JPH05303025A - Connecting structure for optical waveguide and optical fiber - Google Patents

Abstract

PURPOSE:To miniaturize a device and to improve reliability by directly mounting an optical fiber to a waveguide substrate by adhesive agent. CONSTITUTION:A first groove 21 is formed in the roughly vertical direction against a linear optical waveguide 12, and the end face of the optical waveguide 12 is exposed on the wall surface for forming this first groove 21. A second groove 22 for mounting an optical fiber 18 is formed in the roughly vertical direction against a first groove 21, that is, in the same direction as the optical waveguide 12. The optical fiber 18 is mounted in a second groove 22 so as to adhere closely to an optical signal incident end face, and in such a state, a second groove 22 is filled with an adhesive agent. Accordingly, optical and mechanical connection of the optical waveguide 12 and the optical fiber 18 is maintained stably, and there is no fear of causing a peeling-off in the connecting part. Also, since a thermal expansion coefficient of a waveguide substrate 11 and a thermal expansion coefficient of the optical fiber 18 are about the same, even if this phase modulator is used in the environment in which a temperature fluctuation is large, it is not feared that the optical coupling efficiency in the connecting part deteriorates.

Description

Relates connecting structure DETAILED DESCRIPTION OF THE INVENTION Outline optical waveguide and an optical fiber, reduction in size and the purpose of improving reliability, the waveguides such that the ends of the optical waveguide formed on the waveguide substrate is exposed A first groove is formed on the substrate, and a second groove is formed in a direction substantially perpendicular to the first groove, and the optical fiber is attached so that its end face is in close contact with the end of the optical waveguide. The second groove is mounted, and at least the second groove of the first groove and the second groove is filled with an adhesive.

TECHNICAL FIELD The present invention relates to a connection structure between an optical waveguide and an optical fiber.

 In the field of optical communication or optical transmission, various optical devices such as an optical switch and an optical coupler are used in addition to a transmitter, a receiver and an optical transmission line.

One of the forms of the optical device is a waveguide type. A waveguide-type optical device is configured to form an optical waveguide with a higher refractive index on the waveguide substrate and control the light beam while confining it inside the optical waveguide. In addition to the advantages that it is easy to mass-produce using planar technology, etc., it also has the advantage of being able to effectively apply an electric field or magnetic field and dramatically reducing power consumption. is doing. In practical use of such a waveguide type optical device, optimization of the connection structure between the optical waveguide and the optical fiber is being sought.

Prior Art FIG. 3 is a diagram showing a conventional optical waveguide / optical fiber connection structure. A waveguide type optical device 33 is placed and fixed on a substrate 31 via a spacer 32, and the optical waveguide 34 is connected to an optical fiber 35. The optical fiber 35 is held at its root by a fiber holder 37 via a covering material 36, and the fiber holder 37 is fixed to the substrate 31. The connection end of the optical fiber 35 is inserted and fixed in the ring 38. By bonding the ring 38 to the waveguide type optical device 33 with an adhesive, the optical waveguide 34 and the optical fiber 35 are optically and mechanically connected. Connection. Reference numeral 39 is a reinforcing plate provided at the edge of the waveguide type optical device 33.

Problems to be Solved by the Invention According to the conventional example shown in FIG. 3, since the bonding area is increased by using the ring 38, relatively strong connection is possible, but it is not suitable for holding optical fibers. There is a problem that the device becomes large because it requires a relatively large space. In addition, since the coefficient of thermal expansion of the substrate 31 and the coefficient of thermal expansion of the optical fiber, which are usually made of metal, are different, tensile stress acts on the connection part due to the temperature change of the operating environment of the device, and the connection part is separated There was a fear and there was a problem in terms of reliability. In addition, since the bare part of the optical fiber is exposed, there is a risk that the optical fiber may break or the connection part may peel off if some shock is applied to this exposed part. There was a problem.

 The present invention was created in view of such circumstances, and an object thereof is to provide a highly reliable connection structure between an optical waveguide and an optical fiber that can be downsized.

Means for Solving the Problems FIG. 1 shows the principle of the present invention.

 Reference numeral 1 is a waveguide substrate.

 Reference numeral 2 is an optical waveguide formed on the waveguide substrate 1.

 Reference numeral 3 is a first groove formed in the waveguide substrate 1 so that the end portion of the optical waveguide 2 is exposed.

 Reference numeral 4 is a second groove formed in a direction substantially perpendicular to the first groove 3.

 Then, at least the second groove 4 of the first groove 3 and the second groove 4 is mounted on the second groove 4 so that the end face of the optical fiber 5 is in close contact with the end portion of the optical waveguide 2. In this state, it is filled with an adhesive (not shown).

