JP2002341188A - Multi-core optical connector and end face polishing method for multi-core optical connector - Google Patents

Abstract

(57) [Problem] To prevent breakage or chipping of optical fibers due to contact between optical fibers at the end face of an optical connector ferrule when multi-core optical connectors are joined by applying a pressing force. I do. A tip of a plurality of optical fibers constituting a multi-core optical fiber is fixed to an optical connector ferrule of a multi-core optical connector, and an end face of the optical fiber is fixed.
3 projects 2-3 μm from the optical connector ferrule 11,
In order to obtain a multi-core optical connector having an end face having a radius of curvature of 3 mm or more and 60 mm or less, the end face of the optical connector ferrule is polished with alumina abrasive grains, and further polished with cerium oxide abrasive grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing an end face of a communication optical connector used for wiring between communication devices. Particularly, the present invention relates to a method for polishing a multi-core optical connector in which a plurality of optical fibers are inserted and fixed.

[0002]

2. Description of the Related Art Among conventional optical connectors, so-called multi-core optical connectors used for connecting terminals of a plurality of optical fibers include an MT connector, an MPO connector having a built-in MT connector as a component, and the like. There are products. These are attached to the terminal of an optical cable or optical cord, and are used as a wiring cable with a multi-core optical connector or a wiring cord.

In the manufacture of the above-described optical connector, polishing (PC polishing) for a physical contact (PC coupling) for suppressing end face reflection is sometimes performed. For this purpose, the optical fiber needs to protrude from the end face of the optical connector ferrule by 2 to 3 μm.

In the conventional polishing of a multi-fiber optical connector, only the protrusion amount of the optical fiber is controlled, and the shape of the end face of the optical fiber is not considered. On the other hand, for the single-core optical connector, the radius of curvature of the tip of the optical fiber is suitably set to 10 to 25 mm for PC coupling, and various polishing methods have been proposed.

However, the polishing method for a single-core optical connector has not been directly applicable to a multi-core optical connector.
In the multi-fiber optical connector, the amount of protrusion for PC coupling is specified, but the radius of curvature is not specified, and no method for realizing the same has been proposed. In addition, it was not possible to completely eliminate the reflection characteristics and the damage near the core portion, which could cause burnout when high-power light was incident. Due to the above situation, the following issues exist.

[0006]

When a multi-fiber optical connector is polished by a conventional polishing method using alumina abrasive grains or the like so that the optical fiber protrudes from the end face of the optical connector ferrule by 2 to 3 μm, the protruding optical fiber tip Often had a radius of curvature of about 1.5 mm. In addition, the tip of the optical fiber protruded, and the vicinity of the core was sometimes damaged. When the optical connectors polished in this manner are coupled with each other by applying a predetermined pressing force, the optical fibers come into contact with each other, and at that time, the optical fibers may be broken or chipped and become unusable. When light is transmitted using a scratched optical fiber, the reflection characteristics may be degraded, or burning may occur with high output light.

[0007] In the conventional polishing of a multi-core optical connector, the end face of the optical connector ferrule is polished using alumina abrasive grains. Therefore, when the polishing conditions are controlled so that the protrusion amount of the optical fiber is about 3 µm, The radius of curvature of the end face was as small as 1.5 mm.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the ends of a plurality of optical fibers are connected to the end face of an optical connector ferrule so that the optical fibers facing each other are stably PC-coupled. And a multi-core optical connector having an optical fiber end face shape having a radius of curvature larger than 1.5 mm. Particularly, in a multi-fiber optical connector, an optical connector is provided in which the protrusion amount of the optical fiber tip and the radius of curvature of the optical fiber end surface are dimensions and shapes suitable for PC coupling.

Further, the multi-fiber optical connector according to the present invention is characterized in that optical fibers are respectively inserted into a plurality of optical fiber insertion holes of an optical connector ferrule and fixed, and the optical fiber is more than an end face of the optical connector ferrule. Of the optical fiber protrudes 2 to 3 μm and the end face of the optical fiber is 3 to 6 μm.
It has a radius of curvature of 0 mm.

The method for polishing an optical connector according to the present invention is a method for polishing an end face of the optical connector ferrule and an end face of the optical fiber, wherein the optical fiber is inserted into an optical fiber insertion hole of the optical connector ferrule and fixed. The optical fiber is polished so that the tip of the optical fiber protrudes using a polishing liquid, and then the end surface of the optical fiber is polished to a spherical shape using a polishing liquid or polishing paper.

