JPH11352332A - Wavelength characteristic selection type optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make acquirable the wavelength selection characteristics varying with the respective fibers of the coated optical fibers emerging from one unit by disposing respective filters in combination in such a manner as to cross waveguides and imparting the different filter characteristics thereto by these waveguides. SOLUTION: An optical fiber ribbon 3 is inserted in the state where the coatings of the portions existing on a substrate 1 are stripped from a plurality of the optical fibers, i.e., bare optical fibers, into the grooves of the substrate. The substrate is then provided with two slit working grooves 5, 5 in the central portion thereof while cutting in the direction crossing the optical fibers. The filter elements 6, 6 varying in the characteristics are inserted into these grooves 5, 5 so as to cross the respectively separate optical fiber 3 groups and are fixed with a resin. When, for example, the light of a wavelength λ1 is transmitted through these filter elements 6, 6, the wavelength λ2 among the wavelength components propagating in the optical fibers 3 is removed by the filter element 6 of the characteristic to reflect the light of the wavelength λ2 and the wavelength λ3 is removed by the filter element 6 of the characteristic to reflect the light of the wavelength λ3 , so that only the necessary wavelength component is propagated.

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 which is applied to the field of optical communication and the like and selects a wavelength of signal light.

[0002]

2. Description of the Related Art In a conventional optical filter, a substrate is formed using quartz glass, which is a material of an optical fiber, and a predetermined V-groove processing or other cutting processing is performed on the substrate to insert a plurality of optical fibers and a resin. It was manufactured by bonding, case storage, and resin sealing. Usually, one filter element is inserted for one filter, and only each of the optical multi-core ribbons has the same wavelength characteristic.

[0003]

Therefore, for example, when light having a wavelength of 1.65 μm is introduced and filtered in addition to the communication wavelengths of 1.31 μm and 1.55 μm, if it is desired to change the wavelength characteristics to be transmitted, all of them must be rebuilt. .

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the outline of the invention is to cut two or three grooves on a single substrate to obtain different characteristics. By changing the position of the filter element and inserting the filter element, different wavelength selection characteristics can be obtained for each wire of the optical fiber ribbon coming out of one unit.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing an optical filter according to the present invention will be described below with reference to FIG. First, as shown in (a),
A rectangular substrate 1 is prepared using a SiO ₂ —Al ₂ O ₃ ceramic substrate used in the present invention as a starting material.
Next, as shown in (b), a predetermined plurality of V grooves 2 are provided on the substrate 1 by a cutting tool. Next, as shown in (c), the optical fiber tape 3 is inserted into the groove of the substrate 1 with a plurality of optical fibers stripped of the coating on the substrate, that is, with bare optical fibers. Then, as shown in (d),
Two slit processing grooves 5 and 5 are provided while cutting in the center portion in the direction crossing the optical fiber. Next, as shown in (e), filter elements 6 and 6 having different characteristics are inserted into the grooves 5 and 5 so as to traverse different groups of optical fibers 3 and fixed with resin. Then, as shown in (e),
This is housed in a U-shaped case 8 and filled with a curable resin 9 such as an epoxy resin. A rubber boot 10 is provided at the end of the metal case in the mounting direction of the optical fiber tape 3 so as to be easily coupled with the resin.

FIG. 2 shows the structure of the optical filter of the present invention thus obtained. FIG. 2A is a partial cross-sectional plan view of an example of the structure of the optical filter of the present invention. (B) is a partial cross-sectional front view, and (c) is a cross-sectional view before being stored in a case. Now, referring to these drawings, the optical filter 11 includes the substrate 1, the optical fiber 3, the filter elements 6, 6, and the case 8. 7 is an adhesive.
The substrate 1 has a plurality of V-grooves 2 formed thereon in parallel, and an optical fiber 3 is fixed in each V-groove by an adhesive 4. A plurality of optical fibers 3 fixed on the substrate 1 in this manner are cut in a required number of batches at two places, and slit processing grooves 5 and 5 are formed. Filter elements 6 and 6, each having a dielectric multilayer film made of, for example, a polyimide film as a base material, are inserted into the slit processing grooves 5 and 5, respectively. A part of these filter elements 6 and 6 protrudes outward and is inserted into the slit processing grooves 5 and 5, and is fixed by an adhesive 7. Epoxy resin is preferably used for the adhesive 7. The substrate 1 thus configured is housed in a U-shaped case 8, filled with a curable resin 9 such as an epoxy resin, and sealed. Reference numeral 10 denotes a rubber boot for sealing and fixing the optical fiber tape 3 at both ends of a U-shaped metal case.

The optical filter 11 configured as described above is
For example when the filter element 6,6 transmitting light of wavelength lambda _1, the characteristic of the filter element 6 for reflecting the light of the wavelength lambda _2, by removing a wavelength component in the wavelength lambda ₂ that propagates through the optical fiber 3 must Only the wavelength components that are difficult to transmit can be transmitted. Similarly, in the wavelength lambda ₃ of the characteristics to reflect light filter element 6, can propagate only the wavelength components needed to remove the wavelength component in the wavelength lambda ₃ that propagates through the optical fiber 3.

The filter element will be described in more detail. The filter element is formed by forming a dielectric multilayer film formed by laminating a plurality of dielectric layers having different refractive indexes on a substrate. By changing, an optical filter having a desired wavelength characteristic can be configured. The dielectric multilayer film
A thin oxide film such as silica or titania is formed over several tens of layers, and the base is formed using a quartz glass plate or a polyimide film.

The operation of the filter of the present invention will be described below. The wavelength of light used in the following embodiment is as follows.
Three wavelengths of 1.31 μm, 1.55 μm, and 1.65 μm. Also,
Reference numerals 31, 32, 33, and 34 denote optical fibers, respectively.

Embodiment 1 FIG. 3B shows the characteristics of the filter element 6a.
This filter element blocks 1.55 μm and 1.65 μm,
It has the property of transmitting μm. FIG. 3C shows the characteristics of the filter element 6b.
It has the property of blocking 65 μm and transmitting 1.31 μm and 1.55 μm. FIG. 3D shows the result of combining the characteristics of the filter element 6a and the filter element 6b.
It shows the characteristic of blocking 65 μm and transmitting 1.31 μm. Therefore, in the configuration shown in FIG. 3A, when the filter elements 6a and 6b are combined in the arrangement shown in the figure, when only the filter element 6a operates (in the case of light incident from the optical fiber 31), In the wavelength characteristic shown in FIG.
55 μm to 1.60 μm can be cut off, but when only the filter element 6b operates (in the case of light incident from the optical fiber 34), the wavelength characteristic shown in FIG.
μm to 1.65 μm can be blocked. In the portion where the filter elements 6a and 6b are combined, the obtained characteristics are
1.55 μm to 1.65 μm can be blocked. That is, when the three wavelengths are incident from the optical fibers 32 and 33, 1.
Only light of 31 μm is emitted.

Embodiment 2 FIG. 4B shows the characteristics of the filter element 6a.
This filter element blocks 1.31μm, 1.55μm and 1.65μm
It has the property of transmitting μm. FIG. 4C shows the characteristics of the filter element 6b.
It has the property of blocking 65 μm and transmitting 1.31 μm and 1.55 μm. FIG. 4D shows the result of combining the characteristics of the filter element 6a and the filter element 6b.
It has the property of blocking μm and transmitting 1.55 μm. Therefore, the filter element 6 having the configuration shown in FIG.
When a and 6b are combined in the arrangement shown in FIG.
a is the wavelength characteristic shown in (b) of FIG.
In the case where the filter element 6b has a characteristic of 1.31 μm to 1.55 μm and a small loss in the wavelength characteristic shown in FIG. ), Ie 1.55μm
, The loss is small, and 1.31 μm and 1.65 μm provide a large loss. That is, when the three wavelengths are incident from the optical fibers 32 and 33, only light of 1.55 μm is emitted.

Embodiment 3 FIG. 5B shows the characteristics of the filter element 6a.
This filter element blocks 1.31μm, 1.55μm and 1.65μm
It has the property of transmitting μm. FIG. 5C shows the characteristics of the filter element 6b.
It has the property of blocking 55 μm and transmitting 1.31 μm and 1.65 μm. FIG. 5D shows the result of combining the characteristics of the filter element 6a and the filter element 6b.
μm is blocked and 1.65 μm is transmitted. Therefore, when the filter elements 6a and 6b are combined in the arrangement shown in FIG. 5A with the configuration shown in FIG. 5A, the filter element 6a has a wavelength characteristic of 1.55 μm to 1.65 μm as shown in FIG.
m, the filter element 6b has a large loss at 1.55 μm and 1.31 μm and 1.65 μm in the wavelength characteristic shown in FIG.
In the case where the loss is small at μm, the wavelength characteristic shown in FIG. 5D in the part where both are combined and filtered, that is, the loss is small at 1.65 μm, and 1.31 μm and 1.55 μm
Then, a large loss can be obtained. That is, when the three wavelengths are incident from the optical fibers 32 and 33, only light of 1.65 μm is emitted.

In this embodiment, an optical fiber is used as a waveguide, but the present invention can be applied to a silicon-deposited waveguide in which a core portion is embedded in a quartz clad.

[0014]

The above is an example in which two filter elements are used. However, the case where a plurality of filter elements are used, such as three or four, can be easily analogized. As can be seen from the above embodiments, the present invention was able to provide a filter having at least three types of characteristics by combining a plurality of filter elements. Thus, from 1.31 transmission, 1.55 blocking to 1.
If you want to change to something with 31 transmission, 1.55 blocking, 1.65 blocking, etc., you can easily achieve this simply by changing the line connection.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for manufacturing an optical filter of the present invention.

FIG. 2 shows an example of the structure of an optical filter according to the present invention;
(A) is a partial sectional plan view, (B) is a partial sectional front view,
(C) is a cross-sectional view before being stored in a case.

FIGS. 3A and 3B are explanatory diagrams showing the relationship between the optical fiber and the filter element according to the first embodiment. FIG. 3A is an explanatory view showing the state of attachment of the optical fiber and the filter element, and FIGS. Graph of filter characteristics.

FIGS. 4A and 4B are explanatory diagrams showing the relationship between the optical fiber and the filter element according to the second embodiment, wherein FIG. 4A is an explanatory view of the state of attachment of the optical fiber and the filter element, and FIGS. Graph of filter characteristics.

FIGS. 5A and 5B are explanatory diagrams showing the relationship between the optical fiber and the filter element according to the third embodiment, wherein FIG. 5A is an explanatory view of the state of attachment of the optical fiber and the filter element, and FIGS. Graph of filter characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 V groove 3 Optical fiber tape (including optical fiber) 4 Adhesive 5 Slit processing groove 6, 6a, 6b Filter element 7 Adhesive 8 Case 9 Resin 10 Rubber boot 11 Optical filter 31 Optical fiber 32 Optical fiber 33 Optical fiber 34 Optical Fiber

Claims (1)

[Claims] In an optical filter element in which a film-shaped optical filter is embedded on an optical waveguide substrate, a plurality of filters are disposed in combination so as to cross the waveguide of the waveguide substrate, and the optical waveguide is provided by the waveguide. A wavelength characteristic selection type optical filter characterized by having different filter characteristics.