WO2003098324A1

WO2003098324A1 - Ferrule fixed type optical isolator and method for manufacturing the same

Info

Publication number: WO2003098324A1
Application number: PCT/JP2003/006350
Authority: WO
Inventors: Hirotaka Kawai
Original assignee: Fdk Corporation; Nagasawa, Mitsuru
Priority date: 2002-05-22
Filing date: 2003-05-21
Publication date: 2003-11-27
Also published as: JP3934989B2; JP2003337304A

Abstract

An optical isolator comprising a combination of an optical isolator body including a Faraday element, a polarizer and an analyzer arranged in front and rear thereof, and permanent magnets arranged on the outside thereof, and a holder for holding the optical isolator body. The optical isolator body comprises two elongated planar permanent magnets disposed oppositely at an interval, and the polarizer, the Faraday element and the analyzer disposed between the permanent magnets. The holder has a groove made in one side of a tubular section having a central through hole and the optical isolator body is inserted into that groove while exposing the outer side face of the permanent magnets and secured in place. The holder can be fixed to the end face of a ferrule on the side opposite to the groove.

Description

Description Ferrule-mounted optical isolator and its manufacturing method

The present invention relates to an optical isolator, and more particularly, to a ferrule-mounted optical isolator having a structure in which an optical isolator main body is inserted and fixed in a concave groove of a holder, and the holder can be directly mounted on an end face of the ferrule, and a manufacturing method thereof. About the method. Background art

As is well known, an optical isolator is a non-reciprocal optical device that allows light to pass in one direction but blocks light in the opposite direction. For example, in an optical communication system using a semiconductor laser as a light source, It is used to prevent light from returning to the light source side due to reflection. In this type of optical isolator, a polarizer, a Faraday element, and an analyzer are arranged in the optical axis direction in that order, and a permanent magnet that applies a magnetic field in the optical axis direction to the Faraday element is provided outside the Faraday element. The configuration is common. The Faraday element rotates the plane of polarization of incident light by 45 degrees by the magnetic field of a permanent magnet, and the polarizer and analyzer are oriented so that the optical axis (polarization transmission axis) is 45 degrees different. .

In recent years, a configuration has been proposed in which an optical isolator is directly mounted on an end face of a ferrule of an optical fiber in order to further reduce the distance between the input and output devices and reduce the size. The optical isolator to be mounted has a configuration in which a polarizer, a Faraday element, and an analyzer are inserted and fixed in a cylindrical permanent magnet, or a structure in which a polarizer, a Faraday element, and an analyzer are laminated in advance with a bonding agent and then mounted inside a permanent magnet. Configuration. In any case, the polarizer and analyzer have the same specifications, and one is rotated about the optical axis with respect to the other to adjust the direction so that the optical axis differs by 45 degrees. The configuration in which a polarizer, a Faraday element, and an analyzer (collectively called optical elements) are inserted into a cylindrical permanent magnet while maintaining the optically necessary effective area is small enough to accommodate the outer diameter of the ferrule. Is difficult. This is because the smaller the size, the more difficult it becomes to fix the optical element, and the smaller the bonding area of the optical element, the lower the bonding strength. The structure in which the polarizer, the Faraday element, and the analyzer are laminated (laminated) with an adhesive in advance is relatively easy to assemble, but damage is caused when high-power light passes through due to the presence of the adhesive in the optical path. Problems are likely to occur, for example, and the use (use condition) is restricted. In any case, man-hours / parts for adjusting the direction of the optical axis are required, resulting in high costs. Disclosure of the invention

An object of the present invention is to provide a ferrule-mounted optical isolator that can firmly and easily fix each optical element without employing a laminate structure, and that can be reduced in size and diameter as a whole, and a method of manufacturing the same. It is to be.

