JPH0915449A - Ferrule for optical connector - Google Patents

Abstract

PURPOSE: To obviate the occurrence of peeling of adhesion between the outer peripheral surface of a ferrule and a spring mounting member and the fracture of an optical fiber in the ferrule by specifying the surface roughness of the spring material part of the outer peripheral surface of the ferrule to a specific surface. CONSTITUTION: The joint part of the front end face 11 of the ferrule and the outer peripheral part 13 is provided with a sleeve insertion guide 14 and a through-hole 12 is formed in the central axial direction of the ferrule arriving at the rear end face 15 formed with a conical fiber insertion guide 16 from the front end face 11. Further, the surface roughness Ra of the outer peripheral surface is in a range of 0.1<Ra<25 and is specified to the relatively rough surface. The sizes of the ferrule are generally outside diameter D=ϕ2.5mm, length L=10.5mm, through-hole d=ϕ0.126mm diameter. The reason for making the surface roughness of the outer pheripheral surface Ra of the ferrule rougher than 0.1 lies in that the joint area at the time of adhering the surface to the spring mounting part is increased and the joint strength is increased by forming the outer peripheral surface as the rough surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrule for an optical connector used for optical communication and for connecting optical fibers to each other.

[0002]

2. Description of the Related Art Conventionally, a ferrule for an optical connector has been used with its rear end fixed to a spring mounting member. Fixing methods include press-fitting, bonding, insert molding, etc., but when pulling out the optical plug incorporating the ferrule for the optical connector from the optical adapter incorporating the split sleeve, between the spring attachment part and the ferrule for the optical connector. Since 300-600 grams of force is applied to
Considering the safety factor, it has been said that the fixed strength of the ferrule for the optical connector and the spring mounting portion should be 10 kg or more in the product on the actual transaction.

In the case of adhesive fixing among the above fixing methods, since the surface roughness of the adhesive surface is too small, the bonding strength is insufficient, and the adhesive peels between the outer peripheral surface of the ferrule and the ferrule mounting surface of the spring mounting portion. Occasionally, the optical fiber inside the ferrule may break when the optical plug is attached or detached, which may cause a serious problem because optical transmission, which is an important characteristic of the optical fiber connector, becomes impossible.

Incidentally, the ferrule for optical connector is manufactured by JI
The standard is described at the location of the F04 type single-fiber optical fiber connector (commonly called SC ferrule) of SC5973, but the surface roughness of the outer peripheral surface is not specified. However, the product on the actual transaction had a surface roughness of Ra 0.01 or less.

The reason why the surface roughness is reduced in this way is as follows. It was thought that when the surface roughness became large, the insertion loss became large when it was put into the split sleeve.
In addition to this, it is thought that the appearance requirements of each company became stricter because the ferrule manufacturing → connector company → → device maker → telephone company were delivered in the industry. And, whether it is insertion loss or appearance requirements, it was an excessive specification produced by such a system in the industry.

[0006]

In view of the above, the present invention provides
The surface roughness of the outer peripheral surface of the ferrule for optical connector is 0.1 <R
It was set to a <25.

[0007]

In the ferrule for an optical connector of the present invention constructed as described above, since the surface roughness of the outer peripheral surface is Ra> 0.1, the area of the joint surface with the spring mounting portion becomes large, and the adhesive agent The fixing force is significantly increased. Further, since the surface roughness of the outer peripheral surface is Ra <25, the adhesive wraps around the outer peripheral surface of the ferrule evenly. When the surface roughness is greater than Ra25, the surface becomes a rough surface of ▽ finishing or less. As a result, the surface is too rough, and the adhesive agent does not sufficiently wrap around to form an air layer.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view of a ferrule for an optical fiber connector (hereinafter, abbreviated as ferrule) F according to an embodiment of the present invention.
A sleeve insertion guide 14 is provided at a connecting portion between the ferrule front end surface 11 and the outer peripheral portion 13, and a through hole 12 extends from the front end surface 11 to a rear end surface 15 where a conical fiber insertion guide 16 is formed in the central axis direction of the ferrule F. Are formed. Further, the surface roughness of the outer peripheral surface is in the range of 0.1 <Ra <25, and is relatively rough.

As the size of the ferrule F, the outer diameter D
= Φ2.5 mm, length L = 10.5 mm, through hole d = φ
The most common one is 0.126 mm, and the material is ceramics such as zirconia and alumina, glass,
Plastic, metal, etc. are applicable. Further, as the material of the spring mounting portion 2, ceramics, glass, plastic, metal or the like can be applied.

The reason why the surface roughness of the outer peripheral surface of the ferrule F constructed as described above is rougher than Ra0.1 is that the outer peripheral surface is made relatively rough so that it is bonded and fixed to the spring mounting portion 2. The bonding area with the adhesive increases,
This significantly increases the bonding strength. By increasing the length of the ferrule fitting portion 21 of the spring mounting member 2, the joint area with the adhesive can also be increased and the joint strength can be increased when the adhesive fixing is performed similarly. Since the length from the end surface 23 of the spring mounting member 2 to the ferrule tip surface 11 is normally specified as 7.95 to 8.00, the total length of the ferrule 1 must be increased. However, if the total length of the ferrule 1 is increased, the cost for producing the ferrule 1 will increase.

