JPH0415603A - Production of optical demultiplexing/multiplexing circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Concerning a method for manufacturing an optical branching/multiplexing circuit, - To construct an optical branching/multiplexing circuit that can be easily aligned on a single substrate and has low insertion loss. A process of forming a plurality of fiber fixing grooves and a plurality of guide pin grooves that intersect with each other on a substrate, a process of fitting and fixing optical fibers into the plurality of fiber fixing grooves, and a process of forming a plurality of optical fibers through the intersection points of the optical fibers. and a step of cutting the substrate along a straight line intersecting with the plurality of guide pin grooves, a step of forming an optical functional film on at least one of the cut surfaces of the substrate, and a step of a step of fitting and fixing the guide pin, which is shorter than the length of the id pin groove, into one of the guide pin grooves so as to partially protrude from the cut surface;
fitting a kite pin partially protruding from one cut surface of the cut substrate into the guide pin groove of the other, and tightly fixing both cut surfaces of the cut substrate with an optical adhesive layer in between; A method for manufacturing an optical branching/multiplexing circuit is configured to include at least the following.

[Industrial application field]

The present invention relates to an optical branching/multiplexing circuit, and more particularly, to an improvement in a method for manufacturing a small, high-performance optical branching/multiplexing circuit used in large-capacity optical fiber communications such as wavelength division multiplexing communication and bidirectional communication.

[Conventional technology]

Figure 3 is a diagram showing an example of a conventional optical branching/multiplexing circuit (Part 1).
).

In the figure, an optical prism 100 is made of transparent glass and has an optical surface processed to form a required apex angle.

Optical functional films 50 to 5 are provided on optical surfaces, for example, opposing planes.
3 is formed. Optical fibers 40a, 40b, 40c, 40 are located close to the optical functional films 50 to 53, respectively.
The optical axis is adjusted and arranged so that d becomes a required angle of incidence, angle of refraction, angle of reflection, or angle of emission.

Now, for example, the wavelength λ1゜λ2 from the optical fiber 40a
．． Light with a mixture of three wavelengths λ3 is incident on the optical functional film 52°, for example, an anti-reflection film, and is refracted into the optical prism 100 to form the light on the other surface of the optical functional film 50, for example, light with a wavelength λ1. is transmitted and λ2. When the light of wavelength λ3 is made incident on the reflective wavelength selection filter film, only the light of wavelength λ1 is emitted from the optical prism 100 and is branched and transmitted to the optical fiber 40b. On the other hand, the wavelength λ2. The light of λ is reflected and returns to the first surface again to form the optical functional film 51. For example, if the light with the wavelength λ2 is made incident on a wavelength selection filter film that transmits the light and reflects the light with the wavelength λ3, only the light with the wavelength λ2 will be emitted from the optical prism 100 and branched and transmitted to the optical fiber 40c. On the other hand, the wavelength λ
, is reflected and passes through the optical prism 100 to the optical functional film 53 formed on the second surface. For example, the light passes through an antireflection film, exits the optical prism 100, is guided to the optical fiber 40d, and is branched and transmitted. That is, the wavelength λ1. λ2. λ
The mixed light of three wavelengths 3 is branched into separate optical fibers 40b, 40c, and 40d, respectively. In addition,
In the case of multiplexing, if separate lights are incident in directions opposite to the above, combined light can be obtained from the optical fiber 40a due to the retrograde nature of the light.

Note that the figure shows the basic configuration and the package and the like are omitted.

The above method has the advantage of being able to be configured by combining conventional individual optical components, but on the other hand, it is difficult to adjust the optical axis.
For example, it is very difficult to adjust the angle of incidence, angle of refraction, angle of reflection, or angle of emission, and it requires skill and a long time.

In contrast, recently, a structure has been proposed in which a plurality of optical fibers are placed close to each other on a single substrate and coupled to an optical functional component.

Figure 4 is a diagram showing an example of a conventional optical branching/multiplexing circuit (Part 2).
). In the figure, l is a substrate with grooves formed on its surface,
After a plurality of, for example two, optical fibers 4a and 4b are fitted and fixed at a predetermined angle, for example θ, the optical fibers 4a and 4b pass through the intersection of the two optical fibers 4a and 4b at a predetermined angle, for example. , φ to form a component insertion groove 8. By inserting and fixing the optical functional component 9 into the component insertion groove 8 and packaging it, a solid-state optical branching/combining circuit integrated on a single board can be obtained, and the optical axis adjustment is extremely easy. It becomes easier.

[Problem to be solved by the invention]

The conventional example (part 2) shown in FIG. For example, since the optical functional film 5'' is formed on one or both sides of a glass substrate, its thickness needs to be at least 0.3 to 0.5 mm, and therefore it is exposed on both end surfaces of the component insertion groove 8. The spacing between optical fibers has become larger, and in particular, in the case of recent single-mode optical fibers, the core diameter is extremely thin, about 10 μm, and coupling loss between both fibers has become a serious problem, which needs to be solved. It had become.

[Means to solve the problem]

The above-mentioned problems include a step of forming a plurality of fiber fixing grooves 2 and a plurality of kite pin grooves 3 that intersect with each other on a substrate 1, a step of fitting and fixing the optical fibers 4 into the plurality of fiber fixing grooves 2, and a step of forming the optical fibers 4 in the plural fiber fixing grooves 2. The substrate l passes through the intersection of the optical fibers 4 and intersects with the plurality of guide pin grooves 3.
a step of forming an optical functional film 5 on at least one of the cut surfaces of the substrate 1; and a step of forming an optical functional film 5 on at least one of the cut surfaces of the substrate 1; A step of fitting and fixing a guide pin 6 shorter than the length of 3 so that it partially protrudes from the cut surface, and fixing the guide pin 6 that partially protrudes from one cut surface of the cut substrate l to the other guide pin. A manufacturing method of an optical branching/multiplexing circuit configured to include a process of fitting into the optical groove 3 and closely fixing both cut surfaces of the cut substrate l with an optical adhesive layer 7 in between. This can be solved by

[Effect]

According to the method of the present invention, since the optical functional film 5 is directly formed on the cut surface of the substrate 1, the cap between the end faces of the optical fiber exposed on the cut surface can be made extremely small. Moreover, when joining the cut side boards, the guide pin groove 3
Since the position is determined by fitting the kite pin 6 with the kite pin 6, there is no need to adjust the optical axis, and assembly can be performed extremely easily.

〔Example〕

14th. Figure 1 is a diagram showing the main steps of an embodiment of the present invention, and the main steps will be explained in order below.

Step (1) For example, the thickness of the two substrates is 0.7 mm.
A silicon substrate with one plane orientation C100) is used. As is well known, a silicon substrate is anisotropically etched in a unique shape depending on its surface orientation, and holes or grooves with sharp shapes such as rectangles and V-shapes are formed.

For example, in a silicon substrate with this orientation, the etching rate is very fast in the <100> direction and slow in the <lit> direction. ] plane), a V-shaped fiber fixing groove 2b and guide pin grooves 3a, 3b, and a rectangular rectangular side face (both [111] planes) facing each other in a direction perpendicular to these grooves. Fiber fixing groove 2a
can be formed.

A photo-etching technique is used as a specific process for forming these grooves. For example, first, a 500 nm thick SiO□ film is formed on the surface of a substrate 1 made of a silicon plate with a plane orientation (100) by a known thermal oxidation method, and then a photoresist is applied thereon. After exposing and developing the thermal oxide silicon film using a mask to obtain the pattern arrangement shown in (1), the thermally oxidized silicon film was etched for 4 minutes at room temperature in a solution containing a mixture of 5 ammonium fluoride and 1 part hydrofluoric acid. Remove. Next, using the remaining thermally oxidized 5i02 film as a mask, 110°C EPW solution (ethylenediamine) was applied.

Etch for 4 hours in a catechol/water mixture. Comparing the respective etching rates at this time, it is found that 5i per hour (L film: IOA, (111)Si: 0.8
μm, (100)Si: 30 μm, and it can be seen that extremely sharp anisotropic etching is performed.

By anisotropic etching using the above 5in2 film as a mask, a V-shaped fiber fixing groove 2b with a depth of 120 μm and a width of 130 μm, guide pin grooves 3a and 3b, and a direction perpendicular to these grooves (θ= A V-shaped fiber fixing groove 2a having two slopes (both [111] planes) facing each other at an angle of 90° can be formed. Note that the width and depth of each groove may be arbitrarily adjusted depending on the dimensions of the thermally oxidized 5102 film mask and the etching time.

Step (2): Fiber fixing grooves 2a, 2 on the treated substrate
For example, single-mode optical fibers 4a and 4b having an outer diameter of 125 μm are fitted to b, and fixed with an adhesive if necessary.

Step (3): The optical fibers 4a, 4 of the treated substrate
b, and the plurality of guide pin grooves 3a
, 3b (for example, forming an angle φ with the optical fiber 4a), the substrate 1 is cut using, for example, a diamond blade capable of mirror cutting.

Step (4): An optical functional film 5 is formed on at least one of the cut surfaces of the treated substrate. For example, SiO2, TiO□, M
A dielectric multilayer film such as gO is formed with wavelength selectivity. Methods for imparting such wavelength selectivity, for example, the property of transmitting or reflecting light of a specific wavelength, are already known, and the angles θ and φ, the refractive index of each dielectric film, the number of thickness layers, etc. are selected. can be designed. Furthermore, the -dielectric multilayer film may be formed using a known vapor deposition method or sputtering method.

Step (5): Either one of the treated substrates, for example,
In FIG. 5, the length of the guide pin grooves 3a and 3b is shorter than the length of the guide pin grooves 3a and 3b on the substrate on which the optical functional film 5 is formed.

