JP2002333528A - Method for polishing end face of optical connector and optical connector per se - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for grinding an end face of an optical connector, a method for securing the optical fiber projecting shape which is needed for realizing physical contact(PC) of an optical fiber in the end face of an optical connector ferrule, and also to provide an optical connector per se. SOLUTION: In the method for polishing the end face of an optical connector ferrule 11 and that of an optical fiber, a grinding device 22 is rotated for nearly the same length of time in the forward and backward directions for grinding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for polishing an end face of an optical connector for connecting an optical fiber, and an optical connector polished by the method.

[0002]

2. Description of the Related Art In an optical connector for connecting an optical fiber, in order to reduce reflected return light at a connection point, (1)
A method of interposing a refractive index matching agent having the same refractive index as that of the core of the optical fiber between the end faces of the optical fiber, and (2) a method using a physical contact (PC) for directly contacting and joining the end faces of the optical fiber have been studied. I have. The method using PC is superior to the method using a refractive index matching agent in terms of workability and handleability. For this reason, in recent years
In order to realize C, an end face polishing method for an optical fiber is being studied.

In a single-core connector, a PC is realized by a method of processing the end face of an optical connector ferrule into a convex spherical surface or the like. However, in a multi-core connector, a plurality of optical fibers need to be collectively PC-connected. Its difficulty is extremely high. As a method of causing the multi-core connector to be a PC, a polishing method for slightly projecting an optical fiber from the ferrule end face of the optical connector has been studied. For example, Patent 31
Japanese Patent Publication No. 29871 discloses a polishing method in which a low hardness member is used for an end face of an optical connector ferrule, and an optical fiber is protruded by utilizing a difference in hardness between materials of the optical fiber and the end face of the optical connector ferrule.

[0004]

However, in the conventional method, it is difficult to secure the symmetry of the optical fiber even if the amount of protrusion of the optical fiber is sufficient. In the initial stage of polishing, the optical fiber protrudes due to the difference in hardness between the optical fiber and the optical connector ferrule. When polishing is further continued, the side of the optical fiber end face that comes into contact with the abrasive grains first in the rotating direction of the polishing board is more easily shaved. Therefore, there is a problem that the shape of the end face of the optical fiber after polishing loses symmetry and becomes oblique as shown in FIG. FIG. 4 is a side view of an optical connector end face polished by a conventional polishing method. 1 is an end face of a ferrule, and 2 is an optical fiber. Especially for multimode fiber,
Since the hardness of the core is lower than the hardness of the clad, the core portion is particularly easy to be shaved, and the proportion of the core is large, so that the above-described tendency of obliqueness appears remarkably. In addition, it is possible to remove the slanted portion by polishing in a later step to make the portion flat or symmetrical. However, there is a problem that the amount of protrusion is reduced by the additional polishing.

[0005] In order to realize a PC, it is necessary that the optical fiber protrudes sufficiently from the end face of the optical connector ferrule and the polished surface is flat or symmetric. If the protrusion of the optical fiber is small, or if the polished surface of the optical fiber is slanted, the connection loss of the communication light at the end of the optical fiber will be large when the optical connector is connected. It causes trouble.

On the other hand, if the amount of protrusion of the optical fiber is extremely large, there occurs a problem that the tip of the optical fiber is easily broken or chipped during or after polishing.

In view of such circumstances, the present invention provides a method for polishing an end face of an optical connector for securing an amount and a shape of an optical fiber protruding for realizing a PC, thereby obtaining an optical connector. The purpose is to:

[0008]

According to the present invention, there is provided a method of polishing an end face of an optical connector ferrule and an end face of an optical fiber. It is characterized in that it is rotated in the direction for substantially the same time.

Particularly, the optical connector is effective for a multi-core connector in which a plurality of optical fibers are fixed. In this case, it is preferable to fix the optical connector ferrule such that a line connecting the center of the optical connector ferrule fixed on the polishing board to the center of the polishing board and the arrangement direction of the optical fibers intersect at a fixed angle.

