JPH0815566A - Optical connector manufacturing method - Google Patents

Abstract

(57) [Abstract] [Purpose] To easily and inexpensively manufacture a communication optical connector that requires a high return loss used in a system for transmitting an image or a high-speed optical signal. A shaft portion of a ferrule 10 is made of a glass material. First, a step of previously polishing the ferrule tip into a convex spherical shape is performed, and then an optical fiber 14 from which the tip coating is removed is attached by a photo-curing type adhesive. A step of inserting and fixing it in the ferrule using an agent, a first polishing step of roughly polishing the fiber-fixed ferrule with a lapping film 17 having alumina fixed, and fixing cerium oxide. The polishing step is composed of a second step of performing final polishing with the wrapping film 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical connector which is arranged in the middle of an optical fiber transmission line and used for switching or cutting the transmission line, and particularly to image transmission and high-speed optical transmission. The purpose of the present invention is to easily and inexpensively manufacture a communication optical connector which is used in a system for transmitting signals and which requires a high return loss.

[0002]

2. Description of the Related Art At present, as an optical connector capable of obtaining a high return loss for communication, a fiber is inserted into a member called a "ferrule" whose inner and outer diameters are processed with high precision.
After fixing, the end surface of the connecting part is polished into a convex spherical surface, and the fibers are physically brought into contact with each other to be connected by a PC (Physical).
Contact) type optical connector is used.

An example of manufacturing such a PC type optical connector will be described below. First, a ferrule made of ceramics such as alumina or zirconia is filled with a two-component thermosetting epoxy adhesive, the fiber with the coating removed for a long time is inserted, and the fiber is fixed by heating. Then, the fiber protruding excessively is cut. To do. As the first polishing step, dry polishing is performed with a silicon carbide wrapping film for removing the adhesive. In the second polishing step, a convex spherical surface is polished by pouring a solution containing diamond abrasive grains on the elastic film. In the third polishing step, a solution containing ultrafine silicon oxide abrasive grains having a particle size of 0.1 μm or less is poured on the elastic film to perform final polishing. Finally, the procedure was to combine housing parts such as springs and plugs.

The highest cost here is the ferrule member and its polishing process, which occupy more than half of the entire connector.

Therefore, in recent years, the application of glass ferrules has begun to be studied in order to reduce the cost of members. This is a method in which the ferrule is manufactured from a glass material that is cheaper than ceramics, and the fiber is fixed with a photo-curing adhesive.

However, even in this case, it was difficult to achieve a large economy in the conventional polishing process. There was also a ferrule (predome ferrule) in which the ferrule was processed in advance with a convex spherical surface, but in order to obtain a high return loss, it was basically manufactured by the same polishing process using abrasive grains, so It was not linked to economicization.

[0007]

In the above polishing step,
Since a solution containing abrasive grains is used in the second and third polishing steps, it is necessary to sufficiently wash the ferrule to remove the abrasive grains attached to the ferrule after polishing.
This is because if the abrasive grains remain, it may cause damage to the fiber during the subsequent polishing step or when the fiber is used as a connector.

Further, since the abrasive grains themselves are contaminated by the residue of the polished ferrule and the like, it is necessary to wash the elastic film at the same time as disposing each time. Abrasive grains of diamond and ultrafine silicon oxide used here are quite expensive, and although they are used in small quantities, they are thrown away each time, which prevents the economy.

Further, in the conventional ceramic ferrule, since the properties of the fiber made of quartz glass and the material itself are largely different from each other, it is easy to make a difference in the manner of abrasion due to polishing.
Therefore, if polished poorly, the end face of the fiber tends to project or retract with respect to the ferrule, but this causes a problem in stability when the connector is connected. Therefore, in the conventional manufacturing method, first, the ferrule and the fiber are polished into the same convex spherical shape by polishing mainly with mechanical properties using diamond in the precision polishing step. However, if the fiber is polished with a hard material such as diamond, a modified layer is created on the end face of the fiber due to processing, and the return loss deteriorates.Therefore, a slight polishing with silicon oxide is performed to remove this modified layer. Was being given.
It has been well known that cerium oxide is excellent as an abrasive for optical glass, but in the case of an optical connector, it cannot be applied yet because the fiber is selectively shaved due to the property difference from the ferrule described above. It was

According to the present invention, a lapping film having a fixed abrasive is used instead of the above polishing step to simplify the troublesome cleaning step, shorten the polishing time, and eliminate the use of disposable abrasive grains. An object of the present invention is to provide a low-cost optical connector manufacturing method.

