a multi-core fiber 10, a multi-core fiber 10A, a ferrule 21, and a fixing jig FJ, and temporarily assembling the multi-core fiber with a connector is performed. The fixing jig FJ is the same as the housing 22 in the first and second embodiments, and the same key KY as the key 22a formed on the housing 22 is formed. Here, the multi-core fibers 10, 10A are not fixed to the ferrule 21 and are made rotatable around the axis. However, the ferrule 21 and the fixing jig FJ are temporarily fixed.

Next, as shown in FIG. 13 (b), the multi-core fibers 10 and 10A are rotated around the axis, and the outer peripheral core 12a on the end face of the multi-core fibers 10 and 10A is referred to the key KY formed on the fixing jig FJ. A step of aligning the positions of ~ 12c is performed. As the specific alignment method in this step, the one described with reference to FIG. 5 can be used.

Subsequently, as shown in FIG. 13 (c), a step of fixing the multi-core fibers 10 and 10A to the ferrule 21 using, for example, an adhesive is performed. As a result, the positions of the outer peripheral cores 12a to 12c on the end faces of the multi-core fibers 10 and 10A are fixed with reference to the key KY formed on the fixing jig FJ.

Subsequently, as shown in FIG. 13D, a step of polishing the end faces of the multi-core fibers 10 and 10A is performed. Specifically, the end faces of the multi-core fibers 10 and 10A are polished so that the axes of the multi-core fibers 10 and 10A form a predetermined angle φ (for example, 8 degrees) with respect to the perpendicular line of the polishing surface of the polishing device PD. The process is carried out. At this time, the orientation of the fixing jig FJ is set with reference to the key KY formed on the fixing jig FJ, as in the process shown in FIG. 10 (d). As in the third embodiment, in order to facilitate the end face polishing of the multi-core fibers 10 and 10A, a ferrule having one end side formed diagonally may be used.

When the above steps are completed, a step of inspecting the multi-core fiber 4 with a connector is performed with the fixing jig FJ attached. Finally, a step of removing the fixing jig FJ temporarily fixed to the ferrule 21 is performed. Through the above steps, the multi-core fiber 4 with a connector shown in FIG. 11C is manufactured.

FIG. 14 is a diagram for explaining a modification of the second manufacturing method of the multi-core fiber with a connector according to the fourth embodiment of the present invention. In the manufacturing method shown in FIG. 13, in the step shown in FIG. 13A, the multi-core fibers 10 and 10A were not fixed to the ferrule 21, but the ferrule 21 was temporarily fixed to the fixing jig FJ. On the other hand, in this modification, the multi-core fibers 10 and 10A are fixed to the ferrule 21, and the ferrule 21 is not fixed to the fixing jig FJ.

First, as shown in FIG. 14A, for example, a step of fixing the multi-core fibers 10 and 10A to the ferrule 21 using an adhesive is performed. Next, as shown in FIG. 14B, a step of inserting the ferrule 21 to which the multi-core fibers 10 and 10A are fixed into the fixing jig FJ is performed. Here, the ferrule 21 is not fixed to the fixing jig FJ. Therefore, the multi-core fibers 10, 10A and the ferrule 21 can rotate around the shaft as a unit.

Subsequently, as shown in FIG. 14 (c), the multi-core fibers 10 and 10A are rotated around the axis, and the outer peripheral core 12a on the end face of the multi-core fibers 10 and 10A is referred to the key KY formed on the fixing jig FJ. A step of aligning the positions of ~ 12c is performed. When the alignment is completed, a step of temporarily fixing the ferrule 21 and the fixing jig FJ is performed. As a result, the positions of the outer peripheral cores 12a to 12c on the end faces of the multi-core fibers 10 and 10A are fixed with reference to the key KY formed on the fixing jig FJ.

