JPH11109143A - Rare earth element doped optical fiber and broadband optical fiber amplifier using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth element-doped optical fiber having high gain, wide band, low noise figure characteristics, low power consumption and low cost, and a wide band optical fiber amplifier using the same. . A cladding 1 of circular cross-sectional shape of the refractive index n _c
5, erbium (Er), phosphorus (P) and aluminum (A) having a high refractive index n ₀₁ (n ₀₁ > n _c ) having a diameter D
1) a first core 11 made of quartz glass (SiO ₂ ) co-doped with a low refractive index nm ₁ (nm ₁ <n ₀₁ ) having a thickness S ₁ and an outer periphery of the first core 11. And a high refractive index n ₀₂ having a thickness of W on the outer periphery of the first intermediate layer.
A second core 13 made of quartz glass (SiO ₂ ) co-doped with (n ₀₂ ≧ n ₀₁ ) erbium (Er), aluminum (Al), and germanium (Ge);
The outer periphery of the core, the low refractive index in the thickness S ₂ n _m2 (n _m2 <
n ₀₂ ) of the second intermediate layer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare-earth-doped optical fiber suitable for wavelength division multiplexing transmission and a broadband optical fiber amplifier using the same.

[0002]

2. Description of the Related Art In recent years, with the active research and development of wavelength division multiplexing (WDM) technology, an increase in the bandwidth of an optical fiber amplifier has become an important issue. As the broadband optical fiber amplifier, for example, a silica-based fiber having a core doped with erbium (Er) and co-doped with aluminum (Al) at a high concentration is used, and is configured to be pumped with pumping light having a wavelength of 0.98 μm. There is an Er-Al co-doped optical fiber amplifier. Erbium (Er) and aluminum (A
1) a silica fiber having a core co-doped with a silica fiber and a silica fiber having a core co-doped with erbium (Er), aluminum (Al) and phosphorus (P) cascade-connected. There is a hybrid optical fiber amplifier configured to propagate pump light and signal light.

FIGS. 9A to 9C are diagrams showing a configuration example of a hybrid optical fiber amplifier. As shown in (a), the gain of the silica-based fiber 2 having the core 1 in which erbium (Er) and aluminum (Al) are co-doped has a tendency shown in the band where the wavelength is 1.53 μm to 1.55 μm. Erbium (Er) as shown in FIG.
The gain of the silica-based fiber 4 having the core 3 co-doped with aluminum (Al) and phosphorus (P) has a wavelength of 1.55.
There is a tendency shown in the band from μm to 1.57 μm. However, as shown in (c), the gain of the silica-based fiber 5 in which these silica-based fibers 2 and 4 are cascaded shows a high value over a wavelength of 1.53 μm to 1.57 μm. It is possible to widen the bandwidth of a hybrid optical fiber amplifier using this.

[0004]

However, the conventional broadband optical fiber amplifier has the following problems. In the former Er-Al co-doped optical fiber amplifier described above, the 1 dB bandwidth at the time of a minute input signal is about 15 nm, and it is extremely difficult to realize a 1 dB bandwidth of about 30 nm. In the latter hybrid optical fiber amplifier, the 1 dB bandwidth can be made wider than that of the Er-Al co-doped optical fiber amplifier. However, since two kinds of silica fibers must be cascaded, The configuration is complicated, and the cost increases due to the increase in the number of parts and man-hours. Further, the noise figure is degraded due to the connection loss at the cascade connection.

Further, in order to realize a wide band characteristic at a high gain, the length of two kinds of silica-based fibers must be at least 15 mm.
m is required, but when these are cascaded, the distance becomes at least 30 m, so that the power of the excitation light must be increased. For this purpose, a high-output pumping semiconductor laser is required, but the price increases and the power consumption increases. Accordingly, it is an object of the present invention to provide a rare earth element-doped optical fiber having high gain, wide band, low noise figure characteristics, low power consumption and low cost, and a wide band optical fiber amplifier using the same. is there.

