JPH11344636A - Optical fiber juncture and optical amplifier using the optical fiber juncture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to connect a non-quartz-base optical fiber and a quartz-base optical fiber with a low loss and a low reflection without breaking them by not interposing an adhesive layer consisting of an adhesive between the connecting end of the first optical fiber and the connecting end of the second optical fiber. SOLUTION: An optical adhesive is not interposed between the fiber connecting end faces of the non-quartz-base optical fiber 1 and the quartz-base optical fiber 2. Namely, the region provided with the adhesive layer 5 is restricted so that the adhesive is not spread to the region of the connecting portion between the non-quartz-base optical fiber 1 and the quartz-base optical fiber 2 and near the same. Further, grooves 6-1, 6-2 for storing the adhesive are formed on optical fiber holding casings 4-1, 4-2. The optical fiber juncture is provided with such grooves 6-1, 6-2, by which the flow of the adhesive layer forming the adhesive layer 5 pressed at the time of the tight adhesion of the connecting surface 4-1 and the connecting surface 4-2 into the connecting portion of the non-quartz-base optical fiber 1 and the quartz-base optical fiber 2 and the region corresponding near the same is prevented.

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 and the like in the field of optical communication and optical measurement, and more particularly, to connecting a silica fiber and a non-quartz fiber. Further, the present invention relates to an optical fiber connecting portion characterized in that the connecting portion has low loss and low reflection, and an optical amplifier using the optical fiber connecting portion.

[0002]

2. Description of the Related Art At present, several kinds of glass fibers have been receiving attention as amplification media for optical fiber amplifiers. For example, Zr-based or In-based fluoride fibers doped with praseodymium (element symbol: Pr), which is a rare earth element, and chalcogenide-based glass fibers have been attracting attention as amplification media for high-efficiency 1.3 μm-band optical fiber amplifiers. (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, telluride glass fiber doped with erbium (element symbol: Er) has been attracting attention (see “Mori et al.
7th Symposium / Academic Lecture (1996), 9a-KF-
4. ).) In addition, chalcogenide glass fibers and telluride glass fibers have attracted 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
pp.6876-6884, 1991 ").

Incidentally, in a 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 constitute a practical optical amplifier by adding Pr. When such a non-quartz optical fiber is actually used for amplification or nonlinear optics, it must be connected to the silica fiber with low loss and low reflection.

[0004] However, the connection between the quartz fiber and the non-silica fiber has problems to be studied as shown in the following (1) to (3). (1) Difference in softening temperature between both fibers (quartz fiber to 1
(400 degrees, non-quartz fiber <500 degrees), the conventional fusion splicing cannot be applied.

(2) Since there is no manufacturing technology for an optical connector suitable for a non-quartz fiber, the optical connector connection technology cannot be applied.

(3) Due to the reasons (1) and (2) described above, a connection method that has been used for connecting silica-based fibers cannot be applied.

Therefore, there is a need for a versatile connection technique for reliably connecting a non-quartz fiber and a silica fiber with low loss and low reflection.

FIG. 3 shows an example of a conventional connection method between a non-quartz optical fiber and a silica fiber.
This will be described with reference to FIG.

FIG. 30 is a schematic side view showing a connection between a non-quartz fiber and a quartz fiber. FIG. 30A shows a case where an optical adhesive is not interposed on the fiber connection surface (conventional example 1). (B) shows a case where an optical adhesive is interposed on the fiber connection surface (conventional example 2). In the figure, reference numeral 1 denotes a non-quartz fiber, 2 denotes a silica fiber, and 5 denotes an optical adhesive. Note that, as the optical adhesive, an epoxy-based or acrylic-based ultraviolet curable resin is usually applied.

However, in the configuration shown in FIG. 30, since the non-quartz-based optical fiber and the silica-based fiber have different core refractive indices, there is residual reflection at the connection interface, and in general, the connection has practical utility. Cannot be realized. As an exception, as will be described later, the connection between the Zr-based fluoride fiber or the In-based fluoride fiber and the quartz-based fiber is controlled 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, the silica-based fibers 2-1 and 2
-2 are connected 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 indicates reflection at the connection.

In FIG. 31, when there is residual reflection between the silica-based fibers 2-1 and 2-2 and the non-quartz-based fiber 1, the output signal has a ghost (acting as noise) caused by reflection at both connection portions. ) Occurs and the signal quality is significantly degraded. A practical reflectance of 60 dB or more is required (in the case of an optical fiber amplifier) as the residual reflectance of the connection part (see "Takei et al.," Optical Amplifier Module ",
Oki Electric Development, vol.64, No.1, pp.63-66, 1997 ”). The core refractive index of the non-quartz fiber is 1.48 to 1.55 (depending on the glass composition) of the Zr-based fiber, and 1.45 to 1.65 of the In-based fiber.
(Depending on the glass composition), chalcogenide glass fibers (glass composition As-S) to 2.4, and telluride glass fibers to 2.1. Further, the core refractive index of the quartz fiber connected to it is up to 1.50.

Therefore, Zr-based fluoride fiber, I
When an n-based fluoride fiber, a chalcogenide-based glass fiber, or a telluride glass fiber and a quartz-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,
The relationship with the residual reflectivity is that the residual reflectivity indicates a negative value, whereas the return loss indicates the absolute value of the residual reflectivity and has a positive value.) .

[0014]

(Equation 5)

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

A Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber (glass composition As-S), or a telluride glass fiber;
The amount of residual reflection from the silica-based fiber is 石英 to 35, respectively.
dB, ∞-26 dB, 13 dB, or 16 dB. In addition, regarding the Zr-based fluoride fiber and the In-based fluoride fiber, by adjusting the glass composition, the return loss can be increased (the residual reflectance is reduced).

Therefore, the connection between the Zr-based fluoride fiber or the In-based fluoride fiber and the quartz-based fiber has been limited to the case where the glass composition of the Zr-based fluoride fiber or the In-based fluoride fiber is the quartz-based fiber. The method of the prior art 2 (method of interposing an adhesive) was mainly applied so as to be precisely controlled so as to coincide with the above. In some cases, the method of Conventional Example 1 is used. However, in this method, when the non-quartz fiber 1 and the silica fiber 2 are connected, a core layer between the two fibers due to an air layer (polished and roughened) is formed at the connection interface. Caused by the incomplete contact). Therefore, low reflection cannot be realized with a high yield due to the presence of the air layer, 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. FIG. 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-quartz fiber is adjusted to be equal to the core refractive index of the silica fiber. Both fiber end faces are processed so as to be perpendicular to the central axis of the fiber.

In FIG. 32, reference numeral 8-1 denotes an optical fiber holding case for holding the non-quartz fiber 1. This optical fiber holding housing 8-1 has a U-shaped cross section, and a V-groove substrate 9-1 is provided with an adhesive 10 inside.
-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 the surface thereof. Therefore, by providing the non-quartz fiber 1 along the V-groove substrate 9-1, the positioning of the optical fiber 1 in the optical fiber holding case 8-1 is performed. 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.
1 is interposed between the adhesive 10-1 and the adhesive 10-1. Similarly, the silica fiber 2 is 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.
Adhesive 102 and optical fiber fixing plate 1
1-2, it is fixed to the optical fiber holding case 8-2.

As shown in FIG. 33, the connection between the silica fiber 2 and the non-quartz fiber 1 is performed so that the optical axes of the two fibers coincide with each other (the two optical axes are aligned). After adjusting the positions of the bodies 8-1 and 8-2, they are connected using the optical adhesive 5. In addition, as the optical adhesive 5,
Usually excellent in adhesive strength and 1.3 or 1.5 μm
An epoxy-based or acrylic-based ultraviolet curable resin having excellent transmission of band signal light is applied.

However, the method of the second conventional example shown in FIG. 33 has some problems to be solved in order to realize a connection part having excellent characteristics with good reproducibility and high yield. For example, the refractive index of the optical adhesive 5 needs to exactly match the core refractive index of the non-quartz fiber 1 and the core refractive index of the quartz fiber 2. In addition, changes in the refractive index and temperature of the optical adhesive 5,
Since there is a difference between the core refractive index / temperature change of the non-quartz fiber 1 and the core refractive index / temperature change of the quartz fiber 2, the residual reflectance may increase depending on the environmental temperature used by the main connecting part.

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-based fiber and a non-quartz-based fiber. In the method shown in this figure, a Zr-based fluoride fiber or an In-based fluoride fiber is used as the non-quartz fiber in the same manner as in the method of Conventional Example 2, and the core refractive index of the fiber matches the core refractive index of the silica fiber. Thus, precise control of the composition of the core glass can be performed. As shown in FIG. 34, in this method, optical fiber holding housings 8-1 and 8-2 holding fibers 1 and 2 are provided.
Are 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 housing 8-is set so that the optical axes of the fibers 1 and 2 coincide.
After adjusting the positions of 1, 8-2, by diagonally connecting them using the optical adhesive 5, a connection part with low reflection and low loss is realized. According to this method, it is not necessary to exactly match the refractive index of the optical adhesive 5 to the core refractive index of the non-quartz fiber 1 and the core refractive index of the silica fiber 2 as in the method of the conventional example 2, and the optical It is possible to suppress the occurrence of residual reflection caused by the difference between the refractive index / temperature change of the adhesive 5 and the core refractive index / temperature change of the non-quartz fiber 1 and the core refractive index / temperature change of the quartz fiber 2. , The connection portion can be realized with good reproducibility and high yield.

However, in the above-described methods of Conventional Examples 2 and 3, the core refractive index 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. This is a connection technology that must match the refractive index. Therefore,
The methods of Conventional Examples 2 and 3 are general-purpose methods such as 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 quartz-based fiber. It is not a technology applicable to connection.

By the way, the present inventors generally apply the present invention to a connection between a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, or a telluride glass fiber and a quartz-based fiber having an arbitrary core refractive index. Possible technologies 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 views for explaining the method of the 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-quartz fiber 1 or the quartz fiber 2
Is held by the optical fiber holding housing 8-1 or 8-2 (each optical fiber 1 or 2 is
Positioning is performed using 9-2, and the adhesives 10-1, 10-
2 and the optical fiber fixing plates 11-1 and 11-2, which are fixed to the optical fiber holding case 8-1 or 8-2). Also,
One optical fiber holding housing holding the fiber (FIG. 35)
In the optical fiber holding case 18 holding the fiber 2,
A dielectric film 22 is provided on the connection end face of 2).
As shown in FIG. 36, the connection between the silica-based fiber 2 and the non-quartz-based fiber 1 is performed so that the optical axes of the optical fibers coincide with each other (the two optical axes are aligned).
After adjusting the components 1 and 8-2, they are connected to each other using an optical adhesive (epoxy or acrylic 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 non-quartz fiber 1 or silica fiber 2
Perpendicular to the optical axis of

By the way, in 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 thickness of the dielectric film 22. That is, assuming that the core refractive index of the non-quartz fiber 1 is n ₁ and the core refractive index of the quartz fiber 2 is n ₂ , the refractive index of the optical adhesive 5 is adjusted to n ₁ , The refractive index n _f and the film thickness t _f need to satisfy the condition of the following expression (2).

[0028]

(Equation 6)

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

However, in the method of the conventional example 4, since the connection part with low reflection and low loss is formed by using the dielectric film, the refractive index of the optical adhesive 5 and the refractive index and the film thickness of the dielectric film 22 are different. It needs to be adjusted precisely. This is one of the problems to be solved for realizing a connection part having excellent characteristics with good reproducibility and high yield, similarly to the method of Conventional Example 2.

On the other hand, in the method of the conventional example 5, the connection ends of the non-quartz fiber and the silica fiber are not perpendicular but connected to each other while being inclined. That is, the inclination angle θ ₁ of the connection end face of the non-quartz optical fiber with respect to the vertical axis [unit is ra
The relationship between d] and the inclination angle θ ₂ [rad] of the connection end face of the silica-based optical fiber with respect to the vertical axis is such that 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 _2, connected so as to satisfy the "Snell's official" represented by the following formula (3). That is, the gist of the conventional example 5 proposed by the present inventors is that, in connection between cores having different refractive indices, a connection boundary surface is inclined to prevent reflection,
In addition, in order to reduce the loss, the optical axis of the fiber to be connected is inclined so as to satisfy "Snell's formula".

