JPH0596830U - Optical isolator - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an optical isolator capable of transmitting an effective beam having a diameter as designed without requiring assembly time such as position adjustment. [Structure] A holder ring 7 for holding a polarizer 1, a Faraday rotator 2 in a tubular magnet 5 and an analyzer 3 in place.
.Light-shielding plate 1 having an opening smaller than the inner diameter of 8 and 9
It is an optical isolator in which 0 is arranged in front of the polarizer 1. Since the aperture of the light shield plate 10 forms the aperture of the effective beam and the inner diameter of the holder ring 7/8/9 does not form the aperture of the effective beam, the holder ring 7/8/9
Even if the holes are assembled so as to be displaced from each other, some of the transmitted light rays are not blocked, and the effective beam diameter that can be transmitted by the optical isolator is as designed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical component used in, for example, an optical communication system or an optical measuring instrument, and relates to an optical isolator for preventing light emitted from a light source from being reflected by an end face of the optical system and returning to the light source. is there.

[0002]

[Prior Art]

 When the light from the light source is transmitted through the optical system, the light reflected by the end surface of the optical system returns to the light source. For example, in signal transmission through an optical fiber, the light emitted from a laser light source is projected onto the end face of the fiber through a lens, and most of it enters the fiber as transmitted light, but is reflected by the lens and end face of the fiber. And returns to the laser light source to disturb the laser oscillation and generate noise. Optical isolators are used to eliminate such noise.

FIG. 3 shows a cross-sectional view of the optical isolator, and FIG. 4 shows an exploded perspective view of the main part thereof. As shown in these figures, a polarizer 1, which is an optical element, a Faraday rotator 2, and an analyzer 3 are arranged in this order, and a magnet 5 is arranged around the Faraday rotator 2. The polarization direction of the polarizer 1 and the analyzer 3 is rotated by 45 degrees, and the optical path length of the Faraday rotator 2 and the magnetic field strength of the magnet 5 rotate the polarization direction by 45 degrees.

The light from the light source enters the optical isolator, passes through the polarizer 1 to become polarized light in one direction, and has a polarization direction when passing through the Faraday rotator 2 to which a magnetic field is applied by the magnet 5. It rotates 45 degrees and passes through the analyzer 3. The polarized light emitted to the optical isolator in this way mostly enters the next optical system (for example, an optical fiber), but a part of the polarized light is reflected on the surface and enters the optical isolator from the opposite direction. Since the polarization direction of the light is the same as that of the analyzer 3, the light passes therethrough, and the Faraday rotator 2 transmits the light after rotating the polarization direction further by 45 degrees. Therefore, the polarization direction of the transmitted light is rotated by 90 degrees with respect to the polarization direction of the polarizer 1, and has a relationship of orthogonal Nicols. Therefore, since the surface reflected light from the optical system does not pass through the optical isolator, it does not return to the light source and noise can be prevented.

In such a conventional optical isolator, in order to hold the polarizer 1 and the analyzer 3 in the lens barrel 6 and the rotor 2 in the magnet 5, holder rings 7, 8 and 9 are used. They are joined with solder or adhesive with proper spacing. The diameters of the holder rings 7, 8 and 9 substantially form the aperture of the effective beam that can pass through the optical isolator.

[0006]

[Problems to be solved by the device]

 When assembling the optical isolator, if the holes of the holder ring 7, holder ring 8 and holder ring 9 that fix the optical components and form the aperture of the transmitted beam are misaligned with each other, some of the transmitted light will be lost. There is a phenomenon that it becomes opaque, and the effective beam diameter that can be substantially transmitted by the optical isolator becomes smaller than the design value. Recently, along with the miniaturization of optical components, miniaturization of optical isolators has been required, and even a slight deviation greatly affects the transmittance. If it is attempted to eliminate such positional deviation, it will take a lot of time to adjust the position. The present invention has been made in order to solve such a problem, and provides an optical isolator capable of transmitting an effective beam having a diameter as designed without requiring assembly time such as position adjustment. With the goal.

[0007]

[Means for Solving the Problems]

 An optical isolator of the present invention made to achieve the above object will be described with reference to FIG. 1 corresponding to an embodiment. As shown in FIG. 1, in the optical isolator of the present invention, a polarizer 1, a Faraday rotator 2 inside a tubular magnet 5 and an analyzer 3 are arranged in this order and held in a fixed position inside an outer cylinder 6. In the optical isolator, a light shield plate 10 having an opening having a diameter smaller than the inner diameters of the holder rings 7, 8, and 9 for holding the polarizer 1, the Faraday rotator 2 in the tubular magnet 5, and the analyzer 3 in place. Is arranged in front of the polarizer 1. It is preferable that the front surface of the light shielding plate 10 is provided with an absorption layer 10a (see FIG. 2) having a wavelength of light that passes through the optical isolator.

