JP2946424B2 - Connector with optical isolator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connector for connecting an optical fiber to an optical fiber, and more particularly to a connector with an optical isolator having an optical isolator attached to the connection portion.

[Conventional technology]

FIG. 9 is a view showing a conventional connector with an optical isolator.

As shown in the figure, a conventional connector with an optical isolator includes two rod lenses 83 and 88, two polarizers 84 and 85, and one Faraday rotator between two optical fibers 81 and 82. The Faraday rotation element 86 is arranged, and a cylindrical magnet 87 is attached so as to surround the outer periphery of the Faraday rotation element 86.

The light incident from the optical fiber 81 is converted into parallel light by the rod lens 83, and is incident on the polarizer 84. The incident light that has entered the polarizer 84 passes only specific linearly polarized light, and enters the Faraday rotator 86 to which a magnetic field is applied in the optical axis direction by the magnet 87. In the Faraday rotator 86, the plane of polarization of the linearly polarized light
Rotated 45 ゜.

Here, the polarization plane of the polarizer 85 is 45
フ ァ Because it rotates around the optical axis, the Faraday rotation element 86
The polarization plane of the light that has passed through coincides with the polarization plane of the polarizer 85. Therefore, the light that has passed through the Faraday rotation element 86 passes through the polarizer 85 as it is, is collected by the rod lens 88, and is incident on the optical fiber.

On the other hand, light incident from the optical fiber 82 side is converted into parallel light by the rod lens 88 and enters the polarizer 85. Then, the linearly polarized light that has passed through the polarizer 85 is incident on the Faraday rotation element 86, and its polarization plane is rotated by 45 ° around the optical axis.

As a result, the polarization plane of the light that has passed through the Faraday rotator 86 is in a direction at 90 ° to the polarization plane of the polarizer 84,
The light cannot pass through the polarizer 84, thereby blocking return light.

[Problems to be solved by the invention]

In the conventional connector with an optical isolator, the polarizers 84 and 85 and the Faraday rotator 86 need to be inserted between the optical fibers 81 and 82. It was necessary to reduce the loss of light going in the forward direction by making the light parallel or converging the light parallel to the optical fiber. However, for this reason, there has been a problem that the optical isolator becomes large and the number of parts increases.

Also, due to the large number of components, there are many reflections and losses due to the end faces of each optical component, and the loss of light going in the forward direction increases,
In addition, there is a problem that isolation becomes worse.

In addition, there is a problem that it is difficult to adjust the position between the components because of the large number of components.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a connector with an optical isolator that can reduce light loss without attaching a lens, reduce the size of an optical isolator, and reduce the number of parts. is there.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention comprises two optical fibers constituted by fiber-type polarizers, and shifts the polarization directions of the fiber-type polarizers by a predetermined angle (preferably 45 °) around the optical axis. A Faraday rotation element having a direct Faraday effect is provided at both or one of the ends where the two optical fibers are connected, and a magnet that applies a magnetic field in the optical axis direction to the Faraday rotation element is disposed. A connector with an optical isolator was constructed by mounting.

Here, the fiber-type polarizer is constituted by a fiber that transmits only one linearly polarized light component. In particular,
The optical fiber is composed of an absolutely single polarization optical fiber or a structure in which a polarization maintaining fiber is bent (usually, a birefringent optical fiber is wound a plurality of times).

The Faraday rotator having the Faraday effect is made of an oxide paramagnetic glass containing ions of Ce ³⁺ , Pr ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ or transition metal.

Further, it is preferable that the Faraday rotator is formed in a fiber shape by using a core having a Faraday effect and a clad surrounding the core, which is preferable because the fiber does not easily leak to light.

[Action]

By configuring the connector with an optical isolator as described above, the polarizer is replaced with a fiber-type polarizer that forms an optical fiber, so that an independent polarizer is not required, and a Faraday rotator is directly connected to this optical fiber. This eliminates the need for a conventional lens.

For this reason, the optical isolator can be reduced in size and the optical axis can be easily adjusted. Also, the number of parts can be reduced, and the position adjustment between the parts becomes easy.

Further, since a polarizer independent of the lens is unnecessary, reflection at the end faces of these components is eliminated, and an isolator with high isolation and low loss can be configured.

Further, the direction of the isolation can be easily changed only by changing the rotation direction of the two optical fibers around the optical axis.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a basic overall configuration of a connector with an optical isolator according to one embodiment of the present invention.

As shown in the figure, the connector with an optical isolator includes two fiber-type polarizers 1 and 2, and both ends of the two fiber-type polarizers 1 and 2 on the connected side are provided. The fiber type Faraday rotation elements 6 and 7 are connected. Ferrules 11 and 13 are attached to the outer circumferences of the fiber-type polarizers 1 and 2 and the fiber-type Faraday rotators 6 and 7, respectively. 9 is attached.

