JP3823812B2 - Method and apparatus for fusion splicing of silica-based optical waveguide element and optical fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fusion splicing method between a glass waveguide element and an optical fiber.
[0002]
[Prior art]
FIG. 2 is a diagram showing a cross-sectional structure of a general silica-based optical waveguide element.
[0003]
As shown in FIG. 2, in general, the silica-based optical waveguide element 6 includes a lower clad 3 made of a quartz substrate, and a core 1a, which has a refractive index increased by adding impurities such as Ti and Ge to a silica-based glass. 1b and an upper clad 2 made of multicomponent glass obtained by adding B ₂ O ₃ and P ₂ O ₅ to glass containing SiO ₂ as a main component.
[0004]
The upper clad 2 is formed using a flame deposition method.
[0005]
The flame deposition method is a method of heating fine particles of SiCl ₄ , BCl ₄ , and PCl _{4 in an} oxyhydrogen flame and hydrolyzing them to produce glass particles (SiO ₂ as the main component, B ₂ O ₃ , P ₂ O ₅ ) is deposited on a quartz substrate and sintered at a high temperature of 1300 ° C. or higher to form a transparent glass.
[0006]
In general, in a multicomponent glass formed by a flame deposition method, the softening temperature decreases and the viscosity at the sintering temperature decreases as the impurity concentration increases.
[0007]
Utilizing this property, for example, when an optical waveguide device 6 having an optical circuit pattern with a narrow core gap, such as the cores 1a and 1b, is produced, the multi-component glass serving as the upper cladding 2 is used to completely fill the core gap. Impurity concentration may be set high.
[0008]
However, if the impurity concentration of the multi-component glass is too high, the quartz substrate after sintering is greatly warped due to the difference in thermal expansion coefficient between the quartz substrate and the multi-component glass. This may cause peeling and the like, and there is an upper limit to the impurity concentration added to the multicomponent glass.
[0009]
On the other hand, when the silica-based optical waveguide element 6 is used in an optical communication system, connection with an optical fiber is required. As one of the connection methods, there is a fusion connection method in which the silica-based optical waveguide element 6 and the optical fiber are fused and integrated to be permanently connected. The fusion splicing method is characterized in that almost no reflected return light is generated at the connection part and there is almost no fluctuation in the coupling efficiency due to temperature changes, and its use in applications requiring high reliability has been promoted. Yes.
[0010]
FIG. 3 is a diagram showing a fusion splicing method between a general silica-based optical waveguide element 6 and an optical fiber 9. When the optical circuit formed in the silica-based optical waveguide element 6 and the optical fiber 9 are fusion-connected, the end face of the silica-based optical waveguide element 6 and the optical fiber 9 are abutted, and the abutting portion 11 is irradiated with the laser beam 10. Then, the fusion splicing is performed by heating and melting the butted portion 11.
[0011]
In this case, in addition to the conditions such as the output of the laser beam 10, the irradiation time, and the irradiation interval, the impurity concentration conditions of the upper clad 2 of the silica-based optical waveguide element 6 to be fused are determined in advance.
[0012]
[Problems to be solved by the invention]
By the way, since the multicomponent glass used as the upper clad 2 of the quartz-based optical waveguide element 6 generally has a softening temperature lowering as the impurity concentration increases, gas components such as O ₂ and He dissolved in the film increase. When the butted portion 11 between the end face of the silica-based optical waveguide element 6 and the optical fiber 9 is dissolved by irradiation, gas components that cannot be completely dissolved in the clad 2 of the silica-based optical waveguide element 6 are easily generated as bubbles.
[0013]
When bubbles are generated, there is a problem that the bubbles remain in the fusion part, the connection strength of the fusion part is lowered, and the connection loss is further increased.
[0014]
For this reason, there existed a subject that a fusion splicing cannot be applied with respect to the multicomponent glass which raised the impurity concentration and lowered the softening temperature.
[0015]
Accordingly, an object of the present invention is to solve the above-mentioned problems, and a fusion splicing method capable of fusion splicing a silica-based optical waveguide element having a multi-component glass with a high impurity concentration in a clad and an optical fiber without generating bubbles. It is to provide such a device.