Subsequently, as shown in FIG. 14D, a step of polishing the end faces of the multi-core fibers 10 and 10A is performed. This step is the same as the step shown in FIG. 13 (d). When the above steps are completed, a step of inspecting the multi-core fiber 4 with a connector is performed with the fixing jig FJ attached. Finally, a step of removing the fixing jig FJ temporarily fixed to the ferrule 21 is performed. Through the above steps, the multi-core fiber 4 with a connector shown in FIG. 11C is manufactured.

As described above, the multi-core fiber 4 with a connector of the present embodiment is different from the multi-core fibers 1 to 3 with a connector of the first to third embodiments in that the ferrule 21 has the connector 20 but is not. A connector 20 is provided at the end of the multi-core fibers 10 and 10A having the spiral portion SP1 or the loose spiral portion SP2. Therefore, even if the end faces of the multi-core fibers 10 and 10A to which the connector 20 is attached are polished, the positional deviation on the end faces of the outer peripheral cores 12a to 12c should be eliminated (almost eliminated) or reduced (alleviated). Can be done. Further, in the present embodiment, since the ferrule 21 is the connector 20 and the housing (for example, the housing 22) is omitted, the connector 20 can be miniaturized.

[Fifth Embodiment]
FIG. 15 is a perspective perspective view showing the multi-core fiber according to the fifth embodiment of the present invention. As shown in FIG. 15, in the multi-core fiber 10 in the present embodiment, the core dimension (MFD: Mode Field Diameter) in the non-spiral portion SP1 is larger than the core dimension in the portion other than the non-spiral portion SP1. ing. Such a multi-core fiber 10 is obtained, for example, by fusing the multi-core fiber FB1 shown in FIG. 3 and the multi-core fiber FB2 (the center core C11 and the outer peripheral cores C12a to C12c having a large diameter).

As described above, by making the size of the core in the non-spiral portion SP1 larger than the size of the core in the portion other than the non-spiral portion SP1, there are some dimensional errors and positional errors in the cores of the multi-core fibers FB1 and FB2. However, the light loss at the fusion point X can be reduced. When the multi-core fiber 10 in this embodiment is used in OFDR (Optical Frequency Domain Reflectometry), the level of Rayleigh scattered light changes before and after the fusion point X, so that the level of Rayleigh scattered light changes in the sensing region. There is an advantage that the start position can be easily detected and the measurement position accuracy in the longitudinal direction of the sensor can be prevented from deteriorating.

In the present embodiment, the case where the core dimension in the non-spiral portion SP1 of the multi-core fiber 10 is larger than the core dimension in the portion other than the non-spiral portion SP1 is taken as an example. However, the size of the core in the loose spiral portion SP2 of the multi-core fiber 10A may be larger than the size of the core in the portion other than the loose spiral portion SP2. Further, the size of the core in the non-spiral portion SP1 or the loose spiral portion SP2 may be formed smaller than the size of the core in the non-spiral portion SP1 or the loose spiral portion SP2.

[Sixth Embodiment]
FIG. 16 is a cross-sectional view showing a multi-core fiber with a connector according to a sixth embodiment of the present invention. As shown in FIG. 16, in the present embodiment, the ferrule 21 has a two-stage inner diameter of the accommodating portion for accommodating the multi-core fiber 10. Specifically, the ferrule 21 has an accommodating portion H1 (second accommodating portion) having an inner diameter formed to be approximately the same as the outer diameter of the multi-core fiber 10, and an accommodating portion H2 having an inner diameter larger than that of the accommodating portion H1. It has a first housing unit).

As shown in FIG. 16A, the inner diameter may gradually change (tapered) between the accommodating portion H1 and the accommodating portion H2, and as shown in FIG. 16B, the inner diameter is steep. It may change (in steps). As described above, the reason why the accommodation portions H1 and H2 having different diameters are formed in the ferrule 21 is to accommodate the fusion point X (the portion having a larger diameter) of the multi-core fiber 10 inside the ferrule 21.

