JP2957611B2 - Connector type optical isolator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small connector type optical isolator used between fibers to remove return light to a laser diode (LD) in an optical communication system or the like.

[Conventional technology]

2. Description of the Related Art Conventionally, in a small optical isolator used for an optical communication system or the like, an isolator element is housed in a holder and used for light transmitted in space. An optical isolator of this shape cannot be used as it is and cannot be used without a holder for aligning and fixing the optical axis of the optical isolator and the optical isolator, and is not functional. Also,
A fiber-coupled type inserted between fiber connectors has also been devised. However, there is a space for transmitting light in the optical isolator, and the coupling loss is rather increased.

On the other hand, an optical isolator using a garnet thick film can be easily miniaturized, but since the Faraday rotation angle of the internal Faraday rotation element varies depending on the wavelength used and the temperature environment,
The best isolation was not always obtained.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems by embedding an optical isolator in a fiber-to-fiber coupling connector, which eliminates optical axis adjustment, facilitates polarization plane adjustment, and varies the Faraday rotation angle that varies depending on the use environment. It is an object of the present invention to provide a functional and versatile connector-type optical isolator that can easily cope with environmental conditions by finely adjusting the magnetic field from the outside.

B. Configuration of the Invention [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention adheres a Faraday rotation element by sandwiching a Faraday rotation element between polarizing crystal plates in an internal split sleeve of an optical connector for coupling optical fiber connectors. The optical axis of each polarizing crystal plate is aligned with the Faraday rotation direction 45 °, and an optical isolator element with a 45 ° inclination is embedded in the center, and a cylindrical magnetic field generator that generates a magnetic field in the axial direction A compact and functional connector-type optical isolator is provided by adopting a structure in which a split sleeve incorporating the above-mentioned optical isolator element is located at the center. Further, the present optical isolator is a connector-type optical isolator having a magnetic field generator movable along the optical axis of the optical isolator so that the isolation of the isolator element can be finely adjusted.

That is, in a connector used for connecting optical fiber connectors, an optical isolator element is provided in a split sleeve in the connector, and a magnetic field that magnetically saturates the Faraday rotation element in the optical isolator element from outside the split sleeve. A connector-type optical isolator characterized in that a generator is provided outside a split sleeve. In the connector-type optical isolator according to the first aspect, the magnetic field generator installed around the split sleeve has a structure capable of moving in the light propagation direction, so that the Faraday rotation element inside the split sleeve can be moved. The connector type characterized in that the magnetic field generator has a structure that can be moved in the light propagation direction so that the Faraday rotation angle can be adjusted so that the isolation applied to the usage environment can be obtained by changing the applied magnetic field An optical isolator is provided.

[Action]

By installing a small optical isolator element in the middle of the connector that couples the optical fiber connectors, disposing a magnetic field generator outside the connector, and making it a movable structure,
A connector-type optical isolator that is compact, does not require optical axis adjustment, is easy to adjust the polarization plane, and can cope with an external temperature environment or the like.

〔Example〕

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

FIG. 1 is a schematic sectional view of a connector-type optical isolator for explaining an embodiment of the present invention.

As a magnetic field generator, a cylindrical magnet 1 magnetized in the axial direction is used. A split sleeve 2 for accommodating an optical fiber connector is accommodated in the center of the magnet 1, and an optical isolator element is provided in the center of the split sleeve. 6 are arranged.

The configuration of the optical isolator element 6 is such that the polarizing crystal plates 3 and 4 have a thickness of 0.8 mm, an insertion loss of 0.05 dB, and an extinction ratio of 58 dB. A rutile polarizing crystal plate provided with a non-reflective coating for air was used. As the Faraday rotator, (measured at 25 ° C.) the Faraday rotation angle 45 deg, the insertion loss 0.2 dB, was subjected to non-reflection coating for pairs adhesive on both sides with extinction ratio _{38dB (GdBi) 3 (AlFeGa)} 5 O Garnet thick film of ₁₂ composition 5
Was used. Each measurement wavelength is 1.32 μm. The magnet is a ferrite plastic magnet,
The dimensions were φ5 × φ2.7 × 5 mm. The shape of the split sleeve used is φ3 × φ2.5 × 15 mm.

The assembly was performed by adjusting the polarization axis of a 5 mm square rutile polarizing crystal plate and a garnet thick film and bonding them with an optical adhesive. The material of the optical isolator element thus obtained was magnetically saturated and evaluated. As a result, characteristics of an insertion loss of 0.4 dB and an isolation of 35 dB were obtained at a room temperature of 25 ° C. and a measurement wavelength of 1.31 μm. The bonded optical isolator element was punched into φ2.2 mm, housed in a split sleeve, and bonded and fixed. During adhesive curing, the split sleeve was supported and fixed from both ends.

The connector-type optical isolator assembled in this manner facilitates the coupling between fiber connectors, and the movement of the magnet causes a temperature environment of 25 ± 5 ° C. and a wavelength variation of 1.31 ± 0.05.
It has a high isolation of more than 30dB under the environment fluctuation of μm.

C. Effects of the Invention [Effects of the Invention] According to the present invention, an optical isolator to be installed between optical fibers can be easily installed without labor such as optical axis alignment,
A high performance optical isolator can be supplied with a simple structure that can respond to changes in environmental conditions.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical isolator according to an embodiment of the present invention. The arrow in the figure indicates the direction of the magnetic field. 1 ... magnet, 2 ... split sleeve, 3 ... polarizing crystal plate (analyzer), 4 ... polarizing crystal plate (polarizer), 5 ...
Garnet thick film, 6 ... optical isolator element.

Claims (2)

(57) [Claims] An optical isolator element is provided in a split sleeve in the connector, and a Faraday rotator element in the optical isolator element is magnetically provided from outside the split sleeve. A connector type optical isolator characterized in that a magnetic field generator for saturation is provided outside a split sleeve. 2. The connector type optical isolator according to claim 1, wherein the magnetic field generating device installed around the split sleeve has a structure capable of being moved in the light propagation direction, so that the inside of the split sleeve can be moved. The magnetic field generator has a structure that can be moved in the light propagation direction to change the magnetic field applied to the Faraday rotation element and to adjust the Faraday rotation angle so that isolation suitable for the usage environment can be obtained. Connector type optical isolator.