[0016]
[Means for Solving the Problems]
To accomplish the above object, an optical fiber silica-based optical waveguide device was placed in a pressure chamber, increasing the pressure in said pressure chamber to be higher than atmospheric pressure, the quartz the system optical waveguide element is heated by the heater, in which fused by irradiating a laser beam to the portion abutting the optical fiber and the silica-based optical waveguide device.
[0017]
The upper clad of the silica-based optical waveguide element is formed of multicomponent glass obtained by adding B ₂ O ₃ and P ₂ O ₅ to SiO ₂ , and the B ₂ O ₃ and P ₂ O _{5 are used.} The component ratio is preferably 8% to 10% with respect to the entire multicomponent glass.
[0018]
Fusion splicing apparatus, a pressure chamber containing a silica-based optical waveguide device and the optical fiber airtight, and a pressure means for raising the pressure higher than at least atmospheric pressure in said pressure chamber, Laser light irradiation means for irradiating laser light for fusion-connecting the silica-based optical waveguide element and the optical fiber to a heater provided in the pressure chamber for heating the silica-based optical waveguide element When, was constructed and a window for introducing provided in the pressure chamber the laser beam from the outside of the pressurized chamber. The heater may be provided in a jig that fixes the silica-based optical waveguide element and the optical fiber.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0020]
FIG. 1 is a side sectional view of the fusion splicing device 12.
[0021]
As shown in FIG. 1, the fusion splicing device 12 includes a pressurized chamber 4 that hermetically accommodates the silica-based optical waveguide element 6 and the optical fiber 9, and the atmospheric pressure in the pressurized chamber 4 is at least higher than atmospheric pressure. And pressurizing means 13 for increasing the pressure.
[0022]
The pressurizing chamber 4 is formed in a shape in which both ends of the cylinder are hermetically closed, and a window 5 made of Zn—Se is provided on the peripheral surface of the pressurizing chamber 4.
[0023]
The window 5 is for introducing a laser beam 10 for fusion-connecting the silica-based optical waveguide element 6 and the optical fiber 9 from the outside of the pressurizing chamber 4. Is airtight.
[0024]
The laser beam 10 is irradiated from a light source (not shown) outside the pressurizing chamber 4, and specifically comprises a CO ₂ laser.
[0025]
In addition, a fixing jig 8 is provided in the pressurizing chamber 4 so as to be detachable so as to keep the quartz optical waveguide element 6 and the optical fiber 9 in contact with each other.
[0026]
The fixing jig 8 is mounted at a position facing the window 5 so as not to interfere with the irradiation of the laser beam 10, that is, a position facing the window 5 on the diameter line (direct position). The waveguide element 6 has a preheating heater 7 for heating.
[0027]
The heater 7 is specifically composed of a ceramic heater 7 and is in close contact with the back side of the optical waveguide element 6. Then, under the high pressure at which the melting temperature of the silica-based optical waveguide element 6 and the optical fiber 9 becomes high, the amount of heat that is insufficient with the laser beam 10 alone is compensated.
[0028]
The pressurizing means 13 includes a compressor 15. The compressor 15 is connected to the pressurization chamber 4 via an air pipe 16 so that pressurized air can be sent into the pressurization chamber 4.
[0029]
Next, the operation will be described.
[0030]
The end face of the silica-based optical waveguide element 6 formed using multicomponent glass having a high impurity concentration and the optical fiber 9 are brought into contact with each other and placed on the fixing jig 8. The fixing jig 8 is fastened in a state where the end face of the quartz optical waveguide element 6 and the optical fiber 9 are abutted with each other.
[0031]
Thereafter, the fixing jig 8 is mounted at a predetermined position in the pressurizing chamber 4 to close the pressurizing chamber 4 in an airtight manner.
[0032]
When the compressor 15 is operated and the pressure in the pressurizing chamber 4 reaches a predetermined pressure higher than the atmospheric pressure, the quartz-based optical waveguide is heated while energizing the ceramic heater 7 to apply heat to the quartz-based optical waveguide element 6. The butted portion 11 between the element 6 and the optical fiber 9 is irradiated with the laser beam 10. The laser beam 10 is irradiated from outside the pressurizing chamber 4 through the window 5.
[0033]
At this time, since the pressure in the pressurizing chamber 4 is high, the quartz-based optical waveguide element 6 and the optical fiber 9 are not melted unless the temperature is higher than the melting temperature under atmospheric pressure. Since it is also heated, it is easily melted.
[0034]
Further, in an environment where the atmospheric pressure is high, gas components such as O ₂ and He dissolved in the multicomponent glass are hardly vaporized, and bubbles are not generated in the butt portion 11 to be fusion-bonded.
[0035]
When the quartz-based optical waveguide element 6 and the optical fiber 9 are fused, the irradiation of the laser beam 10 is stopped and the energization to the ceramic heater 7 is stopped.
[0036]
By naturally cooling the silica-based optical waveguide element 6 and the optical fiber 9 while maintaining the internal pressure in the pressurizing chamber 4 at a high pressure, the silica-based optical waveguide element 6 and the optical fiber 9 are melted in a state free from bubbles. Incoming connection.
[0037]
Thus, the silica-based optical waveguide element 6 and the optical fiber 9 is installed in the pressure chamber 4 increases the pressure within the pressure chamber 4 so as to be higher than the atmospheric pressure, silica-based optical waveguide element 6 Is heated by a heater 7 and is fused by irradiating a laser beam to a portion where the quartz optical waveguide element 6 and the optical fiber 9 are abutted, so that it is formed using multicomponent glass having a high impurity concentration. The fused silica optical waveguide element 6 and the optical fiber 9 can be fusion-spliced satisfactorily without generating bubbles.
[0038]
In addition, the fusion splicing device 12 is used to raise the pressure in the pressure chamber 4 in which the silica-based optical waveguide element 6 and the optical fiber 9 are hermetically sealed and the pressure in the pressure chamber 4 to at least higher than the atmospheric pressure. A pressure unit 13, a heater 7 provided in the pressure chamber 4 for heating the silica-based optical waveguide element 6, and a laser for fusion-bonding the silica-based optical waveguide element 6 and the optical fiber 9. a light source for irradiating light 10, because the the provided et Lele laser light 10 to the pressure chamber 4 constituted by a window 5 for introducing the pressure chamber 4 outside the heavily doped multicomponent glass The silica-based optical waveguide element 6 and the optical fiber 9 formed by using them can be easily fusion-spliced.
[0039]
Since an experiment was conducted to verify the effect of the present invention, the experimental result will be described.
[0040]
As shown in FIG. 2, the silica-based optical waveguide element 6 used in the experiment is formed with a glass film serving as the waveguide cores 1a and 1b on the lower clad 3 made of a quartz substrate to a thickness of 8 μm using the EB vapor deposition method. Then, an optical circuit pattern is formed on the lower clad 3 by using a photolithography technique, and a multi-component glass to be the upper clad 2 is formed on the optical circuit pattern by using a flame deposition method. did.
[0041]
The multi-component glass formed at this time was obtained by adding B ₂ O ₃ and P ₂ O ₅ mainly composed of SiO ₂ , and the respective component ratios were 8% and 8% with respect to the entire multi-component glass. It was.
[0042]
The impurity concentration of the multicomponent glass has an upper limit due to the problem of warpage due to the difference in thermal expansion coefficient between the quartz substrate and the multicomponent glass, and the upper limit is generally B ₂ O ₃ or P ₂ O mainly composed of SiO _{2. In} the case of multicomponent glass to which ₅ is added, B ₂ O ₃ and P ₂ O ₅ are about 10% each with respect to the entire multicomponent glass.
[0043]
The experiment was performed using the fusion splicer 12 shown in FIG.
[0044]
First, the end face of the silica-based optical waveguide device 6 manufactured by the above-described method and the optical fiber 9 were brought into contact with each other, fixed, and then installed in the pressurizing chamber 4.
[0045]
After the pressure in the pressurizing chamber 4 is set to 12000 hPa (about 12 times the atmospheric pressure), the ceramic heater 7 is energized and heated to about 500 ° C., and the laser beam (CO ₂ laser) 10 is output to the optical waveguide element 6 at an output of 8 W. The butt portion 11 with the optical fiber 9 was irradiated.