In the polishing method for an optical connector according to the present invention, the optical fiber is polished so that the radius of curvature of the end face is 3 mm or more and 60 mm or less.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a multi-core optical connector and a method for polishing a multi-core optical connector according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a basic configuration of the present invention. FIG. 1A is a plan view of a multi-core optical connector 1 according to the present invention, in which the tip of a multi-core optical fiber core 21 composed of a plurality of optical fibers 2 and integrated with a rubber boot 12 is inserted. It is inserted and fixed in an optical fiber insertion hole 14 provided in the optical connector ferrule 11 of the optical fiber connector 1.
The end opposite to the side where the rubber boot 12 is located is the end face 13 of the optical connector ferrule 11, and the end face 22 of the tip of the optical fiber 2 slightly protrudes from the end face 13 of the ferrule 11 of the multi-fiber optical connector 1.

The length of the tip of the optical fiber 2 protruding from the end face 13 of the ferrule 11 of the multi-core optical connector 1 may be 1 μm or more and 5 μm or less, and is 2 to 3 μm.
Is more preferable.

FIG. 1B shows an end face 13 of the ferrule 11 of the multi-core optical connector 1 shown in FIG. 1A. An end face 22 of the optical fiber 2 is provided at the center, and a pair of guide pin holes are provided on both sides thereof. 15 are arranged.

The optical fiber 2 may be a single mode type or a multi-mode type as long as it is a quartz type optical fiber for communication. For the ferrule 11, a polymer resin material or a ceramic material containing a silica filler is used. Epoxy resin or PPS resin can be used as the resin material.
Zirconia can be used as the ceramic material.

FIG. 2 shows a method of polishing the end face 13 of the optical connector ferrule 11. The polishing apparatus 3 comprises a rotary polishing plate 31, a polishing paper 32 on which a polishing grain 321 is fixed, and a ferrule 11. It is composed of a fixed part 33, a rotating mechanism 34, and a polishing liquid 35.

The polishing liquid 35 is obtained by dispersing and suspending abrasive grains 352 in a solvent 351. Alcohol and water are used for the solvent 351. Alumina, cerium oxide, or silica is used for the abrasive grains 321 and 352. A suitable particle size of alumina is about 1 μm. The particle diameter of cerium oxide and silica is suitably from 0.1 to 0.3 μm. Polishing is polishing paper 3
2, the polishing liquid 35 alone, or the polishing paper 32 and the polishing liquid 35 can be used. The polishing liquid may be dropped on the rotary polishing plate 31 from a supply tank (not shown).

The inventor of the present invention has found that when a multi-fiber optical connector made by a conventional polishing method is connected, the protruding tip of an optical fiber may be broken, and as a result of investigating the cause, the radius of curvature of the end face of the optical fiber is determined. It has been found that the above phenomenon can be avoided by increasing.

For this purpose, it has been found that it is preferable to manufacture the optical fiber by a first polishing step of processing the optical fiber so that the tip of the optical fiber projects, and a second polishing step of processing the end face of the optical fiber into a spherical shape.

The abrasive grains in the first polishing step have a particle size of about 1 μm.
It is preferable to use a polishing liquid mixed with m of alumina,
In the second polishing step, it has been found that it is preferable to use cerium oxide having a particle size of 0.1 to 0.3 [mu] m or polishing paper on which silica is fixed.

By employing the above-mentioned polishing step, the optical fiber tip can be protruded by a predetermined amount and the end face of the optical fiber can be processed into a spherical shape.

FIG. 3 shows the procedure of the polishing step of the present invention. First, in step S1, an optical fiber is inserted into an optical fiber insertion hole of an optical connector ferrule and fixed with an adhesive. In the step S2, as a first polishing step, the optical connector ferrule is set in a polishing apparatus such that the end face of the ferrule faces the abrasive paper as shown in FIG. 2, and the end face of the optical connector ferrule is mixed with a polishing liquid mixed with alumina abrasive grains. Polish. After cleaning the end face, the end face of the optical connector ferrule is polished with polishing paper coated with cerium oxide abrasive grains as a polishing second step in step S3.

In the above description, abrasive paper coated with cerium oxide abrasive grains is used in step S3, but the present invention is not limited to this. For example, in the step S3, a polishing liquid mixed with cerium oxide abrasive grains or silica abrasive grains may be used.

In addition, a polishing liquid containing both alumina abrasive grains and a polishing liquid containing cerium oxide abrasive grains are prepared near the polishing apparatus 3, and the former is supplied at the beginning of the polishing step, and the latter is supplied at the later stage. Indicates that the latter is to be supplied.
The S2 step and the S3 step may be performed continuously without stopping.

Assuming that the fracture strength of quartz glass, which is a material constituting the optical fiber, is 70 to 150 MPa, the stress at the contact of the end face of the optical fiber formed at the same radius of curvature using the Hertz's formula at the contact of the spherical surface is used. Is shown in FIG. Here, the horizontal axis indicates the radius of curvature at the end face of the optical fiber, and the vertical axis indicates the applied pressing force. The pressing force of the multi-fiber optical connector at the time of coupling is usually about 5 to 13 N. For example, in the case of a 4-fiber optical connector, it is considered that one-fourth of the pressure is applied to the end face of one optical fiber. About 1 to about 3N force is applied per heart.

