JPH0990247A - Narrow-band optical filter module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately set a transmission center wavelength in a narrow-band optical filter used for optical communication. SOLUTION: Lenses 2, 3 are provided in front of and behind a narrow-band optical filter 1 and moreover the filter 1 is arranged at the common focal position of both lenses. Then, the incident light beam from an optical fiber 4 is displaced by Δx to give an incident angle θ to the light beam transmitting through the narrow-band optical filter 1. Thus, the transmission center wavelength is accurately set by adjusting the incident angle θ, in its turn, the displacement amount Δx.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a narrow band optical filter module used for optical communication or the like, and more particularly to a narrow band optical filter module adapted to adjust an incident angle of light to the optical filter.

[0002]

2. Description of the Related Art In an optical fiber amplifier or an optical semiconductor amplifier device used for optical communication, only a desired signal light is extracted from an input signal to the optical amplifier, or excess light emitted from the optical amplifier itself is removed. For blocking, a module type narrow band optical filter is used.

An example of a conventional basic narrow band optical filter module is disclosed in Japanese Patent Application Laid-Open No. 4-345102, and its configuration is shown in FIG. In FIG. 4, the optical fibers 4 and 5 fixed on the filter assembly substrate 16 are traversed by the core portions of the optical fibers 4 and 5 (the middle portion of the input side 4 and the output side 5 is peeled off to form only the core portion). The narrow band optical filter module is composed of the groove 17 thus formed and the thin strip-shaped narrow band optical filter 1 arranged in the groove 17.

In this case, in order to set the transmission center wavelength of the narrow band optical filter 1, the incident angle dependency of the narrow band optical filter 1 is measured in advance, and the insertion angle θ 0 of the narrow band optical filter 1, that is, It is necessary to determine the angle of the groove 17 in advance. However, in this case, it is difficult to adjust the center wavelength of the transmission band required for the narrow band optical filter within ± 0.5 nm, for example.

As a method for solving this problem, there is a method as shown in FIG. The narrow band optical filter module of FIG. 3 has the same basic configuration as that shown in FIG. 4, and is provided with a rotation adjusting component 15 capable of adjusting the mounting angle of the narrow band optical filter 1.

In FIG. 3, 13 and 14 are fiber collimators for the optical fibers 4 and 5, 20 is a light beam, and 21 is a housing.

[0007]

In the configuration shown in FIG. 3, the incident angle of light to the narrow band optical filter 1 is fixed and cannot be finely adjusted.

Further, in the configuration shown in FIG. 4, since the fine adjustment mechanism is provided, it is possible to set the center wavelength of the transmission band required for the narrow band optical filter with high precision, but the narrow band optical filter 1 is rotated. Since the mechanism is provided, the number of parts is large, which is disadvantageous for the purpose of reducing the number of manufacturing steps and improving reliability, and is not suitable for downsizing.

An object of the present invention is to provide a compact, inexpensive and highly reliable narrow band optical filter module.

[0010]

A narrow band optical filter module according to the present invention is a narrow band optical filter module used for optical communication, and includes a first lens and a narrow band optical filter element on a common optical axis. , A second lens are arranged in this order, and the narrow-band optical filter element is arranged in the first
And a light incident unit that is disposed at a common focal point position of the second lens and that is configured to make a light beam incident on the first lens in parallel to the optical axis and displaced by a certain distance from the optical axis. 1 lens, the narrow-band optical filter element, and light derivation means for extracting the transmitted light that has passed through the second lens in parallel to the optical axis.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is as follows.
Lenses are provided before and after the narrow-band optical filter, the narrow-band optical filter is placed at the common focal point of both lenses, and the light flux is made incident by shifting it slightly parallel to the line passing through the center of the lens. The angle of incidence of light on the bandpass filter can be adjusted.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing the structure of an embodiment of a narrow band optical filter module according to the present invention, FIG. 2 is a sectional view showing the actual structure, and the same parts as those in FIGS. It is shown in.

In FIG. 1, the lens 2, the narrow band filter 1 and the lens 3 are arranged on the same optical axis in this order, and the lens 2 and the optical fiber 4 and the lens 3 and the optical fiber 5 are arranged.
The positional relationship in the optical axis direction is such that the incident light from the optical fiber 4 and the outgoing light to the optical fiber 5 become a parallel light beam. That is, the narrow band filter 1 is arranged at the common focus position of the lenses 2 and 3.

Further, the optical axes of the optical fiber 4 and the lens 2, and the optical fibers 5 and 3 are set to be deviated by Δx in parallel with the line connecting the centers of the lenses 2 and 3, respectively. The light emitted from the lens 2 becomes a light beam 20 having an angle of θ with respect to the optical axis, passes through the narrow band optical filter 1, becomes parallel to the incident optical axis to the lens 2 again by the lens 3, and the optical fiber 5 Combined with.

Since the narrow band optical filter 1 is installed substantially perpendicular to the incident and outgoing optical axes, the light beam 20 has an incident angle of θ with respect to the narrow band optical filter 1. Here, in order to set the pass characteristic of the optical filter to a desired value, the value of θ is finely adjusted. That is, the displacement Δx of the optical fibers 4 and 5 is adjusted while measuring the characteristic as the optical filter. It can be realized by

In the case where a dielectric multilayer film is used as the narrow band optical filter 1, the transmission wavelength adjustment range of the narrow band optical filter 1 needs to be about ± 2 nm in view of its manufacturing accuracy. The dependency of the filter characteristics of the dielectric multilayer film on the light incident angle is about 1 nm / degree. Further, if the focal lengths of the lenses 2 and 3 used are f, then θ = Δx /
Therefore, if a lens having a focal length of 2 mm is used, the displacement Δx for obtaining a transmission wavelength adjustment range of about ± 2 nm is about ± 70 μm.

As for the setting accuracy of the transmission wavelength, an accuracy of about 0.03 nm can be obtained by using a fine adjustment table which can obtain a normal adjusting accuracy of about 1 μm. Even in the method shown in FIG. 4 and the method of rotating the narrow band optical filter 1 shown in FIG. 3, the setting accuracy of the transmission wavelength is about 0.5 to 1 nm, so that the configuration according to the present invention has a significantly excellent setting accuracy. There is.

In FIG. 2, the narrow band optical filter 1 is fixed to a cylindrical filter unit 12 using low melting point glass solder. The lenses 2 and 3 are aspherical lenses with a support, and the outer diameter and the center of the lens are manufactured with an accuracy within several μm in order to secure the performance as a lens.

Between the supports 8 and 9, the aspherical lenses 2 and 3 with the support, and the filter unit 12 are V-shaped or square grooves and V-shaped or square protrusions (not shown) fitted therein. ), It is possible to displace with high accuracy only in the vertical direction of the cross section of FIG.

The filter unit 12 and the aspherical lenses with support 2 and 3 have the same outer diameter, and the centers of the filter unit 12 and the aspherical lenses with support 2 and 3 coincide with each other on the order of μm due to the above-mentioned grooves and protrusions. Can be made. After the centers are aligned with each other, a filter unit 12 is provided by means such as YAG laser beam welding.
And the aspherical lenses 2 and 3 with support are integrated.

The supports 8 and 9 and the optical fiber terminals 10 and 11 have been adjusted in advance in the optical axis direction and fixed by welding. This adjustment method is, for example, in FIG.
A master jig in a state where only the support 9 and the optical fiber terminal 11 are not provided is prepared so that the light emitted from the optical fiber terminal 10 side to the optical fiber terminal 11 side is optimally coupled. The optical fiber terminal 11 may be adjusted and welded and fixed.

The supports 8 and 9 are attached to the aspherical lenses 2 and 3 with supports by displacing the supports 8 and 9 in the vertical direction of the cross section of FIG. 2 by utilizing the above-mentioned groove and protrusion while measuring the optical filter characteristics. Fix by welding. These welds are shown as 22.

A non-reflection coating film is applied to the end faces of the optical fibers of the optical fiber terminals 10 and 11 to prevent reflection (return light) from the end faces. Edge reflection can also be prevented by polishing the end face obliquely instead of using the non-reflective coating film. Since the light obliquely enters the narrow-band optical filter 1, the reflected light travels in a direction different from the incident angle, so that no return light is generated.

Further, since the light transmitted through the narrow band optical filter 1 is a parallel beam, the characteristics originally possessed by the filter will not be impaired.

[0026]

As described above, the present invention has an effect that a transmission center wavelength of a narrow band optical filter can be accurately set, internal reflection is small, and an inexpensive narrow band optical filter module can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of an embodiment of the present invention.

FIG. 2 is a sectional view of an embodiment of the present invention.

FIG. 3 is a configuration explanatory view showing an example of a conventional narrow band optical filter module.

FIG. 4 is a structural explanatory view showing another example of a conventional narrow band optical filter module.

[Explanation of symbols]

 1 Narrow band optical filter 2,3 Lens 4,5 Optical fiber 8,9 Support 10,11 Optical fiber terminal 12 Filter unit 20 Optical beam 21 Filter lens assembly housing

Claims (4)

[Claims] 1. A narrow-band optical filter module used for optical communication, wherein a first lens, a narrow-band optical filter element, and a second lens are arranged in this order on a common optical axis, and the narrow-band optical filter module is provided. The bandpass optical filter element includes the first and second
First lens disposed on a common focal point position of the lens for making a light beam incident on the first lens parallel to the optical axis and displaced from the optical axis by a predetermined distance. A narrow-band optical filter module comprising: a narrow-band optical filter element; and a light derivation unit that extracts light transmitted through the second lens in parallel with the optical axis. 2. The narrow-band optical fiber module according to claim 1, wherein the light incidence means and the light derivation means have an optical fiber, and each end face of the optical fiber has a non-reflecting means. 3. The narrow band optical filter module according to claim 1, wherein a dielectric multilayer film is used as the narrow band optical filter element. 4. The narrow band optical filter module according to claim 2, wherein an anti-reflection coating film is applied as the anti-reflection means, or an end face is obliquely polished.