JPH0743546A - Method for grinding end face of connector with optical fiber - Google Patents

Abstract

PURPOSE:To provide the method for grinding the end face of the connector with optical fibers which enables PC connection of even the multiple optical fibers with high reliability and is efficient. CONSTITUTION:This method includes a stage for inserting the optical fibers 11 into the optical fiber insertion holes of the connector 12 having the optical fiber insertion holes and consisting of a material having the coefft. of thermal expansion larger than the coefft. of thermal expansion of the material of the optical fibers 11, a stage for heating up the connector 12 inserted with the optical fibers 11 up to a temp. exceeding ordinary temp. and grinding the end face 14 to be connected of the connector 12 in this state and a stage for projecting the ends of the optical fibers 11 from the end face 14 to be connected by cooling the connector 12 down to ordinary temp.

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 connector with an optical fiber.

[0002]

2. Description of the Related Art Normally, when an optical fiber is attached to a connector, an optical fiber tape core wire 60 is used as shown in FIG.
The coating of the tip portion of is removed to expose the optical fiber 61. Then, the optical fiber 61 is inserted into the optical fiber insertion hole 62 of the connector 65 having the optical fiber insertion hole 62, the guide pin hole 63, and the opening 64 for filling the adhesive, and the end portion 61 a of the optical fiber 61. Is projected from the connected end surface 65a of the connector 65. Further, as shown in FIG. 7, the opening 64 and the exposed front end portion of the optical fiber 61 are filled with an adhesive 66 and dried to fix the optical fiber 61 and the connector 65. Finally, the connected end surface 65a of the connector 65 is polished and finished.

On the other hand, when connecting the optical fibers attached to the connector as described above, if there is a gap in the connecting portion of the optical fiber 61, not only the connection loss increases, but also
Due to the difference in the refractive index between the optical fiber and the air, the light is reflected on the oscillation side, causing the disturbance of the optical signal.

The following method has been adopted in order to prevent the formation of voids in this connection portion. Firstly, there is a method of filling the connecting portion, that is, the end face to be connected of the optical fiber with a matching agent such as oil having the same refractive index as that of the optical fiber when connecting the optical fibers. However, in this method, the connecting work becomes complicated and the matching agent evaporates, so that there is a problem in long-term reliability.

Secondly, there is a physical contact connection method (hereinafter abbreviated as PC connection) for connecting the optical fibers by projecting the connected end surface of the optical fiber from the connected end surface of the connector. When this PC connection is performed, in the single-core optical connector, polishing is performed so that the connected end surface of the optical fiber is a convex spherical surface. In a multi-core optical connector, since this polishing is difficult, polishing using loose abrasive grains is performed. Polishing with loose abrasive grains takes advantage of the fact that the material of the connector is softer than the material of the optical fiber.Because the connector is polished more than the optical fiber, the end of the optical fiber is not covered by the connector. It is made to project from the connection end face.

[0006]

However, in polishing using loose abrasive grains, it takes a long time to project the end portion of the optical fiber from the connected end surface of the connector by a predetermined amount.
Further, this method has a limit in the amount of protrusion. Therefore, this method has poor productivity.

Further, in this method, the amount of protrusion at the end of each optical fiber is not uniform, so that when connecting to a PC,
Unable to make a reliable connection.

The present invention has been made in view of the above points, and is capable of highly reliable PC connection even in a multi-core optical fiber, and is also efficient in polishing a connector end face with an optical fiber. The purpose is to provide.

[0009]

According to the present invention, a step of inserting an optical fiber into the optical fiber insertion hole of a connector having an optical fiber insertion hole and made of a material having a coefficient of thermal expansion larger than that of the material of the optical fiber. A step of raising the temperature of the connector into which the optical fiber is inserted to a temperature exceeding room temperature, and polishing the connected end surface of the connector in that state; cooling the connector to room temperature to connect the optical fiber from the connected end surface. And a step of projecting an end portion of the fiber, to provide a polishing method for an end face of a connector with an optical fiber.

In the present invention, quartz glass or the like can be used as the material of the optical fiber. Further, as the material of the connector having a higher coefficient of thermal expansion than the material of the optical fiber, plastic such as epoxy resin can be used.

The temperature at which the connector is heated must be set in consideration of the amount by which the end of the optical fiber is projected from the connected end face of the connector. That is, the temperature is set to such a degree that the dimensional difference caused by the difference in the coefficient of thermal expansion between the optical fiber material and the connector material substantially matches the desired protrusion amount.

As a method of raising the temperature of the connector, a method of heating with a heater can be used, and as a method of cooling the connector, leaving at room temperature, air cooling, water cooling or the like can be adopted.

[0013]

According to the present invention, a connector made of a material having a coefficient of thermal expansion higher than that of the optical fiber is used to raise the temperature of the connector to a temperature exceeding room temperature, and in that state, the connected end face of the connector is polished to Is cooled to room temperature, and the end of the optical fiber is projected from the connected end face.

When the connector is heated to a temperature higher than room temperature, the connector expands more than the optical fiber due to the difference in coefficient of thermal expansion. In this state, polishing is performed so that the connected end surface of the optical fiber and the connected end surface of the connector are flush with each other. Thereafter, when the connector is cooled, the difference in coefficient of thermal expansion causes the connector to shrink more than the optical fiber. As a result, the end portion of the optical fiber projects from the connected end surface of the connector.

