JPH063555A - Optical branching device - Google Patents

Abstract

PURPOSE:To provide the structure of the optical branching device which has a function to evenly distribute light input signals for two or more channels as light output signals of plural channels, has good accuracy of branching ratios and can be miniaturized. CONSTITUTION:A waveguide substrate 1 which is formed with at least two pieces each of optical branching circuits 2 each having one piece of light input terminal 2a and >=2 pieces of light output terminals 2b adjacently to each other and an optical fiber coupler array 10 which is constituted by fixing the part from the fusion stretched part 3b of a fusion stretching type optical fiber coupler 3 having at least two pieces each of light input terminals 3a and light output terminals 3c, respectively, to the light output terminals 3c to a plate material 11 with precision positioning grooves are connected and fixed to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical branching device having a function of evenly distributing optical input signals of two channels or more as optical output signals of a plurality of channels.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional 2-input multi-output branch device has at least one optical directional coupling element 2c and a plurality of Y branch optical elements 2d on one substrate. By monolithically integrating the optical waveguide substrate 1 on which an optical branch circuit having a function of distributing an optical signal of two channels to a plurality of channels by itself is formed, and the arrangement interval of the optical fibers 4 is set in advance, The optical fiber array 20 manufactured according to the distance between the input terminal 2a and the output terminal 2b is connected and fixed to each other. In the figure, 21 is a plate with precision positioning grooves for arraying and fixing the optical fibers 4 group, and 22 is a holding plate.

[0003]

When the refractive index distribution structure of the optical waveguide deviates slightly from the design value due to factors such as variations in the manufacturing process, the Y-branching optical element 2d, in principle, changes in the branching ratio. However, in the case of the optical directional coupling element 2c, the branching ratio greatly changes due to the change of the optical coupling state.

Since it is difficult to directly optically monitor the optical output from the optical directional coupling element 2c during the manufacturing process of the optical waveguide, the conventional optical directional coupling element having the optical waveguide is used. In the two-input and multiple-output optical branching device, there is a problem that it is difficult to control the branching ratio for ensuring the uniformity of output light.

[0005]

In the optical branching device of the present invention for solving the above conventional problems, at least two optical branching circuits each having one optical input terminal and two or more optical output terminals are provided. Precise positioning groove is provided at the portion from the fusion extending portion to the light output terminal of the fusion extending optical fiber coupler having the optical waveguide substrate formed adjacent to each other and at least two optical input terminals and two optical output terminals. The optical fiber coupler array, which is fixed to the plate material, is positionally adjusted and then fixed.

The optical branch circuit formed on the optical waveguide substrate according to the present invention preferably has a circuit configuration in which a plurality of Y-shaped branch portions are connected to each other by a straight waveguide or a curved waveguide. It may have an X-shaped branch portion.

Further, the distances between the optical branch circuits arranged adjacent to each other must be such that the optical output terminals do not overlap each other, and all the optical output terminals are arranged in a line at equal intervals. The configuration is preferred.

The distance between the precision positioning grooves of the optical fiber coupler array must be equal to the distance between the optical input terminals of the optical branch circuit arranged adjacent to the optical waveguide substrate. Further, regarding the depth of the positioning groove, when the optical output terminal of the optical fiber coupler is embedded in the groove, a depth such that a part of the optical output terminal is exposed on the surface of the plate material in which the groove is formed is preferable. , It is possible to improve the alignment accuracy of the optical output terminals of the optical fiber coupler by adhering and fixing the exposed optical output terminals while pressing them in the depth direction of the groove with another plate material, but it is not limited to this method. Not a thing.

Further, it is effective that the portion of the optical fiber coupler which is fixedly adhered to the plate member having the precision positioning groove is all the portions from the fusion extending portion to the optical output terminal. It may be alone.

Further, by cutting or polishing the end portion of the plate member to which the optical fiber coupler is bonded and fixed, an array having an end face where the cross section of the optical output terminal of the optical fiber coupler is exposed is produced. If the end faces of the optical waveguide substrate are fixed to each other, the connection is easy.

