JPH04247411A - Fiber input/output type optical parts - Google Patents

Abstract

PURPOSE:To lower the coupling loss of light in the fiber input/output type optical parts, such as optical isolator, which are combined with an optical element part and a fiber collimator by easily aligning optical axes by the simple adjustment alone even with less severe working accuracy. CONSTITUTION:A non-antimetrical part 10 and the fiber collimator 12 are built into a housing 14. The housing has a circular through-hole 16 for insertion of the collimator and holds the non-antimetrical part by inclining this part with the central axis thereof. The collimator has a cylindrical sleeve 20 having the circular through-hole 26 inclined with the central axis, a spherical lens 22, and a ferrule 24 with a fiber diagonally polished at the front end. A cylindrical sleeve is inserted into the housing and the ferrule into the cylindrical sleeve and the position where the coupling loss of light is minimized is found by rotating the sleeve and the ferrule. The sleeve and the ferrule are then fixed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber input/output type optical component that combines an optical element section and a fiber collimator, and the optical element section and the optical fiber are coupled by spatial propagation of light. More specifically, by providing an inclined circular through hole in the cylindrical housing that holds the optical element and the cylindrical sleeve that holds the ferrule, and making them fit together, the optical axis can be adjusted by their relative rotation. This relates to optical components that can be combined. This technique is used, for example, in polarization-independent optical isolators in which fiber collimators are disposed on both sides of an optical element section with a non-reciprocal function.

0002

2. Description of the Related Art The case of a polarization-independent optical isolator, which is a typical application example of the present invention, will be described below. Optical isolators are used in optical communications and the like to remove reflected light returning to a laser light source. There are various types of optical isolators, one of which is an input/output fiber type optical isolator that uses a uniaxial single crystal (birefringent polarizing plate) such as a wedge-shaped rutile single crystal as a polarizer and eliminates polarization dependence. be.

This type of optical isolator has a 45-degree Faraday rotator mounted inside a cylindrical permanent magnet, and polarizers made of wedge-shaped uniaxial single crystals are placed on both sides of the rotator, so that their optical axes are offset by 45 degrees. It is constructed by arranging a lens and a ferrule with a fiber on each side of the ferrule. Technically, it is important here to minimize the coupling loss of light between the two optical fibers.

[0004] As for the assembly process of such an optical isolator, there is a method in which a collimator equipped with a lens and a ferrule is made and then the collimators are coupled together, and a method in which the ferrule is first fixed to a housing and then the lens is inserted. - There is a method of adjusting and combining. Fixing of these used parts is
If the member is block-shaped, this is done by inserting a tapered block into the gap, and if the member is cylindrical, this is done by increasing the dimensional accuracy to eliminate the gap or by pressing it with a screw or the like.

[0005]

However, if the member is block-shaped, it is difficult to miniaturize and adjust it, and the fixing locations are not circularly symmetrical, resulting in relatively poor temperature characteristics. In addition, if the component is cylindrical, it is difficult to achieve precision, and even if precision could be achieved, the light may be bent or shifted parallel due to the inclination of the non-reciprocal part or ferrule, making it difficult to achieve coupling without adjustment. It is difficult. Even if it is pressed using a screw or the like, the optical axis alignment (positioning) work is not necessarily easy.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a fiber input/output system that can easily align the optical axis by simple adjustment even with loose processing precision and reduce optical coupling loss. Our goal is to provide molded optical components.

[0007]

SUMMARY OF THE INVENTION The present invention is an optical component in which an optical element part and a fiber collimator are built into a housing, and the optical element part and the optical fiber are coupled by spatial propagation of light. The housing is a cylindrical structure that has a circular through hole for inserting a fiber collimator and a recess that holds the optical element section at an angle with respect to its central axis. Further, the fiber collimator includes a cylindrical sleeve having an outer peripheral surface with an outer diameter approximately equal to the diameter of the circular through hole of the casing and a circular through hole inclined with respect to the central axis thereof, and a circular through hole of the cylindrical sleeve. It includes a lens installed in the through hole and a fiber-attached ferrule having an outer diameter approximately equal to the diameter of the cylindrical sleeve and having an obliquely polished tip. Then insert the cylindrical sleeve into the circular through hole of the housing,
The ferrule is inserted into the circular through hole of the cylindrical sleeve, and the optical axes are aligned and fixed by rotating them relative to each other.

