JP2529483Y2 - Optical isolator - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component used for an optical communication system or an optical measuring instrument, for example, for preventing light emitted from a light source from being reflected at an end face of the optical system and returning to the light source. It relates to an optical isolator.

[0002]

2. Description of the Related Art When light from a light source is transmitted through an optical system, light reflected at an end face of the optical system returns to the light source. For example, in signal transmission using an optical fiber, light emitted from a laser light source is projected onto a fiber end face through a lens, and most of the light enters the fiber as transmission light, but is reflected on the surface of the lens or fiber end face. After returning to the laser light source, the surface is reflected again at the end face, resulting in noise. An optical isolator is used to eliminate such noise. The optical isolator is required to have high performance in extinguishing reflected light returning to the light source, that is, high extinction performance, and low loss of light transmittance, that is, low insertion loss.

FIG. 5 is a sectional view of an optical isolator. In FIG. 1, a polarizer 1, an Faraday rotator 3, and an analyzer 2 as optical elements are arranged in this order, and metal members 5, 6 as holding jigs and a magnet 4 for applying a magnetic field to the Faraday rotator 3 are shown.
And is stored in the outer cylinder 7. In the optical isolator shown in the figure, the boundary between the components is joined by solder, for example, as indicated by a, but is often joined by an adhesive.

When the components of the optical isolator are joined by soldering, a thin metal film must be formed on the side surface of the optical element so that the components can be soldered. Forming the metal thin film is complicated, and the optical surface of the optical element becomes dirty, and the insertion loss of the optical isolator increases.

When an optical isolator is bonded with an adhesive,
Solder glass is often used as an adhesive, but the temperature must be raised to melt the solder glass. Since each component of the optical isolator has a different thermal expansion coefficient, non-uniform mechanical distortion occurs in the optical element due to shrinkage when the solder glass solidifies. When mechanical distortion occurs, the optical axis is shifted and the insertion loss of the optical isolator increases, or birefringence occurs in the Faraday rotator, and the extinction performance of the optical isolator decreases.

[0006]

As a measure to avoid the mechanical distortion caused when the adhesive solidifies, Japanese Patent Application Laid-Open No. 2-245720 discloses a method in which an optical element is pressed and fixed inside a pipe with a coil spring or an O-ring. A method for doing so is disclosed. However, if the coil spring or the O-ring is pressed for a long time, it is gradually deformed and the position of the optical element is shifted.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an optical isolator having high extinction performance and low insertion loss, and which can easily assemble and join components. I do.

[0008]

An optical isolator according to the present invention, which has been made to achieve the above object, will be described with reference to FIG. 1 corresponding to an embodiment.

In FIG. 1, in an optical isolator 10 including a polarizer 1, a Faraday rotator 3, an analyzer 2, and a cylindrical magnet 4 for applying a magnetic field to the Faraday rotator 3,
Are arranged inside the metal member 5, and the metal members 11 and 1
It is sandwiched between 2 and fixed. Metal members 5, 11, 12
And the gap between the polarizers 1 is filled with an adhesive. The analyzer 2 is arranged inside the metal member 6 and is fixed between the metal members 15 and 16. Metal members 6, 15, 1
The gap between 6 and the analyzer 2 is filled with an adhesive. The Faraday rotator 3 is arranged inside the cylindrical magnet 4 and is fixed by being sandwiched between two metal members 13 and 14. Cylindrical magnet 4, metal members 13 and 14, and Faraday rotator 3
Are filled with an adhesive.

In the optical isolator shown in FIG. 1, the polarizer 1 (or the analyzer 2) is connected to the metal members 11 and 12 (or the metal members 15 and 16) inside the cylindrical metal member 5 (or the metal member 6). Although it is sandwiched and fixed, the polarizer 1 and the analyzer 2 may be fixed by a metal member formed integrally.

The metal member is coated with an adhesive at a boundary portion with another part, and after assembling the part, the adhesive is melted to fill the gap with the adhesive. As shown in FIG. 1, a hole 20 for inserting an adhesive is provided in the metal member 5, the metal member 6, and the cylindrical magnet 4, and the adhesive is arranged in the hole 20 to facilitate the work. When it is not desired to make the hole 20 in the cylindrical magnet 4, for example, metal members 11, 12, 13, 14, 15,
A hole 20 may be provided in 16.

As the adhesive, for example, solder glass, epoxy-based adhesive, silicone-based adhesive, epoxy-modified silicone-based adhesive can be used.

[0013]

When a solder glass is used as an adhesive, the optical element is fixed by being sandwiched between metal members. Since the optical element having a different coefficient of thermal expansion and the metal member are not directly connected by the solder glass, the solder glass cannot be used. Non-uniform mechanical strain due to shrinkage does not occur during solidification. By filling the gap between the components with the solder glass, the structure of the optical isolator becomes stable, and the position of the optical element does not shift even after a long time, so that the characteristics of the optical isolator do not deteriorate.

When another adhesive is used, the gap between the components is filled with the adhesive, so that the optical isolator is shock-absorbing even after the adhesive is solidified, and the structure is stable.