By means of the above means, the optical fiber array array is prepared in advance on the optical output terminal side of the optical branching device in which the optical fiber coupler array is fixed to the optical input terminal side of the optical branching circuit. The optical fiber array can be fixed. Further, it is also possible to fix the microlens array, which is also manufactured by matching the array intervals.

[0012]

In the optical branching device configured as described above, the optical input signals of the two channels are uniformly mixed by the fusion-stretching optical fiber coupler, and then divided into the two channels and output again. When the optical output signal is input to the subsequent optical branch circuit, it functions to evenly distribute the optical output to the plurality of optical output terminals.

Since the optical output terminals of the fusion-stretched optical fiber coupler are fixed to a plate member having precision positioning grooves to form an array, alignment with the optical input terminals of the optical branch circuit is easy. And the cross-sectional area of the array is
Since it is significantly larger than the cross-sectional area of the optical output terminal of the optical fiber coupler, it is possible to increase the strength of fixation with the optical waveguide substrate.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a plan view showing an embodiment of the optical branching device of the present invention, and FIG. 2 is a side view of the same. In the illustrated example, the number of light input terminals is two and the number of light output terminals is eight. In manufacturing the above device, as a first step, two optical branch circuits 2 are formed on the optical waveguide substrate 1. As an example, a single-mode optical branch circuit having a wavelength of 1.3 to 1.55 μm was produced in a glass substrate by using a two-step ion exchange method.

The pattern of the optical branch circuit is formed on a photomask used in the photolithography process described below, but two optical branch circuits 2 each having one optical input terminal 2a and four optical output terminals 2b are provided. The light input terminals 2a are arranged adjacent to each other, and the distance between the light input terminals 2a is 1 mm, and the distance between the eight light output terminals 2b is 250 μm.

First, an optical grade glass containing sodium ions and potassium ions is used as the optical waveguide substrate 1, and a titanium film having a thickness of 0.5 μm is formed on one surface of this glass substrate by a vacuum deposition method, and photolithography and After the titanium film is provided with an opening corresponding to the pattern of the optical branching circuit 2 by each step of the selective etching, the titanium film-coated glass is placed in a high-temperature molten salt containing thallium ions as a first-stage ion exchange step. By immersing the substrate, a high refractive index region having the pattern of the optical branch circuit 2 was formed within the thickness of the substrate.

After cooling, the glass substrate from which the titanium film has been removed by etching is brought into contact with a high temperature molten salt containing potassium ions and sodium ions in the second step of ion exchange, and 100 V / in the thickness direction of the substrate.
By applying an electric field of mm, the high refractive index region to become the optical branch circuit 2 was embedded at a depth of about 15 μm from the substrate surface.

Then, the substrate was cut and its cross section was polished so that the optical input terminal 2a and the optical output terminal 2b of the optical branch circuit 2 were exposed at the end face of the optical waveguide substrate 1. The size of the obtained optical waveguide substrate 1 is 4 mm in width, 30 mm in length, and 2 in thickness.
It was mm.

Although a detailed explanation of the two-stage ion exchange method itself is omitted, for example, in the proceedings of the 1991 IEICE Fall Conference Proceedings C-187, the present inventors have proposed an optical branch circuit using the two-stage ion exchange method. The manufacturing method of is disclosed,
This method can be used for manufacturing the optical branch circuit 2.

Next, as a second step, the optical fiber coupler array 10 and the optical fiber array 20 are manufactured. First of all, for the optical fiber coupler array, using a dicing saw equipped with a circular foil with a blade angle of 45 degrees, a width of 4 m
Two V-shaped grooves 14 were formed in a glass plate 11 having a length of m, a length of 40 mm and a thickness of 2 mm. The depth of the groove top is 140 μm, 2
The interval between the grooves of the book was 1 mm.

Next, the optical output terminal 3c of the fusion-stretched optical fiber coupler 3 having a branching ratio of 50:50 at wavelengths of 1.3 μm and 1.55 μm is set to a length of about 100 mm from the fusion-bonded portion 3b. The coating is removed over, and the portion as close as possible to the fusion stretched portion is placed on the V groove 14, and W4 ×
While pressing the L5 × T1 mm glass plate 12, the epoxy adhesive 13 was instantly filled and fixed.

