JPH1114859A - Method for connecting optical waveguide and optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To connect an optical fiber to the optical input/output end of a waveguide type optical device easily and highly stably. SOLUTION: An auxiliary block 6 is fixed (b) on an optical waveguide 2 so that the end surface of the auxiliary block 6 and the end surface of the optical waveguide 2 form a step almost in parallel to each other. A cylindrical body 7 is mounted (c) on the optical fiber 3 and the end surface is thermally treated (d) through arc discharging. Then the end surface of the optical fiber 3 is coated (f) with a 1st adhesive 8 and brought into contact (g) with the end surface of the optical fiber 3, and then the adhesive 8 is cured. Then the cylindrical body 7 is contacted with the substrate 1, and a 2nd adhesive 9 is used to connect the substrate 1, optical waveguide 2, auxiliary block 6, and cylindrical body 9 (i). The adhesives 8 and 9 set by irradiation with visible light or ultraviolet rays 13 or 14. The cylindrical body 7 is formed of a material which transmits the visible light or ultraviolet rays sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting an optical waveguide and an optical fiber.
The present invention relates to a method for easily and highly stably connecting an optical fiber to an optical input / output end of a waveguide type optical device.

[0002]

2. Description of the Related Art Conventionally, when connecting an end face of an optical waveguide and an optical fiber, as shown in FIGS. 5 and 6, for example, an optical fiber 3 is inserted into a hollow hole of a cylindrical body 7 and its tip is connected to a cylindrical body. The optical fiber 3 is fixed to the cylindrical body 7 by the adhesive 16 while the optical fiber 3 is made to protrude from the cylindrical body 7, and then the optical fiber 3 and the end face of the optical waveguide 2 are abutted. The substrate 1 and the tubular body 7 are fixed by filling and curing between the tubular bodies 7. At this time, a polishing grinder 15 is bonded and fixed on the optical waveguide 2 in advance, and is polished together with the substrate 1.
Are formed. Therefore, the end face of the optical waveguide 2 and the end face of the polishing grinder 15 form the same plane. 4 is a core of the optical fiber 3 and 5 is a jacket of the optical fiber 3.

When an ultraviolet curing type is used for the adhesive 17,
Since ultraviolet irradiation is forced from the outside of the cylindrical body 7,
The adhesive was cured from the outside having strong ultraviolet intensity, and the curing of the end face of the optical fiber 3 near the center and the end face of the optical waveguide 2 was sometimes insufficient. Further, since the application area of the adhesive 17 is large, the optical waveguide 2 and the optical fiber 3 may be displaced due to shrinkage at the time of curing, and the coupling state may be deteriorated.

[0004]

As described above, the adhesive 17 is filled between the substrate 2, the polishing pad 15 and the cylindrical body 7 by utilizing the capillary phenomenon, and the optical waveguide 2 and the optical fiber 3 are bonded together. In the conventional connection method for connecting, if the distance between the end face of the optical fiber 3 and the end face of the optical waveguide 2 is very small, the adhesive 17
Cannot be filled due to the surface tension of the adhesive, or the adhesive 17 wraps around the cylindrical body 7 quickly, leaving bubbles near the center, so that the gap between the end face of the optical fiber 3 and the end face of the optical waveguide 2 In some cases, an air layer was formed. For this reason, there is a defect that reflection occurs due to a difference in refractive index between the optical waveguide 2 and the optical fiber 3, and an air layer repeatedly expands and contracts due to a heat cycle and peels off at a bonding portion.

[0005] When the optical fiber 3 is held by the jacket 5 while the cylindrical body 7 is fixed or arranged on the end face of the optical fiber 3, the tip of the optical fiber 2 may be bent, Occasionally, it may be required to be skilled to obtain desired characteristics at the time of coupling with the optical waveguide 2 due to vibration or the like.

In the method of forming the end face of the optical waveguide 2 using the polishing grinder 15 as described above, if the thickness of the substrate 1 forming the optical waveguide 2 is smaller than the width of the substrate 1, Unless the polishing grinder 15 is as large as the substrate 1, it is applicable when the substrate 1 is broken near the end of the polishing grinder 15 during polishing or when the end face is formed by cleavage like a semiconductor optical waveguide. There is a disadvantage that it cannot be done.