In order to achieve the above and other objects, one aspect of the present invention is to provide a Faraday element, a polarizer and an analyzer arranged before and after the Faraday element, and a permanent element disposed outside the Faraday element. An optical isolator including only an optical isolator main body including a magnet and a holder that holds the optical isolator main body,

The optical isolator main body includes two elongated flat permanent magnets facing each other at an interval, and a polarizer, a Faraday element, and an analyzer disposed between the permanent magnets. And

The holder has a concave groove formed on one side of a cylindrical portion having a central through-hole, and the optical isolator body is inserted into the concave groove of the holder with the outer surface of the permanent magnet exposed. The holder is fixed, and the holder can be attached to the ferrule at an end face opposite to the concave groove.

Another aspect of the present invention is a method for manufacturing an optical isolator, —Prepare a pair of elongated flat permanent magnets,

A Faraday element is disposed on the one permanent magnet so as to cross its longitudinal direction, and a polarizer and an analyzer are disposed on the other permanent magnet at predetermined intervals so as to cross the longitudinal direction,

A concave groove is formed at one end thereof, and the polarizer, the Faraday element, and the analyzer are arranged in this order in the concave groove of the substantially cylindrical holder attached to the ferrule at the other end. The two permanent magnets are opposed to each other so as to be arranged along with each other.

Other features and objects of the present invention will become apparent from reading the description of the present specification with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE FIGURES

1A and 1B are perspective views showing one embodiment of a ferrule-mounted optical isolator according to the present invention.

2A and 2B are explanatory views of the ferrule-mounted optical isolator according to the present invention.

For a more complete understanding of the present invention and its advantages, refer to the following description in conjunction with the accompanying drawings. BEST MODE FOR CARRYING OUT THE INVENTION

At least the following matters will be made clear by the description in the present specification and the description of the accompanying drawings.

1A and 1B are perspective views showing an embodiment of an optical isolator equipped with a ferrule according to the present invention. FIG. 1A is an exploded state, FIG. 1B is a state after being set up, and FIG. Each is shown. FIGS. 2A and 2B are explanatory diagrams, FIG. 2A showing a partially broken side view, and FIG. 2B showing a front view. Ferrule-mounted optical device The optical isolator 10 includes an optical isolator main body 24 having a polarizer 14 and an analyzer 16 disposed before and after the Faraday element 12, and a pair of permanent magnets 20 and 22 disposed outside thereof. It consists of a combination with a holder 30 that holds the isolator body 24.

The main body of the optical isolator 24 has two elongated flat plate-like permanent magnets 20 and 22 opposed to each other with a space between them, and a polarizer 14, a Faraday element 12, and an analyzer 1 are arranged therebetween. Assembled so that 6 is sandwiched. The polarizer 14 and the analyzer 16 are made of, for example, rutile crystal or the like, and are processed into the same strip shape (rectangular flat plate shape) so that their optical axes are different from each other by 45 degrees. For example, polarizer 14 has its optic axis set in a direction parallel (or perpendicular) to its long side, whereas analyzer 16 has its optic axis set at 45 degrees to its long side. I have. The Faraday element 12 is made of a magnetic garnet single crystal (for example, Bi-substituted rare earth iron garnet single crystal), and is processed into a strip (rectangular flat plate) having the same shape as the polarizer 1.4 ゃ analyzer 16 described above. is there. Its thickness is set so that incident light of the used wavelength rotates its polarization plane by 45 degrees.

The permanent magnets 20 and 22 are made of, for example, SmCo-based rare earth sintered magnets, and are magnetized in the longitudinal direction. The width dimension of the elongated plate-shaped permanent magnets 20 and 22 is set slightly larger than the long side dimension of an optical element such as a polarizer. Since the permanent magnets 20 and 22 are basically in the form of a flat plate, they are easy to process and the production cost is low. The Faraday element 12 is bonded to one of the permanent magnets 20 on its long side, and the polarizer 14 and the analyzer 16 are bonded to the other permanent magnet 2 on their long sides. 2 are surface-bonded at a predetermined interval (interval larger than the thickness of the Faraday element 12). As described above, since each optical element is surface-bonded on the long side surface, the bonding area increases, and the fixing strength increases. The opposing surfaces of the permanent magnets 20 and 22 (the surfaces to which the optical elements are bonded) are polished with a grindstone in advance. Further, as shown in FIG. 1, it is preferable that chamfering 26 is performed at least slightly on the ridge portion in the longitudinal direction of the surface where the optical elements of the permanent magnets 20 and 22 are bonded. Then, using the chamfer 26, one of the short side surfaces of the optical element is used. This is because the adhesive can also be placed on the portion, so that the adhesive strength between the permanent magnet and the optical element can be further increased.

An optical isolator main body 24 is formed by combining a permanent magnet 22 having a polarizer 14 and an analyzer 16 bonded thereto and a permanent magnet 20 having a Faraday element 12 bonded thereto facing each other. In this way, the polarizer 14 and the analyzer 16 whose optical axes are set in a predetermined direction in advance are bonded on the same plane of the same permanent magnet 22 so as to be assembled. Desired isolator characteristics can be achieved without optical axis adjustment. Also, since each optical element is individually fixed to a permanent magnet, there is no air layer between the optical elements and no adhesive layer, so that there is no problem such as damage to high-power light.

The holder 30 has a structure in which a concave groove 36 is formed on one side of a cylindrical portion 34 having a central through hole 32 in a direction perpendicular to the central axis. In other words, it has a cylindrical portion 34 having a central through hole 32 and a pair of holding pieces 38 integrally projecting from one side in the direction of the central axis. In this structure, grooves 36 are formed immediately. Therefore, the outer peripheral surface of the holding piece 38 is flush with the outer peripheral surface of the cylindrical portion 34. The optical isolator body 24 is inserted into the concave groove 36 and fixed by bonding. Hold the one permanent magnet 20 with the Faraday element 12 bonded to it and the other permanent magnet 22 with the polarizer 14 and the analyzer 16 bonded so that the optical element bonding surfaces face each other and become parallel. Insert into the 30 four grooves 36, and fix the whole side (3 sides) where the permanent magnets 20 and 22 are in contact with each other by gluing. Since the contact area is large, sufficient fixing strength can be secured. As a work, it is preferable to separately insert one permanent magnet into the concave groove 36 and adhere it, and then fit the other permanent magnet into the concave groove 36 and adhere it. This is because the polarizer 'analyzer and the Faraday element are held by separate permanent magnets on only one side each, so that the thermal stress with respect to temperature fluctuation is reduced.

In order to insert the long and narrow permanent magnets 20 and 22 into the concave groove 36, The angle is uniquely determined. Holder when permanent magnets 20 and 22 are inserted into groove 36

The outer corners of the permanent magnets 20 and 22 are preliminarily subjected to an inclined surface (or rounded) so as to substantially conform to the outer peripheral shape of 34. The inclined surface is indicated by reference numeral 28. As a result, the permanent magnets 20 and 22 do not excessively protrude from the outer peripheral surface of the holder 30 and the outer diameter of the optical isolator can be reduced. Further, by making the permanent magnets 20 and 22 exposed, further miniaturization can be realized. Each optical element is protected by the holding portion 38 of the holder 30 and the permanent magnets 20 and 22. Further, since the permanent magnets 20 and 22 and the holder 30 are fixed so that the permanent magnets 20 and 22 are sandwiched by the holding portion 38 of the holder 30, vibrations from various directions and The mechanical strength against impact is improved.

The holder 30 can be attached to the ferrule 40 at the end opposite to the concave groove 36. As shown in Fig. 2A, the center through hole 32 of the holder 30 is shaped so that the cabillary part 42 of the ferrule 40 just fits, and the holder end face and the ferrule end face are abutted in the fitted state. Join and fix. When the holder and ferrule are both made of stainless steel, they are fixed at a plurality of locations (for example, eight locations) around the perimeter by welding.