[0006]

The present invention fulfills the above objects.
The index of refraction n_cAbbreviation of cladding with circular cross section
In the center, a high refractive index n of diameter D₀₁(N₀₁> N_c) Elbi
(Er), phosphorus (P) and aluminum (Al)
Quartz glass (SiO_Two) Having a first core
And a thickness S on the outer periphery of the first core.₁Low refractive index n_m1
(N_m1<N₀₁) Comprising a first intermediate layer, wherein the first intermediate layer
On the periphery of the layer, a high refractive index n of thickness W₀₂(N ₀₂≧ n₀₁D)
Rubium (Er), aluminum (Al) and germanium
Glass (SiO) co-doped with_TwoConsisting of
A second core having a thickness S on an outer periphery of the second core;_Two
Low refractive index n_m2(N_m2<N₀₂) Having a second intermediate layer
To provide a rare earth element-doped optical fiber characterized by the following features:
You.

[0007] According to the above configuration, since one optical fiber cross section has two core regions through which the signal light and the pump light propagate, the signal light and the pump light are substantially equally distributed to each core region. Can be propagated, and the wavelength multiplexing number is 8
Even if the number of waves increases to 16 waves, 32 waves, and 64 waves, there is no danger of inducing a non-linear effect. That is, since the optical fiber has a structure having two core regions capable of obtaining a large effective core area, there is no possibility of inducing a nonlinear effect.

Further, the present invention in order to achieve the above object, the approximate center of the cladding of a circular cross-sectional shape consisting of a refractive index n _c of fluorine (F) quartz glass doped with (SiO _2), the diameter D High Erbium (Er), aluminum (Al) and germanium (G) having a refractive index n ₀₁ (n ₀₁ > n _c )
e) a first core made of quartz glass (SiO ₂ ) co-doped with phosphorus, and a low-refractive-index n _m1 (nm ₁ <n ₀₁ ) low-refractive-index layer S ₁ having a thickness of S _1. (P) and a first intermediate layer made of quartz glass (SiO ₂ ) to which fluorine (F) is added, and a high refractive index n having a thickness of W is provided around the first intermediate layer.
₀₂ (n ₀₂ ≧ n ₀₁ ) quartz glass (SiO) co-doped with erbium (Er), phosphorus (P) and aluminum (Al)
A second core formed of _2), added to the outer periphery of the second core, phosphorus of a low refractive index in the thickness _{S 2 n m2 (n m2 <} n 02) and (P) fluorine (F) Quartz glass (Si
A rare earth element-doped optical fiber having a second intermediate layer made of O ₂ ).

Further, the present invention has been developed to achieve the above object.
For this reason, pump light of 0.98 μm band or 1.48 μm band is used.
Emitted pump light source, 1.5 μm band signal light and pump
A multiplexer for multiplexing the excitation light emitted from the light source, and a refraction
Rate n_cApproximately at the center of the circular cross section of the cladding,
High refractive index n₀₁(N₀₁> N_c) Erbium (Er) and Li
Glass with co-doped aluminum (P) and aluminum (Al)
(SiO_Two), The first core comprising:
The thickness S₁Low refractive index n_m1(N_m1<N ₀₁)of
A first intermediate layer having a thickness on an outer periphery of the first intermediate layer;
High refractive index n of W₀₂(N₀₂≧ n₀₁) Erbium (Er)
With aluminum (Al) and germanium (Ge)
Quartz glass (SiO_TwoHaving a second core consisting of
And a thickness S on the outer periphery of the second core._TwoLow refractive index n_m2
(N_m2<N₀₂) Rare earth element addition having a second intermediate layer
An optical fiber, wherein the rare earth element-doped optical fiber
The multiplexed light from the multiplexer is propagated to the rare earth element.
The amplified signal from the output end side of the element-doped optical fiber.
A broadband optical filter characterized by extracting light
An iva amplifier is provided.

[0010]

FIG. 1A is a cross-sectional view showing a first embodiment of a rare earth element-doped optical fiber according to the present invention, and FIG. 1B is a sectional view showing a radial refraction in the cross section. It is a figure showing an intensity distribution. This rare earth element doped optical fiber 10
Has a thickness S on the outer periphery of the circular first core 11 having a diameter D.
_One annular first intermediate layer 12 is formed, an annular second core 13 having a thickness W is formed on the outer periphery of the first intermediate layer 12, and an outer periphery of the second core 13 is formed on the outer periphery of the second core 13. A rare earth element-doped multi-ring type quartz fiber having a configuration in which an annular second intermediate layer 14 having a thickness S ₂ is formed, and an annular cladding 15 is formed on the outer periphery of the second intermediate layer 14. is there.

[0011] cladding 15 is made of quartz glass having a refractive index n _c (SiO _2). The first core 11 has a high refractive index n ₀₁
(N ₀₁ > n _c ) erbium (Er), phosphorus (P) and aluminum (Al) co-doped quartz glass (Si)
O ₂ ). The first intermediate layer 12 has a low refractive index n _m1 (n
It is composed of quartz glass (SiO ₂ ) to which phosphorus (P) and fluorine (F) with _m1 <n ₀₁ ) are added. The second core 13 is made of quartz glass (SiO ₂ ) in which erbium (Er) having a high refractive index n ₀₂ (n ₀₂ ≧ n ₀₁ ), aluminum (Al), and germanium (Ge) are co-doped. The second intermediate layer 14 is made of a low refractive index _{n m2 (n m2 <n 02} ) of phosphorus (P) and fluorine (F) quartz glass doped with (SiO _2).

The relative refractive index difference Δn ₁ between the first core 11 and the clad 15 is selected from the range of 0.5% to 1.5%. Relative refractive index difference Δn between second core 13 and clad 15
₁ 'is selected from the range of 0.5% to 1.7%. The relative refractive index difference Δn between the cladding 15 and each of the intermediate layers 12 and 14
₂ is selected from the range of -0.1% to -0.3%.

In order to obtain the above-described refractive index and relative refractive index difference, the following values are selected for the amounts of the respective additives. The amount of erbium (Er) added to each of the cores 11 and 13 is selected from the range of 200 ppm to 1000 ppm. The larger the amount of addition, the more advantageous in that a high gain and a low noise figure can be obtained with a short optical fiber. It is. The amount of aluminum (Al) added to each of the cores 11 and 13 is selected from the range of 0.5% to 4.0%. The greater the amount of addition, the flatter the gain wavelength characteristic is. Is advantageous.

The amount of phosphorus (P) added to the first core 11 is as follows:
It is selected from the range of 10 mol% to 25 mol%, and the thermal expansion coefficient of the first core 11 located at the center is set to be slightly larger than the thermal expansion coefficient of each of the intermediate layers 12, 14 and the second core 13. Is advantageous in that it can be easily manufactured. The amount of germanium (Ge) added to the second core 13 is 6 m
ol% to 15 mol%, the coefficient of thermal expansion of the second core 13 is smaller than the coefficient of thermal expansion of the first core 11 and smaller than the coefficient of thermal expansion of the first intermediate layer 12. A smaller one is preferred. The amount of phosphorus (P) added to each of the intermediate layers 12 and 14 is selected to be 8 mol%. Each intermediate layer 1
The amount of fluorine (F) added in 2, 14 is 2 mol% to 3 m
ol%.

In order to increase the effective core area of the rare-earth element-doped optical fiber 10 and to distribute the signal light and the pump light into the cores 11 and 13 approximately uniformly, the diameter of the clad 15 is 125 μm. In the case of, the diameters and thicknesses D, W, S ₁ and S ₂ of the cores 11 and 13 and the intermediate layers 12 and 14 are
The following values are preferred. That is, D is 1 μm to 2 μm,
W is ₁ μm to ₂ μm, S ₁ and S ₂ are 0.5 μm to 3 μm.
Select from the range of μm. By adopting such structural parameters, the effective core area is 100 μm ^{2 to} 14 μm ^2.
It can be 0 μm ² . Thus, the influence of the nonlinear effect can be suppressed to a small number up to about 8, 16, 32, or 64 wavelength multiplexing numbers. Further, when an optical amplifier is configured using the element-doped optical fiber 10, the signal light and the pump light are distributed substantially evenly in the cores 11 and 13, and propagate therethrough, thereby realizing an optical amplifier with high efficiency and high gain. be able to.