[0011]

The method of the present invention for achieving the above object is a method for manufacturing an optical connector in which an optical fiber is inserted into a ferrule and optical axes are aligned by aligning the ferrules with each other. The shaft part of is composed of a glass material, and the step of first polishing the ferrule tip into a convex spherical shape in advance, and then the optical fiber from which the tip coating has been removed is put into the ferrule with a photocurable adhesive. Inserting / fixing step, first polishing step for performing rough polishing on the ferrule fixed with the fiber with a wrapping film fixed with alumina, and second polishing step for performing finish polishing with a wrapping film fixed with cerium oxide. The process of and is included.

In the method of manufacturing the optical connector, the first
The polishing step and the second polishing step are performed dry or by using only water. Further, the glass material of the shaft portion of the ferrule is multi-component glass or quartz glass.

[0013]

According to the present invention, the ferrule itself is made economical by making the ferrule low-priced glass, and the ferrule and the fiber are made of materials having similar properties, so that the inexpensive cerium oxide is used in the polishing step. It enables the use of wrapping film and realizes economic efficiency without deteriorating the characteristics as a connector. It is considered that the same process can be performed with a ceramic ferrule by using silicon oxide as a film, but since ultrafine silicon oxide is much more expensive than alumina or cerium oxide, it was not suitable for forming a lapping film. In addition, by adopting a pre-dome ferrule, it is possible to reduce the waste of expensive diamond abrasive grains by collectively processing the convex spherical surface. Furthermore, by using a lapping film with a fixed abrasive, the work time required for polishing and cleaning during on-site assembly can be saved.
The photo-curing adhesive used in the present invention is very expensive as compared with the conventional two-component epoxy adhesive, but with the two-component epoxy, defoaming treatment for removing bubbles generated during mixing and heat are required. There are various problems such as the time required for curing and pot life, and it takes a lot of time to use, but only half a day can be used, whereas the photocurable adhesive used in the present invention can be immediately used for work and cured. The cost per connector is not so high because it is fast and can be used for about half a year if stored in the refrigerator after use.

[0014]

EXAMPLES Preferred examples for carrying out the present invention will be described below.

[Embodiment 1] FIGS. 1 to 3 are polishing process diagrams for explaining a ferrule polishing process according to a first embodiment of the present invention. 1 to 3, reference numeral 10 is a ferrule, 11 is a ferrule shaft portion, 12 is a ferrule collar portion, 13 is a plastic polishing film, and 14 is a plastic polishing film.
Is a fiber strand, 15 is a fiber core wire, 16 is a reference plane for fiber alignment, 17 is an alumina wrapping film, 18 is lens cleaning paper or cloth, 19 is a cerium oxide wrapping film, and 20 is an abrasive grain. Each is illustrated.

In this embodiment, the ferrule is a quartz glass ferrule whose shaft is made of quartz glass.
And SC type optical connector for communication (Japanese Industrial Standard: JIS C
5973F04 type single-fiber optical connector) is used to configure the connector.

