JPH1164671A - Glass capillary tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to exactly position and fix plural pieces of optical fibers adjacent to each other by providing a glass capillary tube having insertion holes which have an approximately square shape in section and are inserted with plural pieces of the adjacent optical fibers and forming the tube in such a manner that the spacings of the inside wall surfaces facing each other of the insertion holes and the diameter of the optical fibers satisfy a specific relation. SOLUTION: The glass capillary tube 1 has the insertion holes 2 which have the approximately square shape in section and are inserted with two pieces of the adjacent optical fibers 5, 6. The spacing L of the inside wall surfaces facing each other of the insertion holes 2 and the diameter D of the optical fibers 5, 6 to be inserted are so determined as to satisfy the relation (1+2<(n-2)/2> )D<L<=(1.05+2<(n-2)/2> )D (where, (n) is an integer of >=1). As a result, two pieces of the optical fibers 5, 6 do not induce kinks and misalignment in rotation and the holding, positioning and fixing of the adjacent optical fibers 5, 6 with high accuracy are made possible when two pieces of the optical fibers 5, 6 are inserted into the glass capillary tube 1. The rear surface of the glass capillary tube 1 is provided with a flare part 3 for guiding the optical fibers 5, 6 into the insertion holes 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass capillary for holding, positioning and fixing a plurality of optical fibers adjacent to each other accurately.

[0002]

2. Description of the Related Art Conventionally, when a signal transmitted through one optical fiber is split into a plurality of optical fibers, or when a signal from a plurality of optical fibers is multiplexed into a single optical fiber. , A capillary tube for holding and fixing a plurality of optical fibers is used. For example, when two optical fibers are accurately held in parallel, positioned and fixed, as shown in FIG. 5, a capillary tube 1 having a circular cross-section insertion hole 2 into which the two optical fibers 5 and 6 are inserted is used. Is done.

The inner diameter of the insertion hole 2 of the capillary tube 1 is, for example, a gap of 1 to 5 μm for a quartz optical fiber having a diameter of 125 μm so that high positioning accuracy of the two optical fibers 5 and 6 to be inserted can be achieved. Is manufactured with high accuracy.

[0004]

However, since the insertion hole 2 of the capillary 1 has a circular cross section, the two optical fibers 5 and 6 are twisted in the insertion hole 2 as shown in FIG. In this case, the central axis P of the insertion hole 2 and the optical axis 5b of the optical fiber 5 and the optical axis 6b of the optical fiber 6 have angles Δθ1 and Δθ2, respectively.
Are not parallel to the central axis P, and the optical fibers 5, 6
Of the optical axes 5b and 6b are spread at an angle of Δθ1 + Δθ2. That is, the optical elements such as the light emitting element, the light receiving element, the waveguide element, and the optical fiber arranged with respect to the twisted optical fibers 5 and 6 and the optical fibers 5 and 6 arranged in parallel with the central axis P are as follows. There is a problem that the relative position becomes incompatible and connection loss increases.

Further, as shown by the broken line and the movement angle Δθ3 in FIG. 5B, the two optical fibers are rotationally shifted in the insertion hole 2 and the optical fibers corresponding to the optical fibers 5 and 6 are not rotated. The relative position needs to be adjusted. Some optical fibers have a small diameter of 5 μm to 10 μm, which is called a single mode fiber, through which an optical signal passes, and there is a problem that the operation of adjusting the relative position is extremely difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a glass capillary capable of accurately holding, positioning, and fixing a plurality of optical fibers adjacent to each other and solving the above-mentioned conventional problems.

[0007]

The glass capillary tube according to the present invention has a substantially square cross section and has an insertion hole for inserting a plurality of adjacent optical fibers having a diameter D. The distance L between the facing inner wall surfaces and the diameter D of the inserted optical fiber are (1 + 2 ^{(n-2) / 2} ) D <L≤ (1.05
+2 ^{(n-2) / 2} ) D (where n is an integer of 1 or more).

For example, as shown in FIG.
The distance L between opposing inner wall surfaces of a substantially square insertion hole for holding two adjacent optical fibers having no clearance
And the diameter D are represented by L = (1 + 2 ^{(1-2) / 2} ) D, that is, L = (1 + 1 / Ｄ2) D. Since a clearance is required to insert two optical fibers, the interval L between the insertion holes must satisfy the condition of (1 + 1 / √2) D <L. In the case of a single mode optical fiber, the ratio of the diameter of the core through which the optical signal passes to the diameter D is 5
Since the positioning accuracy of the two optical fibers is within at least about 5% of the optical fiber diameter D, the distance L satisfies the relationship of L ≦ (1.05 + 1 / √2) D. There is a need. Actually, 1 + 1 / √2 ≒ 1.71 and 1.05 + 1 / √2 ≒ 1.76 (1.7
1) It is necessary to satisfy the relationship of D <L ≦ (1.76) D.