Each optical element (polarizer 14, Faraday element 12, analyzer 16) is attached to permanent magnets 20 and 22 so as to be slightly inclined from the state perpendicular to the optical axis in order to prevent end face reflection. Since the optical element bonding surfaces of the permanent magnets 20 and 22 are flat surfaces, and the optical elements are also strip-shaped, bonding in an inclined state is easy. Also the capillaries

The tip surface of 42 is also polished so as to be slightly inclined from the state perpendicular to the optical axis (for example, 8 degrees). By providing such an inclination, reflected return light is prevented. Industrial applicability

According to the embodiment of the present invention described above, the main body of the optical isolator has an elongated flat plate shape. The two permanent magnets are arranged facing each other with a space between them, and the polarizer, Faraday element, and analyzer are sandwiched between them, so the optical element is firmly and easily fixed. it can. In addition, since it is not necessary to laminate the optical elements, there is no risk of damage such as damage to high-power light. Further, the holder has a structure in which a concave groove is formed on one side of a cylindrical portion having a central through hole, and the optical isolator body is inserted and fixed in the concave groove, so that the permanent magnet is exposed, and the outer periphery of the permanent magnet is formed. By forming a beveled surface or forming a round shape, it is possible to further reduce the size and diameter.

When the polarizer and analyzer are processed into strips so that their polarization axes are different from each other by 45 degrees, and fixed to a permanent magnet on their long sides, the isolator characteristics appear without adjustment, and adjustment work is required. This eliminates the need for man-hours and parts required for production, making it possible to manufacture at low cost. In addition, the center through hole of the holder is shaped so that the cavities of the ferrule fit together, and the holder end face and the ferrule end face are abutted and fixed in the fitted state, so that the optical isolator can be connected to the ferrule end. The joining strength is further improved. Having described preferred embodiments of the invention in detail, various changes, substitutions, and alterations therein may be made without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood.

Claims

The scope of the claims

1. An optical isolator main body including a Faraday element and polarizers and analyzers disposed before and after the Faraday element, and a permanent magnet disposed outside thereof, and a holoreda holding the optical isolator main body. An optical isolator having a combination,

The optical isolator main body includes two elongated flat plate-shaped permanent magnets facing each other at an interval, a polarizer, a Faraday element, and an analyzer disposed between the permanent magnets. ,

The holder has a concave groove formed on one side of a cylindrical portion having a central through-hole, and the optical isolator body has a groove in the concave groove of the holder in a state where an outer surface of the permanent magnet is exposed. The holder is inserted and fixed, and the holder can be attached to the ferrule at the end face opposite to the concave groove.

2. The holder is formed in a cylindrical shape, and when the optical isolator main body is inserted into the (13 groove) of the holder, the outer surface of the permanent magnet of the optical isolator main body has substantially the outer peripheral shape of the holder. 2. The optical isolator according to claim 1, wherein the optical isolator is shaped to fit.

3. The polarizer and the analyzer are processed into a strip shape so that their optical axes are different from each other by 45 degrees, and are fixed to the permanent magnet on the long side surfaces thereof, thereby preventing the polarizer and the analyzer. The optical isolator according to claim 1, wherein the isolator characteristic is developed by the adjustment.

4. The optical isolator according to claim 1, wherein the center through-hole of the holder has a shape in which a capillary portion of a ferrule is fitted, and the end face of the holder and the end face of the ferrule are abutted and fixed in the fitted state.

5. A method for manufacturing an optical isolator,

Prepare a pair of elongated flat permanent magnets,

The one permanent magnet is provided with a Faraday element so as to cross the longitudinal direction thereof, and the other permanent magnet is provided with a predetermined interval so as to cross the longitudinal direction thereof and a polarizer. Arrange the analyzer and

6. Insert and fix either the permanent magnet provided with the Faraday element or the permanent magnet provided with the polarizer and the analyzer in the groove of the holder, and then fix the other permanent magnet. 6. The method for manufacturing an optical isolator according to claim 5, wherein the polarizer, the Faraday element, and the analyzer are opposed to each other so as to be arranged along the optical axis in this order.