JP2003241113A - Variable-wavelength optical filter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make small-sized a variable-wavelength optical filter comprising a stage where optical filter chips are arrayed by wavelengths. <P>SOLUTION: On a rotary stage 32, many optical filters 33 are arranged. The optical filters 33 have mutually different wavelength selection characteristics. Then incident light is made incident on one of the optical filters and its transmitted light is projected through a prism 25. The optical filter on which the light is incident is changed by rotating the rotary stage 32 to select a desired wavelength. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable optical filter device used in an optical communication system, an optical measuring device or the like and capable of varying a selected wavelength.

[0002]

2. Description of the Related Art Conventionally, a dielectric multilayer filter having a dielectric multilayer film formed on a substrate is widely known as an optical filter capable of changing a selected wavelength in optical communication and the like. The dielectric multilayer filter is configured by alternately stacking two kinds of dielectric substances having different refractive indexes on a glass substrate. A wavelength tunable filter device has been used in which a selected wavelength is tuned by selecting an optical filter using a large number of optical filters having different transmission wavelengths.

FIG. 8 is a sectional view showing a conventional wavelength tunable optical filter device. As shown in the figure, the optical fiber 1 on the incident side is connected to a housing 3 via a protective cap 2. A collimator 4 and a prism 5 that reflects this light upward are provided in the housing 3. Further, a prism 6, a collimator 7 and a protective cap 8 are provided at positions symmetrical to this, and an optical fiber 9 on the emission side is connected to the protective cap 8. A moving stage 10 is movably provided between the prisms 5 and 6. Moving stage 1
A plurality of optical filters 11 are arranged on the 0. Each optical filter 11 has different wavelength selection characteristics.
The moving stage 10 is moved in the direction of the arrow X axis by driving the motor 12, and its position is detected by the position sensor 13. Therefore, by moving the moving stage 10 in accordance with a signal from the outside and allowing the light to pass through one of the positions of the optical filter 11, the optical filter 1
1 can be selected, and a variable filter device that changes the selected wavelength can be realized.

However, in such a conventional tunable optical filter structure, the moving stage 10 is moved linearly in the X-axis direction. Therefore, as shown by the broken line on the right side of the figure,
It is necessary to secure a space 14 for moving the moving stage, which causes a problem that the tunable optical filter device becomes large in size. In particular, when the number of wavelengths to be selected is increased, it is necessary to increase the number of filters on the moving stage, and there is a drawback that the shape becomes large.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object thereof is to further reduce the product size.

[0006]

According to the invention of claim 1 of the present application, a rotary stage configured to be stopped at a desired rotation angle, and arranged on the rotary stage, have different wavelength selection characteristics from each other. A plurality of optical filters, an incident unit that makes incident light incident on the optical filter on the rotary stage from a predetermined direction, and an emission unit that emits light that has passed through the optical filter. To do.

According to a second aspect of the present invention, in the variable wavelength optical filter device according to the first aspect, the incident portion has a circulator that separates the reflected light.

[0008]

1 is an elevational view of a wavelength tunable filter device according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. 3 is a sectional view taken from a different direction. See also FIG.
Shows a perspective view of the main part of the wavelength tunable filter device. As shown in these figures, the optical fiber 21 for incidence is used.
Is connected to a housing 23 of the wavelength tunable filter device via a protective cap 22. A collimator 24 is provided in the housing 23. The collimator 24 collimates incident light into parallel light, and a right-angle prism 25 is arranged on the optical axis thereof through a filter described later. A collimator 26 is provided on the optical axis of the reflected light reflected by the rectangular prism 25 as shown in the figure, and a protective cap 27 and an optical fiber 28 for emission are connected to the end of the housing 23. Here, the incident optical fiber 21 and the protective cap 22,
The collimator 24 constitutes an incident unit that makes incident light incident on the optical filter on the rotary stage from a predetermined direction, and includes the prism 25, the collimator 26, and the protective cap 2.
7. The optical fiber 28 constitutes an emitting portion for emitting the light passing through the optical filter.

In this embodiment, the motor 31 rotates the rotary stage 32. The rotary stage 32 is a circular table which is rotatably held along the central axis, and a large number of optical filters 33 are vertically arranged on the upper part of the rotary stage 32 at a constant radial position on the circumference, as shown in FIG. ing. All of these optical filters 33 have different wavelength selection characteristics for each filter. A position sensor 34 for detecting a rotational position, for example, a rotary encoder is provided below the rotary stage 32.

The rotary stage 32 is configured to be stopped at a desired position by a selection signal from the outside. Each optical filter 33 is, for example, a bandpass filter capable of selecting the wavelength of each channel of the wavelength multiplexed light. For example, if the wavelengths of wavelength multiplexed light are λ ₁ , λ ₂ ,
When lambda ₃ · · ·, respectively lambda ₁ optical filter 33 to fit thereto, lambda _2, and a lambda ₃ · · · selected wavelength. Such a filter can be formed by laminating a dielectric multilayer film on a glass substrate. Further, the optical filter 33 may be one that selects light of a plurality of wavelengths such as λ ₁ and λ ₂ , λ ₃ and λ ₄ , and λ ₅ and λ ₆ , respectively.

When wavelength-multiplexed light is incident from the incident side optical fiber 21, the light reaches any one of the optical filters 33 via the collimator 24. Therefore, the optical filter 33
Only the light of the wavelength selected in passes through the optical filter 33,
The light is reflected by the rectangular prism 25 and is output to the optical fiber 28 on the emission side via the collimator 26. Then, by rotating the rotary stage 32, it is possible to make the light incident from the incident optical fiber 21 incident on different optical filters 33, and it is possible to select the wavelength.
Since the rotational position of the rotary stage 32 is detected by the position sensor 34, it is possible to change the rotational angle based on a control signal from the outside and thereby select the optical filter 33 on which the incident light enters. In this case, the optical filter 33 is placed upright on the rotary stage 32. However, if the light parallel to the collimator 24 from the incident optical fiber is perpendicular to the surface of the optical filter, the reflected light remains unchanged. It will be returned to the incident optical fiber. In order to avoid this, the optical filter 33 is set to ± 3 on the rotary stage, for example.
The rotary table 32 may be tilted at any angle, or the rotary table 32 may be stopped so that the incident light enters at a slightly tilted angle. In this way, the reflected light is incident on the optical fiber 21.
Will never return to.

Next, a second embodiment of the present invention will be described. In this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, as shown in FIG. 5, the optical filter 33 on the rotary stage 32 is arranged upright with respect to the incident light, and the circulator 41 is provided in the middle of the optical fiber 21 on the incident side as shown in the figure. . Other configurations are the same as those in the first embodiment described above. In this way, when the incident light is incident in the same manner as described above, the reflected light returns to the optical fiber 21. Then, the reflected light can be separated by the circulator 41 to be output on the reflecting side. In this way, the light of the wavelength not selected by the optical filter 33 can be taken out as the output on the reflection side, so that the 3-port type optical branching device can be realized.

Next, a third embodiment of the present invention will be described. In the first and second embodiments described above, the optical filter is placed upright on the rotary stage, but the optical filter 33 may be placed parallel to the upper surface of the rotary stage 32. In this case, as shown in the schematic view of FIG.
The light is reflected along the rotary stage 32 from 4. On the rotary stage 32, the optical filter 33 similar to that of the above-described embodiment is arranged on the same circumference with a slight inclination from the surface. The surface of the rotary stage 32 through which the light passes is made transparent. In this way, only the light of the selected wavelength of the incident light can be transmitted through the optical filter 33, reflected by the rectangular prism 52 provided below it, and output from the optical fiber 28 on the emission side.

FIG. 7 is a perspective view showing a wavelength tunable filter device according to a fourth embodiment. In the present embodiment, the circulator 41 is provided in the optical fiber 21 on the input side of the wavelength tunable optical filter device shown in FIG. In this case, the optical filter 33 on the rotary stage 32 is arranged so as to be orthogonal to the incident light. By doing so, the reflected light returns to the optical fiber 21 as it is through the right-angle prism 51.
Therefore, the output directly reflected by the circulator 41 can be branched to form a 3-port type optical branching device.

Although the present embodiment describes a bandpass filter type optical filter device for selecting a specific wavelength, the present invention is applied to other types of optical filter devices such as band elimination filters. You can also

[0016]

As described in detail above, according to the present invention, a large number of optical filters are arranged on the rotary stage.
The wavelength is selected by rotating the rotary stage. Therefore, the wavelength tunable filter device can be downsized, and the time for changing the wavelength tunable filter device can be shortened. In particular, when the optical filters are continuously arranged from the short wavelength side to the long wavelength side, it is possible to significantly shorten the moving time from the shortest wavelength to the longest wavelength as compared with the conventional one. In addition, it is easy to increase the number of filters and it is possible to increase the number of channels. Further, since the stage is a rotary type, there is no mechanical biting, and the rotating mechanism itself can be simplified.

[Brief description of drawings]

FIG. 1 is an elevation view of a wavelength tunable optical filter device according to a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the casing of the wavelength tunable optical filter device according to the present embodiment taken along the long axis direction.

FIG. 3 is a vertical sectional view of the casing of the wavelength tunable optical filter device according to the present embodiment taken along the minor axis direction.

FIG. 4 is a perspective view showing a main part of the optical filter device according to the present embodiment.

FIG. 5 is a perspective view showing a main part of a wavelength tunable optical filter device according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a main part of a wavelength tunable optical filter device according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a main part of a wavelength tunable optical filter device according to a fourth embodiment of the present invention.

FIG. 8 is an elevational view of a conventional wavelength tunable optical filter device.

[Explanation of symbols]

21,28 optical fiber 22,27 Protective cap 23 housing 24,26 Collimator 25,51,52 Right angle prism 32 rotation stages 33 Optical filter 34 Position sensor 41 Circulator

Claims (2)

[Claims] 1. A rotary stage configured to be stopped at a desired rotation angle, a plurality of optical filters arranged on the rotary stage and having different wavelength selection characteristics, and an optical filter on the rotary stage. A wavelength tunable optical filter device comprising: an incident unit that makes incident light incident from a predetermined direction, and an emitting unit that emits light that has passed through the optical filter. 2. The wavelength tunable optical filter device according to claim 1, wherein the incident unit has a circulator that separates the reflected light.