JP2000292715A - Wavelength variable optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wavelength variable optical filter which does not cause changes in the insertion loss accompanied by the wavelength changes. SOLUTION: An optical fiber 6 in the entrance side and an optical fiber 9 in the exit side are disposed facing each other on one optical axis in an optical fiber unit 2 in the entrance side and an optical fiber unit 3 in the exit side, respectively. A filter film 14 which changes its filtering characteristics for the transmitted light according to the changes in the incident angle on the filter face is interposed between a first glass block 12 and a second glass block 13 which are two semicylindrical light-transmitting bodies into one cylindrical body to constitute an optical filter unit 11, and this unit 11 is disposed between the optical fibers 6, 9 in the entrance side and in the exit side. The optical filter unit 11 is mounted on a rotating bed 10 with the variable angle of the unit 11 to the optical axis. By this constitution, the transmitting state for light of the cylindrical glass block where parallel beams transmit is made const. without depending on the angle of the filter film 14, and no misalignment in the direction of the parallel beams is caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tunable optical filter applied to an optical fiber communication system and the like.

[0002]

2. Description of the Related Art Conventionally, a wavelength tunable optical filter is generally applied to an optical fiber communication system or the like. 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, for example, extracting light of a required wavelength from wavelength-multiplexed light. Have been. 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 fluctuation or the wavelength fluctuation of the light source.

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

In the wavelength tunable optical filter of the first conventional example configured as described above, when the substrate 26 is rotated, the angle of incidence of the parallel beam on the filter film 25 changes. Filter membrane 2
5 changes according to the incident angle.
By the rotation of 6, the cutoff wavelength of the optical filter and the center wavelength of the pass band can be changed.

A "tunable wavelength optical filter" disclosed in Japanese Patent Application Laid-Open No. 5-257068 as a second conventional example similar to the present invention can move a curved filter film in a direction substantially perpendicular to the main axis of a parallel light beam. Is provided.

[0006]

However, when the substrate 26 is rotated to change the wavelength characteristics of the tunable optical filter as described above, the filter film 25 is refracted by the substrate 26 having a finite thickness. Is shifted from the parallel beam incident on the substrate 26. If the light beam on the output side is shifted with respect to the light beam on the incident side, excess loss occurs in coupling to the output side optical fiber 24 by the second lens 23. Therefore, there is a problem that the insertion loss of the tunable optical filter varies with the wavelength change.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a tunable optical filter in which the insertion loss does not fluctuate due to a wavelength change. .

[0008]

In order to achieve the above object, a tunable optical filter according to the present invention comprises an input side optical fiber, an output side optical fiber, and an input side optical fiber which are installed to face the same optical axis. A filter film whose filter characteristics change with respect to transmitted light in accordance with a change in the incident angle to the film surface between the optical fiber and the output side optical fiber, and a columnar body which faces the respective rectangular planes and sandwiches the filter film. The optical filter unit has two semi-cylindrical light-transmitting members constituting the optical filter unit, and is characterized in that the angle is variable with respect to the optical axis of the optical filter unit.

The tunable optical filter according to the first aspect of the present invention further comprises a turntable for changing the surface angle of the filter film with respect to the optical axis, and the optical filter unit is mounted on the turntable. It is preferable that the turntable and the columnar optical filter unit described in Item 2 are mounted on the same rotation shaft.

According to a fourth aspect of the present invention, there is provided the input side optical fiber and the output 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.

The incident-side optical fiber and the outgoing-side optical fiber according to claim 4 are respectively fixed to a support member mounted on a substrate, and the incident-side optical fiber and the output-side optical fiber are further fixed to the support member according to claim 5. It is preferable that the collimating lenses are fixed to the rear side of the optical fiber and the front side of the emission side optical fiber, respectively.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a 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 illustrating a configuration example of a wavelength tunable optical filter according to an embodiment.

In FIG. 1, the wavelength tunable optical filter according to the present embodiment is sandwiched between a first glass block 12 and a second glass block 13, which are semi-cylindrical light-transmitting members, and both glass blocks. The optical filter unit 11 having a cylindrical shape is constituted by the filter film 14 which is an optical filter.

In the tunable optical filter having the above configuration,
In order to change the filter characteristics, the angle of incidence of the incident beam on the filter film 14 is changed. In order to make 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 passes, is kept constant with respect to the incident beam. The purpose of keeping this constant state is to keep the optical axis before and after the light enters 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 exit 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. The incident side optical fiber unit 2 is configured by arranging a first collimating lens 5 and an incident side optical fiber 6 on a first support member 4. Similarly, the output side optical fiber unit 3 is configured by arranging a second collimating lens 8 and an output side optical fiber 9 on a second support member 7.

A turntable 10 is set on the substrate 1. An optical filter unit 11 is installed on the turntable 10. The optical filter unit 11 has a cylindrical shape,
It is composed of a first glass block 12 and a second glass block 13, and a filter film 14 sandwiched between the two glass blocks 12, 13. First glass block 1
The second and second glass blocks 13 have the same semi-cylindrical shape. The rotation center axis of the turntable 10 and the rotation center axis of the column 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 wavelength 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 collimating lens 5 and enters the optical filter unit 11. Here, after being subjected to the optical filter action, the parallel beam enters the second collimating lens 8, is condensed, and is focused on the output side optical fiber 9.
To join.

By rotating the optical filter unit 11 so as to obtain desired filter characteristics, the incident angle of the parallel beam on the filter film 14 is changed. Here, even if the cylindrical optical filter unit 11 is rotated, the state of the cylindrical glass block through which the parallel beam passes with respect to the incident light is constant. For this reason, there is no excess loss due to the displacement of the parallel beam as in the related art.

The above 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 spirit of the present invention.

[0020]

As is apparent from the above description, the wavelength tunable optical filter of the present invention comprises two semi-cylindrical light-transmitting members.
The filter film whose filter characteristics change with respect to the transmitted light in accordance with the change in the incident angle to the film surface is formed as a single columnar body with its rectangular planes facing each other to form an optical filter unit. Therefore, since the light transmission state of the cylindrical glass block through which the parallel beam passes is constant regardless of the angle of the filter film, no deviation occurs in the direction of the parallel beam. Therefore, the insertion loss of the tunable optical filter does not change.

[Brief description of the drawings]

FIG. 1 is a perspective external configuration diagram 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 according to Conventional Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Incident-side optical fiber unit 3 Outgoing-side optical fiber unit 4 First supporting member 5 First collimating lens 6 Incident-side optical fiber 7 Second supporting member 8 Second collimating lens 9 Outgoing-side optical fiber 10 Rotation Table 11 Optical filter unit 12 First glass block 13 Second glass block 14 Filter film

Claims (6)

[Claims] 1. An incident-side optical fiber and an exit-side optical fiber installed opposite to the same optical axis, and the incident-side optical fiber and the exit-side optical fiber respond to a change in an incident angle to a film surface. A filter film whose filter characteristics change with respect to transmitted light, and two rectangular light-transmitting members, each of which has a rectangular plane opposed to each other and is a columnar body sandwiching the filter film, forming an optical filter unit A wavelength tunable optical filter comprising: an optical axis of the optical filter unit; 2. The tunable optical filter according to claim 1,
The wavelength tunable optical filter further includes a turntable for changing 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 columnar optical filter unit according to claim 2 are mounted on the same rotation axis. 4. A wavelength base characterized in that the turntable on which the input side optical fiber and the output side optical fiber according to claim 2 and the optical filter unit are mounted is installed and configured on one substrate. Variable optical filter. 5. The wavelength tunable optical filter according to claim 4, wherein the input side optical fiber and the output side optical fiber according to claim 4 are fixed to a supporting member mounted on a substrate, respectively. 6. The support member according to claim 5, further comprising:
A wavelength tunable optical filter comprising a collimator lens fixed to each of a rear stage of an input optical fiber and a front stage of an output optical fiber.