Further, an optical amplifier having a flat gain wavelength characteristic can be obtained for the following reasons. That is, the signal light and the pump light propagated in the first core 11 are 1.55
The high gain characteristic is provided on the short wavelength side (around 1.53 μm) of the μm band, and the signal light and the pump light propagated in the second core 13 are on the long wavelength side (around 1.56 μm) of the 1.55 μm band. Provides high gain characteristics. Then, on the emission side of the optical fiber, the above two gain characteristics are superposed, and a flat characteristic of gain is obtained over a wavelength of 1.53 μm to 1.56 μm. Further, generation of cracks or cracks in the manufacturing process of the optical fiber preform and the optical fiber due to the mismatch of the thermal expansion coefficient can be suppressed.

As described above, in the first embodiment of the rare-earth element-doped optical fiber of the present invention, quartz glass is used as a base material, and various additives are added thereto to obtain predetermined characteristics. It was made. Here, FIG.
FIG. 3 is a diagram showing the relationship between the refractive index and the additive concentration (mol%) when various additives are added to quartz glass. FIG. 3 is a diagram showing the relationship between the coefficient of thermal expansion and the additive concentration (mol%) when various additives are added to quartz glass. As is clear from each figure, by adding a predetermined additive to quartz glass, its refractive index and thermal expansion coefficient can be changed.

FIG. 4A is a cross-sectional view showing a second embodiment of the rare-earth element-doped optical fiber of the present invention, and FIG. 4B shows a radial intensity distribution in the cross section. FIG. The rare earth element-doped optical fiber 20 is made of quartz glass (Si) in which cladding 25 is doped with fluorine (F).
The point that O ₂ ) is used is different from the rare-earth-element-doped optical fiber 10 of the first embodiment. Fluorine (F) of clad 25
Is selected as 1 mol%.

Fluorine (F) in quartz glass (SiO ₂ )
When is added, the refractive index can be lowered, but the coefficient of thermal expansion hardly changes. Therefore, the cores 21 and 23 and the intermediate layers 22 and 24 can be configured so that the thermal expansion coefficients thereof are substantially close to each other. Thereby, generation of cracks or cracks in the manufacturing process of the optical fiber preform and the optical fiber can be prevented. The addition of fluorine (F) to each of the intermediate layers 22 and 24 and the clad 25 is performed by adding each layer to a VAD (Vapor layer).
Hase Axial Deposition), and when sintering those layers, fluorine (F)
This can be realized by flowing a system gas.

FIG. 5A is a cross-sectional view showing a third embodiment of a rare earth element-doped optical fiber of the present invention, and FIG. 5B shows a radial intensity distribution in the cross section. FIG. The element-doped optical fiber 30 includes a first core 3
In order to make the refractive index n _{01 of 1} and the refractive index n ₀₂ of the second core 33 substantially equal, a small amount of titanium (Ti) is added to the first core 31 to control the refractive index and the coefficient of thermal expansion. This is different from the rare-earth-element-doped optical fiber 10 of the first embodiment. First
In order to increase the refractive index n ₀₁ of the core 31 only by phosphorus (P), a large amount of phosphorus (P) must be added. However, if a large amount of phosphorus (P) is added, a problem arises in the point of hygroscopicity, and a problem arises in the deOH-forming and reliability of the base material. Therefore, the amount of phosphorus (P) is suppressed, and instead, a small amount of titanium (Ti) is added to control the refractive index.

FIG. 6A is a cross-sectional view showing a fourth embodiment of the rare earth element-doped optical fiber of the present invention, and FIG. 6B shows a radial refraction intensity distribution in the cross section. FIG. The rare-earth-element-doped optical fiber 40 has a configuration in which the material of the first core 31 and the material of the second core 33 of the rare-earth-element-doped optical fiber 30 shown in FIG.
And a second core 43. That is, the first core 41 is made of quartz glass (SiO ₂ ) to which erbium (Er), aluminum (Al), and germanium (Ge) are co-doped. Second core 43
Is a quartz glass (S) in which erbium (Er), phosphorus (P), aluminum (Al), and titanium (Ti) are co-doped.
iO ₂ ). Each core 11, 13 and each intermediate layer 2
The thermal expansion coefficients of the first and second cores 41 and 24 are almost equal to each other, or the central first core 41 has the largest thermal expansion coefficient.
First intermediate layer 42, second core 43, second intermediate layer 44
, The coefficient of thermal expansion is gradually reduced.

