JPH0456818A - Optical brancher/coupler and its production - Google Patents

Abstract

PURPOSE:To reduce a branch loss and to obtain parts to be used for optical branching and coupling without especially determining an I/O direction by setting up a light control member to be arranged on a branch part on an optimum position. CONSTITUTION:A light control layer 14 is formed on the light control member 13 to be moved in a groove 16 formed on an intersecting pat between both optical guides 9, 10. The groove 16 is formed in a direction inclined from a direction vertical to a center bisector between the optical axes of both the optical waveguides 9, 11 i.e. the same direction of the layer 14, only by theta. Thereby, the layer 14 is moved in parallel with its thickness direction due to the movement of the member 13 and the layer 14 and an intersecting point between the center lines of both the waveguides 9, 10 coincides with the layer 14. Consequently, the optical brancher/coupler capable of executing optical branching and coupling of low loss can be obtained.

Description

[Detailed Description of the Invention] <Industrial Utilization Public Expenses> The present invention is applicable to optical communication, optical signal processing, etc.
This invention relates to an optical branching coupler that performs optical branching and optical coupling.

<Conventional technology> As a simple configuration method for an optical splitter that divides input light into two,
There is something like the one shown in Figure 6 (tl, Yanagaw
a, et, m! ,, 'Filter-Embedde
dDssign and Tts Application
ons to Passive Components'
, IEEE J, Light*ave Tecbn
ol,, vol.

(See LT-7, pp. 1846-1653.1989).

In Fig. 6, Fig. 6(a) is a plan view, Fig. 6(b)
is its cross section, 1, 2, 3 are optical fibers, 4 is a thin wavelength filter that divides the propagating light of fiber 1 into transmitted light and reflected light, 5 is a groove for arranging the optical filter, and 6 is a groove. A substrate for fixing a fiber and an optical filter is shown, respectively. With this configuration, for example, if a wavelength filter 4 that transmits light with wavelength λ1 and reflects light with wavelength ~ is used, two wavelength components propagating through optical fiber 1 can be used.
Among □ and ^2, the transmitted wavelength component λ is guided to the output optical fiber 2, and the reflected wavelength component λ2 is guided to the output optical fiber 3.

This optical splitter is constructed by fixing optical fibers 1 and 2 (in this state, both optical fibers are not cut) and optical fiber 3 into fiber guide grooves previously provided on a substrate 6 with adhesive or the like. A groove 5 is formed across the branch. A wavelength filter 4 is placed in this groove 5 and fixed with adhesive.

As can be seen from this process, optical fiber 1 and optical fiber 2 are originally the same fiber, and since they were cut while being fixed, their optical axes coincide. Furthermore, by making the groove for arranging the filter several tens of μm or less, the light emitted from the optical fiber 1 can be
After passing through the wavelength filter, it is coupled to the optical fiber 2 without suffering much loss.

<Problems to be Solved by the Invention> However, it is not easy to couple the reflected light to the optical fiber 3 with low loss. This situation will be explained with reference to a detailed diagram of the branch section in FIG.

In Fig. 7, Fig. 7(a) shows when coupling with low loss,
Figure 7 (bl is the case where the loss becomes large. 7 in the figure)
8 is a dielectric multilayer film portion of the wavelength filter, 8 is a transparent substrate portion, and the other parts are the same as in FIG. In the case of FIG. 7(a), the intersection of the optical axes of the optical fibers 1 and 3, that is, the branch point, coincides with the film surface of the dielectric multilayer film 7.
In figure (b), they do not match.

Therefore, in the case shown in FIG.
incident on . In such a case, for example, fibers 1 and 3
If a single mode fiber with a relative refractive index difference of 0.3% and a core diameter of around 10 μm is used, a loss of 2 dB or more will occur if the position of the reflection point shifts by just 5 μm. Therefore, the loss is 2
In order to achieve a value of dB or less, the positional accuracy of the groove 5 that determines the reflection point of the wavelength filter 4 must be 5 μm or less, but it is difficult to obtain such accuracy with good reproducibility by mechanical processing.

In order to avoid this problem, it has been proposed that if a fiber with a large core diameter and aperture (NA) is used as the optical fiber 3, the reflected light can be coupled to the optical fiber 3 with low loss. According to the above literature, if a single mode fiber with a core diameter of 10 μm and a relative refractive index difference of 0.3% is used as the optical fiber 1, and a multimode fiber with a core diameter of 50 μm and a relative refractive index difference of 1% as the optical fiber 3, the reflection will be reflected. The optical coupling loss is about 0.3 dB. In this case, the position of the reflection point may vary by about ±20 μm, so the wavelength filter 4
The machining accuracy of the groove that fixes it is quite loose.

However, with this method, the mode changes while propagating through the optical fiber 3, and if the direction of the light is reversed, almost no light is coupled from the optical fiber 3 to the optical fiber 1, so it cannot be used as an optical coupler. has the disadvantage that it does not work.

The above also applies to the optical waveguide type splitter in which the optical fiber gold optical waveguide is replaced in FIG.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an optical branching/coupling device capable of performing low-loss optical branching and coupling, and a method for manufacturing the same.

Means for Solving the Problems> The configuration of the optical branching coupler according to the present invention for achieving the above object is an optical branching coupler/device having an optical control layer for branching and coupling input light to the intersection of optical waveguides. In the above, the light control layer is provided in a light control member movable within a groove formed at the intersection of the guiding waveguide, and the moving direction of the light control member is a direction intersecting the light control layer and the light control layer is It is characterized in that the light control layer moves in parallel in its thickness direction due to movement of the control member.

Further, the method for manufacturing an optical branching coupler according to the present invention includes a step of forming a groove at the intersection of intersecting optical waveguides, disposing a light control member in the groove, and moving the light control member along the groove. and fixing the light control member at a position where the point where the center lines of the optical waveguides intersect and the light control layer of the light control member match.

Further, in the optical branching coupler having the above configuration, an optical fiber is used instead of the optical waveguide, and in the method for manufacturing the optical branching coupler having the above configuration, an optical fiber is used instead of the waveguide. It is characterized by

Function> In the present invention, when the light control element is disposed in a groove, the light control layer constituting the light control element is a light control layer that is movable in the groove formed at the intersection of the guiding waveguides. The light control member is provided in the member, and when the moving direction of the light control member intersects the light control layer and the movement of the light control member causes the light layer to move in parallel in its thickness direction, light control is performed as a result. Since the layer is inclined with respect to the groove, by moving the light control element along the groove, the light control layer can be aligned with the intersection of the intersecting optical waveguides or optical fibers. Therefore, reflected light can be coupled to an optical waveguide or optical fiber with low loss.

Example of implementation A preferred embodiment of the present invention will be described below.

FIG. 1 shows a first embodiment of an optical branching/coupling device of the present invention, which branches or couples different wavelengths, and is an example of application to a so-called optical branching device or optical multiplexer. 9 and 10 in the figure
．． 11 is the core of the guiding waveguide, 12 is the cladding of the optical waveguide,
13 is a wavelength filter as a light control member, and 16 is a groove. As shown in the perspective view of FIG. 2, the wavelength filter 13 is
A multilayer film part 14 as a light control layer that divides incident light into transmitted light and reflected light, and a wedge-shaped glass part 15.15 that sandwiches the multilayer film part 14.
The film surface of the multilayer film portion 14 is at a predetermined angle θ with respect to the two mutually parallel surfaces 17 and 18 of the glass, and has an overall thickness of t.

A method of manufacturing this optical splitter will be explained using FIG. First, the groove 16 is formed so as to include the intersection point of the optical axes of the optical waveguides 119 and 11, that is, the branch point.

This groove 16 is formed at the center 2 of the optical axis of the optical waveguides 9 and 11.
It is formed in a direction inclined by θ from the direction perpendicular to the equal dividing line.

The purpose of tilting by θ is to align the film surface of the multilayer film portion 14 with the direction perpendicular to the central bisector of the optical axes of the optical waveguides 9 and 11 when the wavelength filter 13 is inserted into the groove. Groove 1
The width of 6 is set to be slightly wider than the thickness of the wavelength filter 13. After that, the wavelength filter 13 is inserted into the groove 16, and while the light is introduced from the optical waveguide 9 and the optical output intensity of the optical waveguide 11 is monitored, the wavelength filter 13 is inserted into the groove 16.
move it along. The wavelength filter 13 is fixed at a position where the amount of monitored light is maximum.

Note that the intensity of light transmitted through the optical wavelength filter 13 and output from the optical waveguide 10 is constant regardless of the position of the wavelength filter 13.