For example, guide pins 6a and 6b made of glass rods with an outer diameter of 125 μm are partially protruded from the cut surface, fitted, and fixed with adhesive. Make sure the length of the guide pin is shorter than the length of the guide pin groove, so it will not get in the way and the cut surface will be fixed in its original position.

Step (6): The guide pins 6a, 6b partially protruding from one cut surface of the processed substrate I are fitted into the guide pin grooves 3a, 3b remaining in the other substrate I, and the cut substrate I is cut.
Both cut surfaces are brought into close contact with each other with an optical adhesive layer 7 interposed therebetween, and are adhesively fixed using, for example, an epoxy optical adhesive. At this time, the gap between the guide pin and the guide pin groove is also fixed with adhesive.

After completing the above processing, packaging is performed to complete the optical branching/multiplexing circuit according to the method of the present invention.

FIG. 2 is a perspective view showing the external appearance of an example device according to the method of the present invention, and is illustrated to facilitate understanding of the overall device configuration. For example, wavelength λ1. When mixed light of wavelength λ2 is made incident on the optical fiber 4a, it is demultiplexed by the optical functional film 5, and the light of wavelength λ2 is transmitted to one side of the optical fiber 4b, for example, the right side, and the light of wavelength λ2 is transmitted to the other side, that is, the left optical fiber 4b. It can be configured such that the light of the following types is emitted.

The device according to the method of the present invention is extremely compact and robust as a whole, and the gap at the cut surface of the optical fiber 4 is about the same as the total thickness of the optical functional film 5 and the optical adhesive layer 7, so it is several 10 μm at most. Compared to the conventional example (Part 2), the insertion loss is 1/2 or less. Therefore, the insertion loss is 1/2.
Reduced to:

In the above embodiments, a silicon substrate was used as the substrate l, but the substrate is not limited to this, and other substrates such as glass, ceramic two metals, etc. may be used, and the grooves can also be formed by anisotropic etching. Ordinary photoetching techniques may be used.

In addition, although the above embodiment shows the case where the optical fiber 4 has one intersection, if the optical fiber 4 is provided at multiple locations and cut in the same manner, and an optical functional film is formed on the cut surface to fabricate a device, it is possible to produce a device with three or more wavelengths. It is possible to form an optical branching/multiplexing circuit that branches light that is a mixture of lights of three wavelengths or multiplexes light of three or more wavelengths.

Further, the number of guide pin grooves 3 is not limited to two, but may be three or more, and the directions thereof may be parallel (they may be formed at an appropriate angle).

The above-mentioned embodiments are merely examples, and the materials used, their combinations, and the configurations of each process may be appropriately selected and used as long as they comply with the spirit of the present invention. Needless to say.

〔Effect of the invention〕

As explained above, according to the method of the present invention, since the optical functional film 5 is directly formed on the cut surface of the substrate 1, the gap between the end faces of the optical fibers exposed on the cut surface can be made extremely small. Moreover, when joining the cut side substrates, positioning is done by fitting the guide pin groove 3 and the guide pin 6, so there is no need for optical axis adjustment, making assembly extremely simple. It greatly contributes to improving the performance 9 quality of multiplexing circuits, lowering prices, and improving the workability of assembling optical circuits.

[Brief explanation of the drawing]

The 14th rotation axis and the +-1 are diagrams showing the main steps of the embodiment of the present invention. Figure 2 is a perspective view showing the external appearance of an example device according to the method of the present invention. Figure 3 is a conventional optical branching diagram.・Diagram showing an example of a multiplexing circuit (part 1)
), Figure 4 is a diagram showing an example of a conventional optical branching/multiplexing circuit (Part 2).
). In the figure, l is the substrate, 2 (2a, 2b) is the fiber fixing groove, 3 (3a, 3
b) is a guide pin groove, 4 (4a, 4b) is an optical fiber, 5 is an optical functional film, 6 (6a, 6b) is a guide pin, and 7 is an adhesive layer.

Claims (1)

[Claims] A plurality of fiber fixing grooves (2) that intersect with each other on a substrate (1).
and a step of forming a plurality of guide pin grooves (3), a step of fitting and fixing an optical fiber (4) into the plurality of fiber fixing grooves (2), and passing through an intersection of the optical fibers (4), and the substrate (
1); forming an optical functional film (5) on at least one of the cut surfaces of the substrate (1); and forming a guide pin for one of the cut substrates (1). a step of fitting and fixing a guide pin (6) shorter than the length of the guide pin groove (3) into the groove (3) so as to partially protrude from the cut surface; and one of the cut substrates (1). The guide pin (6) partially protruding from the cut surface of the substrate (1) is fitted into the other guide pin groove (3), and both cut surfaces of the cut substrate (1) are held together with the optical adhesive layer (7) in between. A method of manufacturing an optical branching/multiplexing circuit, comprising at least the step of closely fixing the optical branching/multiplexing circuit.