Furthermore, in the formation of the end face of the optical fiber 3, a breaking method or a polishing method is conventionally used. In the breaking method, the end face of the optical fiber 3 is clean, but burrs may be generated around the end face. This burr causes a positional shift when the optical waveguide 2 is brought into contact with the end face. On the other hand, the polishing method requires time and labor for polishing. Also, after polishing, the polished surface is washed with alcohol or the like to make it a clean surface. However, it is difficult to maintain a high degree of cleanliness because moisture and airborne substances are adsorbed, and it is known that this may cause a decrease in adhesive strength. Have been.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to easily and highly stably connect an optical fiber to an optical input / output end of a waveguide type optical device. It is an object of the present invention to provide a method of connecting an optical waveguide and an optical fiber which can be performed.

[0009]

According to the present invention, there is provided a method for connecting an optical waveguide formed near the surface of a substrate to an end face of an optical fiber, the auxiliary block being provided on the optical waveguide. Fixing so that the end face of the auxiliary block and the end face of the optical waveguide are substantially parallel and a step is generated,
Thereafter, the end face of the optical fiber coated with the adhesive is brought into contact with the end face of the auxiliary block or the end face of the optical waveguide, and thereafter, the adhesive is cured. Also,
The present invention is characterized in that the step between the end face of the auxiliary block and the end face of the optical waveguide is set within 200 μm. Further, the present invention is characterized in that the auxiliary block is made of the same material as the substrate material or a material having a similar thermal expansion coefficient. Further, the present invention provides a method for connecting an optical waveguide formed near the surface of a substrate to an end face of an optical fiber, wherein a cylindrical body having a hollow hole larger than a clad diameter is prepared, and an optical fiber is inserted into the hollow hole. The lever is moved to a position immediately adjacent to the outer cover of the optical fiber, a first adhesive is applied to the end face of the optical fiber, and the end face of the optical waveguide and the end face of the optical fiber are opposed to each other. After the position adjustment between the end face of the optical waveguide and the end face of the optical fiber is performed as described above, the first adhesive is cured to join the end face of the optical waveguide to the end face of the optical fiber. It is characterized in that the cylindrical body and the optical fiber are joined by being brought into contact with the block, filled with the second adhesive and cured, and then joined. Further, the present invention is characterized in that, before applying the first adhesive, the end face of the optical fiber is subjected to a heat treatment such as arc discharge. Further, the present invention is characterized in that the first adhesive is cured by irradiation with visible light or ultraviolet light. Further, in the present invention, the tubular body may be a second body.
The adhesive is characterized by being a material having a sufficient amount of visible light or ultraviolet light to be hardened.

In the present invention, since a step is provided between the end face of the optical waveguide and the end face of the auxiliary block, the position of the end face of the optical waveguide can be directly viewed from above with a microscope or the like. Filling is reliable, workability is excellent, and sufficient adhesive strength can be obtained. If the step is 200 μm or less, the optical fiber will not be misaligned due to shrinkage during curing of the second adhesive. The auxiliary block and the cylindrical body can increase the bonding area when bonding the substrate and the optical fiber with an adhesive, and can obtain a large bonding strength. Since the auxiliary block is made of the same material as the material of the substrate or a material having a similar coefficient of thermal expansion, there is little warpage of the substrate due to temperature fluctuation, and no peeling of the adhesive occurs. Also,
Since the end face of the optical fiber is heated by arc discharge or the like, the end face of the optical fiber can be cleaned and burrs can be removed, and the bonding strength can be increased. The first adhesive is cured by irradiation with visible light or ultraviolet light, and the tubular body is made of a material having a sufficient amount of visible light or ultraviolet light to cure the first adhesive. It is possible to secure sufficient strength and improve workability.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a perspective view of an optical waveguide and an optical fiber connected by the connection method according to the present invention, and FIG. 2 is a sectional view. In these figures, 1 is a substrate, 2 is an optical waveguide formed on the surface of the substrate 1, 3 is a bare optical fiber, 4 is a core of the optical fiber 3, 5 is a jacket of the optical fiber 3, and 6 is an auxiliary block. , 7 is a cylindrical body, 8 is a first adhesive filled between the auxiliary block 6 and the cylindrical body 7,
Reference numeral 9 denotes a second adhesive filled in the hollow hole of the cylindrical body 7. The end faces of the substrate 1 and the optical waveguide 2 form the same plane. The auxiliary block 6 is formed to be approximately the same as or slightly thinner than the width of the substrate 1, and is fixed on the optical waveguide 2.
The end face of the auxiliary block 6 is substantially parallel to the end faces of the substrate 1 and the optical waveguide 2, but is slightly recessed by being fixed to the end faces with a step. The end face of the optical fiber 3 is in close contact with the end face of the optical waveguide 2 and is fixed by a first adhesive 8. Auxiliary block 6 and cylindrical body 7
Is used to enlarge the bonding area when bonding the substrate 1 and the optical fiber 3 with the second adhesive 9.