The fact that the insertion hole of the glass capillary of the present invention has a substantially square cross section will be described. Generally, when a glass tube is stretched by heating glass, a compressive stress is generated on an outer surface of the glass tube, and a tensile stress is generated on an inner surface of the glass tube. Since glass breaks at the point where the tensile stress is maximized, usually
The shape should be as round as possible so as not to form an angular shape where tensile stress is concentrated on the inner surface. The cross-sectional shape of the insertion hole of the glass capillary of the present invention is rounded at the corners and made substantially square near a circle, so that tensile stress is prevented from being concentrated on the inner surface of the glass capillary, and strength is secured. Things.

Further, the glass capillary tube of the present invention is characterized in that at least one opening end of the insertion hole is formed with a flare portion which smoothly continues to the insertion hole.

[0011]

The glass capillary tube of the present invention has a substantially square cross section and has insertion holes into which a plurality of adjacent optical fibers having a diameter D are inserted, and a gap L between opposing inner wall surfaces of the insertion holes. And the diameter D of the optical fiber to be inserted is (1 + 2)
^{Since (n-2) / 2} ) D <L≤ (1.05 + 2 ^{(n-2) / 2} ) D (where n is an integer of 1 or more), a plurality of optical fibers are inserted into the glass capillary. In this case, the plurality of optical fibers do not twist or rotate, and the adjacent optical fibers can be held, positioned and fixed with high accuracy.

Further, according to the glass capillary in which the flare portion is formed smoothly in the insertion hole, a plurality of optical fibers can be easily inserted adjacent to the substantially square insertion hole.

[0013]

FIG. 1 is an explanatory view of a glass capillary according to the present invention, wherein 1 is a glass capillary, 2 is an optical fiber insertion hole, and 3 is an optical fiber guiding hole. Flare section, 5 and 6 are optical fibers, 9 is adhesive, 1
Reference numeral 0 denotes each connector plug, and the same parts as those in FIG. 5 described above are denoted by the same reference numerals.

The glass capillary of the present invention has an expansion coefficient of 5.
It is made of borosilicate glass of 2 × 10 ⁻⁶ / ° C., has a substantially tubular shape, an outer diameter of 1.14 mm ± 0.001 mm, and has a high roundness. It has a substantially square shape and a plurality of pieces having a diameter D, for example, as shown in FIG.
The distance L between the opposing inner wall surfaces of the insertion hole 2 into which the adjacent optical fibers 5 and 6 are inserted and the diameter D of the inserted optical fiber are (1 + 2 ^{(n-2) / 2} ) D <L ≦ (1.05 + 2
^{(n-2) / 2} ) D (where n = 1), that is, (1.71) D
When two optical fibers having a diameter D of 125 μm are held so as to satisfy the relationship of <L ≦ (1.76) D, the insertion hole 2
The distance L between the opposing inner wall surfaces is 215 μm ± 1 μm, so that the exposed end face of the optical fiber can be accurately positioned and held in the glass capillary tube 1. On the rear end surface 1b of the glass capillary tube 1, a substantially conical flare portion 3 having an opening diameter of about 1 mm for guiding the optical fibers 5 and 6 to the insertion hole 2 is provided.

As a material for forming the glass capillary 1, borosilicate glass, lithium-alumina-silicate glass ceramics, or the like can be used. The expansion coefficient of the material is preferably as low as 1 × 10 ⁻⁵ / ° C. or less when the optical fiber to be held is a silica-based optical fiber having a low expansion coefficient.

When the above-mentioned glass capillary tube 1 is manufactured, the inner surface of the heated glass tube is evacuated to vacuum and the mold is brought into close contact with a mold, or two glass members provided with concave grooves are welded and bonded. A preformed body having a substantially square hole is produced by a method or the like, and the preformed body is heated and stretched and formed into a capillary having an insertion hole 2 with a desired high dimensional accuracy while controlling to a predetermined cross-sectional dimension and shape. . The obtained long capillary is cut into a predetermined length, and a flare portion 3 is provided at one end thereof by a chemical etching method or the like, thereby producing a glass capillary 1.

The glass capillary tube 1 obtained as described above
2 shows an example in which two adjacent optical fibers are positioned by using. As shown in FIG. 1, two single mode fibers 5 and 6 are inserted from a flare portion 3 into an insertion hole 2 of a glass capillary tube 1.
Are inserted adjacent to each other, and fixed with an epoxy resin adhesive 9,
After removing the optical fiber protruding from the end face 1a, the end face 1a was polished by a known method to produce a connector plug 10.

Next, as shown in FIG. 2, two optical fibers 7 and 8 are similarly fixed to the glass capillary tube 1 to form a connector plug 11, and a refractive index matching material 12 is attached to both butted end faces. Is applied, and the outer diameter of the glass capillary 1 is 1 μm.
The inner hole 1 of the glass sleeve 13 having an inner diameter larger by m
3a was inserted from both sides, and held so that the contact between the end faces 1a butted by an appropriate means using a pressing spring or the like was maintained. The connection loss values when the connector plugs 10 and 11 are rotated relative to each other while monitoring the intensity of the signal light to the optical fibers 5 to 7 and set to the optimum positions for connection are both optical fibers 5 to 7 and 6 to 8 0.3dB
It was below.

