JPS60254011A - Polarization plane maintaining optical fiber cable - Google Patents

Abstract

PURPOSE:To easily connect plural polarization plane maintaining optical fibers at a time while suppressing deviation in main axis angle within a specific value range by arranging the optical fibers so that anisotropic strain applied onto the outer periphery of a circular center member is directed to the center of a center member. CONSTITUTION:A projection part 17 is provided on the outer periphery of a connector 16 which holds an optical fiber 15 in the direction of the long axis of the ellipse of the strain-impressed layer of a polarization plane maintaining optical fiber 15. Recessed part 21 are formed at the outer periphery of the center member 19 which has a circular tension member 20. The whole body is covered with the covering 22 of a cable and projection parts 17 of connectors 16 are fixed while fitted in recessed parts 21 of the center member 19. Then, long axes (main axis) of ellipses of strain-impressed layers of all polarization plane maintaining optical fibers constituting the cable run in the center of the center member 19, and the cores are at equal distance from the center of the center member 19.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a polarization-maintaining optical fiber cable, and more particularly to a polarization-maintaining optical fiber cable used in optical communications, optical sensors, and the like.

(Prior art) In recent years, in the field of optical communications, polarization-maintaining optical fibers, which transmit signals while preserving the polarization plane, have been used in fiber gyros, optical sensors, etc., and are attracting attention as a highly promising source transmission line. ing.

In such a polarization-maintaining optical fiber, the degeneracy of the fundamental mode of the propagating light is resolved because the propagation constants of the two propagating lights with polarization planes in two mutually orthogonal directions in the cross section of the core perpendicular to the original axis are different. , conservation of the polarization plane occurs.

In order to make the propagation constants of light different in two orthogonal directions within the cross section of the core, the cross section of the core is made elliptical, or internal stress is applied to the core to make the propagation constants of light different in the two orthogonal directions within the cross section of the core. What is necessary is to make the refractive indexes of the two different from each other.

Initially, polarization-maintaining optical fibers were primarily used for fiber gyros, optical sensors, etc., as mentioned above.
Recently, with the development of polarization-maintaining optical fibers that have good polarization-maintaining properties and low loss, applications to long-distance optical heterodyne communications are being considered. A long polarization-maintaining optical fiber used for such long-distance communication has an anisotropic refractive index in the two orthogonal directions in the cross section of the core perpendicular to the original axis, and the direction of the maximum refractive index or the minimum This can be obtained by connecting opposing polarization maintaining optical fibers so that their refractive index directions match. The splicing accuracy is expressed by the angular deviation in the direction of the principal axes, which is the direction of the maximum refractive index mentioned above, of the two polarization-maintaining optical fibers, but the splicing accuracy of the polarization-maintaining optical fibers is to keep the above-mentioned angular deviation within 2 degrees. It is said that it is necessary to

In order to expand the scope of application of such polarization-maintaining optical fibers to original heterodyne communications, various multicore optical fiber cables using polarization-maintaining optical fibers have recently been actively developed.

In connecting such multicore optical fiber cables, it is necessary to ensure that the above-mentioned angular deviation of the principal axes is within 2 degrees for all of the polarization-maintaining optical fibers that constitute the optical fiber cable.

Conventionally, multicore optical fiber cables using normal original fibers that are not polarization-maintaining have been developed in various configurations.
FIG. 4 is a diagram showing the configuration of a conventional i7 cable that does not maintain polarization. In Figure 4, normal source fibers 1~
6 is an intervening string 8 that has the same outer diameter as the tension member 7 arranged in the rotation of the tension member 7 serving as the central member.
13 and the outer sheath 14.

In this type of original fiber cable, if the diameter of the tension member and the intervening string is set to meet the outer diameter of the fiber, the position of the original fiber placed between the intervening string and the jacket can be completely determined. This makes it easy to connect multi-core optical cables all at once. According to recent technological advances in the dimensional accuracy of the six fibers themselves and the nine cables, it has become possible to connect cables with sufficient practical performance when connecting the original cables together as described above. There is. However, when connecting multi-core optical fiber cables composed of polarization-maintaining optical fibers, it is not only necessary to connect the cores with each other with high precision, but also to match the principal axes of the stress application layers as described above. In such a configuration, it is difficult to simultaneously satisfy two conditions (high-precision connection between cores and alignment of the main axis directions) by batch connection.

However, even with a multi-core optical fiber cable made up of polarization-maintaining optical fibers with the configuration shown in Figure 4, if the component polarization-maintaining optical fibers are connected one by one, the result will be the same as when they are connected all at once. Although it is possible to connect with high accuracy, it has the drawback that the operation becomes extremely complicated.

(Object of the Invention) An object of the present invention is to provide a polarization-maintaining optical fiber cable that eliminates the above-mentioned drawbacks, keeps the angular deviation of the main axis within a specified value, and allows easy batch connection.

