JP2570307B2 - Optical fiber connector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] An optical fiber connector with improved transmission characteristics and reduced connection man-hours at a connection point with an optical waveguide, which reduces connection loss and facilitates connection work with the optical waveguide. At least one optical fiber is fixed in an array with a holder, and the holder is cut along with the optical fiber so as to have a mirror-like cross section in a direction perpendicular to the optical fiber. The optical fiber is made to protrude from the holder cross-section by being etched away, and is positioned and joined to an optical waveguide of a separately provided guide.

[Industrial applications]

The present invention relates to an optical fiber connected to an optical waveguide in an optical communication device, and more particularly to an optical fiber connector for improving transmission characteristics and reducing connection man-hours at a connection point with the optical waveguide.

In other words, a transmission line in optical communication usually includes a core made of high-purity transparent quartz and having a diameter of about 10 μm,
Using an optical fiber covered with a cladding (sheath) made of glass with a smaller refractive index than the core with an outer diameter of about 125 μm,
The optical fiber is connected to an optical waveguide device on a transmission / reception circuit to form a communication system.

However, the diameter of the optical waveguide on the device connected to the optical fiber is usually about the same as the core diameter of the optical fiber, and slight inclination and misalignment of the connection surface at the connection point between the optical fiber and the optical waveguide cause transmission loss. , Causing a decrease in transmission characteristics.

In this case, especially when the amount of information increases, the number of optical fibers required increases, and recently, a method of connecting optical fibers to an optical waveguide device by arraying the optical fibers is often used.

Accordingly, the present invention relates to a structure of an optical fiber connector that can easily and easily connect an optical fiber to an optical waveguide without transmission loss.

[Conventional technology]

As a holder for fixing an optical fiber, a silicon (Si) substrate that can be arrayed with high accuracy has been used.

That is, in general, when an Si single crystal is etched using a heating alkali etchant, the etching rate varies depending on the crystal orientation, so that anisotropic etching is performed. For example, when the crystal plane orientation is (100) or (110), the etching speed is very fast. However, when the crystal plane orientation is (111), the etching rate is extremely low. Irregularities are formed along the crystal orientation on the surface.

Therefore, an oxide film is formed by mask patterning on a Si single crystal wafer having a specific crystal plane orientation, a V-groove forming position is opened in a window, and then immersed in the above-mentioned etching solution to perform V-shaped anisotropic etching. A silicon substrate having a plurality of fine and parallel V-grooves can be formed on a single crystal wafer.

FIG. 4 is a cross-sectional structural view of a conventional optical fiber connector, FIG. 5 is a view showing a forming process of the conventional optical fiber connector, and FIG. 6 is a conceptual view of connection with an optical waveguide as a conventional optical fiber connector. Is shown.

In FIG. 4, an epoxy-based optical fiber 2 composed of a core 3 and a clad 4 is inserted into a square hole formed when the two silicon substrates 1a and 1b face each other so that the V grooves are aligned. The optical fiber 2 is fixed and integrated with an adhesive 5 and further cut in a direction perpendicular to the cross section of the optical fiber to form an end surface (the surface indicated by the arrow a) by plane polishing. Is exposed.

In FIG. 5, (A) is provided with a plurality of fine parallel V-grooves.
1 shows a silicon substrate 1a made of a Si single crystal.

Here, the epoxy fibers 5 are applied in such a manner that the optical fibers 2 are aligned and mounted in the plurality of V-grooves of the silicon substrate 1a and fill the gaps. This state is (B).

Here, (C) is a diagram in which the V-groove is aligned and the optical fiber 2 is sandwiched and fixed in such a manner that the same silicon substrate 1b as that of the above 1a is opposed. At this point, the end faces of the plurality of optical fibers do not need to be particularly aligned.

Further, at a preset position, a right-angle cross section of the V-groove of the optical fiber 2, that is, the silicon substrates 1a and 1b (arrows b to b 'shown in the figure).
(D) direction and the cut surface is polished flat to complete the optical fiber connector shown in (D).

In this case, the polished surface is exposed such that the cross sections of the plurality of optical fibers 2 and the Si crystal planes of the silicon substrates 1a and 1b are on the same plane.

FIG. 6 shows that a conventional optical fiber connector is bonded to a guide 10 having an optical waveguide 11 so that the core 3 of the optical fiber 2 and the optical waveguide 11 are aligned with each other.
FIG. 2 is a view showing a state where the adhesive is fixed and integrated with a curable epoxy adhesive 12.

Here, the optical waveguide 11 serving as a connection surface with the optical fiber connector is provided.
The end face of the guide 10 provided with a surface is usually polished in a direction perpendicular to the optical waveguide to expose the optical waveguide 11.