As described above, by making the surface roughness of the outer circumference rougher than Ra0.1, the spring mounting portion 2 is adhered to the ferrule with the adhesive 3, and then the optical fiber is adhered to the housing and the spring. The outer peripheral surface 1 of the ferrule is assembled even after repeated assembly and removal with an optical plug equipped with rubber boots, etc. and an optical connector equipped with a split sleeve.
Adhesive peeling occurred between the ferrule mounting surface 21 of the ferrule 1 and the ferrule mounting surface 21 of the spring mounting portion, and the optical fiber inside the ferrule 1 did not break when the optical plug was attached and detached.

Furthermore, by making the surface roughness of the outer peripheral surface rougher than Ra0.1, it is possible to finish only by the grinding step without the conventional time-consuming outer peripheral polishing step, so that the manufacturing cost is greatly reduced. We were able to.

Next, the reason for setting the surface roughness of the outer peripheral surface of the ferrule F to Ra <25 is as follows. That is, if the surface roughness of the outer peripheral surface is Ra <25, the adhesive wraps around the outer peripheral surface of the ferrule evenly, but if the surface roughness is greater than Ra25, the surface is too rough and the adhesive agent is not sufficient. An air layer is created without turning around.

In order to confirm the effectiveness of the present invention, several ferrules F each having an outer peripheral surface within the above-mentioned surface roughness range were produced, and these ferrules F were used at -40 to + 85 ° C. for 1 cycle and 500 cycles for 1 hour. After performing the thermal shock test, a desorption test was performed, but the optical fiber inside the ferrule 1 was not broken.

FIG. 2 is a sectional view of a ferrule F showing another embodiment of the present invention, and the same members as those in FIG. 1 are designated by the same reference numerals.

This ferrule F is the ferrule F of FIG.
The end surface diameter of the tip surface 11 of the
An adhesive pool 22 is provided on the end of the spring mounting portion 2 so that the adhesive 3 does not protrude from the end surface 23 of the spring mounting portion 2.
The performance was not inferior to that of the ferrule F of FIG.

Experimental Example 1 An experiment was conducted by the method described below. The zirconia ferrule has an outer diameter D = φ2.5 mm, a length L = 10.5 mm, a through hole d = φ0.126 mm, and a surface roughness Ra0.00.
5, 0.08, 0.11, 0.25, 0.50 samples were made, and the metal spring mounting part 2 was fixed to the rear part of each with the epoxy adhesive 3 and then the spring mounting part rear end. Then, a load T was applied to the ferrule 1 from the rear through the cemented carbide pin 4 as shown in FIG. Table 1 shows the results.

[0018]

[Table 1]

As shown in Table 1, as the surface roughness of the outer peripheral surface becomes rougher, the average load becomes larger and the variation becomes smaller.

Statisticalally, (average value) ± 3 × (variation)
Outside the range of 0.3%, 0.3% out of specification occurs. As a result of this experiment, a bonding strength of 10 kg or more was confirmed with a surface roughness rougher than Ra 0.11.

Experimental Example 2 Zirconia ferrule outer diameter D = φ2.5 mm, length L
= 10.5 mm, through-hole d = φ0.126 mm, and the surface roughness of the outer peripheral surface of each sample of Ra10, 20, 30 is made,
After fixing the metal spring mounting portion 2 to each rear portion with the epoxy adhesive 3, the load when the ferrule 1 slips out of the spring mounting portion 2 was measured as in Experimental Example 1. Table 2 shows the results.

[0022]

[Table 2]

As is clear from Table 2, the surface roughness is R
When it was larger than a25, the load when the ferrule 1 slipped out became small. As a reason for this, it was confirmed that the surface of the ferrule 1 was too rough, and the adhesive layer did not sufficiently circulate and an air layer was generated.

[0024]

As described above, according to the present invention, in a substantially cylindrical ferrule for an optical connector having an axial through hole for accommodating an optical fiber, at least a spring is attached to the outer peripheral surface of the ferrule. The surface roughness of the part is Ra0.1
By using a ferrule structure for an optical fiber connector with a rougher surface, the ferrule is bonded and fixed to a spring mounting member, and then the optical fiber is bonded and assembled into an optical plug equipped with a housing, spring, rubber boot, etc. Even after repeated insertion and extraction in the optical connector equipped with a split sleeve, adhesive peeling may occur between the outer peripheral surface of the ferrule and the spring mounting member, or the optical fiber inside the ferrule may break when the optical plug is removed. Absent.

Further, since the polishing step can be omitted and the finishing step can be completed only by the grinding step, the manufacturing cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a ferrule for an optical connector according to an embodiment of the present invention with a spring mounting portion fixed.

FIG. 2 is a cross-sectional view showing a ferrule for an optical connector according to another embodiment of the present invention, in which a spring mounting portion is fixed.

FIG. 3 is a schematic diagram showing a method for measuring the joint strength between the ferrule for an optical connector and the spring mounting portion of the present invention.

[Explanation of symbols]

 1 Ferrule 2 Spring Attachment Member 3 Adhesive 4 Carbide Pin 11 Tip Surface 12 Through Hole 13 Outer Circumference 14 Sleeve Insertion Guide 15 Rear End Face 16 Optical Fiber Insertion Guide 21 Ferrule Fitting 22 Adhesive Reservoir 23 End Face

Claims (1)

[Claims] 1. A substantially cylindrical ferrule for an optical connector having a through hole for accommodating an optical fiber in an axial direction,
A ferrule for an optical connector, characterized in that the outer peripheral surface of the ferrule has a surface roughness of 0.1 <Ra <25.