JPH05303023A - Connecting structure between optical waveguide element and optical fiber - Google Patents

Abstract

PURPOSE:To realize the connecting structure for securing optical axis alignment of high accuracy, and simultaneously, improving productivity and reliability, at the time of connecting an optical waveguide element and an optical fiber. CONSTITUTION:In a circular metallic pad 20 of an end face of an optical waveguide element 10, spherical projection solder 17 called a solder bump is formed, a circular metallic pad 21 of an end face of an optical fiber terminal 13 is adhered through this bump, and by a self-alignment action by surface tension of molten solder, an optical waveguide 12 and an optical fiber 14 can be coupled by non-adjustment. In such a way, by forming the metallic pad 21 to a circle being the same shape as a cross section of the spherical solder bump, the bump without a variance can be formed with good reproducibility and with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for connecting an optical waveguide terminal to an optical fiber terminal which constitutes an optical communication module for modulating light waves and switching optical paths in optical communication and the like.

[0002]

2. Description of the Related Art Practical application of optical communication systems has progressed, and development has been advanced into more advanced systems having large capacity and multiple functions. New functions such as a switching function of an optical transmission line network, a high-speed connection between terminals in an optical data bus, and a switching function are required, and an optical communication network that enables them is required more and more.

In the realization of optical transmission having such a large capacity and a wide band, for example, an optical switch currently in practical use mechanically moves a prism, a mirror, a fiber, etc., and is low speed. However, there are drawbacks such as insufficient reliability, large shape, and unsuitable for matrix formation. What is being developed as a means to solve this is a waveguide type optical switch that uses an optical waveguide installed on a substrate, and has features such as high speed, multi-element integration, and high reliability. . In particular, the one using a ferroelectric material such as LinbO ₃ crystal is characterized by high efficiency because it has small light absorption and low loss and has a large electro-optical effect. It is expected to be applied to fields such as exchange.

In the connection between such a waveguide type optical device and an optical transmission network, it is required that the optical fiber is stable with respect to environmental changes such as temperature changes and has a small optical loss. Therefore, between the optical waveguide and the optical fiber. Positioning and fixing with high precision (1 to 10 μm) are required, and the simplest structure is realized by butting the end face of the optical waveguide and the end face of the optical fiber.

Conventionally, there is a connection structure of this kind of optical waveguide element and an optical fiber as shown in FIG. Figure 3
FIG. 3A is a perspective view of a waveguide element and an optical fiber connected by a conventional connection structure. In FIG. 3A, an optical waveguide element 30 is one in which an optical waveguide 22 is formed on a substrate 21, and a holding block, that is, an optical fiber 24 arrayed in an optical fiber terminal 23 is adjusted by optical axis adjustment. The optical fiber terminal 23 is fixed to the substrate 21 with an adhesive 25 such as a UV curable resin while keeping the state. As for the fixing method, there are solder welding and laser welding in addition to the adhesive. Further, FIG. 3B is a perspective view showing a connection surface before connection of the optical waveguide device 10 and the optical fiber terminal 13 in another conventional example. A metal pad 16 of about several tens to several hundreds of μm square, which is paired with each end face,
18 is provided, a solder bump is formed on the metal pad 16, and the end face coupling between the optical waveguide device 10 and the optical fiber terminal 13 can be accurately adjusted through the bump without any adjustment.

[0006]

As described above, it is necessary to align and fix the optical waveguide element and the optical fiber terminal with high accuracy. However, the conventional optical axis adjusting and fixing methods are not suitable for those requiring long-term stability and are poor in productivity, because the positional deviation at the time of fixing and the change with time are large. Even when laser welding is used, the problem of requiring highly accurate optical axis adjustment cannot be solved. Further, in the bonding method using bumps, the bumps formed on the pads vary due to the difference in the shape of the bumps that are spheres (circles) and the pads are squares, which hinders highly accurate alignment.
In the future, it is expected that the optical device module will be required to have higher precision and lower optical loss, and the simplification of the optical axis alignment in optical mounting and the higher precision have become issues.

