JP3681439B2 - Connection method between optical waveguide and optical fiber - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for aligning and connecting an input / output optical fiber array to an end face of an optical waveguide.
[0002]
[Prior art]
Conventionally, silica glass-based optical waveguide elements mainly composed of quartz glass among optical waveguide elements have low optical transmission loss and can be connected to silica glass-based optical fibers with low loss. Since the optical functions can be integrated, it is expected to be used in a large amount in the construction of an optical communication network in the future.
As a method for manufacturing this silica-based optical waveguide, for example, as shown in Masao Kawauchi, “Application to Silica-based Optical Waveguide and Integrated Optical Components” Optical Volume 18 No. 12 (December 1989) p681-686 The most common method is a combination of glass film formation by deposition method (FHD: Flame Hydrolysis Deposition) and glass film formation by reactive ion etching (RIE).
[0003]
Specifically, as shown in FIG. 3, first, glass raw materials such as SiCl4 and TiCl4 are supplied to the burner 1 to obtain glass fine particles 3 by hydrolysis and oxidation reactions in an oxyhydrogen flame 2, and this is converted into Si. The glass fine particle films 5a and 5b having different refractive indexes are sequentially formed by being deposited on the substrate 4 such as a wafer ((a) in the figure). Here, it is assumed that the compositions of the glass fine particle films 5a and 5b are different (refractive indexes are different).
[0004]
Then, the glass fine particle films 5a and 5b sequentially formed in the above-described steps are heated to a high temperature, whereby the glass fine particle films 5a and 5b are made into transparent glass to form the lower clad layer 6a and the core layer 6b (FIG. 5B). ). The above is the flame deposition method.
Next, an unnecessary portion of the core layer 6b is removed by reactive etching to leave a ridge-shaped core portion 6c (FIG. 3C), and the upper cladding layer is again covered with the flame deposition method so as to cover the core portion 6c. By forming 6d, a buried type quartz optical waveguide is formed. Since a plurality of repeated optical waveguide patterns are formed on the substrate through the above steps, the optical waveguide chip 7 is completed by dividing the substrate for each waveguide pattern.
[0005]
Next, in order to input light to the optical waveguide element or to extract output light, an optical fiber for input / output, that is, an optical fiber array, is connected to each of the waveguides. For connection with an optical fiber, various methods such as fusion by laser light, adhesion by an adhesive, and mechanical pressure welding between optical path ends are adopted. Since the connection of the optical fiber array to the optical waveguide element is a multi-core connection, the connection with an adhesive is the mainstream for reasons such as low optical loss and high-accuracy connection at low cost. .
[0006]
[Problems to be solved by the invention]
By the way, in the optical waveguide chip connected to the above-described conventional optical fiber array, that is, the optical component, both the manufacture of the waveguide chip and the connection between the waveguide chip and the optical fiber array have a drawback that it takes time.
That is, in the production of the waveguide chip, conventionally, the FHD and sintering processes are used twice for the formation of the lower cladding layer and the core layer, and the formation of the upper cladding layer. FHD is a process that takes several hours at a time, including sintering, and it takes a long time to manufacture an optical waveguide chip. Also, since high temperatures are applied to the sintering of the quartz glass-based lower clad layer, core layer, and upper clad layer, for example, when silicon is used as a substrate, the high temperature between the substrate and quartz glass is increased after sintering. There is also a problem that warpage occurs due to the shrinkage difference between the optical waveguide chip and the accuracy of connection with the input / output optical fiber array is lost.
[0007]
In addition, both the optical waveguide cross-sectional area and the optical fiber core cross-sectional area are extremely small (10 μm 2), it is difficult to align, and it is difficult to confirm whether the light from the optical fiber has reached the optical waveguide. Manual rough alignment with the naked eye was difficult and time consuming. In addition, the connection portion between the optical waveguide having a small cross-sectional area and the optical fiber is misaligned due to a slight external force, resulting in problems such as an increase in connection loss and breakage of the optical fiber.
[0008]
Furthermore, since optical waveguide elements are required to be downsized and their protective equipment tends to be small, optical waveguide elements made of quartz glass, which is a brittle material, have low toughness and can be damaged by slight impacts. It was built in.
An object of the present invention is to provide a connection method for connecting an end face of an optical fiber array for input / output of an optical signal to an end face of an optical waveguide precisely and at low cost. .
