JPS5938709A - Connecting method of optical fiber for retaining plane of polarization - Google Patents

Abstract

PURPOSE:To enable the connection to align the intrinsic polarization axes of optical fibers with high accuracy by providing a pair of polarization plates having orthogonally intersecting planes of polarization across the place where the ends of the optical fibers face to each other and regulating the rotation of the optical fibers while making macro-observation. CONSTITUTION:A pair of optical fibers 1a, 1b for retaining the plane of polarization are butted to each other in the cut ends having a plane shape. A pair of polarization plates 3a, 3b having orthogonally intersecting planes of polarization are provided above and below the butt parts thereof. The fibers 1a, 1b have the distortion of the slow axis in the long axis direction of the elliptical jacket and the distortion of the fast axis in the short axis direction and therefore said parts are observed in bright coloring. Since the elliptical jacket 12 and support 13 differ in refractive index, the light reflects irregularly on the outside of the jacket 12. The operator observes the jacket 12 which appears bold or thin with a microscope 5 and aligns both by rotating adapters 9 thereby matching the intrinsic polarization axes of a pair of the fibers 1a, 1b and connecting the same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a splicing method for matching the intrinsic polarization axes of polarization-maintaining optical fibers, and more particularly to a splicing method that is performed while observing the spliced point using a microscope.

Since it is not possible to find the unique polarization axis of a polarization-maintaining optical fiber even if you enlarge its appearance, it is currently possible to find the polarization axis in a predetermined direction from one free end face of a polarization-maintaining optical fiber whose end faces are closely opposed. The connection or butt splicing is performed while the amount of light emitted from the free end face of the other polarization-maintaining optical fiber is monitored. This type of connection method consumes a great deal of time and effort in long optical transmission lines, requiring the safety of cooperating workers at remote locations. However, if the coincidence of the eigenpolarization axes exceeds the allowable range of 0.5 degrees, disadvantages such as deterioration of the extinction ratio will occur.

The present invention aims to eliminate the drawbacks of the above-mentioned prior art and provide a method for splicing polarization-maintaining optical fibers that can be spliced with high precision even by a single operator. A pair of polarizing plates with polarization planes perpendicular to each other are placed between opposite ends of the wavefront preserving optical fiber, and a white light source is placed on the outside of one of them, and a microscope is placed on the outside of the other. The opposite end portions of polarization-maintaining optical fibers are observed, and their inherent polarization axes are matched to connect them.

FIG. 1 is an explanatory diagram of a method for connecting polarization-maintaining optical fibers, which is an embodiment of the present invention. The tips of the polarization maintaining optical fibers 1a and '1b accommodated in the adapters 9a and 9b are closely opposed to each other, and the adapters 9a and 9b are attached to the respective holders 2a.
, 2b.

Further, polarizing plates 3a and 3b are installed above and below the opposing parts of the tips of the polarization maintaining optical fibers 1a and 1b, a microscope 5 is placed above the polarizing plate 6a, and a white light source 4 is placed below the polarizing plate 6b.
is installed. Note that since the polarizing plates 3a and 3b are in an orthogonal state, the area other than the polarization maintaining optical fibers 1a and 1b is a dark field.

FIG. 2 is a perspective view of the adapter shown in FIG. 1 when it is unfolded. A V-groove 7 is formed in the center of the adapter 9 connected by a hinge 8, and the polarization-maintaining optical fiber 1 is installed in the V-groove 7. This adapter 9 can be rotated in the holder 2 as shown in FIG.

FIG. 6 is an enlarged sectional view of the polarization maintaining optical fiber of FIG. 11, in which a central core 11 is surrounded by an annular cladding 11 concentrically. The cladding 11 is surrounded by an elliptical jacket 12 and further surrounded by a support 16 to form a circular polarization maintaining optical fiber 1.

A connection method using the connection means arranged as shown in FIG. 1 will now be described. A pair of polarization-maintaining optical fibers 1 have planarly cut end faces abutted against each other with a slight gap. Since the light from the white light source 4 is selected by the polarizing plate 6b as only the light component vibrating in a specific direction, it is absorbed by the polarizing plate 6a installed perpendicularly thereto and is not observed by the inner eye.

However, since the polarization maintaining optical fibers Ia and lb have distortion in the long axis direction of the elliptical jacket with the slow axis and in the short axis direction with the fast axis, this portion is observed as being brightly colored. Further, since the elliptical jacket 12 and the support 16 have different refractive indexes, light is diffusely reflected on the outer surface of the elliptical jacket 12, and when magnified with the microscope 5, its thickness can be seen. Therefore, when the adapter 9 is rotated, the elliptical jocket 12 of the polarization maintaining optical fiber 1 appears thicker or thinner.

The rotation is stopped at the thickest position or the thinnest position, and the two end faces are brought together, and the fusion electrode 6a,
By discharging 6b, it becomes possible to connect the pair of polarization-maintaining optical fibers 1a and 1b with their unique polarization axes aligned.

Note that although the ends are fusion-spliced by electric discharge in the above example, it is also possible to connect the polarization-maintaining optical fiber 1 by mechanically fixing it to the V-groove 7 as another method.

The connection method of this embodiment is to rotate the end face of a polarization-maintaining optical fiber between a pair of orthogonal polarizing plates, and then weld the optical fiber at the point where the elliptical jacket appears to have the maximum or minimum thickness, or to By fixing it inside the
This provides the advantage that even one worker can make a suitable connection.

The two-legged embodiment uses a pair of polarizing plates to match the unique polarization axes of the polarization-maintaining optical fibers, but the holders 2a, 2b in FIG. and insert the polarization preserving optical fiber into this matching oil.

Since this matching oil has the same refractive index as the support 16, the shape of the elliptical jacket 12 can be clearly observed.

By doing this, the position where the elliptical jacket 12 is thickest and the position where it is thinnest become clearer, making it possible to match the unique polarization axes of the pair of polarization-maintaining optical fibers 1 and perform a more precise connection. You get the advantage of being

The method for connecting polarization-maintaining optical fibers of the present invention uses a pair of polarizing plates, or by immersing the end of the polarization-maintaining optical fiber in matching oil having the same refractive index as the support, the shape of the elliptical jacket is adjusted. This has the effect of making it possible to conduct a magnified observation, aligning the characteristic polarization axes, and making a good connection with a small extinction ratio.

[Brief explanation of the drawing]

Figure 1 shows a polarization-maintaining optical fiber, which is an embodiment of the present invention.
2 is an exploded view of the adapter shown in FIG. 1, and FIG. 6 is an enlarged sectional view of the polarization-maintaining optical fiber shown in FIG. 1. 1: polarization maintaining optical fiber, 2: holder, 6: polarizing plate, 4: white light source, 5: microscope, 6: fusion electrode, 7: v
groove, 8: hinge, 9: adapter, 10: core, 11: cladding, 12: oval jacket, 16: support. 1 day bacterium 21 3 days 1” I+ 12

Claims (1)

[Claims] 1. In a method for connecting polarization-maintaining optical fibers having adjustment means that allows the end faces of a pair of polarization-maintaining optical fibers to face each other to enable three-dimensional fine movement and rotation on the spot, A pair of polarizing plates with their polarization planes perpendicular to each other are placed between opposite ends of the plates, a white light source is placed outside one of them, and a microscope is placed outside the other. A method for connecting polarization-maintaining optical fibers, which comprises observing opposing ends of the fibers and aligning their intrinsic polarization axes for connection.