Next, the connection method according to the present invention will be described in detail. 3A to 3I show a procedure of a method of connecting the optical waveguide 2 and the optical fiber 3 shown in FIGS. 1 and 2, and FIGS. 3A and 3B fix an auxiliary block to a substrate. Steps (c) to (f) are steps until the first adhesive is applied to the end faces of the optical waveguide and the optical fiber, and (g) to (g).
(I) shows a process until the optical waveguide and the optical fiber are connected.

First, an auxiliary block 6 made of the same material as the end face of the optical waveguide 2 and the substrate 1 is placed on an auxiliary block 6 substantially parallel to the end faces of the substrate 1 and the optical waveguide 2 and, for example, 10 to 20 mm.
The substrate 1 and the optical waveguide 2 are mounted on the optical waveguide 2 with being retracted from the end faces of the optical waveguide 2 so as to form a step (a).
(B). Since the step is provided, the position of the end face of the optical waveguide 2 can be directly viewed from above with a microscope or the like, and the workability is improved.

Next, the sheath 5 of the optical fiber 3 is peeled off, and the bare optical fiber 3 is broken at an appropriate length. It is fitted to a certain portion (c). The end face of the optical fiber 3 is locally heated by, for example, arc discharge, and is slightly melted and cleaned (d, e). In addition, 11 is an electrode for arc discharge, 1
2 is an arc discharge. For example, a UV-curable first adhesive 8 is applied to the end surface of the cleaned optical fiber 3 (f). The breakage of the optical fiber 3 can be achieved at a lower cost and a clean surface as compared with polishing or the like. The unevenness of the end face of No. 3 can be reduced. Here, the order of the mounting step (c) of the tubular body 7 and the steps (d, e) by arc discharge may be reversed.

Next, the end face of the optical waveguide 2 and the end face of the optical fiber 3 are brought close to each other to face each other, adjusted so as to obtain a desired coupling state, and irradiated with ultraviolet light 13 to irradiate the optical fiber 3 and the optical waveguide 2 with each other. (G). Next, the cylindrical body 7
Is moved to the optical waveguide 2 so as to be in close contact with the end face of the substrate 1 (h). For example, an ultraviolet-curable second adhesive 9 is filled in the gap between the auxiliary block 6 and the cylindrical body 7 and irradiated with ultraviolet rays 14. Thus, the optical fiber 3, the substrate 1, the optical waveguide 2,
The auxiliary block 6 and the cylindrical body 7 are integrally joined (i).

Here, the end face of the optical waveguide 2 and the optical fiber 3
Since the first adhesive 8 is surely filled between the cylindrical body 7 and the end surface of the cylindrical body 7, no air layer is generated when the cylindrical body 7 is fixed. However, the end face of the optical waveguide 2 and the auxiliary block 6
When the step of the end face of is set to exceed 200 μm,
The shrinkage of the second adhesive 9 at the time of curing may cause the optical fiber 3 to be misaligned.