[0009]
[Means for Solving the Problems]
In order to solve this problem, the optical waveguide and optical fiber connection method of the present invention is a method of aligning and connecting the end face (16) of the optical waveguide (13) and the end face (23) of the optical fiber array. The surface including the end surface of the core layer of the optical waveguide is an inclined surface with respect to the optical axis direction of the optical waveguide, and the surface including the end surface of the optical fiber of the optical fiber array is the inclined surface of the optical waveguide. And an end face of the optical waveguide and the end face of the optical fiber are arranged to face each other, and after temporarily applying an ultraviolet curable resin (30) so as to cover the core layer of the optical waveguide, Aligning the end face of the core layer of the optical waveguide and the end face of the optical fiber, pouring an ultraviolet curable resin over the entire upper surface of the optical waveguide, and covering the surface of the optical waveguide including the core layer with this ultraviolet curable resin, Core Filling the gap between the layer and the end face of the optical fiber, irradiating and curing the ultraviolet curable resin with ultraviolet rays , forming the ultraviolet curable resin as an upper cladding layer of the optical waveguide, and by the cured ultraviolet curable resin, An optical waveguide and the optical fiber are fixedly connected.
[0010]
【Example】
An embodiment of the method of the present invention will be described below with reference to the drawings.
FIG. 1 is a view for explaining the structure of an optical component according to an embodiment of the present invention. In the figure, 18 is an optical waveguide semi-finished product chip, and 25 is an optical fiber array. In the optical component 40, the upper clad layer 37 of the semi-finished optical waveguide chip 18 shown in FIG. The optical fiber connection end faces 23 and 23 of the optical fiber arrays 25 and 25 shown in FIG.
[0011]
FIGS. 2A and 2B show the configuration of an optical waveguide semi-finished product chip. The optical waveguide semi-finished product chip 18 includes a lower clad layer 12 on a substrate 11, a core layer 13 on which an optical waveguide is formed, and a core layer 13 of a chip 15 in which a glass reinforcing body 14 is bonded to the bottom surface of the substrate. The two surfaces 17a and 17b including the connection end surfaces 16a and 16b are inclined connection surfaces inclined downward.
[0012]
FIG. 2C shows a schematic configuration of the input / output optical fiber array. In the optical fiber array 25, the optical fiber 20 is disposed in a fine groove formed on the upper surface of the lower glass plate 21 of the two glass plates 21, 22, and the upper glass plate 22 is covered with the optical fiber 20 and bonded. After the optical fiber 20 and the glass plates 21 and 22 are bonded and fixed with an agent, the surface 24 including the connection end surface 23 of the optical fiber 20 is inclined obliquely upward so as to be connectable to the connection surface of the optical waveguide semi-finished product chip 18. The surface 24 is configured.
[0013]
FIG. 2D is a diagram in which the optical waveguide semi-finished product chip and the optical fiber array configured as described above are arranged for manufacturing an optical component. In this figure, the connection end faces 16a and 16b of the core layer 13 of the optical waveguide semi-finished chip 18 and the connection end faces 23 and 23 of the two optical fiber arrays 25 and 25 are fixed on a centering table (not shown). Are arranged to be opposed to each other with an interval of. A viscous ultraviolet curable resin 30 is supplied from a nozzle 31.
FIG. 2E shows the configuration of the optical component. 30 is a poured ultraviolet curable resin, 33 is an ultraviolet light source, and 35 is a solid ultraviolet curable resin. The solid ultraviolet curable resin 35 covering the upper surface of the core layer 13 of the optical waveguide semi-finished chip 18 constitutes an upper clad layer 37, and both connection portions 16 a and 16 b of the core layer 13 and connection end surfaces 23 and 23 of the optical fiber are The optical component 40 is configured by being connected by a solid ultraviolet curable resin 35.
[0014]
Next, a method for manufacturing the optical component 40 will be described mainly with reference to FIGS.
The optical waveguide semi-finished chip 18 is prepared by flame deposition and sintering of the lower cladding layer 12 and the core layer on the silicon substrate 11 (FIG. 3B), and then only the optical waveguide portion is formed by reactive ion etching. The remaining core layer 13 is formed (FIG. 3C). The auxiliary glass body 14 is bonded to this to form a chip 15 (FIG. 2A). Further, the optical waveguide semi-finished product chip 18 is manufactured by processing and polishing the connection surfaces 17a and 17b including both connection end surfaces 16a and 16b of the core layer 13 of the chip 15 into a connection surface inclined obliquely downward. (FIG. 2 (b)).