[0007]

A connection structure between an optical waveguide device and an optical fiber according to the present invention has a structure in which an end face of a plurality of optical waveguides formed in the optical waveguide device and a plurality of optical fibers arranged by a holding block. In the connection structure of the optical waveguide element and the holding block, the end surfaces of which are completely end-face-coupled, a plurality of sets of circular metal bats each forming a pair at the connection end surface of the optical waveguide element and the holding block. The metal pads are joined together using solder bumps.

[0008]

[Function] When a spherical bump solder called a solder bump is formed on a square metal pad, the solder bump flows in any of the four extra corners of the metal pad, and the height of the formed bump varies. By forming the pad into a circle having the same shape as the cross section of the bump, an extra portion of the metal pad can be removed, the flow of solder to the unnecessary pad portion can be suppressed, and a bump with almost no variation can be formed with high reproducibility and high accuracy. Therefore, highly accurate optical axis alignment in optical mounting is realized.

[0009]

FIG. 1 is a perspective view of an end of an optical fiber which is a holding block of an optical waveguide element and an optical fiber provided with a circular metal pad for a solder bump according to an embodiment of the present invention. Circular metal pads 20 and 21 forming a pair are formed on the end faces of the optical waveguide device 10 and the optical fiber terminal 13, respectively. A circular metal pad 20 having a diameter of several tens to several hundreds of μm and a solder bump 17 are formed on the end face of the optical waveguide element 10 having the optical waveguide 12 formed on the surface of the substrate 11. The metal material of the pad 20 differs depending on the material of the solder bump 17 used, but if it is Pbsn solder, it is C
Cr-Au may be used for r-Ni and AuSn solder. The height of the solder bump is preferably about several tens to several hundreds of μm. A circular metal pad 21 similar to the optical waveguide element is also formed on the end face of the optical fiber terminal 13 on which the optical fibers 14 are arranged. The positional relationship between the optical fiber 14 and the circular metal pad 21 matches the positional relationship between the optical waveguide 12 and the metal pad 20.

FIG. 2 is a process diagram when the optical waveguide device and the optical fiber terminal according to FIG. 1 are end-face-bonded to each other via solder bumps. First, as shown in FIGS. 2A to 2B, the optical fiber terminal 13 is temporarily connected to the optical waveguide device 10. Since the alignment at this time may be such that a part of the metal pad 21 on the end face of the optical fiber terminal 13 comes into contact with the solder bump 17, the highly accurate alignment required conventionally is not necessary. Next, when the bump 17 is melted, as shown in FIGS. 2C and 2D, the self-alignment between the optical waveguide 12 and the optical fiber 14 is automatically performed by the self-alignment effect due to the surface tension of the molten solder 19. Is done
Can be fixed at the same time.

Similar effects can be expected when the solder bumps 17 are formed on the metal pads 21 provided on the optical fiber terminal 13.

[0012]

As described above, according to the present invention, since the connecting metal pads provided on the end faces of the optical waveguide element and the optical fiber terminal are circular,
There is an effect that the optical axis alignment between the optical waveguide and the optical fiber can be maintained with high precision, and at the same time, the productivity and reliability of the connection can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical waveguide element and an optical fiber terminal before connection in an embodiment of the present invention.

FIG. 2 is a process drawing showing a connection process of FIG.

FIG. 3A is a perspective view showing a structure of a conventional example, and FIG. 3B is a perspective view showing a structure of another conventional example.

[Explanation of symbols]

 10 Optical Waveguide Element 11 Substrate 12 Optical Waveguide 13 Optical Fiber Terminal 14 Optical Fiber 15 Adhesive 16,18 Metal Pad 17 Solder Bump 19 Molten Solder 20,21 Circular Metal Pad

Claims (1)

[Claims] 1. The optical waveguide device, wherein the end faces of a plurality of optical waveguides formed in the optical waveguide device and the end faces of a plurality of optical fibers arranged by a holding block are completely end face-coupled to each other. In the connection structure with the holding block, a plurality of sets of circular metal butt forming a pair are provided on the connection end faces of the optical waveguide element and the holding block, and the metal pads are joined together by using solder bumps. Connection structure between optical waveguide device and optical fiber.