JPS59176714A - Connector for connecting optical fiber maintaining plane of polarization - Google Patents

Abstract

PURPOSE:To improve connection precision and to carry out connecting operation easily even outdoors by providing recessed or projection parts to the outer circumference of an inside circular sleeve adhered to an optical fiber which maintains the plane of polarization. CONSTITUTION:The coating material 2 of the polarization-plane maintaining optical fiber 1 whose outward appearance is circular is peeled near an end surface of the optical fiber 1. An adhesive 3 fixes the optical fiber 1 and circular inside sleeve 4 together without movement. A plug consists of the inside sleeve 4, an outside sleeve 7, and an external lid 10 with a female screw 9. This inside sleeve 4 has linear recessed grooves 5 at two places. Said optical fiber 1 is fixed to the inside sleeve 4 with the adhesive 3, and the grooves 5 are provided in the long-axis direction of the ellipse of the stressed layer 6 of the optical fiber 4. The external sleeve 7 whose outward appearance is circular has projection parts 8 on the internal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polarization maintaining optical fiber used in optical communications, optical sensors, and the like.

In recent years, in the field of optical communications, polarization-maintaining optical fibers, which transmit light while preserving the polarization plane, have been used in fiber gyros, optical sensors, etc., and are attracting attention as a promising optical transmission line. In such a polarization-maintaining optical fiber, the propagation constants of two propagating lights with polarization planes in two mutually orthogonal directions in the cross section of the core perpendicular to the optical axis are different.
The degeneracy of the fundamental mode of the propagating light causes the conservation of the polarization plane. In order to make the propagation constants of light in two orthogonal directions different within the cross section of the core, we can make the cross section of the core elliptical, or apply internal stress to the core so that the propagation constants are orthogonal within the cross section of the core. The refractive index in the two directions may be different.

This polarization-maintaining optical 7-eyeper has been used in fiber gyros and optical sensors, but recently, with the development of polarization-maintaining optical fiber with good polarization preservation and low loss, it has become possible to use long-distance optical fibers. Applications to heterodyne communications are now being considered. Long polarization-maintaining optical fibers used for such long-distance communications are designed to have the maximum anisotropic refractive index in two orthogonal directions within the cross section of the core perpendicular to the optical axis. This can be obtained by connecting so that the directions of refractive index or the direction of minimum refractive index coincide. The connection accuracy in this connection is expressed by the angular deviation in the principal axis direction, which is the direction of the maximum refractive index of the two polarization-maintaining optical fibers.The connection accuracy of polarization-maintaining optical fibers is to keep the angular deviation within 2 degrees. It is necessary to

Conventional 114 wavefront preserving optical fibers are connected mainly by fusion splicing.
The elliptical core on the end face of the eyeglass and the stress applying layer that applies anisotropic strain to the core are magnified with a lens, etc., and the long axis direction of the ellipse is carefully measured and fused so that the connecting directions match. (hereinafter referred to as the "expansion method"), a linearly polarized wave is input in the optical axis direction of the first polarization preserving light 7 eyer, and while the original fiber is rotated around the optical axis, the output light is also straight. Then, the output light of the first polarization-maintaining optical fiber is input into the optical axis direction of the second polarization-maintaining optical fiber, and the second polarization-maintaining optical fiber is adjusted to the optical axis direction. There is a method in which the output light of the second polarization-maintaining optical fiber is adjusted to be linearly polarized while rotating υ times υ, and then fused and connected from the front (hereinafter referred to as the "principal axis adjustment method"). Ta.

However, in the enlarging method, the end face of the optical fiber is enlarged with a lens, etc., and the long direction of the ellipse is determined, so the operation is simple, but the degree of connection is low, and as mentioned above, the two polarization planes are preserved. It has been difficult to reduce the misalignment of the main axis of the optical fiber to within 2 degrees. On the other hand, in the main axis adjustment method, the output light of the second polarization-maintaining optical fiber is adjusted so that it becomes linearly polarized light, so the connection accuracy was high, but the operation became complicated and the equipment became complicated. There were drawbacks. Especially when connecting outdoors, such as inside a manhole, the input end and output end of the Optical 7 Eyeper are far apart, so the output light is linearly polarized while rotating the input end of the optical fiber, as in the principal axis adjustment method. It was extremely difficult to make adjustments to achieve this.

An object of the present invention is to provide a polarization-maintaining optical fiber connector that eliminates these drawbacks, has high connection accuracy, and can be easily operated outdoors.