In this case, if the radius of curvature is 2 mm or less, the area is in a small area where there is a possibility of breakage, but the radius of curvature is 5 mm.
By doing so, it is understood that destruction is avoided. That is, the larger the radius of curvature of the end face of the optical fiber, the lower the pressure at the contact portion may be. Thus, it was found that the radius of curvature of the end face of the optical fiber was practically sufficient if it was about 3 mm or more.

Unlike the single-core optical connector, the stress acting per core is small in the multi-core optical connector. Therefore, even if the radius of curvature is smaller than that of the single-core optical connector, the multi-core optical connector has a crack or chip at the tip of the optical fiber. Is unlikely to occur.

On the other hand, as the radius of curvature of the end face of the optical fiber increases, the risk of breakage decreases, but conversely, the amount of deformation of the optical fiber in the optical axis direction when pressure is applied decreases. The fact that the deformation amount is small becomes a serious problem when the protrusion amounts of the individual optical fibers in the multi-fiber optical connector are different. In a multi-core optical connector, the tip positions of the individual optical fibers vary, so that the entire core may be PC-coupled, and the tip of the optical fiber may undergo a greater compressive deformation than a single-core optical connector. That is, in order to connect the whole core to the PC in the multi-core optical connector, the end face of the optical fiber needs to be deformed in the optical axis direction of the optical fiber, and it is necessary to realize the PC connection within a specified pressing force range. Can be

The inventor calculated the drawing amount (compression deformation) of the optical fiber based on the theory of the deformation of the punch in addition to the theory of Hertz. The result is shown in FIG. Here, the horizontal axis is the radius of curvature at the end face of the optical fiber, and the vertical axis is the pressing force required to deform the optical fiber by 0.3 μm in the optical axis direction. The magnitude of this force is 0.3 at a radius of curvature of 3 mm.
Although it is 21 N, it is also found that if the radius of curvature is 60 mm, it is twice as large as 0.49 N, so that it is necessary to set the radius to 60 mm or less if possible.

[0031]

FIG. 6 is a side view of an end face of a multi-core optical connector ferrule after polishing according to a first embodiment of the present invention. The multi-core optical connector ferrule was manufactured as follows. The optical fiber 2 was made of an epoxy resin containing silica filler, using an eight-core optical fiber tape in which eight single-mode quartz optical fibers coated with an ultraviolet-curable acrylic resin were integrated. An optical fiber was inserted through an optical fiber insertion hole provided in the ferrule 12 and fixed with an epoxy adhesive.

The end face 13 of the optical connector ferrule was first polished with a polishing liquid obtained by mixing alumina abrasive particles having a particle size of about 1 μm with water to project a predetermined amount of the optical fiber tip. Subsequently, the end face of the ferrule was polished using a polishing paper coated with cerium oxide abrasive grains having a particle diameter of 0.3 μm.

Similarly, a set of two multi-core optical connectors was prepared. When the radius of curvature r of the 16 optical fiber end faces 22 incorporated in the two completed multi-core optical connectors was measured, it was about 5 mm on average. The average value of the protrusion amount h was 2.8 μm, and the difference between the maximum protrusion amount and the minimum protrusion amount was 0.4 μm. FIG. 7 shows the measurement results. The position where the horizontal axis is perpendicular to the optical fiber optical axis is
The vertical axis indicates the position in the optical fiber optical axis direction.

Subsequently, when this multi-core optical connector was coupled with a pressing force of 10 N and the initial characteristics were measured at a wavelength of 1.55 μm, the PC ratio was 100% and the connection loss was 0.12 dB.

Similarly, five sets of ten multi-core optical connectors were prepared, and 250 times of detachment tests were performed while cleaning the end face every 25 times. Subsequent loss increase is 0.3d compared to the initial value
None of the hearts showed an increase of B or more, and only 5 out of 10 cores with scratches near the core which did not exist after polishing were found.
It was just my heart.

[0036]

COMPARATIVE EXAMPLE As a comparative example, as in the previous embodiment, an eight-core optical fiber tape was used in which eight single-mode quartz-based optical fibers covered with an ultraviolet-curable acrylic resin were integrated. A ferrule 12 made of a filler-containing epoxy resin as a material was inserted and fixed in an optical fiber insertion hole, and was integrated with an epoxy adhesive.

The end face of the multi-fiber optical connector was polished with only the same polishing liquid in which alumina abrasive grains were mixed in water in the same manner as that used in the above-described embodiment, to prepare a set of two multi-fiber optical connectors.

The radius of curvature of the end faces of the 16 optical fibers incorporated in the two completed multi-core optical connectors was about 1.5 mm on average. The average value of the protrusion amount was 3.2 μm, and the difference between the maximum protrusion amount and the minimum protrusion amount was 1.4 μm.

Subsequently, when this multi-core optical connector was coupled with a pressing force of 10 N and the initial characteristics were measured at a wavelength of 1.55 μm, the PC ratio was 50% and the connection loss was 0.76 dB.

Similarly, five sets of ten multi-core optical connectors were prepared, and 250 times of detachment tests were performed while cleaning the end face every 25 times. Subsequent loss increase is 0.3d compared to the initial value
The number of hearts showing an increase of B or more was 79 out of 10 out of 80 hearts. The number of scratched hearts near the core was 10 80
It was 79 hearts.

[0041]

The present invention is an optical connector and a method for polishing an end face of an optical connector as described above, and therefore has the following effects.

Since the optical fiber protrudes from the end face of the optical connector ferrule by a specified length and the radius of curvature of the tip of the optical fiber has a size that hardly causes cracking or chipping, reliable PC coupling can be performed and connection loss can be reduced. it can.

A multi-fiber optical connector in which a plurality of optical fiber insertion holes are formed and optical fibers are inserted through the holes and fixed, wherein the length of the optical fibers protruding from the optical connector ferrule varies. However, by applying the specified pressing force, all the optical fibers incorporated in the multi-core optical connector can be PC-coupled to obtain low connection loss and low reflection characteristics. Cracks and breaks can be prevented.

Since the end face of the optical connector ferrule is polished using a polishing liquid so that the optical fiber protrudes, the end face of the optical fiber is further polished to a spherical shape using a polishing liquid or abrasive paper. The length of the tip of the optical fiber protruding from the end face of the optical connector ferrule and the radius of curvature of the end face of the optical fiber can be finished with good reproducibility to a size suitable for PC coupling.

[Brief description of the drawings]

FIG. 1 shows the structure of a multicore optical connector according to the present invention.

FIG. 2 shows a method of polishing the end face 13 of the optical connector ferrule 11 of the multi-core optical connector according to the present invention.

FIG. 3 is a method for polishing a multi-core optical connector according to the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the radius of curvature of the end face of the optical fiber and the pressing force of the multi-core optical connector according to the present invention for each breaking strength of glass.

FIG. 5 is an explanatory diagram showing a relationship between a radius of curvature of the multi-core optical connector according to the present invention and a pressing force required for deforming the optical fiber.

FIG. 6 is a side view of an end face of the optical connector ferrule after polishing in the first embodiment of the multicore optical connector according to the present invention.

FIG. 7 shows the results of measuring the unevenness of the optical fiber on the end face of the optical connector ferrule in the example of the multi-core optical connector according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 multi-core optical connector 11 ferrule 12 rubber boot 13 end face of optical connector ferrule 14 optical fiber insertion hole 15 guide pin hole 2 optical fiber 21 multi-core optical fiber core wire 21 22 end face of optical fiber 3 polishing device 31 rotating polishing plate 32 polishing paper 321 abrasive grains 33 ferrule fixing part 34 rotation mechanism 35 polishing liquid 351 solvent 352 abrasive grains

Continued on the front page (72) Inventor Tomohiko Ueda 1 Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Sumitomo Electric Industries, Ltd. (72) Inventor Shinji Ogawa 1-Tagamachi, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries Co., Ltd. 2H036 JA01 QA16 QA18 QA22 QA49 3C049 AA07 AA11 AB04 BA02 CA01 CB01 CB03

Claims (5)

[Claims] 1. A multi-fiber optical connector, wherein tips of a plurality of optical fibers protrude from an end face of an optical connector ferrule, and an end face of the optical fiber is formed in a spherical shape. 2. A radius of curvature of an end face of the optical fiber is 3 m.
2. The multi-fiber optical connector according to claim 1, wherein the length is not less than m and not more than 60 mm. 3. The multi-core optical connector according to claim 1, wherein a tip of the optical fiber is projected from an end face of the optical connector ferrule to which a plurality of optical fibers are fixed, and the end face of the optical fiber is finished to a predetermined radius of curvature. Edge polishing method. 4. After polishing the end face of the optical connector ferrule using a polishing liquid so that the optical fiber protrudes,
4. The method for polishing an end face of a multi-core optical connector according to claim 3, wherein the end face of the optical fiber is polished into a spherical shape using a polishing liquid or polishing paper. 5. A radius of curvature of an end face of the optical fiber is 3 m.
The method for polishing an end face of a multi-fiber optical connector according to claim 3 or 4, wherein the length is not less than m and not more than 60mm.