In this way, the input light λ1. In an optical branching/coupling device having a light control layer 14 for branching and coupling λ2, the light control layer 14 is an optical waveguide @
The optical control member 13 is provided so as to be movable in a groove 16 formed at the intersection of the optical waveguides 9 and 10, and the groove 16 is located at the center bisector of the optical axis of the optical waveguide 9 and the optical waveguide 11. Since it is formed in a direction tilted by θ from the vertical direction, that is, the same direction as the light control layer 14, the movement direction of the light control member 13 is a direction that intersects the light control layer, and the movement of the light control member 13 causes the light to change. The control layer 14 will move in parallel in its thickness direction, and the point where the center lines of the optical waveguides 9 and 10 intersect will coincide with the optical control layer 14.

An optical splitter was manufactured using the method described above. The wavelength filter 13 as a light control member transmits a wavelength of 1.3 μm and has a wavelength of 1.5 μm.
A dielectric multilayer film 14 (alternating films of titanium dioxide and silicon dioxide) as a light control layer designed to reflect wavelengths of μm is sandwiched between glasses, and its thickness t1 is , each 45μm12x4m2. The leading waveguides 9 to 11 have a substrate thickness of 0.7 mm and a core diameter of 8 x 8.
It is a silica-based glass waveguide with a relative refractive index difference of 0.25%. A silica glass optical waveguide is usually fabricated on a Si substrate by soot deposition, vitrification treatment, and patterning by dry etching (Wanai: "Waveguide type optical circuit element", Optronics, vol. 80. p. 85)
(1989, 9)).

Furthermore, the groove 16 was formed with a width of 50 μm using a commercially available dicing saw.
250 μm in depth. The branching angle (the angle between the optical waveguide 9 and the optical waveguide 11) was selected to be 30 degrees so as not to be affected by the polarization dependence of the dielectric multilayer film. When light with a wavelength of 1.3 μm is input from the optical waveguide 9 of the fabricated optical splitter, its output is transmitted from the optical waveguide 10 and from the optical waveguide I.
When light with a wavelength of 1.5 μm was input from I9, its output was emitted from the leading waveguide 11. At this time, from the ratio of the input light amount to the output light amount, the loss is 0.5 dB for the 1.3 μm light transmitted through the wavelength filter, and the loss is 0.5 dB for the 1.5 μm light reflected by the wavelength filter 13. 7dB was obtained. Furthermore, the loss was the same even if the input and output of light were reversed.

From this, the positional accuracy of the wavelength filter was calculated to be within ±2 μm, confirming the effectiveness of the present invention.

FIG. 3 shows a second embodiment of the optical branching coupler of the present invention, which differs from the first embodiment in that an optical fiber is used instead of an optical waveguide. In the figure, 19, 20, 21 are optical fibers, 22 is a wavelength filter as a light control member, 22
Reference numeral a indicates a multilayer film part as a light control layer provided in the wavelength filter, 23 indicates a groove in which the wavelength filter is disposed, and 24 indicates a substrate for fixing the optical fiber. When using this optical fiber, grooves 26 for fixing the optical fibers 19 to 21
It is necessary to prepare in advance a substrate 24 on which are respectively formed.

The optical fibers 19, 20, 21 have an outer diameter of 125 μm1
When a single mode fiber with a core diameter of 10 μm and a relative refractive index difference of 0.3% was fabricated using the same wavelength filter 22 as in the first embodiment, the loss of transmitted light was the same as that in the first embodiment. However, the loss of reflected light was slightly larger. This is because the reflected light increases when propagating through the cladding of the optical fiber 19.

FIG. 4 shows a third embodiment of the optical branching coupler of the present invention, in which a polarization separation film is used as the light control member. In FIG. 4, 25, 26, 27 are the cores of the optical waveguides, 28 are the claddings, 29 are the polarization separation filters, and 30
is a groove. Optical waveguide core 25 and optical waveguide core 27
Although the case where the branching angle with respect to the light beam is 90 degrees is shown, it is not limited to this angle (many commonly used polarization separation prisms have this angle). With this configuration, the light propagating through the core 25 of the optical waveguide is separated into a polarization component parallel to the substrate and a polarization component perpendicular to the substrate.
．． It is output from 27.

In the case of an optical waveguide, since it has polarization maintaining property due to the asymmetry of its structure, it is advantageous in that the polarization direction after separation is maintained in a constant direction within the output waveguide.

A polarization separator was manufactured using an optical waveguide with a branching angle of 90 degrees using the same parameters as in the first example. polarizing filter 2
9 also had the same dimensions as those in FIG. However, multilayer film 29
A is designed for polarization separation (the structure is the same alternating films of titanium dioxide and silicon dioxide as in the wavelength filter). By fixing the polarizing filter 29 at the optimum point, the same 0.5 to 0.7 dB as in the first embodiment
A relatively low loss characteristic was obtained. This loss remained the same even if the input and output were swapped.

A fourth embodiment of the present invention uses optical fibers in place of the optical waveguides 25 to 27 in the third embodiment shown in FIG. The optical fiber used is preferably a polarization-maintaining optical fiber in order to maintain the polarization direction.

FIG. 5 shows a fifth embodiment of the optical branching/coupling device of the present invention, in which a plurality of optical branching devices are fabricated on the same substrate. In FIG. 5, 31, 32, 33 are array-shaped optical waveguide core parts, 34 is a cladding part of the optical waveguide, 3
5 is a light control member, 36 is a multilayer film portion of the light control member, 37
is a groove. In the figure, after the light control member 35 is moved along the groove 37, the film surface of the multilayer film 36 and the branching points of the four pairs of optical waveguides shown by dotted lines are drawn to coincide with each other.

In the sixth embodiment of the present invention, for example, Aj
, Cr, Au, or other metal films are used. In this case, it is possible to obtain an optical splitter or optical coupler that separates incident light into reflected light and transmitted light at a specific ratio.

In the method described above, the waveguide and the groove are provided on the X-Y axis plane of the coordinates, but the present invention is not limited to this, and the waveguide or optical fiber is provided on the X-Y axis plane of the coordinates. , grooves may be provided in the Z-axis direction.

<Effects of the Invention> As explained above, in the optical branching device according to the present invention, the light control member disposed at the branching part can be set at an optimal position.
It has the effect of reducing branch loss. In addition, in the optical splitter according to the present invention, the input optical waveguide or optical fiber and the optical waveguide or optical fiber for branch output can be configured with the same parameters, so there is no need to specifically determine the direction of input and output, and optical branching and optical coupling We can provide parts that can be used for both purposes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical branching coupler according to a first embodiment of the present invention, FIG. 2 is a perspective view of a light control member of this embodiment, and FIG. 3 is an optical branching coupler according to a second embodiment. Schematic diagram of , Figure 4 is the 3rd
A schematic diagram of an optical branching coupler according to an embodiment, FIG. 5 is a schematic diagram of an optical branching coupler according to a fifth embodiment, FIG. 6 is a schematic diagram of an optical branching coupler according to a conventional example, and FIG. It is a partially enlarged view. In the drawings: 1, 2.3. 19.20. 21 is an optical fiber; 4.
13.22 is a wavelength filter; 5.16, 23, and 30 are grooves; 6 is a substrate for fixing an optical fiber; 7.14 is a dielectric multilayer film portion of the wavelength filter; 8.15 is a substrate portion of the wavelength filter; 9. 10, 11, 25, 26, 27, 31° 32.33
is the core of the optical waveguide, 12, 28 and 34 are the claddings of the optical waveguide, 24 is the substrate, and 29 is a polarization separation filter.

Claims (1)

[Claims] 1) In an optical branching/coupling device having an optical control layer for branching and coupling input light at the intersection of optical waveguides, the optical control layer moves within a groove formed at the intersection of the optical waveguides. is provided on a possible light control member,
An optical branching/coupling device characterized in that the moving direction of the light controlling member is a direction intersecting the light controlling layer, and the moving direction of the light controlling member causes the light controlling layer to move in parallel in its thickness direction. 2) forming a groove at the intersection of the intersecting optical waveguides;
A light control member is disposed in the groove, and the light control member is moved along the groove to control the light at a position where the point where the center line of the optical waveguide intersects with the light control layer of the light control member. A method for manufacturing an optical branching coupler, comprising a step of fixing members. 3) The optical branching coupler according to claim 1, wherein an optical fiber is used in place of the optical waveguide. 4) The method of manufacturing an optical branching coupler according to claim 2, wherein an optical fiber is used in place of the optical waveguide. 5) The optical branching coupler according to claim 1 or 3, wherein the optical control layer is a dielectric multilayer film or a metal film.