JP3389101B2 - Optical fiber connector and optical amplifier using the optical fiber connector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber connecting portion and an optical amplifier used for a fiber amplifier, a non-linear optical element or the like in the fields of optical communication and optical measurement, and particularly to connecting a silica fiber and a non-silica fiber. However, the present invention relates to an optical fiber connection section characterized in that the connection section has low loss and low reflection, and an optical amplifier using the optical fiber connection section.

[0002]

2. Description of the Related Art At present, several kinds of glass fibers are attracting attention as an amplification medium for optical fiber amplifiers. For example, Zr-based or In-based fluoride fibers doped with rare earth element praseodymium (element symbol: Pr) and chalcogenide-based glass fibers have been attracting attention as amplification media for highly efficient 1.3 μm band optical fiber amplifiers. (Reference "Y. Ohishi, et.al," Recent pro
g ress in 1.3-μm fiber amplifier
s ", in Proc. OFC'96, San
Jose, California, paper
TuG1, 1996 "). Further, as an amplification medium for a 1.5 μm band optical fiber amplifier having a wide band characteristic, a telluride glass fiber doped with erbium (elemental symbol: Er) is attracting attention (reference “Mori et al .: No. 5”).
7th Conference / Academic Lecture (1996), 9a-KF-
4. See). Furthermore, chalcogenide-based glass fibers and telluride glass fibers are attracting attention as highly efficient nonlinear fibers (see "Yube et al .:
"Nonlinear optical element of chalcogenide glass fiber",
NEW GLASS, vol. 11, No. 4,
pp. 31-37, 1996 "and the document" MELin.
e, "Oxide glasses forfast photonic switching: A co
mparative study ", J. Appl. Phys. vol.69, No.10, p
p.6876-6884, 1991 '').

By the way, in the Zr-based or In-based fluoride fiber, a high NA fiber having a relative refractive index difference Δn of 1% or more is used in order to construct a practical optical amplifier by adding Pr. When such a non-silica optical fiber is actually used for amplification or nonlinear optics, it must be connected to the silica fiber with low loss and low reflection.

However, the connection between the silica-based fiber and the non-silica-based fiber has problems to be studied as shown in the following (1) to (3). That is, (1) difference in softening temperature of both fibers (silica-based fiber to 1
The conventional fusion splicing cannot be applied due to 400 degree, non-silica type fiber <500 degree).

(2) The optical connector connection technology cannot be applied because there is no manufacturing technology for the optical connector suitable for the non-quartz fiber.

(3) Due to the above (1) and (2), the proven connection method cannot be applied for connecting silica-based fibers.

Therefore, there is a demand for a general-purpose connection technique for reliably connecting a non-silica fiber and a silica fiber with low loss and low reflection.

Here, an example of a conventional method of connecting a non-silica optical fiber and a silica fiber is shown in FIG.
A description will be given with reference to 0.

FIG. 30 is a schematic side view showing a connection between a non-quartz fiber and a quartz fiber, and FIG. 30 (a) shows a case where an optical adhesive is not present on the fiber connecting surface (referred to as a conventional example 1). (B) shows a case where an optical adhesive is present on the fiber connecting surface (referred to as Conventional Example 2). In the figure, reference numeral 1 is a non-silica fiber, 2 is a silica fiber, and 5 is an optical adhesive. As the optical adhesive, an epoxy or acrylic UV curable resin is usually applied.

However, in the structure shown in FIG. 30, since the non-silica type optical fiber and the silica type fiber have different core refractive indexes, there is residual reflection at the connecting interface, and the splicing is generally practical. Cannot be realized. As an exception, as will be described later, regarding the connection between the Zr-based fluoride fiber or the In-based fluoride fiber and the silica-based fiber, by adjusting the glass composition of the Zr-based fluoride fiber or the In-based fluoride fiber, The connection method shown in 30 may be applicable.

Next, the case where the above-mentioned residual reflection exists will be described with reference to FIG. In this figure, silica-based fibers 2-1 and 2 are provided on both ends of the non-silica-based fiber 1.
-2 are connected to each other without interposing an optical adhesive. In the figure, the arrow indicates the traveling direction of the light beam, and the folded portion of the arrow means reflection at the connection portion.

In FIG. 31, when residual reflection exists between the silica-based fibers 2-1 and 2-2 and the non-silica-based fiber 1, the output signal has a ghost (acts as noise) caused by the reflection at both connection portions. Occurs, which significantly deteriorates the signal quality. As a practical residual reflectance of the connection portion, 60 dB or more is required (in the case of an optical fiber amplifier) (reference “Takei et al.,“ Optical amplifier module ”,
Oki Electric Development, vol.64, No.1, pp.63-66, 1997 "). The core refractive index of the above-mentioned non-silica fiber is 1.48 to 1.55 of Zr system fluoride fiber (it changes with glass composition), 1.45 to 1.65 of In system fluoride fiber.
(Changes depending on the glass composition), chalcogenide glass fiber (glass composition As-S) to 2.4, and telluride glass fiber to 2.1. The core refractive index of the quartz fiber connected to it is ˜1.50.

Therefore, the Zr-based fluoride fiber, I
When an n-based fluoride fiber, a chalcogenide-based glass fiber, or a telluride glass fiber and a silica-based fiber are connected by the method of the above-mentioned conventional example 1 (method without interposing an adhesive), the residual reflection amount R (unit: dB,
Regarding the relationship with the residual reflectance, the residual reflectance shows a negative value, whereas the return loss shows the absolute value of the residual reflectance and has a positive value) is calculated by the following equation (1). .

[0014]

[Equation 5]

However, n _NS and n _N are core refractive indexes of the silica-based fiber and the non-silica-based fiber, respectively.

Zr-based fluoride fiber, In-based fluoride fiber, chalcogenide-based glass fiber (glass composition As-S), or telluride glass fiber;
The amount of residual reflection between the silica fiber and the silica fiber is ∞ to 35, respectively.
dB, ∞ to 26 dB, 13 dB, or 16 dB. Regarding the Zr-based fluoride fiber and the In-based fluoride fiber, the reflection attenuation amount can be increased (the residual reflectance can be reduced) by adjusting the composition of the glass.

Therefore, so far, regarding the connection between the Zr type fluoride fiber or the In type fluoride fiber and the silica type fiber, the glass composition of the Zr type fluoride fiber or the In type fluoride fiber is the silica type fiber. The method of the above-mentioned conventional example 2 (method of interposing an adhesive) was mainly applied by precisely controlling so as to agree with. Although the method of Conventional Example 1 may be used in some cases, in this method, when the non-silica fiber 1 and the silica fiber 2 are connected to each other, an air layer (a core portion between the two fibers due to polishing roughness etc.) is formed at the connection interface. It occurs due to not completely adhering). Therefore, due to the presence of this air layer, low reflection cannot be realized with high yield, and the method of Conventional Example 1 is rarely applied.

The method of Conventional Example 2 (method of interposing an adhesive) will be further described with reference to FIGS. 32 and 33. 32 is a perspective view showing a state before connection, and FIG. 33 is a side view showing a state after connection. In this example, the core refractive index of the non-silica fiber and the core refractive index of the silica fiber are adjusted to be equal. Further, both fiber end surfaces are processed so as to be surfaces perpendicular to the central axis of the fiber.

In FIG. 32, reference numeral 8-1 is an optical fiber holding housing for holding the non-quartz fiber 1. This optical fiber holding housing 8-1 has a U-shaped cross section, and the V-groove substrate 9-1 is provided inside with the adhesive 10
-1 is provided on the inner bottom surface of the holding housing 8-1. This V-groove substrate 9-1 has a V-shaped groove (V groove) formed on its surface. Therefore, by providing the non-quartz fiber 1 along the V-groove substrate 9-1, the optical fiber 1 is positioned in the optical fiber holding casing 8-1. Further, the optical fiber fixing plate 11-1 is placed on the non-quartz fiber 1 provided on the V-groove substrate 9-1 to fix the non-quartz optical fiber 1. In this example, as shown in the figure, the optical fiber fixing plate 11-1 and the V-groove substrate 9-1 are used.
The adhesive 10-1 is interposed between the adhesive 10-1 and the adhesive. Similarly, the silica fiber 2 is also held by the optical fiber holding case 8-2. That is, the quartz optical fiber 2 is connected to the V-groove substrate 9-2.
Positioned by the adhesive 102 and the optical fiber fixing plate 1
It is fixed to the optical fiber holding housing 8-2 by 1-2.

As shown in FIG. 33, the silica-based fiber 2 and the non-silica-based fiber 1 are connected to each other so that their optical axes coincide with each other (the optical axes of both are aligned). After adjusting the positions of the bodies 8-1 and 8-2, the optical adhesive 5 is used for connection. In addition, as the optical adhesive 5,
Usually excellent in adhesive strength and 1.3 or 1.5 μm
An epoxy-based or acrylic UV-curable resin, which is excellent in transmission of the band signal light, is applied.

However, the method of Conventional Example 2 shown in FIG. 33 has some problems to be solved in order to realize a connection portion having excellent characteristics with good reproducibility and high yield. For example, the refractive index of the optical adhesive 5 needs to be exactly matched with the core refractive index of the non-silica fiber 1 and the silica fiber 2. In addition, when the refractive index and temperature change of the optical adhesive 5
Since there is a difference between the core refractive index / temperature change of the non-silica fiber 1 and the core refractive index / temperature change of the silica fiber 2, the residual reflectance may increase depending on the environmental temperature used for this connection.

As a method for solving such a problem, a method shown in FIG. 34 is disclosed in Japanese Patent Application No. 5-165379 (hereinafter referred to as the method of Conventional Example 3). FIG. 34 is a side view for explaining a method of connecting a silica fiber and a non-silica fiber. In the method shown in this figure, as in the method of Conventional Example 2, a Zr-based fluoride fiber or an In-based fluoride fiber is used as the non-silica fiber, and the core refractive index of the fiber matches the core refractive index of the silica fiber. Thus, the core glass composition can be precisely controlled. As shown in FIG. 34, in this method, the optical fiber holding housings 8-1 and 8-2 holding the fibers 1 and 2 are provided.
Each of the connection end faces of is formed so as to be inclined by θ with respect to the vertical axis of the optical axis of the fiber. Next, the optical fiber holding casing 8- is so arranged that the optical axes of the fibers 1 and 2 are aligned with each other.
After the positions of 1 and 8-2 are adjusted, they are obliquely connected using the optical adhesive 5 to realize a connection portion having low reflection and low loss. According to this method, it is not necessary to exactly match the refractive index of the optical adhesive 5 with the core refractive index of the non-silica fiber 1 and the silica fiber 2 as in the case of the method of the second conventional example. It is possible to suppress the occurrence of residual reflection due to the difference between the refractive index / temperature change of the adhesive 5, the core refractive index / temperature change of the non-silica fiber 1 and the core refractive index / temperature change of the silica fiber 2. It is possible to realize the connection part with good reproducibility and high yield.

However, in the methods of Conventional Examples 2 and 3 described above, the core-glass composition of the Zr-based fluoride fiber or the In-based fluoride fiber is controlled to control the core refractive index of the fiber and the core of the silica-based fiber. It is a connection technology that must match the refractive index. Therefore,
The methods of Conventional Examples 2 and 3 are general-purpose methods for connecting a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, or a telluride glass fiber having an arbitrary core refractive index to a silica-based fiber. It is not a technology applicable to connection.

By the way, the inventors of the present invention have a general application for connecting Zr-based fluoride fibers, In-based fluoride fibers, chalcogenide-based glass fibers, or telluride glass fibers and quartz-based fibers having arbitrary core refractive indexes. Techniques that can be achieved are disclosed in Japanese Patent Application No. 4-178650 (hereinafter referred to as Conventional Example 4) and Japanese Patent Application No. 9-30122 (hereinafter referred to as Conventional Example 5).

FIGS. 35 and 36 are for explaining the method of Conventional Example 4, FIG. 35 is a perspective view showing a state before connection, and FIG. 36 is a side view showing a state after connection.

In the method shown in FIGS. 35 and 36, first, the non-silica fiber 1 or the silica fiber 2 is used.
Is held by the optical fiber holding housing 8-1 or 8-2 (each optical fiber 1 or 2 is connected to the V-groove substrate 9-1,
9-2 is positioned and adhesives 10-1, 10-
2 and the optical fiber fixing plates 11-1 and 11-2 to fix the optical fiber holding housing 8-1 or 8-2). Also,
One optical fiber holding housing holding the fiber (see FIG. 35).
Then, an optical fiber holding housing 18 holding the fiber 2
A dielectric film 22 is provided on the connection end face of 2).
As shown in FIG. 36, the silica-based fiber 2 and the non-silica-based fiber 1 are connected to each other so that their optical axes coincide with each other (the optical axes of both are aligned).
After adjusting 1 and 8-2, they are connected by using an optical adhesive (an epoxy-based or acrylic-based ultraviolet-curing resin is generally used) 5 as shown in FIG. The connection end faces of the housings 8-1 and 8-2 are respectively made of the non-silica fiber 1 or the silica fiber 2.
Is perpendicular to the optical axis).

By the way, in the connection based on the method of the conventional example 4 shown in FIGS. 35 and 36, it is necessary to precisely adjust the refractive index of the optical adhesive 5 and the refractive index and the film thickness of the dielectric film 22. That is, assuming that the core refractive index of the non-silica fiber 1 is n ₁ and the core refractive index of the silica fiber 2 is n ₂ , the refractive index of the optical adhesive 5 is adjusted to n ₁ , and the dielectric film 22 has The refractive index n _f and the film thickness t _f need to satisfy the condition of the following expression (2).

[0028]

[Equation 6]

However, λ is the signal wavelength (wavelength used).

However, in the method of Conventional Example 4, since the dielectric film is used to form the low reflection / low loss connection portion, the refractive index of the optical adhesive 5 and the refractive index and the film thickness of the dielectric film 22 are changed. Needs precise adjustment. This is one of the problems to be solved in order to realize a connection part having excellent characteristics with good reproducibility and a high yield as in the method of the second conventional example.

On the other hand, in the method of Conventional Example 5, the connection end faces of the non-silica fiber and the silica fiber are not made vertical but are made to be inclined with respect to each other. That is, the inclination angle θ ₁ [unit is ra
d] and the inclination angle θ ₂ [rad] of the connecting end face of the silica-based optical fiber with respect to the vertical axis, the relationship between the core refractive index of the non-silica-based optical fiber is n ₁ and the core refractive index of the silica-based optical fiber is n. _{When set to 2} , the connection is made so as to satisfy the “Snell's formula” shown in the following formula (3). That is, the gist of the conventional example 5 proposed by the present inventors is that in connecting cores having different refractive indexes, the connection boundary surface is inclined to prevent reflection,
In addition, the optical axis of the fiber to be connected is tilted so as to satisfy the "Snell's formula" for low loss.