Further, at the time of adjusting the joining of the optical waveguide 2 and the optical fiber 3 (g), the cylindrical body 7 can be arranged far away from the end face of the optical fiber 3, so that the optical fiber 3 Does not bend or vibrate due to its own weight and a small amount of the first adhesive 8.

The first adhesive 8 has a viscosity (for example, 10 to 100 cp) that can be applied in a small amount to the end face of the optical fiber 3.
s) It is necessary that the material be high in transmittance at the wavelength used and have good matching of the refractive index with the optical fiber 3 and the optical waveguide 2. On the other hand, the second adhesive 9 needs to have high adhesive strength to the optical fiber 3, the auxiliary block 6, and the substrate 1, and to have a thermal expansion coefficient close to those of these materials. That is, since the properties required for the respective adhesives 8 and 9 are different, the optimum one can be selected.

Here, an example in which the curing treatment is ultraviolet irradiation is shown. However, in consideration of workability, adhesive strength, and the like, an adhesive capable of being subjected to curing treatment such as visible light curing or heat curing is used. Is also good. For example, the first adhesive 8 may be of an ultraviolet curing type, and the second adhesive 9 may be of a thermosetting type.

If the auxiliary block 6 is made of the same material as the substrate 1 or a material having a similar thermal expansion coefficient, the substrate 1 is less likely to warp even if a thermal fluctuation occurs. For example, as the substrate 1, LiNbO ₃ (α = 0.8 to 1.5 × 10 ⁻⁵ (1 / °)
C)), FKO ₃ ((α = 1.4
× 10 ⁻⁵ (1 / ° C.)) can be used. However, in a limited temperature range, the thermal expansion coefficients may be different. In addition, even if the thickness or the width of the substrate 1 is small, if the size of the auxiliary block 6 is appropriately selected with respect to the size of the cylindrical body 7, the connection can be performed in a similar process.

Although the example of quartz glass has been given as the cylindrical body 7, a second material such as BK-7 glass or Pyrex glass can be used.
What is necessary is to use a material having a sufficient transmittance for ultraviolet rays used when the adhesive 9 is cured. The shape and size of the hole of the cylindrical body 7 through which the optical fiber 3 is inserted may be cylindrical or conical, larger than the outer diameter of the optical fiber 3, and the cylindrical body 7 is connected to the end face of the optical waveguide 2. First, cured first
Any size and shape may be used so that they can be approached without being hindered by the adhesive 8.

FIGS. 4 (a) and 4 (b) are views showing work steps until an auxiliary block is fixed to a substrate by another connection method of the present invention. In this connection method, the end face of the auxiliary floc 6 is slightly projected from the end faces of the substrate 1 and the optical waveguide 2. Subsequent working steps are shown in FIGS.
This is the same as the work process shown in (i).

In a material in which the substrate 1 is easily broken, for example, a semiconductor substrate which is easily cleaved such as InP or GaAs,
When the end face of the optical fiber 3 and the end face of the optical waveguide 2 are in direct contact as shown in FIG. 3 (g), the end face of the optical waveguide 2 is easily chipped.
However, in the process shown in FIG. 4, the end face of the optical fiber 3 does not directly contact the end face of the optical waveguide 2.
The end face of the optical waveguide 2 is not chipped.

In the above-described embodiment, an example of arc discharge is shown as a local heating treatment of the end face of the optical fiber 3. However, a heating treatment using a micro burner, a laser heating treatment, an infrared heating treatment, or the like may be performed. Good.

[0025]

As described above, according to the method for connecting an optical waveguide to an optical fiber according to the present invention, a step is provided between the end surface of the optical waveguide formed on the substrate and the end surface of the auxiliary block to connect the optical fiber to the optical waveguide. Since the connection is made, the substrate, the optical fiber, the auxiliary block, and the tubular body can be connected reliably and with sufficient adhesive strength, and the workability can be improved.

In addition, since the end face of the optical fiber is subjected to heat treatment such as arc discharge at the time of connection, the end face of the optical fiber can be cleaned and burrs can be removed, and the bonding strength can be increased.

Further, since the auxiliary block is made of the same material as the substrate material or a material having a similar thermal expansion coefficient, there is little warping of the substrate due to temperature fluctuation, and the adhesive does not peel.