[0015]

Embodiments of the present invention will be described below.

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

The optical isolator 10 shown in FIG. 1 includes a polarizer 1, a Faraday rotator 3, an analyzer 2, a cylindrical magnet 4 for applying a magnetic field to the Faraday rotator 3, and metal members 5, 6, 11,
12, 13, 14, 15, and 16 are arranged in the assembled outer cylinder 7, and the gaps between the parts are filled with an adhesive to be integrally formed. Holes 20 provided in metal member 5, metal member 6, and cylindrical magnet 4 are holes into which an adhesive is inserted.

The polarizer 1 has a glass polarizing plate formed on the inner peripheral surface of the metal member 5, and the analyzer 2 has a glass polarizing plate formed in a cylindrical shape having an outer diameter that fits on the inner peripheral surface of the metal member 6. Faraday rotator 3
Forms a bismuth-substituted rare earth iron garnet crystal into a cylindrical shape that fits in the cylindrical magnet 4. Metal members 5, 6, 11, 1
2, 13, 14, 15, 16 are all made of stainless steel and brass. The metal member 5 (or the metal member 6) has the same outer diameter as the cylindrical magnet 4, and has a width equal to the sum of the widths of the polarizer 1 (or the analyzer 2) and the metal members 11, 12 (or the metal members 15, 16). Form equally. The width of the cylindrical magnet 4 is equal to the sum of the widths of the Faraday rotator 3 and the metal members 13 and 14. The width of the outer cylinder 7 is formed to be equal to the sum of the widths of the metal member 5, the cylindrical magnet 4, and the metal member 6.

Metal member 5, metal member 6, and cylindrical magnet 4
Are provided with four holes 20 at positions symmetrical in the radial direction at both left and right ends, respectively, in a direction perpendicular to the optical axis. An adhesive is inserted into each of the holes 20.

The polarizer 1 (or analyzer 2) is a metal member 5
(Or the metal member 6), and sandwiched and fixed between the metal members 11, 12 (or the metal members 15, 16) from both sides. The Faraday rotator 3 is disposed inside the cylindrical magnet 4 and is fixed by being sandwiched between metal members 13 and 14 from both sides. Next, the adhesive inserted into each of the holes 20 is melted, and the gaps between the metal members 5, 11, 12 and the polarizer 1, and the gaps between the metal members 6, 15, 16 and the analyzer 2 are melted with the adhesive. fill in. Also, the gap between the cylindrical magnet 4, the metal members 13, 14 and the Faraday rotator 3 is filled with the adhesive.

The above components are arranged inside the outer cylinder 7 in the order shown in FIG. 1, and the outer cylinder 7 and the metal member 11, and the outer cylinder 7 and the metal member 16 are fixed by bonding with an adhesive. 1
0 is completed.

The metal member for fixing the polarizer 1 and the analyzer 2 may be formed as shown in FIGS. Polarizer 1
However, the same applies to the case of the analyzer 2. FIG. 2 shows a case where the polarizer 1 is tilted, the polarizer 1 is arranged inside the metal member 5, and the polarizer 1 is sandwiched and fixed between the metal members 11 and 12 formed with an inclination. FIG. 3 shows that the metal member 5 is integrally formed, and the polarizer 1 is fixed inside the metal member 5. In FIG. 4, one side of the metal member 5 is opened, and the polarizer 1 is disposed inside the metal member 5 and fixed with the metal member 11.

[0023]

As described in detail above, the optical isolator of the present invention does not shift because the optical element is fixed by the metal member. Since the optical element is fixed to another component having a different coefficient of thermal expansion without being bonded with an adhesive, no distortion occurs and the characteristics of the optical isolator do not deteriorate. Further, it is not necessary to form a metal thin film on the optical element for soldering, so that the manufacturing is simple.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing that an inclined optical element is fixed by a metal member.

FIG. 3 is a sectional view showing that the optical element is fixed by a metal member formed integrally.

FIG. 4 is a sectional view showing that the optical element is fixed by two metal members.

FIG. 5 is a sectional view of a conventional optical isolator.

[Explanation of symbols]

1 is a polarizer, 2 is an analyzer, 3 is a Faraday rotator, 4 is a cylindrical magnet, 5 and 6 are metal members, 7 is an outer cylinder, 10 is an optical isolator, 11, 12, 13, 14, 15, 16 and The metal member 20 is a hole.

Claims (2)

(57) [Scope of request for utility model registration] 1. An optical isolator comprising a polarizer, a Faraday rotator, an analyzer, and a magnet for applying a magnetic field to the Faraday rotator, wherein the polarizer and the analyzer are fixed by at least one metal member, respectively. The gap between the polarizer and the gap between the metal member and the analyzer is filled with an adhesive,
An optical isolator characterized in that a Faraday rotator is disposed inside a magnet, fixed between two metal members, and a gap between the magnet, the metal member, and the Faraday rotator is filled with an adhesive. 2. The optical isolator according to claim 1, wherein a hole for inserting an adhesive into the metal member or the metal member and the magnet is provided.