Therefore, the connection of the optical communication transmission line is completed by joining the optical fiber connector to the guide 10 and matching the position of the optical waveguide 11 with the core 3 of the optical fiber 2.

[Problems to be solved by the invention]

The optical waveguide connecting surface to be connected to the optical fiber connector is usually polished with a guide in a plane, and the diameter of the optical waveguide exposed on the polished surface is substantially the same as the diameter of the optical fiber core.

The connection surface of the optical fiber core connected to the optical waveguide is
The optical fiber connector is planar polished together with the Si crystal surface, and the core diameter exposed on the polished surface is 10 μm as described above.
It is about.

On the other hand, the size of the connection surface as an optical fiber connector is considered to be, for example, about 5 × 2 to 3 mm for four optical fibers.

Therefore, when connecting an optical fiber in units of μm and an optical waveguide, if the optical fiber connector polished surface or the optical waveguide polished surface is inclined or bonded with an inclination, the peripheral portion of the polished surface, that is, an optical signal In this case, there is a small gap between the core of the optical fiber and the optical waveguide, which increases the connection loss. For example, even if the inclination is one degree, the waveguide and the optical fiber core are separated by several tens of μm, and a connection loss occurs in this gap.

Further, regarding the positional deviation, in the case of the core diameter and the optical waveguide diameter described above, if the core deviation between the optical waveguide and the optical fiber is not suppressed to 0.5 μm or less, the connection loss sharply increases.

Therefore, conventionally, when connecting the optical fiber connector and the optical waveguide, in order to join and polish the polished surface of the optical fiber connector and the polished surface of the optical waveguide, using a mechanical means such as a fine movement dial. The two are bonded and fixed while being adjusted by man-hours to form a transmission line as a communication system.

However, this connection work is a major factor that hinders cost reduction, and there is a problem that transmission loss cannot be completely eliminated.

[Means for solving the problem]

The above problem is that a plurality of optical fibers are fixed to the holder,
Cutting the holder together with the plurality of optical fibers, forming a joint surface by selectively etching and removing the end of the holder so that end surfaces of the cut plurality of optical fibers protrude from the holder, A plurality of optical fibers and a plurality of optical waveguides formed on the optical waveguide substrate corresponding to the plurality of optical fibers are aligned, and an end surface of the aligned optical waveguide is exposed. The problem is solved by a method for connecting an optical fiber and an optical waveguide, wherein an end face and a bonding surface of the holder are bonded and fixed.
Similarly, the above problems include a plurality of optical fibers, a holder for holding the plurality of optical fibers, and an optical waveguide substrate on which a plurality of optical waveguides corresponding to the plurality of optical fibers are formed, The holder is held so that end faces of the plurality of optical fibers are arranged on the same plane and protrudes from the end face of the holder, and further joins the end face of the holder and the end face of the optical waveguide substrate. The problem is solved by the connection structure between the optical fiber and the optical waveguide, which is characterized by being fixed.

(Operation)

In the present invention, instead of the conventional connection between the polished surface of the optical fiber connector and the polished surface of the optical waveguide connection surface, only the polished tip connection surface of the protruding optical fiber is joined to the polished surface of the optical waveguide and connected. Is what you do.

This significantly reduces the contact area between the polished surfaces and eliminates the one-sided phenomenon of the fiber fixing portion such as the silicon substrate caused by the inclination of the polished surface, so that there is no gap between the optical waveguide and the optical fiber core. In addition, even when a gap occurs or when a misalignment is observed between the waveguide and the optical fiber core, since only the optical fiber protrudes, macroscopic observation with a microscope or the like from the side of the optical fiber becomes possible. Modification is extremely easy.

Furthermore, since the method of projecting the fiber by etching the holder of the optical fiber is used, it is possible to control the amount of minute projection of the fiber with good reproducibility by adjusting the etching time, etc., particularly after fixing the optical fiber to the optical waveguide. Temperature characteristics can be stabilized.

Therefore, when the optical fiber connector is connected to the optical waveguide, a connection that does not cause transmission loss and is stable in characteristics can be performed without increasing the number of steps.

〔Example〕

 The description will be made in order with reference to the accompanying drawings.

FIG. 1 is an external view of an optical fiber connector according to the present invention, FIG. 2 is a sectional structural view and a perspective view of the optical fiber connector according to the present invention, and FIG. FIG. 2 is a conceptual diagram illustrating a connection between a fiber connector and an optical waveguide.

In FIG. 1, when the optical fiber connector according to the present invention is completed, the optical fiber 2 is fixed while penetrating the holder 13. In this case, the end surface of the optical fiber 2 (the arrow c surface in the figure) is a mirror-shaped cut surface, while the end surface of the optical waveguide 11 has a polished surface exposed so that the two are aligned and joined to each other. Connection with low loss can be made.

