JP4925323B2 - Optical fiber collimator and optical fiber collimator array manufacturing method - Google Patents

Description

  The present invention relates to an optical fiber collimator in which a GRIN lens is fused to the tip of an optical fiber, and an optical fiber collimator array in which a plurality of optical fiber collimators are integrated. Particularly, the tip surface of the GRIN lens is spherical and has little return loss. And a manufacturing method thereof.

  In a conventional contact-type optical connector (for example, Patent Document 1) for connecting optical fibers to each other, if a slight amount of dust adheres to the fiber end surface during connection, the connection loss increases. In addition, when used in such a state for a long time, there is a considerable problem that the end face of the optical fiber is burned out. Therefore, a non-contact type optical connector that can be manufactured at low cost is desired. In addition, the optical connector requires a small size, low cost, low insertion loss (<0.5 dB), and low return loss (<−50 dB).

When a GRIN lens (grounded index lens without a clad) that can be fused to an optical fiber is used, alignment work becomes unnecessary when the fiber and the lens are assembled (Patent Document 2). However, when the tip is finished with a vertical flat surface, most of the light reflected by the tip surface returns to the fiber core, so even if AR coating is performed, the return loss becomes as large as about -30 dB.
FIG. 11 is an explanatory diagram of an optical fiber collimator 11 in which the GRIN lens 2 is fused to the tip of the single mode optical fiber 1. Light from the core of the optical fiber 1 travels through the GRIN lens 1 as indicated by an arrow and radiates from the end surface of the GRIN lens 2, but a part of the light is reflected by the end surface of the GRIN lens and returns to the core of the optical fiber (the reflected light is dotted) Display).

As a measure for reducing such a return loss, there is a method in which the tip is polished obliquely. As a result, the return loss is reduced to -50 dB or less, but it is necessary to perform rotational alignment in the axial direction so that the surfaces are parallel when assembled.
FIG. 12 is an explanatory diagram of an optical connector having a pair of optical fiber collimators 12 in which the GRIN lens 2 is fused to the tip of the single mode optical fiber 1 and the tip of the GRIN lens is obliquely polished. As shown in the figure, since the outgoing optical axis does not coincide with the fiber axis due to refraction, the fiber collimator pair cannot be arranged on the same axis and must be offset, so the X axis, Y axis, Z Axis alignment work is unavoidable and takes too much time, making it unusable for use as a connector.

  The following patent document indicates that a return loss characteristic of −50 dB or less required for practical use can be secured by fusing a GI (graded index) fiber to the tip of the optical fiber and making the tip of the GI fiber spherical. 3 is disclosed. By making the tip of the GI fiber a spherical surface, the return loss is reduced and the outgoing optical axis coincides with the axis of the fiber, so that the fiber collimator pair can be arranged on the same axis, and the assembly of the collimator pair becomes easy.

In Patent Document 3, chemical etching is used as a method of processing a GI fiber tip on a spherical surface. In this method, after forming a protective film (plating) on the outer surface of the GI fiber, it is cut to a predetermined length, and then the tip of the GI fiber is chemically etched. However, chemical etching requires a long etching time of 1 to 4 hours, and the processes of “plating” and “chemical etching” take too much time and labor. Although there is a description that physical etching by plasma or the like is possible, no specific method is disclosed.
Further, it is difficult to finally remove the plating, and there is a problem that it is difficult to assemble in a general ferrule used for the connector.
JP-A-61-87111 Japanese Patent Laid-Open No. 2005-115097 JP 2005-128267 A

An object of the present invention is to make it possible to easily manufacture a versatile optical fiber collimator in which the tip of a GRIN lens fused to the tip of an optical fiber is a spherical surface.
The present invention also makes it possible to easily manufacture a versatile optical fiber collimator array in which a large number of optical fiber collimators having a spherical tip of a GRIN lens fused to the tip of an optical fiber are integrated. Is an issue.

The present invention includes a step of inserting and temporarily fixing the tip portions of a plurality of collimator members having a GRIN lens fused to the tip of an optical fiber into each core of a multi-core ferrule , and the ferrule on a polishing film affixed on an elastic pad. In a state where the ferrule and the polishing film are relatively moved in a state of pressing, a step of polishing the plurality of GRIN lens tips together with the ferrule into a spherical shape, a step of extracting the plurality of collimator members from the ferrule, And a step of forming an antireflection film at the tip of the GRIN lens of each collimator member.

  As the ferrule, a multi-core ferrule is used, and by inserting the tip end portion of the collimator member into each core, temporarily fixing and polishing, a large number of collimator members can be simultaneously polished, and the manufacturing efficiency of the optical fiber collimator Will improve.

  The present invention also includes a step of inserting tip portions of a plurality of collimator members having a GRIN lens fused to the tip of an optical fiber into each core of a multi-core ferrule and fixing with an adhesive, and a polishing film affixed on an elastic pad A step of relatively moving the ferrule and the polishing film in a state where the ferrule is pressed to polish the front ends of the plurality of GRIN lenses in a spherical shape together with the ferrule. It is a manufacturing method. After the polishing is completed, an antireflection film can be formed on the tip of the GRIN lens as necessary.

  Since the manufacturing method of the optical fiber collimator and the manufacturing method of the optical fiber collimator array of the present invention polish the tip of the GRIN lens together with the ferrule, it is possible to prevent the collimator member from being damaged during the polishing. In addition, since the tip of the GRIN lens is automatically polished into a spherical shape by polishing with a polishing film affixed on an elastic pad, the polishing operation is extremely easy and the optical fiber collimator or the optical fiber collimator array is highly efficient. Can be manufactured.

  Moreover, since the optical fiber collimator manufactured by the method of the present invention does not perform chemical etching, the outer periphery of the collimator has no plating and is excellent in versatility.

  Moreover, the optical fiber collimator array manufactured by the method of the present invention can be used as an optical fiber collimator array with the polished ferrule.

  The material of the ferrule can be made of zirconia, glass, resin, or the like.

  The means for inserting and temporarily fixing the tip of the collimator member into the ferrule is free, but for example, a thermoplastic resin adhesive can be used. The inner wall of the ferrule core hole and the outer peripheral part of the collimator can be bonded with a thermoplastic resin adhesive, or the outer peripheral part of the collimator can be bonded to the rear end face of the ferrule with a thermoplastic resin adhesive. What is necessary is just to heat a ferrule when extracting a collimator member.

  As means for inserting and fixing the collimator member into the ferrule, epoxy resin or the like can be used.

As an apparatus for polishing the tip of the GRIN lens into a spherical shape together with the ferrule, for example, a polishing apparatus 13 shown in FIG. 9 can be used.
The polishing apparatus 13 includes a rotary table 14, an elastic pad 15, a polishing film 16, a shaft 17, a weight 18, a ferrule holding jig 19, a fiber holding rod 20, and the like. The rotary table 14 rotates about its center as an axis and revolves around two axes slightly apart from the center. As a result, the rotary table moves in a complicated manner, and the ferrule is polished in all directions. The elastic pad 15 is a disk made of an elastic body such as rubber, and is attached to the upper surface of the rotary table 14. The polishing film 16 is a thin sheet whose upper surface is a polishing surface having a large number of abrasive grains, and is attached to the upper surface of the elastic pad 15. A cylindrical weight 18 is inserted through the shaft 17 so as to be movable up and down. The ferrule holder 19 holds the ferrule inserted through the collimator member, and is fixed to the weight 18. Therefore, the ferrule is pressed against the polishing film 16 by the weight of the weight 18, and polishing is performed. The fiber holding rod 20 holds the optical fiber 1 extending from the rear end of the ferrule.

The polishing apparatus 13 polishes the ferrule into which the collimator member is inserted, and polishes the tip of the GRIN lens at the tip of the collimator member into a spherical shape together with the ferrule. FIG. 10 is an explanatory diagram of a state in which the ferrule is polished. When the ferrule 4 is pressed against the polishing film 16, the elastic pad 15 and the polishing film 16 at that portion are deformed and depressed. Since the polishing is performed in such a state, the tip of the ferrule 4 and the GRIN lens 2 are polished into a spherical shape.
When the tip portions of a plurality of collimator members are inserted into each core of the multi-core ferrule and polished, the spherical portion at the tip of the GRIN lens is polished in a state protruding from the tip surface of the multi-core ferrule (FIG. 8).
The curvature of polishing into a spherical shape can be changed by adjusting the diameter of the ferrule and the hardness of the elastic pad. That is, the smaller the ferrule diameter and the softer the elastic pad, the larger the curvature (the smaller the radius of curvature).

  As the antireflection film formed on the front end of the GRIN lens, a conventionally used antireflection film can be used. If the reflectance of the antireflection film is 0.2% or less, the final return loss can be made −56 dB or less.

  First, a GRIN lens 2 having a diameter of 125 μm is fused to the tip of a single mode optical fiber 1 having a diameter of 125 μm, and the GRIN lens 2 is cut into an appropriate length to produce a collimator member 3 ′. The state is shown in FIG. The length of the GRIN lens 2 is a length obtained by adding a polishing margin to a predetermined length (a length that is an odd multiple of 1/4 of the meandering period of light traveling through the GRIN lens).

  Next, the tip of the collimator member 3 'is inserted into the single core ferrule 4 and temporarily fixed with a thermoplastic resin adhesive. The state is shown in FIG.

  Next, the ferrule tip surface and the GRIN lens tip surface are polished into a spherical shape by the polishing apparatus 13. FIG. 3 shows a state where the polishing is completed.

  Next, the ferrule 4 is heated, the optical fiber collimator 3 is extracted from the ferrule 4, and the adhesive is washed. Further, an antireflection film is formed at the tip of the GRIN lens 2 to complete the optical fiber collimator 3 shown in FIG.

  The optical fiber collimator manufactured by the method of the present invention has excellent versatility and can be used for various applications. FIG. 5 shows an example in which an optical fiber collimator 3 is inserted and fixed in a capillary (made of glass, zirconia, etc.) as a pair and is used as an ultra-compact collimator pair module. The pair of collimators have almost no misalignment or angular misalignment, and only the mutual distance needs to be adjusted. Therefore, the manufacture is very simple and highly efficient optical connection is possible.

  FIG. 6 shows an example in which the collimator pair module of FIG. 5 is used as a passive module in which a passive device such as a filter is sandwiched between the pair of collimators. Also in this case, since only the distance between the collimators needs to be adjusted, the manufacture is very simple.

  A multi-core ferrule can be used instead of the single-core ferrule. FIG. 7 shows an example of a multi-core ferrule. The multi-core ferrule 7 has 16 core holes 8. When the collimator member 3 ′ is inserted into each core hole 18 and polished, the spherical portion at the tip of the GRIN lens is polished in a state of protruding from the tip of the multi-core ferrule as shown in FIG. By removing the polished optical fiber collimator 3 from the ferrule and forming an antireflection film, 16 optical fiber collimators 3 can be obtained at a time.

When the collimator member 3 ′ is fixed to the multi-core ferrule 7 with an epoxy resin adhesive or the like, it can be used as it is as an optical fiber collimator array in the state where the polishing shown in FIG. From the state of FIG. 8, it is desirable to form an antireflection film on the front end surface of the GRIN lens.
The optical fiber collimator array manufactured by the method of the present invention can be inserted into a cylindrical capillary and used as a collimator array pair module or a passive module, as in the case of the single core shown in FIGS.

It is a section explanatory view of collimator member 3 '. It is a cross-sectional explanatory view of the ferrule 4 with the collimator member 3 ′ inserted therein. FIG. 3 is a cross-sectional explanatory view of a ferrule 4 and an optical fiber collimator 3 polished into a spherical shape. FIG. 3 is a cross-sectional explanatory view of the optical fiber collimator 3. It is a section explanatory view of a collimator pair module. It is a section explanatory view of a passive module. 3 is a perspective view of a multi-core ferrule 7. FIG. FIG. 3 is a cross-sectional explanatory view of a multi-core ferrule 7 and an optical fiber collimator 3 polished into a spherical shape. It is explanatory drawing of the grinding | polishing apparatus. It is explanatory drawing of the state of grinding | polishing by the grinding | polishing apparatus 13. FIG. 3 is a cross-sectional explanatory view of the optical fiber collimator 11. FIG. It is explanatory drawing of the state which made the optical fiber collimator 12 a pair.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 GRIN lens 3 Optical fiber collimator 3 'Collimator member 4 Ferrule 5 Capillary 6 Device 7 Multi-core ferrule 8 Core hole 9 Optical fiber collimator array 11 Optical fiber collimator 12 Optical fiber collimator 13 Polishing device 14 Rotary table 15 Elastic pad 16 Polishing film 17 Axis 18 Weight 19 Ferrule holding jig 20 Fiber holding rod

Claims (2)

Inserting the tip portions of a plurality of collimator members having a GRIN lens fused to the tip of the optical fiber into each core of the multi-core ferrule, and temporarily fixing;
In a state where the ferrule is pressed against a polishing film affixed on an elastic pad, the ferrule and the polishing film are relatively moved, and a plurality of the GRIN lens tips are polished into a spherical shape together with the ferrule;
Extracting a plurality of the collimator members from the ferrule;
And a step of forming an antireflection film at the tip of the GRIN lens of each collimator member. Inserting the tip portions of a plurality of collimator members each having a GRIN lens fused to the tip of the optical fiber into each core of the multi-core ferrule and fixing with an adhesive;
The ferrule and the polishing film are relatively moved in a state in which the ferrule is pressed against the polishing film affixed on the elastic pad, and a plurality of GRIN lens tips are polished together with the ferrule into a spherical shape. A method for manufacturing an optical fiber collimator array.