JPH0894879A - Optical connector for polarization maintaining fiber - Google Patents

Abstract

PURPOSE: To make a small-sized optical connector, such as MU type optical connector, adaptable to a polarization maintaining fiber by positioning the optical connector with good accuracy for an angle around the axis of ferrules while assuring the resistance to the sustained characteristics against external force. CONSTITUTION: A part or the whole of the surfaces constituting the outer peripheries of the flanges 21 of the ferrules 2 constitute tapered surfaces in a direction where the sectional area perpendicular to the axis decreases from the rear end toward the front end of the ferrules 2. The inner peripheral surface of the part of a plug housing 11 where the ferrules 2 are held constitutes the tapered surface similar to the outer peripheries of the flanges of the ferrules 2. A pair of the ferrules 2 are respectively pushed by a slight amt. into the plug housing 1 when a pair of the plugs 1 to be connected are coupled to the adapter. The tapered surfaces on the outer peripheries of the ferrules are then parted from the tapered surfaces on the inside surface of the plug housing and the ferrules 2 are floated from the plug housing 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical connector for connecting an optical fiber, and is applied to a polarization maintaining optical fiber or the like when the angle around the axis of the optical fiber to be connected must be accurately adjusted. It is suitable.

[0002]

2. Description of the Related Art As an optical connector used for connecting optical fibers to each other, there is, for example, an F04 type single-core optical fiber connector defined in JIS C 5973, which is generally called an SC type optical connector. It is widely used for The SC type optical connector includes a ferrule fixed to the end of the optical fiber to be connected, a pair of plug housings that hold the ferrule inside with a spring that presses the ferrule in the axial direction, and an elastic sleeve that aligns both ferrules. And a connection adapter that holds the plug housing and is connected to the plug housing. Since the ferrule is inside the plug housing and the elastic sleeve is inside the connection adapter, even if external force acts on the plug housing and the optical fiber cord in the connected state, no force acts on the ferrule and the elastic sleeve. Realizes extremely stable connection characteristics.

On the other hand, among optical fibers, there is a polarization-maintaining optical fiber that propagates while maintaining the polarization state of light constant, and it is particularly high speed among sensors utilizing optical interference and optical transmission equipment. It is used for modulators that process various optical signals.

This polarization-maintaining optical fiber has a birefringence in the core portion for propagating light, and maintains the polarization state only when linearly polarized light is incident in accordance with the direction of its birefringence axis. Propagate the signal. Therefore, when connecting the polarization maintaining optical fibers together, not only the axes must be precisely aligned, but also the directions of the birefringent axes of both must be accurately aligned.

Here, the above-mentioned SC is added to the polarization maintaining optical fiber.
When applying the optical connector, a troublesome problem occurs. That is, since the float amount in the plug housing of the ferrule and the positioning accuracy of the angles around the axes of both optical fibers are contradictory conditions, it is difficult to realize a structure that satisfies both. Therefore, for example, as described in JP-A-1-216304, by narrowing one key groove of the flange of the ferrule, the angle around the axes of the ferrules can be made substantially unique while securing the required float amount. An SC type optical connector applicable to a polarization maintaining optical fiber has been realized by adopting a fixed structure. Further, when more strict positioning is required, a structure has been proposed in which the ferrule is held in the plug housing via an intermediate member, as described in JP-A-1-234807.

On the other hand, among the optical connectors, there is an optical connector smaller than the SC type optical connector, which is called "ComPact and self-retentive multi-ferrule opti" by S. Iwano et al.
calbackpanel connector "(IEEE Journal of Lightwave
Technology, vol.10, no.10, pp.1356-1362, Oct.1992) has been put to practical use.
The structure is shown in FIG. The ferrule 2 used for the MU type optical connector has a diameter of 1.25 mm, which is half the diameter of the SC type optical connector, which is 2.5 mm, and the flange portion 22 does not have a key groove unlike the SC type optical connector, and each corner of the quadrangle. Has a chamfered shape, and has a structure in which rotation of the ferrule 2 is restricted by being held inside a plug housing 12 having a similar cross-sectional shape.

The MU type optical connector enables high-density plug-in connection via the back panel in the bookshelf type mounting method and can be used for single-core optical connection like the SC type optical connector, and is small in size. Therefore, it is also suitable for optical wiring inside the device, for example, on a printed circuit board.

The polarization-maintaining optical fiber is mainly used inside the device, for example, for connecting the LD light source to an external modulator or an optical switch. Therefore, as a connector for a polarization maintaining optical fiber, a connector that is smaller than the SC optical connector and is capable of plug-in connection is required. If the above-mentioned MU type optical connector can be applied to the polarization maintaining optical fiber, Its use is wide.

[0009]

When the MU type optical connector is applied to the polarization maintaining optical fiber, it is necessary to satisfy the contradictory conditions of the ferrule float amount and the angular position about the axis. Much more difficult than connectors. Because, as shown in FIG.
Flange 2 of ferrule 2 used for U type optical connector
2 is thinner than the SC type optical connector, and may be greatly inclined even with a slight gap with the plug housing 12. For example, when the float amount of the ferrule 2 with respect to the plug housing 12 is 0.1 mm in each direction, the maximum tilt angle is cos from the reference position shown in FIG. 7A to the maximum tilt angle shown in FIG. ^-1 (2.6 / 3.1) -cos ^-1 (2.8 / 3.
1) = 7.6 °, and the worst inclination between the two ferrules to be connected is 15.2 °. The polarization crosstalk in this case is 10 log (tan ² (15.2 °)) =-11.3
(DB), which is completely useless as an optical connector for polarization maintaining fiber. Even if the float amount is 0.05 mm in each direction, the maximum tilt angle is 3.6 ° from the reference position, and the worst polarization crosstalk is -18.1 dB. It is difficult to further reduce the float amount in terms of dimensional tolerance, and the original role of the double fitting structure cannot be fulfilled.

The present invention has been made in view of the above circumstances, and for a small-sized optical connector such as an MU type optical connector, the ferrule floats from the housing when the optical connector is connected, and the connection characteristic resistance against external force is secured. However, it is an object of the present invention to accurately position the ferrule with respect to the angle around the axis and enable application to a polarization maintaining optical fiber.

[0011]

An optical connector for a polarization maintaining fiber according to the present invention for achieving the above object has a flange portion having a polygonal cross section perpendicular to the axis, and has two optical components to be coupled. It is composed of a pair of ferrules that fix the ends of the fibers, a plug housing that holds the ferrule slidably in the axial direction, and a spring that is built in the plug housing and biases the ferrule in the axial direction. A pair of plugs, an elastic sleeve that fits and abuts the pair of ferrules so that the ends of the optical fibers are aligned and connected to each other in the axial direction, and the elastic sleeve is held inside by floating. And a pair of plug housings to be connected together, each ferrule being fitted in the elastic sleeve. In the optical connector coupled to the connection adapter, a part or all of the surface forming the outer periphery of the flange portion of the ferrule is oriented in a direction in which the cross-sectional area perpendicular to the axis decreases from the rear end of the ferrule to the tip. The ferrule has a tapered surface, an inner peripheral surface of a portion of the plug housing that holds the ferrule has a tapered shape similar to the outer peripheral portion of the flange of the ferrule, and the ferrule when the plug is not connected. The outer peripheral surface of the flange portion is pressed against the inner peripheral surface of the plug housing by the spring to be fixed, and when a pair of plugs to be connected are coupled to the adapter, the pair of ferrules are slightly inside the plug housing. The tapered surface of the outer circumference of the ferrule is pushed away from the tapered surface of the inner surface of the plug housing, Lumpur is characterized by a structure that the float from the plug housing.

[0012]

[Function] Since the tapered surface of the ferrule flange is pressed against the tapered surface of the inner surface of the plug housing by the spring when the optical connector is not connected, the angle around the axis of the ferrule is accurately maintained at the set value. . When the optical connectors are connected, both ferrules abut inside the connection adapter and are pushed into the plug housing, so that the flange of the ferrule separates from the tapered surface of the inner surface of the plug housing and floats. At this point, the ferrule has already been inserted into the elastic sleeve in the connection adapter, so that the ferrule does not rotate and both plugs are coupled in the initial position. With this structure, it is possible to achieve both accurate positioning with respect to the angle around the axis of the ferrule, a double fitting structure due to the ferrule floating, and two conflicting conditions.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical connector for polarization maintaining fiber will be described below with reference to the accompanying drawings. 1A and 1B show the structure of an optical connector for a polarization maintaining fiber according to the present invention. FIG. 1A is a front view thereof, FIG. 1B is a partial side sectional view thereof, and FIG. 2 shows a structure of a ferrule. The figure (a) is the front view, the figure (b) is a side view, FIG. 3 shows the positional relationship between the ferrule and the plug housing, and the figure (a) is a state diagram in which the plug is not connected. The same figure (b) is a state diagram in which a plug is connected.