The configuration of the present invention is to provide a polarization-maintaining optical fiber having a refractive index fitting in the core in two directions orthogonal to each other at the center of the optical axis in a cross section perpendicular to the optical axis of the core. The present invention is characterized in that a concave portion or a convex portion extending in the optical axis direction is provided on the outer periphery of the inner circular sleeve to be bonded to the wavefront preserving optical fiber in one of the two directions.

Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a plane view showing a plug and a jack according to an embodiment of the present invention. 2 is the material III of the polarization maintaining optical fiber 1, which is peeled off near the end face of the fiber. 3 is the optical fiber 1 and the circular part 111.
1 and sleeve 4 so that they do not move relative to each other. As shown in the figure, it is composed of a plug tj, an inner sleeve 4, an outer sleeve 7, and an outer plug 10 with a female thread 9. As shown in the cross-sectional view at 8 in FIG. 2(a), this inner sleeve 4 is provided with linear grooves 5 at two locations, and the outer diameter of this sleeve is 5 mm. . As shown in FIG. 3, this inner sleeve 4 has a polarization maintaining optical fiber 1 fixed thereto by an adhesive 3, and the groove 5 of the inner sleeve 4 is located along the long axis of the ellipse of the stress applying layer 6 of the optical fiber 1. provided in the direction. As shown in FIG.
It's relevant.

On the other hand, as shown in FIG.
1 is fixed. As shown in the cross-sectional view of FIG. 4, two polarization-maintaining optical fibers are connected to these plugs and jacks. The protrusion 8 of the outer sleeve 7 of the plug fits into the groove 5 provided in the inner sleeve 4 of the plug and jack. The outer sleeve 7 connects the outer cover 10 of the plug provided with the female thread 9 to the screw 1 of the jack.
1, push the inner sleeve 4 on the plug side, which is integrated with the polarization preserving optical fiber 1, toward the inner sleeve 4 on the jack side, so that the end surfaces of the two polarization preserving optical fibers 1 are in close contact with each other. connected.

The central axes of the polarization-maintaining optical fiber, the inner sleeve 4, the outer sleeve 5, and the outer cover 10 coincide with each other when the end surfaces of the polarization-maintaining optical fiber 1 are in close contact with each other. In addition, since the fitting viscosity between the convex portion 8 of each sleeve and the groove 5 was approximately JOμm, the angular deviation in the long axis direction of the ellipse of the stress applying layer 6 of the two polarization maintaining optical fibers was reduced. It was about 0.4 degrees. Furthermore, when the extinction ratio of the output light from one polarization-maintaining optical fiber was 30 rlB, the extinction ratio before deterioration at the connection point was about 0.2 dB, and a highly accurate connection was achieved.

In this embodiment, the shape of the stress applying layer 6 of the polarization maintaining optical fiber is an ellipse, but it may be of any other shape such as a rectangle. Although the groove 5 of the inner sleeve 4 is provided, it may be provided in the short axis direction of the ellipse. Further, in this embodiment, the outer diameter of the polarization maintaining optical fiber was set to 125 μm, but it is clear that an outer diameter other than this may be used. Alternatively, the concave and convex portions of the sleeve may be reversed, and a convex portion and a corresponding reservoir portion may be provided on the inner sleeve and the outer sleeve, respectively.

According to the present invention, the connection accuracy is high, and the direction of the main axis at the connection end can be set between the concave and convex portions provided in the sleeve, so it is possible to connect the polarization plane outdoors, etc. It has the advantage that it can be easily connected to the output end even if they are far apart.

[Brief explanation of drawings]

Fig. 1 (al, (b)) is a sectional view of a plug and jack according to an embodiment of the present invention. Fig. 2 (al, (b))
Figure 1 (al) is a cross-sectional view of the inner and outer sleeves, Figure 3 (l-1, a cross-sectional view of the part where the inner sleeve and optical fiber in Figure 1 (a) are connected, and Figure 4 is a cross-sectional view of the inner and outer sleeves of the Figure (al
, (This is a cross-sectional view showing the state in which the BL connector is connected. In the figure, 1...Polarization maintaining optical fiber,
2...Coating material, 3...Adhesive material, 4...
...Inner sleeve, 5...Groove, 6...
... Stress application layer, 7... Outer sleeve, 8...
...Protrusion, 9...Plug screw, 10...
...Outside fly, 11...Jack body, 12
...It's a jack screw.

Claims (1)

[Claims] In a connector to be connected to a polarization-maintaining optical fiber whose core has different refractive indexes in two directions perpendicular to the center of the optical axis in a cross section perpendicular to the optical axis of the core, the polarization-maintaining optical fiber and A connector for polarization-maintaining optical fiber connection, characterized in that four or six sections extending in the optical axis direction are provided in one of the two directions on the outer periphery of the inner circular sleeve to be bonded.