The assembly process according to this embodiment will be described below in order. Process: The quartz glass ferrule 10 is pressed on an elastic plastic polishing film, which is the same method as the conventional manufacturing process, and is polished into a convex spherical shape using diamond abrasive grains 20 (see FIG. 1). Step: The abrasive grains 20 adhered with a cleaning liquid 21 such as water or alcohol are cleaned (see FIG. 1). Step: After filling the hole in the ferrule 10 with a photo-curing adhesive, the coating is removed and the cleaved fiber 14 with a predetermined strand length is inserted and irradiated with light to be hardened. At this time, it is preferable to irradiate the light while pressing the fiber 14 against the reference surface 16 so that the fiber 14 does not protrude much from the tip of the ferrule 10 (see FIG. 1). Step: A force (F) is applied at the collar portion 12 of the ferrule to crimp and hold the fiber core wire 15 (see FIG. 2). Step: Using the alumina wrapping film 17, the fiber 14 is roughly ground by dry grinding so that the fiber 14 coincides with the convex spherical surface of the ferrule (see FIG. 2). Process: Dry paper or cloth 18 for lens cleaning
Wipe the tip with to clean (see Fig. 2). Step: Water is added to the cerium oxide wrapping film 19 and finish polishing is performed by wet polishing (see FIG. 3). Process: Dry paper or cloth 18 for lens cleaning
Wipe the tip with to clean (see Fig. 3). The subsequent procedure for assembling the ferrule into the housing is conventional.

In the above process, the convex spherical surface polishing of the process and the ferrule 10 in the process can be collectively carried out at the time of manufacturing the ferrule in the factory, and it is already manufactured at present, and it is called a predome ferrule. . In addition,
Even with a normal ferrule with a flat end face, the end face is actually polished, so even if it is made into a convex spherical surface, the cost does not increase so much.

Even when this convex spherical surface polishing is carried out at a work site, it is more economical because a plurality of diamond abrasive grains which have been thrown away by the conventional manufacturing method can be repeatedly used when polishing a plurality of pieces. This is because there is no problem even if some dust is mixed in, because there is no fiber. When performing convex spherical surface processing in the field, if the dummy fiber is inserted so that the abrasive grains 20 do not enter the ferrule 10, cleaning of the process becomes easy.

As the photo-curing adhesive in the step, it is important to select one having a high glass transition temperature and a small linear expansion coefficient in order to enhance the stability after production. In this example, the glass transition temperature = 250 ° C., the linear expansion coefficient = 1.
A visible light curing type having a viscosity of 1 × 10 ⁻⁴ and a viscosity of 15,000 cps was used. If the viscosity is too high, it becomes difficult to insert the fiber. Therefore, it is preferable that the viscosity is not more than the above value. However, depending on the device such as a working jig, the viscosity exceeding the above range cannot always be used. Even if the adhesive is an ultraviolet curing type, there is no problem because the glass ferrule has a high translucency.

The fiber length of the fiber is 0.1 to
A length of about 1.5 mm is sufficient, and a fiber cutter for fusion splicing can achieve this degree of accuracy. When mass-producing in a factory, a plurality of pieces may be cut together and cut with a dicing saw or the like.

Reference plane 16 for process fiber alignment
Is preferably a material such as Teflon or polyethylene that is hard to attach an adhesive and transmits light, and when the ferrule 10 is pressed, the fiber is slightly (0.01 to 0.2).
It should be made so that it protrudes.

Process alumina lapping film 1
As No. 7, a particle size of 0.3 μm was used, and dry polishing was performed for about 1 minute with a polishing machine. Here, the particle size of alumina is 3μ
It is preferably m or less. This is because the ferrule may be scratched if a film having a large particle size or a silicon carbide film is used, which is not preferable.

In the present embodiment, the dry polishing is shown, but wet polishing may be performed by pouring water on the film. For example, when wet-polished with an alumina film having a particle size of 0.3 μm, a return loss of about 31 to 37 dB is obtained. Therefore, it can be used as it is if the application does not require a high return loss.

A cerium oxide lapping film having a particle size of 1 μm was used in the step, and wet-polished for several tens of seconds with a polishing machine. The water used was ordinary tap water, and the polishing time was short, so it was sufficient to run it first. Here, cerium oxide having a particle size of about 0.5 to 1 μm is widely used and is easily available. Further, if the particle size is outside the above range, the manufacturing cost is high, which is not preferable.

The polishing time is not necessarily the same as that in this embodiment, because the conditions vary depending on the polishing machine used.

Through the above steps, a connector having a return loss of 42 dB or more and having almost no drawing or protrusion of the fiber with respect to the ferrule (less than ± 50 nm) could be stably manufactured. By the way, when a conventional ferrule made of zirconia was polished in the same process, although the return loss could be secured at the same level, a fiber drawing amount of 200 nm was also generated, which is the standard of the current PC connector −50 to +100.
It was not possible to clear the nm standard.

As an optical connector for communication, an FC type optical connector (Japanese Industrial Standard: JIS C 5970 F01 type single core optical connector) is also widely used, but the ferrule shape is the same and this embodiment is the same. It can be used. The present embodiment is basically applicable to other optical connectors as long as the ferrule is built in.

[Embodiment 2] FIG. 4 is a diagram for explaining a second embodiment, in which reference numerals 10 to 21 are the same as those in FIG.
Reference numeral 22 indicates a silicon carbide wrapping film. In this embodiment, a "pre-dome ferrule" for SC type optical connector whose axis is made of multi-component glass is used as a ferrule for the purpose of further economy.

Further, in the present embodiment, it is assumed that the work is carried out at a site where there is no highly accurate fiber cutter. Hereinafter, the assembly process will be described in order. Step: After filling the hole in the ferrule 10 with a photo-curing adhesive, insert the fiber 14 with the coating removed for a long time,
Irradiate light to harden. Further, a slightly larger amount of adhesive is applied between the collar 12 of the ferrule and the core wire 15, and light is irradiated from above to cure the adhesive 23 and fix the fiber 14. Step: The tip portion of the fiber 14 that has been protruded is cut by a method of making a scratch with a ruby or a carbide blade and folding it. Step: The portion of the fiber 14 protruding by the silicon carbide wrapping film 22 is polished and dropped. Subsequent steps from step to step may be operated in the same manner as in Example 1, and the description thereof will be omitted.

In this embodiment, the fiber 1 is used in the process.
It is not necessary to grind 4 until it matches the ferrule 10. Rather, a slightly protruding state of the ferrule 14 will not damage the ferrule, so the finish will be clean. Similar polishing can be performed here by using a lapping film made of alumina or silicon oxide having a large grain size other than the silicon carbide lapping film 22. As for the material of the ferrule, the multi-component glass ferrule has a little difference in the physical properties from the fiber, but since it is closer to that of ceramic, there is no major problem. Further, when used under particularly severe temperature conditions, the ferrule made of quartz glass is superior, but the multi-component glass requires less temperature at the time of production, and thus can be expected to be more economical. Further, other than quartz glass, crystallized glass can be exemplified. As an example, the coefficient of linear expansion of multi-component glass is 3 to 5 × 10 ⁻⁶ / ° C., the coefficient of linear expansion of quartz glass is 0.5 × 10 ⁻⁶ / ° C., and the coefficient of linear expansion of zirconia is about 10 × 10 6. ^-6 / ° C.

[Third Embodiment] FIGS. 5 and 6 are views for explaining a third embodiment, and the reference numerals in the drawings are the same as those in the above-mentioned first and second embodiments. In addition, FIG.
6A to 6C show the steps 1 to 5, respectively, and
The same operation as above may be performed, and this embodiment is an example applied to a diagonal PC polishing connector having a slanted tip. In this case as well, a "pre-dome ferrule" is used, which is polished in a slanting convex spherical surface in advance.

The basic process is to tilt the ferrule with respect to the wrapping film (usually the ferrule axis is about 8
Except that the polishing is performed with an inclination of 10 ° to 10 °, the procedure is the same as in Examples 1 and 2, and the description thereof is omitted. The direction in which the ferrule is tilted with respect to the wrapping film has a key groove for aligning in the collar portion 12 of the ferrule, and therefore it may be aligned with that as a reference. The fiber is held by caulking, but it is of course possible to use an adhesive.

