JP3362696B2 - Tunable optical filter - Google Patents

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 applied to an optical fiber communication system or the like.

[0002]

2. Description of the Related Art Conventionally, variable wavelength optical filters are generally applied to optical fiber communication systems. In the field of optical fiber communication, various optical filters such as a low-pass optical filter, a high-pass optical filter, and a band-pass optical filter are used for the purpose of extracting light of a desired wavelength from wavelength-multiplexed light. Has been done. In such an optical filter, it is desirable that the cutoff wavelength and the center wavelength of the pass band are variable in order to cope with the wavelength variation of the light source or the variation of the wavelength.

FIG. 2 is a diagram for explaining the configuration and operation of the variable wavelength optical filter of the first conventional example. This wavelength tunable optical filter includes an incident-side optical fiber 21, a first lens 22 for converting the light emitted from the optical fiber 21 into a parallel beam, and a second lens 2 for converging the parallel beam.
3 and an output side optical fiber 24 on which this converged light enters
And a filter film 25 provided between the first lens 22 and the second lens 23 so as to cross the parallel beam. This filter film 25 is supported on a transparent substrate 26, and the substrate 26 on which the filter film 25 is mounted is
It is rotatably supported around 7.

In the tunable optical filter of the conventional example 1 configured as above, when the substrate 26 is rotated, the incident angle of the parallel beam on the filter film 25 changes. Filter membrane 2
The optical characteristics of No. 5 change depending on the incident angle, so that the substrate 2
By rotating 6 the cutoff wavelength of this optical filter and the center wavelength of the pass band can be changed.

The "variable wavelength optical filter" of Japanese Patent Application Laid-Open No. 5-257068, which is a second conventional example having a similar technical field to the present invention, is capable of moving a curved filter film in a direction substantially perpendicular to the main axis of a parallel light beam. It is provided in.

[0006]

However, when the substrate 26 is rotated to change the wavelength characteristics of the wavelength tunable optical filter as described above, the filter film 25 is caused by refraction of light by the substrate 26 having a finite thickness. The parallel beam emitted from the optical disc shifts from the parallel beam incident on the substrate 26. If the light beam on the output side is deviated from the light beam on the input side, excessive coupling loss occurs in the coupling of the second lens 23 with the output side optical fiber 24. Therefore, there arises a problem that the insertion loss of the wavelength tunable optical filter fluctuates as the wavelength changes.

The present invention has been made in view of the problems of the above-mentioned conventional technique, and an object of the present invention is to provide a wavelength tunable optical filter in which fluctuations in insertion loss due to wavelength changes do not occur. .

[0008]

To achieve the above object, a wavelength tunable optical filter according to the present invention comprises an incident side optical fiber and an outgoing side optical fiber, which are installed to face the same optical axis, and an incident side optical fiber. And a filter film whose filter characteristics change with respect to the transmitted light according to a change in the incident angle to the film surface between the output side optical fiber and the output side optical fiber, and a columnar body confining the filter film with each rectangular flat surface facing each other. The optical filter unit has two semi-cylindrical translucent bodies, and the angle is variable with respect to the optical axis of the optical filter unit.

The wavelength tunable optical filter according to claim 1 further comprises a turntable for varying the surface angle of the filter film with respect to the optical axis, and the optical filter unit is mounted on the turntable. The rotary table and the cylindrical optical filter unit described in Item 2 may be mounted on the same rotary shaft.

According to a fourth aspect of the present invention, the incident side optical fiber and the outgoing side optical fiber according to the second or third aspect,
The turntable on which the optical filter unit is mounted may be installed and configured on one substrate.

Further, the incident side optical fiber and the emitting side optical fiber according to claim 4 are respectively fixed to a supporting member mounted on the substrate, and the supporting member according to claim 5 is further provided with an incident side optical fiber. It is preferable that a collimator lens is fixed to each of the rear side of the optical fiber and the front side of the emission side optical fiber.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the tunable optical filter according to the present invention will be described in detail with reference to the accompanying drawings. Referring to FIG. 1, there is shown one embodiment of the tunable optical filter of the present invention. FIG. 1 is a perspective external view showing a configuration example of a wavelength tunable optical filter according to an embodiment.

In FIG. 1, the wavelength tunable optical filter of this embodiment is sandwiched between a first glass block 12 and a second glass block 13 which are semi-cylindrical light-transmitting bodies, and both glass blocks. A cylindrical optical filter unit 11 is constituted by the filter film 14 which is an optical filter.

In the tunable optical filter having the above structure,
In order to change the filter characteristics, the incident angle of the incident beam on the filter film 14 is changed. In order to cause this change, the optical filter unit 11 is rotated. In this rotation, the state of the glass block, which is a cylindrical light-transmitting body through which the parallel beam is transmitted, is kept constant with respect to the incident beam. The purpose of keeping this constant state is to keep the optical axis constant before and after entering the optical filter and to ensure the stability of the optical filter characteristics. The contents of this configuration will be described in detail below.

In FIG. 1, an incident side optical fiber unit 2 and an emitting side optical fiber unit 3 are provided on a substrate 1,
They are installed so that they face each other and their optical axes coincide with each other. The incident side optical fiber unit 2 is configured by disposing the first collimating lens 5 and the incident side optical fiber 6 on the first supporting member 4. Similarly, the emission side optical fiber unit 3 is configured by disposing the second collimating lens 8 and the emission side optical fiber 9 on the second support member 7.

A turntable 10 is installed on the substrate 1. An optical filter unit 11 is installed on the turntable 10. The optical filter unit 11 has a cylindrical shape,
The first glass block 12 and the second glass block 13, and the filter film 14 sandwiched between the glass blocks 12 and 13. First glass block 1
2 and the second glass block 13 have the same semi-cylindrical shape. The rotation center axis of the turntable 10 and the rotation center axis of the cylinder of the optical filter unit 11 are arranged so as to coincide with each other. The optical filter unit 11 is rotated about the rotation center axis by the turntable 10.

Next, the operation of the tunable optical filter shown in FIG. 1 will be described. First, the light that has entered the incident-side optical fiber 6 is converted into a parallel beam by the first collimator lens 5 and enters the optical filter unit 11. Here, the parallel beam is incident on the second collimator lens 8 after being subjected to the optical filter action, is condensed, and is emitted from the optical fiber 9 on the output side.
Bind to.

The optical filter unit 11 is rotated so that desired filter characteristics are obtained, and the incident angle of the parallel beam with respect to the filter film 14 is changed. Here, even when the cylindrical optical filter unit 11 is rotated, the state of the cylindrical glass block through which the parallel beam is transmitted with respect to the incident light is constant. Therefore, the excessive loss due to the deviation of the parallel beam does not occur unlike the conventional case.

The above-described embodiment is an example of a preferred embodiment of the present invention. However, it is not limited to this,
Various modifications can be made without departing from the scope of the present invention.

[0020]

As is apparent from the above description, the wavelength tunable optical filter of the present invention has two semi-cylindrical light-transmitting bodies,
An optical filter unit is formed by forming a filter film whose filter characteristics change with respect to transmitted light according to a change in an incident angle on the film surface into a columnar body having a rectangular flat surface facing each other. Therefore, since the light transmission state of the cylindrical glass block through which the parallel beam is transmitted is constant regardless of the angle of the filter film, the parallel beam direction is not displaced. Therefore, the variation of the insertion loss of the wavelength tunable optical filter does not occur.

[Brief description of drawings]

FIG. 1 is a perspective external view showing an embodiment of a wavelength tunable optical filter of the present invention.

FIG. 2 is a diagram for explaining the configuration and operation of a wavelength tunable optical filter of Conventional Example 1.

[Explanation of symbols]

1 substrate 2 Incident side optical fiber unit 3 Output side optical fiber unit 4 First support member 5 First collimating lens 6 Incident side optical fiber 7 Second support member 8 Second collimating lens 9 Output side optical fiber 10 turntable 11 Optical filter unit 12 First glass block 13 Second glass block 14 Filter membrane

Claims (6)

(57) [Claims] 1. According to a change in an incident angle to a film surface between an incident side optical fiber and an outgoing side optical fiber, which are installed to face each other on the same optical axis, and the incident side optical fiber and the outgoing side optical fiber. And a filter film whose filter characteristics change with respect to transmitted light, and two semi-cylindrical light-transmitting bodies that form an optical filter unit by forming a columnar body in which the respective rectangular planes face each other and enclose the filter film. And a variable wavelength optical filter having a variable angle with respect to the optical axis of the optical filter unit. 2. The wavelength tunable optical filter according to claim 1,
Further, the wavelength tunable optical filter is characterized in that it has a turntable for varying a surface angle of the filter film with respect to the optical axis, and an optical filter unit is mounted on the turntable. 3. A wavelength tunable optical filter, wherein the turntable and the cylindrical optical filter unit according to claim 2 are mounted on the same rotary shaft. 4. The wavelength according to claim 2, wherein the incident side optical fiber and the emission side optical fiber according to claim 2 and the turntable on which the optical filter unit is mounted are installed and configured on one substrate. Variable optical filter. 5. The wavelength tunable optical filter according to claim 4, wherein the incident side optical fiber and the emission side optical fiber are fixed to a supporting member mounted on a substrate, respectively. 6. The support member according to claim 5, further comprising:
A tunable optical filter, characterized in that collimator lenses are respectively fixed on the rear side of the incident side optical fiber and the front side of the emitting side optical fiber.