[0032]

[Equation 2]

However, when connecting the non-silica fiber and the silica fiber in which the core / glass compositions of the Zr-based fluoride fiber and the In-based fluoride fiber are precisely controlled so as to match the silica-based fiber, n ₁ and n are connected. ₂ are equal, and therefore correspond to Conventional Example 1 (θ ₁ = θ ₂ = 0) in FIG. 30 and Conventional Example 3 (θ ₁ = θ ₂ ≠ 0) in FIG. θ ₁ and θ ₂ are the same angle.

FIG. 37 is a side view for explaining the method of Conventional Example 5. In the figure, reference numeral 1 is a non-silica optical fiber, 2 is a silica fiber, and 3-1 and 3-2 are optical fiber holding casings for holding the ends of the non-silica optical fiber 1 or the silica optical fiber 2, respectively. Body, 4-1 and 4-2 are connection end faces of the optical fiber holding casings 3-1 and 3-2, and 5 is an optical adhesive. As shown in the figure, the non-silica optical fiber 1 and the silica optical fiber ₂ have optical fiber holding casings at different angles θ ₁ and θ ₂ with respect to the vertical axes of the respective connection end faces 4-1 and 4-2. It is held in 3-1 and 3-2. As mentioned above,
A low-loss connection between the non-silica optical fiber 1 and the silica fiber 2 can be realized when the angles θ ₁ and θ ₂ [rad] satisfy the Fresnel's formula shown in Expression 3.
Further, the return loss R ₁ and R _{2 at} the connecting portion between the non-silica optical fiber 1 and the silica fiber 2 are calculated by the following equation (4-
1) and (4-2) (This formula is described in the document “HMPresby, et.al,“ Bevelled-microlensed taper c
on nectors for laser and fiber back-reflection ", E
lectron. Lett., vol.24, pp. 1162-1163, 1988 ”).

[0035]

[Equation 8]

In the formula, n _UV is the refractive index of the optical adhesive 5, λ is the signal wavelength (used wavelength), and ω ₁ and ω ₂ are the mode field radii of the non-silica optical fiber 1 and the silica fiber 2. . Therefore, by adjusting the angles θ ₁ and θ ₂ from the above equation, it is possible to realize a low reflection connection with a desired reflection attenuation amount or more. For example, non-silica optical fiber 1 (Zr-based fluoride fiber: core refractive index 1.55, In-based fluoride fiber: core refractive index 1.65, chalcogenide-based glass fiber (glass composition As-S): core refractive index 2.4, telluride glass fiber: calculated with a core refractive index of 2.1), with respect to the angle θ ₁ and the silica-based optical fiber 2 required to realize return loss R ₁ = 40, 50, 60 dB. Then, the angles θ ₁ and θ ₂ required to realize the return loss R ₂ = 40, 50, 60 dB are expressed by the following formula (5) obtained by modifying the formulas (4-1) and (4-2). Can be found at.

[0037]

[Equation 9]

In the formula, n _UV is the refractive index of the optical adhesive 5, λ is the signal wavelength, n _1,2 is the core refractive index (the core refractive index n ₁ of the non-silica fiber ₁ or the core refractive index of the silica fiber 2). Rate n
₂ ) and ω _1,2 represent the spot size (radius) (the spot size (radius) ω _{1 of the} non-silica optical fiber 1 or the spot size (radius) ω 2 of the silica fiber ₂ ).

The refractive index n _UV 1.5 optical adhesive 5, the signal wavelength 1.3μm and lambda, non silica-based optical fiber 1 spot size (radius) omega ₁ and the spot size of the silica fiber 2 (radius) Both ω ₂ are 5 μm (that is, ω _1,2 = 5 μm
m), the return loss is 60d with low loss between the telluride glass fiber and the silica fiber, for example.
The connection of B is such that θ ₁ is 3.6 (deg) and θ ₂ is 5.0.
It can be realized by setting (deg) (the angle of θ ₂ is derived from Expression 3). However, in reality, the connection surface 4-1 shown in FIG.
In order to realize the above, processing roughness such as polishing that is generally used occurs, and therefore the actually obtained return loss is smaller than the calculated value. Therefore, a practically low reflection (reflection attenuation 6
0 dB or more), the connection angle θ ₁ of the non-silica fiber is, for example, a practically low reflection (reflection attenuation of 60 dB or more) when the decrease of the reflection attenuation is expected.
As the value required to achieve, for Telluride based fiber angle theta ₁ is 8 degrees or more, when the chalcogenide fiber angle theta ₁ is 8 degrees or more, if the angle theta ₁ of Zr-based fluoride fiber is 3 degrees Further, in the case of In-based fluoride fiber, it is desirable that the angle θ ₁ be 4 degrees or more. Therefore, according to the connection method of Conventional Example 5, a non-silica fiber (Zr-based fluoride fiber, In-based fluoride fiber, chalcogenide-based glass fiber, or telluride glass fiber) having an arbitrary core refractive index and a silica-based fiber are used. The connection between them can be realized universally.

By the way, as a result of the inventors' earnest study on the method of Conventional Example 5, the connection part to which Conventional Example 5 was applied had no problem in applying the non-silica fiber to the nonlinear element.

However, when it is applied to a connecting portion for an optical amplifier, it has become clear that the optical adhesive 5 may deteriorate and the connecting portion may be damaged. As a cause of this, when excitation light is incident on Pr-doped Zr-based or In-based fluoride fiber, Er-doped telluride fiber, Pr-doped chalcogenide fiber, visible light and ultraviolet light are generated in the Pr-doped fiber or Er-doped fiber, It is considered that the visible light and the ultraviolet light discolor the epoxy-based or acrylic-based optical adhesive 5 to become a light absorbing medium, which absorbs the excitation light and generates heat to destroy the connection portion. Such a problem similarly occurs in the methods of Conventional Examples 2, 3, and 4 in which the epoxy-based or acrylic-based optical adhesive 5 is used at the connecting interface between the silica-based fiber and the non-silica-based fiber. Even in the connection between the optical fiber and the optical waveguide, an epoxy or acrylic optical adhesive is used at the connection interface. However, in such connection, Pr or Er is used as the connecting fiber.
Since no non-quartz fiber added with is used, visible light and ultraviolet light that deteriorates the optical adhesive are not generated. Therefore, the optical fiber and the optical connecting portion are not damaged. That is, the problem that the connection part is damaged due to the deterioration of the optical adhesive is peculiar to the case where an optical amplifier is constructed by using a non-quartz fiber, and has been a problem that has not been heretofore known. Therefore, one of the problems to be solved by the present invention is a connection portion between a silica-based fiber and a non-silica-based fiber due to deterioration of an optical adhesive, which is peculiar to configuring an optical amplifier using the non-silica-based fiber. Is to prevent deterioration.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above problems.
It is an object of the present invention to provide an optical fiber connection part that connects a non-silica optical fiber and a silica fiber with low loss and low reflection without causing damage, and an optical amplifier using the optical fiber connection part.

[0043]

In order to solve the above-mentioned problems, the invention according to claim 1 is an optical fiber splicing part, at least one of which is a non-quartz fiber for optical amplification. An optical fiber and a second optical fiber, a first optical fiber holding housing holding the end of the first optical fiber, and a second optical fiber holding holding the end of the second optical fiber. A housing, the first optical fiber and the second optical fiber have different glass compositions, and the end surface of the first optical fiber holding housing and the first optical fiber
The end surface of the optical fiber, the end surface of the second optical fiber holding housing and the end surface of the second optical fiber are on the same plane, and the optical axis of the first optical fiber and the The second optical fiber is arranged so as to be aligned with the optical axis of the second optical fiber, and is arranged in a partial region of at least one end face of the first optical fiber holding casing and the second optical fiber holding casing. Is provided with a groove portion located in the vicinity of the end portion of the first or second optical fiber, and the end surfaces of the first and second optical fiber holding casings are formed by the groove portion.
It is divided into a first region on the side of the first and second optical fibers and a second region outside the first region, and only in the second region of the first and second regions. An adhesive layer made of an adhesive is provided, and the first optical fiber holding casing and the second optical fiber holding casing are adhered by the adhesive layer, and the end face of the first optical fiber and the first optical fiber holding casing are adhered to each other. It is characterized in that the end faces of the two optical fibers are connected.

The invention described in claim 2 is the same as claim 1
In the optical fiber splicing part described in [1], the adhesive is an epoxy-based or acrylic-based adhesive.

The invention described in claim 3 is the same as that of claim 2
In the optical fiber connection part described in [1], the adhesive is an ultraviolet curable adhesive.

Further, the invention according to claim 4 is an optical fiber connecting portion, at least one of which is a first optical fiber and a second optical fiber, and at least one of which is a non-quartz fiber for optical amplification; A first optical fiber holding housing for holding an end portion of one optical fiber; and a second optical fiber holding housing for holding an end portion of the second optical fiber,
Of the optical fiber and the second optical fiber have different glass compositions, and the end face of the first optical fiber holding casing and the end face of the first optical fiber, and the second optical fiber.
The end surface of the optical fiber holding housing and the end surface of the second optical fiber are on the same plane, and the optical axis of the first optical fiber and the optical axis of the second optical fiber coincide with each other. So that the first optical fiber holding housing and the second optical fiber holding housing are
And an end face of the first optical fiber and an end face of the second optical fiber are made of a silicone adhesive while being adhered by an adhesive layer provided between the end faces of the second optical fiber holding casing. It is characterized in that they are connected via an adhesive layer.

The invention described in claim 5 is the same as in claim 4
In the optical fiber connection part described in [1], the silicone adhesive is an ultraviolet curable adhesive.

The invention according to claim 6 is an optical fiber connecting portion, at least one of which is a first optical fiber and a second optical fiber, each of which is a non-silica fiber for optical amplification; A first optical fiber holding housing for holding an end portion of one optical fiber; and a second optical fiber holding housing for holding an end portion of the second optical fiber,
Of the optical fiber and the second optical fiber have different glass compositions, and the end face of the first optical fiber holding casing and the end face of the first optical fiber, and the second optical fiber.
The end surface of the optical fiber holding housing and the end surface of the second optical fiber are on the same plane, and the optical axis of the first optical fiber and the optical axis of the second optical fiber coincide with each other. Are arranged so that each of the end faces of the first and second optical fiber holding casings has the first and second end faces.
Has a first region near the end face of the optical fiber and a second region outside the first region, and the first region is provided with a first adhesive layer made of a silicone-based adhesive. A second adhesive layer made of a non-silicone adhesive is provided in the second region, and the first optical fiber holding case and the second optical fiber holding case are the first and the second optical fiber holding cases. The end faces of the first optical fiber and the end faces of the second optical fiber are connected to each other by being bonded by the second adhesive layer.

The invention described in claim 7 is the same as claim 6
In the optical fiber connection part described in (1) above, the first region and the second region are the first optical fiber holding casings and the first optical fiber holding casings on the end face of at least one of the first optical fiber holding casings. Alternatively, it is characterized by being defined by a groove portion provided in a region located near the end face of the second optical fiber.

The invention described in claim 8 is the same as claim 6
Alternatively, in the optical fiber connecting part described in 7, the non-silicone adhesive is an epoxy adhesive or an acrylic adhesive.

The invention described in claim 9 is the same as claim 6
In the optical fiber connection part according to any one of 1 to 8, the silicone-based adhesive and the non-silicone-based adhesive are
Both are characterized by being an ultraviolet curable adhesive.

According to a tenth aspect of the invention, there is provided the optical fiber connecting section according to any one of the first to ninth aspects,
At least one of the first optical fiber and the second optical fiber is a non-quartz light selected from the group consisting of Zr-based fluoride fibers, In-based fluoride fibers, chalcogenide-based glass fibers and tellurite glass fibers. It is characterized by being a fiber.

According to the eleventh aspect of the present invention, in the optical fiber connection section of the tenth aspect, the core refractive index n ₁ of the first optical fiber and the core refractive index n of the second optical fiber are ₂ has a value different from _2, and each of the first optical fiber and the second optical fiber has a predetermined inclination angle θ with respect to the perpendicular of the connecting surface of the first and second optical fibers. and it provided with the first inclined angle theta ₂ of the inclination angle theta ₁ and the second optical fiber of the optical fiber is set so as to satisfy the following expression, the selected non-silica-based optical The inclination angle θ of the fiber is 3 degrees or more in the case of Zr-based fluoride fiber and 4 in the case of In-based fluoride fiber.
Or more, 8 degrees or more in the case of chalcogenide glass fiber, and 8 degrees or more in the case of tellurite glass fiber.

[0054]

[Equation 3]

The invention described in claim 12 is characterized in that, in the optical fiber connection part according to claim 11, a rare earth element is added to the selected optical fiber.

The thirteenth aspect of the present invention is an optical fiber amplifier including the optical fiber connection section according to any one of the first to twelfth aspects.

[0057]

[0058]

[0059]

[0060]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an optical fiber connecting portion according to the first invention will be described with reference to FIGS. 1, FIG. 2 and FIG. 3 are schematic side views for explaining the schematic configuration of the optical fiber connection portion, and the application locations or application methods of the adhesive are different. The greatest feature of these optical fiber connecting portions is that no optical adhesive is present on the fiber connecting end faces of the non-silica optical fiber and the silica fiber. However, the inclination angle θ ₁ [rad] of the connecting end face of the non-silica optical fiber with respect to the vertical axis and the inclination angle θ of the connecting end face of the silica optical fiber with respect to the vertical axis
The relationship with ₂ [rad] satisfies Expression 3 as in the case of Conventional Example 5 already described. In the figure, reference numeral 1 is a non-silica fiber,
2 is a silica-based fiber, 3-1 and 3-2 are optical fiber holding casings for holding the ends of the optical fibers 1 and 2, respectively.
-1, 4-2 are connection surfaces of the optical fiber holding housings 3-1, 3-2, 5 is an adhesive, and 6 (6-1, 6-2) is a connection surface 4-1 of the optical fiber holding housing. , 4-2 is a groove for storing an adhesive agent formed on the base plate 4-2.

The configuration shown in FIG. 1 has an optical fiber holding housing 3
−1 of the connection surface 4-1 and the connection surface 4-2 of the optical fiber holding housing 3-2 are completely brought into close contact with each other, and the optical fiber holding housing 3-
1 is a method of fixing an adhesive 5 between both sides of a portion where the optical fiber holding housing 3-2 and the optical fiber holding housing 3-2 are in close contact with each other.

The structure shown in FIGS. 2 and 3 has a structure in which the connecting surface 4-1 of the optical fiber holding housing 3-1 and the optical fiber holding housing 3 are connected.
-2 and the connecting surface 4-2 are completely adhered and fixed via the adhesive layer 5 made of an adhesive. At this time, in order to prevent the adhesive from spreading to the area corresponding to the connecting portion between the non-silica optical fiber 1 and the silica optical fiber 2 and its vicinity,
The area where the adhesive layer 5 is provided is limited. further,
In FIG. 3, the connection surfaces 4-1 and 4-2 of the optical fiber holding housing are shown.
Grooves 6-1 and 6-2 for storing the adhesive are formed on the top. By providing the grooves 6-1 and 6-2 as described above, the adhesive layer forming the pressed adhesive layer 5 when the connecting surface 4-1 and the connecting surface 4-2 are brought into close contact with each other is a non-quartz type adhesive layer. It is possible to prevent the fluid from flowing into a region corresponding to the connecting portion between the optical fiber 1 and the silica optical fiber 2 and the vicinity thereof. Further, it becomes easy to clearly define the portion where the adhesive layer 5 is present and the portion where the adhesive layer 5 is not present (the surface including the fiber connection end faces of the non-silica optical fiber 1 and the silica optical fiber 2). The groove may be formed on at least one of the connection surfaces of the optical fiber holding casings.
In the configuration shown in FIG. 2, the adhesive reservoir grooves 6-1 and 6-2 are provided.
Are formed in parallel lines extending in the width direction. However, the present invention is not limited to such a line shape, and may be arranged like a concentric circle shape in the figure. A specific example thereof is shown in FIG.

FIG. 4 is for explaining the shape of the adhesive reservoir groove formed on the adhesive surface of the optical fiber holding casing. FIG. 4A is a side view of the optical fiber holding housing,
(B) is a front view seen from the connection end face of the optical fiber holding casing corresponding to the side view of (a), and is a linear adhesive reservoir groove 6-1 applied to the configuration of FIG. 6-2 is shown. On the other hand, FIG. 4C shows an adhesive reservoir groove formed concentrically with the axis of the optical fiber. Furthermore, in FIG.
Although the adhesive collecting groove is provided on both the connecting surface 4-1 and the connecting surface 4-2, if the adhesive collecting groove is present on at least one of the connecting surfaces, it is possible to determine that the connecting surface has the adhesive. It is possible to realize the missing surface.

As described above, the optical fiber connecting portion according to the first aspect of the present invention, as shown in FIGS. 1, 2 and 3, has a connecting end face of a non-silica type optical fiber and a connecting end face of a silica type fiber. There is no optical adhesive layer between the and. Therefore, it is possible to solve the problem that "the optical adhesive 5 is deteriorated and the connection part is damaged", which is a common problem to be solved in the conventional examples 2, 3, 4, and 5.
As a result, it becomes possible to construct a highly reliable optical fiber amplifier using a non-quartz fiber that has been conventionally required.

In the optical fiber splicing part based on the first aspect of the invention, the angle θ _{1 of the} non-silica fiber necessary for realizing practically low reflection (reflection attenuation amount of 60 dB or more).
As in the case of Conventional Example 5, telluride-based fiber is 8 degrees or more, chalcogenide-based fiber is 8 degrees or more, Zr-based fluoride fiber is 3 degrees or more, and In-based fluoride fiber is 4 degrees or more.

Next, the optical fiber connection portion based on the second invention will be described.

The greatest feature of this optical fiber connecting portion is that a silicone-based photo-curing adhesive is interposed between the connecting end surface of the non-quartz optical fiber and the connecting end surface of the quartz fiber. However, the relationship between the inclination angle θ ₁ [rad] of the connecting end face of the non-silica type optical fiber with respect to the vertical axis and the inclination angle θ ₂ [rad] of the connecting end face of the silica type optical fiber with respect to the vertical axis is the same as in the conventional example 5 described above. Expression 3 is satisfied similarly to.

From the viewpoint of adhesive strength and environmental resistance, epoxy-based or acrylic UV-curable resins have been used as optical adhesives. However, when the connection part using these epoxy or acrylic UV-curable optical adhesives is applied as a connection part for an optical amplifier, a rare-earth-doped (Pr, Er, etc.) non-quartz fiber generated visible light is generated. The epoxy or acrylic optical adhesive is discolored by light and ultraviolet light to become a light absorbing medium. As a result, this absorption medium absorbs the excitation light,
There is a problem that heat is generated and the connection portion is destroyed.
In order to solve such a problem, the present inventor examined changes in transmittance of epoxy-based, acrylic-based, and silicone-based optical adhesives with respect to ultraviolet light irradiation time. Table 1 shows the examination results.

[0069]

[Table 1]

The change in transmittance of the epoxy-based, acrylic-based, and silicone-based optical adhesives with respect to the irradiation time of ultraviolet light (irradiation light wavelength: 0.42 μm, irradiation intensity: 95 mW / cm ² ) was the same as that of the epoxy-based, acrylic-based, and The silicone adhesive was 10 mm thick and the measurement wavelength was 0.8 μm. As shown in Table 1, the epoxy-based and acrylic-based optical adhesives increased with increasing irradiation time of ultraviolet light.
It can be seen that while the transmittance decreases and the color changes to pale yellow (observation with the naked eye), the silicone-based optical adhesive has stable transmittance even when irradiated with ultraviolet light.
As a result, even if the silicone-based optical adhesive is interposed between the connection end surface of the non-silica fiber and the connection end surface of the silica fiber, there is a problem in the conventional technique (conventional examples 2, 3, 4, and 5). There is no problem of deterioration of the optical adhesive and damage of the connection part.

The structure of the optical fiber connecting portion using the silicone optical adhesive is shown in FIGS. 3, 4 and 5. In these drawings, reference numeral 1 is a non-silica fiber, 2 is a silica fiber, 3-1 and 3-2 are optical fiber holding housings for holding the ends of the optical fibers 1 and 2, respectively.
1, 4-2 are connection surfaces of the optical fiber holding housings 3-1 and 3-2, 5 is an adhesive, and 6 (6-1, 6-2) are connection surfaces 4-1 of the optical fiber holding housing. A groove for storing an adhesive formed on 4-2, and 7 a silicone optical adhesive layer.

In the structure shown in FIG. 5, the silicone optical adhesive 7 is applied to the entire connecting surfaces 4-1 and 4-2 of the two optical fiber holding cases 3-1 and 3-2. At this time, the silicone optical adhesive 7 is also interposed between the connection end surface of the optical fiber 1 and the connection end surface of the optical fiber 2.

In the configuration shown in FIG. 6, the connecting surface 4-1 of the optical fiber holding housing 3-1 and the connecting surface 4-2 of the optical fiber holding housing 3-2 are provided with an adhesive layer 5 made of an adhesive agent. Completely adhered and fixed. At this time, the area where the adhesive layer 5 is provided is limited so that the adhesive 5 does not spread to the area corresponding to the connection between the non-silica optical fiber 1 and the silica optical fiber 2 and the vicinity thereof. Also, the adhesive 5
The silicone-based optical adhesive 7 is interposed in a region where no connection exists, that is, between the connection surface of the optical fiber 1 and the connection surface of the optical fiber 2 and in a region near the connection surface.

In the configuration shown in FIG. 7, the adhesive reservoir grooves 6-1 and 6- are formed on the connection surfaces 4-1 and 4-2 of the optical fiber holding casing.
2 is formed. By providing the grooves 6-1 and 6-2 as described above, the adhesive layer forming the pressed adhesive layer 5 when the connecting surface 4-1 and the connecting surface 4-2 are brought into close contact with each other is a non-quartz type adhesive layer. It is possible to prevent the fluid from flowing into a region corresponding to the connecting portion between the optical fiber 1 and the silica optical fiber 2 and the vicinity thereof. Further, it becomes easy to clearly define the portion where the adhesive layer 5 is present and the portion where the adhesive layer 5 is not present (the surface including the fiber connection end faces of the non-silica optical fiber 1 and the silica optical fiber 2). Further, the regions where the adhesive layer 5 is not interposed, that is, the grooves 6-1 and 6
The silicone-based optical adhesive 7 is interposed between the connecting surface of the optical fiber 1 and the connecting surface of the optical fiber 2 at the boundary of −2, and in a region near the connecting surface. in this way,
In the configuration shown in FIG. 7, since the adhesive reservoir grooves 6-1 and 6-2 are formed, it is easy to clearly separate the portion where the adhesive layer 5 is present and the portion where the silicone optical adhesive layer 7 is provided. It is possible to provide. In addition, in FIG. 7, the adhesive reservoir grooves 6-1 and 6-2 are provided in a line shape, but the present invention is not limited to this, and it is also possible to form the concentric shape shown in FIG. Is. Further, in FIG. 7, the connection surface 4-1 and the connection surface 4 are
-2 is provided with the adhesive reservoir groove, but if the adhesive reservoir groove is present on at least one of the connection surfaces, a connection surface with adhesive and a surface without adhesive can be realized. .

As described above, the optical fiber connecting portion according to the second invention is, as shown in FIGS. 5 to 7, between the connecting end surface of the non-silica type optical fiber and the connecting end surface of the quartz type fiber. Since the silicone-based optical adhesive layer is interposed in the above, the problem that "the optical adhesive 5 is deteriorated and the connection portion is damaged", which is a common problem to be solved in the conventional examples 2, 3, 4, and 5, is solved. It becomes possible to do. As a result, it becomes possible to construct a highly reliable optical fiber amplifier using a non-quartz fiber that has been conventionally required.

In the optical fiber splicing part based on the first aspect of the invention, the angle θ _{1 of the} non-silica fiber required to realize practically low reflection (reflection attenuation amount of 60 dB or more).
As in the case of Conventional Example 5, telluride-based fiber is 8 degrees or more, chalcogenide-based fiber is 8 degrees or more, Zr-based fluoride fiber is 3 degrees or more, and In-based fluoride fiber is 4 degrees or more.

The first and second parts will be described below with reference to the drawings.
The optical fiber splicing part based on the invention will be described in more detail. However, the embodiments described below are merely examples of the present invention and do not limit the scope of the present invention in any way.

(Embodiment 1) In Embodiment 1, a first connection technique of the present invention will be described.

(I) Example of Embodiment 1-1 FIG. 8 shows a schematic structure of an optical fiber connecting section based on the example of the present embodiment. FIG. 8A is a side view showing the entire optical fiber connecting section. b) is a side view showing a connection end face of the optical fiber holding casing. In the figure, reference numeral 1 is an Er-doped telluride glass fiber (the glass composition is TeO ₂ -ZnO.
-Na ₂ O, core refractive index 2.1, mode field radius 5 μm, Er addition concentration 4000 ppm, coating of this fiber is UV resin, 2 is silica fiber (core refractive index is ~ 1.5, mode The field radius is 5 μm, the coating is UV resin), and 8-1 and 8-2 are V-groove type optical fiber holding casings for holding the ends of the optical fibers 1 or 2, respectively. The optical fiber holding casings 8-1 and 8-2 are provided with the V-groove substrate 9 inside.

In the optical fiber connecting portion composed of such components, the optical fibers 1 and 2 are positioned by the V-groove substrate 9 provided in the optical fiber holding casings 8-1 and 8-2, respectively. It was provided by being fixed to the V-groove type optical fiber holding housings 8-1 and 8-2 by the adhesive 10 and the optical fiber fixing plate 11. V-groove type optical fiber holding housing 8-
1, 8-2, V groove substrate 9, and optical fiber fixing plate 11
The material used was made of Pyrex glass. In the present embodiment example, V-groove type optical fiber holding housings 8-1, 8-
The connection end faces 12-1 and 12-2 of No. 2 are completely adhered to each other without an optical adhesive, and the V-groove type optical fiber holding housings 8-1 and 8-2 are fixed on both sides thereof. The space was fixed to the side by an epoxy adhesive 5.

The optical fiber 1 and the silica-based fiber 2 are
Θ with respect to the vertical axis of each connection end face 12-1, 12-2
_{It was held at 1} = 18 [deg] and θ ₂ = 25 [deg]. By this connection, it was possible to connect the Er-doped telluride glass fiber 1 and the silica-based fiber 2 with a connection loss of 0.1 dB. However, the splice loss was measured at 1.2 μm where there was no absorption of Er ions in the Er-doped telluride glass fiber 1.

The return loss measured from the Er-doped telluride glass fiber 1 side and the silica type fiber 2 side was 60 dB or more, respectively (the commercially available return loss measuring instrument was used for the measurement, and the measurement wavelength was 1.2 μm). , This measurement device cannot measure a return loss of 60 dB or more, and this connection part shows a high-performance low reflection characteristic higher than the measurement range of the measurement device).

Of the optical fiber 1 and the silica-based fiber 2,
The angles of the respective connection end faces 12-1 and 12-2 with respect to the vertical axis are [θ ₁ = 8 [deg], θ ₂ = 11.2 [de]
g]], [θ ₁ = 14 [deg], θ ₂ = 20 [de]
g]], the splice loss between the Er-doped telluride glass fiber 1 and the silica-based fiber 2 is 0.1 dB (measurement wavelength 1.2 μm). The return loss measured from the 2 side was 60 dB or more.
However, when the angles of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of the respective connection end faces 12-1 and 12-2 are set to [θ ₁ = 5 [deg], θ ₂ = 7 [deg]]. , Er-doped telluride glass fiber 1 and silica fiber 2 have a connection loss of 0.2 dB (measurement wavelength of 1.2).
μm). However, the return loss measured from the Er-doped telluride glass fiber 1 side was 56 dB. As a result, in order to connect the telluride glass fiber and the silica-based fiber with low loss and low reflection (reflection attenuation amount of 60 dB or more), the telluride glass fiber should be 8 [deg] or more with respect to the vertical axis of the connection end face. It turns out that an angle is required.

In the above description, the Er-doped telluride glass fiber is used. However, other In-based fluoride fibers, Zr-based fluoride fibers, chalcogenide-based fibers (rare earth elements Er, Pr, Tm, etc. are added respectively). The same good connection as above is realized by setting the angle θ ₁ to 8 degrees or more for chalcogenide fiber, 3 degrees or more for Zr system fluoride fiber, and 4 degrees or more for In system fluoride fiber. did it.

(Ii) Embodiment 1-2 FIG. 9 shows a schematic structure of an optical fiber connecting portion based on this embodiment, (a) is a side view showing the entire optical fiber connecting portion, b) is a side view showing a connection end face of the optical fiber holding casing. In the figure, reference numeral 1 is an Er-doped telluride glass fiber (the glass composition is TeO ₂ -ZnO.
-Na ₂ O, core refractive index 2.1, mode field radius 5 μm, Er addition concentration 4000 ppm, coating of this fiber is UV resin, 2 is silica fiber (core refractive index is ~ 1.5, mode The field radius is 5 μm, and the coating is UV resin. In this embodiment, glass ferrules 13-1 and 13-2 are used as the optical fiber holding housing (the connection end faces 14-1 and 14-2 are each glass). It was realized by obliquely polishing the ferrules 13-1 and 13-2).

For the Er-doped telluride glass fiber 1 and the silica-based fiber 2, a glass ferrule 13-1, 13- was prepared by using an adhesive 10 (using an acrylic UV adhesive).
Fixed to 2. An epoxy type adhesive was used as the adhesive 5 for fixing the side surface. Optical fiber 1 and fiber 2
Of the connection end faces 14-1 and 14-2 with respect to the vertical axis are θ ₁ = 12 [deg] and θ ₂ = 17 [deg].
The connection loss between the Er-doped telluride glass fiber 1 and the silica-based fiber 2 is 0.2 dB (measurement wavelength is 1.2 μm).
m), the return loss measured from the Er-doped telluride glass fiber 1 and the silica-based fiber 2 side is 60d, respectively.
Achieved B or higher.

Further, as in the embodiment 1-1, the telluride glass fiber and the connecting end face / perpendicular, which are necessary for connecting the telluride glass fiber and the silica fiber with low loss and low reflection (reflection attenuation of 60 dB or more), The angle between the axes is 8
It was more than [deg].

In the above description, the Er-doped telluride glass fiber is used, but other In-based fluoride fibers, Zr-based fluoride fibers, chalcogenide-based fibers (rare earth elements Er, Pr, Tm, etc. are added respectively). The same good connection as above is realized by setting the angle θ ₁ to 8 degrees or more for chalcogenide fiber, 3 degrees or more for Zr system fluoride fiber, and 4 degrees or more for In system fluoride fiber. did it.

(Iii) Embodiment 1-3 FIG. 10 shows a schematic structure of an optical fiber connecting portion based on this embodiment. (A) is a side view showing the whole optical fiber connecting portion, b) is a side view showing a connection end face of the optical fiber holding casing. Further, FIG. 11 is a modification of FIG. 10, in which a ferrule is used as an optical fiber holding housing, and (a) is a side view showing the entire optical fiber connecting portion,
(B) is a side view showing a connection end face of the optical fiber holding casing. In the figure, reference numeral 1 is a Pr-doped Zr-based fluoride fiber (glass composition: ZrF ₄ —BaF ₂ —LaF ₃ —Y).
F ₃ -AlF ₃ -LiF-NaF, core refractive index: 1.5
5, mode field radius: 4 μm, coating: UV resin,
Pr doping concentration is 1000 ppm, 2 is silica fiber (core refractive index is ~ 1.5, mode field radius is 4μ)
m, coating is UV resin), 8-1 and 8-2 are V-groove type optical fiber holding casings for holding the ends of the optical fibers 1 or 2, respectively, and each optical fiber 1 or 2 is a V-groove. It was positioned by the substrate 9 and fixed to the V-groove type optical fiber holding housing 8-1 or 8-2 by the adhesive 10 and the optical fiber fixing plate 11. V-groove type optical fiber holding housing 8-1,
8-2, the V-groove substrate 9 and the optical fiber fixing plate 11 were made of Pyrex glass.

Further, reference numerals 13-1 and 13- in FIG.
Reference numeral 2 denotes a ferrule used as an optical fiber holding housing. Here, the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 are bonded to the glass ferrules 13-1 and 13- using an adhesive 10 (using an acrylic UV adhesive).
Fixed to 2.

In the present embodiment, as shown in FIGS. 10 and 11, the adhesive layer 5 is provided on the connection end faces 12-1 and 12- which do not include the fiber connection face between the optical fiber 1 and the optical fiber 2.
2 or 14-1 and 14-2 only, the V-groove type optical fiber holding housings 8-1 and 8-2 or the ferrules 13-1 and 13 to which the optical fibers 1 and 2 are fixed are provided.
-2 is aligned so that the connection loss between the optical fibers 1 and 2 is minimized, and then the connection end faces 12-1 and 12-2 or 14-1.
And 14-2 are brought into close contact with each other, and an ultraviolet curing adhesive is applied to the interface from the side surface of the V-groove type optical fiber holding housings 8-1, 8-2 or the ferrules 13-1, 13-2 by using a capillary phenomenon. This is achieved by injecting the agent 5 and curing the adhesive 5 using ultraviolet rays before the adhesive 5 reaches the fiber connecting surface between the optical fibers 1 and 2.

The optical fiber 1 and the silica-based fiber 2 are
Each of the connection end faces 12-1, 12-2 or 14-1,
14-2 with respect to the vertical axis, θ ₁ = 3 [deg], θ ₂ =
It was held at 3.1 [deg]. By this connection (both when the V-groove type optical fiber holding housing 8 is used and when the ferrule 13 is used), the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB or less. I was able to connect. However, the connection loss is 1.2 μ, which is the case where Pr ions are not absorbed in the Pr-doped Zr-based fluoride fiber 1.
It was measured in m. The return loss measured from the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 60 dB or more (both when the V-groove type optical fiber holding housing 8 is used and when the ferrule 13 is used. )
(A commercially available return loss measurement instrument was used for measurement, the measurement wavelength was 1.2 μm, and this measurement instrument cannot measure return loss of 60 dB or more. Shows high performance and low reflection characteristics above).

Further, the connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2 respectively.
The angles of −1 and 14-2 with respect to the vertical axis are [θ ₁ = 4
Even when [deg] or θ ₁ = 6 [deg]] is set, the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB (measurement wavelength is 1.3 μm).
m), the return loss measured from the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 60 dB each.
That was all. However, the angles of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axes of the respective connection end faces 12-1, 12-2 or 14-1, 14-2 are [θ ₁ =
2 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB.
Although the measurement wavelength was 1.2 μm, the return loss measured from the Pr-doped Zr-based fluoride fiber 1 side was 53d.
As a result, the Zr-based fluoride fiber and the silica-based fiber have low loss and low reflection (reflection attenuation amount of 60 dB or more).
It was found that an angle of 3 [deg] or more with respect to the vertical axis of the connection end face of the Zr-based fluoride fiber was required for the connection.

In the above description, the Pr-added Zr-based fluoride fiber is used, but other In-based fluoride fibers, telluride-based fibers, chalcogenide-based fibers (rare earth elements Er, Pr, Tm, etc. are added respectively). The same good connection as above was realized by setting the angle θ ₁ to In-based fluoride fiber 4 ° or more, telluride-based fiber 8 ° or more and chalcogenide-based fiber 8 ° or more.

(Iv) Embodiment 1-4 FIG. 12 shows a schematic structure of an optical fiber connecting portion based on this embodiment, (a) is a side view showing the entire optical fiber connecting portion, b) is a side view showing a connection end face of the optical fiber holding casing. FIG. 13 is a modification of FIG. 12, in which a ferrule is used as an optical fiber holding housing, and (a) is a side view showing the entire optical fiber connecting portion.
(B) is a side view showing a connection end face of the optical fiber holding casing. In the figure, reference numeral 1 Pr added In-based fluoride fiber (glass composition: InF ₃ -GaF ₃ -ZnF ₂ -P
bF ₂ —BaF ₂ —SrF ₂ —YF ₃ —NaF, core refractive index: 1.65, mode field radius 4.5 μm, coating: UV resin, Pr addition concentration 1000 ppm, 2 silica fiber (core refractive index) Is ~ 1.5, mode field radius is 4.5 μm, coating is UV resin), 8-1, 8
-2 is V for holding the ends of the optical fibers 1 or 2, respectively.
It is a groove type optical fiber holding housing, and each optical fiber 1 or 2 is positioned by a V groove substrate 9 and adhesive 1
0 and the optical fiber fixing plate 11 were fixed to the V-groove type optical fiber holding housing 8-1 or 8-2.

V-groove type optical fiber holding housings 8-1, 8-
2. The materials for the V-groove substrate 9 and the optical fiber fixing plate 11 were made of Pyrex glass. Adhesive reservoir grooves 15-1 and 15-2 are formed in the connection surfaces 12-1 and 12-2 of the V-groove type optical fiber housing 8-1 or 8-2.

Further, reference numerals 13-1, 13- in FIG.
Reference numeral 2 denotes a ferrule used as an optical fiber holding casing (Pr-doped In-fluoride fiber 1 and quartz-based fiber 2 use an adhesive agent 10 (using an acrylic UV adhesive agent) for a glass ferrule 13-1, 13-2 fixed). Connection surface 1 of ferrule 13-1 or 13-2
Adhesive reservoir grooves 16-1, 16-2 are provided at 4-1 and 14-2.
Is being processed.

In this embodiment, as shown in FIG. 12 and FIG. 13, the adhesive layer 5 is provided on the connection end faces 12-1 and 12-2 or 14-1 and 14- which do not include the connection faces of the optical fibers 1 and 2. Since it is provided only on the optical fiber 2, the V-groove type optical fiber holding housings 8-1 and 8-2 or the ferrules 13-1 and 13-2 to which the optical fibers 1 and 2 are fixed have the minimum connection loss between the optical fibers 1 and 2. So that the connection end faces 12-1 and 1
2-2 or 14-1 and 14-2 are brought into close contact with each other, and a V-groove type optical fiber holding housing 8 is formed on the interface by using a capillary phenomenon.
The ultraviolet curable adhesive 5 was injected from the side surface of the -1, 8-2 or the ferrules 13-1, 13-2. Adhesive 5
Is an adhesive reservoir groove 15-1, 15-2 or 16-1,
The penetration was blocked by 16-2.

By using the groove for accumulating the adhesive used in this embodiment, the adhesive layer 5 is provided with the connection end faces 12-1 and 12-2 or 14-1 which do not include the connection face of the optical fibers 1 and 2.
And the connection structure provided only in 14-2 is the same as the embodiment 1-3.
It was also found that it can be realized more reliably than in.

The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 14 respectively.
Θ ₁ = 4 [deg] with respect to the vertical axes of −1 and 14-2,
It was held at θ ₂ = 4.1 [deg]. This connection (when using the V-groove type optical fiber holding casing 8 and the ferrule 1
3), the connection loss between the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 0.15.
I was able to connect at less than dB. However, the splice loss is that there is no absorption of Pr ions in the Pr-doped In-based fluoride fiber 1,
It was measured at 1.2 μm.

Further, Pr-doped In-based fluoride fiber 1
And the return loss measured from the silica fiber 2 side is
Each was 60 dB or more (both when the V-groove type optical fiber holding housing 8 was used and when the ferrule 13 was used) (a commercially available return loss measuring instrument was used for measurement, measurement wavelength was 1.2 μm, This measurement device cannot measure return loss of 60 dB or more, and this connection part exhibits high-performance low reflection characteristics higher than the measurement range of the measurement device).

Further, the connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2 respectively.
The angles of -1, 14-2 with respect to the vertical axis are [θ ₁ = 5
Even when [deg] or θ ₁ = 6 [deg]] is set, the connection loss between the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB (measurement wavelength is 1.3 μm).
m), the return loss measured from the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 60 dB each.
That was all. However, the angles of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axes of the respective connection end faces 12-1, 12-2 or 14-1, 14-2 are [θ ₁ =
3 [deg]], the connection loss between the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB.
Although the measurement wavelength was 1.2 μm, the return loss measured from the Pr-doped In-based fluoride fiber 1 side was 59 dB.
Met. As a result, in order to connect the In-based fluoride fiber and the silica-based fiber with low loss and low reflection (reflection attenuation amount of 60 dB or more), the In-based fluoride fiber is set to 3 [] with respect to the vertical axis of the connection end face. It was found that it is required to incline at an angle of deg] or more and connect.

In the above description, the Pr-doped In-based fluoride fiber is used. However, other Zr-based fluoride fiber, telluride-based fiber, chalcogenide-based fiber (rare earth elements Er, Pr, Tm, etc. are added, respectively). The same good connection as above was realized by setting the angle θ ₁ to Zr-based fluoride fiber 3 ° or more, telluride-based fiber 8 ° or more, and chalcogenide-based fiber 8 ° or more. .

Further, by the connection method shown in the above-mentioned Embodiments 1-1 to 1-4, Er-doped telluride glass fiber 1 (glass composition: TeO ₂ —ZnO—Na ₂ O, core refractive index: 2.1, mode: Field radius is 5 μm, Er concentration is 4000 ppm, fiber length is 1 m, coating is U
A silica fiber was connected to both ends of the V resin) to construct the optical fiber amplifier shown in FIG. In the figure, reference numeral 17-
Reference numerals 1 and 17-2 are pumping light source units for generating pumping light to the optical fiber 1. For the Er-doped telluride glass fiber 1, semiconductor lasers having an oscillation wavelength of 1.48 μm (each output is 200 mW) were used. Further, reference numerals 18-1 and 18
Reference numeral -2 is a multiplexer for multiplexing the signal light and the pumping light generated in 17-1, 17, 2 and 19-1 and 19-2 are optical isolators for suppressing oscillation of the optical amplifier. Also, 20-
Reference numerals 1 and 20-2 denote connection portions of the present invention, and the present embodiment example 1
−1 to 1-4 connection portions (that is, FIG. 8, FIG. 9, FIG.
0, the configurations shown in FIGS. 11, 12, and 13) are applied. However, Embodiment Example 1-1 and Embodiment Example 1-
In the connection part 3 and 1-4 using the V-groove type optical fiber holding housing 8, the angle between the optical fiber 1 and the silica-based fiber and the connection end faces 12-1 and 12-2 with respect to the vertical axis is θ ₁ = 14.
[Deg], θ ₂ = 20 [deg], and in the connection portion using the ferrule 1 in the embodiment example 1-2 and the embodiment examples 1-3 and 1-4, the optical fiber 1 and the silica-based fiber and the connection end face are used. The angles of 14-1 and 14-2 with respect to the vertical axis were θ ₁ = 12 [deg] and θ ₂ = 17 [deg]. By using the connection method shown in the embodiment examples 1-1 to 1-4, a signal gain of 40 dB or more of the optical fiber amplifier was realized and no ghost was generated in the optical fiber amplifier.

FIG. 14B shows an example of the amplification characteristics of the present fiber amplifier (the figure shows the characteristics of those connected by using Embodiment 1-1, but Embodiments 1-2 and Embodiments 1-2). Similar results were obtained with the V-groove type optical fiber holding casing 8 and the ferrule 13 of 1-3 and 1-4).

Further, FIG. 15 shows embodiment examples 1-1 to 1-1.
4 shows the time change of the signal gain of the optical amplifier configured by using the connection part of −4. The signal wavelength is 1.54 μm. Also,
The figure also shows the characteristics of the optical fiber amplifier configured by using the method of Conventional Example 5. As shown in the figure, by using the connecting portions of Embodiments 1-1 to 1-4, it is possible to solve the problem that the optical adhesive is deteriorated and the connecting portions are damaged, which cannot be solved in the conventional example 5. , A reliable optical fiber amplifier using non-silica fiber was constructed.

Further, the embodiment example 1-1 (FIG. 8), the embodiment example 1-3 (FIG. 10), and the embodiment example 1-4 (FIG. 1).
In 2), the V-groove type optical fiber holding housing 8, the embodiment example 1-
2 (FIG. 9), the embodiment example 1-3 (FIG. 11), and the modification example (FIG. 13) of the embodiment example 1-4, the ferrule 13 was used, but the connecting portion using the ferrule 13 is connected. It was found from an actual work that the part manufacturing time can be shortened (V-groove type optical fiber holding housing, manufacturing time: 45
Min, ferrule / production time: 10 minutes). This is because when manufacturing the V-groove type optical fiber holding casing 8, each optical fiber 1 or 2 is positioned by the V-groove substrate 9 and the adhesive 1
0 and the optical fiber fixing plate 11 are used to fix them to the V-groove type optical fiber holding housing 8, while
The ferrule 13 is realized by a very simple operation of passing the optical fiber 1 or 2 through the hole of the ferrule 13 and fixing it with the adhesive 10.

Furthermore, in the connection parts of the embodiment example 1-1 and the embodiment example 1-2, the optical fiber holding casings 8-1, 8 are provided.
-2 or fixing the ferrules 13-1 and 13-2,
The side surface fixing method of fixing the both sides with the adhesive 5 was used. However, in this connection portion, the portion to which the adhesive 5 is applied is the side surface of the optical fiber holding housing 8-1, 8-2 or the ferrule 13-1, 13-2, and the adhesive 5 is thermally expanded. Alternatively, when contracted, the optical fiber holding housing 8-1
When the optical fiber holding housing 8-2 moves to the left or right or the ferrule 13-1 and the ferrule 13-2 move to the left or right, the connection surface of the optical fiber may be displaced. On the other hand, in the connection parts of the embodiment example 1-3 and the embodiment example 1-4, the connection end faces 12-1 and 12-2 not including the connection faces of the optical fibers 1 and 2 are used.
Alternatively, the adhesive layer 5 is provided on 14-1 and 14-2. This adhesive layer 5 is very thin (usually ~ 1 μm),
Or because the direction of thermal expansion and contraction is up and down,
In the connection portions of the example 1-3 of the embodiment and the example 1-4 of the embodiment, compared to the connection portions of the example 1-1 of the embodiment and the example 1-2 of the embodiment, a connection portion with less change in loss can be stably realized. It was

FIG. 16 shows embodiment examples 1-1 and 1-2.
5 is a graph showing changes in the connection loss of the connection part of FIG. 3 with temperature and changes of the connection loss of the connection parts of Embodiments 1-3 and 1-4 with temperature. As shown in FIG. 16, the temperature change may be performed by increasing the temperature from room temperature (20 ° C.) to 60 ° C. or gradually decreasing the temperature from 60 ° C. to 0 ° C. and then returning to room temperature, as shown in FIG. I went. In the curve regarding the loss characteristic, the broken line indicates the embodiment example 1-1 and the embodiment example 1-2.
The solid line and the solid line relate to the embodiment example 1-3 and the embodiment example 1-4.

As for the plot of each curve, the values of the samples showing the largest change in the loss characteristics among the predetermined number of samples were plotted as follows. That is, the first embodiment example
-3 and 1-4 of the number of samples of the optical fiber connection portion (5 samples having the configuration of FIG. 9, 5 samples having the configuration of FIG. 11, 5 samples having the configuration of FIG. 12, and FIG. The characteristics of the sample having the most remarkable fluctuation among the 5 samples having the constitution) were plotted, and a solid curve as shown in the figure was obtained.

In addition, the number of the samples of the optical fiber connecting portions of the embodiment examples 1-1 and 1-2 is 20 (10 samples having the configuration of FIG. 8 and 10 samples having the configuration of FIG. 9). The characteristics of those with significant fluctuations were plotted, and a dashed curve as shown in the figure was obtained. As the optical fiber 1, a Pr-doped In-based fluoride fiber (glass composition: In
_{F 3 -GaF 3 -ZnF 2 -PbF 2} -BaF 2 -Sr
F ₂ -YF ₃ -NaF, core refractive index: 1.65, mode field radius: 4.5 μm, coating: UV resin, Pr-added concentration is 1000 ppm), as the optical fiber 2, a silica-based fiber (core refractive index: ~ 1.5, mode field radius: 4.5 μm, coating: UV resin), θ 1 is 3 [deg] with respect to the vertical axis of the connection end face, and θ ₂ is 3.1 [de]
g]. From the same characteristics, Embodiment Examples 1-3 and 1-
It was found that the optical fiber connection part of No. 4 can realize an optical fiber connection part having thermal stability.

Further, in the above embodiment, the optical fiber holding housing 8 and the ferrule 13 are made of glass, but the same result is obtained even if the plastic is used.

Embodiment 2 In Embodiment 2, the second connection technique of the present invention will be described.

(I) Embodiment 2-1 FIG. 17 shows a schematic structure of an optical fiber connecting portion based on this embodiment. (A) is a side view showing the entire optical fiber connecting portion, b) is a side view showing a connection end face of the optical fiber holding casing. 18 is a modification of FIG. 17, in which a ferrule is used as an optical fiber holding housing, (a) is a side view showing the entire optical fiber connecting portion, and (b) is an optical fiber holding housing. It is a side view which shows the connection end surface of. In the figure, reference numeral 1 is a Pr-doped chalcogenide glass fiber (glass composition: As-S, core refractive index:
2.4, mode field radius: 3 μm, coated UV resin, Pr addition concentration is 1000 ppm, 2 is a silica fiber (core refractive index: up to 1.5, mode field radius:
5 μm, coating: UV resin), 8-1 and 8-2 are V-groove type optical fiber holding casings for holding the ends of the optical fibers 1 or 2, respectively, and each optical fiber 1 or 2 is V-shaped.
It is positioned by the groove substrate 9 and fixed to the V-groove type optical fiber holding housing 8-1 or 8-2 by the adhesive 10 and the optical fiber fixing plate 11 (FIG. 18).

V-groove type optical fiber holding housings 8-1, 8-
2. The materials for the V-groove substrate 9 and the optical fiber fixing plate 11 were made of Pyrex glass.

Reference numerals 13-1, 13- in FIG.
2 is a glass ferrule, and the Pr-added chalcogenide glass fiber 1 and the silica-based fiber 2 are glass ferrules 13-using an adhesive (acrylic UV adhesive).
It was fixed to 1, 13-2.

Pr-doped chalcogenide glass fiber 1
The connection between the silica-based fiber 2 and the silica-based fiber 2 is, as shown in FIGS. 17 and 18, between the connection end faces 12-1 and 12-2 of the V-groove type optical fiber holding housings 8-1 and 8-2 or the glass ferrule 13-1. , 13-2 between the connection end faces 14-1 and 14-2 by using an ultraviolet curing type silicone adhesive 7 for fixing.

The optical fiber 1 and the silica-based fiber 2 are
Each of the connection end faces 12-1, 12-2 or 14-1,
14-2 with respect to the vertical axis, θ ₁ = 18 [deg], θ ₂
= 25 [deg].

By this connection, the connection loss between the Pr-doped chalcogenide glass fiber 1 and the silica fiber 2 is 0.
I was able to connect with 2 dB. However, the splice loss was measured at 1.2 μm where there is no absorption of Pr ions in the Pr-doped chalcogenide glass fiber 1.

The return loss measured from the Pr-doped chalcogenide glass fiber 1 side and the silica fiber 2 side was 60 dB or more, respectively (the commercially available return loss measuring instrument was used for the measurement, and the measurement wavelength was 1.3 μm). , This measurement device cannot measure a return loss of 60 dB or more, and this connection part shows a high-performance low reflection characteristic higher than the measurement range of the measurement device).

Of the optical fiber 1 and the silica-based fiber 2,
Each of the connection end faces 12-1, 12-2 or 14-1,
The angle of 14-2 with respect to the vertical axis is [θ ₁ = 8 [de
g], θ ₂ = 11.2 [deg]], [θ ₁ = 14 [d
[Eg], θ ₂ = 20 [deg]], the splice loss between the Pr-doped chalcogenide glass fiber 1 and the silica-based fiber 2 is 0.15 dB (measurement wavelength 1.2 μm), and Pr-doped chalcogenide glass. The return loss measured from the fiber 1 side and the silica type fiber 2 side was 60 dB or more. However, optical fiber 1
And the respective connecting end faces 12-1 of the silica-based fiber 2,
The angles of 12-2 or 14-1 and 14-2 with respect to the vertical axis are [θ ₁ = 6 [deg], θ ₂ = 7 [deg]].
When set to, Pr-doped chalcogenide glass fiber 1
The connection loss between the silica-based fiber 2 and the silica-based fiber 2 was 0.2 dB (measurement wavelength 1.2 μm), but the return loss measured from the Pr-doped chalcogenide glass fiber 1 side was 55 d.
It was B.

As a result, the chalcogenide glass fiber and the silica fiber are made to have low loss and low reflection (reflection loss of 60).
It has been found that in order to make a connection of at least dB, it is required to incline the telluride glass fiber at an angle of 8 [deg] or more with respect to the vertical axis of the connection end face.

In the above description, the Pr-doped chalcogenide glass fiber was used, but other In-based fluoride fibers, Zr-based fluoride fibers, telluride-based fibers (respectively added with rare earth elements Er, Pr, Tm, etc.). The same good connection as above was achieved by setting the angle θ ₁ to 8 degrees or more for telluride-based fibers, 3 degrees or more for Zr-based fluoride fibers, and 4 degrees or more for In-based fluoride fibers. .

(Ii) Embodiment 2-2 FIG. 19 shows a schematic structure of an optical fiber connecting portion based on this embodiment, (a) is a side view showing the entire optical fiber connecting portion, b) is a side view showing a connection end face of the optical fiber holding casing. 20 is a modification of FIG. 19, in which a ferrule is used as the optical fiber holding housing, (a) is a side view showing the entire optical fiber connecting portion, and (b) is an optical fiber holding housing. It is a side view which shows the connection end surface of. In the figure, reference numeral 1 is an Er-doped Zr-based fluoride fiber (glass composition: ZrF ₄ —BaF ₂ —LaF _{3
-YF 3 -A lF 3 -LiF-NaF} , core refractive index:
1.55, mode field radius: 4 μm, coating: UV
Resin, Er added concentration: 1000 ppm), 2 is a silica fiber (core refractive index: to 1.5, mode field radius: 4 μm, coating: UV resin), reference numerals 8-1, 8-
Reference numeral 2 is a V-groove type optical fiber holding housing for holding the end portions of the optical fibers 1 or 2, respectively, and each optical fiber 1 or 2 is positioned by a V-groove substrate 9 and adhesive 10
The optical fiber fixing plate 11 was used to fix the V-groove type optical fiber holding housing 8-1 or 8-2.

V-groove type optical fiber holding housings 8-1, 8-
2. The materials for the V-groove substrate 9 and the optical fiber fixing plate 11 were made of Pyrex glass.

Also, reference numerals 13-1 and 13- in FIG.
Reference numeral 2 denotes a ferrule used as an optical fiber holding casing (Pr-doped Zr-based fluoride fiber 1 and quartz-based fiber 2 use an adhesive agent 10 (using an acrylic UV adhesive agent), and a glass ferrule 13-1, 13-2 fixed).

In Example 2-2 of the present embodiment, as shown in FIG. 19 and FIG.
End faces 12-1 and 1 not including the connection faces 2 and 2
2-2 or 14-1 and 14-2 only, and the silicone-based adhesive layer 7 is formed on the connection end faces 12-1 and 12-2 or 14-1 and 14-2 including the connection faces of the optical fibers 1 and 2. As a method of providing, before connection, the connection end faces 12-1 and 12-2 or 14-1 and 14-
The silicone-based adhesive 7 is applied to the connection end surface including the connection surface of the optical fiber 1 or 2 on one connection end surface of each of the two, and epoxy is applied to the connection end surface not including the connection surface of the optical fiber 1 or 2 of the connection end surface. V-groove type optical fiber holding housing 8 in which the optical fibers 1 and 2 are fixed after applying the system adhesive 5
It was realized by aligning the optical fiber 1 and 8-2 or the ferrules 13-1 and 13-2 so that the connection loss between the optical fibers 1 and 2 was minimized. The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 1
Θ ₁ = 3 [de with respect to the vertical axes of 4-1 and 14-2
g], θ ₂ = 3.1 [deg]. By this connection (both using the V-groove type optical fiber holding casing 8 and using the ferrule 13), Er-added Zr
The system fluoride fiber 1 and the silica system fiber 2 could be connected with a connection loss of 0.11 dB or less. However, the connection loss is
It was measured at 1.3 μm, which is the absorption of Er ions in the Er-doped Zr-based fluoride fiber 1.

Further, Er-doped Zr-based fluoride fiber 1
And the return loss measured from the silica fiber 2 side is
Each was 60 dB or more (both when the V-groove type optical fiber holding casing 8 was used and when the ferrule 13 was used) (a commercially available return loss measuring instrument was used for measurement, measurement wavelength was 1.3 μm, This measurement device cannot measure return loss of 60 dB or more, and this connection part exhibits high-performance low reflection characteristics higher than the measurement range of the measurement device).

Of the optical fiber 1 and the silica-based fiber 2,
Each of the connection end faces 12-1, 12-2 or 14-1,
The angle of 14-2 with respect to the vertical axis is [θ ₁ = 4 [de
g] or θ ₁ = 6 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 0.09 dB (measurement wavelength 1.3 μm).
m), the return loss measured from the Er-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 60 dB each.
That was all. However, the angles of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axes of the respective connection end faces 12-1, 12-2 or 14-1, 14-2 are [θ ₁ =
2 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the silica-based fiber 2 is 0.1 dB.
Although the measurement wavelength was 1.2 μm, the return loss measured from the Er-doped Zr-based fluoride fiber 1 side was 51 dB.
Met.

As a result, in order to connect the Zr-based fluoride fiber and the silica-based fiber with low loss and low reflection (reflection attenuation amount of 60 dB or more), the Zr-based fluoride fiber is set to 3 with respect to the vertical axis of the connection end face. It has been found that it is required to incline and connect at an angle of [deg] or more.

In the above description, the Er-added Zr-based fluoride fiber is used, but other In-based fluoride fibers, telluride-based fibers, chalcogenide-based fibers (rare earth elements Er, Pr, Tm, etc. are added respectively). The same good connection as above was realized by setting the angle θ ₁ to In-based fluoride fiber 4 ° or more, telluride-based fiber 8 ° or more, and chalcogenide-based fiber 8 ° or more.

