JPH0743547A - Optical fiber connection method - Google Patents

Abstract

(57) [Abstract] [Object] The present invention relates to an improvement in a method for permanently splicing optical fibers. [Structure] Two optical fibers 1a and 1b to be connected are inserted from both ends of a pipe 2 having an inner diameter slightly larger than the outer diameter of the strand, and a photo-curable adhesive 3 introduced in advance is sandwiched inside the pipe. Optical fiber 1
Light of a wavelength that does not react with the adhesive 3 is incident from one end of a,
The fiber holding stage 4 ′ performs centering so that the intensity received by the power meter 8 at the other end becomes maximum, and thereafter, light having a wavelength that cures the adhesive 3 is made incident from one end of the optical fiber 1 a to form a bonding surface. Of the optical fiber 1a, by irradiating light from outside the pipe 2
This is a method of curing the adhesive 3 between 1b and the pipe 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method of permanently splicing optical fibers.

[0002]

2. Description of the Related Art A conventional method for permanently splicing optical fibers is to connect them as shown in FIG.
Insert the optical fibers 1a and 1b of the book from both ends of the pipe 2 having an inner diameter slightly larger than the outer diameter of the strand, and sandwich the ultraviolet curing adhesive 3'previously inserted in the pipe from both sides. After the two optical fibers 1a and 1b are pressure-contacted with each other, an ultraviolet ray is transmitted from one end of the optical fiber 1a or 1b to cure the adhesive (Japanese Unexamined Patent Publication No. 56-25708).

[0003]

The above-mentioned conventional method has been widely used since the beginning because the connecting means is simple.
A small gap between the inner diameter of the pipe and the outer diameter of the optical fiber has been a problem when the core diameter is small and the axis alignment with high accuracy is required like the mode fiber. The present invention is an optical fiber connection method that solves such problems.

[0004]

According to a first connection method of the present invention, two optical fibers to be connected are inserted from both ends of a pipe having an inner diameter slightly larger than the outer diameter of the strand, and The two optical fibers are joined so as to sandwich the photo-curing adhesive introduced in advance inside, and then light having a wavelength that does not react with the adhesive is incident from one end of the optical fiber and received at the other end to receive the light. The joint is aligned so that the strength is maximized, and then the adhesive at the joint surface is first cured by the incidence of light of a wavelength that cures the adhesive from one end of the optical fiber, then the outside of the pipe. It is characterized in that the adhesive between the optical fiber and the pipe is cured by irradiating light from.

In the second connection method according to the present invention, the two optical fibers to be connected are inserted from both ends of a pipe having an inner diameter slightly larger than the outer diameter of the strand, and the optical fiber introduced in advance inside the pipe. The two optical fibers are joined so as to sandwich the curing adhesive, and then light having a wavelength that does not react with the adhesive is irradiated from the cross-sectional direction of the pipe, and the transmitted light is image-processed to align the core or the clad. After that, light with a wavelength that cures the adhesive is injected from one end of the optical fiber to cure the adhesive on the joint surface, and then light is irradiated from the outside of the pipe to bond the optical fiber and the pipe. It is characterized in that the agent is cured.

In the above invention, first, the light of the core waveguide mode is incident to cure the adhesive in the central portion of the optical fiber joint surface, and then the light of the clad waveguide mode is incident to the optical fiber joint surface. It is characterized in that the adhesive in the peripheral portion of is cured.

The adhesive in the above invention is equal to the refractive index of the core, or is larger than the core of the low refractive index fiber and smaller than the core of the high refractive index fiber when the two optical fibers are different from each other. Characterize.

Further, when the linear expansion coefficient of the adhesive in the above invention is equal to the linear expansion coefficient of the optical fiber, or when the two optical fibers are different from each other, it is larger than the low expansion coefficient fiber and higher than the high expansion coefficient fiber. Characterized by being small.

[0009]

According to the above construction, the method of the present invention realizes a highly accurate splice because the fiber to be connected is inserted from both ends of the pipe, and after the centering, the adhesive is cured and integrated. It is effective when applied to SM fiber connection. Also, after alignment, since the adhesive is cured from the center of the joint of the fiber to be connected to the outer periphery,
It is possible to prevent axial misalignment due to strain force when the adhesive cures.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. FIG. 1 is a schematic diagram showing a configuration relating to the connection method of the first embodiment, in which two connected optical fibers 1a and 1b having a resin coating around an optical fiber element wire 1'made of glass and a pipe. 2 is a fiber fixing stage 4 and a fiber holding stage 4 respectively
′, The pipe fixing stages 6, 6 are positioned with high precision. The fiber holding stage 4'is connected to the drive motor 5 and is provided so as to be movable in the XYZ directions with submicron accuracy. Further, one end of each of the optical fibers 1a and 1b is connected to a light source 7 whose wavelength can be switched, and the other end is connected to a power meter 8. The power meter 8 is connected to a stage control circuit 9 and a fiber is gripped via a drive motor 5. It is connected to the stage 4 '.

The connection method according to the structure of the present invention comprises an aligning step and a fixing step. In the centering step, after filling the inside of the pipe 2 with a photo-curable adhesive that reacts only with light of a certain wavelength, the fibers 1a and 1b to be connected are inserted from both ends of the pipe 2 and abutted. Next, light having a wavelength that does not react with the adhesive is incident from one end of the optical fiber 1, and the light receiving level is monitored by the power meter 8 at the other end of the optical fiber. The received light power is sent to the control circuit 9, and the optical axis of the optical fiber is centered by the drive motor 5 in the X and Y directions so that the received light power becomes maximum.

On the other hand, in the fixing process, after the alignment process is completed, the light source 7
Is switched to a wavelength that reacts with the adhesive 3 and this light is incident from the end face of the core to transmit the light of the core waveguide mode, and the adhesive of the end face core portion of the optical fiber is selectively cured. Next, the light of the clad waveguide mode is transmitted by being incident from the side surface of the optical fiber, and the adhesive in the end clad portion of the optical fiber is selectively cured. Finally, from the outside of the pipe 2, the light irradiation device 1
0 cures the adhesive between the outer circumference of the cladding and the inner surface of the pipe. In this way, since the adhesive around the center of the optical fiber is cured in order, the axial displacement due to the stress generated in the curing process can be minimized.

Since the adhesive on the end faces of the fibers 1a and 1b to be connected forms a part of the optical transmission medium, if the refractive index of the optical fiber core is equal to or the two optical fibers are different from each other, the low refractive index fiber is used. Is larger than the core of the high refractive index fiber and smaller than that of the high refractive index fiber. Further, since the optical fibers 1a and 1b and the pipe 2 are integrated after being connected, when the linear expansion coefficient of the adhesive is equal to the linear expansion coefficient of the connected fiber or the two optical fibers are different from each other. It is preferably larger than the low expansion coefficient fiber and smaller than the high expansion coefficient fiber.

Next, the connection process of this embodiment will be described more specifically. The center of a glass pipe 2 having an inner diameter of 127 μm is filled with Daikin's Optodyne: UV curable adhesive 3, and a quartz fiber 1b having a core outer diameter of 4 μm and a cladding outer diameter of 125 μm and a fluoride fiber 1a are inserted from both ends of the pipe 2. And then matched. At this time, when light with a wavelength of 1.31 μm was incident from the fluoride fiber 1a side by the light source 7 and the received light power was monitored by the power meter 8 on the quartz fiber 1b side, the butt loss was 2.1 dB. After that, while monitoring the received light power, the control circuit 9 axially adjusted the fiber holding stage 4'in the X and Y directions via the drive motor 5 so that the input was maximized, and the loss decreased to 0.18 dB. In this state, the light source 7 is switched to a wavelength of 0.34 μm, this light is made incident on the core of the optical fiber 1a to cure the adhesive in the core portion in the joint portion, and then the light is made incident on the cladding layer to make the cladding portion. Then, the adhesive between the inner periphery of the pipe 2 and the outer periphery of the clad was cured by applying light having a wavelength of 0.34 μm from the outside of the pipe 2 in the cross-sectional direction by the light irradiation device 10. The connection loss at this time was 0.20 dB.

FIG. 2 is a schematic diagram showing the configuration of another embodiment relating to the connection method of the present invention, and the same elements as those in FIG. 1 are designated by the same reference numerals. To adjust the axes of the optical fibers 1a and 1b, an illumination 13 is applied from the cross-sectional direction of the pipe 2, the transmitted light passes through a microscope camera 11, and an image processing device 12 causes an axial deviation of the outer diameter of the core or the clad of the optical fibers 1a and 1b. To calculate. Then, this axis deviation is adjusted by the control circuit 9 via the drive motor 5 so as to be minimized. The fixing step is performed in the same manner as in the above embodiment.

[0016]

As described above, according to the present invention, the fiber to be connected is inserted from both ends of the pipe, and after the alignment, the adhesive is cured and integrated, so that the splice is highly accurate and the loss is low. It is effective when applied to the required SM fiber connection. Also, after alignment, since the adhesive is cured from the center of the joint of the fiber to be connected to the outer periphery,
It is possible to prevent axial misalignment due to strain force when the adhesive cures.

[0017]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration relating to a connection method of a first invention.

FIG. 2 is a schematic diagram showing a configuration relating to a connection method of the second invention.

FIG. 3 is a partially broken side view for explaining a conventional connection method.

[Explanation of symbols]

 1a, 1b: Optical fiber 1 ': Optical fiber element wire 2: Pipe 3, 3': Adhesive 4: Fiber fixing stage 4 ': Fiber gripping stage 5: Drive motor 6: Pipe fixing stage 7: Light source 8: Power meter 9: Control circuit 10: Light irradiation device 11: Camera 12: Image processing device 13: Lighting

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Nakazato 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Masataka Nakazawa 1-6, Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corp. (72) Inventor Yoshiaki Miyajima 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corp.

Claims (7)

[Claims] 1. Two optical fibers to be connected are inserted from both ends of a pipe having an inner diameter slightly larger than the outer diameter of the strand, and the photocurable adhesive previously introduced into the pipe is sandwiched between the two optical fibers. The optical fibers are joined together, then light with a wavelength that does not react with the adhesive is incident from one end of the optical fiber, and the other end is received to align the joint so that the intensity of the light is maximized. , The light of the wavelength that cures the adhesive is injected from one end of the optical fiber to cure the adhesive on the bonding surface,
Then, a method of connecting the optical fibers is characterized by irradiating light from the outside of the pipe to cure the adhesive between the optical fiber and the pipe. 2. The two optical fibers to be connected are inserted from both ends of a pipe having an inner diameter slightly larger than the outer diameter of the strand, and the photocurable adhesive introduced in advance is sandwiched inside the pipe. After joining the optical fibers of the book, then irradiating light of a wavelength that does not react with the adhesive from the cross-sectional direction of the pipe, image processing the transmitted light to align the core or clad, and then one end of the optical fiber It is characterized in that light of a wavelength that cures the adhesive is injected to cure the adhesive on the joint surface, and thereafter, light is irradiated from the outside of the pipe to cure the adhesive between the optical fiber and the pipe. Optical fiber connection method. 3. The light of core guided mode is first incident to cure the adhesive in the center of the optical fiber joint surface, and then,
3. The method of connecting optical fibers according to claim 1, wherein light in a clad waveguide mode is incident to cure the adhesive in the peripheral portion of the optical fiber joint surface. 4. The method of connecting optical fibers according to claim 1, wherein the adhesive has a refractive index equal to that of the core. 5. When two optical fibers are different from each other,
4. The optical fiber connecting method according to claim 1, wherein the adhesive has a refractive index larger than that of the core of the low refractive index fiber and smaller than that of the core of the high refractive index fiber. 6. The method of connecting optical fibers according to claim 1, wherein the linear expansion coefficient of the adhesive is equal to the linear expansion coefficient of the optical fiber. 7. When two optical fibers are different from each other,
The linear expansion coefficient of the adhesive is larger than that of the low expansion coefficient fiber,
It is smaller than a high expansion coefficient fiber, The connection method of the optical fiber of Claims 1-5 characterized by the above-mentioned.