Before cutting a long capillary obtained by stretching the preform into a predetermined length, a linear marker 14 is inserted into the insertion hole 2 as shown in FIG. It was provided on the outer surface of the glass capillary tube 1 in parallel with the central axis, and then cut to provide the flare portion 3 to form a pair of glass capillary tubes 1 and 1 '. Using the pair of glass capillaries 1 and 1 ′, two connector plugs 10 and 11 were prepared in the same manner as described above, and FIG.
As shown in FIG. Instead of confirming the connection loss of light from the optical fibers 5 to 7 or 6 to 8, the connector plug 1 is set so that the position of the marker 14 previously provided under the microscope is straight as shown in FIG.
0 and 11 were rotated and positioned. The connection loss value of the optical fiber obtained in this way is
It was confirmed that the connector plugs 10 and 11 could be set at the optimal positions for connection without monitoring the optical signal, in both cases 6 to 8 being 0.3 dB or less.

FIG. 3 shows another embodiment according to the present invention. The cross section is substantially square (1.71) D <L
In order to satisfy the relationship of ≦ (1.76) D, there is an insertion hole 2 in which the distance L between the inner wall surfaces facing the diameter D125 μm of the two optical fibers is 215 μm ± 1 μm, and flared portions at both ends. A glass capillary 1 provided with 3 is prepared. The refractive index matching material 12 is previously inserted into the insertion hole 2 of the glass capillary 1.
And four single-mode optical fibers 5, 6, 7, 8 having end faces cleaved and cut from the flared portions 3 at both ends.
Among them, the optical fibers 5 and 7, and 6 and 8 were inserted so as to abut each other, and held so that the contact between the butted end faces was maintained. When inserting the optical fiber, the extra refractive index matching material 12 is inserted into the substantially square insertion hole 2 and the optical fibers 5, 6,.
Since the optical fibers 5, 6, 7, 8 are discharged outside through the gaps between the end faces 7, 8, there is no difficulty in inserting the optical fibers 5, 6, 7, 8 and no bubbles are interposed at the contact interface between the end faces. At this time, the connection loss of each of the optical fibers 5 to 7 and 6 to 8 is 0.3 d.
Good connections below B were achieved. By using the glass capillary tube 1 provided with the flare portions 3 at both ends of the present embodiment, the optical axes of the respective optical fibers can be accurately aligned only by opposing and abutting the two optical fibers in the insertion hole 2. , Confirmed that a high-grade connection can be achieved immediately.

As described above, the glass capillary tube 1 of the present embodiment maintains the relative position of the core portions 5a because two adjacent optical fibers do not twist or rotate in the insertion hole 2. It can be accurately and easily positioned at a predetermined adjacent position.

In the above embodiment, the case where two adjacent optical fibers are connected has been described. However, the present invention is not limited to this. As shown in FIGS. Are stable in the insertion hole having a substantially square cross section (n =
2) 5 (n = 3), 9 (n = 4), 13 (n =
5) etc., any glass capillary tube into which a plurality of adjacent optical fibers can be inserted may be used.

[0023]

According to the glass capillary tube of the present invention, an excellent effect that a plurality of adjacent optical fibers can be easily positioned and held at accurate adjacent positions can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a glass capillary of the present invention,
(A) is a perspective view, (B) is an end view

FIG. 2 is an explanatory view of an example of use of the glass capillary of the present invention.

FIG. 3 is an explanatory view showing another embodiment of the present invention.

FIG. 4 is an explanatory view showing another glass capillary tube of the present invention.

5A and 5B are explanatory views of a conventional capillary tube, wherein FIG. 5A is a perspective view and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capillary tube 2 Insertion hole 3 Flare part 5, 6, 7, 8 Optical fiber 9 Adhesive 10, 11 Connector plug 12 Refractive index matching agent 13 Sleeve 14 Marker

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaki Wada 2-7-1 Hararashi, Otsu City, Shiga Prefecture Nippon Electric Glass Co., Ltd.

Claims (2)

[Claims] 1. A cross section having a substantially square shape and having an insertion hole for inserting a plurality of adjacent optical fibers having a diameter D,
The distance L between the opposed inner wall surfaces of the insertion hole and the diameter D of the inserted optical fiber are (1 + 2 ^{(n-2) / 2} ) D <L ≦
(1.05 + 2 ^{(n-2) / 2} ) A glass capillary tube satisfying the relationship of D (where n is an integer of 1 or more). 2. The glass capillary tube according to claim 1, wherein a flare portion smoothly connected to the insertion hole is formed at at least one opening end of the insertion hole.