[0015]
On the other hand, in the optical fiber array 25, micro holes are formed in the mating surfaces of the two glass plates 21 and 22, the optical fibers are inserted into the micro holes, and the optical fibers are fixed together with the mating surfaces by an adhesive. After that, the surface including the connection end surface 23 of the optical fiber is processed into a connection surface 24 inclined obliquely upward and polished (FIG. 2C).
Next, the two input / output optical fiber arrays 25, 25 are connected to the connection end faces 16a, 16b of the core layer 13 of the core layer 13 of the semi-finished optical waveguide chip 18 manufactured as described above. The optical fiber connection end faces 23 and 23 are opposed to each other and installed on a centering device (not shown) (FIG. 2D).
[0016]
Therefore, the alignment of both optical paths of the core layer 13 and the optical fiber 20 is performed as follows according to the order of the first coarse alignment and the second and subsequent automatic alignment. Coarse alignment is a rough alignment, in which the position where an optical signal is transmitted from the input fiber to the core layer and from the core layer to the output fiber is manually detected. First, it is assumed that the surface of the core layer 13 is thinly coated with a viscous UV curable resin 30. In this state, light is confined in the core layer 13, and no light oozes out from the core layer 13 or light enters the core layer 13 from the outside. Further, when the coating layer is thin, the signal light incident on the core layer 13 can be confirmed with the naked eye. Therefore, the coarse alignment can be completed in a short time by confirming that the optical signals from the input and output optical fibers 20 and 20 are transmitted to the core layer 13.
[0017]
Automatic alignment is a method of mechanically searching for an optimum connection position where an optical signal is input from an input optical fiber, transmitted through the core layer 13, and output from the output optical fiber is maximized. In this embodiment, the end faces (16a, 16b) of the optical waveguide 13 and the connection faces 23, 23 of the optical fiber 20 are bonded to each other by a viscous ultraviolet curable resin 30, and the relative end faces of both optical paths are mechanically relative to each other. The position is changed little by little to search for the optimum connection position. After the alignment is completed, the ultraviolet resin is solidified by ultraviolet irradiation, and both optical path end faces are fixedly connected to the automatically aligned optimum position. As a result, compared to the first alignment, a more precise connection is possible, and an optimum connection position can be stably maintained. In addition, the connection surfaces 16a, 16b, 23, and 23 of the core layer 13 and the optical fiber 20 are processed into inclined surfaces, so that the connection area is increased and the connection strength is high, which effectively acts to stably maintain the connection position. .
[0018]
Thereafter, a viscous ultraviolet curing resin 30 is poured into the upper surface of the optical waveguide semi-finished chip 18. The viscous UV curable resin flows, covers the surface of the optical waveguide semi-finished chip 18 including the core layer 13, and further fills the gap between the connection surfaces of the core layer 13 and the optical fiber 20.
Next, the ultraviolet curable resin 30 of the viscous material is irradiated with ultraviolet rays to convert the ultraviolet curable resin into a solid. An optical waveguide element 40 is completed in which the solid ultraviolet curable resin 35 is used as the upper cladding layer 37 and the input / output optical fiber array 25 is fixedly connected by the resin 35.
[0019]
The refractive index of the ultraviolet curable resin 30 can be adjusted to a necessary value for the cladding layer 37. Therefore, by using the ultraviolet curable resin 35 whose refractive index is adjusted to a predetermined value, the upper clad layer 37 having necessary optical characteristics can be obtained.
Further, the solid ultraviolet curable resin 35 has higher toughness than quartz glass and is resistant to impact. Therefore, the optical component in which the upper clad layer 37 is made of the resin 35 is excellent in impact resistance and has a low risk of breakage. And the protector of this optical waveguide element 40 can be reduced in size.
[0020]
The optical waveguide element 40 to which the optical fiber array 25 manufactured as described above is connected has the following characteristics. That is,
The creation time of the optical waveguide element 40 can be greatly shortened. That is, since the upper cladding layer 37 is made of the ultraviolet curable resin 35, the manufacturing time can be shortened. Further, when the effect of connecting the optical fiber array 25 and the core layer 13 simultaneously with the production of the upper clad layer 37 and the time for rough alignment can be reduced, the production time of the optical component 40 can be greatly reduced. .
