JP2016148806A - Polarization maintaining optical fiber, capillary, and connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization maintaining optical fiber and a capillary that are capable of suppressing movement of rotation about an axis of an optical fiber.SOLUTION: A polarization maintaining optical fiber comprises: a core part 13 for propagating light; a cladding part 11 that is formed on an outer periphery of the core part 13 and has a refractive index lower than a refractive index of the core part 13; a pair of stress applying parts 12 that have stress applying action to the core part 13 and are formed at positions opposed to each other with the core part 13 as a center; and a positioning part that has a projection shape or a groove shape on an outer periphery of the cladding part 11 in a lengthwise direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a polarization maintaining optical fiber, a capillary, and a connector.

  In the related art, a polarization maintaining optical fiber in which a stress applying portion is provided in the fiber is used in optical communication. As shown in FIG. 1, the polarization maintaining optical fiber includes a cladding part 11, a stress applying part 12, and a core part 13. The polarization-maintaining optical fiber described above is a stress-applying polarization-maintaining optical fiber that utilizes a birefringence phenomenon caused by stress. By applying stress to the core portion 13, the phase difference between the modes constituting the fundamental mode is obtained. And a predetermined plane of polarization can be preserved.

  The stress applying portion 12 in the polarization maintaining optical fiber is preliminarily added with boron and has a higher thermal expansion coefficient than the clad portion 11. Since the stress applying portion 12 is contracted from the clad portion 11 in the cooling process when forming the optical fiber, a tensile stress is applied between the stress applying portions 12 arranged at both ends with respect to the core portion 13 in the upward direction of the connection. Birefringence can be generated.

  On the other hand, in the related technology, when the polarization maintaining optical fibers shown in FIG. 1 are connected to each other or when the light emitting element and the light receiving element are connected, the polarization maintaining optical fiber is fixed and stored. Is used. FIG. 2 shows a cylindrical capillary 15 according to a related technique in which a polarization maintaining optical fiber is inserted. The columnar capillary 15 can be formed while retaining the holes by drawing a base material in which holes are previously provided in the columnar capillary 15 by heat treatment.

  In the other related technique, a ceramic sleeve is used as a capillary. Capillaries made of ceramic generally have high hardness and are excellent in wear resistance, and are therefore widely used as optical connection components that ensure long-term reliability. The pores of the ceramic capillaries are formed by firing a molded body in which holes have been previously drilled, or by drilling after firing the molded body.

  Since the polarization maintaining optical fiber inserted into the cylindrical capillary 15 described above is a circular optical fiber, it rotates around the axis of the polarization maintaining optical fiber. The optical axis shift between the wave holding optical fiber and the optical component occurs, and the optical signal coupling loss due to the shift occurs.

“High-birefringence Polarizing Fiber with Flat Cladding” JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. LT3, NO. 4, AUGUST 1985.

  In order to solve the above problems, an object of the present invention is to provide a polarization-maintaining optical fiber and a capillary that suppress the rotational motion generated around the axis of the optical fiber.

  In order to achieve the above object, in the present invention, a projection shape or a groove shape is formed in the polarization maintaining optical fiber and the capillary.

Specifically, the polarization maintaining optical fiber according to the present invention is:
A core that propagates light;
A clad part formed on the outer periphery of the core part and having a refractive index lower than the refractive index of the core part;
A pair of stress applying portions having a stress applying action on the core portion and formed at positions facing each other with the core portion as a center;
A positioning portion having a protrusion shape or a groove shape along the longitudinal direction on the outer periphery of the cladding portion.

In the polarization maintaining optical fiber according to the present invention,
The positioning portion is
You may provide so that it may be located in the orthogonal | vertical direction with respect to the connection which connects the said stress provision parts, or on the extension line | wire of the said connection.

Specifically, the capillary according to the present invention is:
A capillary having a cylindrical outer shape,
A circular through hole extending in the major axis direction of the cylindrical shape is formed, and a groove shape is formed on the outer side of the through hole along the long axis direction, or a projection shape is formed on the inner side of the outer periphery. It has a plurality of hole portions.

Specifically, the connector according to the present invention is:
The polarization-maintaining optical fiber described above having a protrusion-shaped position determining portion is different from the above-described capillary having a groove-shaped hole portion in the protrusion-shaped position determining portion and the groove-shaped hole. The polarization-maintaining optical fiber described above having a groove-shaped positioning portion is inserted so as to fit into each other, or the above-described capillary having a protruding hole, The groove-shaped position extreme portion and the protrusion-shaped hole portion are inserted so as to fit into each other.

  The above inventions can be combined as much as possible.

  ADVANTAGE OF THE INVENTION According to this invention, the polarization maintaining optical fiber and capillary which suppress the rotational motion produced centering on the axis | shaft of an optical fiber can be provided.

An example of the polarization maintaining optical fiber which concerns on related technology is shown. An example of the capillary which concerns on related technology is shown. An example of PM fiber concerning Embodiment 1 is shown. An example of arrangement | positioning of the position extreme part of PM fiber which concerns on Embodiment 1 is shown. An example of the capillary which concerns on Embodiment 2 is shown. An example of the capillary which concerns on Embodiment 2 is shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. These embodiments are merely examples, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
A polarization maintaining optical fiber (hereinafter referred to as PM (Polarization Maintaining) fiber) according to the present embodiment is shown in FIG. The PM fiber has a clad part 11, a core part 13, and a pair of stress applying parts 12. The PM fiber has a pair of stress applying portions 12 with the core portion 13 sandwiched in the cladding portion 11 region.

  In the PM fiber according to the present embodiment, different residual stresses are generated in the first direction connecting the central points of the stress applying portions 12 of the pair of stress applying portions 12 and the second direction orthogonal to the first direction. . As a result, the PM fiber has birefringence and can propagate light while maintaining the polarization state of light.

The core portion 13 may be made of GeO ₂ glass added with GeO ₂ in order to increase the relative refractive index difference with respect to the cladding portion 11. The stress applying part 12 uses the glass to which B ₂ O ₃ is added, so that the stress applying part 12 having a larger linear expansion coefficient than the clad part 11 generates strain due to tensile stress, and thus the first direction described above. A stress is applied to the core portion 13 along the line to generate a birefringence.

  In the PM fiber, there exists a polarization mode having two orthogonal polarization planes generated by the tensile stress of the pair of stress applying portions 12, and the polarization maintaining optical fiber has a propagation constant difference between the two polarization modes. As a result, it is possible to suppress the coupling from one polarization mode to the other polarization mode and to enhance the polarization holding capability.

  As shown in FIG. 3, the PM fiber is provided with a convex position extreme portion that protrudes to the outer peripheral side of the clad portion 11. The positioning portion may be formed by forming a protrusion or groove having a desired shape into a base material and drawing it at the preform stage when producing the PM fiber.

  When the PM fiber is inserted into a capillary in which holes having the same shape as the cross-sectional shape of the PM fiber according to the present embodiment are provided in advance, and the PM fibers are connected to each other via the capillary, the position extreme portion provided in the PM fiber Thus, the rotational movement of the PM fiber can be suppressed, and the fiber end faces can be brought into contact with each other while maintaining the arrangement of the central axes of both PM fibers.

  In the PM fiber shown in FIG. 3, the long side x of the position extreme part is preferably a distance longer than the height y. By satisfying the relationship of x> y, the strength of the protrusion with respect to external stress can be increased, so that the occurrence of breakage or breakage of the position extreme portion can be reduced.

  As shown in FIG. 4, the position of the position extreme portion may be provided so as to be positioned in the upward direction with respect to the connection represented by the alternate long and short dash line connecting the pair of stress applying portions 12. In addition, the position of the position extreme part of the PM fiber may be a cross section of the PM fiber showing a shape other than the square shape of the position extreme part. Specifically, the shape of the protrusion when the position extreme portion protrudes outside on the outer periphery of the cladding portion 11 may be a semicircular shape or a triangular shape. Moreover, when the position extreme part has a groove | channel on the inner side on the outer periphery of the clad part 11, it may be triangular shape or semicircle shape.

  In addition, since the position of the positioning part according to the present embodiment can maintain the polarization direction by the positioning part, it is convenient to maintain the polarization direction if it is arranged vertically or extended from the connection described above. .

  When the connection represented by the alternate long and short dash line connecting the pair of stress applying portions 12 is used as a symmetry axis, the relationship of line symmetry is satisfied, or the vertical line of the connection in the vertical direction from the intersection of the center point of the core portion 13 and the connection And a line-symmetrical relationship may be satisfied. Further, the size of the position extreme portion is such that the length of the substantial arc obtained by excluding the projected arc on the clad portion 11 from the circumference of the clad side arc on the clad portion 11 is 50 mm. It may be a length satisfying a relationship of more than a percentage.

(Embodiment 2)
FIG. 5 shows a capillary according to this embodiment. The capillary is a capillary 16 with a guide having a grooved hole for inserting a PM fiber having a position extreme portion according to the first embodiment. A capillary 16 with a guide is formed by forming a circular hole in a glass base material at the stage of the preform of the capillary in order to insert a PM fiber having a projecting position positioning portion, and then using an ultrasonic drill. (Numerical Control) A capillary with a guide that can insert a PM fiber having a protruding shape by forming a guide groove for guiding a positioning portion in a hole and drawing it to a desired size is created be able to.

  In addition, when inserting a PM fiber having a groove-shaped positioning portion, the capillary 16 with a guide forms a circular hole in the glass base material at the stage of the capillary preform, and then the groove in the positioning portion. It is possible to insert a PM fiber having a groove shape by creating a convex member having a cross-sectional shape almost the same as the shape in advance and drawing the convex member to a desired size with the created convex member adhered to the hole portion. A guided capillary can be created.

  Note that the capillary according to the present embodiment may be a ceramic capillary formed of ceramic. In this case, the holes in the positioning part may be excavated after firing the molded body in advance, or the holes in the positioning part may be formed in the molded body in advance and fired before firing. Good.

(Embodiment 3)
In the present embodiment, as shown in FIGS. 5 and 6, a connector in which a PM fiber having a positioning portion is inserted into a capillary 16 with a guide and the PM fiber and the capillary 16 with a guide are combined will be described below.

  By inserting a PM fiber having a position extreme part into the capillary 16 with guide according to the present embodiment, the PM fiber is fitted into the position guide part in the PM fiber and the guide groove or protrusion in the capillary 16 with guide. The fiber end faces can be abutted with each other while maintaining the arrangement of the central axes of both PM fibers.

  In addition, since the optical axis misalignment that occurs when connecting the PM fiber and the optical connecting component can be prevented, the optical signal coupling loss due to the optical axis misalignment is reduced by using the connector according to this embodiment. can do.

  FIG. 6 shows a D-surface capillary 17 in which a D-cut surface is formed on the cylindrical capillary 16 with a guide according to the present embodiment. The D-surface capillary 17 can form a capillary having a D-cut surface by forming a D-cut in a glass base material at the stage of capillary preform and then drawing to a desired size. Since part of the D-surface capillary 17 has a flat surface, the position and orientation are determined when the D-surface capillary 17 is fixed to an external device, so that assembly work can be easily performed.

  The D-surface capillary 17 described above may be a ceramic capillary formed of ceramic. In this case, the flat surface of the D-surface shape may be ground after the cylindrical shaped body is fired in advance, or may be fired by previously forming the flat surface on the shaped body before firing. .

  The PM fiber and the capillary with guide according to the present invention are shown as an example of a configuration applied to the information and communication industry, but the medical field used as a medical device used as an optical output probe for applying an optical stimulus to a target. Can be applied to.

11: Cladding portion 12: Stress applying portion 13: Core portion 15: Cylindrical capillary 16: Grooved capillary 17: D face capillary

Claims (4)

A core that propagates light;
A clad part formed on the outer periphery of the core part and having a refractive index lower than the refractive index of the core part;
A pair of stress applying portions having a stress applying action on the core portion and formed at positions facing each other with the core portion as a center;
A positioning portion having a protrusion shape or a groove shape along the longitudinal direction on the outer periphery of the cladding portion,
A polarization-maintaining optical fiber comprising: The positioning portion is
The polarization maintaining optical fiber according to claim 1, wherein the polarization maintaining optical fiber is provided so as to be positioned in a direction perpendicular to a connection connecting the stress applying portions or on an extension line of the connection. A capillary having a cylindrical outer shape,
A circular through hole extending in the major axis direction of the cylindrical shape is formed, and a groove shape is formed on the outer side of the through hole along the long axis direction, or a projection shape is formed on the inner side of the outer periphery. Having a plurality of holes,
A capillary characterized by comprising: The polarization-maintaining optical fiber according to claim 1 or 2, wherein the polarization maintaining optical fiber having a protrusion-shaped position determining portion is provided with a groove-shaped hole portion. The polarization-maintaining optical fiber according to claim 1, wherein the polarization maintaining optical fiber has a protrusion shape, or the groove-shaped hole portion is inserted so as to fit into each other, or has a groove-shaped positioning portion. The connector according to claim 3, wherein the capillary has a hole, and the groove-shaped positioning portion and the protrusion-shaped hole are inserted into each other.

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