JPH02212805A - Method for coupling and fixing optical fiber and waveguide type optical parts - Google Patents

Abstract

PURPOSE:To stably maintain high optical coupling efficiency without using a matching wave by cooling a waveguide type optical part, a ferrule and a coupling member and obtaining the adhesive strength between an optical fiber and the exposed end face of the waveguide by utilizing the differences in the rate of shrinkage between these parts. CONSTITUTION:The waveguide type optical part 3 and the ferrule 2 are so held that the end face of the optical fiber 1 comes into tight contact with the exposed end face of the waveguide 4 of the waveguide type optical part 3. The coupling member 5 having the coefft. of linear thermal expansion larger than the coefft. of linear thermal expansion of the waveguide type optical part 3 and the ferrule 2 as well as the waveguide type optical part 3 and the ferrule 3 are heated to fix both ends of the coupling member 5 to the side faces of the waveguide type optical part 3 and the ferrule 2. The waveguide type optical part 3, the ferrule 2 and the coupling member 5 are cooled to obtain the adhesive strength between the optical fiber 1 and the exposed end face of the waveguide 4 by utilizing the differences in the rate of shrinkage between these members. The high optical coupling efficiency is stably maintained in this way without using the matching liquid.

Description

[Detailed Description of the Invention] Summary Regarding a method for coupling and fixing optical fibers and waveguide type optical components, the present invention relates to a method for coupling and fixing optical fibers and waveguide type optical components, which can stably maintain high optical coupling efficiency without using a matching liquid. For the purpose of providing a coupling and fixing method, the end face of a ferrule into which an optical fiber is inserted and fixed is polished into a spherical shape, and the waveguide type optical component is polished so that the end face of the optical fiber is in close contact with the exposed end face of the waveguide of the waveguide type optical component. Holds the optical component and the above ferrule,
While heating the coupling member having a linear thermal expansion coefficient larger than that of the waveguide-type optical component and the ferrule, and the waveguide-type optical component and the ferrule, both ends of the coupling member are connected to the waveguide-type optical component and the ferrule. It is fixed to the side surface of the optical component and the ferrule, cools the waveguide-type optical component, the ferrule, and the coupling member, and uses the difference in the amount of contraction of these components to obtain adhesion between the optical fiber and the exposed end surface of the waveguide. and configure it.

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for coupling and fixing an optical fiber and a waveguide type optical component.

In the field of optical communication or optical transmission, waveguide type optical components are used in addition to bulk type optical components in which optical system components such as lenses are fixedly held on a board. Waveguide-type optical components are structured so that a guiding waveguide with a higher refractive index is formed on the waveguide substrate, and the light beam is controlled while being confined within this guiding waveguide, making it possible to reduce the size of the structure. is easy,
In addition to the advantage that mass production is possible, it has the advantage that electric and magnetic fields can be effectively applied, so power consumption can be dramatically reduced.

When putting such waveguide-type optical components into practical use, optimization of the method for coupling and fixing them with optical fibers is being sought.

Conventional technology When optically coupling an optical fiber and a waveguide type optical component,
If the end face of the optical fiber and the end face of the waveguide are simply brought close to each other, an air layer with a low refractive index will exist between the high refractive index optical fiber and the waveguide, which will increase the loss due to Fresnel reflection loss and cause the cavity effect. The above loss is not stable depending on minute fluctuations in the gap. For this reason, conventionally, as shown in FIG. 5, the end face of the waveguide 32a of the waveguide type optical component 32 mounted and fixed on the substrate 31 and the end face of the optical fiber 33 are made to face each other, and optical adhesive is bonded between them. A matching liquid 34 having a refractive index substantially equal to that of the optical fiber and waveguide is interposed to prevent the increase and fluctuation of the loss. In the figure, 36 is a block fixed on the substrate 31, and 35 is solder for fixing the optical fiber 33 on the surface of which a metal thin film (not shown) is formed to the block 36.

Problems to be Solved by the Invention As described above, in the conventional technology, it was necessary to use a matching liquid in order to stably maintain high optical coupling efficiency, but there was a problem that the reliability of the matching liquid was not necessarily high. there were. For example, if a matching liquid is placed in the same airtight block as an optical semiconductor element such as an LD (semiconductor laser), gas evaporated from the matching liquid may have an adverse effect on the optical semiconductor element.

The present invention was created in view of the above circumstances, and it is an object of the present invention to provide a method for coupling and fixing optical fibers and waveguide type optical components, which can stably maintain high coupling efficiency without using a matching liquid. The purpose is

Means to solve problems FIG. 1 is a diagram showing the principle of the present invention.

2 is a ferrule into which the optical fiber 1 is inserted and fixed;
Its end face is polished into a spherical surface. Reference numeral 4 denotes a waveguide of a waveguide type optical component 3 to be optically coupled to the optical fiber 1.

5 is a coupling member having a linear thermal expansion coefficient larger (first method) or smaller (second method) than the waveguide type optical component 3 and the ferrule 20.

In the first method of the present invention, the waveguide type optical component 3 and the ferrule 2 are held so that the end surface of the optical fiber 1 is in close contact with the exposed end surface of the waveguide 4 of the waveguide type optical component 3, and the waveguide type optical component 3
The coupling member 5 having a linear thermal expansion coefficient larger than the linear thermal expansion coefficient of the ferrule 20, the waveguide type optical component 3, and the ferrule 2 are heated to connect both ends of the bonding material 5 to the waveguide type optical component 3 and the ferrule. The waveguide-type optical component 3, ferrule 2, and coupling member 5 are fixed to the side surface of the optical fiber 1 and the exposed end surface of the waveguide 4 is cooled, and the difference in the amount of contraction of these components is utilized to obtain adhesion between the optical fiber 1 and the exposed end surface of the waveguide 4. ing.

In addition, in the second method of the present invention, the waveguide type optical component 3 and the ferrule 2 are held so that the end surface of the optical fiber 1 is in close contact with the exposed end surface of the waveguide 4 of the waveguide type optical component 3, The coupling member 5 having a linear thermal expansion coefficient smaller than that of the component 3 and the ferrule 2, the waveguide-type optical component 3, and the ferrule 2 are cooled, and both ends of the coupling member 5 are connected to the waveguide-type optical component 3. and fixed to the side surface of the ferrule 2, and heats the waveguide-type optical component 3, the ferrule 2, and the coupling member 5, and uses the difference in the amount of expansion of these components to obtain adhesion between the optical fiber l and the exposed end surface of the waveguide 4. That's what I do.

Working waveguide type optical component 30 linear thermal expansion coefficient α4, ferrule 2
The zero-line thermal expansion coefficient is α2, the waveguide type optical component 3 and the coupling member 5
The distance from the fixed part to the close contact part of waveguide 4 and optical fiber 1! 9. The distance from the close contact part of the waveguide 4 and optical fiber 2 to the fixed part of the ferrule 2 and coupling member 5 is 12
, when the linear thermal expansion coefficient of the coupling member 50 is α, in the first method of the present invention, the linear thermal expansion coefficient of the coupling member 50 is larger than the linear thermal expansion coefficient of the waveguide type optical component 3 and the ferrule 20. It is defined as satisfying the expression it +Ilt. By satisfying this condition, after heating the coupling member 5, waveguide type optical component 3, and ferrule 2 and fixing both ends of the coupling member 50 to the side surfaces of the waveguide type optical component 3 and ferrule 2,
By cooling these to an appropriate operating temperature of the optical component (for example, room temperature), an appropriate adhesion force can be obtained between the optical fiber 1 and the exit end surface of the waveguide 4i1. When the optical fiber 1 and the exposed end face of the waveguide 4 are in close contact, there is no air layer between them, which prevents loss increase and fluctuation, and maintains high optical coupling efficiency stably without using a matching liquid. can do.

Furthermore, in the second method of the present invention, the linear thermal expansion coefficient of the coupling member 5 is smaller than the linear thermal expansion coefficients of the waveguide type optical component 3 and the ferrule 2 because the following equation is satisfied. Define that there is. If this condition is satisfied, after cooling the coupling member 5, waveguide-type optical component 3, and ferrule 2 and fixing both ends of the coupling member 50 to the sides of the waveguide-type optical component 3 and ferrule 2, By heating the optical component to an appropriate operating temperature (for example, room temperature), an appropriate adhesion force can be obtained between the optical fiber 1 and the exposed end surface of the waveguide 4, which is based on the same principle as the first method of the present invention. The purpose is achieved.

"L" 1-Male Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention, and is a plan view of an optical fiber and a waveguide type optical component that are coupled and fixed by the method of the present invention, and FIG. 3 is a side view thereof. Reference numeral 12 denotes a ferrule in which the optical fiber 11 is inserted and fixed in its central pore, and the end surface of the ferrule 12 is polished into a spherical surface. In order to fix the optical fiber 11 to the ferrule 12, a film of a solderable metal such as Au is formed by vapor deposition on the surface of the ferrule 12 made of, for example, SUS material and the surface near the tip of the optical fiber 11, and then soldered. This can be done by

The waveguide type optical component 13 is constructed by closely fixing a waveguide substrate 15 on which a waveguide 14 is formed onto a carrier 16 made of metal such as SUS material or Kovar. Reference numeral 17 indicates a coupling member whose both ends are fixed to the side surfaces of the carrier 16 and the ferrule 12, respectively, by laser welding, and 18 indicates a temporary fixing member for temporarily fixing the ferrule 12 to the carrier 16 before the coupling member 17 performs the coupling. It is a stop member.

In the case of the first method, the material for the coupling member 17 is selected to have a linear thermal expansion coefficient larger than that of the carrier 16 and the ferrule 120. When the carrier 16 and the ferrule 12 are made of SUS material, since the linear thermal expansion coefficient of the SUS material is 16.4 A coupling member 17 can be formed from X 10-@). Then, prior to heating the entire ferrule 12, the ferrule 12 is fixed to, for example, a fine movement table (not shown), and the end surface of the optical fiber 11 is brought into close contact with the exposed end surface of the waveguide 14. The carrier 16 and the ferrule 12 are temporarily fixed by the temporary fixing member 18. In this case, the temporary fixing member 18 It is desirable that the linear thermal expansion coefficient of the ferrule 12 and the carrier 16 be approximately equal to that of the ferrule 12 and the carrier 16.Next, the entire body is heated, for example, in a heating furnace, and both ends of the coupling member 170 are bonded to the carrier 16 and the ferrule, respectively. After it is fixed to the side surface of 12 by laser welding or the like, it is cooled to a normal use temperature (for example, room temperature).

At this time, the amount of contraction of the coupling member 17 due to cooling is larger than the amount of contraction of the ferrule 12 and the carrier 16 between the fixed parts with the coupling member 17, so the optical fiber 1
An appropriate adhesion force is generated between the end faces of the waveguide 1 and the waveguide 14. Therefore, if the heating temperature is set to a temperature higher than the upper limit of the operating temperature range of the optical component, the end faces of the optical fiber 11 and the waveguide 14 can be brought into close contact with each other at all times within the operating temperature range. No voids are created between them, and high optical coupling efficiency can be stably maintained. The adhesion force between the end surfaces can be expressed as P=E1ΔT(αJ×αS)/S, where this pressure is P. Here, S is the contact area between the ferrule and the waveguide (fiber cross section 1), and E is the ferrule (
Young's modulus of SUS material)! is the distance between welding points fi(5+a
+s), ΔT is the temperature difference (50°C), α is the coefficient of linear thermal expansion of the joining member (brass), α.

is carrier 16 (SUS material) and ferrule 12 (SUS material)
This is the linear thermal expansion coefficient of the US material), and when P is calculated using the values exemplified for each, P = 1.2X10'
(N/rn').

Note that if the entire heating can be performed with the end face of the optical fiber 11 and the exposed end face of the waveguide 14 in close contact with each other, temporary fixing by the temporary fixing member 18 is not necessary.

In the second method, a material having a linear thermal expansion coefficient smaller than that of the ferrule 12 and the carrier 16 is used as the material for the coupling member 17 . In the first method, the end faces of the optical fiber 11 and the waveguide 14 are cooled at the parts to be heated, heated at the parts to be cooled, and expanded at the parts to be contracted at the working temperature of the optical component. They can be brought into good contact with each other, and high optical coupling efficiency can be stably maintained.

By the way, in the above embodiment, when a coupling member having a large Young's modulus is used to couple the ferrule 12 and the carrier 16 with a high coupling force, the adhesion force between the end faces of the optical fiber 11 and the waveguide 14 becomes significantly large. , it may cause damage right to the close contact part. In such a case, as shown in FIG.
1 may be used to impart spring properties to the coupling member 21 in the optical axis direction, that is, to substantially reduce the bending ratio of the coupling member 21 in the optical axis direction, thereby preventing the above-mentioned damage. .

Effects of the Invention As explained above, according to the present invention, it is possible to stably maintain high optical coupling efficiency without using a matching liquid.

[Brief explanation of the drawing]

FIG. 1 is a diagram of the principle of the present invention, FIG. 2 is a diagram of an embodiment of the present invention, and is a plan view of an optical fiber and a waveguide-type optical component coupled and fixed by the first method of the present invention. 4 is a side view of the same, FIG. 4 is a plan view of an optical fiber and waveguide type optical component coupled and fixed by the second method of the present invention, and FIG. 5 is a plan view of a conventional optical component. It is an explanatory diagram. 1.1 2, 1 3.1 4, 1 5.1 1... Optical fiber, 2... Ferrule, 3... Waveguide type optical component, 4... Waveguide, 7.21...・Connection member.

Claims (2)

[Claims] (1) Ferrule into which the optical fiber (1) is inserted and fixed (
The end face of the optical fiber (2) is polished into a spherical shape, and the end face of the optical fiber (1) is brought into close contact with the exposed end face of the waveguide (4) of the waveguide type optical component (3). A coupling member (5) that holds the ferrule (2) and has a linear thermal expansion coefficient larger than that of the waveguide type optical component (3) and the ferrule (2) and the waveguide type optical component ( 3) and the ferrule (2) are heated, both ends of the coupling member (2) are fixed to the side surfaces of the waveguide type optical component (3) and the ferrule (2), and the waveguide type optical component ( 3) The ferrule (2) and the coupling member (5) are cooled, and the difference in the amount of contraction thereof is used to obtain adhesion between the optical fiber (1) and the exposed end surface of the waveguide (4). A method for coupling and fixing an optical fiber and a waveguide type optical component, characterized by the following. (2) Ferrule into which the optical fiber (1) is inserted and fixed (
The end face of the optical fiber (2) is polished into a spherical shape, and the end face of the optical fiber (1) is brought into close contact with the exposed end face of the waveguide (4) of the waveguide type optical component (3). A coupling member (5) that holds the ferrule (2) and has a linear thermal expansion coefficient smaller than that of the waveguide-type optical component (3) and the ferrule (2) and the waveguide-type optical component ( 3) and the ferrule (2) are cooled, both ends of the coupling member (5) are fixed to the side surfaces of the waveguide type optical component (3) and the ferrule (2), and the waveguide type optical component ( 3) The ferrule (2) and the coupling member (5) are heated to utilize the difference in the amount of expansion of these to obtain adhesion between the optical fiber (1) and the exposed end surface of the waveguide (4). A method for coupling and fixing an optical fiber and a waveguide type optical component, characterized by the following.