JPH0618734A - Waveguide type optical splitter / coupler - Google Patents

Abstract

(57) [Summary] [Object] To provide a waveguide type optical branching / coupling device that can be manufactured with a high yield. [Structure] In this waveguide type optical branching / coupling device, two waveguides 1 and 2 intersect in an X shape, and a filter chip 4 is arranged at an intersection 3 thereof. [Effect] Since the branch coupling ratio is defined by the transmittance / reflectance ratio of the filter chip, the precision of the dimensional parameter at the time of forming the waveguide can be loosened, and the manufacturing becomes easier accordingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide type optical branching / coupling device, and more particularly to a waveguide type optical branching / coupling device which can be manufactured with a high yield.

[0002]

2. Description of the Related Art Aurora, which is a subscriber optical fiber monitoring system currently under development and research, has two inputs.
A two output optical splitter / coupler is required. Specifically, 1.3
It is a two-input / two-output optical branching / coupling device that shows a constant branching / coupling ratio of 80/20% for optical signals in a wide wavelength range of up to 1.55 μm.

As such an optical branching / coupling device, a fused taper fiber type, in which two optical fibers are welded and processed, is known, but recently, an attempt is made to reduce the size by increasing the number of cores in the future. Then, a Mach-Zehnder interferometer has been proposed (Tech. Dig. 1st Conf. Integrated Photonics Rese
arch, K. Jinguji, Hilton Head, 1990). This Mach-Zehnder interferometer has two directional couplers A ₁ and A ₂ capable of evanescent coupling by bringing _two waveguides l ₁ and l ₂ close to each other, as shown in a schematic plan view in FIG. And forms a phase section A ₃ between these directional couplers A ₁ , A _2.
It has a structure with.

[0004]

In order to obtain a good wavelength flatness at the branch coupling ratio by using the interferometer shown in FIG. 4, the cross-sectional dimensions of the cores of the waveguides l ₁ and l ₂ , mutual spacing, coupling Strict precision is required for the length, and the tolerance of the relative refractive index difference Δ must be strictly controlled. For example, 80
When trying to obtain a branch coupling ratio with a tolerance of ± 1% with respect to / 20%, the cross-sectional dimensions of the cores of the waveguides l ₁ and l ₂ are ± 0.1.
The interferometer must be manufactured so that the accuracy is within μm and the relative refractive index difference Δ is within ± 0.01%.

The waveguide in the above interferometer is usually made of quartz. That is, for example, on a Si substrate, a layer of quartz fine particles to be a clad and a core is laminated by a flame deposition method, the whole is heated to vitrify, and then dry etching is performed on the whole to form a waveguide of a predetermined size. Form. Therefore, a dimensional error will inevitably occur during these operation steps, but it is very difficult to keep the error within the above-mentioned accuracy range, and therefore the yield during manufacturing becomes extremely low.

The present invention solves the above-mentioned problems, and a desired branch coupling ratio can be obtained irrespective of the dimension parameter of the waveguide, and therefore, the fabrication is easy, so that the fabrication can be performed with a high yield. An object is to provide a waveguide type optical branching / coupling device.

[0007]

In order to achieve the above object, the present invention is characterized in that two waveguides intersect each other in an X shape and a filter chip is arranged at the intersection. A waveguide type optical branching / coupling device is provided.

[0008]

In the optical branching / coupling device of the present invention, the filter chip manufactured so that the ratio of the transmittance and the reflectance has a desired value is arranged at the intersection of the two waveguides. Therefore, the branching / coupling ratio at the intersection of the waveguides is defined by the transmittance / reflectance ratio of the filter chip arranged therein.

When the filter chip is a half mirror composed of a dielectric multi-layer film, the transmittance / reflectance ratio is determined by appropriately adjusting factors such as the thickness of the layer, the number of layers, and the material of the layer. By selecting, it can be set to a predetermined value. Therefore, in the optical branching / coupling device of the present invention, a desired branching / coupling ratio can be obtained without strictly controlling the dimension parameter of the waveguide.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical branching / coupling device of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic plan view showing an example of the optical branching / coupling device of the present invention. In the figure, two silica-based waveguides 1 and 2 are formed on a Si substrate (not shown) by applying a conventional flame deposition method and a dry etching method. These waveguides 1 and 2 are X at the crossing angle θ.
The intersection 3 is formed by intersecting in a letter shape.

The waveguides 1 and 2 have a core cross-sectional size of 8 μm □ and a relative refractive index difference Δ of 0.3% in order to obtain compatibility with a standard single-mode optical fiber connected thereto. Has become. In this case, if the crossing angle θ is 5 ° or more, crosstalk between the waveguides in the vicinity of the crossing portion 3 can be reduced to a negligible level. Further, when the crossing angle θ is 15 ° or less, it will be described later. The crossing angle θ in FIG. 1 is set to 10 ° because the polarization dependency of the filter chip when the filter chip is arranged can be ignored.

A filter chip 4 is arranged at the intersection 3. Specifically, a slit 5 having a predetermined depth, width, and length is formed at the intersection 3 at a right angle to the optical axis, and a filter chip 4 is inserted into the slit 5 and then embedded with an optical adhesive to form the filter. Fix the tip. As the filter chip, for example, a half mirror having a dielectric multilayer film filter structure in which a thin layer of TiO ₂ and SiO ₂ is laminated on a glass substrate having a thickness of 20 μm, or a wavelength filter is used.

In the case of this optical branching / coupling device, for example, the waveguide 1
The optical signal propagating through the
Thus, the light is transmitted or reflected according to the transmittance / reflectance ratio of this filter chip. Therefore, in principle, the optical signal transmitted through the filter chip 4 is demultiplexed at a rate corresponding to the above ratio. That is, unlike the conventional structure, the branching / coupling ratio of this optical branching / coupling device does not depend on the parameter of the waveguide, but depends on the ratio of transmittance / reflectance of the arranged filter chip 4. And
This transmittance / reflectance ratio can be set to a desired value by appropriately selecting the conditions at the time of manufacturing the half mirror.

Therefore, at the time of forming the waveguides 1 and 2, the dimensions may be controlled so that the mode matching property with the optical fiber connected thereto and low propagation loss and coupling loss can be satisfied. Specifically, the accuracy of the core cross-sectional dimension is ± 0.5
The tolerance of μm and relative refractive index difference Δ may be controlled to be ± 0.03%. FIG. 2 is a schematic view showing another embodiment.
This optical branching / coupling device has the optical branching / coupling device having the structure shown in FIG. 1 as a constituent unit, the units are arranged in parallel on the same substrate, and a common half mirror 4a is arranged at each intersection. .

FIG. 3 is a schematic view showing still another embodiment. In this optical branching / coupling device, wavelength filters 6, 6, 6 for blocking crosstalk are further arranged in the waveguides 1, 1, 1 in the optical branching / coupling device shown in FIG. This optical branching / coupling device is useful when incorporated in an aurora system. In the optical branching / coupling device shown in FIG. 2, if the wavelength filter 6 is arranged instead of the common half mirror 4a, the crosstalk blocking function can be exerted similarly to the optical branching / coupling device shown in FIG. .

[0016]

As is apparent from the above description, in the optical branching / coupling device of the present invention, the branching / coupling ratio is defined by the transmissivity / reflectance ratio of the filter chips arranged at the intersections. Therefore, the control range of the accuracy of the waveguide parameter at the time of forming the waveguide can be loosened. Therefore, manufacturing is facilitated and a high yield can be realized.

[Brief description of drawings]

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

FIG. 2 is a schematic plan view showing another embodiment of the present invention.

FIG. 3 is a schematic plan view showing still another embodiment of the present invention.

FIG. 4 is a schematic plan view showing a Mach-Zehnder interferometer.

[Explanation of symbols]

 1 Waveguide 2 Waveguide 3 Intersection of Waveguide 1 and Waveguide 2 4 Filter Chip 4a Common Half Mirror 5 Slit 6 Wavelength Filter

Front page continuation (72) Inventor Ken Ueki 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Izumi Mikawa 1-1-6, Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph Phone Co., Ltd.

Claims (3)

[Claims] 1. A waveguide type optical branching / coupling device, wherein two waveguides intersect each other in an X shape and a filter chip is arranged at the intersection. 2. The waveguide type optical branching / coupling device according to claim 1, wherein the filter chip is a half mirror or a wavelength filter. 3. A plurality of patterns composed of two waveguides intersecting in an X shape are arranged in parallel, and one filter chip is arranged in common in all patterns at the intersection of each pattern. A waveguide type optical branching / coupling device characterized by the above.