The oblique PC-polished connector has a feature that a high return loss is maintained even when the connector is opened, but if the center of the obliquely-polished convex spherical structure is not exactly aligned with the fiber. It is difficult to manufacture because it tends to show up as loss during connection and deterioration of temperature stability. Conventionally, after fixing the fiber and obliquely polishing, the eccentricity of the core and the convex spherical surface was measured and selected, but at present, the yield of oblique polishing is low, so the cost of fixing and polishing the fiber is multiple. The price was very high.

In this embodiment, the oblique polishing is collectively performed in the factory, and the eccentricity between the convex spherical surface and the shaft hole is measured and selected at that stage, thereby reducing the wasteful cost in yield. In this embodiment, almost only the fiber portion is polished even in the rough polishing, and this is possible because the shape of the ferrule is maintained.

[0036]

The present invention can greatly reduce the time and cost required for polishing. In particular, when considering the automation of connector polishing, the conventional manufacturing method using abrasive grains is likely to cause a failure due to clogging, etc., but in the present invention, the convex spherical surface polishing process using abrasive grains is intensively performed at the factory. Since only water is used in the process of attaching and polishing the fiber, it is suitable for automation, and it is easy to mass-produce, so further cost reduction can be expected.

A photo-curable adhesive is used for fixing the fiber, and problems such as the mixing of the epoxy adhesive, the elimination of defoaming processing time and the limitation of pot life are solved. By using a lapping film with a fixed abrasive, expensive abrasive grains are not used, and the time required for polishing and cleaning is greatly shortened to realize economic efficiency.

Further, by using a pre-dome ferrule, an optical connector with little reflection can be easily manufactured without using abrasive grains that tend to stain the surroundings. Therefore, in the laboratory, an optical fiber can be used as a connector on the spot for measurement. Suitable for

Similarly, the use of a predome ferrule eliminates the need for liquid management of abrasive grains, so repair work at the site, etc.
It is also advantageous when it is not used regularly. With a transparent glass ferrule, the injection status of the adhesive can be visually checked, so problems such as uneven adhesive and forgetting to apply the adhesive can be avoided.

Since the structure of the conventional optical connector plug is basically used as it is, there is no problem in terms of optical characteristics and compatibility.

[Brief description of drawings]

FIG. 1 is a polishing process diagram of processes for explaining a first embodiment of the present invention.

FIGS. 2A to 2D are views of a polishing process of processes for explaining the first embodiment of the present invention. FIGS.

FIG. 3 is a polishing step diagram of steps 1 to 3 explaining the first embodiment of the present invention.

FIG. 4 is a polishing process diagram of processes to explain a second embodiment of the present invention.

FIG. 5 is a polishing process diagram of processes to explain the third embodiment of the present invention.

FIGS. 6A to 6C are views of polishing steps of steps for explaining the third embodiment of the present invention. FIGS.

[Explanation of symbols]

 10 ferrule 11 ferrule shaft portion 12 ferrule collar portion 13 plastic polishing film 14 fiber element wire 15 fiber core wire 16 fiber alignment reference plane 17 alumina wrapping film 18 lens cleaner paper or cloth 19 cerium oxide wrapping film 20 Abrasive Grain 21 Cleaning Liquid 22 Silicon Carbide Lapping Film 23 Adhesive

Claims (3)

[Claims] 1. A method for manufacturing an optical connector in which an optical fiber is inserted into a ferrule and the optical axes are aligned by aligning the ferrules with each other, wherein the shaft portion of the ferrule is made of a glass material. The step of polishing the ferrule tip into a convex spherical shape in advance, the step of inserting and fixing the optical fiber from which the tip coating has been removed into the ferrule with a photo-curing adhesive, and the fiber-fixed ferrule. On the other hand, the optical connector is characterized by including a first polishing step of performing rough polishing with a lapping film with a fixed alumina and a second step of performing final polishing with a lapping film with a fixed cerium oxide. Production method. 2. The method for manufacturing an optical connector according to claim 1, wherein the first polishing step and the second polishing step are performed dry or by using only water. 3. The method for manufacturing an optical connector according to claim 1, wherein the glass material of the shaft portion of the ferrule is multi-component glass or quartz glass.