According to the connecting structure of the work for the present invention, it is possible to mount directly the optical fiber to the waveguide path substrate, miniaturization can be achieved as compared with the prior art. In addition, the optical fiber is fixed by filling the second groove with an adhesive, and the optical fiber is exposed only in the narrow first groove. There is no risk of breaking or peeling of the connection. Further, since the portion in which the second groove is formed and the waveguide substrate portion are integrally formed, for example, the thermal expansion coefficient of this integrated component and the thermal expansion coefficient of the optical fiber can be easily adjusted. They can be matched, and peeling of the connection part due to temperature change can be prevented.

It will be described with reference to the drawings an embodiment of implementation examples below the present invention.

FIG. 2 is a diagram showing the structure of a waveguide type phase modulator constructed by applying the present invention. Reference numeral 11 is a waveguide substrate made of, for example, lithium niobate (LiNbO ₃ ). An optical waveguide 12 is formed on the waveguide substrate 11 by thermally diffusing titanium (Ti), for example. Electrodes 13 and 14 are for applying an electric field to the optical waveguide 12, and are formed by depositing a metal on the surface of the waveguide substrate 11. Reference numeral 15 is a modulation signal generator connected to the input ends of the electrodes 13 and 14, and 16 is a terminating resistor connected to the output ends of the electrodes 13 and 14.

Reference numerals 17 and 18 denote optical fibers connected to the optical signal input side and output side of the optical waveguide 12, respectively. These optical fibers 17 and 18 are connected to optical connectors 19 and 20, respectively.

 Since the connection between the optical waveguide 12 and the optical fibers 17, 18 is the same on the optical signal input side and the output side, only the output side will be described. Reference numeral 21 is a first groove formed in a direction substantially perpendicular to the linear optical waveguide 12, and the end face of the optical waveguide 12 is exposed on the wall surface forming the first groove 21. The first groove 21 can be formed by, for example, a dicing saw, and its width is several 100 μm. Reference numeral 22 is a second groove for mounting the optical fiber 18, and the second groove 22 is formed in a direction substantially perpendicular to the first groove 21, that is, in the same direction as the optical waveguide 12. Since the second groove 22 needs to be opened to the first groove 21, it is desirable that the second groove 22 is formed by wet or dry etching. The width of the second groove 22 is such that the optical fiber 18 (for example, the diameter is 125 μm) is fitted.

 The optical fiber 18 is mounted in the second groove 22 so that the optical signal incident end face is in close contact with the optical signal emitting end face of the optical waveguide 12. In this state, the second groove 22 is not shown in the figure but an adhesive. Filled by. Therefore, the optical and mechanical connection between the optical waveguide 12 and the optical fiber 18 is stably maintained, and there is no risk of peeling at the connection portion. In this case, the adhesive may protrude from the second groove 22 to fill the first groove 21, but there is no problem because the adhesive protruding further contributes to the fixation of the optical fiber 18. ..

Further, since the thermal expansion coefficient of the waveguide substrate 11 and the thermal expansion coefficient of the optical fiber 18 are approximately the same, even if this phase modulator is used in an environment with large temperature fluctuations, the optical coupling at the connection part is also increased. There is no risk of efficiency loss.

EFFECTS OF THE INVENTION As described in detail above, according to the connection structure of the present invention, the optical fiber is directly attached to the waveguide substrate with an adhesive, which enables downsizing of the device and improvement of reliability. Has the effect of becoming.

[Brief description of drawings]

 FIG. 1 is a principle view of the present invention, FIG. 2 is a perspective view of a waveguide type phase modulator showing an embodiment of the present invention, and FIG. 3 is a view showing a conventional connection structure between an optical waveguide and an optical fiber. Is. 1, 11 ... Waveguide substrate, 2, 12 ... Optical waveguide, 3, 21 ... First groove, 4, 22 ... Second groove, 5, 17, 18 ... Optical fiber.

Claims (1)

[Claims] 1. An optical waveguide (2) formed on a waveguide substrate (1)
The first groove (3) is formed in the waveguide substrate (1) so that the end of the first groove (3) is exposed, and the second groove (4) is formed in a direction substantially perpendicular to the first groove (3). Then, the optical fiber (5) is attached to the second groove (4) so that its end face is in close contact with the end of the optical waveguide (2), and the first groove (3) and the second groove (4) are attached. A connection structure for a waveguide and an optical fiber, characterized in that at least the second groove (4) of the groove (4) is filled with an adhesive.