Since the ferrules 21 are formed with accommodating portions H1 and H2 having different diameters, when the multi-core fiber 10 is inserted into the ferrule 21, the fusion point X is engaged between the accommodating portions H1 and the accommodating portions H2. It will be stopped. In the example shown in FIG. 16A, the fusion point X is locked to the tapered portion, and in the example shown in FIG. 16B, the fusion point X is located in the stepped portion. Locked. This has the advantage that the fusion point X can be positioned within the ferrule 21. Further, when it is used for a sensor using OFDR, there is an advantage that deterioration of measurement position accuracy in the longitudinal direction can be prevented. It should be noted that this embodiment can be applied to any of the above-mentioned first to fifth embodiments.

[7th Embodiment]
FIG. 17 is a cross-sectional view showing a multi-core fiber with a connector according to a seventh embodiment of the present invention. As shown in FIG. 17, in the multi-core fiber 10 in the present embodiment, the clad diameter in the non-spiral portion SP1 is larger than the clad diameter in the portion other than the non-spiral portion SP1. In this way, the clad diameter in the non-spiral portion SP1 is made larger than the clad diameter in the portion other than the non-spiral portion SP1, as in the ferrule 21 of the sixth embodiment, the inner diameter of the accommodating portion is made into two stages. This is to accommodate the fusion point X of the multi-core fiber 10 inside the ferrule 21 without doing so.

As shown in FIG. 17, even if the multi-core fibers FB1 and FB2 having different clad diameters are fused, the clad diameter at the fusion point X of the multi-core fiber 10 obtained by fusion is larger than the clad diameter of the multi-core fiber FB1. It doesn't get bigger. Therefore, if the ferrule 21 having an inner diameter similar to the clad diameter of the multi-core fiber FB 1 is used, the fusion point X of the multi-core fiber 10 can be accommodated inside the ferrule 21 without having to make the inner diameter of the accommodating portion into two stages. Can be done.

In the present embodiment, the case where the clad diameter in the non-spiral portion SP1 of the multi-core fiber 10 is larger than the clad diameter in the portion other than the non-spiral portion SP1 is taken as an example. However, the clad diameter in the loose spiral portion SP2 of the multi-core fiber 10A may be larger than the clad diameter in the portion other than the loose spiral portion SP2.

[Eighth Embodiment]
FIG. 18 is a cross-sectional view showing a multi-core fiber with a connector according to an eighth embodiment of the present invention. As shown in FIG. 18, the multi-core fiber with a connector in the present embodiment includes a multi-core fiber 10 having portions having different clad diameters, and a ferrule 21 having a two-stage inner diameter of the accommodating portion.

The multi-core fiber 10 in the present embodiment is different from the multi-core fiber 10 (see FIG. 17) of the seventh embodiment described above, and the clad diameter in the non-spiral portion SP1 is smaller than the clad diameter in the portion other than the non-spiral portion SP1. It is said that. The ferrule 21 in this embodiment is the same as that in the sixth embodiment described above. That is, it has an accommodating portion H1 having an inner diameter formed to be the same as the outer diameter of the non-spiral portion SP1 of the multi-core fiber 10, and an accommodating portion H2 having an inner diameter formed to be larger than the accommodating portion H1. That is, in the present embodiment, the inner diameters of the accommodating portions H1 and H2 differ depending on the clad diameter of the multi-core fiber 10 to be inserted (the clad diameter of the multi-core fibers FB1 and FB2).

When such a multi-core fiber 10 is inserted into the ferrule 21, the fusion point X of the multi-core fiber 10 is locked between the accommodating portion H1 and the accommodating portion H2 of the ferrule 21. This has the advantage that the fusion point X can be positioned within the ferrule 21. Further, when it is used for a sensor using OFDR, there is an advantage that deterioration of measurement position accuracy in the longitudinal direction can be prevented. It should be noted that this embodiment can be applied to any of the above-mentioned first to fifth embodiments.