[0046]
After the fusion splicing was completed in this way, the preheating ceramic heater 7 was turned off and cooling was performed for 1 hour while maintaining the pressure in the pressurizing chamber 4.
[0047]
As a result, no bubbles remained in the fusion spliced portion, the connection loss was 0.3 dB, the average tensile strength was 1000 g, and it was confirmed that the fusion spliced well.
[0048]
Then, the upper cladding 2 to form a multi-component glass comprising the addition of B ₂ O _3, P ₂ O ₅ to SiO _2, and the B ₂ O _3, a multi respectively P ₂ O ₅ ratio of components It was confirmed that the optical fiber 9 can be fusion-bonded very effectively to the silica-based optical waveguide element 6 having 8% to 10% of the entire component glass.
[0049]
On the other hand, fusion splicing was performed in the same manner and under the same conditions except that the pressure in the pressurizing chamber 4 was changed to atmospheric pressure (1013 hPa).
[0050]
As a result, bubbles were generated in the fusion spliced portion, the connection loss varied greatly from 0.5 dB to 1.0 dB, and the average tensile strength was 400 g.
[0051]
Thereby, it was confirmed that the fusion splicing between the silica-based optical waveguide element 6 and the optical fiber 9 is required to be performed at a pressure higher than at least atmospheric pressure.
[0052]
The window 5 is made of Zn-Se, but the present invention is not limited to this. Any other material can be used as long as it can withstand the high pressure in the pressurizing chamber and can transmit the laser beam 10 satisfactorily. Good.
[0053]
Further, the pressurizing means 13 is not limited to the compressor 15. Other things such as a gas cylinder may be used as long as the inside of the pressurizing chamber 4 can be increased to a predetermined pressure.
[0054]
In this case, the gas may be any gas such as nitrogen, air, carbon dioxide, oxygen, etc. as long as it does not hinder the fusion, such as burning at a particularly low ignition point.
[0055]
【The invention's effect】
In short, according to the present invention, the following excellent effects can be obtained.
(1) A silica-based optical waveguide device having a multicomponent glass with a high impurity concentration in the cladding and the optical fiber can be fusion-bonded without generating bubbles.
[Brief description of the drawings]
FIG. 1 is a sectional side view of a pressurized chamber showing a preferred embodiment of the present invention.
FIG. 2 is a schematic explanatory view showing a cross-sectional structure of a general silica-based optical waveguide element.
FIG. 3 is a schematic explanatory view showing a general fusion splicing method.
[Explanation of symbols]
2 Upper cladding 4 Pressurizing chamber 5 Window 6 Silica-based optical waveguide element 9 Optical fiber 10 Laser light 12 Fusion splicer 13 Pressurizing means

Claims (4)

A silica-based optical waveguide device and the optical fiber was placed in a pressure chamber, the air pressure in the pressure chamber is raised to higher than the atmospheric pressure, the silica-based optical waveguide element is heated by the heater, the fusion splicing method of the silica-based optical waveguide device and the optical fiber, which comprises fusing by applying a laser beam to the butt portion of the optical fiber and the silica-based optical waveguide device. An upper cladding of the silica-based optical waveguide device to form a multi-component glass comprising the addition of _{B 2 O 3, P 2 O} 5 to SiO _2, and the components of the _{B 2 O 3, P 2 O} 5 The method for fusion splicing of a silica-based optical waveguide element and an optical fiber according to claim 1, wherein the ratio is 8% to 10% with respect to the entire multicomponent glass. A pressure chamber containing a silica-based optical waveguide device and the optical fiber airtight, and a pressure means for raising the pressure higher than at least atmospheric pressure in said pressure chamber, said silica-based optical waveguide device A heater provided in the pressurizing chamber for heating the laser, laser light irradiation means for irradiating a laser beam for fusion-bonding the silica-based optical waveguide element and the optical fiber, and the pressurization chamber fusion splicing apparatus being characterized in that and a window for introducing the outside of the pressure chamber the laser beam provided. 4. The fusion splicing apparatus according to claim 3, wherein the heater is provided in a jig for fixing the silica-based optical waveguide element and the optical fiber.

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