When the optical component is, for example, a polarization-independent optical isolator, wedge-shaped uniaxial single crystals are used as the optical element on both sides of a 45-degree Faraday rotator housed in a cylindrical permanent magnet. A non-reciprocal section in which a polarizer is arranged is used, and fiber collimators are arranged on both sides of the non-reciprocal section. Note that the fiber end face located at the tip of the ferrule is polished diagonally.

[0009]

[Operation] For example, when light is emitted from an optical fiber, if the cylindrical sleeve is rotated with respect to the housing, the trajectory of the light changes on the conical surface. In addition, when the ferrule is rotated relative to the cylindrical sleeve, the optical fiber tip is polished diagonally, so the light is refracted and moves in a circular motion, so the trajectory of the light emitted from the optical fiber is parallel. changes along the cylindrical surface. Therefore, the optical coupling loss changes depending on the relative positional relationship between the cylindrical sleeve and the ferrule with respect to the housing, and there is an optimal position where the loss is minimized. Assembly and adjustment are completed by finding the optimal position and fixing it at that position.

In the case of an optical isolator, since ferrules with fibers are located on both sides, by performing rotational adjustment on both sides, the positions and directions of input and output from both ferrules are changed, and the optimum position can be found. If the fiber end face located at the tip of the ferrule is obliquely polished, it is possible to correct the deviation from the central axis of the optical path spatially propagating within the non-reciprocal portion, and to reduce reflection within the optical component itself.

[0011]

Embodiment FIG. 1 is a sectional view showing an embodiment of a polarization-independent optical isolator with fiber input and output according to the present invention.
FIG. 2 is an explanatory diagram of its assembly. This optical isolator is
The non-reciprocal part 10 and the fiber collimators 12 located on both sides thereof are built into a housing 14, and each member is coupled by spatial propagation of light.

The housing 14 is made of stainless steel and has a circular through hole 16 for inserting the fiber collimator 12,
It is a cylindrical structure having a concave portion 18 that holds the non-reciprocal portion 10 at an angle with respect to its central axis. The recess 18 is located in the housing 1.
4, and is carved perpendicular to the side surface. Here, the tilt angle between the circular through hole 16 and the center line of the housing 14 is 4 degrees. The fiber collimator 12 includes a cylindrical sleeve 20, a ball lens 22 built into the sleeve,
and a ferrule 24 with a fiber. The cylindrical sleeve 20 is also made of stainless steel, and the diameter of its outer peripheral surface is approximately equal to the diameter of the circular through hole 16 of the housing 14 (provided that the dimensional accuracy allows the cylindrical sleeve 20 to fit into the circular through hole 16 and rotate). , a circular through hole 26 inclined with respect to its central axis.
is formed. The ball lens 22 is press-fitted into the circular through hole 26. The diameter of the cylindrical sleeve 20 is the same as that of the ferrule 2.
approximately equal to the outer diameter of ferrule 24 (however, in this case, ferrule 24
is of such dimensional accuracy that it can be fitted into the circular through hole 26 and rotated)
. The tilt angle between the outer peripheral surface of the cylindrical sleeve 20 and the central axis of the circular through hole is also 4 degrees.

Note that the fiber-attached ferrule is one in which a part of the optical fiber 28 is glued at the center of the ferrule 24. The non-reciprocal section 10 consists of a 45-degree Faraday rotator 32 housed within a cylindrical permanent magnet 30 and polarizers 34 placed on both sides thereof. Both polarizers 34 are wedge-shaped (angle of inclination 4 degrees)
of rutile single crystal plates, and their optical axes are aligned with each other by 4.
Arrange them so that they differ by 5 degrees. This non-reciprocal part 10 is actually assembled using a holder (not shown) or the like.