Further, the first adhesive is cured by irradiation with visible light or ultraviolet light, and the first body is made of the first adhesive.
Is a material having a sufficient amount of visible light or ultraviolet light to be hardened to cure the adhesive, so that there are advantages in that sufficient adhesive strength can be ensured and workability is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of an optical waveguide and an optical fiber connected by a connection method according to the present invention.

FIG. 2 is a sectional view.

FIG. 3 shows a procedure of a method of connecting an optical waveguide and an optical fiber, wherein (a) and (b) show steps until an auxiliary block is fixed to a substrate, and (c) and (f) show optical waveguide and an optical fiber. Steps until the first adhesive is applied to the end face of (g),
(I) is a diagram illustrating a process until a light guide is connected to an optical fiber.

FIGS. 4A and 4B are diagrams showing work steps until an auxiliary block is fixed to a substrate according to another connection method of the present invention.

FIG. 5 is a perspective view of an optical waveguide and an optical fiber connected by a conventional connection method.

FIG. 6 is a sectional view.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Optical waveguide, 3 ... Optical fiber, 4 ... Optical fiber core, 5 ... Optical fiber jacket, 6 ... Auxiliary block, 7 ... Cylindrical body, 8 ... First adhesive, 9 ... Second adhesive, 10 ... third adhesive, 11 ... electrode for arc discharge, 1
2 ... arc discharge, 13 ... ultraviolet rays for curing the first adhesive, 14 ... ultraviolet rays for curing the second adhesive, 15 ... polishing grinder, 16 ... fixing the optical fiber and the cylindrical body Adhesive, 17 ... adhesive.

Claims (7)

[Claims] 1. A method for connecting an optical waveguide formed near the surface of a substrate to an end face of an optical fiber, comprising: placing an auxiliary block on the optical waveguide such that the end face of the auxiliary block and the end face of the optical waveguide are substantially parallel and a step is formed. An optical waveguide and an optical fiber, wherein the end face of the optical fiber coated with an adhesive is brought into contact with the end face of the auxiliary block or the end face of the optical waveguide, and then the adhesive is cured. Connection method. 2. The method for connecting an optical waveguide to an optical fiber according to claim 1, wherein a step between the end face of the auxiliary block and the end face of the optical waveguide is 200.
A method for connecting an optical waveguide and an optical fiber, wherein the distance is set within μm. 3. The method for connecting an optical waveguide to an optical fiber according to claim 1, wherein the auxiliary block is made of the same material as the substrate material or a material having a thermal expansion coefficient similar to that of the substrate material. Characteristic connection method between optical waveguide and optical fiber. 4. A method for connecting an optical waveguide formed near the surface of a substrate to an end face of an optical fiber, comprising: providing a cylindrical body having a hollow hole larger than a cladding diameter;
An optical fiber is inserted into the hollow hole, the optical fiber is moved to a position immediately adjacent to the outer cover of the optical fiber, a first adhesive is applied to the end face of the optical fiber, and the end face of the optical waveguide is opposed to the end face of the optical fiber. After adjusting the position between the end face of the optical waveguide and the end face of the optical fiber so that the optical output has desired characteristics, the first adhesive is cured, and the end face of the optical waveguide and the end face of the optical fiber are joined. A method for connecting an optical waveguide and an optical fiber, comprising bringing the tubular body into contact with an end face of the optical waveguide or an auxiliary block, filling and curing a second adhesive, and joining the cylindrical body and the optical fiber. 5. The method of connecting an optical waveguide to an optical fiber according to claim 4, wherein a heating process such as arc discharge is performed on an end face of the optical fiber before applying the first adhesive. How to connect the optical path with the optical path. 6. The method of connecting an optical waveguide to an optical fiber according to claim 4, wherein the first adhesive is cured by irradiation with visible light or ultraviolet light. Connection method. 7. The method for connecting an optical waveguide and an optical fiber according to claim 4, 5 or 6, wherein the cylindrical body has a visible light or ultraviolet light transmission amount sufficient to cure the second adhesive. A method for connecting an optical waveguide and an optical fiber, characterized in that: