JP2000227527A - Optical fiber type optical part and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber-type optical part which has a coating with decreased absorption of light and in which generation of multimode propagation is suppressed, and to provide the producing method. SOLUTION: A coating part 3 comprising a thermosetting silicone having high transmittance for UV rays is formed on the peripheral face of an optical fiber 10 consisting of a core 1 and a clad 2 to obtain a coated optical fiber 20. By this method, a pattern having changes in the refractive index can be efficiently produced by radiation of UV rays in the production process of the optical fiber-type optical parts. The refractive index of the coating 3 is usually lower than that of the clad 2, but by constituting the clad 2 of a first clad 2a and a second clad 2b having a higher refractive index than that of the first clad 2a, propagation of high-order modes produced can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber type optical component using an optical fiber whose refractive index is changed in a predetermined area by irradiating ultraviolet light or the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the development of optical fiber communication technology, the configuration of an optical communication system has been advanced, such as the complexity of a network and the multiplexing of signal wavelengths. With respect to the construction of this optical communication system, the importance of optical circuit components having various functions is increasing.

One of such optical circuit components is an optical fiber type optical component. For example, an optical fiber type diffraction grating (fiber grating) irradiates a core or a clad of an optical fiber with ultraviolet light to give a periodic refractive index change in the direction of the optical axis, thereby producing a Bragg diffraction grating or a chirped Bragg grating. A diffraction grating, a core-cladding mode conversion type diffraction grating, etc., which transmits or reflects the propagating light according to the wavelength of the propagating light, and includes an optical filter, an optical multiplexer / demultiplexer, and a dispersion compensator. And various other applications. In addition, various changes in refractive index
By giving the distribution, an optical fiber type optical component for performing mode field conversion and optical coupling can be formed.

[0004] Such an optical fiber type optical component is made of Si.
GeO ₂ (germanium oxide) as a photosensitive component in advance on the core or clad of an O ₂ (quartz glass) based optical fiber
Is generally produced by irradiating a light having a predetermined wavelength such as ultraviolet light and forming a refractive index change pattern corresponding to the light energy intensity distribution. The mechanism of the refractive index change is considered to be that a Ge defect is generated in the optical fiber by irradiating light of a predetermined wavelength, and the Ge defect causes a change in the refractive index.

[0005]

In the step of irradiating ultraviolet light, a method of irradiating with the optical fiber coating removed has conventionally been adopted. However, in this case, problems such as deterioration of the glass surface are caused. Is generated. In contrast, Japanese Patent Application Laid-Open
JP-A-113741 and JP-A-10-82919 describe a method of forming a refractive index change pattern by irradiation with ultraviolet light without removing a coating. When irradiating with ultraviolet light without removing the coating in this way, it is necessary to use a material that sufficiently transmits ultraviolet light (has a high transmittance to ultraviolet light) as a material of the coating. Examples of such materials include fatty poly (meth) acrylate, silsesquioxane, vinyl, and the like in Japanese Patent Application Laid-Open No. Hei 9-113741.
Ether or alkyl-substituted silicon is exemplified, and in JP-A-10-82919, a silicone resin or an epoxy resin is described.

[0006] Coating in the case of using the manufacturing method as described above, in the case of an optical fiber having a conventional structure, (1) at the same time as the above condition that the absorption coefficient for ultraviolet light of a predetermined wavelength to be irradiated is small. (2) It is necessary to have a condition that it has a higher refractive index than the cladding and can suppress the occurrence of multi-mode propagation. However, due to the relationship between light absorption and the complex refractive index, increasing the refractive index increases the absorption coefficient, and if the absorption is reduced by reducing the coating thickness, this reduces the optical fiber. There is a problem that the strength is deteriorated, and therefore, it has been difficult to satisfy the above two conditions depending on the conventional structure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an optical fiber type optical component in which the absorption of irradiated ultraviolet light by coating is reduced and the occurrence of multi-mode propagation is suppressed. And a method for producing the same.

[0008]

In order to achieve the above object, an optical fiber type optical component according to the present invention provides an ultraviolet light of a predetermined wavelength to at least one of a core region and a cladding region. An optical component including an optical fiber on which a refractive index change pattern is written by irradiating, wherein a clad portion of the optical fiber includes a first clad portion provided on an outer periphery of a core portion, and a first clad portion. And a second cladding portion having a refractive index higher than the first cladding portion, and a coating portion made of thermosetting silicone formed on the outer periphery of the optical fiber. It is characterized by being formed from an optical fiber.

Further, the coated portion of the coated optical fiber is characterized by being integrally formed including a portion corresponding to a predetermined region irradiated with ultraviolet light of a predetermined wavelength.

In the above-mentioned optical fiber type optical component, thermosetting silicone is used as a material of a coating portion formed on an outer periphery of an optical fiber comprising a core portion and a cladding portion. Many thermosetting silicones have a high transmittance to ultraviolet light.Therefore, by using thermosetting silicone for the coating portion, for example, the ultraviolet light can be removed without removing the coating portion corresponding to a predetermined region to be irradiated with ultraviolet light. It becomes possible to apply a manufacturing method for writing a refractive index change pattern by light irradiation. In this case, the covering portion is integrally formed including a portion corresponding to the predetermined region.

In this case, the refractive index of the coating portion made of the thermosetting silicone may be smaller than the refractive index of the cladding portion, which causes a problem of occurrence of multimode propagation in practical use. On the other hand, by making the clad part at least two layers having a first clad part and a second clad part, and making the refractive index of the second clad part larger than that of the first clad part. In addition, it is possible to suppress the occurrence of multi-mode propagation and improve the characteristics.

The refractive index of thermosetting silicone is:
It is not less than 1.39 and not more than 1.43.

As described above, due to the relationship between light absorption and complex refractive index, increasing the refractive index increases the absorption coefficient.
In the optical fiber type optical device according to the present invention, since the second clad portion is separately provided for suppressing the multi-mode propagation, the refractive index of the thermosetting silicone constituting the coating portion is limited to the above value. It can be a small value. At this time, since the light absorption coefficient of the thermosetting silicone is reduced, the writing of the refractive index change pattern by irradiation with ultraviolet light can be performed more favorably.

Further, the thermosetting silicone is characterized in that it is formed containing only a linear alkyl group.

In a thermosetting silicone, the refractive index is usually adjusted by the content of the phenyl group. However, by increasing the content of the phenyl group, the refractive index increases and the absorption of ultraviolet light also increases. Therefore, by using a thermosetting silicone containing only a straight-chain alkyl group such as a methyl group and substantially not containing a phenyl group, it is possible to obtain a coating portion in which ultraviolet light absorption is further reduced.

Further, the first clad portion is made of quartz glass to which a predetermined amount of fluorine is added, and the second clad portion is made of quartz glass to which a predetermined amount of hydroxyl group is added.

In this configuration, the second clad portion is
A hydroxyl group having an attenuating property with respect to light in a wavelength band used for optical communication is added, whereby the refractive index is made larger than that of the first clad portion to which fluorine is added, and the second clad portion is added. It is possible to further suppress the occurrence of multi-mode propagation by attenuating the light component that spreads out. The second cladding has no ultraviolet light absorption and photosensitivity.

Further, a method of manufacturing an optical fiber type optical component according to the present invention comprises a core portion and a clad portion having a first clad portion and a second clad portion having a higher refractive index than the first clad portion. A coated optical fiber in which a coating made of thermosetting silicone is formed on the outer periphery of an optical fiber having a photosensitive component on at least one of the portion and the cladding portion. By irradiating ultraviolet light of a predetermined wavelength from the side surface through the coating portion, a refractive index change pattern is written on at least one of the core portion and the cladding portion.

By using the coated optical fiber having the above-described configuration, it is possible to manufacture an optical fiber-type optical component having good characteristics as described above. Writing of the refractive index change pattern can be performed efficiently. In particular, by adopting a manufacturing method in which the covering portion is not removed, deterioration and the like of the glass surface of the optical fiber can be suppressed, and the manufacturing process can be simplified and the manufacturing cost can be reduced.

The predetermined wavelength is not less than 220 nm and not more than 350 nm.
nm or less.

The wavelength range of the ultraviolet light is 22 on the short wavelength side.
0 nm is limited by the absorption edge of the coating, while 350 nm on the longer wavelength side is limited by the photosensitivity in writing. Therefore, by limiting the ultraviolet light used to the above-mentioned wavelength range, a manufacturing method can be realized in which the ultraviolet light absorption by coating is reduced and the writing efficiency by ultraviolet light irradiation is improved.

The refractive index of the thermosetting silicone is:
It may be characterized by being not less than 1.39 and not more than 1.43.

Further, the thermosetting silicone may be characterized in that it is formed containing only a straight-chain alkyl group.

Further, the first clad portion may be made of quartz glass to which a predetermined amount of fluorine is added, and the second clad portion may be made of quartz glass to which a predetermined amount of hydroxyl group is added.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical fiber type optical component and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional ratios in the drawings do not always match those described.

FIG. 1 is a cross-sectional view of one embodiment of a coated optical fiber 20 used in an optical fiber type optical component according to the present invention, and a refractive index in a fiber radial direction (a direction indicated by a line L in the figure). It is a figure showing a profile. The coated optical fiber 20 includes a core portion 1 and a clad portion 2 constituting the optical fiber 10 and a coated portion 3 formed on the outer periphery of the optical fiber 10, and the clad portion 2 further includes a first clad portion 2a, And a second cladding portion 2b on the outside thereof.

The refractive index profile shown in FIG.
The horizontal axis of the figure corresponds to the central axis of the core 1 along the line L in the figure.
Corresponding to each position on the vertical section,
In order to clarify the correspondence with each part,
The corresponding parts are denoted by reference numerals. In addition, corresponding to each part
The value of the refractive index and relative refractive index difference is such that the core 1 has a refractive index n. ₁
And relative refractive index difference Δn₁, The first cladding portion 2a has a refractive index n
_2aAnd relative refractive index difference Δn_2a, The second cladding 2b has a refractive index
n_2bAnd relative refractive index difference Δn_2b, The coating portion 3 has a refractive index n _Threeas well as
Relative refractive index difference Δn_ThreeAnd Below, the relative refractive index difference is Si
O_Two(Quartz glass)
You.

In the present embodiment, the coated optical fiber 20 used for the optical fiber type optical component according to the present invention is as follows.
A first cladding portion 2a and a second cladding portion 2b in which the cladding portion 2 is formed such that its refractive index satisfies n _2b > n _2a
And has a two-layered structure. An optical fiber having such a refractive index distribution can be configured, for example, as follows. That is, the core 1 is made of SiO
₂ , a predetermined amount of GeO ₂ (germanium oxide) is added to increase the refractive index, for example, to form Δn ₁ = 0.4%, and the first cladding portion 2a is formed by adding a predetermined amount of F (fluorine) to SiO _2. The refractive index is reduced to form, for example, Δn _2a = −0.1%.

At this time, the first cladding portion 2a has an outer diameter of 80 mm.
The range is up to μm, and the region having a cladding diameter of 80 to 125 μm is the second cladding portion 2b having a larger refractive index than the first cladding portion 2a as described above. The second clad 2b is formed, for example, by adding OH (hydroxyl group) to 200 to 300.
For example, Δn _2b ≒ 0% in SiO ₂ containing about ppm. Further, a coating portion 3 made of thermosetting silicone is formed on the outer periphery of the cladding portion 2 to form a coated optical fiber 20.

The coated optical fiber 20 having the above configuration
Then, as shown in FIG. 2, writing of a refractive index change pattern by irradiation of ultraviolet rays is performed to manufacture an optical fiber type optical component. That is, by irradiating the coated optical fiber 20 in a state in which the coating portion 3 is not removed from a side surface of the coated optical fiber 20 from the light source 5 such as a laser through the mask 4 with ultraviolet light of a predetermined wavelength, At least one of the predetermined refractive index change patterns is written.

As the mask 4, for example, a mask corresponding to a refractive index change pattern to be formed and a writing method, such as a long-period fiber grating or a Bragg diffraction type fiber grating, is used. To manufacture. Examples of the writing method include a phase grating method, a holographic method, and an intensity modulation mask method. Further, of the core portion 1 and the clad portion 2, the portion where the refractive index change pattern is written needs to be formed to contain GeO ₂ which is a photosensitive component. In the above embodiment, the core portion 1 containing GeO ₂ is a target of writing the refractive index change pattern.

In the optical fiber type optical component and the method for manufacturing the same according to the present invention, the optical fiber 10 is irradiated with ultraviolet light of a predetermined wavelength without removing the coating 3 as described above.
Writing and forming of a refractive index change pattern on the substrate. In the case of using a manufacturing method that removes the coating when irradiating ultraviolet light, the surface of the optical fiber comes into direct contact with air, causing the glass surface to deteriorate, or the surface of the optical fiber to be damaged during manufacturing, resulting in a decrease in tensile strength. This causes a problem such as lowering. Further, there is a problem that the manufacturing process is complicated and the cost is increased by the coating removing process and the recoating process after the writing of the refractive index change pattern by the irradiation of ultraviolet light. On the contrary,
The optical fiber 10 can be passed through the coating 3 without removing the coating 3.
By irradiating the optical fiber with ultraviolet light, these problems can be solved, the characteristics of the obtained optical fiber type optical component can be improved, and the manufacturing cost can be reduced.

At this time, as a composition of a material such as a resin applied to the covering portion 3, it is necessary to use a material which sufficiently transmits ultraviolet light used. In the selection of the composition of this material, considering the known electronic spectrum of various chromophores in the material and the wavelength of ultraviolet light used, does not have absorption in the ultraviolet light region of a predetermined wavelength, or A material such as a resin having a composition having a sufficiently small absorption coefficient is selected. However, even when the light absorption coefficient is small, heat generation and deterioration due to light absorption and an increase in absorption due to light absorption may occur when the irradiation intensity is high. Therefore, sufficient consideration should be given to specific irradiation conditions in the manufacturing process. Resin and the like to be used.

At this time, when the optical fiber having the conventional structure is used, the material such as the resin forming the coating portion 3 is (1) from the manufacturing surface of the optical fiber type optical component, (1) the ultraviolet light of a predetermined wavelength to be irradiated. A condition that the light absorption coefficient is small (hereinafter referred to as condition (1)) is required.
From the performance point of view of the optical fiber type optical component, (2) a condition that the refractive index is larger than that of the clad and that the occurrence of multi-mode propagation can be suppressed (hereinafter referred to as condition (2)) is required. .

However, due to the relationship between light absorption and complex refractive index, increasing the refractive index increases the absorption coefficient, making it difficult to satisfy both of the above two conditions.
FIG. 3 shows different refractive indices (1.41, 1.42, 1.4).
8, 1.52, 1.55) shows the wavelength dependence in the ultraviolet region of the light absorption coefficient for five types of silicone resins. The horizontal axis indicates the wavelength of the ultraviolet light to be irradiated, and the wavelength 2
The range is from 00 to 360 nm. In order to satisfy both the above conditions (1) and (2), a material having a small absorption coefficient and a large refractive index is required.
As shown in each curve of FIG. 3 and its correlation, a material having a higher refractive index has a larger light absorption coefficient, and therefore cannot satisfy the two conditions at the same time. Further, for example, when the thickness of the coating is reduced to reduce the absorption, this causes a problem that the mechanical strength of the optical fiber is deteriorated.

FIGS. 4A and 4B show a refractive index profile of a coated optical fiber having a conventional configuration used for manufacturing an optical fiber type optical component. In the example shown in FIG. 4A, the coated optical fiber includes a core 1, a cladding 2, and a coating 3, and the coating 3 is separated from the cladding 2 in order to prevent multi-mode propagation. Is also configured to have a large refractive index. In this case, as described above, the light absorption of the coating portion 3 increases, and it is not possible to favorably form and manufacture an optical fiber type optical component such as an optical fiber type diffraction grating by irradiation with ultraviolet light.

Further, in the example shown in FIG.
Are composed of a first covering portion 3a and a second covering portion 3b. Among them, the first coating portion 3a is formed to have a larger refractive index than the cladding portion 2 in order to prevent the occurrence of multi-mode propagation, and the second coating portion 3b is configured to reduce light absorption. The refractive index is accordingly increased to the cladding 2
It is formed smaller than. In this case as well, although there is an improvement over the example shown in FIG. 4A, the problem of light absorption by the first covering portion 3a still exists.

The above problem will be described more specifically below. In the optical fiber type optical component according to the present invention, thermosetting silicone is used as the material of the coating portion 3 of the coated optical fiber 20. Such a silicone has a small transmission loss of ultraviolet light and is a material applied to an ordinary coated optical fiber, so that it is easily available and low in cost.

The thermosetting silicone is usually prepared by a hydrosilyl represented by the following reaction formula (a): Si—CH ＝ CH ₂ + H—Si— → Si—CH ₂ CH ₂ —Si (a) It is polymerized and cured by a chemical reaction. Among the resin materials that have been put into practical use, those having a low refractive index include, for example, XE14-062 manufactured by Toshiba Silicone Co., Ltd.
Dow-Silicone CY52-130, Shin-Etsu Silicone OF
180, OF101, OF111 and the like.

It is standard practice to adjust the refractive index of such a thermosetting silicone by the content of a phenyl group (benzene ring structure). FIG.
FIG. 2 shows the correlation between the content ratio of phenyl group to methyl group and the refractive index of silicone. FIG. 6 shows the correlation between the content ratio of the phenyl group to the methyl group and the light absorption coefficient for ultraviolet light having a wavelength of 260 nm.

As shown in FIG. 5, the refractive index of the obtained silicone can be increased by increasing the content ratio of the phenyl group in the silicone. On the other hand, the phenyl group has an absorption near a wavelength of 250 nm, and therefore, as shown in FIG. 6, the light absorption increases with an increase in the content ratio of the phenyl group. This is also shown in FIG. 3 described above.

Therefore, it is necessary to set the content of the phenyl group to be small in order to reduce the absorption of ultraviolet light and to manufacture a good optical component.
For example, it is preferable that the refractive index of the thermosetting silicone be 1.39 or more and 1.43 or less. At this time, as shown in FIG. 5, the content ratio of the phenyl group to the methyl group is about 0.1.
1 or less. Furthermore, by using a thermosetting silicone containing only a straight-chain alkyl group such as a methyl group under the condition that the phenyl group is not substantially contained, the coating portion 3 having particularly good ultraviolet light transmission characteristics can be formed. Can be formed. In order to further improve the ultraviolet light transmission characteristics, it is desirable to reduce the C = C bond shown in the reaction formula (a). For this purpose, the ... Si-CH = CH ₂ H
It is desirable to reduce the ratio of the amount to -Si ...

As described above, when the coating portion 3 is formed of the thermosetting silicone containing no phenyl group, the refractive index of the coating portion 3 is, as shown in the refractive index profile of FIG. It becomes a value smaller than. When such a coating 3 is applied to a conventional step index type optical fiber having a single clad structure as shown in FIG. 4 (c), the entire optical fiber has a structure capable of multi-mode propagation due to its refractive index profile. Propagation of a mode other than the fundamental mode occurs, coupling occurs between the fundamental mode and the higher-order mode, and the propagation characteristics change.

For example, in a region where the refractive index is changed, there is a problem in that the mode radiated to the clad changes in characteristics due to recombination with the core. Further, for example, when a fiber grating is written in a core portion, there is a problem that when the refractive index of the coating portion 3 is low, a loss occurs at a wavelength shorter than the cutoff wavelength due to coupling with a propagating higher mode. There is. In the case of a long-period fiber grating, a higher-order mode converted from a fundamental mode propagates through an optical fiber, and thus loss characteristics may change due to disturbance.

FIG. 7 shows that in the configuration shown in FIG. 4C, the refractive index of the cladding 2 is n ₂ , the refractive index of the coating 3 is n _3, and the refractive index difference n between the cladding 2 and the coating 3 is n. ₂ -n ₃ is 0.
An example of the transmission characteristics of light near the Bragg reflection wavelength when a Bragg-type fiber grating is manufactured using the optical fiber No. 05 will be described. The horizontal axis is the wavelength of light propagating in the optical fiber.

In the graph shown in FIG. 7, the peak of a loss having a large amount of ripple (hereinafter, referred to as a short wavelength loss) in a region of a wavelength shorter than the wavelength band of 1555 to 1556 nm which is the Bragg reflection wavelength (around a wavelength of 1552 nm). Has occurred. This is due to the occurrence of multi-mode propagation.

FIG. 8 shows a change in the short wavelength loss when the refractive index difference n ₂ −n ₃ (horizontal axis) is changed. From this graph, as the refractive index difference between the cladding part 2 and the coating part 3 increases, that is, as the refractive index of the coating part 3 becomes smaller than that of the cladding part 2, the influence of multi-mode propagation increases, and the short wavelength loss decreases. It can be seen that the performance has deteriorated due to the increase.

In order to solve such a problem, in the optical fiber type optical component according to the present invention, the clad portion 2 has a double clad structure including a first clad portion 2a and a second clad portion 2b, The refractive index n _{2b of 2b} is the first
It is larger configuration than the refractive index n _2a of the cladding portion 2a. That is, as described above, it is difficult to realize the condition (1) for the absorption coefficient from the manufacturing aspect and the condition (2) for the refractive index from the performance aspect only by the covering portion 3. On the other hand, in the optical fiber type optical component according to the present invention, the condition (1) is adjusted by the coating portion 3, while the condition (2) is adjusted to the second portion, which is the portion outside the cladding portion 2.
Adjustment by the cladding portion 2b realizes both conditions.

In such a configuration, since the refractive index of the second cladding portion 2b is larger than that of the first cladding portion 2a, the second cladding portion 2b functions as a filter for removing a higher-order mode propagating through the cladding portion 2. In addition, recombination of the radiation mode with the core unit 1 is suppressed. As a result, as shown in FIG. 8, the short wavelength loss and the increase in the short wavelength loss due to the increase in the refractive index difference n _2a −n ₃ are significantly reduced as compared with the case of the single clad structure.

Further, as in the above-described embodiment, the second cladding portion 2b has an OH having a large loss with respect to light in the communication wavelength band.
Is contained in a large amount, the radiation mode propagating in the cladding portion 2 is attenuated by the OH, and the influence of the radiation mode is further reduced. At this time, OH increases infrared absorption, but has no absorption in a region of ultraviolet light used for writing a refractive index change, and therefore does not impair transmission of ultraviolet light.

As an embodiment of the optical fiber type optical component having such a structure and a manufacturing method, OF111 manufactured by Shin-Etsu Silicone Co., Ltd. is used as the material of the coating portion 3, and the glass diameter (outer diameter of the second cladding portion 2 b) is 125 μm. An optical fiber type optical component was manufactured using a coated optical fiber drawn to a resin diameter (outer diameter of the coating portion 3) of 250 μm. The loss of this optical fiber is 0.20 dB / km at a wavelength of 1.55 μm.
And good transmission characteristics. This optical fiber is 25 ° C,
Sensitization treatment by hydrogen treatment under the condition of 20 MPa
I went for five days. As described above, by adding hydrogen to the optical fiber by the hydrogen pressurizing process, the amount of change in the refractive index due to the irradiation of the ultraviolet light can be increased, and the writing of the refractive index change pattern can be made more efficient.

Next, the irradiation light source 5 shown in FIG. 2 was a KrF excimer laser using ultraviolet light having a wavelength of 247 nm.
The optical fiber is irradiated with ultraviolet light for 15 minutes through the coating 3 at an irradiation density of 00 mJ / cm ² , and a Bragg-type fiber grating is applied to the core 1 to which GeO ₂ is added by a phase mask method over a length of 8 mm. Was formed. The light blocking amount of the Bragg-type fiber grating manufactured as described above was about 20 dB at the peak value.

Under the same conditions, 20 Bragg-type fiber gratings were manufactured.
It was in the range of 0 to 30 dB. When the tensile strength of these optical fibers was evaluated, the average breaking strength was 5.0 GPa, and the value before irradiation with ultraviolet light was 5.2 GPa.
The deterioration is slight, and good characteristics are obtained.

The wavelength of the ultraviolet light used for writing the refractive index change pattern is preferably 220 nm or more and 350 nm or less. This wavelength range is the short wavelength side 2
20 nm is limited by the absorption edge of the coating, while 350 nm on the longer wavelength side is limited by the photosensitivity in writing. Therefore, by using the ultraviolet light in the above-mentioned wavelength range, it is possible to provide a manufacturing method that realizes both the reduction of the ultraviolet light absorption by the coating and the efficiency of the writing by the irradiation of the ultraviolet light.

The optical fiber type optical component and the method of manufacturing the same according to the present invention are not limited to the above-described embodiment, and various modifications and changes can be made. For example, regarding the structure of the clad part, one or more clad parts are further added to the first clad part and the second clad part described above.
It is also possible to have a cladding structure having a weight or more.

In the above embodiment, the writing of the refractive index change pattern is performed only in the core portion.
Writing may be performed on the core and clad portions, or only on the clad portion. In either case, the refractive index change pattern to be written can be set variously according to the target optical component.

[0057]

The optical fiber type optical component according to the present invention is
As described in detail above, the following effects are obtained. That is, by using a thermosetting silicone having high transparency to ultraviolet light for the coating portion of the coated optical fiber, writing the refractive index change pattern on the optical fiber by irradiating the ultraviolet light without removing the coating portion. Can be. In particular, the thermosetting silicone preferably has a configuration substantially free of a phenyl group.

At this time, as the ultraviolet light absorption by the covering portion is reduced, the refractive index of the covering portion becomes small, and there is a problem that multi-mode propagation occurs. On the other hand, by forming the clad portion of the optical fiber by the first clad portion and the second clad portion and making the refractive index of the second clad portion on the outer peripheral side higher than the refractive index of the first clad portion, the multi-layer structure is improved. Mode propagation can be suppressed to prevent deterioration of characteristics of the optical fiber type optical component.

Further, in the method of manufacturing an optical fiber type optical component according to the present invention, the deterioration of the glass surface of the optical fiber is achieved by writing the refractive index change pattern by irradiating ultraviolet light without removing the coating. And the like can be suppressed to improve the production yield, and the production process can be simplified to reduce the production cost. At this time, by manufacturing using the coated optical fiber having the above-described configuration, it is possible to improve the efficiency of writing the refractive index change pattern and improve the characteristics of the obtained optical fiber type optical component.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure and a refractive index profile of a coated optical fiber used for an optical fiber type optical component according to the present invention.

FIG. 2 is a perspective view schematically showing a method for manufacturing an optical fiber type optical component according to the present invention.

FIG. 3 is a graph showing a wavelength dependence of a light absorption coefficient of a silicone resin in an ultraviolet region.

FIG. 4 is a diagram showing a refractive index profile of a conventional coated optical fiber or the like used for an optical fiber type optical component.

FIG. 5 is a graph showing a correlation between the refractive index of a thermosetting silicone and the content ratio of a phenyl group to a methyl group.

FIG. 6 is a graph showing a correlation between a light absorption coefficient of a thermosetting silicone at a wavelength of 260 nm and a content ratio of a phenyl group to a methyl group.

FIG. 7 is a graph showing light transmission characteristics of a Bragg fiber grating manufactured using a coated optical fiber having a single clad structure.

FIG. 8 is a graph for comparing short-wavelength loss due to a Bragg-type fiber grating manufactured using a coated optical fiber having a double clad structure according to the present invention with that of a single clad structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Optical fiber, 20 ... Coated optical fiber, 1 ... Core part, 2 ... Clad part, 2a ... First clad part, 2b ... Second clad part, 3 ... Coated part, 4 ... Mask, 5 ... Light source.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Seiichi Mobara 1st Tayacho, Sakae-ku, Yokohama City, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Katsuyuki Tsuneishi 1st Tayacho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industry Co., Ltd. Yokohama Works F-term (reference) 2H049 AA33 AA43 AA44 AA45 AA59 AA62 2H050 AB05X AB10Y AB14Y AC36 AC82 AC84 BB04Q BB35Q

Claims (10)

[Claims] 1. An optical component including an optical fiber in which a predetermined area of at least one of a core portion and a clad portion is irradiated with ultraviolet light having a predetermined wavelength to write a refractive index change pattern. A cladding portion of the optical fiber, a first cladding portion provided on an outer periphery of the core portion, and a second cladding portion provided on an outer periphery of the first cladding portion and having a refractive index larger than that of the first cladding portion. And an optical fiber-type optical component comprising: a coated optical fiber having a coating made of thermosetting silicone formed on the outer periphery of the optical fiber. 2. The coated optical fiber according to claim 1, wherein the coated portion of the coated optical fiber includes a portion corresponding to the predetermined region irradiated with the ultraviolet light of the predetermined wavelength. Optical fiber type optical parts. 3. The thermosetting silicone has a refractive index of:
3. The optical fiber-type optical component according to claim 2, wherein the ratio is from 1.39 to 1.43. 4. The optical fiber type optical component according to claim 2, wherein said thermosetting silicone is formed containing only a straight chain alkyl group. 5. The method according to claim 2, wherein the first clad portion is made of quartz glass to which a predetermined amount of fluorine is added, and the second clad portion is made of quartz glass to which a predetermined amount of hydroxyl group is added. The optical fiber type optical component according to the above. 6. A core part, a first clad part and the first clad part.
A cladding portion having a second cladding portion having a refractive index larger than that of the cladding portion, and a coating portion made of thermosetting silicone on an outer periphery of an optical fiber having a photosensitive component in at least one of the core portion and the cladding portion. By irradiating a predetermined region of the optical fiber with ultraviolet light having a predetermined wavelength from a side surface through the coating portion of the coated optical fiber, the core portion or the clad A method of manufacturing an optical fiber-type optical component, comprising writing a refractive index change pattern on at least one of the portions. 7. The predetermined wavelength is not less than 220 nm and not more than 350 nm.
7. The method for manufacturing an optical fiber-type optical component according to claim 6, wherein the diameter is not more than nm. 8. The refractive index of the thermosetting silicone is:
7. The method of manufacturing an optical fiber-type optical component according to claim 6, wherein the ratio is from 1.39 to 1.43. 9. The method of manufacturing an optical fiber type optical component according to claim 6, wherein said thermosetting silicone is formed containing only a linear alkyl group. 10. The method according to claim 6, wherein the first cladding portion is made of quartz glass to which a predetermined amount of fluorine is added, and the second cladding portion is made of quartz glass to which a predetermined amount of hydroxyl group is added. The manufacturing method of the optical fiber type optical component described in the above.