First, the non-reciprocal portion 10 is fitted from the side into the recess 18 formed in the housing 14 and fixed by welding. Next, the cylindrical sleeve 20 is inserted into the circular through hole 16 of the housing 14 from both ends, and the fiber-equipped ferrule 24 is further inserted into the circular through hole 26 of the cylindrical sleeve 20, and they are rotated relative to each other. Adjust. When the ferrule 24 and the cylindrical sleeve 20 are rotated, the light emitting position at the ferrule 24 changes in a circular motion, and the light emitting and incident angles also change. The position where the loss is minimum can be found. It is fixed by welding while maintaining its optimal position. Note that the cylindrical sleeve 2
Needless to say, the axial position of the ferrule 24 within the ferrule 24 is adjusted so that the end face of the optical fiber 28 matches the focal position of the spherical lens 22.

The basic operation of the optical isolator is exactly the same as that of the optical isolator of the conventional structure. If one of the two polarizers 34 functions as a polarizer in a narrow sense, the other functions as an analyzer. In the forward direction, the light input from the first (one) fiber is output as is from the second (other) fiber, but in the reverse direction, the light input from the second fiber is output from the first fiber. There is no output from . In other words, non-reciprocal operation is performed. As a result, for example, the light output from the laser light source is output to the optical transmission path, but the reflected light can be prevented from returning to the laser light source.

The fiber end face (including the ferrule tip) is obliquely polished in advance, and the inclination angle can be adjusted to exactly offset the amount of deviation from the central axis of the optical path spatially propagating in the non-reciprocal portion. Here it is set to 8 degrees. This oblique polishing also reduces reflection within the optical isolator itself.

Although the present invention has been described above with reference to the case where it is applied to a polarization-independent optical isolator with fiber input and output, the present invention is not limited to such a configuration. Needless to say, the present invention can be applied to any optical component that combines an optical fiber and an optical passive element or an optical active element, and in which light is spatially propagated and coupled between them. Therefore, in addition to the case where the optical fiber is located on both sides of the optical element section, the case where the optical fiber is located only on one side is also included.

[0018]

Effects of the Invention As described above, the present invention has a structure in which the casing for holding the optical element portion and the cylindrical sleeve for holding the ferrule are provided with inclined through holes and are rotatably fitted into each other. By rotating each member, angular misalignment can be relatively easily adjusted using members with a simple structure, even with relatively low processing precision, and an optical component with low optical coupling loss can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a fiber input/output polarization-independent optical isolator to which the present invention is applied.

FIG. 2 is an explanatory diagram of the assembly of FIG. 1;

[Explanation of symbols]

10 Non-reciprocal part 12 Fiber collimator 14 Housing 16 Circular through hole 18 Recess 20 Cylindrical sleeve 22 Ball lens 24 Ferrule with fiber 26 Circular through hole 28 Optical fiber

Claims (2)

[Claims] 1. An optical component in which an optical element part and a fiber collimator are built into a housing, and the optical element part and the optical fiber are coupled by spatial propagation of light, wherein the housing has a circular shape for inserting the fiber collimator. The fiber collimator is a cylindrical structure having a through hole and a concave portion for tilting and holding the optical element portion with respect to its central axis.
A cylindrical sleeve having an outer circumferential surface with an outer diameter approximately equal to the diameter of the circular through hole of the casing and a circular through hole inclined with respect to its central axis, and a lens installed in the circular through hole of the cylindrical sleeve. and a fiber-attached ferrule having an outer diameter approximately equal to the diameter of the cylindrical sleeve and having an obliquely polished tip.The cylindrical sleeve is inserted into the circular through hole of the housing, and the ferrule is inserted into the cylindrical sleeve. A fiber input/output type optical component characterized by being inserted into a circular through hole and relatively rotated to align and fix the optical axis. 2. The optical element part is a non-reciprocal part that combines a 45-degree Faraday rotator housed in a cylindrical permanent magnet and polarizers made of a wedge-shaped uniaxial single crystal arranged on both sides of the rotator, and 2. The fiber input/output type optical component according to claim 1, wherein a polarization-independent optical isolator is constructed by disposing collimators on both sides of the non-reciprocal portion.