Next, each component of the connector with an optical isolator will be described.

First, fiber-type polarizers 1 and 2 consist of cores 1a and 2a and cladding 1
b, 2b.

This fiber type polarizer is a fiber that allows only one linearly polarized light component to pass therethrough, and is specifically configured using an absolutely single-polarization optical fiber that transmits only one of two orthogonal linearly polarized light components. Alternatively, by bending the polarization-maintaining fiber (usually by winding a birefringent optical fiber around a cylindrical drum), the loss of one of the two linearly polarized light components is increased while the other is reduced. May be configured to transmit only the polarized light component.

Here, the two fiber polarizers 1 and 2 are connected such that their polarization directions are shifted from each other by about 45 ° about the optical axis.

However, this angle of 45 ° is the angle at which the insertion loss is the smallest, and even if it deviates from 45 °, it can be configured as an isolator.

The fiber type Faraday rotators 6 and 7 are
a, 7a and claddings 6b, 7b are formed in the same shape.

Here, the cores 6a and 7a are constituted by Faraday rotation elements having a Faraday effect, and specifically, Ce ³⁺ , P
It is composed of an oxide paramagnetic glass containing ions of r ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ or transition metal.

The combined length of the cores 6a and 7a is a length necessary for rotating the plane of polarization of the light by 45 ° when the light passes through both.

The magnet 9 is formed in a cylindrical shape, and is arranged so as to apply a magnetic field in the optical axis direction to the cores 6a and 7a including the Faraday rotation element.

Then, the light that has entered from the core 1a side of the fiber-type polarizer 1 and has only one linearly polarized light component passes through the cores 6a and 7a of the fiber-type Faraday rotators 6 and 7 and changes its polarization plane by 45. After being rotated by ゜, the plane of polarization is rotated by 45 ° with respect to the core 1a in advance and directly enters the core 2a connected thereto.

On the other hand, the light that has entered from the core 2a side of the fiber-type polarizer 2 and has only one linear polarization component passes through the cores 7a and 6a of the fiber-type Faraday rotation elements 7 and 6 and has a polarization plane of 45%. Although it is rotated, when this light is about to enter the core 1a, it is orthogonal to the polarization plane of the core 1a. Therefore, this light does not eventually enter the core 1a, and an isolator can be configured.

If the polarization plane of the core 1a of the fiber-type polarizer 1 and the polarization plane of the core 2a of the fiber-type polarizer 2 are connected by being rotated by 45 ° around the optical axis in a direction opposite to the above case, the above-mentioned connection is obtained. Contrary to the embodiment, light incident from the fiber-type polarizer 2 is transmitted to the fiber-type polarizer 1, and light incident from the fiber-type polarizer 1 is not incident on the fiber-type polarizer 2. It will be.

When the fiber-type polarizing element 1 and the fiber-type polarizer 2 are connected in this manner, the directions of the polarization planes of both are simply shifted by 45 ° to either the counterclockwise direction or the clockwise direction.
The direction of the isolation can be easily changed.

The direction of the isolation can be easily changed by changing the direction of the magnet 9 and reversing the direction of the magnetic field applied to the fiber type Faraday rotators 6 and 7.

FIG. 2 is a diagram showing a method of connecting the fiber-type polarizers 1 and 2 and the fiber-type Faraday rotators 6 and 7.

First, as shown in FIG. 1A, two fiber polarizers 1 and 2 and two fiber Faraday rotators 6 and 7 are prepared.

Next, as shown in FIG.
And the fiber-type Faraday rotator 6 are connected by bonding or discharge fusion techniques such that both cores 1a and 6a face each other.

Similarly, the fiber type polarizer 2 and the fiber type Faraday rotator 7 are also connected.

Then, as shown in FIG. 1, ferrules 11 and 13 are attached to the outer circumference of these, and the polarization planes of both are connected at a position shifted by 45 ° around the optical axis, so that a connector with an optical isolator as shown in FIG. Can be configured.

3 and 4 are views showing a specific connection structure of the connector with an optical isolator, and FIG. 3 shows adapters A and B.
FIG. 4 is a side sectional view showing a state where a connector with an optical isolator is incorporated in the adapters A and B.

As shown in FIG. 3, a magnet 9 is attached to the adapters A and B, and a split sleeve 51 is attached inside the magnet 9.