(Iii) Embodiment 2-3 FIG. 21 shows a schematic structure of an optical fiber connection portion based on the present embodiment. (A) is a side view showing the entire optical fiber connection portion, b) is a side view showing a connection end face of the optical fiber holding casing. 22 is a modification of FIG. 21, in which a ferrule is used as an optical fiber holding housing, (a) is a side view showing the entire optical fiber connecting portion, and (b) is an optical fiber holding housing. It is a side view which shows the connection end surface of. In the figure, reference numeral 1 is an Er-doped In-based fluoride fiber (glass composition: InF ₃ —GaF ₃ —ZnF _{2
-PbF 2 -BaF 2 -SrF 2 -YF 3} -NaF, core refractive index: 1.65, the mode field radius: 4.5Myu
m, coating: UV resin, Er addition concentration: 1000 pp
m), 2 is a silica fiber (core refractive index: to 1.5, mode field radius: 4.5 μm, coating: UV resin), 8-1 and 8-2 are end portions of the optical fiber 1 or 2, respectively. Is a V-groove type optical fiber holding case in which each optical fiber 1 or 2 is positioned by a V-groove substrate 9 and is bonded by an adhesive 10 and an optical fiber fixing plate 11. It was fixed to -1 or 8-2. The V-groove type optical fiber holding housings 8-1, 8-2, the V-groove substrate 9, and the optical fiber fixing plate 11 were made of Pyrex glass. V-groove type optical fiber holding housing 8-
Adhesive reservoir grooves 15-1 and 15-2 are formed on the connection surfaces 12-1 and 12-2 of 1 or 8-2.

Reference numerals 13-1 and 13-2 indicate ferrules used as optical fiber holding casings (Pr-doped In-fluoride fiber 1 and silica-based fiber 2 are adhesive 10 (acrylic UV adhesive). Was used to fix the glass ferrules 13-1 and 13-2). Connection surface 14-1, 1 of ferrule 13-1 or 13-2
Adhesive reservoir grooves 16-1 and 16-2 are formed in 4-2.

In Example 2-3 of this embodiment, as shown in FIGS. 21 and 22, the epoxy adhesive layer 5 was used for the optical fiber 1.
And the connecting end faces 12-1 and 12-2 or 14-1 and 14-2 not including the connecting faces, and the silicone-based adhesive layer 7 includes the connecting end faces 1 including the connecting faces of the optical fibers 1 and 2.
V-groove type optical fiber holding housings 8-1 and 8-2 in which the optical fibers 1 and 2 are fixed in order to be provided in 2-1 and 12-2 or 14-1 and 14-2. Alternatively, the ferrules 13-1 and 13-2 are connected to the optical fibers 1 and 2 respectively.
After aligning so that the connection loss of
1 and 12-2 or 14-1 and 14-2 are brought into close contact with each other and V-groove type optical fiber holding housings 8-1 and 8-2 or ferrules 13-1 and 1 are used at the interface by using a capillary phenomenon.
It was prepared by injecting the epoxy ultraviolet curing adhesive 5 and the silicone ultraviolet curing adhesive 7 from the side of 3-2.
The epoxy-based UV-curing adhesive 5 and the silicone-based UV-curing adhesive 7 can be easily separated by the adhesive reservoir grooves 15-1, 15-2 or 16-1, 16-2.

By using the groove for accumulating the adhesive used in Example 2-3 of the present embodiment, the epoxy adhesive layer 5 can be connected to the connection end faces 12-1 and 12-1 which do not include the connection face of the optical fibers 1 and 2.
2-2 or 14-1 and 14-2 is provided with a silicone-based adhesive layer 7 and a connection end surface 12 including a connection surface between the optical fibers 1 and 2.
It was also found that the connection structure provided in -1 and 12-2 or 14-1 and 14-2 can be realized more reliably than in the embodiment 2-2 (in the embodiment 2-2, the connecting portion 5 is used).
From the excellent result that 32 good products were produced during the production of one, and 95 good connection products were produced during the production of 95 connection portions in the embodiment 2-3).

The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 14 respectively.
Θ ₁ = 4 [deg] with respect to the vertical axes of −1 and 14-2,
It was held at θ ₂ = 4.1 [deg]. This connection (when using the V-groove type optical fiber holding casing 8 and the ferrule 1
3), the connection loss between the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 0.13.
I was able to connect at less than dB. However, the splice loss is that there is no absorption of Er ions in the Er-doped In-based fluoride fiber 1,
It was measured at 1.3 μm.

The return loss measured from the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 6 each.
It was 0 dB or more (both when the V-groove type optical fiber holding housing 8 was used and when the ferrule 13 was used) (a commercially available return loss measuring instrument was used for measurement, measurement wavelength was 1.3 μm, The measuring device cannot measure a return loss of 60 dB or more, and this connection shows a high-performance low reflection characteristic higher than the measuring range of the measuring device).

Further, the connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2 are provided.
The angles of -1, 14-2 with respect to the vertical axis are [θ ₁ = 5
Even when [deg] or θ ₁ = 6 [deg]] is set, the connection loss between the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 0.115 dB (measurement wavelength 1.
3 μm), and the return loss measured from the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 60 each.
It was above dB. However, the angles of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of the respective connection end faces 12-1, 12-2 or 14-1, 14-2 are [θ
₁ = 3 deg]], the connection loss between the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 0.1d.
Although it was B (measurement wavelength 1.2 μm), the return loss measured from the Er-doped In-based fluoride fiber 1 side was 57 d.
It was B.

As a result, in order to connect the In-based fluoride fiber and the silica-based fiber with low loss and low reflection (reflection loss of 60 dB or more), the In-based fluoride fiber should be connected to the vertical axis of the connecting end face. It was found that an angle of 3 [deg] or more is required.

In the above description, the Er-doped In-based fluoride fiber is used. However, other Zr-based fluoride fibers, telluride-based fibers, chalcogenide-based fibers (rare earth elements Er, Pr, Tm, etc. are added respectively). The same good connection as above could be realized by setting the angle θ ₁ to Zr-based fluoride fiber 3 degrees or more, telluride-based fiber 8 degrees or more, and chalcogenide-based fiber 8 degrees or more.

Further, by the connection method shown in the above-mentioned Embodiments 2-1 to 2-3, silica type fibers were connected to both ends of the Pr-doped In type fluoride fiber to construct the optical fiber amplifier shown in FIG. Reference numerals 17-1 and 17-2 are pumping light source units that generate pumping light to the optical fiber 1, and are Nd-YLF lasers (each of which has an oscillation wavelength of 1.047 μm) as pumping light sources for the Pr-doped In-based fluoride fiber 1. Output of 500 mW) was used. Reference numerals 18-1 and 18-2 are multiplexing sections for multiplexing the signal light and the pumping light generated at 17-1 and 17-2, and 19-1 and 19-2 are for suppressing oscillation of the optical amplifier. It is an optical isolator. Also, 20-1, 2
As the connecting portion of 0-2, the connecting portions of Examples 2-1 to 2-3 of this embodiment (all implementations shown in FIGS. 17 to 22) were applied. Optical fiber 1 and silica fiber and connecting end face 12
The angles of -1, 12-2 or 14-1, 14-2 with respect to the vertical axis are θ ₁ = 4 [deg], θ ₂ = 4.1 [de]
g].

By using the connection method shown in the embodiment examples 2-1 to 2-3, the signal gain of the optical fiber amplifier is 30d.
While achieving B or higher, no ghost was generated in the optical fiber amplifier. Further, the life of the optical fiber amplifier configured using the conventional technology (conventional technology 2, 3, 4, 5) (measured by operating with a signal gain of 33 dB at 1.30 μm) was 400 hr at the maximum. The life of the optical fiber amplifier to which the connection parts (all shown in FIGS. 17 to 22) of the present embodiment examples 2-1 to 2-3 are applied is 5000 h.
By confirming that r or more and using the second invention, as in the first invention, the prior art (conventional examples 2, 3,
It was possible to solve the problem that the optical adhesive deteriorated and the connection portion was broken, which could not be solved in 4, 5), and it was possible to construct a reliable optical fiber amplifier using a non-silica fiber.

17 and 2-2 of the embodiment 2-1.
19, 2-3 of FIG. 21, a V-groove type optical fiber holding casing 8, FIGS. 18 and 2-2 of FIGS.
Although the ferrule 13 was used in FIG. 22 of -3, it was found by the actual work that the connection part using the ferrule 13 has a characteristic that the connection part manufacturing time can be shortened (V
Groove type optical fiber holding housing-fabrication time: 45 minutes, ferrule-fabrication time: 10 minutes). This is because when the V-groove type optical fiber holding casing 8 is manufactured, each optical fiber 1 or 2 is manufactured.
Is prepared by positioning it with the V-groove substrate 9 and fixing it to the V-groove type optical fiber holding housing 8 with the adhesive 10 and the optical fiber fixing plate 11, whereas the ferrule 13 has the optical fiber 1 or 2 Is achieved by a very simple operation of passing the fiber through the hole of the ferrule 13 and fixing it with the adhesive 10.

Further, FIG. 23 shows the connection loss of the embodiment examples 2-1 to 2-3 (FIGS. 17 to 22 and the change of the connection loss of the connection portions of the embodiment examples 1-1 to 1-4 in FIG. 23). The characteristic is shown in the figure, and the number of samples of the connection portion of this embodiment example 2-1 is 1
Characteristic of 0 (5 in FIG. 17 and 5 in FIG. 18 with the worst fluctuation)
-24 samples (6 in FIG. 19, FIG. 2)
(6 of 0, 6 of FIG. 21, 6 of FIG. 22)
The characteristics of the sample having the worst fluctuation, the number of samples of the connection portion of the embodiment examples 1-1 and 1-2 is 20 (1 in FIG. 8).
0, 10 in FIG. 9) with the worst variation, 20 samples (5 in FIG. 10, FIG. 10) 11 characteristics, 5 characteristics shown in FIG. 12, 5 characteristics shown in FIG. 13, and those having the worst fluctuation. As the fiber 1, a Pr-doped In-based fluoride fiber (glass composition: I
_{nF 3 -GaF 3 -ZnF 2 -PbF 2} -BaF 2 -S
rF ₂ -YF ₃ -NaF, core refractive index: 1.65, mode field radius: 4.5 μm, coating: UV resin, Pr
(Addition concentration is 1000 ppm), as the fiber 2, a silica fiber (core refractive index is ~ 1.5, mode field radius is 4.5 μm, coating is UV resin), θ _{1 with} respect to the vertical axis of the connection end face is 3 [deg]. , Θ ₂ is 3.1 [de
g]. From the same characteristics, it was found that the connecting portions of the embodiment examples 2-2 and 2-3 can realize the connecting portions having excellent temperature characteristics and thermal stability.

Further, in the above-described embodiment, the optical fiber holding housing 8 and the ferrule 13 are made of glass, but the same results are obtained by using plastic.

(Embodiment 3) Tables 2 and 3 collectively show Embodiment 3 of the present invention.

[0147]

[Table 2]

[0148]

[Table 3]

The non-quartz fiber 1 includes: Telluride glass fiber (indicated as non-quartz fiber A in Table 2) Glass composition: TeO ₂ —ZnO—Na ₂ O, core refractive index: 2.1, mode field radius: 3 μm, coating: U
V resin 2. Zr-based fluoride fiber (indicated as non-silica fiber B in Table 2) Glass composition: ZrF ₄ —BaF ₂ —LaF ₃ —YF ₃ —
2. AlF ₃ -LiF-NaF, core refractive index: 1.55, mode field radius 4 μm, coating: UV resin 3. In-based fluoride fiber (indicated as non-silica-based fiber C in Table 2) Glass composition: InF ₃ —GaF ₃ —ZnF ₂ —PbF ₂
-BaF ₂ -SrF ₂ -YF ₃ -NaF, core refractive index 1.65, the mode field radius 4.5 [mu] m, coating: U
V resin 4. Chalcogenide glass fiber (indicated as non-quartz fiber D in Table 2) Glass composition: As-S, core refractive index: 2.4, mode field radius: 3 μm, coated UV resin was used.

The non-silica fibers A, B, C,
In D, Er as a rare earth element (addition concentration 1000 pp
m), Pr (addition concentration 500 ppm), Tm (addition concentration 2000 ppm), Ho (addition concentration 1000 ppm),
Yb (addition concentration of 500 ppm), Tb (addition concentration of 20 ppm)
00ppm), Nd (addition concentration 1000ppm), Eu
(Addition concentration 2000 ppm) was added and those not added. In addition, the mode field radius of the silica-based fiber to be connected was the same as that of each of the above-mentioned non-silica-based fibers (refractive index was 1.5), and the connection mode adopted any one of the first to sixth embodiments.

As shown in Tables 2 and 3, by using the splicing method of the present invention, non-silica fibers could be spliced with low loss and low reflection. Incidentally, Table 2 and Table 3, a low reflection has shown an example of (return loss 60dB or higher), in the above Zr-based fluoride fiber at θ ₁ <3 [deg], in the above-In-based fluoride fiber theta ₁ < 4 [deg], θ ₁ <8 [deg] in the above chalcogenide glass fiber
It was confirmed that the reflection attenuation amount of 60 dB or more cannot be achieved with g], and that an angle θ ₁ larger than this value is necessary to realize the reflection attenuation amount of 60 dB or more.

Further, the embodiment examples 1-1 to 1-4, 2-1
The optical fiber amplifier shown in FIG. 14A was configured by using the connections shown in FIGS. Reference numerals 17-1 and 17-2
Is a pumping light source unit for generating pumping light to the optical fiber 1, and P
As an excitation light source for the r-doped In-based fluoride fiber 1, an Nd-YLF laser (each output is 500 mW) having an oscillation wavelength of 1.047 μm was used. Reference numerals 18-1 and 18-2 are multiplexers that combine the signal light and the pumping light generated in 17-1 and 17-2, and 19-1 and 19-2 are optical isolators for suppressing oscillation of the optical amplifier. Is. A Pr-doped fiber was used as the optical fiber of reference numeral 1. The signal gain of the optical fiber amplifier was 30 dB or more, and no ghost was generated in the optical fiber amplifier. Also, as shown in the table, it was confirmed that the connection was for a practical optical fiber amplifier with no life problem.

(Embodiment 4) In Embodiments 1 and 2 described above, the connection between the non-silica fiber and the silica fiber has been described. However, in Embodiment 8, between the non-silica fibers made of two different glasses. The connection result of will be described.
As the non-silica fibers 1 and 2 used, any of the non-silica fibers A, B, C, and D described in the third embodiment was used. The rare earth element used was one containing Er. The results are shown in Table 4.

[0154]

[Table 4]

As shown in Table 4, by using the splicing method of the present invention, non-silica fibers were spliced with low loss and low reflection.

From the results of the above-mentioned fourth embodiment, the present invention is very useful for the connection between the non-silica fiber and the silica fiber and the non-silica fiber made of two different glasses with low loss and low reflection connection. It was confirmed to be effective. Further, an optical fiber amplifier is constituted by the amplifier fiber using the connecting portion of this embodiment. However, as the rare earth element, Er was used, and as shown in Table 4, it was confirmed that the connecting portion was for a practical optical fiber amplifier with no life problem.

(Fifth Embodiment) A fifth embodiment will be described with reference to FIGS. 24 to 27. In this embodiment, the connection surfaces 12-1 and 12-2 of the V-groove type optical fiber holding housing 8-1 or 8-2 are the same as those in the embodiments 1-4 and 2-3.
Adhesive reservoir grooves 15-1 and 15-2 are provided on both sides of the ferrule 13-1 or the connecting surface 14-1 of the ferrule 13-2.
2 is a connection portion that uses the adhesive reservoir grooves 16-1 and 16-2 for both of them, but in the present embodiment example, the connection surface 12- of the V-groove type optical fiber holding housing 8-1 or 8-2 is used. 1,12-2
The adhesive reservoir groove 15 was formed on one side, and the adhesive reservoir groove 16 was formed on one of the connecting surfaces 14-1 and 14-2 of the ferrule 13-1 or 13-2.

The optical fiber indicated by reference numeral 1 is Er-doped I
n-based fluoride fiber (glass composition: InF ₃ -GaF
_{3 -ZnF 2 -PbF 2 -BaF 2 -SrF} 2 -YF 3
-NaF, core refractive index: 1.65, mode field radius: 4.5 μm, coated UV resin, Er addition concentration: 100
0 ppm), 2 is a silica-based fiber (core refractive index: up to 1.
5, mode field radius: 4.5 μm, coating: UV resin), 8-1 and 8-2 are V-groove type optical fiber holding casings for holding the ends of the optical fibers 1 or 2, respectively. The fiber 1 or 2 was positioned by the V-groove substrate 9 and fixed to the V-groove type optical fiber holding housing 8-1 or 8-2 by the adhesive 10 and the optical fiber fixing plate 11. The V-groove type optical fiber holding housings 8-1, 8-2, the V-groove substrate 9, and the optical fiber fixing plate 11 were made of Pyrex glass. V-groove type optical fiber holding housing 8-
The connection surface 12-1 of No. 1 is processed with the adhesive reservoir groove 15.

Further, reference numeral 13 in FIGS.
Reference numerals -1, 13-2 represent ferrules used as optical fiber holding housings (Er-doped In-fluoride fiber 1 and quartz-based fiber 2 are made of glass using an adhesive 10 (using an acrylic UV adhesive). Ferrules 13-1, 13-
Fixed to 2.) Connection surface 14-1 of ferrule 13-1
A groove 16 for accumulating an adhesive is processed in the.

24 and 25 of this embodiment, the adhesive layer 5 is provided only on the connection end faces 12-1 and 12-2 or 14-1 and 14-2 not including the connection faces of the optical fibers 1 and 2. Therefore, the V-groove type optical fiber holding housings 8-1, 8-2 or the ferrule 13-
1, 13-2 are aligned so that the connection loss between the optical fibers 1 and 2 is minimized, and then the connection end faces 12-1 and 12-2 or 14-1 and 14-2 are brought into close contact with each other, and a capillary is attached to the interface. Using the phenomenon, the ultraviolet curing adhesive 5 was injected from the side surface of the V-groove type optical fiber holding housings 8-1, 8-2 or the ferrules 13-1, 13-2. The adhesive 5 is a groove 15 for storing the adhesive.
Alternatively, 16 prevented its penetration.

26 and 27, the epoxy adhesive layer 5 is provided only on the connection end faces 12-1 and 12-2 or 14-1 and 14-2 not including the connection faces of the optical fibers 1 and 2. The silicone-based adhesive layer 7 is connected to the connection end faces 12-1 and 12-2 or 14 including the connection faces of the optical fibers 1 and 2.
-1 and 14-2, the V-groove type optical fiber holding housings 8-1 and 8-2 or the ferrules 13-1 and 13-2 to which the optical fibers 1 and 2 are fixed are connected to the optical fibers 1 and 2. After alignment so that the loss is minimized, the connection end faces 12-1 and 12-2 or 14-1 and 14-2 are brought into close contact with each other, and the V-groove type optical fiber holding housing 8 is made to use the capillary phenomenon at the interface. -1, 8-2 or ferrules 13-1, 13-2
It was prepared by injecting the epoxy-based UV-curing adhesive 5 and the silicone-based UV-curing adhesive 7 from the side surface of. The epoxy-based UV-curing adhesive 5 and the silicone-based UV-curing adhesive 7 were easily separated by the adhesive reservoir grooves 15 or 16 in the area where they were injected.

The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 14 respectively.
Θ ₁ = 4 [deg] with respect to the vertical axes of −1 and 14-2,
It was held at θ ₂ = 4.1 [deg]. This connection (when using the V-groove type optical fiber holding casing 8 and the ferrule 1
3), the connection loss between the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 0.15.
Connection was possible at 5 dB or less. However, the splice loss was measured at 1.3 μm where Er ion was not absorbed by the Er-doped In-based fluoride fiber 1.

The return loss measured from the Er-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 6 each.
It was 0 dB or more (both when the V-groove type optical fiber holding housing 8 was used and when the ferrule 13 was used) (a commercially available return loss measuring instrument was used for measurement, measurement wavelength was 1.3 μm, The measuring device cannot measure a return loss of 60 dB or more, and this connection shows a high-performance low reflection characteristic higher than the measuring range of the measuring device).

In the above description, the Er-doped In-based fluoride fiber has been used, but other Zr-based fluoride fibers, telluride-based fibers, chalcogenide-based fibers (respective rare earth elements Er, Pr, Tm, etc. are used). (Including the added ones), the same good connection as above was realized by setting the angle θ ₁ to Zr-based fluoride fiber 3 degrees or more, telluride-based fiber 8 degrees or more, and chalcogenide-based fiber 8 degrees or more. .

Further, by the connection method shown in FIGS. 24 to 27, silica type fibers were connected to both ends of the Pr-doped In type fluoride fiber to form the optical fiber amplifier shown in FIG. Reference numerals 17-1 and 17-2 are pumping light source units for generating pumping light to the optical fiber 1, which are Nd-YLF lasers having an oscillation wavelength of 1.047 μm (each output) as pumping light sources for the Pr-doped In-based fluoride fiber 1. Of 500 mW) was used. 18-1, 18-2 are signal light and 17-1, 17-2
, 19-1, 19 for combining the pumping light generated in
Reference numeral -2 is an optical isolator for suppressing oscillation of the optical amplifier. Further, as the connecting portions of 20-1 and 20-2, the connecting portions of the present embodiment example (all implementations shown in FIGS. 24 to 27) are applied. The optical fiber 1 and the silica-based fiber and the connection end faces 12-1, 12-2 or 14-1, 14-
The angle of 2 with respect to the vertical axis is θ ₁ = 4 [deg], θ ₂ =
It was set to 4.1 [deg]. By using the connection part shown in FIGS. 24 to 27, a signal gain of 30 dB or more was realized in the optical fiber amplifier and no ghost was generated in the optical fiber amplifier. Further, the life of the optical fiber amplifier configured using the conventional technology (conventional technology 2, 3, 4, 5) (measured by operating with a signal gain of 33 dB at 1.30 μm) was 400 hr at the maximum. The life of the optical fiber amplifier to which the connection portions (all shown in FIGS. 17 to 22) of the present embodiment examples 2-1 to 2-3 are applied is 200.
After confirming that it is 0 hr or more, the conventional technique (conventional example 2,
It was possible to solve the problem that the optical adhesive was deteriorated and the connection portion was broken, which could not be solved by No. 3, 4, 5), and it was possible to construct a reliable optical fiber amplifier using a non-silica fiber.

In the above embodiment, the optical fiber holding housing 8 and the ferrule 13 are made of glass, but the same results are obtained by using plastic.

(Embodiment 6) Embodiment 6 will be described with reference to FIGS. 28 and 29. In this embodiment, the connection surfaces 12-1 and 12-2 of the V-groove type optical fiber holding housing 8-1 or 8-2 are the same as those in the embodiments 1-4 and 2-3.
The line-shaped adhesive reservoir grooves 15-1 and 15-2 are provided on the connecting surfaces 14-1 and 1-2 of the ferrule 13-1 or 13-2.
4-2 is a connection portion using the adhesive reservoir grooves 16-1 and 16-2, but in the present embodiment example, the connection surface 12- of the V-groove type optical fiber holding housing 8-1 or 8-2 is used. An adhesive reservoir groove 15 is provided on one of the first and the second portions 12-2, and the concentric adhesive reservoir groove 2 is provided.
The connection with the one having 1 was implemented.

The optical fiber denoted by reference numeral 1 is Pr-doped I
n-based fluoride fiber (glass composition: InF ₃ -GaF
_{3 -ZnF 2 -PbF 2 -BaF 2 -SrF} 2 -YF 3
-NaF, core refractive index: 1.65, mode field radius: 4.5 μm, coating: UV resin, Pr addition concentration: 10
00 ppm), 2 is a silica fiber (core refractive index: ~
1.5, radius of mode field: 4.5 μm, coating: U
V resin), 13-1 and 13-2 represent ferrules used as optical fiber holding casings (Pr-doped In-fluoride fiber 1 and quartz-based fiber 2 are adhesive 10 (using an acrylic UV adhesive)). Using the glass ferrule 1
3-1 and 13-2). The connection surface 14-1 of the ferrule 13-1 is provided with a concentric adhesive reservoir groove 21.

In the configuration of this embodiment shown in FIG. 28, the adhesive layer 5 is used as the connection end face 14 not including the connection face of the optical fibers 1 and 2.
-1 and 14-2, the ferrules 13-1 and 13-2 with the optical fibers 1 and 2 fixed are provided on the optical fiber 1.
After aligning so that the connection loss of 2 and 2 becomes the minimum, the connection end face 1
4-1 and 14-2 were brought into close contact with each other, and the ultraviolet curing adhesive 5 was injected into the interface from the side surfaces of the ferrules 13-1 and 13-2 by using a capillary phenomenon. The adhesive 5 was prevented from penetrating by the concentric adhesive reservoir groove 21.

In the connection shown in FIG. 28, the epoxy adhesive layer 5 is used as the connection end surface 14-1 not including the connection surface between the optical fibers 1 and 2.
And 14-2 only. In addition, the silicone-based adhesive layer 7
A connection end face 14-1 including a connection face of the optical fibers 1 and 2
And 14-2, first, a silicone-based adhesive layer 7 is applied to the connection end surfaces 14-1 and 14-2 including the connection surfaces of the optical fibers 1 and 2 to connect the optical fibers 1 and 2 with each other. The connection end faces 14-1 and 14 so that
-2, and after aligning and aligning, the connection end faces 14-1 and 14-2, which do not include the connection face of the optical fibers 1 and 2, are epoxy-treated from the side faces of the ferrules 13-1 and 13-2 by using a capillary phenomenon. It was manufactured by injecting the system ultraviolet curing adhesive 5. The epoxy-based UV-curing adhesive 5 and the silicone-based UV-curing adhesive 7 were easily separated from each other by the adhesive reservoir groove 21.

The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 14 respectively.
With respect to the vertical axes of -1, 14-2, θ1 = 4 [deg],
It was held at θ ₂ = 4.1 [deg]. This connection (when using the V-groove type optical fiber holding casing 8 and the ferrule 1
3) is used, the connection loss between the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 is 0.11.
Connection was possible at 1 dB or less. However, the splice loss was measured at 1.2 μm where there was no absorption of Er ions in the Pr-doped In-based fluoride fiber 1.

The return loss measured from the Pr-doped In-based fluoride fiber 1 and the silica-based fiber 2 was 6 each.
It was 0 dB or more (both when the V-groove type optical fiber holding housing 8 was used and when the ferrule 13 was used) (a commercially available return loss measuring instrument was used for measurement, the measurement wavelength was 1.2 μm, The measuring device cannot measure a return loss of 60 dB or more, and this connection shows a high-performance low reflection characteristic higher than the measuring range of the measuring device).

In the above description, the Pr-doped In-based fluoride fiber is used. However, other Zr-based fluoride fiber, telluride-based fiber, chalcogenide-based fiber (rare earth elements Er, Pr, Tm, etc. are added, respectively). The same good connection as above was realized by setting the angle θ ₁ to Zr-based fluoride fiber 3 ° or more, telluride-based fiber 8 ° or more, and chalcogenide-based fiber 8 ° or more. .

Further, by the connection method shown in FIGS. 28 and 29, a silica fiber was connected to both ends of the Pr-doped In fluoride glass fiber to form the optical fiber amplifier shown in FIG. Reference numerals 17-1 and 17-2 are pumping light source units for generating pumping light to the optical fiber 1, which are Nd-YLF lasers having an oscillation wavelength of 1.047 μm (each output) as pumping light sources for the Pr-doped In-based fluoride fiber 1. Of 500 mW) was used. 18-1, 18-2 are signal light and 17-1, 17-2
, 19-1, 19 for combining the pumping light generated in
Reference numeral -2 is an optical isolator for suppressing oscillation of the optical amplifier. Further, as the connecting portions of 20-1 and 20-2, the connecting portions of the present embodiment example (all implementations shown in FIGS. 28 and 29) were applied. The angle between the optical fiber 1 and the silica-based fiber and the connection end faces 14-1 and 14-2 with respect to the vertical axis is θ.
₁ = 4 [deg] and θ ₂ = 4.1 [deg].

By using the connection portions shown in FIGS. 28 and 29, a signal gain of 30 dB or more was realized in the optical fiber amplifier and no ghost was generated in the optical fiber amplifier. In addition, the related art (conventional examples 2, 3,
4, 5) Life of an optical fiber amplifier (measured by operating with a signal gain of 33 dB at 1.30 μm)
Was 400 hours at maximum, while it was confirmed that the life of the optical fiber amplifier to which the present embodiment example was applied was 2000 hours or more, and the prior art (conventional examples 2, 3, 4, 5)
The problem that the optical adhesive deteriorates and the connection portion is broken, which could not be solved by the method described above, can be solved, and a reliable optical fiber amplifier using a non-silica fiber can be constructed.

In the above-described embodiment, the material of the ferrule 13 is made of glass, but the same result is obtained even if the material of plastic is used. Further, in this embodiment, the concentric adhesive reservoir groove 21 is provided on the connection end face of the ferrule 13, but the concentric adhesive reservoir groove 21 is provided on the connection end face of the V-groove type optical fiber holding housing 8. It is natural that the same result can be obtained by providing.

In the above-mentioned first to fourth embodiments, the fiber to which the rare earth element is added has been described. However, even if Cr, Ti or Ni is added as a transition metal in addition to the rare earth element, the present invention is effective. there were. Furthermore, Zr shown in the embodiment example
It is obvious that it is also effective for compositions other than the glass composition of the system fluoride fiber, the In system fluoride fiber, the chalcogenide glass fiber, and the telluride glass fiber. Further, the embodiment has been shown with respect to the two shapes of the adhesive reservoir groove, that is, the linear shape and the concentric shape, but the purpose of this groove is to "include the adhesive layer 5 as the connecting surface of the optical fibers 1 and 2". No connecting end face 12-1 and 12-2 or 14-1
And 14-2 only "or" the epoxy adhesive layer 5 does not include the connection surface between the optical fibers 1 and 2
-1 and 12-2 or 14-1 and 14-2 only, and a silicone-based adhesive layer is provided on the connection end faces 12-1 and 12-2 or 14-1 and 14- including the connection faces of the optical fibers 1 and 2. It is for the purpose of easily realizing "to be provided in 2" and the shape may be another shape as long as this purpose is satisfied. Further, although the epoxy adhesive layer is used as the adhesive layer 5, the same result can be obtained with other adhesive such as acrylic adhesive.

[0178]

As described above, according to the present invention,
The connection end face of the non-silica fiber and the connection end face of the silica fiber are connected so that no optical adhesive is present, or the connection end face of the non-silica fiber and the connection end face of the silica fiber are bonded with a silicone optical adhesive. To provide an optical fiber connection part for connecting a non-silica optical fiber and a silica fiber with low loss and low reflection, by preventing damage to the connection part due to deterioration of an optical adhesive by connecting the optical fiber and the silica fiber. This makes it possible to construct a highly reliable optical fiber amplifier using the optical fiber connection section.

[Brief description of drawings]

FIG. 1 is a schematic side view for explaining a schematic configuration of an optical fiber connection section according to the present invention.

FIG. 2 is a schematic side view for explaining a schematic configuration of an optical fiber connection portion according to the present invention, in which an adhesive reservoir groove is not formed on a connection surface of an optical fiber holding casing. Indicates.

FIG. 3 is a schematic side view for explaining a schematic configuration of an optical fiber connection portion according to the present invention, in which an adhesive reservoir groove is formed on a connection surface of an optical fiber holding casing. Indicates.

FIG. 4 is a view for explaining the shape of an adhesive reservoir groove formed on an adhesive surface of an optical fiber holding casing applied to an optical fiber connecting portion of the present invention, in which (a) is an optical fiber. A side view of the holding housing, (b) is a front view seen from the connection end face of the optical fiber holding housing corresponding to the side view of (a), and a line-shaped bonding applied to the configuration of FIG. 3. FIG. 6C shows a groove for storing the agent, and FIG. 7C is a front view seen from the connection end face of the optical fiber holding casing corresponding to the side view of FIG. 3 shows the formed adhesive reservoir groove.

FIG. 5 is a schematic side view for explaining a schematic configuration of an optical fiber connection section according to the present invention.

FIG. 6 is a schematic side view for explaining a schematic configuration of an optical fiber connection section according to the present invention.

FIG. 7 is a schematic side view for explaining a schematic configuration of an optical fiber connection section according to the present invention.

8A and 8B show a schematic configuration of an optical fiber connecting portion according to the present invention, FIG. 8A is a side view showing the entire optical fiber connecting portion, and FIG. 8B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

9A and 9B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 9A is a side view showing the entire optical fiber connecting portion, and FIG. 9B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

10A and 10B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 10A is a side view showing the entire optical fiber connecting portion, and FIG. 10B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

11A and 11B show a schematic configuration of an optical fiber connecting portion according to the present invention, FIG. 11A is a side view showing the entire optical fiber connecting portion, and FIG. 11B is a side view showing a connecting end surface of an optical fiber holding housing. It is a figure.

12A and 12B show a schematic configuration of an optical fiber connecting portion according to the present invention, FIG. 12A is a side view showing the entire optical fiber connecting portion, and FIG. 12B is a side view showing a connecting end surface of an optical fiber holding housing. It is a figure.

13A and 13B show a schematic configuration of an optical fiber connecting portion according to the present invention, FIG. 13A is a side view showing the entire optical fiber connecting portion, and FIG. 13B is a side view showing a connecting end surface of an optical fiber holding housing. It is a figure.

14A is a schematic diagram showing a configuration of an optical amplifier according to the present invention, and FIG. 14B is a graph showing characteristics of the optical amplifier of FIG. 14A.

FIG. 15 is a graph showing the relationship between signal gain and time when the optical fiber connection section according to the present invention is applied.

FIG. 16 is a graph showing the relationship between the temperature, loss, and time of the connection part when the optical fiber connection part according to the present invention is applied.

17A and 17B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 17A is a side view showing the entire optical fiber connecting portion, and FIG. 17B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

18A and 18B show a schematic configuration of an optical fiber connecting portion according to the present invention, in which FIG. 18A is a side view showing the entire optical fiber connecting portion, and FIG. 18B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

19A and 19B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 19A is a side view showing the entire optical fiber connecting portion, and FIG. 19B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

20A and 20B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 20A is a side view showing the entire optical fiber connecting portion, and FIG. 20B is a side view showing a connecting end surface of an optical fiber holding housing. It is a figure.

21A and 21B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 21A is a side view showing the entire optical fiber connecting portion, and FIG. 21B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

22A and 22B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 22A is a side view showing the entire optical fiber connecting portion, and FIG. 22B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

FIG. 23 is a graph showing the relationship between the temperature, loss, and time of the connection section when the optical fiber connection section according to the present invention is applied.

24A and 24B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 24A is a side view showing the entire optical fiber connecting portion, and FIG. 24B is a side view showing a connecting end surface of an optical fiber holding housing. It is a figure.

25A and 25B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 25A is a side view showing the entire optical fiber connecting portion, and FIG. 25B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

26A and 26B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 26A is a side view showing the entire optical fiber connecting portion, and FIG. 26B is a side view showing a connecting end surface of an optical fiber holding casing. It is a figure.

27A and 27B show a schematic configuration of an optical fiber connecting portion according to the present invention, FIG. 27A is a side view showing the entire optical fiber connecting portion, and FIG. 27B is a side view showing a connecting end face of an optical fiber holding housing. It is a figure.

28A and 28B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 28A is a side view showing the entire optical fiber connecting portion, and FIG. 28B is a side view showing a connecting end surface of an optical fiber holding casing. It is a figure.

29A and 29B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 29A is a side view showing the entire optical fiber connecting portion, and FIG. 29B is a side view showing a connecting end surface of an optical fiber holding casing. It is a figure.

FIG. 30 is a schematic side view for explaining a conventional connecting method between a non-quartz fiber and a quartz fiber, where (a) shows a case where an optical adhesive is not present on the fiber connecting surface (conventional example 1 and And (b) show the case where the optical adhesive is present on the fiber connecting surface (referred to as Conventional Example 2).

FIG. 31 is a schematic diagram for explaining generation of multiple reflected light by a conventional connection method.

FIG. 32 is a perspective view for explaining a conventional connection method.

FIG. 33 is a side view for explaining a conventional connecting method.

FIG. 34 is a side view for explaining a conventional connecting method.

FIG. 35 is a perspective view for explaining a conventional connection method.

FIG. 36 is a side view for explaining a conventional connecting method.

FIG. 37 is a side view for explaining a conventional connecting method.

[Explanation of symbols]

1 Non-Quartz Fiber 2 Quartz Fiber (Non-Quartz Fiber Made of Glass Different from Non-Quartz Fiber 1 in Embodiment 4) 3-1 and 3-2 Light for Holding End of Optical Fiber 1 or 2 Fiber holding housings 4-1 and 4-2 Connection end face 5 of optical fiber holding housings 3-1 and 3-2 Adhesive (adhesive layer) or optical adhesive (optical adhesive layer) 6-1, 6-2 Adhesion Agent reservoir groove 7 Silicone adhesive (silicone adhesive layer) 8-1, 8-2 V-groove type optical fiber holding housing 9-1, 9-2 V-groove substrate 10 Adhesive 11-1, 11-2 Optical fiber fixing plates 12-1, 12-2 V-groove type optical fiber holding housing 8-
1, 8-2 connection end faces 13-1, 13-2 ferrules 14-1, 14-2 ferrules 12-1, 12-2 connection end faces 15-1, 15-2 V-groove type optical fiber holding housing 8 −
Adhesive reservoir grooves 16-1, 16-2 formed on the connection end faces 12-1, 12-2 of 1, 8-2, the connection end faces 14-1, 14-2 of the ferrules 12-1, 12-2. Adhesive reservoir grooves 17-1 and 17-2 formed on the pumping light sources 18-1 and 18-8 Multiplexers 19-1 and 19-2 Optical isolators 20-1 and 20-2 21 Concentric adhesive reservoir groove 22 Dielectric film

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Fujiura 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) References JP-A-59-223406 (JP, A) Special features Kaihei 9-211250 (JP, A) JP 8-136764 (JP, A) JP 8-122561 (JP, A) JP 5-60941 (JP, A) (58) Fields investigated ( Int.Cl. ⁷ , DB name) G02B 6/255

Claims (13)

(57) [Claims] 1. A first optical fiber and a second optical fiber, at least one of which is a non-quartz fiber for optical amplification, and a first optical fiber holding casing for holding an end portion of the first optical fiber. A body and a second optical fiber holding housing holding an end portion of the second optical fiber, wherein the first optical fiber and the second optical fiber have different glass compositions. The end surface of the first optical fiber holding housing and the end surface of the first optical fiber, and the end surface of the second optical fiber holding housing and the end surface of the second optical fiber are on the same plane. And is aligned and arranged so that the optical axis of the first optical fiber and the optical axis of the second optical fiber coincide with each other, and the first optical fiber holding housing and the second optical fiber holding housing In a partial area of at least one end face of the optical fiber holding housing Is provided with a groove portion located in the vicinity of the end portion of the first or second optical fiber, and the end surfaces of the first and second optical fiber holding casings are provided with the first and second groove portions by the groove portion. It is divided into a first region on the second optical fiber side and a second region outside the first region, and only the second region of the first and second regions is made of an adhesive. An adhesive layer is provided, and the first optical fiber holding casing and the second optical fiber holding casing are adhered by the adhesive layer to form an end face of the first optical fiber and the second optical fiber. An optical fiber connecting part, which is connected to an end face of the optical fiber. 2. The optical fiber connecting section according to claim 1, wherein the adhesive is an epoxy or acrylic adhesive. 3. The optical fiber connecting section according to claim 2, wherein the adhesive is an ultraviolet curable adhesive. 4. A first optical fiber and a second optical fiber, at least one of which is a non-quartz fiber for optical amplification, and a first optical fiber holding casing which holds an end portion of the first optical fiber. A body and a second optical fiber holding housing holding an end portion of the second optical fiber, wherein the first optical fiber and the second optical fiber have different glass compositions. The end surface of the first optical fiber holding housing and the end surface of the first optical fiber, and the end surface of the second optical fiber holding housing and the end surface of the second optical fiber are on the same plane. And is aligned and arranged so that the optical axis of the first optical fiber and the optical axis of the second optical fiber coincide with each other, and the first optical fiber holding housing and the second optical fiber holding housing The optical fiber holding housing of is the first and second optical fibers. While being bonded by an adhesive layer provided between the end faces of the bar holding housing, the end face of the first optical fiber and the end face of the second optical fiber are bonded via an adhesive layer made of a silicone adhesive. An optical fiber connecting part characterized by being connected. 5. The optical fiber connecting section according to claim 4, wherein the silicone-based adhesive is an ultraviolet curable adhesive. 6. A first optical fiber and a second optical fiber, at least one of which is a non-quartz fiber for optical amplification, and a first optical fiber holding casing which holds an end portion of the first optical fiber. A body and a second optical fiber holding housing holding an end portion of the second optical fiber, wherein the first optical fiber and the second optical fiber have different glass compositions. The end surface of the first optical fiber holding housing and the end surface of the first optical fiber, and the end surface of the second optical fiber holding housing and the end surface of the second optical fiber are on the same plane. And arranged so that the optical axis of the first optical fiber and the optical axis of the second optical fiber are aligned with each other. Each of the end faces is close to the end faces of the first and second optical fibers. First by the side
And a second region outside the first region, wherein the first region is provided with a first adhesive layer made of a silicone-based adhesive, while the second region is not A second adhesive layer made of a silicone-based adhesive is provided, and the first optical fiber holding casing and the second optical fiber holding casing are adhered by the first and second adhesive layers, An optical fiber connection part, wherein an end surface of the first optical fiber and an end surface of the second optical fiber are connected. 7. The first region and the second region are the first or second end faces of at least one end face of the first optical fiber holding casing and the second optical fiber holding casing. The optical fiber connection part according to claim 6, wherein the optical fiber connection part is defined by a groove part provided in a region located near the end face of the optical fiber. 8. The optical fiber connection part according to claim 6, wherein the non-silicone adhesive is an epoxy or acrylic adhesive. 9. The optical fiber connection part according to claim 6, wherein the silicone adhesive and the non-silicone adhesive are both ultraviolet curable adhesives. 10. At least one of the first optical fiber and the second optical fiber is selected from the group consisting of Zr-based fluoride fibers, In-based fluoride fibers, chalcogenide-based glass fibers and tellurite glass fibers. The optical fiber splicing part according to any one of claims 1 to 9, wherein the optical fiber splicing part is a non-quartz optical fiber. 11. The core refractive index n of the first optical fiber
₁ and the core refractive index n ₂ of the second optical fiber have different values, and each of the first optical fiber and the second optical fiber has a connection between the first and second optical fibers. provided with a predetermined inclination angle theta with respect to the perpendicular plane, the inclination angle theta ₂ of the inclination angle theta ₁ and the second optical fiber of the first optical fiber satisfies the following equation Is set as follows: The tilt angle θ of the selected non-silica optical fiber
Is 3 degrees or more for Zr-based fluoride fibers, 4 degrees or more for In-based fluoride fibers, 8 degrees or more for chalcogenide-based glass fibers, and 8 degrees or more for tellurite glass fibers. The optical fiber connection part according to claim 10. 12. The optical fiber connecting section according to claim 11, wherein a rare earth element is added to the selected optical fiber. 13. An optical fiber amplifier comprising the optical fiber connection section according to any one of claims 1 to 12.