JPH02209708A - Electromagnet for magneto-optical switch - Google Patents

Abstract

PURPOSE:To obtain an electromagnet generating a high magnetic field between poles by a method wherein a core made of semi-hard magnetic material is placed in a plane containing light paths along which light enters and comes out of a composite optical component including a magneto-optical switching device and holes are drilled in the core, auxiliary pole plates and a magnetic plate for forming a closed magnetic path and coils are wound around the core on the parts apart from the light path. CONSTITUTION:Holes 4a-4c are drilled in a core 1 having a square cross section along single-dotted chain lines A-C which are the light paths of a laser beam. All the holes exist in a plane on which all the centers of the cross sections of the core 1 exist or in a plane which is in parallel with the former plane. Therefore, an electromagnet suitable for surface mounting can be constructed easily. Further, as a core frame can be so designed as to have coils 5 wound on two positions apart from the hole 4c, a high magnetic field can be obtained between poles.

Description

[Detailed Description of the Invention] [Summary] Regarding an electromagnet for a magneto-optic switch, the present invention relates to an electromagnet that supplies a sufficient magnetic field to a composite optical component (integrated optical component) including a magneto-optic switch element, such as a Faraday rotator, and has a low profile (electromagnet The purpose of the present invention is to provide an electromagnet with a thin thickness (as a thin film), and the center of the cross section of the magnetic core is in a plane containing the optical path of light entering and exiting the composite optical component (integrated optical component), or in a plane parallel thereto. A magnetic core made of a semi-hard magnetic material is placed so that all the components are placed on top of each other, and holes are made in the magnetic core in the optical path of the input and output light, the auxiliary magnetic pole plate, and the magnetic plate for forming a closed magnetic path. A magneto-optical switch electromagnet is constructed by winding the coil.

[Industrial application field]

The present invention relates to improvements in electromagnets for magneto-optic switches.

It is well known that laser light has come to be used for main power transmission lines, mainly undersea communication cables.

Furthermore, with improvements in optical fibers, laser light sources, optical data links, and other optical components, LAN (Local Array)
The introduction of optical technology such as EA Network has become popular, and information network systems based on optical fibers are now being used in new intelligent buildings.

These laser light application systems require optical switches, but mechanical optical switches have low reliability (they cannot be used in systems that require high reliability).

In contrast, magneto-optical switches that utilize Faraday rotation are solid-state switches with no moving parts, so they are suitable for optical communication system switches that require high reliability, such as optical fiber line switching switches, and are beginning to be put into practical use. .

[Conventional technology]

Generally, an optical device constitutes an optical system by combining individual optical parts such as a lens, a prism, a partial single-wavelength plate (λ/2 plate), and a beam splitter.

When introducing a magneto-optical switch into such an optical system,
By directly applying a magnetic field to the Faraday rotator to rotate the plane of polarization, a magneto-optical switch was constructed as an individual optical component, making it possible to apply a strong magnetic field and therefore simplifying the selection of electromagnets. Ta.

However, recently, in order to miniaturize the entire optical system and facilitate adjustment, composite optical components that integrate the various individual optical components described above have begun to be put into practical use.

Fig. 8 shows an example of such a conventional device [Japanese Patent Application No. 187708/1987 (filed on July 27, 1988) proposed by the present applicant], which has a total reflection mirror at one end. A composite optical component is used in which a magneto-optic switch element 6 and a λ/2 plate 7 are sandwiched and adhesively fixed between two polarizing beam splitters 8.

Therefore, as shown in the figure, it is necessary to widen the distance between the auxiliary magnetic pole plates 2 bonded to both ends of the C-shaped magnetic core 1 around which the coil 5 is wound. The strength of the magnetic field is smaller compared to .

As a result, in order to strengthen the magnetic field, the current flowing through the coil must be increased.

The figure shows an example of a 2x2 optical switch in which light travels in the direction of the arrow along the broken line, and there are two input ports and two output ports. Note that 9 in the figure is a lens.