In addition, the polishing machine has a rotation function of rotating about the center of the polishing machine as an axis and a revolving function of rotating about an axis eccentric from the center. The rotation is performed in combination with the rotation and the rotation. Alternatively, it is preferable that both the rotation directions of the revolution and the rotation are switched at least once or more, and the rotation is performed in the forward rotation direction and the reverse rotation direction for substantially the same time.

On a polishing film stuck on a polishing board,
It is preferable to polish while dropping the liquid in which the abrasive grains are suspended at a constant speed.

In the optical connector after polishing, the amount of protrusion of the optical fiber from the end face of the optical connector ferrule at the end face is 1.5 μm or more and 4.0 μm or less, and the maximum protrusion amount of the optical fiber from the end face of the optical connector ferrule and the optical fiber It is preferable that the difference from the minimum protrusion amount of the core portion from the optical connector ferrule be 0.4 μm or less, thereby realizing a more stable PC.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments. FIG. 1 is an external perspective view of an example of an optical connector to which the edge polishing method of the present invention is applied. Ferrule 11
Is made of an epoxy resin containing silica powder at a high density, and is used for inserting a plurality of optical fiber holes 12 for inserting the two-core optical fiber 2 and a guide pin (not shown) to fit with another ferrule. Has a pair of pin holes 13. Two optical fibers 2 are inserted from the rear end of the ferrule 11 and fixed with an adhesive.

FIG. 2 is a side view of a polishing apparatus used in the embodiment of the present invention. The optical connector 10 is arranged such that a line connecting the center of the ferrule end face 1 and the center of the polishing board 22 and the direction in which the optical fibers 2 are arranged intersect at a fixed angle with the ferrule end face 1 facing down on the fixing jig 21. Is set to A polishing film 2 made of polyester cloth is placed on the polishing plate 22.
The ferrule end face 1 is pressed against the polishing film with a load of 6N. Polishing film 2
Polishing is performed while dropping a polishing liquid mainly containing water in which abrasive grains made of alumina having an average particle diameter of 1.0 μm to 3.0 μm are suspended. A housing 24 is provided below the polishing plate 22, and a drive mechanism such as a motor for rotating the polishing plate 22 for revolution and rotation, a rotating shaft, an eccentric shaft, and a gear is built therein. The rotation directions can be individually reversed.

It is preferable to grind only the rotation or both the rotation and the rotation in the forward rotation direction and the reverse rotation direction for substantially the same time. Thereby, the optical fiber 2 protruding from the ferrule end face 1 can uniformly contact the abrasive grains from both sides. Therefore, the ferrule end face 1 after polishing
The more protruding optical fiber 2 maintains symmetry as shown in FIG. The difference in the polishing time between the normal rotation direction and the reverse rotation direction is preferably 20% or less of the total polishing time. If the difference in polishing time is 20% or more, the symmetry at the end face of the optical fiber is lost, and it is difficult to realize a PC.

After polishing for a predetermined time, the fixing jig 2
Even when the ferrule 11 fixed to 1 is mounted in the opposite direction by 180 ° and the polishing disk 22 is polished in the same rotation direction for the same time, the same effect as when the rotation direction of the polishing disk 22 is changed can be obtained.

As shown in FIG. 3, when the ferrule 11 is fixed to the fixing jig 21, the line connecting the center of the ferrule 11 and the center 34 of the polishing machine and the direction in which the optical fibers 2 are arranged in a line are aligned. , At a certain angle. The angle is preferably not less than 60 ° and not more than 120 °. More preferably, the line connecting the center of the ferrule 11 and the center of the polishing plate 22 is substantially orthogonal to the direction in which the optical fibers 2 are arranged in a line. When orthogonal, all the optical fibers 2 can be located on substantially the same radius on the polishing board, so that the variation in the ease of shaving between the optical fibers can be reduced. The ratio of the number of rotations per unit time between the rotation and the revolution is desirably 2: 1 to 20: 1. Will be the same. The deviation of the angle in the flow direction of the abrasive grains due to the combination of the revolutions falls within a range of ± 30 °.

In order to effectively use the area of the polishing film 23 on the polishing disk, the driving of the polishing disk 22 causes not only the rotation but also a combination of the revolution and the rotation to make a complicated movement. Further, the fixing jig 2 holding the ferrule 11
In some cases, 1 is reciprocated on a polishing machine on a straight line. With only revolution or rotation only, ferrule 11
Since it comes into contact with a limited place on the polishing film 23, the abrasive grains existing in that part are easily worn, and it is difficult to be polished with the polishing time. Therefore, it is preferable to combine revolution and rotation. In addition, only the rotation direction, or both the rotation direction of the revolution and the rotation direction is changed to the normal rotation direction 32 and the reverse rotation direction 33.
Polishing the ferrule 11 for about the same time
The protruding optical fiber 2 can be
It is always polished under the same conditions and can come in contact with abrasive grains that are not evenly worn from both sides.

The method of switching the rotation direction is as follows: (1) polishing the revolution and rotation in the forward rotation direction, and then polishing the revolution and rotation in the reverse rotation direction; and (2) polishing the revolution and rotation in the forward rotation direction. After that, the revolution is polished in the normal rotation direction and the rotation is polished in the reverse rotation direction.
After polishing the revolution and the rotation in the normal rotation direction, the rotation may be performed in the reverse rotation direction without performing the revolution. These may be performed in reverse order. These switching may be repeated a plurality of times. The same effect can be obtained not only by rotating the polishing machine but also by rotating the fixing jig and switching its rotation direction. Of course, the polishing method of the present invention is not limited to the above, and if the optical connector can be uniformly polished from the forward direction and the reverse direction, in particular, the rotating means of the polishing plate, the method, the optical connector fixing jig It is not limited to the moving method. For example, the polishing machine may perform only the rotation motion, and the revolving motion may be such that the fixing jig of the optical connector rotates around the eccentric axis.

As the abrasive grains, silica, alumina, cerium oxide and the like are preferable. The abrasive grains embedded in the polishing film 23 may be used by attaching them to the polishing board 22 or a solution in which the abrasive grains are suspended may be dropped on the polishing film.

In particular, it is preferable to continuously drop abrasive grains on the polishing film 23 during polishing. By continuously dropping the abrasive grains, the abrasive grains that have not always been worn under the same conditions can come into contact with the optical fiber 2, so that the polishing can always be performed under the same conditions. Also, by polishing in the normal rotation direction and the reverse rotation direction for substantially the same time, the abrasive grains in the same state can be uniformly contacted from both side surfaces of the optical fiber 2, so that the polished surface of the optical fiber 2 becomes symmetric.

The ferrule 11 is preferably made of a material having a lower hardness than the optical fiber 2 and having a high dimensional accuracy. A plastic material such as an epoxy resin containing silica powder and PPS (polyphenylene sulfide) is suitable. In the case of the optical connector 10 in which the quartz optical fiber 2 is inserted into a ferrule 11 made of plastic,
Since the difference in hardness between the ferrule 11 and the optical fiber 2 is large as compared with the case where ceramics or metal is used, the optical fiber 2 is easily protruded at the time of polishing, and the effect of the present invention also appears remarkably, and the symmetry of the optical fiber 2 is also improved. Get better.

In order to realize a PC, the amount of protrusion of the optical fiber (a in FIGS. 4 and 5) from the end face of the optical connector ferrule after polishing is preferably 1.5 μm or more and 4.0 μm or less. When the thickness is 1.5 μm or less, it is difficult for the optical fibers to sufficiently PC with each other with a normally applied pressing force of the optical connector. If it is 4.0 μm or more, the tip of the optical fiber is likely to be broken or chipped during or after polishing. More preferably, the thickness is 1.5 μm or more and 3.0 μm or less. The difference between the maximum protrusion amount of the optical fiber at the end face of the optical connector and the minimum protrusion amount of the optical fiber core portion (b in FIGS. 4 and 5) is preferably 0.4 μm or less.
In the case of 0.4 μm or more, when the optical connectors are fitted to each other, the cores of the optical fibers facing each other cannot contact each other, and it is difficult to perform PC. More preferably, 0.2μm
The following is good. According to the present invention, it is possible to obtain a preferable optical fiber protrusion amount for a PC.

In order to realize the required fiber protrusion amount (a in FIGS. 4 and 5) and the difference between the maximum protrusion amount and the minimum protrusion amount (b in FIGS. 4 and 5), polishing time, polishing time Timing to reverse the direction of board rotation,
Conditions are set for items such as the number of times of inversion. The optimum range of each condition differs depending on the polishing apparatus, ferrule material, optical fiber type, and type of abrasive grains. By setting the conditions, it is possible to reliably obtain a polished surface on which PC can be performed regardless of the polishing apparatus, ferrule material, optical fiber type, and abrasive grains.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two multi-mode optical fibers 2 are inserted into a ferrule 11 made of an epoxy resin containing silica powder at a high density and fixed with an adhesive to obtain an optical connector 10 shown in FIG. Was. The ferrule 11 of the optical connector 10 is connected to a fixing jig 21 of the polishing apparatus shown in FIG. 2 by a line connecting the center of the ferrule 11 and the center of the polishing plate 22 and the arrangement direction of the two-core optical fibers 2 by 90 °. And the end face was polished. A polishing film 23 made of a polyester cloth is stuck on the polishing plate 22, and the ferrule 1
1 was pressed against the polishing film with a load of 6N. On the polishing film 23, the average particle size is 1.0 μm to 3.0 μm
The polishing was carried out while dropping a polishing liquid in which abrasive grains of alumina were suspended.

FIG. 3 is a view showing one embodiment of a polishing locus 31 drawn by the optical connector 10 to be polished in the present invention. The polishing locus 31 represents a locus of the optical connector 10 moving on the polishing film when the rotating polishing film 23 is fixed. The rotation speed of the polishing machine is set to 135 rpm, and the ratio of the rotation speed and the revolution speed per unit time is set to 10: 1.
For 60 seconds, and then reverse the revolution and rotation in the reverse direction.
Polishing was performed for a total of 240 seconds, 60 seconds in the forward rotation direction and 60 seconds in the reverse rotation direction.

The 15-plug optical connector 10 was polished, and its end face was measured with a surface roughness meter to measure the unevenness of the optical fiber end face. The shape of the end face of the optical fiber is shown in FIG.
The protruding amount of the optical fiber of 30 fibers in total (Fig. 5
A) in the average was 2.4 μm. Optical fiber 2
The difference between the maximum protrusion amount of the optical fiber and the minimum protrusion amount of the optical fiber core portion 3 (b in FIG. 5) was 0.1 μm on average.
For the measurement of the minimum protrusion amount of the core portion 3, an area with a core diameter of 62.5 μm at the center of the optical fiber was regarded as the core portion 3 from the measurement results of the surface roughness meter, and the minimum protrusion amount was obtained. In addition, when the optical connectors are protruded by 4.0 μm or more, the end of the optical fiber tends to be easily chipped when the test for attaching and detaching the optical connectors is repeated 500 times.

These optical connectors are connected to each other,
When the connection loss at 1.3 μm was measured, it was 0.04 dB on average, and the return loss showed a good value of 35.4 dB.

As a comparison, for the optical connector having the same structure as that shown in FIG. 1 as described above, the polishing apparatus was rotated for 240 seconds only in the normal rotation direction along the locus of FIG. Polishing was performed under the same conditions as described above.

The 15-plug optical connector 10 was polished, and its end face was measured with a surface roughness meter to measure the unevenness of the optical fiber end face. The end face of the optical fiber has a shape as shown in FIG.
A) in the average was 1.4 μm. The difference between the maximum protrusion amount of the optical fiber and the minimum protrusion amount of the core portion of the optical fiber (b in FIG. 4) was 0.8 μm on average.

By connecting these optical connectors to each other, the wavelength
When the connection loss at 1.3 μm was measured, it was 0.15 dB on average, and the return loss was 32.4 dB on average. In particular, an optical fiber in which the protrusion amount of the optical fiber (a in FIG. 4) is 1.5 μm or less, and the difference between the maximum protrusion amount of the optical fiber and the minimum protrusion amount of the core portion of the optical fiber (b in FIG. 4) is 0.2 μm or more. Showed a tendency of high connection loss.

[0032]

As described above, in the method of polishing an end face of an optical connector according to the present invention, the polishing of the optical fiber is performed by rotating the polishing disk by rotating the polishing disk in the forward rotation direction and the reverse rotation direction for substantially the same time. The end face becomes flat or symmetrical with respect to the ferrule end face, and a sufficient fiber protrusion amount for PC can be secured. Further, by realizing such a protruding shape of the optical fiber, the PC of the optical fibers of the optical connectors facing each other is ensured, and an optical connector with low connection loss can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view showing an example of an optical connector whose end face is polished in the present invention.

FIG. 2 is a configuration diagram of a polishing apparatus used in the present invention.

FIG. 3 is a schematic view showing one embodiment of a polishing locus drawn by an optical connector whose end face is polished in the present invention.

FIG. 4 is a schematic diagram showing a state of an optical connector end face polished by a conventional optical connector end face polishing method.

FIG. 5 is a schematic diagram showing a state of an optical connector end face polished by the optical connector end face polishing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferrule end surface 2 Optical fiber 3 Core part 10 Optical connector 11 Ferrule 12 Optical fiber hole 13 Fitting pin hole 21 Ferrule fixing jig 22 Polishing machine 23 Polishing film 24 Housing 31 Polishing locus 32 Forward rotation direction 33 Reverse rotation direction 34 Polishing Center of board

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Teruaki Nishida 1-chome, Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa F-term (reference) 2H036 QA23 QA29 2H038 AA21 CA22 3C049 AA07 AA11 AA16 BA02 BC02 CA01 CB01 CB03

Claims (6)

[Claims] 1. A method of polishing an end face of an optical connector, in which an optical fiber is inserted and fixed in an optical fiber insertion hole provided in an optical connector ferrule, using a rotary polishing machine,
A method of polishing an end face of an optical connector, characterized in that a rotation direction of the polishing board is switched at least once or more, and the polishing board is rotated in a forward rotation direction and a reverse rotation direction for substantially the same time. 2. The optical connector according to claim 1, wherein the optical connector has a plurality of optical fiber insertion holes arranged in a line in the optical connector ferrule,
A multi-core connector in which a plurality of optical fibers are fixed one by one to each other, and a line connecting the center of the optical connector ferrule and the center of the polishing machine intersects at a fixed angle with the arrangement direction of the optical fibers. The method for polishing an end face of an optical connector according to claim 1, wherein the end face is fixed above the polishing board. 3. The rotating polishing machine has a rotation function of rotating about the axis of the polishing machine and a revolving function of rotating about an axis eccentric from the axis of the polishing machine. In addition to driving in combination with the function, the rotation direction of only rotation or the rotation direction of both revolution and rotation is switched at least once, and the rotation is performed in the forward rotation direction and the reverse rotation direction for about the same time. The method for polishing an end face of an optical connector according to claim 1. 4. The end face of the optical connector according to claim 1, wherein the polishing is performed while a liquid in which abrasive grains are suspended is dropped on a polishing film stuck on the rotary polishing machine. Polishing method. 5. The optical connector according to claim 1, wherein an end face of the optical connector ferrule is polished by the method according to claim 1. 6. The protrusion of the optical fiber from the end face of the optical connector ferrule on the end face of the optical connector ferrule is 1.5 μm or more and 4.0 μm or less, and the maximum protrusion of the optical fiber from the end face of the optical connector ferrule. The difference between the amount and the minimum protrusion amount of the optical fiber core from the end face of the optical connector ferrule is 0.4 μm.
The optical connector according to claim 5, wherein: