JPH03118501A - Optical coupling structure of optical fiber for optical waveguide - Google Patents

Abstract

PURPOSE:To offer the high-efficiency optical coupling structure by storing optical fibers as many as optical waveguides in array in optical fiber holding grooves in the groove depth direction and coupling the light incidence/projection end surfaces of the optical fibers with the end surfaces of the optical waveguides optically. CONSTITUTION:Block bodies 10 and 10 where the optical fiber holding grooves 28 and 28 are formed are adhered and mounted on block body mount parts 8 and 8 on both end sides of a base 2 with optical adhesives. The mutual isola tion distance D1 between the end surfaces of the optical waveguides 12 and 12 on a base plate 6 is equal to the distance D0 between the cores of the two optical fibers in an adjacency state, and the two optical fibers 20... are stored adjacently in the optical fiber holding grooves 28 and 28 of the block bodies 10 and 10 in the groove depth direction. The base plate 6 and block bodies 10 and 10 are only adhered and mounted on the substrate mount part 4 and block body mount part 8 of the base 2 with UV resin, etc., to couple the light incidence/projection end surfaces 30... of the optical fibers 20... with the end surfaces 16... of the optical waveguides 12 and 12 optically.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a substrate on which an end face of an optical waveguide formed on the surface thereof extends to the end face of the substrate, and a substrate in which one end face is tightly attached to the end face of the substrate. The end face of the optical fiber is positioned and fixed in a holding groove having a groove length from the above-mentioned end face to the other end face of the block body, and then the end face of the optical fiber is fixed. The present invention relates to an optical coupling structure of an optical fiber to an optical waveguide in which a light input/output end face on the side is optically coupled to an optical waveguide end face of the substrate end face.

(Prior art) There is an optical switch shown in Figs. 3 and 4 that is used in this type of optical fiber optical coupling structure [Material 4-1 of the 1985 National Conference of the Institute of Electronics and Communication Engineers]
23 1069r 2X2 Optical Switch Module Study”].

This optical switch requires single linear polarization excitation in order to efficiently operate a light guided switch using an anisotropic crystal, and requires fiber arraying for high integration. This was reported above as a 2×2 switch realized using a polarization maintaining optical fiber.

By the way, the substrate 02 used in the optical switch in the same figure is
It is made of stium niobate, has a rectangular shape in plan view, has a predetermined thickness, and has a pair of optical waveguides 04 and a comb-shaped electrode 06 on its surface.
are formed respectively. The intermediate portions of the optical waveguides 04 intersect with each other, and their end faces face both end faces of the substrate 02. The above-mentioned comb-shaped [! 06 is formed.

Then, one end surface of a block body is attached to each of both end surfaces of the substrate 02 in close contact with an optical adhesive, and each block body 08 has a pair of grooves each having a groove length from one end surface to the other end surface. A holding groove 010 having a V-shaped cross section is formed, and in each holding IFj 010, the end face of each optical fiber 012 is positioned and fixed with an optical adhesive. In this positioned and fixed state, the light input/output end face of each end face of each optical fiber 012 is optically coupled to the optical waveguide end face of the end face of the substrate.

Regarding the operation of an optical switch with such a structure,
Since this is well known, its explanation will be omitted.

(Problem to be Solved by the Invention) In the above optical switch, in order to obtain the accuracy of the switch operation, it is necessary to connect the optical fiber 01 on the left side in FIG.
In order for the light incident from the cladding 012a to be efficiently guided to the optical waveguide 04 without any loss and then efficiently emitted from the optical fiber 012 on the right side in the figure without any loss, a core 012b must be placed at the center of the cladding 012a. It is essential that the core 012h of the optical fiber 012 configured by inserting the core 012h is positioned with high precision on the end surface of the optical waveguide 04 facing the end surface of the substrate 02.

However, since the retainer 4010 is generally created by etching, its inner groove surface changes from the normal groove inner circumferential surface position shown by the broken line to the non-regular groove inner circumference shown by the solid line as shown in FIG. 5(a). It is often formed in a rough state as shown in the surface position, and the retaining groove 0 of the groove inner circumferential surface with such roughness
When the optical fiber 012 is positioned and fixed to the groove 10, the optical fiber 012 is deviated from its normal mounting position with respect to the inner peripheral surface of the groove.
There is a problem that the optical coupling efficiency between the optical waveguide 04 and the optical waveguide 04 is extremely deteriorated.

Furthermore, due to etching, the depth of the holding member 4010 tends to vary as shown in FIG. As a result, the optical coupling efficiency becomes non-uniform, which also causes the problem that the optical coupling efficiency is extremely deteriorated.

Therefore, an object of the present invention is to provide a structure that can optically couple the end face of an optical fiber and the end face of an optical waveguide with high efficiency.