Then, as shown in FIG. 4, ferrules 11 and 13 each having fiber type polarizers 1 and 2 attached thereto are inserted into the split sleeve 51, and plugs 55a and 55b are screwed and fixed to adapters A and B, respectively. Then, both fiber polarizers 1 and 2 are connected. 57a and 57b are positioning keys for the plugs 55a and 55b.

FIG. 5 is a view showing another embodiment of the connector with an optical isolator according to the present invention.

In the embodiment shown in the figure, the connection surface between the fiber polarizer 1 and the fiber Faraday rotator 6 and the connection surface between the fiber polarizer 2 and the fiber Faraday rotator 7 are inclined surfaces.

With this configuration, reflected light generated between the fiber-type polarizer 1 and the fiber-type Faraday rotator 6 and reflected light generated between the fiber-type polarizer 2 and the fiber-type Faraday rotator 7 can be removed. It is. Further, when the inclination angle is set to the Brewster angle, the polarization characteristics are also improved.

FIG. 6 is a view showing still another embodiment of the connector with an optical isolator according to the present invention.

In the embodiment shown in the figure, the core 6a of the fiber type Faraday rotator 6 is provided in the clad 1b of the fiber type polarizer 1 and at the end of the ore 1a. In order to achieve such a configuration, the core 6a may be inserted into the clad 1b, or a material in the core 1a may be doped to have a Faraday effect.

FIG. 7 is a view showing still another embodiment of the connector with an optical isolator according to the present invention.

In the embodiment shown in the figure, the fiber type Faraday rotator 6 is omitted and the fiber type Faraday rotator 7 is omitted.
Only the fiber type polarizer 2 is connected.

Even with such a configuration, the length of the core 7a in the fiber type Faraday rotator 7 may be any length as long as it is necessary to rotate light by 45 °. With this configuration, the number of parts can be further reduced. Further, the core 6a shown in FIG. 6 may be omitted and only the core 7a may be provided.

Although the core 6a and the core 7a have the same length in the embodiment shown in FIG. 1, the lengths may be different. In short, it is only necessary that the total length of the two is such that the polarization plane of the light is rotated by 45 °. When both lengths are the same, both fiber type Faraday rotation elements 6,
Since the shape of the fiber polarizers 1 and 2 to which 7 is attached is the same, there is no need to distinguish them.

FIG. 8 is a view showing still another embodiment of the connector with an optical isolator according to the present invention.

In the embodiment shown in the drawing, a thin-film Faraday rotator 15 such as garnet is
It is configured with attached.

〔The invention's effect〕

As described above in detail, according to the connector with an optical isolator according to the present invention, unlike the conventional one, the two optical fibers are constituted by the fiber type polarizer, and the ends to which the two optical fibers are connected are connected. Since the Faraday rotator is connected to both or either of them, the following excellent effects can be obtained.

Since the conventional lens is not required, the size of the optical isolator can be reduced. Also, the number of parts can be reduced, and the adjustment of the optical axis between the parts can be simplified.

In the conventional optical isolator, reflection loss from the end faces of the lens and the polarizer was unavoidable. However, in the present invention, there is no such loss, and a low-loss isolator can be configured with high isolation.

It is possible to easily change the direction of the isolator simply by reversing the direction of displacement around the optical axis when connecting two optical fibers.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic overall configuration of a connector with an optical isolator according to an embodiment of the present invention, and FIG. 2 is a diagram showing a method of connecting fiber type polarizers 1, 2 and fiber type Faraday rotator elements 6, 7. FIGS. 3 and 4 are diagrams showing specific connection structures of the connector with an optical isolator, and FIGS.
7 and 8 are views showing another embodiment of the connector with an optical isolator according to the present invention, and FIG. 9 is a view showing a conventional connector with an optical isolator. In the figure, 1,2 ... Fiber type polarizer, 6,7 ... Fiber type Faraday rotator, 15 ... Faraday rotator, 9 ...
Is a magnet.

────────────────────────────────────────────────── (5) References JP-A-64-47087 (JP, A) JP-A-62-86326 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 6/26 G02B 6/00

Claims (2)

(57) [Claims] 1. A connector with an optical isolator, wherein an optical isolator is attached to a connection portion between two optical fibers, wherein the two optical fibers are constituted by a fiber-type polarizer, and a polarization direction of the two optical fibers. Are arranged at a predetermined angle around the optical axis, a Faraday rotator having a direct Faraday effect is provided at both or one of the connected ends of the two optical fibers, and furthermore, an optical A connector with an optical isolator, wherein a magnet for applying an axial magnetic field is mounted. 2. The connector with an optical isolator according to claim 1, wherein said Faraday rotation element is formed in a fiber shape by a core having a Faraday effect and a clad surrounding said core.