[0008]

[Action]

 In the optical isolator of the present invention, the aperture of the shading plate 10 forms the aperture of the effective beam, and the inner diameters of the holder rings 7, 8 and 9 do not form the aperture of the effective beam. Therefore, even if the holes of the holder ring 7, the holder ring 8, and the holder ring 9 are assembled so as to be displaced from each other, the transmitted light rays are not blocked and the optical isolator can effectively transmit the light. The beam diameter will be as designed.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a sectional view of an embodiment of an optical isolator to which the present invention is applied, and FIG. 2 is an exploded perspective view of a main part thereof. As shown in these drawings, a polarizer 1, an Faraday rotator 2, and an analyzer 3, which are optical elements, are arranged in this order. The Faraday rotator 2 is arranged in a cylindrical permanent magnet 5. The polarization direction of the polarizer 1 and the analyzer 3 is rotated by 45 degrees, and the optical path length of the Faraday rotator 2 and the magnetic field strength of the magnet 5 are adapted to rotate the polarization direction by 45 degrees. The polarizer 1 is held in the holder ring 7, the Faraday rotator 2 is fixedly positioned by the holder ring 8 and held in the cylindrical permanent magnet 5, and the analyzer 3 is held in the holder ring 9. . These are held by the lens barrel 6 (not shown in FIG. 2) as a whole.

Further, a light shielding plate 10 is arranged on the front surface of the polarizer 1 in the lens barrel 6. The aperture of the light shielding plate 10 is smaller than the inner diameter of any of the holder ring 7, the holder ring 8 and the holder ring 9, and substantially forms the aperture of the transmitted beam of the optical isolator. The front surface of the light shield plate 10 is plated with nickel phosphorus black as an absorption layer 10a for a light wavelength that passes through the optical isolator. In addition to this, black zinc plating or black nickel plating may be applied.

In this optical isolator, the light from the light source (eg, the light emitted from the optical fiber) enters the polarizer 1 through the opening of the light shielding plate 10. Light that spills out of this opening and strikes the light shielding plate 10 is absorbed by the absorption layer 10a. The movement of the light passing through the optical isolator has already been described below, and thus the description thereof will be omitted. At this time, the light transmitted through the optical isolator is a beam narrowed through an opening smaller than the inner diameter of any of the holder ring 7, the holder ring 8, and the holder ring 9. But there is no interruption.

[0012]

[Effect of the device]

 As described above in detail, in the optical isolator of the present invention, the holder ring of each optical component does not form the aperture of the effective beam, and the aperture of one light shield plate forms the aperture of the effective beam. Even if the holes in the ring group are assembled so that they are offset from each other, some of the transmitted light is not blocked, and the effective beam diameter that the optical isolator can substantially transmit is as designed. Becomes Further, in the optical isolator of the present invention, since it is not necessary to adjust each hole of the holder ring group so as not to shift when assembling, the manufacturing time can be shortened.

[Brief description of drawings]

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

FIG. 2 is an exploded perspective view of essential parts of an embodiment of an optical isolator to which the present invention is applied.

FIG. 3 is a cross-sectional view of a conventional optical isolator.

FIG. 4 is an exploded perspective view of a main part of a conventional optical isolator.

[Explanation of symbols]

Reference numeral 1 is a polarizer, 2 is a Faraday rotator, 3 is an analyzer, 5 is a magnet, 6 is an outer cylinder, 7 · 8 · 9 is a holder ring, 10 is a light shielding plate, and 10a is an absorption layer.

Claims (2)

[Scope of utility model registration request] 1. An optical isolator in which a polarizer, a Faraday rotator in a cylindrical magnet, and an analyzer are arranged in this order, and is held in a fixed position in an outer cylinder, the polarizer and the Faraday rotation in the cylindrical magnet. An optical isolator, characterized in that a light shielding plate having an opening having a diameter smaller than the inner diameter of a holder ring for holding the child and the analyzer in place is arranged on the front surface or both ends of the polarizer. 2. The optical isolator according to claim 1, wherein at least a front surface of the light shielding plate is provided with an absorption layer having an optical wavelength that transmits the optical isolator.