[9th Embodiment]
FIG. 19 is a cross-sectional view showing a multi-core fiber with a connector according to a ninth embodiment of the present invention and a method for manufacturing the same. As shown in FIG. 19D, the multi-core fiber with a connector according to the present embodiment includes a multi-core fiber 10 composed of multi-core fibers FB1 and FB2 having different clad diameters, and a ferrule 21 having accommodating portions H1 and H2 having different inner diameters. To prepare for. The multi-core fibers FB1 and FB2 forming the multi-core fiber 10 are not fused, and the ferrule is in a state where the end faces are in contact with each other (in a state where each core of the multi-core fiber FB1 and each core of the multi-core fiber FB2 are in contact with each other). It is fixed at 21.

In the present embodiment, the clad diameter of the multi-core fiber FB2, which is the non-spiral portion SP1 of the multi-core fiber 10, is made larger than the clad diameter of the multi-core fiber FB1, which is a portion other than the non-spiral portion SP1 of the multi-core fiber 10. There is. Further, the inner diameter of the accommodating portion H1 of the ferrule 21 is formed to be about the same as the clad diameter of the multi-core fiber FB2, and the inner diameter of the accommodating portion H2 is formed to be about the same as the clad diameter of the multi-core fiber FB1. That is, the inner diameters of the accommodating portions H1 and H2 differ depending on the clad diameter of the inserted multi-core fiber 10 (the clad diameter of the multi-core fibers FB1 and FB2).

When manufacturing the multi-core fiber with a connector of the present embodiment, first, the ferrule 21 shown in FIG. 19 (a) is prepared, and as shown in FIG. 19 (b), the multi-core fiber FB2 is used in the accommodating portion H1 of the ferrule 21. The process of interpolation is performed. Here, since the inner diameter of the accommodating portion H2 of the ferrule 21 is formed to be smaller than the inner diameter of the accommodating portion H1, the end face of the multi-core fiber FB2 inserted in the accommodating portion H1 is the boundary between the accommodating portions H1 and H2. Locked with. Next, for example, a step of fixing the multi-core fiber FB2 inserted in the accommodating portion H1 to the ferrule 21 using an adhesive is performed.

Subsequently, as shown in FIG. 19C, a step of interpolating the multi-core fiber FB1 into the accommodating portion H2 of the ferrule 21 is performed. Here, the end face of the multi-core fiber FB1 inserted in the accommodating portion H1 of the ferrule 21 is in contact with the end face of the multi-core fiber FB2 fixed to the ferrule 21. Subsequently, a step of rotating the multi-core fiber FB1 around an axis to align the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber FB1 is performed. When the alignment is completed, for example, a step of fixing the multi-core fiber FB1 inserted in the accommodating portion H2 to the ferrule 21 by using an adhesive is performed. When the above steps are completed, as shown in FIG. 19D, a step of polishing the end faces of the ferrule 21 and the multi-core fiber FB2 is performed.

In this embodiment, an example in which the clad diameters of the multi-core fibers FB1 and FB2 forming the multi-core fiber 10 are different and the inner diameters of the accommodating portions H1 and H2 in the ferrule 21 are different has been described. However, the clad diameters of the multi-core fibers FB1 and FB2 forming the multi-core fiber 10 are the same, and the inner diameters of the accommodating portions H1 and H2 in the ferrule 21 are the same (that is, the inner diameters of the accommodating portions of the ferrule 21 are not made into two stages). It may be.

FIG. 20 is a diagram for explaining a modified example of the method for manufacturing a multi-core fiber with a connector according to a ninth embodiment of the present invention. First, as shown in FIG. 20A, a step of inserting and fixing the multi-core fiber FB2 into the ferrule 21 is performed. Here, when the inner diameters of the accommodating portions H1 and H2 in the ferrule 21 are different, the end faces of the multi-core fiber FB2 are locked at the boundary between the accommodating portions H1 and H2, as in the step shown in FIG. 19B. It is inserted into the ferrule 21 until it is done. On the other hand, when the inner diameter of the accommodating portion of the ferrule 21 is not set in two stages, it is necessary to adjust the insertion amount of the multi-core fiber FB2 into the accommodating portion of the ferrule 21.