The fusion-bonded stretched portion 3b was also fixed to the glass plate 11 with an epoxy adhesive. After the adhesive was completely cured, the light output terminal 3c protruding from the glass plate was folded and removed, and the end face was polished to a mirror finish.

The manufacturing method of the optical fiber array 20 is almost the same as that of the optical fiber coupler array 10, except that eight V grooves are formed at intervals of 250 μm, and one groove is formed in each groove. The single-mode optical fiber 4 is fixed.

In the third step, the optical fiber coupler array 1
0, the optical waveguide substrate 1, and the optical fiber array 20 are position-adjusted so that the optical loss at the connection points of the respective optical paths is minimized, and the connection surface is filled with an ultraviolet curable adhesive so that the ultraviolet light is emitted. They were fixed to each other by irradiating. Furthermore, the entire unit except the optical input / output terminal is W7 × L100 × T6m
m SUS container and filled with silicone resin to form a package.

The optical loss characteristics of the optical branching device manufactured in the above-described embodiment are shown by the wavelengths of 1.3 μm and 1.55 μm.
The measurement was performed using a laser light source of m. As a result, the excess loss was 0.7 dB, and the fluctuation range of the branching ratio was 0.2 dB or less at all wavelengths.

Although the present invention has been described based on the embodiments, it goes without saying that various modifications can be made other than the embodiments. For example, the material of the optical waveguide substrate 1 is quartz,
It is possible to use silicon, lithium niobate, a polymer resin, or the like. In these cases, the optical branch circuit 2 can be formed by a manufacturing method other than the ion exchange method.

Further, as the plate member with the precision positioning groove for fixing the optical fiber coupler, a machined product of metal such as SUS or an anisotropically etched silicon substrate can be used.

[0028]

According to the present invention, since the fusion-stretched optical fiber coupler capable of directly optically monitoring the branching ratio in the manufacturing process is used, an optical branching device with high branching ratio accuracy can be manufactured with a high yield.

Since most of the optical waveguide circuit is formed, the device can be downsized. The optical branching device manufactured in the example is about 1 in comparison with a device in which fusion-stretched optical fiber couplers are mutually connected to have the same function.
It was one-fifth the size.

Further, by fixing the distance between the optical output terminals of the optical fiber coupler to the plate material in accordance with the distance between the optical input terminals of the optical branch circuit, the optical axis adjustment between them can be facilitated. Further, by fixing the optical fiber coupler to the plate member, a large bonding area with the optical waveguide substrate can be obtained, so that there is an advantage that the strength of the device against disturbance is increased and the device is not easily broken.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

2 is a side view of the embodiment of FIG.

3 is a sectional view of the optical fiber coupler array taken along the line AA ′ in FIG.

FIG. 4 is a plan view of a conventional optical branching device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical waveguide substrate 2 Optical branch circuit 2a Optical input terminal of optical branch circuit 2b Optical output terminal of optical branch circuit 2c Directional coupling element 2d Y-branch optical element 3 Fusion splicing type optical fiber coupler 3a Optical input terminal of optical fiber coupler 3b Fusion extension part of optical fiber coupler 3c Optical output terminal of optical fiber coupler 4 Optical fiber 10 Optical fiber coupler array 11 Plate with precision positioning groove 12 Holding plate 13 Adhesive 14 V-shaped groove 20 Optical fiber array 21 With precision positioning groove Plate 22 Presser plate

Claims (1)

[Claims] 1. A waveguide substrate formed by adjoining two or more optical branch circuits each having one optical input terminal and two or more optical output terminals, and at least two optical input terminals and two optical input terminals. The optical fiber coupler array is formed by fixing a portion extending from the fusion extending portion of the fusion extending type optical fiber coupler having output terminals to the optical output terminal to a plate material with a precision positioning groove, and connecting and fixing it to each other. Characteristic optical branching device.