 Hereinafter, specific examples of the present invention will be described.

In FIG. 2A, the polished surface (arrow a surface shown) of the conventional optical fiber connector shown in FIG. 4 is immersed in an etching solution for etching only Si crystals such as pyrocatechol under preset conditions. Then, only the Si crystal plane is removed by etching to a thickness of 10 to several hundreds μm.

Therefore, by adding this step, an optical fiber connector in which only the optical fiber 2 according to the present invention protrudes can be formed.

The thickness to be removed by etching is determined by the coefficient of thermal expansion of the UV-curable epoxy adhesive 12 used for connecting and integrating the optical fiber 2 with the optical waveguide 11 and the smaller coefficient of thermal expansion of the optical fiber 2. In order to prevent the peeling phenomenon at the connection fixing part during high temperature use caused by the difference, 10 to several hundreds
It is specified in the range of μm.

Further, the above-mentioned etchant for etching only the Si crystal plane such as pyrocatechol does not remove the SiO ₂ film or the epoxy-based adhesive 5 for stabilizing the surfaces of the silicon substrates 1a and 1b, but the SiO ₂ film has a large thickness. Is very thin, so that it drops off when the Si crystal surface is removed by etching, and the amount of the epoxy-based adhesive 5 is small and the adhesive used for connection and fixation with the optical waveguide is the same type of epoxy resin. There is no particular hindrance due to the residue.

FIG. 2 (B) is a perspective view in the case where there are four optical fibers, and a plurality of optical fibers 2 serving as connection surfaces with an optical waveguide.
The tip end surface (arrow d surface in the figure) maintains a polished surface located on the same plane because the surface is maintained as polished before the Si crystal surface is removed by etching.

FIG. 3 shows an optical fiber connector according to the present invention;
This figure shows a state in which the optical fiber 2 is tightly bonded to the guide 10 provided with the optical fiber 2, and the two are fixed and integrated using a UV-curable epoxy-based adhesive 12 in a space created by projecting the optical fiber 2.

In the figure, the joining portion is limited to the optical waveguide 11 for transmitting an optical signal and the optical fiber 2, and since there is a space as much as the optical fiber protrudes, the two are fixed with a UV-curable epoxy adhesive 12. Before that, the connection surface can be visually observed with a microscope or the like from the side direction of the optical fiber.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide an optical fiber connector that can easily and reliably connect to an optical waveguide without deteriorating transmission characteristics in connection of a transmission line in an optical communication device.

In the description of the present invention, a silicon substrate capable of forming an array with high accuracy and capable of selective etching with an optical fiber is based on the silicon substrate. As long as the material can perform the above, the same hardening can be obtained by cutting and selective etching after arraying not only silicon but also other materials.

[Brief description of the drawings]

FIG. 1 is an external view of an optical fiber connector according to the present invention, FIG. 2 is a sectional structural view and a perspective view of an example of an optical fiber connector according to the present invention, and FIG. 3 is an optical fiber connector according to the present invention. FIG. 4 is a cross-sectional structural view of a conventional optical fiber connector, FIG. 5 is a process diagram of forming a conventional optical fiber connector, and FIG. 6 is a conventional optical fiber connector. FIG. 3 is a conceptual diagram of a connection between a fiber connector and an optical waveguide. In the figure, 1a is a silicon substrate, 1b is a silicon substrate, 2 is an optical fiber, 3 is a core, 4 is a clad, 5 is an epoxy adhesive, 10 is a guide, 11 is an optical waveguide, and 12 is a UV curable epoxy adhesive , Respectively.

Claims (2)

(57) [Claims] 1. A plurality of optical fibers are fixed to a holder, and the holder is cut together with the plurality of optical fibers. An end portion of the holder so that end faces of the cut plurality of optical fibers protrude from the holder. Forming a bonding surface by selectively etching away, aligning the plurality of optical fibers and the plurality of optical waveguides formed on the optical waveguide substrate corresponding to the plurality of optical fibers, A method for connecting an optical fiber and an optical waveguide, wherein an end surface of the optical waveguide substrate where the aligned end surface of the optical waveguide is exposed and a bonding surface of the holder are bonded and fixed. 2. An optical fiber comprising: a plurality of optical fibers; a holder for holding the plurality of optical fibers; and an optical waveguide substrate on which a plurality of optical waveguides corresponding to the plurality of optical fibers are formed. The end faces of the plurality of optical fibers are arranged on the same plane and are held so as to protrude from the end face of the holder, and the end face of the holder and the end face of the optical waveguide substrate are joined and fixed. A connection structure between an optical fiber and an optical waveguide.