[0032]

(Equation 7)

However, in the connection between the silica-based fiber and the non-quartz-based fiber in which the core glass composition of the Zr-based fluoride fiber and the In-based fluoride fiber is precisely controlled so as to match the silica-based fiber, n ₁ and n 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. The theta ₁ and theta ₂ are the same angles.

FIG. 37 is a side view for explaining the method of the conventional example 5. In the drawing, reference numeral 1 denotes a non-quartz optical fiber, 2 denotes a silica fiber, and 3-1 and 3-2 denote an optical fiber holding case for holding an end of the non-quartz optical fiber 1 or the quartz optical fiber 2, respectively. Reference numerals 4-1 and 4-2 denote connection end surfaces of the optical fiber holding housings 3-1 and 3-2, and reference numeral 5 denotes an optical adhesive. As shown in the figure, the non-quartz optical fiber 1 and the silica fiber 2 are optical fiber holding housings at different angles θ ₁ and θ ₂ with respect to the vertical axes of the respective connection end surfaces 4-1 and 4-2. 3-1 and 3-2. As mentioned above,
A low-loss connection between the non-silica-based optical fiber 1 and the silica-based fiber 2 can be realized when the angles θ ₁ and θ ₂ [rad] satisfy the Fresnel formula shown in Expression 3.
The return loss R ₁ and R _{2 at} the connection between the non-quartz optical fiber 1 and the silica fiber ₂ are expressed by the following equation (4-
(This formula is described in the literature "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, _nUV is the refractive index of the optical adhesive 5, λ is the signal wavelength (wavelength used), and ω ₁ and ω ₂ are the mode field radii of the non-quartz optical fiber 1 and the silica fiber 2. . Therefore, from the above equation, by adjusting the angles θ ₁ and θ ₂ , a low reflection connection with a desired return loss or more can be realized. For example, non-quartz 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), the angle θ ₁ required to realize the return loss R ₁ = 40, 50, 60 dB and the quartz optical fiber 2 The angles θ ₁ and θ ₂ required to realize the return loss R ₂ = 40, 50, 60 dB are calculated by the following equation (5) obtained by transforming the equations (4-1) and (4-2). Can be obtained by

[0037]

(Equation 9)

In the formula, n _UV is the refractive index of the optical adhesive 5, λ is the signal wavelength, and n _1,2 is the core refractive index (the core refractive index n ₁ of the non-quartz fiber ₁ or the core refractive index of the quartz fiber 2). Rate n
₂ ) and ω _1,2 indicate 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) ω ₂ are both 5 μm (that is, ω _1,2 = 5 μm)
m), for example, a low loss between the telluride glass fiber and the silica-based fiber and a return loss of 60 d
In connection of B, θ _{1 is set} to 3.6 (deg) and θ _{2 is set} to 5.0.
(Deg) (the angle of θ ₂ is derived from Expression 3). However, actually, the connection surface 4-1 shown in FIG.
In order to realize the above, the processing roughness such as polishing generally used occurs, so that the actually obtained return loss is smaller than the calculated value. For this reason, a practical low reflection (return loss 6
The connection angle θ ₁ of the non-quartz fiber required to realize the above-mentioned (0 dB or more) is, for example, a practically low reflection (60 dB or more return loss) when the above-mentioned reduction of the return loss 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 In the case of an In-based fluoride fiber, the angle θ ₁ is desirably 4 degrees or more. Therefore, according to the connection method of Conventional Example 5, a non-quartz 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 quartz-based fiber can be used. The connection between them can be realized in general.

By the way, the inventors of the present invention have conducted intensive studies on the method of the conventional example 5, and as a result, there was no problem in applying the non-quartz fiber to the nonlinear element in the connection portion to which the conventional example 5 was applied.

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

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to solve the above-mentioned problems.
An object of the present invention is to provide an optical fiber connecting portion for connecting a non-quartz optical fiber and a silica fiber with low loss and low reflection without causing breakage, and an optical amplifier using the optical fiber connecting portion.

[0043]

Means for Solving the Problems To solve the above problems, the optical fiber connecting portions according to claim 1 (hereinafter referred to as the optical fiber connecting portions of the first invention) are different from each other in glass composition. A first optical fiber and a second optical fiber, at least one of which is a non-quartz fiber for optical amplification,
A first optical fiber holding case for holding an end of the first optical fiber, and a second optical fiber holding case for holding an end of the second optical fiber; In a state where the optical axis of the optical fiber is aligned with the optical axis of the second optical fiber, the connection end face of the first optical fiber holding housing and the second optical fiber holding housing are aligned. In an optical fiber connection portion in which the connection end face of the body is connected via an adhesive layer made of an adhesive, a connection end of the first optical fiber located at least on a connection end face of the first optical fiber holding housing. An adhesive layer made of the adhesive is not interposed between the second optical fiber holding housing and a connection end of the second optical fiber located on a connection end surface of the second optical fiber holding housing.

Preferably, one or both of the first optical fiber holding housing and the second optical fiber holding housing has a groove surrounding the end of the first optical fiber near the end thereof. A region where the end of the first optical fiber is located is a non-adhesion region where no adhesive layer made of the adhesive is interposed, and a region where the optical fiber is not located is the adhesive. As an adhesion region in which an adhesion layer made of is interposed, the adhesion region of the first optical fiber holding case and the second optical fiber holding case are adhered and connected via the adhesion region.

Preferably, the refractive index n ₁ of the core of the first optical fiber and the refractive index n ₁ of the core of the second optical fiber
₂ is different from the _second optical fiber, the first optical fiber is provided at an angle θ ₁ with respect to a perpendicular to a connection surface between the first optical fiber and the second optical fiber, and the second optical fiber The optical fiber has an angle θ different from the angle θ ₁ with respect to the perpendicular to the connecting surface between the first optical fiber and the second optical fiber.
₂ , and the relationship between the angle θ ₁ and the angle θ ₂ is as follows:

[0046]

(Equation 10)

The following Snell's formula is satisfied.

Preferably, any one of the first optical fiber and the second optical fiber is a group consisting of a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, and a telluride glass fiber. And more preferably, the selected optical fiber is provided at an angle θ with respect to a perpendicular to a connecting surface between the first optical fiber and the second optical fiber, and further, the angle θ Is 8 degrees or more when the selected optical fiber is a telluride-based fiber; 8 degrees or more when a chalcogenide-based fiber; 3 degrees or more when a Zr-based fluoride fiber; 4 degrees or more. Preferably, a rare earth element is added to the selected optical fiber.

The optical fiber connecting portion according to claim 7 (hereinafter, referred to as an optical fiber connecting portion of the second invention) comprises a first optical fiber and a first optical fiber having a glass composition different from that of the first optical fiber. A second optical fiber; a first optical fiber holding case for holding an end of the first optical fiber;
A second optical fiber holding case for holding the end of the optical fiber, and the optical axis of the first optical fiber is aligned with the optical axis of the second optical fiber. In a state where the connection end face of the first optical fiber holding casing and the connection end face of the second optical fiber holding casing are connected to each other, at least the first optical fiber holding casing is connected. Between the connection end of the first optical fiber located on the connection end face of the second optical fiber and the connection end of the second optical fiber located on the connection end face of the second optical fiber holding housing. Characterized in that an adhesive layer consisting of

Preferably, the silicone adhesive is
It is an ultraviolet curing silicone adhesive.

Preferably, the first optical fiber holding casing has a groove surrounding the end near the end of the first optical fiber, and the first optical fiber holding casing is separated from the first optical fiber by the groove. A first bonding area where the end of the optical fiber is located and where the bonding layer made of the silicone-based adhesive is in contact, and a second bonding area where the bonding layer made of another adhesive is in contact are the first light. The second optical fiber holding housing is provided on a connection end face of the fiber holding housing, and has a groove surrounding the end near the end of the second optical fiber, with the groove as a boundary. ,
The first adhesive region where the end of the second optical fiber is located and the adhesive layer made of the silicone adhesive is in contact, and the second adhesive region where the adhesive layer made of another adhesive is in contact are A second adhesive region of the first optical fiber holding case is provided on a connection end surface of the second optical fiber holding case, and a second adhesive region of the second optical fiber holding case is connected to the second optical fiber holding case. .

Preferably, the refractive index n ₁ of the core of the first optical fiber and the refractive index n ₁ of the core of the second optical fiber
₂ is different from the _second optical fiber, the first optical fiber is provided at an angle θ ₁ with respect to a perpendicular to a connection surface between the first optical fiber and the second optical fiber, and the second optical fiber The optical fiber has an angle θ different from the angle θ ₁ with respect to the perpendicular to the connecting surface between the first optical fiber and the second optical fiber.
₂ , and the relationship between the angle θ ₁ and the angle θ ₂ is as follows:

[0053]

[Equation 11]

This satisfies the Snell's formula.

Preferably, one of the first optical fiber and the second optical fiber is a group consisting of a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, and a telluride glass fiber. An optical fiber selected from the group consisting of: More preferably, the selected optical fiber is provided to be inclined at an angle θ with respect to a perpendicular to a connection surface between the first optical fiber and the second optical fiber, and further, the angle θ is
8 degrees or more when the selected optical fiber is a telluride-based fiber; 8 degrees or more when a chalcogenide-based fiber; 3 degrees or more when a Zr-based fluoride fiber; and 4 degrees when an In-based fluoride fiber It is characterized by the above. Preferably, a rare earth element is added to the selected optical fiber.

In the optical fiber connecting section based on the first and second inventions, preferably, the above-mentioned θ ₁ and the above-mentioned θ ₂ are set so as to achieve a predetermined return loss.

[0057]

(Equation 12)

(Where R is the return loss, n _UV is the refractive index of the adhesive, λ is the signal wavelength, ω _1,2 is the spot size of the _first or second optical fiber, θ _{1, 2} can satisfy θ ₁ or θ ₂ ).

An optical amplifier according to the present invention is an optical amplifier comprising at least two types of optical fibers and an optical fiber connecting portion for connecting the at least two types of optical fibers, wherein the optical fiber connecting portion is the first type. The optical fiber connecting portion according to the invention of the second aspect or the second aspect.

[0060]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an optical fiber connecting portion based on the first invention will be described with reference to FIGS. FIGS. 1, 2 and 3 are schematic side views for explaining the schematic configuration of the optical fiber connection portion, and the application location or application method of the adhesive is different from each other. The most characteristic feature of these optical fiber connection parts is that no optical adhesive is present on the fiber connection end face between the non-quartz optical fiber and the silica fiber. However, the inclination angle θ ₁ [rad] of the connection end face of the non-silica optical fiber with respect to the vertical axis and the inclination angle θ of the connection 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 the conventional example 5 already described. In the figure, reference numeral 1 is a non-quartz fiber,
Reference numeral 2 denotes a quartz fiber, 3-1 and 3-2 denote optical fiber holding cases for holding the ends of the optical fibers 1 and 2, respectively.
-1, 4-2 are connection surfaces of the optical fiber holding cases 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 case. , 4-2 shows a groove for an adhesive reservoir formed on the adhesive reservoir.

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

FIGS. 2 and 3 show a configuration in which the connection surface 4-1 of the optical fiber holding case 3-1 and the optical fiber holding case 3
2 and the connection surface 4-2 are completely adhered and fixed via an adhesive layer 5 made of an adhesive. At this time, the adhesive is prevented from spreading to a connection portion between the non-quartz optical fiber 1 and the silica optical fiber 2 and a region corresponding to the vicinity thereof.
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.
The adhesive reservoir grooves 6-1 and 6-2 are formed thereon. By providing such grooves 6-1 and 6-2, when the connection surface 4-1 and the connection surface 4-2 are brought into close contact with each other, the adhesive layer forming the pressed adhesive layer 5 is made of a non-quartz type. It can be prevented from flowing into the region corresponding to the connection between the optical fiber 1 and the silica-based optical fiber 2 and the vicinity thereof. In addition, it is easy to clearly define the portion where the adhesive layer 5 exists and the portion where it does not exist (the surface including the fiber connection end surfaces of the non-quartz optical fiber 1 and the silica optical fiber 2). The groove may be formed on the connection surface of at least one optical fiber holding case.
In the configuration shown in FIG. 2, the adhesive reservoir grooves 6-1, 6-2
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 in FIG. A specific example is shown in FIG.

FIG. 4 is a view for explaining the shape of an adhesive reservoir groove formed on the adhesive surface of the optical fiber holding housing. FIG. 4A is a side view of the optical fiber holding case,
3B is a front view corresponding to the side view of FIG. 3A as viewed from the connection end face of the optical fiber holding housing, 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. Further, in FIG.
Although the adhesive storage grooves are provided on both the connection surface 4-1 and the connection surface 4-2, if the adhesive storage groove exists on at least one of the connection surfaces, the connection surface with the adhesive is provided. There is no aspect.

As described above, the optical fiber connecting portion based on the first invention is, as shown in FIGS. 1, 2 and 3, a connecting end face of a non-quartz optical fiber and a connecting end face of a quartz fiber. And the optical adhesive layer does not intervene. For this reason, it is possible to solve the problem that the optical adhesive 5 is deteriorated and the connection part is damaged, which is a problem to be solved commonly in Conventional Examples 2, 3, 4, and 5.
As a result, it is possible to construct a highly reliable optical fiber amplifier using a non-quartz fiber that has been conventionally required.

In the optical fiber connection section based on the first invention, the angle θ _{1 of the} non-quartz fiber required for realizing a practically low reflection (reflection loss of 60 dB or more).
Similar to the case of the conventional example 5, is a telluride-based fiber of 8 degrees or more, a chalcogenide-based fiber of 8 degrees or more, a Zr-based fluoride fiber of 3 degrees or more, and an In-based fluoride fiber of 4 degrees or more.

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

The most characteristic feature of this optical fiber connecting portion is that a silicone-based light-curing adhesive is interposed between the connecting end face of the non-quartz-based optical fiber and the connecting end face of the quartz-based fiber. However, the relationship between the inclination angle θ ₁ [rad] of the connection end face of the non-silica type optical fiber with respect to the vertical axis and the inclination angle θ ₂ [rad] of the connection end face of the silica type optical fiber with respect to the vertical axis has already been described in the fifth conventional example. Equation 3 is satisfied in the same manner as

Conventionally, an epoxy or acrylic ultraviolet curable resin has been used as an optical adhesive from the viewpoint of its adhesive strength and environmental resistance. However, when a connection using such an epoxy or acrylic UV-curable optical adhesive is applied as a connection for an optical amplifier, visible light generated in a rare-earth-doped (Pr, Er, etc.) non-quartz fiber is used. Due to the light and ultraviolet light, the epoxy or acrylic optical adhesive changes color and becomes a light absorbing medium. As a result, this absorbing medium absorbs the excitation light,
Heat is generated, and a problem such as destruction of the connection portion occurs.
In order to solve such a problem, the present inventor examined changes in transmittance of the epoxy-based, acrylic-based, and silicone-based optical adhesives with respect to the ultraviolet light irradiation time. Table 1 shows the results of the study.

[0069]

[Table 1]

The change in the transmittance of the epoxy, acrylic and silicone optical adhesives with respect to the irradiation time of ultraviolet light (irradiation light wavelength: 0.42 μm, irradiation intensity: 95 mW / cm ² ) was determined by the epoxy, acrylic and silicone adhesives. The measurement was performed with a silicone adhesive having a thickness of 10 mm and a measurement wavelength of 0.8 μm. As shown in Table 1, as the epoxy and acrylic optical adhesives increase the 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 a stable transmittance even when irradiated with ultraviolet light.
Accordingly, even if the silicone-based optical adhesive is interposed between the connection end face of the non-quartz-based fiber and the connection end face of the quartz-based fiber, there is a problem in the related art (conventional examples 2, 3, 4, and 5). Therefore, there is no problem of deterioration of the optical adhesive and damage of the connection portion.

FIGS. 3, 4 and 5 show the structure of an optical fiber connecting portion using a silicone-based optical adhesive. In these figures, reference numeral 1 denotes a non-quartz fiber, 2 denotes a silica fiber, 3-1 and 3-2 denote optical fiber holding cases for holding the ends of the optical fibers 1 and 2, respectively.
Reference numerals 1 and 4-2 denote connection surfaces of the optical fiber holding housings 3-1 and 3-2, 5 denotes an adhesive, and 6 (6-1 and 6-2) denote connection surfaces 4-1 and 4-1 of the optical fiber holding housing. Reference numeral 4-2 denotes a groove for an adhesive reservoir formed on the substrate, and reference numeral 7 denotes a silicone-based optical adhesive layer.

In the configuration shown in FIG. 5, a silicone-based optical adhesive 7 is applied to the entire connection surfaces 4-1 and 4-2 of both optical fiber holding housings 3-1 and 3-2. At this time, the silicone optical adhesive 7 is also interposed between the connection end face of the optical fiber 1 and the connection end face of the optical fiber 2.

In the configuration shown in FIG. 6, the connection surface 4-1 of the optical fiber holding case 3-1 and the connection surface 4-2 of the optical fiber holding case 3-2 are connected via an adhesive layer 5 made of an adhesive. And completely fixed. At this time, the region where the adhesive layer 5 is provided is limited so that the adhesive 5 does not spread to the connection portion between the non-quartz optical fiber 1 and the silica optical fiber 2 and the region corresponding to the vicinity thereof. The adhesive 5
The silicone-based optical adhesive 7 is interposed in a region where no is interposed, that is, between the connection surface of the optical fiber 1 and the connection surface of the optical fiber 2 and further in the vicinity of the connection surface.

In the configuration shown in FIG. 7, the adhesive storage grooves 6-1 and 6--6 are provided on the connection surfaces 4-1 and 4-2 of the optical fiber holding housing.
2 are formed. By providing such grooves 6-1 and 6-2, when the connection surface 4-1 and the connection surface 4-2 are brought into close contact with each other, the adhesive layer forming the pressed adhesive layer 5 is made of a non-quartz type. It can be prevented from flowing into the region corresponding to the connection between the optical fiber 1 and the silica-based optical fiber 2 and the vicinity thereof. In addition, it is easy to clearly define the portion where the adhesive layer 5 exists and the portion where it does not exist (the surface including the fiber connection end surfaces of the non-quartz optical fiber 1 and the silica optical fiber 2). Further, the region 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 connection surface of the optical fiber 1 and the connection surface of the optical fiber 2 and in the region near the connection surface with -2 as a boundary. in this way,
In the configuration shown in FIG. 7, the adhesive reservoir grooves 6-1 and 6-2 are formed, so that a portion having the adhesive layer 5 and a portion of the silicone-based optical adhesive layer 7 are clearly separated and easily. Can be provided. In FIG. 7, the grooves 6-1 and 6-2 for storing the adhesive are provided in a line shape. However, the present invention is not limited to this, and the shape such as the concentric shape shown in FIG. It is. Further, in FIG. 7, the connection surfaces 4-1 and 4
-2, the adhesive storage groove is provided, but if the adhesive storage groove exists on at least one connection surface, it is possible to realize the connection surface with the adhesive and the surface without the adhesive. .

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

In the optical fiber connection section based on the first invention, the angle θ _{1 of the} non-quartz fiber required for realizing a practically low reflection (a return loss of 60 dB or more) is obtained.
Similar to the case of the conventional example 5, is a telluride-based fiber of 8 degrees or more, a chalcogenide-based fiber of 8 degrees or more, a Zr-based fluoride fiber of 3 degrees or more, and an In-based fluoride fiber of 4 degrees or more.

Hereinafter, the first and second embodiments will be described with reference to the drawings.
The optical fiber connecting portion based on the invention of 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) Embodiment 1 describes a first connection technique of the present invention.

(I) Embodiment 1-1 FIG. 8 shows a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 8 (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 housing. In the figure, reference numeral 1 denotes an Er-doped telluride glass fiber (glass composition is TeO ₂ -ZnO).
-Na ₂ O, core refractive index is 2.1, mode field radius is 5 μm, Er addition concentration is 4000 ppm, coating of this fiber is UV resin, 2 is quartz-based fiber (core refractive index is ~ 1.5, mode The field radius is 5 μm, and the coating is UV resin. Reference numerals 8-1 and 8-2 denote V-groove type optical fiber holding housings for holding the ends of the optical fibers 1 and 2, respectively. The optical fiber holding housings 8-1 and 8-2 have a V-groove substrate 9 inside.

In the optical fiber connecting portion composed of such components, the optical fibers 1 and 2 are positioned by V-groove substrates 9 provided in the optical fiber holding casings 8-1 and 8-2, respectively. It was provided by fixing to the V-groove type optical fiber holding housings 8-1 and 8-2 with the adhesive 10 and the optical fiber fixing plate 11. V-groove optical fiber holding case 8-
1, 8-2, V-groove substrate 9, and optical fiber fixing plate 11
Was made of Pyrex glass. In the present embodiment, the V-groove type optical fiber holding housings 8-1, 8-
2 and the connection end faces 12-1 and 12-2 are completely adhered to each other without an optical adhesive therebetween, 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 and 12-2.
₁ = 18 [deg] and θ ₂ = 25 [deg]. With 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 connection loss was measured at 1.2 μm, where the Er-doped telluride glass fiber 1 did not absorb Er ions.

The return loss measured from the Er-doped telluride glass fiber 1 and the quartz-based fiber 2 was 60 dB or more (a commercially available return loss measuring device 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 the connection portion exhibits high-performance and low-reflection characteristics higher than the measurement range of the measurement device).

The optical fiber 1 and the silica-based fiber 2
The angles of the 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 connection loss between the Er-doped telluride glass fiber 1 and the quartz-based fiber 2 is 0.1 dB (measuring wavelength 1.2 μm), and the Er-doped telluride glass fiber 1 and the quartz-based fiber The return loss measured from the second 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 connection end faces 12-1 and 12-2 are [θ ₁ = 5 [deg], θ ₂ = 7 [deg]]. The connection loss between the Er-doped telluride glass fiber 1 and the silica-based fiber 2 is 0.2 dB (measurement wavelength 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 (return loss of 60 dB or more), the telluride glass fiber must be 8 [deg] or more with respect to the vertical axis of the connection end face. It turned out that an angle was required.

Although the above description has been made using the Er-doped telluride glass fiber, other In-based fluoride fibers, Zr-based fluoride fibers, and chalcogenide-based fibers (each doped with a rare earth element such as Er, Pr, Tm, etc.) The same good connection is realized by setting the angle θ ₁ to 8 degrees or more for chalcogenide-based fiber, 3 degrees or more for Zr-based fluoride fiber, and 4 degrees or more for In-based fluoride fiber. did it.

(Ii) Embodiment 1-2 FIG. 9 shows a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 9A 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 housing. In the figure, reference numeral 1 denotes an Er-doped telluride glass fiber (glass composition is TeO ₂ -ZnO).
-Na ₂ O, core refractive index is 2.1, mode field radius is 5 μm, Er addition concentration is 4000 ppm, coating of this fiber is UV resin, 2 is quartz-based 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 applied as optical fiber holding housings (connection end faces 14-1 and 14-2 are made of respective glasses). This was realized by obliquely polishing the ferrules 13-1 and 13-2).