(Means for Solving the Problems) In order to achieve such an object, in the optical coupling structure of an optical fiber to an optical waveguide of the present invention, at least two optical waveguides are formed, and each optical waveguide has a A substrate whose end face extends to the end face of the substrate and in which the separation distance between the end faces of adjacent optical waveguides matches the distance between the cores of two adjacent optical fibers, and a substrate that extends from the one end face to the other end face. A light beam having a groove length, whose groove depth matches the total outer diameter size of the same number of optical fibers as the optical waveguide, and whose groove width is approximately equal to the outer diameter size of a single optical fiber. a block body having a fiber holding groove, one end surface side of the block body is in close contact with the end surface of the substrate in a direction in which a groove depth direction of the optical fiber holding groove and a separation direction of the optical waveguides coincide. and,
In the optical fiber holding groove, the same number of optical fibers as the optical waveguides are housed in a line in the depth direction of the groove, and the light input/output end face of each optical fiber is aligned with the end face of each of the optical waveguides. It is characterized by being optically coupled to.

(Function) According to the above structure, the distance between the end faces of at least two optical waveguides formed on the substrate matches the distance between the cores of a plurality of optical fibers that are the same in number as the optical waveguides and are placed adjacent to each other. In this way, the same number of optical fibers as the optical waveguides are housed in a row in the mW direction in the optical fiber holding groove of the block, so just by bringing one end of the block into close contact with the end of the substrate. , the light input/output end faces of each optical fiber are reliably optically coupled to the end faces of each optical waveguide in a normal state.

(Example) Hereinafter, a coupling structure according to an example of the present invention will be described in detail as applied to an optical switch with reference to the drawings.

FIG. 1(a) is a perspective view showing the external appearance of an optical switch applied to the optical coupling structure of the end fiber to the optical waveguide according to the embodiment of the present invention, and FIG. ) is a vertical cross-sectional view of.

As will be explained with reference to these figures, in the coupling structure applied to the optical switch of this embodiment, the substrate mounting portion 4 is located at the center of the lithium niobate base 2 which is rectangular in plan view. A substrate 6 made of stium niobate and having a rectangular shape in a plan view smaller than the base 2 is adhesively mounted on each end of the base 2 using an optical adhesive such as an ultraviolet curable resin (UV resin). A block body 10.10 is also adhesively mounted on the block body mounting portions 8, 8 in the same way using an optical adhesive.

A pair of optical waveguides 12.12 and a comb-shaped electrode I4 are formed on the surface of the substrate 6, respectively.

Both end surfaces 16 of each of the optical waveguides 12, 12 on the substrate 6 extend to both end surfaces l818 of the substrate 6, and each optical waveguide 1 at both end surfaces l8I8 of the substrate 6
The mutual separation distance on both end faces I6... of 2.12 is the core 2 of two adjacent optical fibers 20...
2... Distance. is matched to

Optical fiber holders M28 and 28, which will be described later, are formed on each block mounting portion 88 at both ends of the base 2, and each block 10. IO is adhesively mounted with optical adhesive. This block body 10゜10 has block portions 10a and 1 in which optical fiber holders i28 and 28 are formed, respectively.
0a, and the optical fiber holding groove i#2 is attached to the optical fiber holding groove forming surface side of each block portion 10alOa.
Another block part 10b, 10 that closes 8.28
b are integrally constructed. In addition, in this embodiment, both block portions 10a, I Oa, 10b, I Ob
The optical fiber holder 12828 constitutes an optical fiber holding hole because it has an integral structure bonded with adhesive.The block portions] Ob and 10b are not necessarily essential in the present invention; The optical fiber holding groove referred to in the above-mentioned claims is not only constituted by both block parts IO or each block part 10a, 10a alone, but also by both block parts 10a, lOa, and +o.
This concept also includes the optical fiber holding hole in which b and tab are integrally formed from the beginning.

Each of the block bodies 10.10 has a groove length L extending from the end face 24 to the other end face 26, and has a groove depth H.
is the total outer diameter size of the two optical fibers 20 2 x D2
The block portion 10a, IO of which the optical fiber holding groove 28.28 is formed has a groove width W substantially equal to the outer diameter size D of the single optical fiber 20.
a is formed on one side 27 of each. and,
This block body 10.10 is in a state in which the one end surface side 24 is in close contact with the substrate end surface 18 in a direction in which the groove depth direction of the optical fiber holding groove 2828 and the separation direction of the optical waveguide 12.12 coincide. The optical fiber holding groove 28.2
Two optical fibers 20... are housed in a row in the depth direction of the groove, and each optical fiber 20...
... Each light input/output end face 30 corresponds to each optical waveguide 12.
It has a structure in which it is optically coupled to end surfaces 16 and 16 of 12, respectively.

In the above structure, each optical waveguide 12, 12 on the substrate 6
The mutual separation distance D1 between the end faces l- is the distance between the cores of two adjacent optical fibers. and two optical fibers 20... are stored adjacently in the groove depth direction in the optical fiber holding grooves 28, 28 of the block bodies to, to, so that the substrate mounting on the base 2 is By simply attaching the substrate 6 and the block bodies to and to on the placing part 4 and the block placing part 8 with UV resin, etc., each optical fiber 20... The output end faces 30... are optically coupled to the end faces 16... of each optical waveguide 12, 12, respectively.

