JP3022132B2 - Fusion splicing method between silica glass waveguide element and optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fusion splicing method between a silica glass waveguide device and an optical fiber.

[0002]

2. Description of the Related Art In recent years, quartz-based glass waveguide optical components made of a quartz-based material include a quartz-based glass waveguide element (hereinafter, referred to as a waveguide element) and a quartz-based optical fiber (hereinafter, referred to as a waveguide element).
Since a low loss and permanent connection can be achieved by fusion splicing with an optical fiber, an active optical component such as an optical wavelength multiplexer / demultiplexer or an optical star coupler has been actively developed.

Various methods for fusion splicing the waveguide element and the optical fiber have been proposed.
The most common method uses a CO ₂ laser beam as a heat source for fusion as shown in FIG. More specifically, first, the waveguide element 1 fixed in the metal package 10b will be described.
0 and the optical fiber 5 composed of the core 5a and the clad 5b are butted by using the fine adjustment tables 6 and 6, and the optical axis is adjusted so as to minimize the coupling loss. In this optical axis adjustment, the laser light emitted from the semiconductor laser 1 is incident on one end of the optical fiber 5 via the lens 3, and is emitted from the opposite side of the waveguide element 10 by using the fine movement tables 6 and 6. The adjustment is performed while watching the indicated value of the optical power meter 14 so that the optical power becomes maximum. Next, the end face of the optical fiber 5 is crimped to the end face of the glass waveguide element 10 with a crimp amount of about 5 μm, and the laser light emitted from the CO ₂ laser 8 is Zn-
After focusing using the Se lens 11, the CO ₂ laser light P ₁ is applied to the butting portion 15 between the waveguide element 10 and the optical fiber 5.
Are irradiated under a condition of, for example, an irradiation time of about 2 sec, a CO ₂ laser power of about 7 W, and a spot size of about 200 μm as a spot size of the CO ₂ laser beam at the connection portion, and the two are fusion-spliced. In FIG. 6, reference numerals 7 and 2 denote mirrors 4 and 4, respectively.
He-Ne laser used for CO ₂ laser beam position detection, optical axis adjustment of optical fiber 5 and waveguide element 10, 9 is a calorimeter for measuring power of CO ₂ laser light, 12, 13 and 20 are A television camera, a monitor, and a half mirror used for monitoring light emitted from the waveguide element 10, respectively.

As described above, the CO ₂ laser beam is most suitable as a fusion splicing heat source for a quartz-based material because its wavelength is 10.6 μm, it is efficiently absorbed by the quartz-based material, and is collected by a lens. This is because light can be emitted and an arbitrary portion on the quartz-based material can be irradiated as a minute spot to be selectively melted.

[0005]

By the way, in such a conventional fusion splicing method, the CO ₂ laser beam P ₁ is applied while the butt end face of the optical fiber 5 is pressed against the waveguide element 10.
In order to start the heat fusion of the optical fiber 5, a gap is formed between the abutting surfaces 15 of the optical fibers 5 because, for example, the abutting end surfaces of the optical fibers 5 are not cut at right angles, or the end surfaces of the waveguide elements 10 are not ground at right angles. If this occurs, the butted surfaces will not be uniformly melted, and bubbles will remain inside the fusion after fusion, resulting in a decrease in fusion strength and an increase in connection loss. If the heating time is short, the fusion portion on the gap side is not sufficiently integrated, and a notch that reduces the fusion strength is generated. If the heating time is lengthened for sufficient integration, deformation of the core 5a of the optical fiber 5 occurs, and a phenomenon such as an increase in connection loss occurs, and good fusion splicing cannot be achieved.

On the other hand, when a single-mode CO ₂ laser beam is used as a fusion heat source, the CO ₂ laser beam has a Gaussian distribution type energy distribution.
Even if the light is condensed using the n-Se lens 11, it hardly changes, so that it is difficult to uniformly melt the waveguide element 10 and the optical fiber 5 having greatly different heat capacities. Incoming connections cannot be achieved with good reproducibility. That is, as shown in FIG. 7, when the CO ₂ laser beam P ₁ is irradiated vertically from above onto the butting portion 15 of the waveguide element 10 and the optical fiber 5, the optical fiber having a smaller heat capacity than the waveguide element 10 is obtained. The 5th side melts excessively, causing optical axis shift and connection failure. Also, since the power density at the center of the spot of the CO ₂ laser beam P ₁ is extremely large, the temperature gradient at the boundary between the irradiated portion and the non-irradiated portion is increased. And a large thermal stress is generated at the time of irradiation, and the durability of the waveguide element 10 and the optical fiber 5 is impaired. Therefore, the CO ₂ laser light P
_Although it is conceivable to intentionally shift the focal position of ₁ to increase the spot diameter and increase the laser power, as shown in the figure, in the case of a multi-core waveguide element 10 having a plurality of waveguides 10a. In this case, an adjacent optical fiber (not shown) is adversely affected, and similarly, there is a problem that good fusion cannot be performed.

The present invention has been devised in order to effectively solve this problem, and its main purpose is to fusion splice a waveguide element and an optical fiber with low loss and high strength. It is intended to provide a novel method for fusion splicing a silica-based glass waveguide element and an optical fiber.

[0008]

According to a first aspect of the present invention, a quartz glass waveguide device and an optical fiber are butt-aligned so that their optical axes are substantially coincident with each other. In this method, the butt portion is irradiated with a focused CO ₂ laser beam, heated, and fusion spliced.
Immediately before abutting the optical fiber end face to the quartz glass waveguide element end face, between the end face of the quartz glass waveguide element and the end face of the optical fiber, a discharge path was formed so as to cross the end face, According to a second aspect of the present invention, the end face of the silica glass waveguide element and the end face of the optical fiber are opposed to each other at a predetermined interval, and are aligned so that their optical axes coincide with each other. A discharge path is formed on the end face side of the waveguide element so as to cover it, and CO
₍₂₎ Heat by irradiating laser light, then abut the end face of the optical fiber while passing through the discharge path and melting while abutting against the end face of the silica glass waveguide, and immediately thereafter, erase the discharge path. Thus, the end face of the silica glass waveguide element and the end face of the optical fiber are integrally fusion-spliced.

[0009]

According to the first and second aspects of the present invention, the discharge path formed between the end face of the silica glass waveguide element and the end face of the optical fiber immediately before the optical fiber is brought into contact with the silica glass waveguide element. Then, after the end face is appropriately melted, the end face is brought into contact with the end face of the quartz glass waveguide element. Therefore, even when the end face of the optical fiber is not cut at a right angle or the end face of the waveguide element is not polished at a right angle, the end face of the optical fiber melts and softens in the discharge path, so that both are good. Butts are fused together, so that inconveniences such as an increase in transmission loss and a decrease in fusion strength can be prevented.

[0010]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 3 show one embodiment of the fusion splicing method according to the first and second inventions.
Numeral 0 denotes a waveguide element on which a waveguide is formed, 16 denotes an optical fiber in which the end face 16a faces the end face 15a of the waveguide element 10 and the end face 16a is slightly obliquely cut, 17 and 18 denote discharge electrodes, and 19 denotes a discharge electrode. A discharge path generated between the discharge electrodes 17 and 18,
P ₁ is a CO ₂ laser beam as a heat source for fusion, and 11 is a CO ₂ laser beam.
Zn-S for irradiating _two laser beams P ₁ to abutting surface 15 near the waveguide element 10 and the optical fiber 16 is condensed
e lens.

The fusion splicing of the optical fiber 16 and the waveguide element 10 is performed by first aligning the waveguide element 10 and the optical fiber 16 using the above-described conventional device, and then aligning the end faces 15a, 15a of the two. 16a are opposed to each other at a predetermined interval. Next, the waveguide element 10 is heated by vertically irradiating the CO ₂ laser beam P ₁ above the end face 15 a of the waveguide element 10, and the discharge electrodes 17 and 18 cover the vicinity of the abutting portion 15. After generating the discharge path 19, the optical fiber 16 is moved to the waveguide element 10 side, and the end face 16a
Is brought closer to the end face 15a side of the waveguide element 10. Then, when the end face 16a of the optical fiber 16 enters the discharge path 19, as shown in FIG. 2, the end face 16a in a slightly obliquely cut state starts to melt and soften. It is advanced to abut against the butted end face 15a of the waveguide element 10, and immediately after that, the discharge is stopped.
As shown in FIG. 3, after the optical fiber 16 and the waveguide element 10 are fused and integrated by the heat of the CO ₂ laser beam P ₁ ,
The _second irradiation of the laser light P ₁ is stopped, both fusion splice is completed.

