JPS5938710A - Connecting method of optical fiber for retaining plane of polarization - Google Patents

Abstract

PURPOSE:To enable the easy connection of optical fibers in the finest state by mounting a pair of optical fibers for retaining planes of polarization to receptacles, making specific polarized light incident thereto from both ends and rotating and adjusting the fibers so that the light reflected most at the center. CONSTITUTION:Polarized light is entered an optical fiber 2 for retaining the plane of polarization on a feed side like an arrow 1. The polarized light is collimated by a collimating lens 6 to parallel luminous fluxes which pass the slope of a beam splitter 10 for polarized light, and are converted by a collimating lens 7. The converged light enters an optical fiber 3 on a receiving side similarly. The fibers are so adjusted in this stage that the light passing the fiber 3 is maximized. The polarized light 2 is detected with a photodetector 11a if said light is rotated 90 deg.. Then, the polarized light for monitoring shown by a broken line 12 is made incident from the fiber 3, and is detected with a photodetector 11b. In this state, the polarized light is made incident from the optical fibers 2, 3, and connectors 4a, 4b are rotated and adjusted. The connectors are fixed where the quantity of the light detected in the detectors 11a, 11b is largest, whereby the polarization axes of both optical fibers 2, 3 are adjusted to the optimum directions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting polarization-maintaining optical fibers used in optical communication channels, and particularly to a method for connecting polarization-maintaining optical fibers using a receptacle in which a polarizing beam splitter is installed in the center.

Since polarization-maintaining optical fibers have a pair of unique polarization axes that are orthogonal to each other, when they are connected, the polarization axes must be aligned to prevent deterioration of the extinction ratio. Generally, the following methods can be considered for connecting polarization maintaining optical fibers.

(1) A method of specifying the polarization axis direction on the connector itself to which the polarization-maintaining optical fiber is attached, and mechanically matching this direction using this as a guide.

(2) Operators are placed at six locations: the light input part of the polarization-maintaining optical fiber on the sending side, the light output part of the polarization-maintaining optical fiber on the receiving side, and the connecting part between the two. , and connect while adjusting so that the extinction ratio of the output light is the minimum and the optical output is the maximum.

(Phrase: Linearly polarized light is incident from both the sending and receiving sides,
Connect a pair of polarization-maintaining optical fibers while checking the state of the polarization plane only at the connector section.

Generally, it is required that the polarization axes of a pair of polarization-maintaining optical fibers in a connector section match within 0.5 degrees, but it is extremely difficult to achieve this mechanically in case (1). In the case of (2), six workers are required, and communicating with each other through communication means requires too much manpower and equipment, so it is not practical. Since no specific method has yet been proposed for method (3), the present invention was obtained as a result of studies regarding this method.

An object of the present invention is to eliminate the drawbacks of the prior art as described above and to provide a method for connecting polarization-maintaining optical fibers that can be performed by a single operator without using special equipment, and has the following characteristics: However, polarized light that vibrates in a direction parallel to the hypotenuse of the multilayer polarization beam splitter is input from the ends of a pair of polarization-maintaining optical fibers, and is directed to the ends of the other pair of collimating lenses. The purpose is to adjust the direction of the polarization axis of the polarization-maintaining optical fiber so that the maximum amount of light is detected by the light-receiving element, and to fix the connector to which the polarization-maintaining optical fiber is attached to a receptacle.

FIG. 1 is a sectional view of a connecting portion of a polarization maintaining optical fiber according to an embodiment of the present invention. A polarizing beam splitter 10 is installed in the center, and perpendicular Selfoc-type collimating lenses 6, 7, 8°9 are arranged on each side of the polarizing beam splitter 10. optical fiber 2
How many wavefront preserving optical fibers 6 are connected to the connector 4a?

A receptacle 5 is installed in which the receptacles 4b are screwed together, respectively. Further, the outer end surfaces of the collimating lenses 8 and 9 are installed to face the light receiving elements 11a and 11b, respectively.

Next, a method for adjusting the optical axis of the receptacle 5 configured as described above will be explained. Polarized light is made to enter through the wavefront preserving optical fiber 2 in the direction of the solid arrow line 1. This polarized light is linearly polarized light that vibrates parallel to the plane of the paper, but while passing through the collimating lens 6, it becomes a parallel beam, passes through the slope of the polarizing beam splitter 10, is focused by the collimating lens 7, and is received. How many wavefront preserving optical fibers 6 enter the wavefront preserving optical fiber 6? At this time, the receiver adjusts the direction of the polarization plane so that the light propagating through several wavefront preserving optical fibers 6 becomes maximum. That is, the receiver adjusts the screwing position of the sending connector 4b to which several wavefront preserving optical fibers 3 are fixed, and is fixed when the maximum amount of light is detected.

Next, if the polarized light emitted through the wavefront preserving optical fiber 2 is rotated by 90 degrees to make it a polarized light that oscillates perpendicular to the plane of the paper, then the polarized light reflected from the multilayered slope of the polarizing beam splitter 10 is , are focused by the collimating lens 8 and detected by the light receiving element 11a. At this time, the light receiving element 11
A adjusts its installation position etc. so that total reflected light can be detected.

In this state, how many wavefront preserving optical fibers are connected from the broken line 12 to the wavefront preserving optical fiber 6?
Inject linearly polarized light for monitoring purposes. The plane of polarization of this linearly polarized light oscillates perpendicular to the plane of the paper. In this case, the positions of the collimating lens 9 and the light receiving element 11b are adjusted so that the amount of coupling between them is maximized. The above is the basic adjustment of this optical connector, which uses polarized light perpendicular or horizontal to the plane of the paper.

However, since the transmitting side polarization preserving optical fiber 2 is fixed to the transmitting side connector 4a, and the number of receivers of the wavefront preserving optical fiber 6 is fixed to the receiver side connector 4b, it depends on the screwing state of those connectors 4. Each polarization maintaining optical fiber2.
The polarization axis direction of B becomes different. Therefore, while inputting light with a polarization direction perpendicular to the plane of the drawing into the double-sided wavefront preserving optical fiber 2゜6, the transmitting side connector 4a and the receiving side connector 4b were rotated, so that the amount of light received by the light receiving elements 11a and 11b was maximized. Tighten it as far as you can and secure it. In this way, the directions of the polarization axes of the polarization maintaining optical fibers 2 and 6 will be naturally adjusted to the optimum state. That is, polarization maintaining optical fiber 2
．． The direction of the polarization axis B is parallel and perpendicular to the plane of the paper, and one operator can connect the pair of polarization-maintaining optical fibers 2 and 6.

FIG. 2 is a cross-sectional view of the polarization maintaining optical fiber of FIG. 1. The periphery of the core 16 is surrounded by a cladding 14, the periphery of this cladding 14 is surrounded by an elliptical jacket 15, and the periphery is further surrounded by a support 16 so as to have a circular outer shape, so that the polarization maintaining optical fibers 2 and 6 are It is configured. In this case, the long axis (horizontal) direction of the elliptical jacket 15 is the slow axis, and the short axis (longitudinal) direction perpendicular thereto is the fast axis.

In the optical connector using the polarization-maintaining optical fiber of this example, collimating lenses are arranged perpendicular to each side of the central polarizing beam splitter, and a pair of polarizing lenses are arranged on the same axis. By attaching and connecting the wavefront preserving optical fiber to the connector, and forming a receptacle with the ends of the other pair of collimating lenses facing the photodetector, the beam is pasted together so that it is initially reflected by the polarizing beam splitter. By introducing polarized light parallel to the slope through a pair of polarization-maintaining optical fibers and making basic adjustments to maximize the sensitivity of the photodetector, a single operator can easily make the best connection. This effect can be obtained.

The method of connecting polarization-maintaining optical fibers of the present invention involves attaching a pair of polarization-maintaining optical fibers to the receptacle shown in Figure 1, inputting a specific polarized light from both ends, and maximizing the amount of light reflected by the central polarization beam splitter. By rotating and adjusting the polarization axis of the polarization-maintaining optical fiber so that the polarization-maintaining optical fiber is rotated, it is possible to obtain the effect that even one operator can easily connect the fiber in the best condition.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a receptacle that is a connection portion of a polarization-maintaining optical fiber according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the polarization-maintaining optical fiber of FIG. 1. 1.12: Polarized light incident direction, 2.6: Polarization maintaining optical fiber, 4: Connector, 5: Receptacle, 6 to 9: Collimating lens, 10: Polarizing beam splitter, 11: Photodetector, 16: Core , 14: cladding, 15: oval jacket, 16: support.

Claims (1)

[Claims] 1. Place cylindrical collimating lenses perpendicular to each side of the polarizing beam splitter installed at the center.
A pair of polarization-maintaining optical fibers are connected to the tips of the collimating lenses on the same axis by attaching them to cap nut-shaped connectors, and the ends of the other pair of collimating lenses face the light receiving element. In the method for connecting polarization-maintaining optical fibers using a receptacle, polarized light vibrating in a direction parallel to the hypotenuse on which the multilayer film of the polarization beam splitter is applied is incident from the ends of the pair of polarization-maintaining optical fibers. adjusting the polarization axis direction of the polarization-maintaining optical fiber so that the maximum amount of light is detected by the light-receiving element;
A method for connecting polarization-maintaining optical fibers, comprising fixing the connector to which the polarization-maintaining optical fiber is attached to the receptacle.