[0021]
In addition, the upper clad layer 37 made of the ultraviolet curable resin 35 does not require a high temperature. Therefore, the thermal effect due to flame deposition and sintering is once, the warping of the substrate 11 is halved, and the influence on the optical waveguide element characteristics can be prevented.
Further, in the connection between the optical waveguide chip 18 and the optical fiber array 25, coarse alignment and automatic alignment are precisely performed, and the connection between both optical paths after the alignment is fixed, so that the core layer 13 and the optical fiber array 25 are fixed. Therefore, it is possible to manufacture an optical waveguide element that is stably connected with high accuracy.
[0022]
In the above embodiment, the optical waveguide chip 18 is configured using a silicon substrate. However, the optical waveguide chip 18 is not particularly limited. For example, the same effect can be obtained by using quartz glass, multicomponent glass, or the like. it can.
In the present invention, each alignment step does not necessarily require temporal continuity. That is, for example, even if the first coarse alignment is performed in several steps, the first alignment is meant as a whole.
[0023]
【The invention's effect】
According to the present invention, by using an ultraviolet curable resin having a necessary refractive index in a solidified state as a cladding layer of an optical waveguide, compared with a manufacturing method by FHD that requires several hours at a time, sintering, An optical waveguide chip can be formed in about half the time. In addition, impact resistance of optical components obtained by using UV curable resin, which has higher toughness than glass-based materials, as the upper cladding layer and connecting the core layer and optical fiber array between the connection surfaces Is high, and the size of the protective equipment can be reduced.
[0024]
In addition, the upper cladding layer and the optical fiber array are connected simultaneously. Including the manufacturing time shortening effect by using the above-mentioned clad layer as an ultraviolet curable resin, according to this method, the manufacturing time of the optical component can be greatly shortened, and the cost can be greatly reduced.
Further, by forming the upper clad layer with an ultraviolet curable resin, the warpage of the substrate due to the thermal influence on the substrate was reduced, and the effect of reducing the deterioration of the optical component characteristics due to the warpage was obtained.
[0025]
Furthermore, by covering the core layer thinly, light is confined in the optical waveguide, and when the coating layer is thin, the light in the optical waveguide is visible with the naked eye. The optical signal from the input and output optical fibers can be easily performed only by visually recognizing that the optical signals are transmitted to the core layer. In addition, the UV-curing resin of viscous fluid was precisely aligned by automatic alignment while the connection surface was adhered, and then the UV-curing resin was solidified by irradiating with UV to achieve precise alignment. An optical component in which the connection position of both optical paths is fixed and the connection position of the optical fiber array is fixed accurately and stably is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical waveguide element in which an end face of an optical fiber array is connected to an end face of an optical waveguide according to the present invention.
FIG. 2 is an explanatory view showing a method for connecting an end face of an optical waveguide and an end face of an optical fiber array according to the present invention.
FIG. 3 is an explanatory diagram of a conventional method for producing an optical waveguide chip.
[Explanation of symbols]
13 Core layer 16a forming optical waveguide One end face 16b of optical waveguide The other end face 20 of the optical waveguide 20 Optical fiber 23 Optical fiber end face 30 UV curable resin 40 of viscous material Optical waveguide element connected with input / output optical fiber

Claims (1)

A method of aligning and connecting the end face (16) of the optical waveguide (13) and the end face (23) of the optical fiber array,
The surface including the end surface of the core layer of the optical waveguide is inclined with respect to the optical axis direction of the optical waveguide, and the surface including the end surface of the optical fiber of the optical fiber array is connected to the inclined surface of the optical waveguide. It can be an inclined surface,
An end face of the optical waveguide and an end face of the optical fiber are arranged to face each other,
After temporarily applying the ultraviolet curable resin (30) so as to cover the core layer of the optical waveguide, alignment between the end surface of the core layer of the optical waveguide and the end surface of the optical fiber is performed,
An ultraviolet curable resin is poured over the entire upper surface of the optical waveguide, the surface of the optical waveguide including the core layer is covered with the ultraviolet curable resin, and a gap between the core layer and the end face of the optical fiber is filled.
The ultraviolet curable resin is cured by irradiating ultraviolet rays, and the ultraviolet curable resin is used as an upper clad layer of the optical waveguide,
A method of connecting an optical waveguide and an optical fiber, wherein the optical waveguide and the optical fiber are fixedly connected by the cured ultraviolet curable resin.

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