JPH0588113A - Optical fiber type faraday rotor and optical isolator - Google Patents

Abstract

PURPOSE:To provide the optical fiber type rotator which can easily be manufactured compactly to extremely small size and the optical isolator which uses the optical fiber type Faraday rotator. CONSTITUTION:The optical fiber type Faraday rotator is formed by putting an optical fiber 130 which provides Faraday effect in an annular magnet body 110, formed in a closed polygonal annular shape by coupling unit magnet members 101-108 having both end surfaces slanted in mutually opposite directions at a specific angle with magnetic poles at both end parts so that the end surfaces abut on each other, along the center axis of the annular magnet body 100; and the optical isolator uses the Faraday rotator of said constitution. Consequently, the optical fiber rotator and optical isolator which can easily be manufactured compactly to the extremely small size are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type Faraday rotator which can be made extremely small and compact, and an optical isolator using the optical fiber type Faraday rotator.

[0002]

2. Description of the Related Art As an optical fiber type Faraday rotator, for example, reference [APPLIED OPTICS Vol.23, No.7 A
pril 1984 pp1103-1106] are known.

In short, the example disclosed in this document is to apply a magnetic field along the axial direction to an optical fiber whose core material is made of a substance exhibiting the Faraday effect. The polarization plane of the polarized light traveling inside is rotated.

Further, as an example in which the principle disclosed in this document is applied, a generally known example is to wind an optical fiber around the center of a donut-shaped solenoid coil so that a magnetic field is generated parallel to the axis of the optical fiber. As an example of such an arrangement or an improvement thereof, an example is known in which an optical fiber is wound in a shape that vertically intersects with an 8-shaped solenoid coil (as of August 8, 1984). See Nikkan Kogyo Shimbun).

Further, there is also known an optical isolator in which polarizers having different polarization planes are arranged at the entrance and exit portions of the above-mentioned optical fiber type Faraday rotator.

[0006]

By the way, since the above-mentioned conventional optical fiber type Faraday rotator uses a solenoid coil, there is a problem of heat generation by the solenoid coil and the solenoid coil is driven. A power source that can be used was required, and there was a certain limit to miniaturization and compactness. Further, in the case where the above-mentioned donut type solenoid coil is used, the solenoid coil must be formed in a donut type, and a complicated assembling work of twisting and winding the optical fiber around the center of the ring is required. It had a problem that

The present invention has been made under the above-mentioned background, and is an optical fiber type Faraday rotator which can be formed into an extremely small size and is extremely easy to manufacture and an optical fiber using the optical fiber type Faraday rotator. It is intended to provide an isolator.

[0008]

In order to solve the above-mentioned problems, the present invention provides (1) both end faces intersecting with the central axis of a cylindrical magnet member having magnetic poles at both ends with respect to a surface orthogonal to the central axis. Inside a ring-shaped magnet body formed by forming a closed polygonal ring by uniting a plurality of unit magnet members that are inclined by a predetermined angle in mutually opposite directions by abutting their end faces. An optical fiber having the Faraday effect is housed along the central axis.

Further, as an optical isolator using the optical fiber type Faraday rotator of the constitution 1, (2) an optical isolator comprising polarizers having different polarization planes on both sides of the Faraday rotator, wherein the Faraday rotator is used. The optical fiber type Faraday rotator described in 1 is used.

[0010]

According to the above-mentioned structure 1, since the magnetic field parallel to the axial direction is formed inside the annular magnet body, the magnetic field is accommodated inside the annular magnet body along the axial direction to the axis of the optical fiber exhibiting the Faraday effect. A parallel magnetic field is applied along. Thereby, the function as a Faraday rotator can be obtained.
According to this, since it is not necessary to use the solenoid coil, the problem of heat generation by the solenoid coil does not occur, and the device can be made compact and compact. Further, the unit magnet members are arranged such that they are arranged on the circumference and are formed into a closed polygonal ring shape by forming a ring-shaped magnet body by abutting the end faces of each other and joining them together. Therefore, it is easy to manufacture the annular magnet member, and it is possible to form the annular magnet body by passing the optical fiber through each unit magnet member in advance, and at the same time, it is possible to obtain the optical fiber type Faraday rotator. Is extremely easy.

Further, according to the configuration 2, an optical isolator using an optical fiber type Faraday rotator can be formed in an extremely small size and can be easily obtained.

