JPS5848006A - Optical branching circuit and its production - Google Patents

Abstract

PURPOSE:To decrease light losses by formation of a main waveguide and a subwaveguide having a circular shape in section by irradiating the UV light propagated through an optical fiber of graded index type to a photosensitive resin coated on a glass substrate thereby curing the resin. CONSTITUTION:A glass substrate 6 is disposed between an optical fiber 1 and optical fibers 2, 3, and a photosensitive resin is coated thereon. UV light of the wavelength region sensitive to the resin is throttled with a lens and is made incident to the fiber 1. The UV light propagates in the fiber 1, cures the uncured photosensitive resin successively from the end face of the fiber 1 until it arrives at the end face of the fiber 2. The UV light is made incident from the fiber 2 as well to cure the photosensitive resin. The uncured parts are removed by developing, whereby a main waveguide 4 is obtained. In the same manner, the photosensitive resin is coated and the UV light is made incident to the fiber 3. The resin is processed in the same manner, whereby a subwaveguide 5 is obtained. Thus the main waveguide 4 and subwaveguide 5 having a circular shape in section of the diameter approximately equal to that of the fibers are formed. Thus light losses are decreased considerably as compared to conventional branching circuits of a square or trapezoidal shape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical branch circuit used in an optical communication system.

In an optical fiber communication line of an optical communication system, for example, when branching or adding an optical signal for CATV, a light source,
Optical branch circuits are used to monitor and inspect the states of transmission lines and light receiving elements.

Conventional optical branching circuits include those that utilize coupling between thin film light guides and those that form half mirrors on thin film light guides, but these all require strict precision machining and are difficult to realize. It has the disadvantage of being

In addition to this, there are waveguides formed by irradiating ultraviolet rays through a mask on a photosensitive resin coated on a glass substrate, but in this case, the cross-sectional shape of the waveguide is square or trapezoidal. Therefore, there was a drawback that optical loss was large due to the difference in shape with the optical fiber to be connected.

The purpose of the present invention is to solve these drawbacks, and for this purpose, a photosensitive resin coated on a glass substrate is irradiated with ultraviolet light propagated through a graded index optical fiber and cured, thereby creating a material with a circular cross-sectional shape. It is characterized by forming a main waveguide and a sub waveguide.

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, reference numerals 1, 2 and 3 are graded index type optical fibers, and the main waveguide 4 is made of photosensitive resin.
and an end face of a sub-waveguide 5 branched from the middle of the main waveguide 4.

The main waveguide 4 and the sub-waveguide 5 are formed on a heat-resistant glass substrate 6, and their cross-sectional shape is similar to that of the optical fiber 1.
, 2.3 is formed into a circular shape with approximately the same diameter. , , 7 is a silicone resin which becomes the cladding of the main waveguide 4 and the sub waveguide 5, and is molded on the glass substrate 6.

Next, an example of manufacturing the above-mentioned optical branch circuit will be described. First, optical fibers 1, 2, and 3i with a core diameter of 60 μmφ and a cladding diameter of 150 μmφ are made of silicon single crystal (IIGIo
l) V-groove substrate prepared by etching the surface (not shown)
Align the position so that it has a predetermined relationship, and
Wavelength 6328 using a He Ne laser with an output of 1W as a light source
Align the optical axes of the cores of optical fibers 1, 2, and 3 with the He-Ne laser beam of A, and then
2.3 is fixed to the V-groove substrate. The lengths of the optical fibers 1, 2, and 3 are set as necessary to construct the optical branch circuit, and the lengths are set as 3 to 5 here.

Next, an acrylic photosensitive resin is applied onto a glass substrate 6 having a refractive index of 1,472 and having dimensions of 110×10×5− and a mirror finish on the entire surface. This photosensitive resin needs to be applied thicker than the diameter of the cores of the optical fibers 1 and 2, and here it is set to 7 μm.

Next, this glass substrate 4 is connected to the optical fiber 1 and the optical fiber 2,
Place it between 3 and 3. Then, when ultraviolet rays with a peak wavelength of 370 nm, which is the photosensitive wavelength range of the photosensitive resin, are focused by a lens and incident on the optical fiber 1, the ultraviolet rays propagate through the optical fiber 1 and are emitted to the uncured photosensitive resin. However, the photosensitive resin is cured sequentially from the end surface of the optical fiber 1 to approximately the same diameter, and reaches the end surface of the optical fiber 2. In addition, in order to reduce the variation in the outer diameter of the main waveguide 4 to be formed, to make the refractive index uniform, and to improve the close contact with the end face of the optical fiber 2, ultraviolet rays are also emitted from the optical fiber 2. The light enters and hardens the photosensitive resin, and after curing,
The main waveguide 4 is obtained by removing the uncured portion of the photosensitive resin by development.

Next, the same photosensitive resin as above is applied to the portion where the sub waveguide 5 is to be formed, and ultraviolet rays are made to enter the optical fiber 3. Thereby, the photosensitive resin is cured until it intersects with the main waveguide 4, and after curing, the uncured portion is removed by development to obtain the sub waveguide 5.