The Er-doped telluride glass fiber 1 and the quartz fiber 2 are bonded to the glass ferrules 13-1 and 13- using an adhesive 10 (using an acrylic UV adhesive).
Fixed to 2. As the adhesive 5 for fixing the side surface, an epoxy-based adhesive was used. Optical fiber 1 and fiber 2
Of the connection end surfaces 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 (measuring wavelength 1.2 μm).
m), the return loss measured from the Er-doped telluride glass fiber 1 and the quartz-based fiber 2 was 60 d
B or higher was achieved.

As in the case of Embodiment 1-1, the telluride glass fiber and the connection end face and the vertical surface which are necessary for connecting the telluride glass fiber and the silica-based fiber with low loss and low reflection (reflection loss of 60 dB or more) are used. The angle between the axes is 8
[Deg] or more.

Although the above description has been made using the Er-doped telluride glass fiber, other In-based fluoride fibers, Zr-based fluoride fibers, and chalcogenide-based fibers (each doped with the rare earth elements Er, Pr, Tm, etc.) The same good connection is realized by setting the angle θ ₁ to 8 degrees or more for chalcogenide-based fiber, 3 degrees or more for Zr-based fluoride fiber, and 4 degrees or more for In-based fluoride fiber. did it.

(Iii) Embodiment 1-3 FIGS. 10A and 10B show a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 10A 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 housing. FIG. 11 is a modification of FIG. 10, in which a ferrule is used as an optical fiber holding case, (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 case. In the figure, reference numeral 1 Pr adding 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 added concentration is 1000 ppm, 2 is a quartz 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 housings for holding the ends of the optical fibers 1 and 2, respectively. Each optical fiber 1 or 2 is a V-groove. It was positioned by the substrate 9, and was fixed to the V-groove type optical fiber holding case 8-1 or 8-2 by the adhesive 10 and the optical fiber fixing plate 11. V-groove type optical fiber holding case 8-1,
8-2, V-groove substrate 9, and optical fiber fixing plate 11 were made of Pyrex glass.

Further, reference numerals 13-1, 13- in FIG.
Reference numeral 2 denotes a ferrule used as an optical fiber holding case. Here, the Pr-doped Zr-based fluoride fiber 1 and the quartz-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 with connection end surfaces 12-1 and 12- which do not include the fiber connection surfaces of the optical fibers 1 and 2.
2 or 14-1 and 14-2, the V-groove type optical fiber holding housings 8-1, 8-2 or the ferrules 13-1, 13 to which the optical fibers 1 and 2 are fixed are provided.
-2 is adjusted 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 are connected.
And 14-2 are brought into close contact with each other, and an ultraviolet-curing type adhesive is applied from the side surface of the V-groove type optical fiber holding housings 8-1 and 8-2 or the ferrules 13-1 and 13-2 using the capillary phenomenon at the interface. This is realized by injecting the agent 5 and curing the adhesive 5 using ultraviolet rays before the adhesive 5 reaches the fiber connection surface between the optical fiber 1 and the optical fiber 2.

The optical fiber 1 and the silica-based fiber 2 are
Each connection end face 12-1, 12-2 or 14-1,
With respect to the vertical axis of 14-2, θ ₁ = 3 [deg], θ ₂ =
It was kept at 3.1 [deg]. By this connection (both when using the V-groove type optical fiber holding case 8 and when using the ferrule 13), the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB or less. I was able to connect. However, the splice loss was 1.2 μm without absorption of Pr ions in the Pr-doped Zr-based fluoride fiber 1.
m. The return loss measured from the side of the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 is 60 dB or more (both in the case where the V-groove type optical fiber holding case 8 is used and in the case where the ferrule 13 is used). )
(A commercially available return loss measuring instrument was used for the measurement, the measurement wavelength was 1.2 μm, and the measuring instrument could not measure the return loss of 60 dB or more. The high performance and low reflection characteristics described above are shown).

The connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2
-1, 14-2 with respect to the vertical axis are represented by [θ ₁ = 4
[Deg] or θ ₁ = 6 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB (measurement wavelength 1.3 μm).
m), the return loss measured from the side of the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 was 60 dB, respectively.
That was all. Here, the angle of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of each connection end face 12-1, 12-2 or 14-1, 14-2 is [θ ₁ =
2 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB.
(Measurement wavelength: 1.2 μm), but the return loss measured from the side of the Pr-doped Zr-based fluoride fiber 1 was 53d.
B, and as a result, the Zr-based fluoride fiber and the silica-based fiber have low loss and low reflection (return loss of 60 dB or more).
It has been found that the Zr-based fluoride fiber is required to have an angle of 3 [deg] or more with respect to the vertical axis of the connection end face in order to connect with each other.

Although the above description has been made using the Pr-doped Zr-based fluoride fiber, other In-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (each doped with the rare earth elements Er, Pr, Tm, etc.) The same good connection as described above could be realized by setting the angle θ ₁ to In-fluoride fiber 4 ° or more, telluride-based fiber 8 ° or more, and chalcogenide-based fiber 8 ° or more.

(Iv) Embodiment 1-4 FIGS. 12A and 12B show a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 12A 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 housing. FIG. 13 is a modification of FIG. 12, in which a ferrule is used as an optical fiber holding case, (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 case. In the figure, reference numeral 1 denotes a Pr-doped 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 added concentration: 1000 ppm, 2: quartz fiber (core refractive index) 〜1.5, mode field radius 4.5 μm, coating UV resin), 8-1,8
-2 are V holding the ends of the optical fibers 1 or 2, respectively.
This is a groove type optical fiber holding case, in which each optical fiber 1 or 2 is positioned by a V-groove substrate 9 and an adhesive 1
The optical fiber was fixed to the V-groove type optical fiber holding case 8-1 or 8-2 by the optical fiber fixing plate 11 and the optical fiber fixing plate 11.

V-groove type optical fiber holding case 8-1, 8-
2. 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 and 13- in FIG.
Numeral 2 denotes a ferrule used as an optical fiber holding housing (Pr-doped In-based fluoride fiber 1 and quartz-based fiber 2 use an adhesive 10 (using an acrylic UV adhesive) to form a glass ferrule 13-1, 13-2). Connection surface 1 of ferrule 13-1 or 13-2
4-1 and 14-2 have grooves 16-1 and 16-2 for storing the adhesive.
Has been processed.

In the present embodiment, as shown in FIGS. 12 and 13, the adhesive layer 5 is formed by connecting 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. 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 lowest connection loss between the optical fibers 1 and 2. After the alignment, the connection end faces 12-1 and 12-1
2-2 or 14-1 and 14-2 are brought into close contact with each other, and a V-groove type optical fiber holding case 8 is
-1,8-2 or the side surface of the ferrules 13-1 and 13-2 was injected with an ultraviolet-curable adhesive 5. Adhesive 5
Are the adhesive reservoir grooves 15-1, 15-2 or 16-1,
16-2 prevented its penetration.

By using the adhesive reservoir groove used in this embodiment, the adhesive layer 5 can be connected to the connection end surfaces 12-1 and 12-2 or 14-1 not including the connection surfaces of the optical fibers 1 and 2.
And the connection structure provided only in 14-2 is the embodiment 1-3.
It was also found that it could be realized more reliably than.

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,
θ ₂ was kept at 4.1 [deg]. This connection (when the V-groove type optical fiber holding case 8 is used and when the ferrule 1 is used)
3), the connection loss between the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.15.
Connection was possible at less than dB. However, the connection loss is such that the Pr-doped In-based fluoride fiber 1 does not absorb Pr ions,
It was measured at 1.2 μm.

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

The connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2
-1, 14-2 with respect to the vertical axis are represented by [θ ₁ = 5
[Deg] or θ ₁ = 6 [deg]], the connection loss between the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB (measuring wavelength 1.3 μm).
m), the return loss measured from the side of the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 60 dB, respectively.
That was all. Here, the angle of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of each connection end face 12-1, 12-2 or 14-1, 14-2 is [θ ₁ =
3 [deg]], the connection loss between the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB.
(Measurement wavelength: 1.2 μm), but the return loss measured from the side of the Pr-doped In-based fluoride fiber 1 was 59 dB.
Met. As a result, in order to connect the In-based fluoride fiber and the quartz-based fiber with low loss and low reflection (return loss of 60 dB or more), the In-based fluoride fiber must be connected to the vertical axis of the connection end face by 3 [ deg] or more.

Although the above description has been made using the Pr-doped In-based fluoride fiber, other Zr-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (each doped with the rare earth elements Er, Pr, Tm, etc.) The same good connection as above can be realized by setting the angle θ ₁ to 3 degrees or more of Zr-based fluoride fiber, 8 degrees or more of telluride-based fiber, and 8 degrees or more of chalcogenide-based fiber. .

Further, the Er-doped telluride glass fiber 1 (glass composition is TeO ₂ -ZnO-Na ₂ O, core refractive index is 2.1, mode is 2.1 The field radius is 5 μm, the Er doping concentration is 4000 ppm, the fiber length is 1 m, and the coating is U
V-resin) were connected to both ends of a silica-based fiber to form an optical fiber amplifier shown in FIG. In the figure, reference numeral 17-
Reference numeral 1, 17-2 denotes an excitation light source for generating excitation light to the optical fiber 1, which uses a semiconductor laser having an oscillation wavelength of 1.48 μm (each output is 200 mW) for the Er-doped telluride glass fiber 1. Also, reference numerals 18-1 and 18-1
Reference numeral -2 denotes a multiplexing unit for multiplexing the signal light and the pump light generated in 17-1, 17 and 2, and 19-1 and 19-2 denote 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 first embodiment of the present invention.
-1 to 1-4 (that is, FIG. 8, FIG. 9, FIG.
0, 11, 12, and 13). However, Embodiment 1-1 and Embodiment 1-
In the connection section using the V-groove type optical fiber holding housing 8 at 3, 1-4, the angle of the optical fiber 1 and the silica-based fiber and the connection end faces 12-1, 12-2 with respect to the vertical axis is θ ₁ = 14.
[Deg], θ ₂ = 20 [deg], and in the connection part using the ferrule 1 in the embodiment 1-2 and the embodiment 1-3, 1-4, the connection end face with the optical fiber 1 and the silica-based fiber is used. The angles of the 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 methods shown in Embodiment Examples 1-1 to 1-4, a signal gain of the optical fiber amplifier of 40 dB or more was realized, and no ghost occurred in the optical fiber amplifier.

FIG. 14 (b) shows an example of the amplification characteristics of the present fiber amplifier (FIG. 14 shows the characteristics of the connection using the embodiment 1-1, but the embodiments 1-2 and the embodiments). Similar results were obtained with the V-groove type optical fiber holding housing 8 of 1-3 and 1-4 and the ferrule 13).

FIG. 15 shows Embodiments 1-1 to 1-1.
4 shows a time change of the signal gain of the optical amplifier configured using the connection section of FIG. The signal wavelength is 1.54 μm. Also,
FIG. 9 also shows the characteristics of an optical fiber amplifier configured by using the method of the conventional example 5. As shown in the figure, the use of the connection portions of the embodiment examples 1-1 to 1-4 can solve the problem that the optical adhesive deteriorates and the connection portion is broken which could not be solved in the conventional example 5. As a result, a highly reliable optical fiber amplifier using a non-quartz fiber was constructed.

Further, Embodiment 1-1 (FIG. 8), Embodiment 1-3 (FIG. 10), and Embodiment 1-4 (FIG. 1)
In 2), the V-groove type optical fiber holding case 8 is the first embodiment.
2 (FIG. 9), the embodiment 1-3 (FIG. 11), and the modification of the embodiment 1-4 (FIG. 13), the ferrule 13 is used. It has been found by actual work that it has the characteristic of shortening the time required for manufacturing the optical fiber (V-groove type optical fiber holding housing, manufacturing time: 45
Min, ferrule, production time: 10 minutes). This is because when the V-groove type optical fiber holding case 8 is manufactured, 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, which is fixed to the V-groove type optical fiber holding case 8,
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.