[0012]

【Example】

(Optical Fiber Type Faraday Rotator) FIG. 1 is a diagram showing a configuration of an optical fiber type Faraday rotator according to an embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a unit magnet member, and FIG. 3 is an optical fiber type Faraday rotator. It is explanatory drawing of a manufacturing procedure. Hereinafter, an optical fiber type Faraday rotator according to an embodiment will be described in detail with reference to these drawings.

In the figure, reference numeral 100 is an annular magnet body, reference numerals 101 to 108 are unit magnet members, and reference numeral 130 is an optical fiber.

The ring-shaped magnet body 100 is formed by forming a closed polygonal ring by joining a plurality of substantially cylindrical unit magnet members 101 to 108 with their end faces abutted to each other. .. Therefore, a cavity 120 formed into a substantially donut shape by connecting the cavities in each of the unit magnet members 101 to 108 is formed therein, and a magnetic field parallel to the central axis of the cavity 120 is formed in the cavity 120. Has been formed.

The unit magnet members 101 to 108 have the same shape. As shown in the example of the unit magnet member 101 in FIG. 2, the unit magnet members 101 to 108 have N and S magnetic poles at both ends and have a substantially cylindrical shape. And both end surfaces 1 intersecting the central axis O of the magnet member 101.
01a101b is inclined with respect to the planes P ₁ and P ₂ orthogonal to the central axis O by an angle α = 22.5 ° in mutually opposite directions. A cavity 101c is formed inside. Further, the unit magnet members 101 and 108 are provided with optical fiber take-out holes 101d and 108d, respectively. These unit magnet members are composed of Sm—Co magnets or the like.

Then, the cavity 120 of the annular magnet member 100.
The optical fiber 130 is wound inside so that the optical axis of the optical fiber 130 is along the central axis of the cavity 120 so as to make six rounds in the cavity, and both ends thereof are taken out to the outside. It is used as an input / output section. In this embodiment, as the optical fiber 130, a single mode fiber made of lead glass is used. This fiber is diamagnetic, has a Verdet constant that is about five times that of quartz fiber, and has a small photoelastic constant that causes small bending-induced birefringence.
It is most suitable for use in the case of this embodiment in which it is wound in a small diameter. Note that such an optical fiber is, for example, Japanese Patent Publication No.
-13177, etc.

Next, with reference to FIG. 3, a procedure for manufacturing the optical fiber type Faraday rotator having the above-mentioned structure will be described.

First, the unit magnet members 101 to 108 are joined together by abutting the end faces having opposite magnetic poles to each other to form a long straight cylindrical body.

Next, the optical fiber 130 is passed through the inside of the cylinder from one end of this straight cylindrical body, and after passing through the inside of the cylinder,
After passing through the outside again into the cylinder a necessary number of times (6 times in this embodiment) to form a loop with a desired turn between the inside and outside of the cylinder, both ends are taken out from the loop. ..

Next, as shown by the arrow r in the figure, the unit magnet members 101 to 108 are successively rotated to form the annular magnet body 100 as shown in FIG. that time,
As shown by the arrow u, the work is performed while adjusting the loop diameter while pulling both ends of the optical fiber 130.

In the above structure, the coil diameter of the optical fiber 130 formed into a coil shape by passing through the cavity 120 in the annular magnet body 6 six times is set to about 30 mm, and the magnetic field in the cavity 120 is set. When the strength of was 3300 oersted (Oe), it was possible to obtain a Faraday rotation angle of 45 ° with respect to light having a wavelength of 1.3 μm. In this case, other wavelengths (1.5 μm, 0.8 μm, 0.63 μm) can be obtained by adjusting the total length of the optical fiber in the magnetic field and the strength of the magnetic field in consideration of the wavelength dependence of the Verdet constant.
Of course, it can also be applied to other wavelengths.

According to this embodiment, since it is not necessary to use the solenoid coil which has been conventionally required, the problem of heat generation by the solenoid coil does not occur, and the device can be made compact and compact. Further, the unit magnet member 101
Since the annular magnet body 100 is formed by abutting the end faces of each other with each other to be joined to each other, the annular magnet body 100 is easily manufactured, and each of the unit magnet members 101 to 108 is previously formed. Since the annular magnet body 100 can be formed by connecting them after passing the optical fiber 130, and at the same time, an optical fiber type Faraday rotator can be obtained, which is extremely easy to manufacture.