Finally, the entire structure is molded with silicone resin 7 having a refractive index of 1,410 to clad and protect the main waveguide 4 and sub-waveguide 5.

In addition, in the above-mentioned manufacturing method, when curing the photosensitive resin, scattering curing due to the spread of ultraviolet rays emitted from the optical fiber 1.2.3 is considered, but the optical fiber 1.2.3 used in the present invention is gray. This graded index type optical fiber has excellent straightness of light, and the light intensity at the central axis is very large, so the main waveguide 4 and the sub waveguide 5 are connected to the optical fiber 1. It can be hardened to a diameter approximately equal to the core diameter of 2.3 mm.

The optical branching circuit of the present invention obtained in this way, as shown in FIG.
The optical fiber 2 is propagated through the main waveguide 4 and the sub waveguide 5.
, 3, and the optical fiber 2
Or the optical signal transmitted to main waveguide 4'! or sub-waveguide 5f/i: can be propagated and taken out from the optical fiber 1.

Note that the degree of coupling from the main waveguide 4 to the sub waveguide 5 can be arbitrarily set depending on the angle formed between the two.

FIG. 3 is an enlarged view showing the cross-sectional shapes of the main waveguide and sub waveguide of the optical branch circuit according to the present invention and the conventional optical branch circuit.
Figures (,) are of the present invention, and Figure 3(b) is of the conventional type.

The main waveguide and sub-waveguide according to the present invention are formed by curing the photosensitive resin with ultraviolet light propagated through the optical fiber as described above, so if the cross-sectional shape is circular with approximately the same diameter as the core of the optical fiber. Therefore, while the optical loss due to the difference in shape between the conventional rectangular or trapezoidal main waveguide and sub waveguide and the optical fiber was 0.8 dB, the optical loss according to the present invention was 0.8 dB. 2 dB.

There is no need for one connection between the trenched optical fiber and the main waveguide and the sub waveguide, and connection loss can also be reduced.

As explained above, in the present invention, the main waveguide and the sub waveguide are formed by irradiating the photosensitive resin coated on the glass substrate with ultraviolet rays propagated through an optical fiber. It can be made circular, which has the effect of reducing optical loss.

It is easy to manufacture, inexpensive because it does not require a mask like conventional methods, and it is also very reliable because it is very easy to connect the main waveguide and sub-waveguide to the optical fiber. It can be used as a T-branch or star branch circuit for highly flexible communication systems.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the present invention, FIG. 2 is a side sectional view thereof, FIG. Figure (b) is an enlarged view showing the cross-sectional shapes of a conventional main waveguide and a sub-waveguide. 1.2.3... Optical fiber 4... Main waveguide 5.
...Sub-waveguide 6...Glass substrate 7...Silicone resin patent applicant Oki Electric Industry Co., Ltd. Representative patent attorney Takashi Kanakura Niwa 11:ill noodles 2; Procedural amendment (master) January 1982 1811 Commissioner of the Patent Office Shima 1) Haruki Tono1, Indication of the case 1981 Patent Application No. 1462012,
Title of the invention Optical branching circuit and its manufacturing method 3, relationship to the amended case Patent applicant address 1-7-12 Toranomon, Minato-ku, Tokyo Name (029) Oki Electric Industry Co., Ltd. Representative Masao Miyake 4. Agent 6. Subject of amendment Specification "Claims column" 0 "Detailed description of the invention column" 0 7 Contents of amendment 1. The claims are amended as follows. 1. A main waveguide with a circular cross-section and a diameter approximately equal to the core diameter of the optical fiber and a sub-waveguide branched from the main waveguide are formed on a glass substrate using photosensitive resin, and silicone resin is molded on top of the main waveguide. An optical branch circuit characterized by having a cladding.A photosensitive resin is coated on two glass substrates, and the necessary portions are exposed by irradiating the photosensitive resin with ultraviolet light propagated through a Greyget index type optical fiber. A method for manufacturing an optical branching circuit, which comprises curing and removing uncured portions by development to form a main waveguide and a sub-waveguide.'' 2 Specification, page 2, line 18, page 3, line 3 ~4th line, page 5, 16th line, 17th line, and 18th line "Graded Index" is corrected to [Graded Index C]. 3. "5N" on page 4, line 4 of the specification is corrected to "5m". 2-

Claims (1)

[Claims] 1. A main waveguide with a circular cross-section and a diameter substantially equal to the core diameter of an optical fiber and a sub-waveguide branched from the main waveguide are formed on a glass substrate using a photosensitive resin, and a silicone An optical branch circuit characterized by having a cladding formed by molding resin. 2. Coating a photosensitive resin on a glass substrate, irradiating the photosensitive resin with ultraviolet light propagated through a graded index optical fiber to cure the necessary parts, and removing the uncured parts by development. A method for manufacturing an optical branch circuit, comprising forming a main waveguide and a sub waveguide.