(Structure of the Invention) The polarization-maintaining optical fiber cable of the present invention includes a glass layer that is anisotropically strained to a core glass layer and has the same center as the core. A plurality of polarization-maintaining optical fibers having a circular outer shape are arranged on the outer periphery of a circular central member such that the direction of anisotropic strain applied to the polarization-maintaining optical fibers points toward the center of the central member. Composed of Yota.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of a polarization-maintaining optical fiber held concentrically with a connector used in an embodiment of the present invention, and FIG. The figure is a schematic cross-sectional view of a central member used in an embodiment of the present invention.

In FIG. 2, 15 is a polarization-maintaining optical fiber having an elliptical stress applying layer, and 16 is the polarization-maintaining optical fiber 1.
5, the center of the connector and the center of the polarization maintaining optical fiber are aligned. Also, connector 1
A convex portion 17 is provided on the outer periphery of 6. The convex portion 17 is provided in the long axis direction of the ellipse of the stress applying layer of the polarization maintaining optical fiber 15. Further, 18 is a polarization maintaining optical fiber 15
This is a filling material that holds the connector 16 concentrically with the connector 16.

In FIG. 3, 19 is a central member having a circular outer shape;
0 is a circular tension member concentric with the central member. 2
1 is a recess provided on the outer periphery of the central member 19;
1 were provided at positions dividing the outer periphery of the central member 19 into six equal parts. In addition, the convex portion 17 provided on the outer periphery of the connector 15 has a structure that can be fitted into the recess 21 provided on the outer periphery of the central member 19. The structure shown in FIG. 1 is composed of six polarization-maintaining optical fibers. This is an example of a cross-sectional view of a polarization-maintaining optical fiber cable, in which 22 is the outer sheath of the cable. By covering the entire connector with the outer jacket, the connector 16 including the polarization preservation source fiber 15 is fixed with its convex portion 17 fitted into the concave portion 21 provided on the outer periphery of the central member 19. As mentioned above, the convex portion 17 is
Since the stress application layer of the polarization maintaining optical fiber 15 is provided in the long axis direction of the ellipse, all the polarization maintaining optical fibers constituting the p1 cable can be The long axis (the aforementioned main axis) of the ellipse of the stress-applying layer of the fiber passes through the center of the central member 19 . Furthermore, since the aforementioned recesses 21 are arranged so as to divide the outer periphery of the central member 19 into six equal parts, the main axes of the six polarization-maintaining optical fibers all pass through the center of the central member 19, and Divide the circumference into six equal parts. Therefore, the angle between the principal axes of adjacent polarization-maintaining optical fibers with respect to the center of the central member is 360°/6=60°. Furthermore, the polarization-maintaining optical fiber 15 and the connector 16 are constructed concentrically, and the outer diameters, fiber outer diameters, and core diameters of the six pairs of connectors shown in FIG. 1 are all equal. So, the third
In the illustrated cable, the cores of all polarization maintaining optical fibers making up the cable are equidistant from the center of central member 19. As is clear from the above explanation, when considering the batch connection of polarization-maintaining optical fiber cables as in this example, there are two conditions: high precision connection of the cores of opposing polarization-maintaining optical fibers, and matching of the principal axes. It can be seen that these can be simultaneously and easily realized.

In this embodiment, the number of polarization maintaining optical fibers constituting the polarization maintaining optical fiber cable is six, but any other number may be used. Further, although the configuration is such that the long axis of the ellipse of the stress applying layer of the polarization maintaining optical fiber points toward the center of the central member, it may be configured such that the short axis of the ellipse points toward the center of the central member. Furthermore, the materials of the filler, connector, central member, tension member, outer cover, etc. are not particularly limited. Further, in this embodiment, the connector is provided with a convex portion and the central member is provided with a concave portion, but the connector may be provided with a concave portion and the central member may be provided with a convex portion. Furthermore, there is no particular limitation on the method for collectively connecting polarization-maintaining optical fiber cables.

(Effects of the Invention) As described above, according to the present invention, polarization-maintaining optical fiber cables can be easily connected together and high connection accuracy can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an embodiment of the present invention, FIGS. 2 and 3 are schematic cross-sectional views of parts of an embodiment of the present invention, and FIG. 4 is a conventional non-polarization preserving 17-eye beam. FIG. 3 is a schematic cross-sectional view of a cable. 1.2, 3, 4, 5, 6.15...Polarization maintaining optical fiber, 7,20...Tension member, 8,9.10
, 11゜12.13... Intervening string, 14, 22... Outer covering, 16. Connector, 17. Convex portion, 18.. Filler, 1
9... Central member, 21... Recessed portion. Agent Patent Attorney Susumu Uchihara 67B", =='=>.\-2- Figure 1 Figure 42 Figure 45 Figure M4

Claims (1)

[Claims] A circular center member includes a plurality of polarization-maintaining optical fibers each having an anisotropic strain applied to a glass layer serving as a core and a glass layer having the same center as the core, and having a circular outer shape having the same center as the glass layer serving as the core. A polarization-maintaining optical fiber cable, characterized in that the polarization-maintaining optical fiber cable is arranged on the outer periphery of the polarization-maintaining optical fiber so that the direction of anisotropic strain applied to the polarization-maintaining optical fiber faces the center of the central member.