Next, as shown in FIG. 20B, a step of polishing the end faces of the ferrule 21 and the multi-core fiber FB2 is performed. Subsequently, as shown in FIG. 20 (c), a step of interpolating the multi-core fiber FB1 into the ferrule 21 is performed. Here, the multi-core fiber FB1 is inserted into the ferrule 21 until the end face abuts on the end face of the multi-core fiber FB2.

Subsequently, as shown in FIG. 20 (d), a step of rotating the multi-core fiber FB1 around an axis to align the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber FB1 is performed. In this step, for example, in a state where light is emitted from the multi-core fiber FB1 toward the multi-core fiber FB2, the light emitted from the other end of the multi-core fiber FB2 is emitted while rotating the multi-core fiber FB1 around an axis. A centering method monitored by a power meter PM is used. When the alignment is completed, for example, a step of fixing the multi-core fiber FB1 interpolated in the ferrule 21 to the ferrule 21 by using an adhesive is performed. It should be noted that this embodiment can be applied to any of the above-mentioned first to fifth embodiments.

[10th Embodiment]
FIG. 21 is a cross-sectional view showing a method of manufacturing a multi-core fiber with a connector according to the tenth embodiment of the present invention. The multi-core fiber with a connector of the present embodiment is different from the multi-core fiber with a connector according to the ninth embodiment in that the ends of the multi-core fiber FB2 and the ferrule 21 are APC-polished.

When manufacturing the multi-core fiber with a connector of the present embodiment, first, as shown in FIG. 21A, a step of inserting and fixing the multi-core fiber FB2 into the ferrule 21 is performed. The process shown in FIG. 21 (a) is the same as the process shown in FIG. 20 (a). Next, as shown in FIG. 21B, a step of polishing the end faces of the ferrule 21 and the multi-core fiber FB2 is performed. The process shown in FIG. 21 (b) is the same as the process shown in FIG. 20 (b).

Next, as shown in FIG. 21 (c), a step of inserting the ferrule 21 in which the multi-core fiber FB2 is fixed and the end face is polished is inserted into the fixing jig FJ is performed. Here, the ferrule 21 is not fixed to the fixing jig FJ. Therefore, the multi-core fiber FB2 and the ferrule 21 can rotate around the axis as a unit.

Subsequently, as shown in FIG. 21 (d), the multi-core fiber FB2 and the ferrule 21 are rotated around the axis, and the outer peripheral cores 12a to the outer peripheral core 12a on the end face of the multi-core fiber FB2 are referred to with reference to the key KY formed on the fixing jig FJ. A step of aligning the position of 12c is performed. When the alignment is completed, a step of temporarily fixing the ferrule 21 and the fixing jig FJ is performed. As a result, the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber FB2 are fixed with reference to the key KY formed on the fixing jig FJ.

Subsequently, as shown in FIG. 21 (e), a step of polishing (APC polishing) the end faces of the multi-core fiber FB2 and the ferrule 21 is performed. When the end face polishing is completed, the step of removing the fixing jig FJ is performed. Subsequently, as shown in FIG. 21 (f), a step of interpolating the multi-core fiber FB1 into the ferrule 21 is performed. Here, the multi-core fiber FB1 is inserted into the ferrule 21 until the end face abuts on the end face of the multi-core fiber FB2.

Subsequently, as shown in FIG. 21 (g), a step of rotating the multi-core fiber FB1 around an axis to align the positions of the outer peripheral cores 12a to 12c on the end face of the multi-core fiber FB1 is performed. This step is the same as the step shown in FIG. 20 (d). When the alignment is completed, for example, a step of fixing the multi-core fiber FB1 interpolated in the ferrule 21 to the ferrule 21 by using an adhesive is performed. It should be noted that this embodiment can be applied to any of the above-mentioned first to fifth embodiments.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be freely changed within the scope of the present invention. For example, the multi-core fibers 10 and 10A described in the above-described embodiment include a linear central core 11 and three spiral outer peripheral cores 12a to 12c, whereas the multi-core fiber has a plurality of cores. It suffices if at least one of the cores is formed in a spiral shape. Further, the multi-core fiber may have the central core 11 omitted.