Since the difference in the coefficient of thermal expansion between the optical fiber material and the connector material is utilized in this way, it is possible to secure a sufficient protrusion amount of the optical fiber end portion for PC connection even with a short polishing process. it can. Further, since it is considered that the contraction of the connector uniformly occurs on the end face to be connected, the amount of protrusion of each optical fiber end becomes uniform.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings.

First, the coating at the tip of the four-core tape core wire was peeled off to expose the optical fiber. Then, the optical fiber is inserted into the optical fiber insertion hole of the connector having the four optical fiber insertion holes, the pair of guide pin holes, and the opening for filling the adhesive, and the opening is filled with the adhesive. The tape core wire was attached to the connector by drying. Here, the coefficient of thermal expansion of the optical fiber is 0.51 ×
It is 10 ^-6 1 / ° C, and the coefficient of thermal expansion of the epoxy resin (including glass filler) that is the material of the connector is 1.27 x
It is 10 ^-5 1 / ° C.

FIG. 1 is a perspective view showing a state in which an optical fiber 11 of a tape core wire 10 is inserted into a connector 12 and fixed with an adhesive 13. At this time, the optical fiber 11 projects from the connected end surface 14 of the connector 12 together with the adhesive 13. Note that reference numeral 15 in the drawing denotes a guide pin hole into which a guide pin is inserted when the connectors 12 are butted and connected to each other. Further, the length of the connector 12 in FIG. 1 is 2a, and the center of the connector 12 is the XYZ axis center 0.

Next, using a lapping type polishing machine with fixed abrasives, the connected end surface 14 of the connector 12 was polished while the connector 12 was heated to 90 ° C. by a heater. At this time, the polishing liquid was also heated to the same temperature as the connector 12.

FIG. 2 is a plan view showing a state when the connector 12 is heated and expanded. By heating the connector 12, the connector 12 expands and its length is 2a.
It became long. Therefore, the connector 12 is 90 ° C.
It means that only 2a'-2a has expanded. When the connected end surface 14 of the connector 12 was polished, the length from the center of the connector 12 to the connected end surface 14 became b ′, as shown in FIG. That is, the polishing amount in the polishing process is a'-b ', and the length of the connector 12 after polishing is a'
It became '+ b'.

Next, the connector 12 after the polishing treatment was left at room temperature to be cooled to room temperature, and the optical fiber 11 was projected from the connected end face 14 of the connector 12 as shown in FIG. By cooling the connector 12, the connector 12 contracted by b'-b and its length became short as a + b. At this time, since the optical fiber 11 contracts less than the connector 12, the connected end surface 14 of the connector 12
Protruding from. The protrusion amount ε at this time can be calculated by the following formula.

Ε = k (α ₂ −α ₁ ) × T × b ′ where α ₁ is the coefficient of linear expansion of the optical fiber material, α ₂ is the coefficient of linear expansion of the connector material, and T is when the connector is expanded. The temperature difference between the temperature and the room temperature, and k is a protrusion coefficient mainly relating to the residual stress on the optical fiber due to the adhesive and the polishing environment. By setting the materials of the optical fiber and the connector and the temperature at which the polishing process is performed based on this equation, the protrusion amount can be appropriately changed.

The connected end face 1 of the connector 12 after this cooling
The surface roughness of No. 4 was measured. The result is shown in FIG. Figure 5
As can be seen from the figure, all 4 optical fibers have 1μ
m Projected from the connected end surface.

Further, the polishing treatment time by this method is 30
Seconds, which is significantly shorter than the polishing processing time of 300 seconds for projecting 1 μm in the conventional method.

In the present embodiment, the connector and the polishing liquid were both heated in the polishing process, but the polishing liquid may not be heated as long as the temperature of the connector can be maintained at a temperature higher than room temperature. Although lapping polishing using fixed abrasives has been described in the present embodiment, the present invention is not limited to this and can be applied to lapping and grinding treatments using free abrasives.

[0026]

As described above, the method for polishing an end face of a connector with an optical fiber according to the present invention uses a connector made of a material having a coefficient of thermal expansion larger than that of the optical fiber to raise the temperature of the connector to a temperature higher than room temperature. In that state, the connected end face of the connector is polished, the connector is cooled to room temperature, and the end of the optical fiber is projected from the connected end face.
Even in a multi-core optical fiber, the amount of protrusion at the end of each optical fiber becomes uniform, which enables highly reliable PC connection.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which an optical fiber of a tape core wire is inserted into a connector and fixed with an adhesive.

FIG. 2 is a plan view showing a state when the connector is heated and expanded.

FIG. 3 is a plan view showing the connector after a polishing process.

FIG. 4 is a plan view showing a state after cooling the connector.

FIG. 5 is an explanatory view showing a protruding state of an end portion of an optical fiber.

FIG. 6 is a diagram for explaining a conventional method of attaching an optical fiber to a connector.

FIG. 7 is a diagram showing a state in which an optical fiber is attached to a connector.

[Explanation of symbols]

10 ... Tape core wire, 11 ... Optical fiber, 12 ... Connector, 13 ... Adhesive agent, 14 ... Connected end surface, 15 ... Guide pin hole.

Front page continuation (72) Inventor Shinji Nagasawa 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A step of inserting an optical fiber into the optical fiber insertion hole of a connector having an optical fiber insertion hole and made of a material having a thermal expansion coefficient higher than that of the material of the optical fiber, and inserting the optical fiber. A step of raising the temperature of the connector to a temperature exceeding room temperature and polishing the connected end surface of the connector in that state, and a step of cooling the connector to room temperature and projecting the end portion of the optical fiber from the connected end surface. A method of polishing an end face of a connector with an optical fiber, comprising: