JPH10177112A - Optical fiber with filter and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen light loss and to improve the long-term reliability at a low cost, by making the end face of a second optical fiber butt against the optical filter film of a first optical fiber so that the end faces thereof face each other and fusion spricing the butting part via an optical filter. SOLUTION: The end face of the second optical fiber 3 is butted against the optical filter film 1 of the first optical fiber 2 having the optical filter film 1 formed on the end face by vapor deposition in such a manner that the end faces face each other. The butting parts are fusion-spliced via the optical filter film 1. The fusion splicing is executed by aligning the axes of both optical fibers 2, 3 to each other and preheating the parts facing each other, then shaping and heating the optical fibers 2, 3 while pushing one of these fibers into the direction where the fibers are butted against each other. As a result, the optical filter film 1 and the end faces of the optical fibers 2, 3 are tightly adhered without clearances and, therefore, the light loss at the boundary decreases drastically. Since adhesives are not used, the high environmental reliability is obtd. when the optical fiber with the filter is used for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an optical fiber with a filter which is low in cost and excellent in environmental reliability and a method for producing the same.

[0002]

2. Description of the Related Art In general, in optical communication using an optical fiber, an optical filter is used to selectively transmit and prevent wavelengths, prevent reflection, and attenuate light. Such an optical fiber with an optical filter is configured by inserting a filter element formed by forming a film by vacuum evaporation or the like in the middle of the optical fiber, and there are a substrate fixed type and a ferrule insertion type.

[0003] An optical fiber fixed to a substrate is shown in FIG.
As shown in (a) and FIG. 13 (b), a plurality of optical fibers 41 are fixed on the substrate 40 along the longitudinal direction, and an element insertion groove 42 that cuts the optical fiber 41 and reaches the substrate 40 is formed. The filter element 43 is engraved in the center of the substrate in the horizontal direction, and the filter element 43 is inserted into the element insertion groove 42 and fixed with an adhesive 44. As shown in FIGS. 14 (a) and 14 (b), the ferrule insertion type optical fiber has an insertion hole 4 formed in the axis of the ferrule 46.
The optical fiber 41 is inserted through the ferrule 46.
The optical fiber 4 inserted through the side (upper side in the figure) of
The filter element 43 is inserted into the element insertion groove 42 so as to cut the element 1 and is fixed with an adhesive 44.

In each of the above-mentioned optical filter of the substrate fixed type and the ferrule insertion type, an element insertion groove 42 having a width slightly larger than the thickness of the filter element 43 is formed (that is, the optical fiber 41 is cut by a distance longer than the thickness of the filter element 43). Since the filter element 43 is inserted into the element insertion groove 42 and fixed by bonding, a gap is formed between the filter element 43 and the end face of the optical fiber 41, and the gap is filled with an adhesive 44. ing.

[0005]

However, the conventional substrate-fixed type and ferrule-inserted type optical fibers require material costs as much as the substrate 40, the ferrule 46, the adhesive 44, etc. are required.
There is a problem that the size is increased by the dimension of No. 6. Further, the groove processing on the substrate 40 and the ferrule 46, the filter element 4
3 requires operations such as insertion and bonding, and the number of manufacturing steps is large. Moreover, while the thickness of the filter element 43 is 10 to 30 μm, the width of the element insertion groove 42 is only the thickness of the filter element 43 plus 1 to 10 μm, and the work of inserting the filter element 43 into the element insertion groove 42 is extremely difficult. Difficult to do. For this reason, the productivity is extremely low and the production cost is high. Further, the optical fiber 41 is cut to a thickness equal to or greater than the thickness of the filter element 43, and a gap is formed between the filter surface of the filter element 43 and the end face of the optical fiber 41. Since this gap is filled with the adhesive 44, Interface of agent 44 and adhesive element 44 and filter element 4
There is also a problem that light is scattered and reflected at the interface of No. 3 and extra light loss occurs. Moreover, since the filter element 43 is fixed with the adhesive 44, there is a problem in the environmental reliability of the adhesive 44 when used for a long time.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical fiber with a filter, which has low optical loss, is low in cost, and has excellent long-term reliability, and a method for producing the same.

[0007]

In order to achieve the above object, an optical fiber with a filter according to the present invention comprises a second optical fiber having a second optical fiber and a first optical fiber having an optical filter film formed on an end face by vapor deposition. The gist is that the end faces are opposed to each other, and the abutting portion is fusion-spliced via the optical filter film.

In the method of manufacturing an optical fiber with a filter according to the present invention, a first optical fiber having an optical filter film formed on an end face by vapor deposition and a second optical fiber are prepared, and both optical fibers are used as an optical filter film of the first optical fiber. And the end face of the second optical fiber are disposed so as to face each other, and the facing portions of the two optical fibers are fusion-spliced via the optical filter film.

That is, in the optical fiber with a filter of the present invention, the first optical fiber having the optical filter film formed on the end surface by vapor deposition and the second optical fiber are butted, and the butted portion is fused through the optical filter film. It is connected. Therefore, unlike the conventional substrate-fixed and ferrule-inserted optical fibers, the substrate, ferrule, adhesive, and the like are not used, so that the material cost is reduced accordingly. In addition, there is no need for operations such as forming a groove in a substrate or a ferrule, or inserting or bonding a filter element, so that the number of manufacturing steps can be reduced, and productivity can be improved and cost can be further reduced. Furthermore, the size can be reduced because there is no substrate or ferrule and there is no extra filter element protruding from the optical fiber. Further, since the optical filter film and the end face of the optical fiber are in close contact with each other and no gap is formed, light loss at the interface is greatly reduced. Moreover, because no adhesive is used,
High environmental reliability when used for a long time.

In the optical fiber with a filter according to the present invention, a silicon oxide film is formed on the surface of the optical filter film of the first optical fiber.
When the optical fiber and the optical fiber are fusion-spliced, there is an advantage that the deformation at the time of fusion splicing prevents the optical filter film from being melted and the filter performance does not deteriorate. That is, when the butt portions of the first and second optical fibers are fusion-spliced, the optical filter film may be overheated and melted and deformed, and if connected as it is, the filter performance may be reduced or the filter may not function as a filter. is there. Thus, by performing the above, even if overheated, only the silicon oxide film is melted and deformed, and the optical filter film is not deformed, so that the filter performance does not decrease.

In the optical fiber with a filter according to the present invention, when the end face of the optical fiber is formed to be inclined with respect to the vertical plane of the optical fiber axis, the light reflected at the fusion splicing interface escapes to the outside, This has the effect of reducing noise to the light source due to reflected return light.

In the method of manufacturing an optical fiber with a filter according to the present invention, a first optical fiber having an optical filter film formed on an end face by vapor deposition and a second optical fiber are fusion-spliced via the optical filter film. For this reason, unlike the conventional substrate-fixed and ferrule-inserted optical fibers, the substrate, ferrule, adhesive and the like are not used, so that the material cost is reduced accordingly. In addition, there is no need to perform a groove process on a substrate or a ferrule, or insert or attach a filter element, so that the number of manufacturing steps can be reduced, and productivity can be improved and production cost can be further reduced. Furthermore, the size can be reduced because there is no substrate or ferrule and there is no extra filter element protruding from the optical fiber. In addition, since the optical filter film and the end face of the optical fiber are in close contact with each other and there is no gap, an optical fiber with significantly reduced light loss at the interface can be obtained. Moreover, since no adhesive is used, an optical fiber having high environmental reliability when used for a long time can be obtained.

In the method of manufacturing an optical fiber with a filter according to the present invention, an optical filter film is formed on an end face of the first optical fiber, and a silicon oxide film is formed on the surface of the optical filter film. In the case where the two optical fibers are fusion-spliced, there is an advantage that deformation due to melting of the optical filter film is prevented by heating during fusion splicing, and the filter performance is not reduced. That is, by heating at the time of fusion splicing the butt portions of the first and second optical fibers,
There is a problem that the optical filter film is overheated and melted and deformed, and if it is connected as it is, the filter performance is reduced or the filter does not function. Thus, by performing the above, even if overheated, only the silicon oxide film is melted and deformed, and the optical filter film is not deformed, so that the filter performance does not decrease.

In the method for manufacturing an optical fiber with a filter according to the present invention, the fusion splicing is provided so that the silicon oxide film of the first optical fiber and the end face of the second optical fiber face each other. After preheating, the pressing is performed by pressing at least one of the optical fibers in a direction in which the optical fibers are brought into contact with each other. In the case of, there is an advantage that the deformation of the optical filter film at the time of pushing after contacting both end surfaces is prevented, and the filter performance is not reduced. That is, there is a problem in that the optical filter film is deformed due to the stress caused by pushing when the facing portions of the first and second optical fibers are fusion-spliced, and the filter performance is reduced or the filter does not function. Therefore, by performing the above, only the silicon oxide film at the tip portion is deformed even if it is pushed, and the optical filter film is not deformed, so that the filter performance does not decrease.

[0015]

Next, embodiments of the present invention will be described in detail.

FIG. 1 shows an optical fiber with a filter according to an embodiment of the present invention. This is abutted against the optical filter film 1 of the first optical fiber 2 having the optical filter film 1 formed on the end surface by vapor deposition so that the end surface of the second optical fiber 3 faces the optical filter film 1. Is fusion-spliced.

The optical fiber to which the present invention is applied may be any of a quartz optical fiber and a plastic optical fiber. Further, structurally, a step index type (SI type) of a double structure in which a low-refractive-index clad is coated around a high-refractive-index core, or a grating in which the refractive index changes parabolically in the radial direction. Any of the index type (GI type) may be used. Further, a single-core optical fiber composed of one optical fiber or a multi-core optical fiber such as a tape-shaped optical fiber composed of a plurality of optical fibers may be used.

Materials for forming the quartz optical fiber and
For example, for example, Na_TwoO-CaO-SiO_TwoGlass,
Na_TwoOB_TwoO_Three-Al_TwoO_Three-SiO_TwoGlass, T
iO _Two-Na_TwoOB_TwoO_Three-SiO_TwoGlass, Na_Two
OB_TwoO_Three-SiO_TwoGlass, B_TwoO_Three-La_TwoO_Three
-RO glass, NaF-TiO_Two-SiO_TwoGlass, N
a_TwoO-CaO-SiO_Two・ Ce ・ Eu glass 、 Na_Two
OB_TwoO_Three-Al_TwoO_Three-SiO_Two・ AgCl ・ Br
・ I glass, TiO_Two(Na_TwoO) -Al_TwoO _Three-Si
O_TwoGlass, As-S-halogen glass, Ge-Se-
Te glass, GeO_Two-SiO_TwoGlass, B_TwoO_Three-S
iO_TwoThere are various materials such as glass, but there is no particular limitation
It is not something to be done. The quartz optical fiber
Related resin, silicone resin, nylon resin, ultraviolet light
A protective coating made of a resin material such as a cured resin is performed.

Examples of the material for forming the plastic optical fiber include polymethyl methacrylate (PMMA), polystyrene, polycarbonate, diethylene glycol bisallyl carbonate (CR-3).
9), acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), poly-4-methylpentene (TPX), and other various materials, but are not particularly limited. is not.

In the present invention, first, an optical filter film is formed on the end face of the first optical fiber by vapor deposition.

The first optical fiber 2 may be formed so that its end face 4 is perpendicular to the axis of the optical fiber, as shown in FIG. 2A, or as shown in FIG. Alternatively, it may be formed on an inclined surface at a predetermined angle α with respect to the vertical surface of the optical fiber axis. When the end face 4 is formed as a vertical face, the end face 4 can be easily polished or the like, which is advantageous in terms of cost. When the end face 4 is formed as an inclined surface,
There is an effect that the light reflected at the fusion splicing interface escapes to the outside, and noise to the light source due to the reflected return light is reduced.
Here, the inclination angle α of the inclined surface is not particularly limited and may be arbitrarily set, but is most preferably 5 to 8 °. When the end surface 4 of the first optical fiber 2 is formed as an inclined surface, the end surface of the second optical fiber that is fusion-spliced with the first optical fiber 2 is also formed on the inclined surface having the same inclination angle α as the first optical fiber 2. There is a need to.

As a vapor deposition method for forming an optical filter film, a so-called physical vapor deposition method (PVD method) such as a vacuum vapor deposition method, an ion-assisted vapor deposition method, a sputtering method, or an ion plating method is mainly performed. Chemical vapor deposition (CVD) such as plasma CVD is also performed.
There is no particular limitation. The vacuum evaporation method is a method in which a deposition material is heated and evaporated in a high vacuum, and the evaporated atoms are solidified on the end face of the optical fiber to form a film. In the sputtering method, an inert gas (argon or the like) of about 10 ^{-1 to} 10 Pa is flowed into a tank, a voltage of several thousand volts is applied between the electrodes to cause glow discharge, and an inert gas ion is applied negatively. In this method, the scattered target material is caused to collide with an end face of the optical fiber. In addition, the ion-assisted evaporation method is an evaporation method in which an ion gas from an ion source is projected onto a substrate surface while depositing a thin film forming substance. Further, the ion plating method is a method in which evaporated atoms heated and evaporated are ionized in an argon glow discharge and collide with a negatively applied optical fiber end face to be solidified. Among these, when forming a dielectric multilayer film in which metal oxides and the like are laminated in multiple layers as an optical filter film, an ion-assisted vapor deposition method is preferable from the viewpoint that an optical filter film with high density and good adhesion can be obtained. It is. When a metal film is formed, a vacuum evaporation method is preferable.

The substance deposited as an optical filter film by the above-mentioned deposition method includes, for example, TiO ₂ , ZnS, C
eO ₂ , Ta ₂ O ₅ , ZrO ₂ , SiO ₂ , MgF ₂ ,
CaF ₂ , BaF ₂ , LiF, NaF, MgO ₂ , Al
₂ O ₃ , Ti, Mo, Au, Cr, Zn, Al, Mg,
Examples include various substances such as Co, and are not particularly limited. These are formed as a single layer or as a multilayer in which a plurality of types are laminated.

These vapor deposition methods need to be performed without heating or at a low temperature in order not to damage the resin coating. Further, when vapor deposition is performed on a silica-based optical fiber having a protective coating, gas is released from the protective coating under a high vacuum, the degree of vacuum is reduced, and the characteristics of the optical filter film are deteriorated. One optical fiber is set on a jig for vapor deposition. That is, FIG.
As shown in the figure, the jig 7 comprises a case 5 and a lid 6 for sealing the case 5 via a sealing rubber 10a. The lid 6 is sealed around the end of the first optical fiber 2 with a sealing rubber 10b. There is provided a holding portion 11 for holding in a shape. As shown in FIG. 3 (b), the first optical fiber 2 is provided with a rubber seal 10b on the holding portion of the lid 6 so that the protective coating 9 near the end face is peeled off and the end face 4 of the first optical fiber 2 is exposed. Pinched through. In this state,
The first optical fiber 2 is sealed in a jig 7. As the rubber seals 10a and 10b, a fluorine-based rubber or the like which emits little gas is used. Then, the first optical fiber 2 is inserted into the vapor deposition device 8 with only the end face 4 exposed, and vapor deposition is performed. At this time, while the inside of the vapor deposition device 8 is at a high vacuum, the inside of the jig 7 is kept at the atmospheric pressure, so that the gas is not released from the protective coating 9 and the degree of vacuum in the vapor deposition device 8 does not decrease. In FIG. 3A, reference numeral 12 denotes a heater.

Further, as shown in FIG. 4, the protective coating of the quartz optical fiber is removed, and a predetermined length L (15 to 30 m
m), the bare optical fiber 13 may be inserted into the vapor deposition apparatus, and the optical filter film 1 may be formed by performing vapor deposition on one end face 4 thereof. Even in this case, gas is not released from the protective coating and the degree of vacuum in the vapor deposition apparatus does not decrease.

The two optical fibers are disposed so that the optical filter film of the first optical fiber and the end face of the second optical fiber face each other, and the facing portions of the two optical fibers are fusion-spliced. At this time, when the quartz optical fibers are fusion-spliced, the protective coating is peeled off near the end faces of both optical fibers.

In the fusion splicing, for example, first, the two optical fibers provided so that the optical filter film of the first optical fiber and the end face of the second optical fiber face each other, and the facing portions of the two optical fibers are aligned. After preheating, the shaping is performed by pressing and shaping at least one of the optical fibers in a direction in which the optical fibers abut.

In general, axis alignment is performed with reference to the outer diameters of the end faces of both optical fibers in the case of the GI type, and with the core in the case of the SI type. However, when the optical filter film is formed on the end face of the first optical fiber, the outer diameter accuracy of the portion of the optical filter film is lower than that of the optical fiber portion (accuracy is deteriorated by about ± 1 to 3 μm), or the core is confirmed. Therefore, there is a tendency that the alignment accuracy deteriorates and the connection loss increases. Therefore, as shown in FIG. 5, the centering position P serving as a reference at the time of axis alignment is set.
At a predetermined distance M (10 to 50 μm) from the optical filter film 1.
) Is set at a position deviated by (degree). As a result, it is possible to reduce the axial deviation and reduce the connection loss.

As the heat source for the preheating, various types such as a nichrome heater, a carbon dioxide gas laser, a YAG laser, a gas discharge, a heating flame such as an oxyhydrogen flame, etc. are used. Its melting point is 1
Gas discharge is mainly used because it is as high as 800 ° C. and a large amount of heat is required for melting.

As shown in FIG. 6, the preheating is performed in the first
The optical filter film 1 of the optical fiber 2 and the end face 4 of the second optical fiber 3 are disposed so as to face each other, and the facing surface portions of the optical fibers 2 and 3 are heated and melted. In FIG. 6, reference numeral 14 denotes an electrode for gas discharge. However, when the optical filter film 1 is formed on the end face of the first optical fiber 2, the edge portion of the optical filter film 1 is overheated at the time of the preheating, and may be melted and deformed as shown in FIG. is there. As described above, when the optical filter film 1 is connected while being deformed, the optical filter film 1 is connected.
There is a possibility that the filter performance of the filter may be reduced or the filter may not function. Then, as shown in FIG. 8, after the silicon oxide film 15 is formed on the surface of the optical filter film 1 by vapor deposition, the first optical fiber 2 and the second optical fiber 3 are fusion-spliced. By doing so, even if the edge of the first optical fiber 2 is overheated during preheating, only the silicon oxide film 15 is melted and deformed, and the optical filter film 1 is not deformed. Absent. Therefore, the filter performance does not decrease after fusion splicing. Here, the thickness of the silicon oxide film 15 is preferably about 1.5 to 5 μm. If the thickness is less than 1.5 μm, the effect of forming the silicon oxide film 15 is poor and the optical filter film 1 is likely to be melted and deformed. If the thickness exceeds 5 μm, the light loss may be rather increased.

As another method for preventing the optical filter film 1 from being melted and deformed, as shown in FIG. 9, the position of the electrode 14 is set at the center between the opposing optical fibers 2 and 3 (indicated by a chain line in the figure). ) To the second optical fiber 3 by a predetermined distance N (about 3 to 5 μm),
Prevention of overheating of the optical filter film 1 is also performed.

The first and second optical fibers whose portions facing each other are preheated are shaped and heated while being pushed in a direction in which at least one of the optical fibers abuts with each other, so that the first and second optical fibers are in a molten state or a semi-molten state. The tip surfaces come into contact, and after the contact, they are further pushed a predetermined distance to complete the fusion splicing. However, when the optical filter film is formed on the end face of the first optical fiber, when the distal end portions of both optical fibers come into contact with each other, they are pushed in.
There is a possibility that the optical filter film is deformed to deteriorate the filter performance or stop functioning as a filter. Therefore, a silicon oxide film 15 is formed on the surface of the optical filter film 1 of the first optical fiber 2 (see FIG. 8), and the optical fibers 2 and 3 after the surface of the silicon oxide film 15 and the end surface of the second optical fiber 3 are in contact with each other. Is set to be equal to or less than the thickness of the silicon oxide film 15. By doing so, the silicon oxide film 1
Since only 5 deforms and the optical filter film 1 does not deform,
The filter performance does not decrease.

As the first optical fiber, an optical fiber 13 cut out by a predetermined length L by removing the protective coating.
In the case where the optical filter film 1 is formed on one end face (see FIG. 4), first, as shown in FIG.
The two optical fibers 1 are arranged such that the optical filter film 1 of the optical fiber 13 and the end face 4 of the second optical fiber 3 face each other.
3 and 3 are arranged and fusion-spliced, and then the other end face of the optical fiber 13 is fusion-spliced with another optical fiber 16 to obtain one long optical fiber using the optical fiber 13 as a joint. Done. In FIG. 10, 9 is a protective coating.

In the case of a quartz optical fiber, the connection portion after fusion splicing is reinforced because the protective coating 9 is peeled off and removed. As a method of reinforcement, as shown in FIG. 11, a resin tube 18 made of ethylene vinyl alcohol or the like is put on the connection portion of the optical fibers 2 and 3 that have been fusion-spliced, and a steel core 17 is made to run along. The tube 18 is inserted into a heat-shrinkable tube 19 made of polyethylene or the like and heated.
Is fixed by heat shrinkage. As another method of reinforcement, as shown in FIG. 12, two metal plates 21 having grooves 20 are prepared, and a hot melt adhesive 22 is applied to both metal plates 21 to form the grooves 20. The optical fibers 2 and 3 are moved along, and the two metal plates 21 are aligned and bonded and fixed.

Next, an embodiment will be described.

[0036]

Embodiment 1 Quartz-based GI fiber (125 μm in diameter)
m, the angle of the end face was 0 °), the protective coating was removed, and a first optical fiber cut out to a length of 30 mm was prepared.
On one end face of the first optical fiber, a TiO ₂ layer and a SiO ₂ layer were alternately deposited in a thickness of 0.25 μm by ion-assisted deposition to form an optical filter film having a thickness of 10 μm. At this time, the degree of vacuum in the evaporation apparatus was 5 × 10 ⁻⁷ Torr. Further, a silicon oxide film having a thickness of 3 μm was formed on the surface of the optical filter film by vapor deposition.

Then, the first optical fiber and the second optical fiber were disposed such that the silicon oxide film of the first optical fiber and the end face of the second optical fiber faced, and were fusion-spliced under the following fusion conditions. Further, another end face of the first optical fiber and another optical fiber were fusion-spliced to obtain an optical fiber with an optical filter of the present invention. [Fusing conditions] Heating method: Gas discharge Distance between optical fibers: 10 μm Preheating time: 0.15 seconds Pushing amount: 2 μm Discharge time: 4.5 seconds

[0038]

Embodiment 2 A silica-based GI fiber (125 μm in diameter)
m) was used, and an optical fiber with an optical filter of the present invention was obtained in the same manner as in Example 1 except that the angle of the end face was changed to 8 °.

[0039]

[Embodiment 3] A quartz SI type fiber (125 μm in diameter)
Except for using m), an optical fiber with an optical filter of the present invention was obtained in the same manner as in Example 1.

[0040]

Embodiment 4 Quartz GI fiber (125 μm in diameter)
m, the angle of the end face was 0 °), the protective coating was removed, and a first optical fiber cut out to a length of 30 mm was prepared.
On one end face of the first optical fiber, a TiO ₂ layer and a SiO ₂ layer were alternately deposited in a thickness of 0.25 μm by ion-assisted deposition to form an optical filter film having a thickness of 10 μm.

Then, the first optical fiber and the second optical fiber were arranged such that the silicon oxide film of the first optical fiber and the end face of the second optical fiber faced, and were fusion-spliced under the following fusion conditions. Further, another end face of the first optical fiber and another optical fiber were fusion-spliced to obtain an optical fiber with an optical filter of the present invention. [Fusing conditions] Heating method: Gas discharge (electrode position shifted by 5 μm from the center between optical fibers to the second optical fiber side) Distance between optical fibers: 10 μm Preheating time: 0.1 second Depressed amount: 2 μm Discharge time: 1.5 seconds

[0042]

Embodiment 5 Quartz GI fiber (125 μm in diameter)
m, the angle of the end face is 0 °), and remove the coating near the end face.
The removed long first optical fiber was prepared. This first light
Set the fiber in the jig shown in Fig.
TiO by assisted deposition _TwoLayer and SiO_TwoEach layer
Alternately deposited and laminated at a thickness of 0.25 μm to a thickness of 10
A light filter film of μm was formed. Evaporation equipment at this time
The degree of vacuum inside is 1 × 10^-6Torr, using a jig
If not (1 × 10^-FourHigher vacuum than Torr)
Was done. Further, a thickness of 3 μm is applied to the surface of the optical filter film.
m silicon oxide film was formed by vapor deposition.

Then, the first optical fiber and the second optical fiber are disposed such that the silicon oxide film of the first optical fiber and the end face of the second optical fiber face each other, and are fusion-spliced in the same manner as in the first embodiment. An optical fiber with an optical filter was obtained.

[0044]

[Comparative Example] A Ti substrate having a thickness of 0.5 mm
An O ₂ layer and a SiO ₂ layer are alternately deposited with a thickness of 0.25 μm each to form a 10 μm thick filter element;
The glass substrate was polished to a thickness of 10 μm and thinned to form a filter chip having a total thickness of 20 μm.
The substrate-type optical fiber shown in FIG.

With respect to the optical fibers of Examples 1 to 5 and Comparative Example, the transmittance was measured by transmitting light of a predetermined wavelength, and the transmittance when the same light was transmitted only through the filter was measured. Was determined as the transmission loss. As a result, the optical fiber of the comparative example had a transmission loss of about 0.3 to 0.4 dB, whereas the optical fiber of each example was suppressed to about 0.10 to 0.15 dB, and the transmission loss was reduced to about half. Diminished.

[0046]

As described above, according to the present invention, unlike the conventional substrate fixed type and ferrule insertion type optical fibers, the substrate, ferrule, adhesive and the like are not used.
The material cost is reduced accordingly. In addition, there is no need for operations such as forming a groove in a substrate or a ferrule, or inserting or bonding a filter element, so that the number of manufacturing steps can be reduced, and productivity can be improved and cost can be further reduced. Furthermore, the size can be reduced because there is no substrate or ferrule and there is no extra filter element protruding from the optical fiber. Also, since the optical filter film and the optical fiber end face are in close contact with each other and there is no gap,
Light loss at the interface is greatly reduced. In addition, since no adhesive is used, environmental reliability when used for a long time is high.

[Brief description of the drawings]

FIG. 1 is a side view showing an optical fiber with a filter according to an embodiment of the present invention.

FIG. 2 is a side view showing a state of an end face of a first optical fiber, where (a) is a state formed on a plane perpendicular to an axis,
(B) is a state formed on an inclined surface with respect to a vertical surface of the axis.

3A is an explanatory view showing a vapor deposition apparatus using a jig, and FIG. 3B is an enlarged view of a main part showing a rubber seal portion of the jig.

FIG. 4 is a side view showing an optical fiber cut out by a predetermined length.

FIG. 5 is an explanatory diagram showing an alignment position of axis alignment.

FIG. 6 is an explanatory view showing a fusion splicing step.

FIG. 7 is a side view showing the first optical fiber whose tip is melted and deformed.

FIG. 8 is a side view showing a first optical fiber on which a silicon oxide film is formed.

FIG. 9 is an explanatory view showing a fusion splicing step.

FIG. 10 is an explanatory view showing another fusion splicing step.

FIG. 11 is an explanatory diagram showing a reinforced state of a connecting portion.

FIG. 12 is an explanatory diagram showing another reinforcing state of the connection portion.

13A and 13B are diagrams showing a conventional substrate-fixed optical fiber, wherein FIG. 13A is a perspective view and FIG. 13B is a sectional view of a main part.

14A and 14B are diagrams showing a conventional ferrule insertion type optical fiber, wherein FIG. 14A is a perspective view and FIG. 14B is a sectional view of a main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical filter film 2 1st optical fiber 3 2nd optical fiber

Claims (6)

[Claims] 1. An optical filter film of a first optical fiber having an optical filter film formed on an end face by vapor deposition,
An optical fiber with a filter, characterized in that the end faces of the optical fiber are butted to face each other, and this butted portion is fusion-spliced via the optical filter film. 2. The optical fiber with a filter according to claim 1, wherein a silicon oxide film is formed on a surface of the optical filter film of the first optical fiber, and the first optical fiber and the second optical fiber are fusion-spliced. 3. The optical fiber with a filter according to claim 1, wherein an end face of the optical fiber is formed to be inclined with respect to a plane perpendicular to the axis of the optical fiber. 4. A first optical fiber having an optical filter film formed on an end face by vapor deposition and a second optical fiber are prepared, and the optical fiber film of the first optical fiber faces the end face of the second optical fiber. A method for producing an optical fiber with a filter, comprising: disposing the optical fibers in such a manner as to be opposed to each other, and fusion-splicing the facing portions of the optical fibers through the optical filter film. 5. An optical filter film is formed on the end face of the first optical fiber, and a silicon oxide film is formed on the surface of the optical filter film. Then, the first optical fiber and the second optical fiber are fusion-spliced. A method for producing an optical fiber with a filter according to claim 4. 6. A fusion splicing device, wherein the silicon oxide film of the first optical fiber and the end face of the second optical fiber face each other, and at least one of the facing portions of the two optical fibers is preheated. 6. The optical fiber with a filter according to claim 5, wherein the optical fiber is pushed by pushing the optical fiber in a direction in which the optical fiber is brought into contact with each other, and the amount of pushing the optical fiber after the silicon oxide film comes into contact with the end face of the second optical fiber is not more than the thickness of the silicon oxide film. Recipe.