Further, in the connecting portions of the embodiment 1-1 and the embodiment 1-2, the optical fiber holding casings 8-1, 8 are provided.
-2 or fixing the ferrules 13-1 and 13-2,
A side fixing method in which the both sides were fixed with an 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 housings 8-1 and 8-2 or the ferrules 13-1 and 13-2, and the adhesive 5 thermally expands. Alternatively, when contracted, the optical fiber holding casing 8-1
When the optical fiber holding case 8-2 moves left and right, or when the ferrule 13-1 and the ferrule 13-2 move left and right, the connection surface of the optical fiber may shift. On the other hand, in the connection portions of the embodiment 1-3 and the embodiment 1-4, the connection end surfaces 12-1 and 12-2 not including the connection surfaces of the optical fibers 1 and 2 are provided.
Alternatively, the adhesive layer 5 is provided on 14-1 and 14-2. This adhesive layer 5 is very thin (usually １1 μm);
Or because the direction of thermal expansion and contraction is the vertical direction,
In the connection portions of the first to third embodiments and the first to fourth embodiments, compared to the connection portions of the first and second embodiments, a connection portion having less change in loss can be stably realized. Was.

FIG. 16 shows Embodiments 1-1 and 1-2.
6 is a graph showing a temperature change of a connection loss of a connection portion of the connection portion and a temperature change of a connection portion loss of a connection portion of Embodiments 1-3 and 1-4. As shown in FIG. 16, the temperature is changed from room temperature (20.degree. C.) to 60.degree. C. with time, or gradually lowered from 60.degree. C. to 0.degree. C., and then returned to room temperature. I went. In the curves relating to the loss characteristics, the broken lines indicate the embodiment 1-1 and the embodiment 1-2.
, The solid line relates to the embodiment 1-3 and the embodiment 1-4.

The plot of each curve plots the value of the sample which showed the largest change in the loss characteristic among the predetermined number of samples as follows. That is, the first embodiment of the present invention
-3 and 1-4, the number of samples was 20 (5 samples having the configuration of FIG. 9, 5 samples having the configuration of FIG. 11, 5 samples having the configuration of FIG. 12, 5 samples of FIG. 13). Among the five samples having the configuration, the characteristics of the sample having the most remarkable fluctuation were plotted, and a solid curve as shown in the figure was obtained.

Also, among the 20 samples (10 samples having the configuration shown in FIG. 8 and 10 samples having the configuration shown in FIG. 9) of the optical fiber connection portions of the embodiment examples 1-1 and 1-2, The characteristics of those having significant fluctuation were plotted, and a dashed curve as shown in the figure was obtained. The optical fiber 1 is 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 addition concentration: 1000 ppm), and a silica-based fiber (core refractive index: ~ 1.5, mode field radius: 4.5 [mu] m, the coating: UV resin), .theta.1 is 3 [deg] with respect to the vertical axis of the connection end face, theta ₂ is 3.1 [de
g]. From the same characteristics, Embodiment Examples 1-3 and 1-
It has been found that the optical fiber connection of No. 4 can realize an optical fiber connection having thermal stability.

In the above embodiment, the optical fiber holding case 8 and the ferrule 13 are made of glass. However, similar results are obtained by using plastic.

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

(I) Embodiment 2-1 FIG. 17 shows a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 17A 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 housing. FIG. 18 is a modification of FIG. 17, in which a ferrule is used as an optical fiber holding case, (a) is a side view showing the entire optical fiber connecting portion, and (b) is an optical fiber holding case. FIG. 4 is a side view showing the connection end face of FIG. In the figure, reference numeral 1 denotes a Pr-doped chalcogenide glass fiber (glass composition: As-S, core refractive index:
2.4, mode field radius: 3 μm, coated UV resin, Pr added concentration: 1000 ppm, 2: quartz fiber (core refractive index: ~ 1.5, mode field radius:
5 μm, coating: UV resin), 8-1 and 8-2 are V-groove type optical fiber holding housings for holding the ends of the optical fibers 1 and 2, respectively.
It is positioned by the groove substrate 9, and is fixed to the V-groove type optical fiber holding case 8-1 or 8-2 by the adhesive 10 and the optical fiber fixing plate 11 (FIG. 18).

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

Also, reference numerals 13-1, 13- in FIG.
Reference numeral 2 denotes a glass ferrule. The Pr-doped chalcogenide glass fiber 1 and the quartz-based fiber 2 are made of glass ferrule 13- using an adhesive (acrylic UV adhesive).
1, 13-2.

[0117] Pr-doped chalcogenide glass fiber 1
As shown in FIG. 17 and FIG. 18, the connection between the fiber and the silica-based fiber 2 is made between the connection end faces 12-1 and 12-2 of the V-groove type optical fiber holding casings 8-1 and 8-2 or the glass ferrule 13-1. , 13-2 between the connection end surfaces 14-1 and 14-2 using an ultraviolet-curing silicone adhesive 7.

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

By this connection, the connection loss between the Pr-doped chalcogenide glass fiber 1 and the silica-based fiber 2 is reduced to 0.
Connection was possible at 2 dB. However, the splice loss was measured at 1.2 μm where the Pr-doped chalcogenide glass fiber 1 did not absorb Pr ions.

The return loss measured from the Pr-doped chalcogenide glass fiber 1 and the quartz fiber 2 was 60 dB or more (a commercially available return loss measuring device 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 the connection portion exhibits high-performance and low-reflection characteristics higher than the measurement range of the measurement device).

The optical fiber 1 and the silica-based fiber 2
Each connection end face 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 connection loss between the Pr-doped chalcogenide glass fiber 1 and the silica-based fiber 2 is 0.15 dB (measuring wavelength 1.2 μm), and the Pr-doped chalcogenide glass is The return loss measured from the fiber 1 and the quartz-based fiber 2 was 60 dB or more. However, optical fiber 1
And the respective connection end faces 12-1,
The angle of 12-2 or 14-1, 14-2 with respect to the vertical axis is represented by [θ ₁ = 6 [deg], θ ₂ = 7 [deg]]
, The Pr-doped chalcogenide glass fiber 1
The connection loss between the fiber 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 dB.
B.

As a result, the chalcogenide glass fiber and the silica-based fiber were made to have a low loss and a low reflection (a return loss of 60).
(dB or more), it has been found that it is necessary to connect 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, a Pr-doped chalcogenide glass fiber is used, but other In-based fluoride fibers, Zr-based fluoride fibers, and telluride-based fibers (each doped with a rare earth element Er, Pr, Tm, etc.) The same good connection as described above was realized by setting the angle θ ₁ to 8 degrees or more of telluride-based fiber, 3 degrees or more of Zr-based fluoride fiber, and 4 degrees or more of In-based fluoride fiber. .

(Ii) Embodiment 2-2 FIG. 19 shows a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 19 (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 housing. FIG. 20 shows a modification of FIG. 19, in which a ferrule is used as an optical fiber holding case. FIG. 20 (a) is a side view showing the entire optical fiber connecting portion, and FIG. 20 (b) is an optical fiber holding case. FIG. 4 is a side view showing the connection end face of FIG. In the figure, reference numeral 1 denotes an Er-doped Zr-based fluoride fiber (glass composition: ZrF ₄ -BaF ₂ -LaF _3).
—YF ₃ —AlF ₃ —LiF—NaF, core refractive index:
1.55, mode field radius: 4 μm, coating: UV
Resin, Er added concentration: 1000 ppm), 2 is a quartz fiber (core refractive index: ~ 1.5, mode field radius: 4 µm, coating: UV resin), reference numerals 8-1, 8-
Reference numeral 2 denotes a V-groove type optical fiber holding housing for holding the end of the optical fiber 1 or 2, respectively. Each optical fiber 1 or 2 is positioned by a V-groove substrate 9, and an adhesive 10
And the optical fiber fixing plate 11 to fix the optical fiber holding case 8-1 or 8-2 to the V-groove type optical fiber.

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

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

In the embodiment 2-2, as shown in FIGS. 19 and 20, the epoxy-based adhesive layer 5 is
Connection end faces 12-1 and 1 not including the connection faces 2 and 1
2-2 or 14-1 and 14-2 only, and the silicone adhesive layer 7 is attached to 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. Before the 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 face including the connection face of the optical fiber 1 or 2 at one connection end face of each of the two, and the epoxy is applied to the connection end face not including the connection face of the optical fiber 1 or 2 at the connection end face. After applying the system adhesive 5, a V-groove type optical fiber holding housing 8-
1, 8-2 or the ferrules 13-1 and 13-2 are realized by aligning the cores so that the connection loss between the optical fibers 1 and 2 is minimized. The optical fiber 1 and the silica-based fiber 2 are connected to respective connection end faces 12-1, 12-2 or 1
Θ ₁ = 3 [de with respect to the vertical axis of 4-1 and 14-2
g], θ ₂ = 3.1 [deg]. By this connection (both when using the V-groove type optical fiber holding case 8 and when using the ferrule 13), Er-doped Zr
The connection between the system-based fluoride fiber 1 and the quartz-based fiber 2 was achieved with a connection loss of 0.11 dB or less. However, connection loss is
The measurement was performed at 1.3 μm where the Er-doped Zr-based fluoride fiber 1 did not absorb Er ions.

The Er-doped Zr-based fluoride fiber 1
And the return loss measured from the quartz fiber 2 side is:
Each was 60 dB or more (both in the case of using the V-groove optical fiber holding case 8 and in the case of using the ferrule 13) (a commercially available return loss measuring instrument was used for measurement, the measurement wavelength was 1.3 μm, This measuring device cannot measure a return loss of 60 dB or more, and the connecting portion exhibits high-performance and low-reflection characteristics higher than the measuring range of the measuring device.)

The optical fiber 1 and the silica-based fiber 2
Each connection end face 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 quartz-based fiber 2 is 0.09 dB (the measurement wavelength is 1.3 μm).
m), the return loss measured from the Er-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 was 60 dB, respectively.
That was all. Here, the angle of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of each connection end face 12-1, 12-2 or 14-1, 14-2 is [θ ₁ =
2 [deg]], the connection loss between the Pr-doped Zr-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 dB.
(Measurement wavelength: 1.2 μm), but the return loss measured from the Er-doped Zr-based fluoride fiber 1 was 51 dB.
Met.

As a result, in order to connect the Zr-based fluoride fiber and the quartz-based fiber with low loss and low reflection (reflection loss of 60 dB or more), the Zr-based fluoride fiber must be connected to the vertical axis of the connection end face by three times. It has been found that the connection is required to be inclined at an angle of [deg] or more.

Although the above description has been made using the Er-doped Zr-based fluoride fiber, other In-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (each doped with a rare earth element such as Er, Pr, or Tm) are used. The same good connection as described above could be realized by setting the angle θ ₁ to 4 degrees or more for the In-based fluoride fiber, 8 degrees or more for the telluride-based fiber, and 8 degrees or more for the chalcogenide-based fiber.

(Iii) Embodiment 2-3 FIGS. 21A and 21B show a schematic configuration of an optical fiber connecting portion based on the present embodiment. FIG. 21A 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 housing. FIG. 22 shows a modification of FIG. 21 in which a ferrule is used as an optical fiber holding case. FIG. 22 (a) is a side view showing the entire optical fiber connecting portion, and FIG. 22 (b) is an optical fiber holding case. FIG. 4 is a side view showing the connection end face of FIG. In the figure, reference numeral 1 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, mode field radius: 4.5 μ
m, coating: UV resin, Er addition concentration: 1000 pp
m), 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 ends of optical fiber 1 or 2, respectively. The optical fiber 1 or 2 is positioned by a V-groove substrate 9, and the V-groove optical fiber holding case 8 is fixed by an adhesive 10 and an optical fiber fixing plate 11. -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 optical fiber holding case 8-
Adhesive reservoir grooves 15-1 and 15-2 are formed in connection surfaces 12-1 and 12-2 of 1 or 8-2.

Reference numerals 13-1 and 13-2 denote ferrules used as optical fiber holding housings (Pr-doped In-based fluoride fiber 1 and quartz-based fiber 2 are adhesives 10 (acrylic UV adhesive). Was fixed to the glass ferrules 13-1 and 13-2). Connection surface 14-1, 1 of ferrule 13-1 or 13-2
At 4-2, the grooves 16-1 and 16-2 for storing the adhesive are formed.

In the embodiment 2-3, as shown in FIGS. 21 and 22, the epoxy-based adhesive layer 5 is
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 are provided only on the connection end faces 12-1 and 12-2 not including the connection faces of the optical fibers 1 and 2.
V-groove type optical fiber holding housings 8-1 and 8-2 to which optical fibers 1 and 2 are fixed are provided in V-groove type optical fiber holding housings 8-1 and 8-2 to be provided in 2-1 and 12-2 or 14-1 and 14-2. Alternatively, ferrules 13-1 and 13-2 are connected to optical fibers 1 and 2
Of the connection end face 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 housings 8-1 and 8-2 or the ferrules 13-1 and 1-1 are formed at the interface using capillary action.
3-2, an epoxy-based UV-curable adhesive 5 and a silicone-based UV-curable adhesive 7 were injected from the side.
The epoxy-based UV-curable adhesive 5 and the silicone-based UV-curable adhesive 7 can be easily separated from each other by the adhesive reservoir grooves 15-1 and 15-2 or 16-1 and 16-2.

By using the adhesive reservoir groove used in the embodiment 2-3, the epoxy-based adhesive layer 5 can be connected to the connection end surfaces 12-1 and 12-1 not including the connection surfaces of the optical fibers 1 and 2.
2-2 or 14-1 and 14-2, the silicone-based adhesive layer 7 is provided with a connection end face 12 including a connection face of 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 (the connection portion 5 in the embodiment 2-2).
The excellent result is that 32 pieces are non-defective during the production of one piece, while 95 pieces are non-defective 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 14-2.
Θ ₁ = 4 [deg] with respect to the vertical axes of −1 and 14-2,
θ ₂ was kept at 4.1 [deg]. This connection (when the V-groove type optical fiber holding case 8 is used and when the ferrule 1 is used)
3), the connection loss between the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.13.
Connection was possible at less than dB. However, the connection loss is such that Er-doped In-based fluoride fiber 1 does not absorb Er ions.
It was measured at 1.3 μm.

The return loss measured from the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 6
0 dB or more (both in the case of using the V-groove type optical fiber holding case 8 and in the case of using the ferrule 13) (a commercially available return loss measuring instrument was used for measurement, the measurement wavelength was 1.3 μm, The measuring device cannot measure the return loss of 60 dB or more, and the connection portion exhibits high-performance and low-reflection characteristics higher than the measuring range of the measuring device).

The connection end faces 12-1, 12-2 or 14 of the optical fiber 1 and the silica-based fiber 2
-1, 14-2 with respect to the vertical axis are represented by [θ ₁ = 5
Even when [deg] or θ ₁ = 6 [deg]], the connection loss between the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.115 dB (measurement wavelength 1.
3 μm), the return loss measured from the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 60
dB or more. Here, the angle of the optical fiber 1 and the silica-based fiber 2 with respect to the vertical axis of each connection end face 12-1, 12-2 or 14-1, 14-2 is [θ
₁ = 3 deg]], the connection loss between the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.1 d.
B (measurement wavelength: 1.2 μm), but the return loss measured from the Er-doped In-based fluoride fiber 1 was 57 d.
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 attenuation of 60 dB or more), the In-based fluoride fiber must be connected to the vertical axis of the connection end face. It was found that an angle of 3 [deg] or more was required.

Although the above description has been made using the Er-doped In-based fluoride fiber, other Zr-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (each doped with a rare earth element such as Er, Pr, or Tm) are used. The same good connection as described above could be 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, a quartz fiber was connected to both ends of a Pr-doped In-based fluoride fiber by the connection method shown in the above-described Embodiment Examples 2-1 to 2-3, thereby forming an optical fiber amplifier shown in FIG. Reference numerals 17-1 and 17-2 denote excitation light source units for generating excitation light for the optical fiber 1, and Nd-YLF lasers having an oscillation wavelength of 1.047 μm (each of which is an excitation light source for the Pr-doped In-based fluoride fiber 1). Output was 500 mW). Reference numerals 18-1 and 18-2 denote multiplexing sections for multiplexing signal light and pump light generated in 17-1 and 17-2. Reference numerals 19-1 and 19-2 denote oscillations of an optical amplifier. It is an optical isolator. Also, 20-1, 2
As the connection part 0-2, the connection parts of the present embodiment examples 2-1 to 2-3 (all the implementations shown in FIGS. 17 to 22) were applied. Optical fiber 1 and silica-based fiber and connection end face 12
The angles of the −1, 12-2 or 14-1, 14-2 with respect to the vertical axis are θ ₁ = 4 [deg] and θ ₂ = 4.1 [de].
g].

By using the connection method described in the embodiment examples 2-1 to 2-3, the signal gain of the optical fiber amplifier is 30d.
B and above were realized, and no ghost occurred in the optical fiber amplifier. Further, the life of the optical fiber amplifier (measured by operating at a signal gain of 33 dB at 1.30 μm) measured using the conventional technology (prior arts 2, 3, 4, and 5) was 400 hours at the maximum. The life of the optical fiber amplifier to which the connecting portions (all shown in FIGS. 17 to 22) of the embodiment examples 2-1 to 2-3 are applied is 5000 hours.
r, and using the second invention, as in the first invention, the conventional technology (conventional examples 2, 3,
The problem that the optical adhesive deteriorates and the connection part is broken, which could not be solved in 4, 5), can be solved, and a highly reliable optical fiber amplifier using a non-quartz fiber can be constructed.

In addition, FIGS. 17 and 2-2 of the embodiment 2-1.
19 and FIG. 21 of FIG. 2-3, the V-groove type optical fiber holding housing 8, and FIGS.
In FIG. 22-3, the ferrule 13 was used, but it was found by actual work that the connecting part using the ferrule 13 has a feature that the time required for manufacturing the connecting part can be shortened (V
(Groove type optical fiber holding case, production time: 45 minutes, ferrule, production time: 10 minutes). This is because, when the V-groove type optical fiber holding case 8 is manufactured, each of the optical fibers 1 or 2
Is positioned by a V-groove substrate 9 and fixed to a V-groove type optical fiber holding case 8 by an adhesive 10 and an optical fiber fixing plate 11, whereas the ferrule 13 is made of an optical fiber 1 or 2. Is realized 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 temperature change of the connection loss of the connection portions of the embodiments 2-1 to 2-3 (FIGS. 17 to 22 and the connection portions of the embodiments 1-1 to 1-4. The characteristics shown in the figure are the number of samples of the connection part of the embodiment 2-1.
0 (5 in FIG. 17 and 5 in FIG. 18 having the worst variation, the characteristics of this embodiment 2-2, 2
The number of samples at the connection portion of No.-3 was 24 (6 in FIG. 19, FIG.
0, 6 in FIG. 21, 6 in FIG. 22)
The characteristics of the sample having the worst variation in the number of samples of the connection portion of the embodiment examples 1-1 and 1-2 (1 in FIG. 8)
0, 10 in FIG. 9 with the worst variation, 20 samples (5 in FIG. 10, FIG. 11 (five in FIG. 12, five in FIG. 12, and five in FIG. 13) with the worst variation. The fiber 1 is 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
The addition concentration is 1000 ppm), the fiber 2 is a silica fiber (the core refractive index is up to 1.5, the mode field radius is 4.5 μm, and the coating is a UV resin), and 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 connection portions of the embodiment examples 2-2 and 2-3 have excellent temperature characteristics and can realize a connection portion having thermal stability.

In the above embodiment, the optical fiber holding case 8 and the ferrule 13 are made of glass. However, similar results are obtained by using plastic.

(Third Embodiment) Tables 2 and 3 collectively show a third embodiment of the present invention.

[0147]

[Table 2]

[0148]

[Table 3]

As the non-quartz fiber 1, there are: 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 (Table 2 displays the non-silica fiber B) 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 In based fluoride fiber (Table 2 displays the non-silica fiber C) 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: 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.

The above non-quartz fibers A, B, C,
In D, Er (additional concentration: 1000 pp) was used as a rare earth element.
m), Pr (additional concentration 500 ppm), Tm (additional concentration 2000 ppm), Ho (additional concentration 1000 ppm),
Yb (additional concentration 500 ppm), Tb (additional concentration 20 ppm)
00 ppm), Nd (additional concentration 1000 ppm), Eu
(Additional concentration: 2000 ppm) and those not added. Further, 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: 1.5), and the connection mode was any of Embodiments 1 to 6.

As shown in Tables 2 and 3, by using the connection method of the present invention, a non-quartz fiber could be connected 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], and in the chalcogenide glass fiber, θ ₁ <8 [de]
g], it was not possible to achieve a return loss of 60 dB or more, and it was confirmed that an angle θ ₁ larger than this value was necessary to achieve a return loss of 60 dB or more.

Embodiment Examples 1-1 to 1-4 and 2-1
The optical fiber amplifier shown in FIG. 14A was configured using the connections shown in FIGS. Reference numerals 17-1, 17-2
Is an excitation light source section for generating excitation light to the optical fiber 1;
As an excitation light source for the r-doped In-based fluoride fiber 1, an Nd-YLF laser having an oscillation wavelength of 1.047 μm (each output was 500 mW) was used. Reference numerals 18-1 and 18-2 denote multiplexing sections for multiplexing the signal light and the pump light generated in 17-1 and 17-2, and 19-1 and 19-2 denote optical isolators for suppressing oscillation of the optical amplifier. It is. As the optical fiber denoted by reference numeral 1, a Pr-doped fiber was applied. The signal gain of the optical fiber amplifier was 30 dB or more, and no ghost occurred in the optical fiber amplifier. In addition, as shown in the table, it was confirmed that the connection portion was a practical optical fiber amplifier having no lifetime problem.

Fourth Embodiment In the first and second embodiments, the connection between the non-quartz fiber and the silica fiber has been described. In the eighth embodiment, however, the connection between the non-quartz fibers made of two different glasses is used. Will be described.
As the non-quartz fibers 1 and 2 used, any one of the four non-quartz fibers A, B, C and D described in the third embodiment was used. In addition, Er-added rare earth elements were used. Table 4 shows the results.

[0154]

[Table 4]

As shown in Table 4, non-quartz fibers could be connected with low loss and low reflection by using the connection method of the present invention.

According to the results of the above-mentioned Embodiment 4, the present invention provides a very low loss and low reflection connection between a non-quartz fiber and a non-quartz fiber made of two different glasses. It was confirmed that it was effective. Further, an optical fiber amplifier was constituted by the amplifier fiber using the connection portion of the present embodiment. However, Er was used as the rare earth element, and as shown in Table 4, it was confirmed that the connection part was for a practical optical fiber amplifier having no life problem.

Fifth Embodiment A fifth embodiment will be described with reference to FIGS. 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 different from the embodiments 1-4 and 2-3.
Of the ferrule 13-1 or 13-2 are connected to the adhesive storage grooves 15-1 and 15-2.
2 is a connecting portion using the adhesive reservoir grooves 16-1 and 16-2 for both of them. In the present embodiment, the connecting surface 12- of the V-groove type optical fiber holding housing 8-1 or 8-2 is used. 1,12-2
The connection was made by using an adhesive reservoir groove 15 on one side and an adhesive reservoir groove 16 on one of the connection surfaces 14-1 and 14-2 of the ferrule 13-1 or 13-2.

The optical fiber denoted 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 added concentration: 100
0 ppm), 2 is a silica-based fiber (core refractive index: １1.
5, mode field radius: 4.5 μm, coating: UV resin), 8-1 and 8-2 are V-groove type optical fiber holding housings for holding the ends of the optical fibers 1 and 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 case 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 optical fiber holding case 8-
An adhesive reservoir groove 15 is formed in the first connection surface 12-1.