FIG. 4 is a diagram showing the configuration of a modification of the optical fiber type Faraday rotator according to the above-mentioned embodiment. As shown in the drawing, in this embodiment, an annular magnet body 200 is configured by 16 unit magnet members 201 to 216, and the other configurations are the same as the above-described one embodiment. The description is omitted. In addition, in this modification, in the unit magnet members 201 to 216, an angle α formed between both end surfaces of the unit magnet members 201 to 216 with respect to a surface orthogonal to the central axis
It is necessary to set α = 11.25 °.

According to this modification, since the shape of the ring-shaped magnet body 200 becomes closer to the ring shape, the optical fibers in the ring-shaped magnet body 200 can be arranged more accurately and parallel to the magnetic field. Therefore, it becomes possible to apply a magnetic field more efficiently.

(One Embodiment of Optical Isolator) FIG. 5 is a diagram showing the structure of an optical isolator according to one embodiment of the present invention.

In the optical isolator according to this embodiment, the fiber type polarizer 30 is provided at each of the light input / output ends of the optical fiber type Faraday rotator according to the above-mentioned modification.
0 and 400 are connected.

In this case, the optical fiber Faraday rotator 200 rotates the polarization plane of the incident polarized light by 45 °. In addition, the fiber type polarizers 300 and 40
0 indicates that the polarization planes of polarized lights that can pass through each other are deviated by 45 °.

As the fiber type polarizer, one using a polarization maintaining fiber is known. This polarization-maintaining fiber has the property that when the fiber is bent uniformly, the loss of one polarization component of the orthogonal polarization components of the light propagating through the fiber increases and only the other propagates. I have. Therefore, if this polarization-maintaining fiber is held in a circular shape by being held by, for example, a circular guide member, a function as a polarizer can be obtained and an optical fiber polarizer can be obtained.

According to this example, it was confirmed that isolation of about 25 dB or more can be easily obtained with respect to light having a wavelength of 1.3 μm.

According to this, it is possible to obtain an optical isolator whose optical path is composed entirely of optical fibers, which has an extremely simple and compact structure, and which requires almost no optical position adjustment. Obtainable.

Instead of the optical fiber polarizer, it is possible to have another polarizer such as an ultra-thin glass polarizer utilizing the resonance absorption of metal copper.

In each of the above-described embodiments, a single-mode fiber using lead glass is used as the optical fiber, but it goes without saying that a quartz fiber may be used instead. Quartz fiber has the advantage that it can be easily connected to a silica-based optical fiber that is widely used in optical communication and fiber sensors.

[0033]

As described above in detail, in the optical fiber type Faraday rotator according to the present invention, both end faces intersecting with the central axis of the cylindrical magnet member having magnetic poles at both ends with respect to the surface orthogonal to the central axis. Unit magnet members inclined by a predetermined angle in mutually opposite directions are joined together by abutting their end faces to form a closed polygonal ring shape by the inside of the annular magnet body. An optical fiber that exhibits a Faraday effect along the central axis is housed, and the optical isolator according to the present invention uses the Faraday rotator having the above-mentioned configuration, which can be formed to be extremely small and compact. , An optical fiber type Faraday rotator and an optical isolator that are extremely easy to manufacture are obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical fiber type Faraday rotator according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a unit magnet member.

FIG. 3 is an explanatory diagram of a manufacturing procedure of an optical fiber type Faraday rotator.

FIG. 4 is a diagram showing a modified example configuration of an optical fiber type Faraday rotator.

FIG. 5 is a diagram showing a configuration of an embodiment of an optical isolator.

[Explanation of symbols]

100, 200 ... Annular magnet body 101-108, 201
˜216 ... Unit magnet member, 130 ... Optical fiber, 30
0,400 ... Optical fiber polarizer.

Claims (2)

[Claims] 1. A unit magnet member in which both end surfaces of a cylindrical magnet member having magnetic poles at both ends intersecting with the central axis are inclined at predetermined angles in directions opposite to each other with respect to a surface orthogonal to the central axis. An optical fiber containing an optical fiber exhibiting the Faraday effect along the central axis of an annular magnet body formed so as to be formed into a polygonal ring closed by butt-joining a plurality of end faces and joining them. Type Faraday rotator. 2. An optical isolator in which polarizers having different polarization planes are arranged on both sides of a Faraday rotator, wherein the optical fiber type Faraday rotator according to claim 1 is used as the Faraday rotator. ..