Since a polarization beam splinter allows P-polarized light to pass through and reflects S-polarized light, for example, by applying an external magnetic field that rotates the plane of polarization by 45 degrees to the magneto-optic switch element 6 and reversing it, the light incident in the C direction can be polarized. direction A or C
It is possible to switch the output light from the light incident in the 'force direction' or the B direction to the C' force direction or the A direction.

As shown in the figure, one of the two auxiliary magnetic pole plates 2 has a hole 4 (a) through which the output laser beam (six directions) passes, and a hole 4 (b) through which the incident laser beam (direction B) passes. ) has been opened.

The other input/output laser beam (C and C') has a plane in which the force direction is perpendicular to the laser beam and includes the optical path of the input/output beams A, B, C, and C' [for example, FIG. (A) corresponds to the plane of the paper] is a plane on which the entire center of the cross section of the magnetic core l lies [for example, the -dotted chain line D in Fig. 8 (C)].
-D' and is assumed to be a plane perpendicular to the plane of the paper].

This is because the C-shaped magnetic core l around which the coil 5 is wound gets in the way, making it impossible to set the optical path within a plane on which the entire center of the cross section of the magnetic core 1 rests, or a parallel plane close to the plane.

[Problem to be solved by the invention]

Therefore, the height of the conventional magneto-optic switch described above is approximately the height of the composite optical component plus the height of the magnetic core.

In reality, the height of the magnetic core is often larger than the height of the composite optical component, so the dimensions, especially the height, of the conventional magneto-optic switch using electromagnets shown in FIG. 8 become large.

Recently, due to the need for planar mounting, there has been a strong demand for low-profile optical switches in which all optical paths are parallel to the mounting surface, and this has become a major problem.

Furthermore, since a magnetic field is applied to the entire composite optical component, the spacing between the magnetic poles becomes wide (which results in a large current being passed through the coil 5 in conventional electromagnets, which causes heat generation and other problems. A solution was needed.

[Means to solve the problem]

Figure 1 is a perspective view (A) showing an example of the configuration of the electromagnet of the present invention.
and a layout diagram (b) of a composite optical component (integrated optical component).

The composite optical component shown here is similar to 2 in Fig. 5, which was already explained.
Taking the x2 optical switch as an example, the arrangement of the electromagnet of the present invention between the magnetic poles, the optical path and holes 4 (a) and 4 (b).

4(c) and the like are shown to make the present invention easier to understand.

The prismatic core 1 has holes 4 (a) and 4 (b).

4(c) is the optical path of the laser light beam, dotted lines A and B
, C, all of which lie within a plane on which the center of the cross section of the magnetic core 1 lies, or a plane parallel thereto.

Therefore, it is easy to configure an electromagnet suitable for planar mounting.

Furthermore, since the magnetic core frame can be designed so that the coil 5 is wound in two places avoiding the hole 4(c), a large magnetic field can be obtained between the magnetic poles.

In other words, the above problem is solved by creating a semi-rigid structure so that the center of the magnetic core cross section is entirely on the plane containing the optical path of the light entering and exiting the composite optical component (integrated optical component) including the magneto-optical switch element, or in a plane parallel to the plane. A magnetic core made of a magnetic material is arranged, holes are made in the magnetic core in the optical path of the input and output light, an auxiliary magnetic pole plate, and a magnetic plate for forming a closed magnetic path, and a coil is wound around the magnetic core avoiding the optical path. This problem can be solved by configuring an electromagnet for a magneto-optic switch.

[Effect]

As shown in FIG. 1, there are holes 4 (a), 4 (b), 4 through which all the laser beams of the magneto-optic switch pass.
(C) is opened along dashed lines A, B, and C in a plane on which all the centers of the cross sections of the magnetic core 1 are placed, or in a plane parallel to the plane, so the height of the optical switch device is approximately the same as that of the magnetic core 1. The thickness of the magnet is determined by the thickness of the magnet, and therefore a low-profile electromagnet can be easily obtained.

Further, since the coil 5 can be wound many times over each frame side of the magnetic core 1 while avoiding the hole 4(C), it is possible to sufficiently increase the magnetic field generated between the magnetic poles.

[Example] FIG. 2 is a diagram showing an example of the present invention using a cylindrical magnetic core.

In the figure, 1 is a cylindrical magnetic core made of iron-copper-molybdenum magnetic alloy (Fe-Cu-Mo, trade name: TFC) with a diameter of 2 mm and a length of 30 mm, and the four cores are on the same plane as shown in the figure. They were arranged in two columns and two rows with an interval between them. 0.1 for magnetic core 1
The coil 5 was formed by tightly winding each 3 mmφ copper wire with 500 turns.

2 is a piece of iron with a thickness Q of 3 mm, a width of 3 mm, and a length of 12 mm.
Cobalt-niobium magnetic alloy (Fe-Co-Nb,
Product name: Nipkoroi NB50) magnetic core 1 with auxiliary magnetic pole plate
It was glued to the end with epoxy resin.

3 is a permalloy (Ni-Fe) magnetic plate with a thickness of 0.8 mm, a width of 35 mm, and a length of 85 mm, with both ends bent at right angles and placed between the ends of the magnetic core 1 on the side to which the auxiliary magnetic pole plate 2 is not bonded. This is provided to form a closed magnetic path by connecting the auxiliary magnetic pole plates 2 and to strengthen the magnetic field generated between the auxiliary magnetic pole plates 2. Note that the interval between the auxiliary magnetic pole plates 2 was 3 mm.

A hole 4(a) with a diameter of 1 mm is provided along the optical path (A) at one bent end of one of the auxiliary magnetic pole plates 2 and the magnetic plate 3.
In addition, at the other bent end of the other auxiliary magnetic pole plate 2 and the magnetic plate 3, a hole 4 with a diameter of 1 mm is formed along the optical path (B) with a center distance of 1.5 mm from the hole 4 (a). (b) was opened.

In this way, the plane on which all the centers of the cross-sections of the magnetic core 1 are placed can be made to coincide with the optical paths A, B, and C, and as a result, the height of the magneto-optic switch can be reduced to 1Q mm or less.

The arrangement of the composite optical component between the magnetic poles is the same as that shown in FIG. 1 (b).

FIG. 3 shows a magnetic field strength versus current curve diagram (■) of the above embodiment using a cylindrical magnetic core.

The magnetic field strength at the center between the auxiliary pole plates 2 at a coil current of 1 ampere is 350 Oe, and the residual magnetic field HO2
A squareness ratio of 76% was obtained with 650e.

This value is more than twice as large as the magnetic field strength of 150 oersted under similar conditions in the conventional example shown in Figure 8, and the height when configured as an electromagnet for flat mounting is I was able to reduce it by half or less.

FIG. 4 is a diagram showing another embodiment of the present invention using a cylindrical magnetic core.

In the embodiment shown in FIG. 2, since the two magnetic cores 1 with the same polarity are connected by one magnetic plate 3, the density of the magnetic lines of force tends to decrease in the intermediate region due to the anti-t9 magnetic field. Further, since the distance between the auxiliary magnetic pole plate 2 and the magnetic Fi, 3 is short, the magnetic flux emitted from the auxiliary magnetic pole plate 2 tends to leak to the magnetic plate 3.

Therefore, this embodiment shows a configuration for improving this.

In this example, the four magnetic cores, coils, auxiliary magnetic pole plates, etc. are the same as the example shown in FIG. 3゛ and
By providing a spacing of 4 to 7 mm, and by interposing a spacer 10 between the coil wound around the magnetic core 1 and the magnetic plates 3, 3' as shown in (b) of the same figure, the spacing is 0.5 to 7 mm. 1.0
The spacing is mm.

Then, in order to fix the two sets of electromagnets, a magnetic plate 3.3
A holding plate 11 was provided on top of the ``.

Therefore, in order to insert the optical fiber between the magnetic plates 3 and 3, a minimum distance of 4 mm is required, and the distance must be 7 m.
If it is more than m, the magnetic flux distribution between the auxiliary magnetic pole plates 2 will deteriorate.

Furthermore, if the thickness of the spacer 10 is 0.5 mm or less, magnetic flux leakage will occur as in the configuration shown in FIG.
The above is not necessary from the point of view of miniaturization.

FIG. 5 is a magnetic field strength vs. current curve diagram (■) of an example using nibcolloy auxiliary magnetic pole plates in the above configuration, where the auxiliary magnetic pole plate spacing is 4 mm and the auxiliary magnetic pole plate thickness is 0.3 mm.

Note that the dotted curve ■ is the same as the configuration shown in Figure 2, and shows for comparison the characteristics when only the auxiliary pole plate spacing is 4 mm, which is 1 mm wider than in Figure 2 (
Therefore, the residual magnetic field value is 130e compared to 2650e in Figure 3.
0e).

The solid curve ■ indicates the spacer 10. With the excitation characteristics of this example in which the holding plate 11 is provided, the generated magnetic field is 4300e and the residual magnetic field is 2200e at the coil current IA, and compared with the data of (2), this example in which the spacer is 10° and the holding plate 11 is provided. We were able to confirm the effectiveness of

In the above embodiment, the auxiliary magnetic pole plate 2 is made of iron-cobalt-niobium magnetic alloy (F), which is a semi-hard magnetic material.
e-Co-N b, product name: Nifco Loy NB50)
However, in this case, if the plate thickness is thin, there is a tendency that sufficient saturation cannot be achieved due to shape anisotropy.

Therefore, as the auxiliary magnetic pole plate 2, an electromagnet was fabricated using a Mn-Zn ferrite sintered body having good magnetic saturation characteristics even when made into a flat plate, and having the configuration shown in FIG.

The physical properties of this ferrite are an initial magnetic permeability of 2300. Effective saturation magnetic flux density 4400 gauss, effective saturation coercive force 0.20e
It is.

Figure 6 is a magnetic field strength vs. current curve diagram of an example using a ferrite auxiliary magnetic pole plate, and ■ indicates that the thickness of the auxiliary magnetic pole plate 2 is 0.5 m.
In the case of m, ■ is the case of 1.0 mm. Note that the interval between the auxiliary magnetic pole plates 2 is 3 mm. As can be seen from the figure, the residual magnetic field was 2600e in the case of ■ with a plate thickness of 0.5 mm, but the residual magnetic field was 2600e when the plate thickness was 1. In the case of Omm ■, the residual magnetic field is 30
The largest value of 00e was obtained, and it was found to be extremely excellent as an electromagnet for magneto-optical switches.

Of course, the ferrite auxiliary magnetic pole plate described above can also be effectively used as an auxiliary magnetic pole plate of other configurations of the present invention.

On the other hand, FIG. 7 is a diagram showing still another embodiment of the present invention using a flat magnetic core.

In this example, since a thin flat plate made of semi-hard magnetic material is used for the magnetic core l, two holes, 4 (a) and 4 (b), are sufficient as shown in the figure. In the direction along the optical path C, a composite optical component including a magneto-optical switch element can be arranged without being obstructed by the coil 5 wound flat around the magnetic core 1, so that a low-profile electromagnet suitable for planar mounting can be produced. is extremely easy.

In addition, since a symmetrical magnetic core frame is used as shown in the figure, the coil 5 is placed on the opposite magnetic core frame side with the magnetic pole part in between, that is, the 2
The auxiliary magnetic pole plates 2 are wound around each other, and a large magnetic field can be obtained between the auxiliary magnetic pole plates 2.

[Effects of the Invention] As explained above, by carrying out the present invention, it is possible to manufacture an electromagnet that has a low profile suitable for planar mounting and generates a large magnetic field between magnetic poles, and improves the performance of a magneto-optical switch. It greatly contributes to improvement.

[Brief explanation of the drawing]

Figure 1 is a perspective view (A) showing an example of the configuration of the electromagnet of the present invention.
2 is a diagram showing an embodiment of the present invention using a cylindrical magnetic core, and FIG. 3 is a magnetic field strength vs. current curve diagram of an embodiment using a cylindrical magnetic core. , Fig. 4 is a diagram showing another embodiment of the present invention using a cylindrical magnetic core, Fig. 5 is a magnetic field strength vs. current curve diagram of an embodiment using a Nipkolloy auxiliary magnetic pole plate, and Fig. 6 is a diagram showing a ferrite auxiliary magnetic pole plate. A magnetic field strength vs. current curve diagram of an embodiment using a magnetic pole plate, FIG. 7 is a diagram showing still another embodiment of the present invention using a flat magnetic core, and FIG. 8 is a conventional example of an electromagnet for a magneto-optic switch. FIG. In the figure, 1 is a magnetic core, 2 is an auxiliary magnetic pole plate, 3.3 is a magnetic plate forming a closed magnetic path, 4 (a), 4 (b), 4 (c) are holes, 5 is a coil, and 6 is a magnetic plate. 7 is a 1/2 wavelength plate, 8 is a polarizing beam splitter, 9 is a lens, IO is a spacer, and 11 is a holding plate. 4 rows of stone travel circles with 8 uses for yen akin stone spiders
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Claims (5)

[Claims] (1) In an electromagnet for applying a magnetic field to a composite optical component (integrated optical component) including a magneto-optical switch element, a plane including the optical path of light entering and exiting the composite optical component (integrated optical component), or A magnetic core made of a semi-hard magnetic material (
1), a magnetic core (1) in the optical path of the input and output light, an auxiliary magnetic pole plate (2), and a magnetic plate (3) for forming a closed magnetic path.
Drill a hole (4) in the hole (4) and insert the coil (1) into the magnetic core (1) avoiding the optical path.
5) An electromagnet for a magneto-optical switch characterized by being wound with. (2) The magnetic core (1) has a prismatic column/square frame shape, and holes 4 (a), 4 (b), 4 (c) forming optical paths are formed on the side where the magnetic pole part is located and the side facing it. An electromagnet for a magneto-optical switch according to claim 1, characterized in that: (3) Four cylindrical magnetic cores (1) are arranged at intervals in two columns and two rows, and two auxiliary magnetic pole plates (2) are placed at the end of the central magnetic core.
A magnetic plate (3) for forming a closed magnetic path is used to bridge between the ends of the magnetic core on the opposite side, and one of the magnetic plates (3) for forming a closed magnetic path with an auxiliary magnetic pole plate (2) is bonded. 2. The electromagnet for a magneto-optical switch according to claim 1, wherein one set has a hole 4(a) that serves as an optical path, and the other set has a hole 4(b) that serves as an optical path. (4) Four cylindrical magnetic cores (1) are arranged at intervals in two columns and two rows, and two auxiliary magnetic pole plates (2) are placed at the end of the central magnetic core.
and bridged with two sets of magnetic plates (3) and (3') to form a closed magnetic path between the opposite ends of the magnetic core, and the two sets of magnetic plates (3) and (3') ), spacer (
10), the two sets of magnetic plates (3) and (3') arranged in parallel are maintained at a required distance from the coil (5) wound around the magnetic core (1). , fixed to the holding plate (11) with the required spacing maintained, and a hole 4(a) serving as an optical path is formed in one side of the auxiliary magnetic pole plate (2), and a hole 4(b) serving as an optical path is made in the other side. An electromagnet for magneto-optical switches characterized by: (5) The magnetic core (1) has a flat plate shape and a rectangular frame type, and the square frame has two flat protrusions that serve as magnetic poles in the center, and auxiliary magnetic pole plates ( 2), and make holes 4(a) and 4(b) that will serve as the optical path in the protruding parts of the two auxiliary magnetic pole plates (2), and then
2. The electromagnet for a magneto-optical switch according to claim 1, wherein the coil (5) is wound around the two magnetic core frame sides avoiding the optical path.