Further, reference numeral 13 in FIGS.
Reference numerals -1 and 13-2 denote ferrules used as optical fiber holding housings (Er-doped In-based 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-
2). Connection surface 14-1 of ferrule 13-1
Is formed with an adhesive reservoir groove 16.

FIG. 24 and FIG. 25 of this embodiment show that the adhesive layer 5 is provided only on the connection end faces 12-1 and 12-2 or 14-1 and 14-2 which do not include the connection faces of the optical fibers 1 and 2. Therefore, the V-groove type optical fiber holding housings 8-1 and 8-2 to which the optical fibers 1 and 2 are fixed or the ferrule 13-
After the cores 1 and 13-2 are aligned so that the connection loss between the optical fibers 1 and 2 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 a capillary is provided at the interface. Using the phenomenon, the ultraviolet curing adhesive 5 was injected from the side surfaces of the V-groove type optical fiber holding casings 8-1 and 8-2 or the ferrules 13-1 and 13-2. The adhesive 5 is provided in an adhesive reservoir groove 15.
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 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 a V-groove type optical fiber holding case 8 is formed at the interface using capillary action. -1, 8-2 or ferrules 13-1, 13-2
The epoxy UV-curable adhesive 5 and the silicone UV-curable adhesive 7 were injected from the side of the above. The epoxy UV-curable adhesive 5 and the silicone UV-curable adhesive 7 were easily separated from each other by the groove 15 or 16 for storing the adhesive.

The optical fiber 1 and the silica-based fiber 2 are connected to the respective connection end faces 12-1, 12-2 or 14-1.
Θ ₁ = 4 [deg] with respect to the vertical axes of −1 and 14-2,
θ ₂ was kept at 4.1 [deg]. This connection (when the V-groove type optical fiber holding case 8 is used and when the ferrule 1 is used)
3), the connection loss between the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 is 0.15.
Connection was possible at 5 dB or less. However, the connection loss was measured at 1.3 μm where the Er-doped In-based fluoride fiber 1 did not absorb Er ions.

The return loss measured from the Er-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 6
0 dB or more (both in the case of using the V-groove type optical fiber holding case 8 and in the case of using the ferrule 13) (a commercially available return loss measuring instrument was used for measurement, the measurement wavelength was 1.3 μm, The measuring device cannot measure the return loss of 60 dB or more, and the connection portion exhibits high-performance and low-reflection characteristics higher than the measuring range of the measuring device).

In the above description, an Er-doped In-based fluoride fiber has been described. However, other Zr-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (such as rare earth elements Er, Pr, Tm, etc. The same good connection as described above could be realized by setting the angle θ ₁ of the Zr-based fluoride fiber to 3 degrees or more, the telluride-based fiber to 8 degrees or more, and the chalcogenide-based fiber to 8 degrees or more. .

Further, a silica fiber was connected to both ends of a Pr-doped In-based fluoride fiber by the connection method shown in FIGS. 24 to 27, and an optical fiber amplifier shown in FIG. 14 was formed. Reference numerals 17-1 and 17-2 denote pumping light sources for generating pumping light to the optical fiber 1. Nd-YLF lasers having an oscillation wavelength of 1.047 μm (each output) serve as a pumping light source for the Pr-doped In-based fluoride fiber 1. Was 500 mW). 18-1 and 18-2 are signal lights and 17-1 and 17-2.
Multiplexing section for multiplexing the pump light generated in step 19-1, 19
Reference numeral -2 denotes 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 (all the embodiments shown in FIGS. 24 to 27) are applied. Optical fiber 1 and silica-based fiber and connection end faces 12-1, 12-2 or 14-1, 14-
2 with respect to the vertical axis are θ ₁ = 4 [deg], θ ₂ =
It was set to 4.1 [deg]. By using the connecting portions shown in FIGS. 24 to 27, a signal gain of the optical fiber amplifier of 30 dB or more was realized, and no ghost occurred in the optical fiber amplifier. Further, the life of the optical fiber amplifier (measured by operating at a signal gain of 33 dB at 1.30 μm) measured using the conventional technology (prior arts 2, 3, 4, and 5) was 400 hours at the maximum. The life of the optical fiber amplifier to which the connecting portions (all shown in FIGS. 17 to 22) of the embodiment examples 2-1 to 2-3 are applied is 200.
0 hr or more, and the conventional technology (conventional example 2,
The problem that the optical adhesive deteriorates and the connecting portion is broken, which could not be solved in 3, 4, 5), can be solved, and a highly reliable optical fiber amplifier using a non-quartz fiber can be constructed.

In the above-described embodiment, the optical fiber holding case 8 and the ferrule 13 are made of glass. However, similar results can be obtained by using plastic.

(Embodiment 6) Embodiment 6 will be described with reference to FIGS. 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 different from the embodiments 1-4 and 2-3.
And a line-shaped adhesive reservoir groove 15-1, 15-2 on the connection surface 14-1, 1, 2 of the ferrule 13-1 or 13-2.
4-2 is a connecting portion using the adhesive reservoir grooves 16-1 and 16-2. In the present embodiment, the connecting surface 12- of the V-groove type optical fiber holding housing 8-1 or 8-2 is used. 1 and 12-2, the adhesive reservoir groove 15 is provided with a concentric adhesive reservoir groove 2.
The connection with the one with 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-based fiber (core refractive index: ~
1.5, mode field radius: 4.5 μm, coating: U
V-1), 13-1 and 13-2 denote ferrules used as optical fiber holding housings (Pr-doped In-based fluoride fiber 1 and quartz-based fiber 2 are adhesives 10 (acrylic UV adhesive is used)) Using glass ferrule 1
3-1 and 13-2). The connection surface 14-1 of the ferrule 13-1 is formed with a concentric adhesive reservoir groove 21.

In the structure of this embodiment shown in FIG. 28, the adhesive layer 5 is connected to the connection end surface 14 not including the connection surface of the optical fibers 1 and 2.
-1 and 14-2, the ferrules 13-1 and 13-2 to which the optical fibers 1 and 2 are fixed are connected to the optical fiber 1 only.
After adjusting the connection loss so that the connection loss of
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 connected to the connection end surface 14-1 not including the connection surfaces of the optical fibers 1 and 2.
And 14-2 only. In addition, the silicone adhesive layer 7
Is a connection end surface 14-1 including a connection surface 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, and the connection loss between the optical fibers 1 and 2 is lost. Of the connection end faces 14-1 and 14
After the alignment and alignment, the connection end surfaces 14-1 and 14-2 not including the connection surfaces of the optical fibers 1 and 2 are epoxy-bonded from the side surfaces of the ferrules 13-1 and 13-2 using the capillary phenomenon. It was produced by injecting an ultraviolet curing adhesive 5. The epoxy-based UV-curable adhesive 5 and the silicone-based UV-curable adhesive 7 were easily separated from each other by the adhesive reservoir groove 21 in the region into which the epoxy-based UV-curable adhesive 5 was 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.
Θ1 = 4 [deg] with respect to the vertical axes of −1 and 14-2,
θ ₂ was kept at 4.1 [deg]. This connection (when the V-groove type optical fiber holding case 8 is used and when the ferrule 1 is used)
3), the connection loss between the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 0.11.
Connection was possible at 1 dB or less. However, the splice loss was measured at 1.2 μm where the Pr-doped In-based fluoride fiber 1 did not absorb Er ions.

The return loss measured from the Pr-doped In-based fluoride fiber 1 and the quartz-based fiber 2 was 6
0 dB or more (both in the case of using the V-groove type optical fiber holding case 8 and in the case of using the ferrule 13). The measuring device cannot measure the return loss of 60 dB or more, and the connection portion exhibits high-performance and low-reflection characteristics higher than the measuring range of the measuring device).

Although the above description has been made using the Pr-doped In-based fluoride fiber, other Zr-based fluoride fibers, telluride-based fibers, and chalcogenide-based fibers (each doped with a rare earth element Er, Pr, Tm, etc.) are used. The same good connection as above can be realized by setting the angle θ ₁ to 3 degrees or more of Zr-based fluoride fiber, 8 degrees or more of telluride-based fiber, and 8 degrees or more of chalcogenide-based fiber. .

Further, a silica-based fiber was connected to both ends of the Pr-doped In-based fluoride fiber by the connection method shown in FIGS. 28 and 29, and the optical fiber amplifier shown in FIG. 14 was formed. Reference numerals 17-1 and 17-2 denote pumping light sources for generating pumping light to the optical fiber 1. Nd-YLF lasers having an oscillation wavelength of 1.047 μm (each output) serve as a pumping light source for the Pr-doped In-based fluoride fiber 1. Was 500 mW). 18-1 and 18-2 are signal lights and 17-1 and 17-2.
Multiplexing section for multiplexing the pump light generated in step 19-1, 19
Reference numeral -2 denotes 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 (all illustrated in FIGS. 28 and 29) are applied. The angle of the optical fiber 1 and the silica-based fiber with respect to the vertical axis of the connection end faces 14-1 and 14-2 is θ.
₁ = 4 [deg] and θ ₂ = 4.1 [deg].

By using the connecting portions shown in FIGS. 28 and 29, a signal gain of the optical fiber amplifier of 30 dB or more was realized, and no ghost occurred in the optical fiber amplifier. In addition, the conventional technology (conventional examples 2, 3,
Life of an optical fiber amplifier constructed using (4, 5) (measured by operating at a signal gain of 33 dB at 1.30 μm)
Was 400 hours at the maximum, while the life of the optical fiber amplifier to which the present embodiment was applied was confirmed to be 2000 hours or longer.
However, the problem that the optical adhesive deteriorates and the connection part is broken, which cannot be solved by the above, can be solved, and a highly reliable optical fiber amplifier using a non-quartz fiber can be constructed.

In the above embodiment, the ferrule 13 is made of glass, but the same result can be obtained by using plastic. Further, in the present embodiment, the concentric adhesive storage groove 21 is provided on the connection end face of the ferrule 13, but the concentric adhesive storage groove is provided on the connection end face of the V-groove optical fiber holding housing 8. Of course, the same result can be obtained.

In the first to fourth embodiments described above, a fiber doped with a rare earth element 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 compositions other than the glass compositions of the system fluoride fiber, the In system fluoride fiber, the chalcogenide glass fiber, and the telluride glass fiber are also effective. In addition, although the embodiment has been described with respect to two types of the shape of the groove for the adhesive reservoir, that is, a line shape and a concentric shape, the purpose of this groove is to include “the adhesive layer 5 includes the connection surface between the optical fibers 1 and 2. No connection end faces 12-1 and 12-2 or 14-1
Or 14-2 only "or" the epoxy-based adhesive layer 5 is provided with the connection end face 12 not including the connection face between the optical fibers 1 and 2 ".
-1 and 12-2 or 14-1 and 14-2, 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. 2), and other shapes may be used as long as the shape satisfies this purpose. Although an epoxy-based adhesive layer was used as the adhesive layer 5, similar results can be obtained with other adhesives such as an acrylic adhesive.

[0178]

As described above, according to the present invention,
Connect the connection end face of the non-quartz fiber to the connection end face of the silica fiber so that no optical adhesive is present, or connect the connection end face of the non-quartz fiber to the connection end face of the silica fiber with a silicone optical adhesive. The present invention provides an optical fiber connecting portion for connecting a non-quartz optical fiber and a silica fiber with low loss and low reflection by preventing the connecting portion from being damaged due to deterioration of the optical adhesive by connecting through the optical fiber. And a highly reliable optical fiber amplifier using the optical fiber connecting portion can be constructed.

[Brief description of the drawings]

FIG. 1 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention.

FIG. 2 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention, in which an adhesive reservoir groove is not formed on a connecting surface of an optical fiber holding housing. Is shown.

FIG. 3 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention, in which an adhesive reservoir groove is formed on a connecting surface of an optical fiber holding housing. Is shown.

4A and 4B are diagrams for explaining the shape of an adhesive reservoir groove formed on an adhesive surface of an optical fiber holding case applied to the optical fiber connecting portion of the present invention, wherein FIG. FIG. 3B is a side view of the holding housing, and FIG. 3B is a front view corresponding to the side view of FIG. 3A as viewed from the connection end surface of the optical fiber holding housing, and is a line-shaped adhesive applied to the configuration of FIG. FIG. 7C is a front view of the optical fiber holding housing seen from the connection end face corresponding to the side view of FIG. 7A and is formed concentrically with the axis of the optical fiber. Fig. 6 shows the groove for the stored adhesive.

FIG. 5 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention.

FIG. 6 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention.

FIG. 7 is a schematic side view for explaining a schematic configuration of an optical fiber connecting portion based on the present invention.

8A and 8B show a schematic configuration of an optical fiber connecting portion based on the present invention, wherein 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 the optical fiber holding housing. FIG.

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 surface of the optical fiber holding housing. FIG.

10A and 10B show a schematic configuration of an optical fiber connecting portion based on 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 surface of the optical fiber holding housing. FIG.

11A and 11B show a schematic configuration of an optical fiber connecting portion based on the present invention, wherein 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 the optical fiber holding housing. FIG.

FIGS. 12A and 12B show a schematic configuration of an optical fiber connecting portion according to the present invention, in which 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 the optical fiber holding housing. FIG.

FIGS. 13A and 13B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein 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 the optical fiber holding housing. FIG.

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

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

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

FIGS. 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. FIG.

FIGS. 18A and 18B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 18A is a side view showing the entire optical fiber connecting portion, and FIG. FIG.

19A and 19B show a schematic configuration of an optical fiber connecting portion based on 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 the optical fiber holding housing. FIG.

FIGS. 20A and 20B show a schematic configuration of an optical fiber connecting portion based on the present invention, wherein FIG. 20A is a side view showing the entire optical fiber connecting portion, and FIG. FIG.

FIGS. 21A and 21B show a schematic configuration of an optical fiber connecting portion based on the present invention, wherein FIG. 21A is a side view showing the entire optical fiber connecting portion, and FIG. FIG.

FIGS. 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. FIG.

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

24 (a) is a side view showing the entire optical fiber connection part, and FIG. 24 (b) is a side view showing the connection end face of the optical fiber holding case. FIG. FIG.

FIGS. 25A and 25B show a schematic configuration of an optical fiber connecting portion based on the present invention, wherein FIG. 25A is a side view showing the entire optical fiber connecting portion, and FIG. FIG.

26A and 26B show a schematic configuration of an optical fiber connecting portion based on 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 the optical fiber holding housing. FIG.

FIGS. 27A and 27B show a schematic configuration of an optical fiber connecting portion according to the present invention, wherein FIG. 27A is a side view showing the entire optical fiber connecting portion, and FIG. FIG.

28 (a) is a side view showing the entire optical fiber connecting portion, and FIG. 28 (b) is a side view showing the connecting end face of the optical fiber holding case. FIG. FIG.

29 (a) is a side view showing the entire optical fiber connecting portion, and FIG. 29 (b) is a side view showing the connecting end face of the optical fiber holding case. FIG.

FIG. 30 is a schematic side view for explaining a conventional connection method between a non-quartz fiber and a quartz fiber, and FIG. 30 (a) shows a case where an optical adhesive is not interposed in a fiber connection surface (conventional examples 1 and 2). (B) and (b) show a case where an optical adhesive is interposed in the fiber connection surface (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 connection method.

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

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

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Non-quartz fiber 2 Quartz fiber (non-quartz fiber composed of glass different from non-quartz fiber 1 in Embodiment 4) 3-1 and 3-2 Light holding end of optical fiber 1 or 2 respectively Fiber holding case 4-1, 4-2 Connection end surface of optical fiber holding case 3-1, 3-2 5 Adhesive (adhesive layer) or optical adhesive (optical adhesive layer) 6-1, 6-2 Adhesion Reservoir groove 7 Silicone-based adhesive (silicone-based adhesive layer) 8-1, 8-2 V-groove type optical fiber holding case 9-1, 9-2 V-groove substrate 10 Adhesive 11-1, 11-2 Optical fiber fixing plate 12-1, 12-2 V-groove type optical fiber holding case 8-
Connection end faces of 1, 8-2 13-1, 13-2 Ferrules 14-1, 14-2 Connection end faces of ferrules 12-1, 12-2 15-1, 15-2 V-groove type optical fiber holding housing 8 −
Adhesive reservoir grooves 16-1, 16-2 formed on connection end faces 12-1, 12-2 of 1, 8-2 Connection end faces 14-1, 14-2 of ferrules 12-1, 12-2 Adhesive reservoir groove formed on top 17-1, 17-2 Excitation light source 18-1, 18-8 Combiner 19-1, 19-2 Optical isolator 20-1, 20-2 Connection part of the present invention 21 Concentric adhesive reservoir groove 22 Dielectric film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuo Fujiura 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (16)

[Claims] 1. A first optical fiber and a second optical fiber which are glass compositions different from each other, at least one of which is a non-quartz fiber for optical amplification, and a second optical fiber holding an end of the first optical fiber. A second optical fiber holding case for holding an end of the second optical fiber, and an optical axis of the first optical fiber and the second optical fiber holding case.
The connection end face of the first optical fiber holding casing and the connection end face of the second optical fiber holding casing are made of adhesive in a state where the optical axes of the optical fibers are aligned so as to coincide with each other. In an optical fiber connection portion connected via an adhesive layer, at least a connection end of the first optical fiber located at a connection end face of the first optical fiber holding housing and a connection end of the second optical fiber holding housing. An optical fiber connection section, wherein an adhesive layer made of the adhesive is not interposed between the second optical fiber and the connection end of the second optical fiber located on the connection end face. 2. One or both of the first optical fiber holding housing and the second optical fiber holding housing have a groove near the end of the first optical fiber and surrounding the end. Then, with the groove as a boundary, a region where the end of the first optical fiber is located is defined as a non-bonding region where no adhesive layer made of the adhesive is interposed, and a region where the optical fiber is not located is formed from the adhesive. As an adhesion area in which an adhesion layer is interposed, the adhesion area of the first optical fiber holding casing and the second optical fiber holding casing are adhered and connected via the adhesion area. Item 2. The optical fiber connection section according to item 1. 3. The refractive index n of the core of the first optical fiber.
_{If 1} and the refractive index n ₂ of the core of the second optical fiber is different, the first optical fiber angle to the normal of the connecting surface between the second optical fiber and the first optical fiber It provided obliquely with theta _1, also inclined at different angles theta ₂ is the second optical fiber and an angle theta ₁ with respect to the perpendicular of the connection surface between the second optical fiber and the first optical fiber The relationship between the angle θ ₁ and the angle θ ₂ is given by: The optical fiber connection according to claim 1, wherein the optical fiber connection part satisfies the Snell's formula. 4. In order to achieve a predetermined return loss, θ ₁ and θ ₂ are given by: (Where R is the return loss, n _UV is the refractive index of the adhesive, λ is the signal wavelength, ω _1,2 is the spot size of the first optical fiber or the second optical fiber, θ _1,2 is θ optical fiber connection part according to claims 1 and satisfies _one or theta ₂₎ to any one of 3. 5. One of the first optical fiber and the second optical fiber is selected from the group consisting of a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, and a telluride glass fiber. The optical fiber according to any one of claims 1 to 4, wherein the optical fiber is a selected optical fiber. 6. The optical fiber of claim 1, wherein the selected optical fiber is
Is provided at an angle θ with respect to the perpendicular to the connection surface between the optical fiber and the second optical fiber, and the angle θ is 8 degrees when the selected optical fiber is a telluride-based fiber. 6. The light according to claim 5, wherein the angle is 8 degrees or more for a chalcogenide-based fiber; 3 degrees or more for a Zr-based fluoride fiber; and 4 degrees or more for an In-based fluoride fiber. Fiber connection. 7. The optical fiber connection according to claim 5, wherein a rare earth element is added to the selected optical fiber. 8. A first optical fiber, a second optical fiber having a glass composition different from that of the first optical fiber, and a first optical fiber holding case for holding an end of the first optical fiber. A body, and a second optical fiber holding case for holding an end of the second optical fiber, wherein an optical axis of the first optical fiber coincides with an optical axis of the second optical fiber. In a state where the connection is made such that the connection end face of the first optical fiber holding casing and the connection end face of the second optical fiber holding casing are connected, at least the first Between the connection end of the first optical fiber located on the connection end face of the optical fiber holding housing and the connection end of the second optical fiber located on the connection end face of the second optical fiber holding housing. Is characterized by the interposition of an adhesive layer made of a silicone-based adhesive. Optical fiber connection part to. 9. The silicone adhesive according to claim 8, wherein the silicone adhesive is an ultraviolet-curable silicone adhesive.
2. The optical fiber connection according to claim 1. 10. The first optical fiber holding case has a groove surrounding the end of the first optical fiber near the end of the first optical fiber, and the first optical fiber is bounded by the groove. The first optical fiber is located at the end of the fiber and is in contact with an adhesive layer made of the silicone-based adhesive, and the second adhesive area is in contact with an adhesive layer made of another adhesive. The second optical fiber holding housing is provided on a connection end surface of the holding housing, the second optical fiber holding housing has a groove surrounding the end near the end of the second optical fiber, and with the groove as a boundary, A first optical fiber in which an end of the second optical fiber is located and an adhesive layer made of the silicone adhesive is in contact
The second contact area where the adhesive area of
Is provided on the connection end surface of the second optical fiber holding housing, and the second bonding region of the first optical fiber holding housing and the second bonding area of the second optical fiber holding housing are provided. The optical fiber connector according to claim 8, wherein the optical fiber connector is connected to the bonding area. 11. When the refractive index n ₁ of the core of the first optical fiber is different from the refractive index n ₂ of the core of the second optical fiber, the first optical fiber is the first optical fiber. Is provided at an angle θ ₁ with respect to a perpendicular to a connecting surface between the first optical fiber and the second optical fiber, and the second optical fiber is a connection between the first optical fiber and the second optical fiber. The angle θ ₁ is provided at an angle θ ₂ different from the angle θ ₁ with respect to the perpendicular to the surface. The relationship between the angle θ ₁ and the angle θ ₂ is given by The optical fiber connection according to any one of claims 8 to 10, which satisfies the Snell's formula. 12. To achieve a predetermined return loss,
The θ ₁ and the θ ₂ are given by: (Where R is the return loss, n _UV is the refractive index of the adhesive, λ is the signal wavelength, ω _1,2 is the spot size of the first optical fiber or the second optical fiber, θ _1,2 is θ optical fiber connecting portion according to any one of claims 8 to 11, characterized in that meet _one or theta _2). 13. The first optical fiber and the second optical fiber.
9. The optical fiber according to claim 8, wherein one of the optical fibers is an optical fiber selected from the group consisting of a Zr-based fluoride fiber, an In-based fluoride fiber, a chalcogenide-based glass fiber, and a telluride glass fiber. 13. The optical fiber connection according to any one of claims 12 to 12. 14. The selected optical fiber is provided to be inclined at an angle θ with respect to a perpendicular to a connecting surface between the first optical fiber and the second optical fiber, and the angle θ is 8 degrees or more when the selected optical fiber is a telluride-based fiber; 8 degrees or more when a chalcogenide-based fiber; 3 degrees or more when a Zr-based fluoride fiber; The optical fiber connection according to claim 13, wherein the temperature is equal to or higher than the degree. 15. The optical fiber connection according to claim 13, wherein a rare earth element is added to the selected optical fiber. 16. An optical amplifier comprising at least two kinds of optical fibers and an optical fiber connecting part for connecting said at least two kinds of optical fibers, wherein said optical fiber connecting part is one of claims 1 to 15. An optical amplifier, characterized in that it is the optical fiber connection section described in the paragraph.