As shown, the flange 2 of the ferrule 2
The outer periphery of 1 has a shape with chamfered polygonal corners,
It forms a taper surface on the front downside, and plug housing 11
It is held along the inner tapered surface. The details are
As shown in FIG. 3, when the plug 1 is not connected, the flange 21 of the ferrule 2 is biased by the spring 3 and contacts the plug housing 11 (see FIG. 3A).
However, when the plug 1 is connected, the ferrule 2 is pushed into the plug housing 11, and the flange 21 separates from the plug housing 11 and floats (see FIG. 3B).

At this point, the ferrule 2 has already been inserted into the elastic sleeve in the connection adapter, so the ferrule 2 does not rotate, and the two plugs 1 are joined together in the initial position. With this structure, it is possible to achieve both accurate positioning with respect to the shaft rotation angle of the ferrule 2, a double fitting structure due to the ferrule 2 floating, and two contradictory conditions.

The connection adapter used is a normal MU.
The connection adapter used for the optical connector can be used without any special structure.

[0017]

As described above, in the polarization-maintaining fiber optical connector according to the present invention, the outer periphery of the flange of the ferrule has a tapered surface. Therefore, the ferrule floats with high accuracy with respect to the angle around the axis of the ferrule. Therefore, it is possible to achieve both the double fitting structure and the two contradictory conditions. Therefore, even a small-sized optical connector such as a MU type optical connector can be used for connection of a polarization maintaining optical fiber that requires high accuracy with respect to the angle around the axis of a ferrule, and a small optical connector is required. It is possible to provide an extremely advantageous optical connector for polarization maintaining fiber when using the polarization maintaining optical fiber for optical wiring inside the device.

[Brief description of drawings]

1A and 1B show a structure of an optical connector for a polarization maintaining fiber according to an embodiment of the present invention, FIG. 1A is a front view thereof, and FIG. 1B is a partial side sectional view thereof.

FIG. 2 is a diagram for explaining the structure of the ferrule,
The figure (a) is the front view, and the figure (b) is the side view.

3A and 3B are views for explaining the positional relationship between the ferrule and the plug housing, FIG. 3A is a state diagram in which the plug is not connected, and FIG. 3B is a state diagram in which the plug is connected.

4A and 4B are views showing a structure of a conventional MU type optical connector, in which FIG. 4A is a front view thereof and FIG. 4B is a partial side sectional view thereof.

5A and 5B are views for explaining the positioning accuracy with respect to the angle around the axis of the ferrule, FIG. 5A is a view showing a reference position, and FIG. 5B is a view showing a rotated state.

[Explanation of symbols]

 1 Plug 11,12 Plug housing 2 Ferrule 21,22 Flange

Claims (1)

[Claims] 1. A pair of ferrules each having an end portion of two optical fibers to be coupled, each having a flange portion having a polygonal cross section perpendicular to the axis, and the ferrule slidably in the axial direction. A pair of plugs each of which holds a plug housing and a spring which is built in the plug housing and biases the ferrule in the axial direction, and the ends of the optical fibers are aligned and connected to each other in the axial direction. A pair of ferrules are fitted to each other and abutted against each other, and a connection adapter including a sleeve that holds the elastic sleeves inside is held, and each ferrule is fitted into the elastic sleeves. In the optical connector in which a pair of plug housings to be connected are coupled to the connection adapter, the outer circumference of the flange portion of the ferrule is provided. Part or all of the constituting surface forms a taper surface in a direction in which the cross-sectional area perpendicular to the axis decreases from the rear end of the ferrule to the tip thereof, and holds the ferrule of the plug housing. The inner peripheral surface of the part forms a tapered surface similar to the outer peripheral part of the flange of the ferrule, and when the plug is not connected, the outer peripheral surface of the flange part of the ferrule is the inner peripheral surface of the plug housing by the spring. When the pair of plugs to be connected is coupled to the adapter, the pair of ferrules are slightly pushed into the inside of the plug housing and the tapered surface of the outer periphery of the ferrule is tapered to the inner surface of the plug housing. Polarization maintaining structure, characterized in that the ferrule floats from the plug housing away from the surface. Fiber-optic connector.