JPH04233510A - Optical isolator - Google Patents

Abstract

PURPOSE:To offer a small-sized optical isolator having high reliability and productivity which can be used in the field of optical communication, etc. CONSTITUTION:Polarizing plates 151, 152, as polarizers and a magneto-optical element 140 are housed in a cylindrical outer case 110 with a common optical axis. The polarizing plates 151, 152, magneto-optical element 140, and magnets 131, 132, 133 as a means to produce a magnetic field are housed in an inner case 120, which is then housed in the outer case 110 above described. Thereby, the obtd. small-sized isolater has excellent reliability and can be easily adjusted for assembling.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact optical isolator that can be used particularly in the field of optical communications.

0002

[Prior Art] For example, a small optical isolator that can be incorporated into an optical communication module, etc. has a through hole with a substantially square shape formed in a permanent magnet as a magnetic field generating means, and a magneto-optic Faraday glass as an element and a polarizing plate as a polarizer were inserted and fixed.

0003

[Problems to be Solved by the Invention] In the conventional optical isolator as described above, a Faraday glass or a polarizing plate is directly inserted and fixed into a through hole of a permanent magnet.
Since these optical components are extremely small and easily damaged, there is a high risk of damaging these components during insertion work. Furthermore, it is extremely difficult to directly and accurately arrange such small optical components, which are not necessarily easy to precisely process, in a predetermined positional relationship. There was also a risk that they would not be able to demonstrate their abilities. Further, after arranging each of these optical components, it is necessary to adjust the angle of the two polarizing plates so that the polarization planes of the two polarizing plates have a predetermined relationship, but this angle adjustment has been difficult with conventional optical isolators. In addition, conventional optical isolators generally use organic adhesives to fix each optical component, but this organic adhesive has the problem that it is not always reliable depending on the conditions of use. be.

The present invention was made against the above-mentioned background, and it is an object of the present invention to provide an optical isolator that has excellent reliability and is easy to assemble and adjust.

[0005]

[Means for Solving the Problems] The present invention solves the above-mentioned problems by having the following configurations.

(1) Two polarizers arranged with different transmission polarization planes and a common optical axis; a magneto-optical element arranged between these polarizers with a common optical axis; An optical isolator comprising a magnetic field forming means for forming a magnetic field in a magneto-optical element, wherein at least the polarizer and the magneto-optical element are housed in a cylindrical outer case with a common optical axis, and the two polarizers A configuration characterized in that one or more of the magneto-optical element and the magnetic field forming means are housed in an inner case, and the inner case is housed in the outer case.

(2) In the optical isolator according to configuration 1, the cylindrical outer case has a cavity in the cylinder having a circular cross-sectional shape, and the inner case has an outer shape that is different from the outer case. A configuration characterized in that it is cylindrical in shape and has an outer diameter approximately equal to the inner diameter of the cavity.

(3) In the optical isolator according to configuration 2, the two polarizers are housed in separate inner cases, and these inner cases are housed in the outer case. .

(4) In the optical isolator according to any one of structures 1 to 3, a permanent magnet is used as the magnetic field generating means, and the permanent magnet is housed in an outer case.

(5) The optical isolator according to configuration 4, wherein the permanent magnet is composed of a plurality of parts, and these permanent magnets are arranged in the outer case so as to surround the magneto-optical element. Isolator.

[0011]

[Operation] According to configuration 1, each optical component is housed in the outer case, at least one polarizer is housed in the inner case, and the inner case is housed in the outer case. Compared to the conventional case of inserting and fixing other optical components into the through-hole of a permanent magnet, assembly, polarizer angle adjustment, etc. are significantly easier. Furthermore, according to configurations 2 and 3, the angle of the polarizer can be adjusted by rotating the inner case with respect to the outer case after inserting the inner case containing the polarizer into the outer case, making the adjustment even easier. Become. Furthermore, according to configurations 4 and 5, it is possible to obtain an optical isolator that is smaller, more compact, and easier to assemble and adjust.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a longitudinal sectional view of an optical isolator according to a first embodiment of the present invention, and FIG. 2 is an assembled view of the first embodiment. Hereinafter, a first embodiment of the present invention will be described in detail with reference to these drawings.

In the figure, 110 is an outer case, 120 is an inner case, 131, 132, 133 are magnets serving as magnetic field generating means, 140 is a magneto-optical element, and 1 is a magneto-optical element.
51 and 152 are polarizing plates.

The outer case 110 is made of non-magnetic stainless steel with an outer diameter of 3 to 4 mmφ and an inner diameter of 2.5 to 3.7 mmφ (thickness of 0
．． It is formed into a cylindrical shape with a length of about 1 to 0.4 mm) and a length of about 2 to 3 mm. Inside the outer case 110, an inner case 120, a magnet 132, a polarizing plate 152, and a magnet 133 are housed and fixed.

The inner case 120 is a cylindrical case that has an outer diameter that is approximately the same as the inner diameter of the outer case, and can be stored in the outer case 110 with good fit, and has a length of 1 to 2 mm.
, material and thickness are approximately the same as the outer case 110. Figure 2
As shown in the figure, the inner case 120 has a magnet 131.
And the polarizing plate 151 is inserted and fixed.

The magnet 131 is made of a rare earth permanent magnet or the like with a thickness of 0.
It is formed into a disc shape with an inner and outer diameter of 5 mm, with a light passage hole 13 in the center.
1a, and has an outer diameter that allows it to be inserted into the inner case 120 with good fit. As shown in Figure 2,
This magnet 131 is press-fitted and fixed into the inner case 120 with its left end face aligned and with such force that the outer diameter of the inner case 120 is not deformed.

The polarizing plate 151 is composed of a well-known birefringent crystal plate or the like, and converts the light passing therethrough into linearly polarized light whose plane of polarization is a specific plane including the traveling direction of the light. This polarizing plate 151 is a rectangular plate-like body with a thickness of 0.2 to 0.5 mm, the length of the diagonal being approximately equal to the inner diameter of the inner case 120, and as shown in FIG. The magnet 131 is housed in the inner case 120 and is adhesively fixed to the inner peripheral surface of the inner case 120 and one end surface of the magnet 131. The magnet 132 is made of a rare earth permanent magnet or the like, and has an outer diameter approximately equal to the inner diameter of the outer case 110 and a thickness of 0.5 mm.
The magneto-optical element 140 is formed into a disc-shaped body with an inner and outer diameter of 5 mm, and a rectangular storage hole 132a is formed in the center, and the magneto-optical element 140 is stored in this storage hole 132a as shown in FIG. This is what I did.

The magneto-optical element 140 rotates the plane of polarization of passing light by a predetermined angle (45°) using the Faraday effect (magneto-optic effect).
A well-known Bi-substituted garnet thick film is used. The magneto-optical element 140 is formed in a shape and size that allows it to be accommodated in the accommodation hole 132a of the magnet 132 with good fit.

The polarizing plate 152 has the same structure as the polarizing plate 151 except for the dimensions. This polarizing plate 1
52 is a rectangular plate-like body with a thickness of 0.5 mm, the distance between the diagonals is approximately equal to the inner diameter of the outer case 110, and the inner and outer sides are square.
As shown in FIG. 2, the magnet 133 is housed in the outer case 110 and adhesively fixed to the inner peripheral surface of the outer case 110 and one end surface of the magnet 133. In this case, this polarizing plate 152 and the polarizing plate 1
51 are arranged with the angular relationship of their polarization planes adjusted such that their polarization planes form an angle of 45 degrees with each other.

The magnet 133 is made of a rare earth permanent magnet or the like and has an outer diameter approximately equal to the inner diameter of the outer case 110 and a thickness of 0.5 mm.
It is formed into an inner and outer disc-shaped body, with a light passing light 133a formed in the center, and has an outer diameter that allows it to be inserted into the outer case 110 with good fit. As shown in FIG. 2, the magnet 133 is press-fitted into the outer case 110 with its right end aligned and fixed with a force that does not deform the outer diameter of the outer case 110.

Note that the inner case 12 is located inside the outer case 110.
0. When storing and fixing the magnet 132, the polarizing plate 152, and the magnet 133, first, the magnet 133 is press-fitted into the outer case 110 with their right ends aligned, and then the polarizing plate 152 is fixed.
is inserted into the outer case 110, the right end surface of the polarizing plate 152 is adhesively fixed in contact with the left end surface of the magnet 133, and then the magnet 132 with the magneto-optical element 140 housed and fixed therein is inserted into the outer case 110. and then fix the polarizing plate 1 with adhesive.
51 and the magnet 131 are housed and fixed therein, the inner case 120 is inserted into the outer case 110. After that, case 1
20 is rotated within the outer case 110 to adjust the angle so that the planes of polarization of the polarizing plates 151 and 152 form exactly 45 degrees. After this adjustment is completed, inner case 1
20 is fixed to the outer case 110 by means of soldering or the like.

In the optical isolator configured as described above, light such as a laser beam traveling from the left side to the right side in the figure (outgoing light)
When the light enters through the light transmission hole 131a of the magnet 131, the light is linearly polarized by the polarizing plate 151, and further, the linearly polarized light is changed by 45 degrees in its polarization plane by the magneto-optical element 140. The light passes through the polarizing plate 152 and is emitted to the outside through the light passing hole 133a of the magnet 133. On the other hand, light traveling in the opposite direction to this light in the figure, that is, light such as return light traveling from the right side to the left side in the figure (return light) passes through the polarizing plate 152 and becomes linearly polarized light. The linearly polarized light is rotated by 45° again by passing through the magneto-optic element 140. in this case,
Since the direction of rotation of this return light is the same direction as the rotation direction of the above-mentioned outbound light in terms of absolute coordinates, the polarization plane of the return light that has passed through the magneto-optical element 140 is the same as that of the polarization plate 151.
The light makes an angle of 90° with the plane of polarization, and cannot pass through the polarizing plate 151. This provides optical isolation.

According to this embodiment, each optical component is housed in the outer case 110, and one polarizing plate 15
1 is stored in the inner case 120 and the inner case 120 is stored in the outer case 110. After inserting the inner case 120 containing the polarizing plate 151 into the outer case 110, the inner case 120 is inserted into the outer case 110. 110, the angle of the polarization plane between the polarizing plate 151 and the polarizing plate 152 can be adjusted accurately and easily, and other optical components can be directly inserted and fixed into the through hole of the permanent magnet as in the conventional case. The assembly work is easier than in the case where the optical components are assembled, and furthermore, it is possible to reduce the risk of damaging the optical components during assembly. In addition, the magneto-optical element 1
40 is stored and fixed in advance in the storage hole 132a of the magnet 132, and this magnet 132 is stored in the outer case 110, and the magnet 131 is placed between the magneto-optical elements 140.
and 133 in the outer case 110,
Furthermore, it facilitates assembly and allows the device to be made small and compact while ensuring a predetermined magnetic field strength.

(Second Embodiment) FIG. 3 is a longitudinal sectional view of an optical isolator according to a second embodiment of the present invention, and FIG. 4 is an assembled view of the second embodiment. A second embodiment of the present invention will be described in detail below with reference to these drawings. The basic configuration of each of the embodiments described below is the same as that of the first embodiment described above, and each component having the same function is approximately the same as that of the first embodiment described above. These detailed explanations are omitted.
In the following, the simple functions of each component and the differences from the first embodiment will be mainly explained. In this embodiment, two polarizing plates 2
51 and 252 are housed and fixed in inner cases 221 and 222, respectively, these inner cases 221 and 222 are housed in outer case 210, and two polarizing plates 251 and 2
52 can be rotated and adjusted independently within the outer case 210, thereby increasing the degree of freedom in adjusting the angle of the polarizing plate and making the assembly work easier. Note that the two inner cases 221 and 222 are provided with polarizing plates 25.
1 and 252, magnets 231 and 233 are press-fitted and fixed, respectively, and a magnet 232 with a magneto-optical element 240 inserted and fixed is placed between the two inner cases 221 and 222. , the configuration is substantially the same as that of the first embodiment described above. In addition, in FIG. 3, symbols 231a, 23
3a is a light passage hole, and 232a is a storage hole.

(Third Embodiment) FIG. 5 is a longitudinal sectional view of an optical isolator according to a third embodiment of the present invention, and FIG. 6 is an assembled view of the third embodiment.

In this embodiment, three magnets 331 and 332 are used.
, 333, one polarizing plate 351 and the magneto-optical element 34
0 are placed in between, and these are housed in one inner case 320, and this inner case 320 is inserted into the outer case 31.
At the same time, the other polarizing plate 352 and magnet 310 are directly stored and fixed in the outer case 310. By storing the magneto-optical element in the inner case in advance, the assembly work is easy. The aim is to streamline the process. In addition, in FIG. 5, 331a, 332a, 333
a, 334a are light passing holes.

(Fourth Embodiment) FIG. 7 is a longitudinal sectional view of an optical isolator according to a fourth embodiment of the present invention, and FIG. 8 is an assembled view of the fourth embodiment.

In this embodiment, two magnets 431 and 43
2, one polarizing plate 451 and the magneto-optical element 440 are arranged alternately and housed and fixed in the first inner case 421, and the other polarizing plate 452 is arranged in the second inner case 422. These two inner cases 421 and 42
2 are stored and fixed in the outer case 410, and fixing plate fittings 461 and 462 made of stainless steel plate material or the like are fixed to the openings at both ends of the outer case 410.
All optical components to be stored in the inner case 421 are stored in advance.
and 422, and these inner cases are inserted and fixed into the outer case 410 to facilitate assembly and adjustment, and fixing plate fittings 461 and 462 are fixed to the openings at both ends of the outer case. This makes the optical components more firmly fixed.

(Fifth Embodiment) FIG. 9 is a longitudinal sectional view of an optical isolator according to a fifth embodiment of the present invention, and FIG. 10 is an assembled view of the fifth embodiment.

In this embodiment, one polarizing plate 551 and magnet 531 are housed and fixed in the first inner case 521, and the other polarizing plate 552 and magnet 532 are housed and fixed in the second inner case 522. These inner cases 521, 522 and the magneto-optical element 540 are housed and fixed in the outer case 510 so that the magneto-optical element 540 is sandwiched between the inner cases, and fixing plate metal fittings 561 are attached to the openings at both ends of the outer case.
and 562 are fixed to each other, and has almost the same advantages as the fourth embodiment.

(Sixth Embodiment) FIG. 11 is a longitudinal sectional view of an optical isolator according to a sixth embodiment of the present invention. In this embodiment, instead of using the inner case 521 and the fixed plate metal fittings 561 of the fifth embodiment, a bottomed cylindrical inner case 621 is used, and the inner case 52
2 and a fixing plate metal fitting 562, a bottomed cylindrical inner case 622 is used, which integrates these two together, thereby making it possible to reduce the number of assembly steps. Other points are the same as the fifth embodiment. In addition, Figure 1
1, numerals 651 and 652 are polarizing plates, and numeral 631
, 632 are magnets, symbols 621a, 631a, 632a,
622a is a light passage hole.

In each of the above embodiments, a permanent magnet is used as the magnetic field generating means, and the permanent magnet is installed inside the outer case. You can also do it.

[0033]

As described in detail above, the present invention is such that at least a polarizer and a magneto-optical element are housed in a cylindrical outer case with a common optical axis, and the polarizer, the magneto-optic element and the magnetic field By storing one or more of the forming means in an inner case and storing the inner case in the outer case, a compact optical isolator that has excellent reliability and is easy to assemble and adjust can be obtained. It is something that exists.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an optical isolator according to a first embodiment of the present invention.

FIG. 2 is an assembly diagram of the first embodiment.

FIG. 3 is a longitudinal sectional view of an optical isolator according to a second embodiment of the present invention.

FIG. 4 is an assembly diagram of the second embodiment.

FIG. 5 is a longitudinal sectional view of an optical isolator according to a third embodiment of the present invention.

FIG. 6 is an assembly diagram of the third embodiment.

FIG. 7 is a longitudinal sectional view of an optical isolator according to a fourth embodiment of the present invention.

FIG. 8 is an assembly diagram of the fourth embodiment.

FIG. 9 is a longitudinal sectional view of an optical isolator according to a fifth embodiment of the present invention.

FIG. 10 is an assembly diagram of the fifth embodiment.

FIG. 11 is a longitudinal sectional view of an optical isolator according to a fifth embodiment of the present invention.

[Explanation of symbols]

110, 210, 310, 410, 510, 610
Outer case 120, 221, 222, 320, 421, 422, 5
21,522,621,622
Inner case 151, 152, 251, 252, 351, 352, 4
51,452,551,552,651,652
Polarizing plate 131, 132, 133, 231, 232, 233, 3
31,332,333,334,431,432,53
1,532,631,632 Magnet 140,240,340,440,540,640
magneto-optical element

Claims (5)

[Claims] Claim 1: Two polarizers disposed with different transmission polarization planes and a common optical axis; a magneto-optical element disposed between these polarizers with a common optical axis; An optical isolator comprising a magnetic field forming means for forming a magnetic field in an optical element, wherein at least the polarizer and the magneto-optical element are housed in a cylindrical outer case with a common optical axis, and the two polarizers, An optical isolator characterized in that one or more of a magneto-optical element and a magnetic field forming means are housed in an inner case, and the inner case is housed in the outer case. 2. The optical isolator according to claim 1, wherein the cylindrical outer case has a hollow section in the cylinder having a circular cross-sectional shape, and the outer shape of the inner case is the same as the outer case. An optical isolator characterized in that it is cylindrical in shape and has an outer diameter approximately equal to the inner diameter of a cavity. 3. The optical isolator according to claim 2, wherein the two polarizers are housed in separate inner cases, and these inner cases are housed in the outer case. Isolator. 4. The optical isolator according to claim 1, wherein a permanent magnet is used as the magnetic field generating means, and the permanent magnet is housed in an outer case. 5. The optical isolator according to claim 4, wherein the permanent magnet is composed of a plurality of parts, and these permanent magnets are arranged in the outer case so as to surround the magneto-optical element. Isolator.