In this embodiment, one end surface 24.24 of the block body 10.10 is brought into close contact with the substrate end surfaces 18, 18, and two optical fiber holding grooves 28.28 of the block body 10.10 are inserted.
By simply housing the optical fibers 20, respectively, the light input/output end faces 30 of each optical fiber 20 can be connected to the end faces 16 and 12 of the optical waveguides 12 and 12 formed on the substrate 6.
. . , each optical fiber 20 within the optical fiber holding groove 28° 28.
- The mutual separation distance can be kept constant, so that the optical fibers 20...each core 22... is always in a state facing the optical waveguide 12° 12, and the optical fiber 2
0... and the optical waveguides 12, 12 are improved.

In addition, the optical fiber holding i28, 2g is for each optical fiber 20.
. . are housed at the same time, the optical fiber holding grooves 28.
Since there is no variation in groove depth, which is a problem when the groove 28 is created, there is no unevenness in height when attaching the fibers to each other, which causes a decrease in the efficiency of optical coupling due to this variation.

FIGS. 2(a) to 2(C) are diagrams for explaining the procedure for creating the block body 10. First, FIG. 2(a)
A block piece 32 (the block portion 10a
(equivalent to). A concave groove 34 corresponding to the optical fiber holding groove is formed on one side of the block piece 32 using a cutting cutter or the like. Block piece 32
The two optical fibers 20.20 are inserted into the groove 34 in a row in the depth direction of the groove as shown in FIG. Glue and fix with resin. After inserting the optical fiber 20° 20, another block piece 36 (the block portion 10b) is inserted so as to close the groove 34 as shown in FIG.
The block body 10 of the present example is obtained by adhesively fixing the blocks (corresponding to the above) with the resin.

In this embodiment, two optical waveguides are formed on the substrate, and correspondingly two optical fibers are held in the optical fiber holding groove. When a waveguide is formed, it is preferable to hold a corresponding number of optical fibers in the optical fiber holding groove. Therefore, in this example, the number of optical waveguides formed on the substrate is 2. The number of optical fibers held in the optical fiber holding groove is not limited to two either.

(Effects of the Invention) As is clear from the above explanation, according to the present invention,
By simply adhering one end surface of the block body to the end surface of the substrate, the end surfaces of each optical fiber stored and held in the optical fiber holding groove of the block body are optically coupled to the respective end surfaces of each optical waveguide on the substrate. As a result, the optical fiber is prevented from being installed out of position in the optical fiber holding groove, and the optical coupling efficiency between the optical fiber end face and the optical waveguide end face is improved. In addition, unlike conventional block bodies, which have multiple optical fiber holding grooves that hold a single optical fiber, the structure is such that multiple optical fibers are held in a single optical fiber holding groove. It is possible to eliminate the problem of non-uniform heights when attaching optical fibers to each other due to variations in groove depth between the fiber holding grooves, and as a result, the efficiency of the optical coupling is improved.

As a result of the above, the present invention can provide a structure in which the end face of an optical fiber and the end face of an optical waveguide can be optically coupled with high efficiency.

[Brief explanation of drawings]

1 and 2 relate to one embodiment of the present invention, FIG. 1(a) is an external perspective view showing the joint structure of the same embodiment, and FIG. 1(b) is the same as that of FIG. 1(a). The vertical cross-sectional views and FIGS. 2(a) to 2(C) are diagrams for explaining the procedure for making the block body. 3 and 5 relate to a conventional example, FIG. 3 is an external perspective view of an optical switch to which the conventional coupling structure is applied, and FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. FIGS. 5(a) and 5(b) are diagrams corresponding to FIG. 4 for explaining the problems of the conventional example, respectively. 2... Base, 4... Board rest, 6... Board, 8
...Block body placement part, lO...Block body, 12
... Optical waveguide, 16 ... Optical waveguide end surface, I8 ... Substrate end surface, 20 ... Optical fiber, 22 ... Core, 24
...One end surface of the block body, 26...The other end surface of the block body, 2
8... Optical fiber holding groove, 30... Optical fiber light input/output end face, D... Distance between cores, DI... Optical waveguide end face separation distance, D2... Outside of single optical fiber Diameter size, H... Groove depth of the optical fiber holding groove, W... Groove width of the optical fiber holding groove.

Claims (1)

[Claims] (1) At least two optical waveguides are formed, each end face of each optical waveguide extends to the end face of the substrate, and the distance between the end faces of adjacent optical waveguides is such that two optical waveguides are in an adjacent state. A substrate having a groove length that matches the distance between the cores of the fibers, a groove length extending from the one end surface to the other end surface, the groove depth matching the total outer diameter size of the same number of optical fibers as the optical waveguide, and a groove width has a block body having an optical fiber holding groove formed to have an outer diameter approximately equal to the outer diameter size of a single optical fiber, and one end surface side of the block body is aligned with the end surface of the optical fiber holding groove with respect to the end surface of the substrate. The groove depth direction and the separation direction of the optical waveguides are closely attached in the same direction, and the same number of optical fibers as the optical waveguides are housed in a line in the groove depth direction in the optical fiber holding groove. 1. An optical coupling structure of an optical fiber to an optical waveguide, wherein the light input/output end face of each optical fiber is optically coupled to the end face of each of the optical waveguides.