When the FBG is formed on the central core 11 and the outer peripheral cores 12a to 12c of the multi-core fibers 10 and 10A, the FBG may be formed over the entire length of the multi-core fibers 10 and 10A in the longitudinal direction. It may be formed only in a part of the region. Further, the FBG formed on the central core 11 and the outer peripheral cores 12a to 12c of the multi-core fibers 10 and 10A may have a constant period or a continuously changing period (chirp grating). good.

1-4 ... Multi-core fiber with connector, 10,10A ... Multi-core fiber, 12 ... Outer core, 20,20A ... Connector, 21 ... Ferrule, 21a, 21b ... Key, 21c ... End face, 22 ... Housing, 22a ... Key, 23 ... Internal housing, 24 ... External housing, 24a ... Key, 25 ... Housing, C12 ... Outer core, FB1, FB2 ... Multi-core fiber, H1, H2 ... Accommodating part, SP1 ... Non-spiral part, SP2 ... Loose spiral part, X ... Fusion point

Claims (13)

A multi-core fiber in which at least one of a plurality of cores is formed in a spiral shape, and
The connector provided at the end of the multi-core fiber and
Equipped with
The end of the multi-core fiber is a non-spiral portion in which the core is linear, or a loose spiral in which the number of spirals per unit length of the core is smaller than that of a portion other than the end of the multi-core fiber. It is said to be a department,
Multi-core fiber with connector. The multi-core fiber includes a first multi-core fiber in which at least one first core of the plurality of first cores is formed in a spiral shape.
The second core, which has a plurality of second cores optically coupled to the plurality of first cores and is optically coupled to the spirally formed first core, is linearly formed. The number of spirals per unit length is less than that of the first core formed in a spiral shape, and the non-spiral portion or the loose spiral portion is a second multi-core fiber.
The multi-core fiber with a connector according to claim 1. The first multi-core fiber and the second multi-core fiber are fused to each other.
The multi-core fiber with a connector according to claim 2, wherein the connector is provided at the end of the multi-core fiber so as to internally accommodate a fusion point between the first multi-core fiber and the second multi-core fiber. .. The first multi-core fiber and the second multi-core fiber are fixed to the connector in a state where the plurality of optically coupled first cores and the plurality of second cores are in contact with each other. Item 2. The multi-core fiber with a connector according to Item 2. The multi-core fiber with a connector according to any one of claims 2 to 4, wherein the plurality of first cores and the plurality of second cores have different diameters. The multi-core fiber with a connector according to any one of claims 2 to 5, wherein the first multi-core fiber and the second multi-core fiber have different clad diameters. The connector according to any one of claims 2 to 6, wherein the inner diameter of the first accommodating portion accommodating the first multi-core fiber and the second accommodating portion accommodating the second multi-core fiber of the connector are different. With multi-core fiber. The multi-core fiber with a connector according to claim 7, wherein the inner diameters of the first accommodating portion and the second accommodating portion differ depending on the size of the diameter of the clad between the first multi-core fiber and the second multi-core fiber. Any one of claims 1 to 8, wherein the connector is provided at the end of the multi-core fiber so as to internally accommodate at least a part or all of the non-spiral portion or the loose spiral portion. Multi-core fiber with connector as described in the section. The multi-core fiber with a connector according to any one of claims 1 to 9, wherein the connector is a ferrule. The multi-core fiber with a connector according to claim 10, wherein the ferrule includes an alignment portion for alignment with respect to another multi-core fiber to be connected. The connector is a ferrule and
The housing that houses the ferrule and
The multi-core fiber with a connector according to any one of claims 1 to 9, wherein the multi-core fiber has a connector. 12. The multi-core fiber with a connector according to claim 12, wherein the ferrule or the housing includes an alignment portion for alignment with respect to another multi-core fiber to be connected.

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