As described above, the method of the present invention provides the waveguide element 10
The discharge path 19 is previously set in the butting portion 15 of the
Is formed, the optical fiber 16 or the end face of the waveguide element 10 is melted and softened before the optical fiber 16 abuts on the end face of the waveguide element. Therefore, not only when the end face 16a of the optical fiber is obliquely cut as in this embodiment, but also when the end face 15a of the waveguide element 10 is not polished at right angles, a gap is formed between the abutting portions 15 thereof. Does not occur, and an increase in connection loss due to a decrease in the fusion strength or the incorporation of air is prevented. In addition, since the two are fused in a short time, it is possible to prevent an increase in connection loss due to deformation of the core of the optical fiber or the like.

Using the method of the present invention, a discharge current value of 15 A, a discharge time of 2 seconds, and a CO ₂ laser power of 2
As a result of performing fusion splicing of the single mode optical fiber and the waveguide element under the condition of W and the laser beam irradiation time of 4 seconds, the average connection loss was 0.18 dB with respect to 50 samples and 0.25 of the prior art.
It was able to be slightly reduced from dB. On the other hand, the tensile strength of the conventional technique was 1 Kg on average, whereas the tensile strength of the method of the present invention was 1.8 Kg on average. Furthermore, while the minimum strength was conventionally 180 g, in the method of the present invention, 1.1 Kg was found, indicating that very stable fusion splicing was performed.

[0015]

In summary, according to the present invention, since the optical fiber is abutted against the waveguide element in a molten state, the optical fiber is melted and integrated in a short time, and is fused without being affected by the end face angle of the optical fiber waveguide element. I can wear it. As a result, the mechanical strength of the fused portion is high and stable, so that long-term reliability is improved. Also, since the heating time is short, the core does not deform,
In addition to enabling low-loss fusion splicing, the working time can be shortened and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a side view showing one embodiment according to the first and second inventions.

FIG. 2 is a side view showing one embodiment according to the first and second inventions.

FIG. 3 is a side view showing one embodiment according to the first and second inventions.

FIG. 4 is an explanatory view showing an example of a conventional fusion splicing method between a silica-based glass waveguide element and an optical fiber.

FIG. 5 is a partially broken perspective view showing an example of the vicinity of a fusion spliced portion between a conventional silica glass waveguide element and an optical fiber.

[Explanation of symbols]

5, 16 Optical fiber 10 Silica-based glass waveguide element 15 Butted portion 15a End face of silica-based glass waveguide element 16a End face of optical fiber 19 Discharge path P CO ₂ laser beam

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 6/30

Claims (2)

(57) [Claims] 1. A quartz glass waveguide device and an optical fiber are butt-aligned so that their optical axes are substantially coincident with each other, and the butt portion is irradiated with a focused CO ₂ laser beam. Then, heating, in a method of fusion splicing the two, just before butting the optical fiber end face to the quartz glass waveguide element end face, between the end face of the quartz glass waveguide element and the end face of the optical fiber, A fusion splicing method between a silica glass waveguide element and an optical fiber, characterized in that a discharge path is formed so as to cross the fiber. 2. An end face of a silica glass waveguide element and an end face of an optical fiber are opposed to each other at a predetermined interval, and
After the two optical axes are aligned, a discharge path is formed on the end face side of the quartz glass waveguide element so as to cover it, and the vicinity thereof is irradiated with CO ₂ laser light and heated. Then, the end face of the optical fiber passes through the discharge path and is melted and abuts against the end face of the silica glass waveguide. Immediately thereafter, the discharge path is erased and the silica glass waveguide element is removed. Wherein the end face of the optical fiber and the end face of the optical fiber are integrally fusion-spliced.