In each of the above-described embodiments, each of the intermediate layers 12, 14, 22, 24, 32, and 34 has a refractive index higher than that of each of the cores 11, 13, 21, 23, 31, and 33. It is sufficient that the thermal expansion coefficient is small and the thermal expansion coefficients are substantially equal. For example, boron (B) may be added instead of fluorine (F) and phosphorus (P), and boron (B) and phosphorus (P) may be added. May be added.

FIG. 7 is a block diagram showing a broadband optical fiber amplifier using a rare earth element-doped optical fiber according to a first embodiment of the present invention. This broadband optical fiber amplifier 100 is a broadband optical fiber amplifier in the case of forward pumping, and the signal light and the pump light that are wavelength-multiplexed to the rare earth element-doped optical fibers 10, 20, 30, and 40 of the above-described embodiments. Is configured to be propagated. Signal light S
L propagates in the input side optical fiber (single mode optical fiber, dispersion shift optical fiber, or optical fiber for wavelength division multiplexing) 101,
2. The light is input into the rare-earth element-doped optical fiber 104 through the WDM coupler 103 as shown by an arrow a in the drawing.

The excitation light WL from the excitation light source (wavelength 0.98 μm or 1.48 μm band) 106 is W
The light is multiplexed by the DM coupler 103 and input into the rare-earth element-doped optical fiber 104 as shown by the arrow b in the figure. And
Excitation light W propagated in the rare-earth element-doped optical fiber 104
L, the signal light SL is amplified and output as shown by the arrow c in the figure, and the WDM coupler 107 and the optical isolator 108
Then, the light propagates through the optical fiber 109 on the output side and is output as shown by the arrow d in the figure.

FIG. 8 is a block diagram showing a second embodiment of a broadband optical fiber amplifier using a rare earth element-doped optical fiber according to the present invention. The broadband optical fiber amplifier 200 is a broadband optical fiber amplifier in the case of forward pumping, and the signal light and the pump light that are wavelength-multiplexed to the rare earth element-doped optical fibers 10, 20, 30, and 40 of the above-described embodiments. Is configured to be propagated. Signal light S
L propagates in the input side optical fiber (single mode optical fiber, dispersion shift optical fiber, or optical fiber for wavelength division multiplexing) 101,
2. The light is input into the rare-earth element-doped optical fiber 104 through the WDM coupler 103 as shown by an arrow a in the drawing.

The excitation light WL from the excitation light source (wavelength 0.98 μm or 1.48 μm band) 106 is W
The light beams are combined by the DM coupler 103 and input into the rare-earth element-doped optical fiber 104 as shown by the arrow b in the figure. further,
Excitation light source (wavelength 0.98 μm or 1.48 μm
The excitation light WL ′ from the band) 201 is also transmitted to the WDM coupler 103.
And input into the rare-earth-element-doped optical fiber 104 as shown by an arrow e in the figure. Then, the signal light SL is amplified by the pumping lights WL and WL ′ propagated in the rare-earth element-doped optical fiber 104 and output as shown by the arrow c in the figure, and is output through the WDM coupler 107 and the optical isolator 108 to the output side optical fiber 109. It propagates through the inside as shown by the arrow d in the figure and is output.

With the above operation, the wavelength 1.53 μm
The wavelength-multiplexed signal light SL of m to 1.56 μm can be amplified substantially uniformly with a gain of at least 30 dB. For example, the signal light SL having a wavelength of 1.53 μm to 1.56 μm and wavelength-multiplexed at least 32 channels at 0.8 nm intervals can be amplified and output with a substantially uniform gain. In addition, since the rare-earth-element-doped optical fiber can have an effective core area larger than 100 μm ² , the problem of waveform deterioration due to the non-linear effect does not occur even if the number of multiplexed wavelengths increases.

The following effects can be obtained by the above embodiments. Since two light propagation portions are combined in one optical fiber cross section, an optical fiber having a lower loss can be obtained as compared with a conventional hybrid cascade connection type of two types of optical fibers. As a result, high gain,
An optical amplifier having low noise figure and low power consumption characteristics can be realized at low cost. A multi-ring structure is formed by adding a thermal expansion coefficient controlling dopant to each core and the intermediate layer to balance the thermal expansion coefficients of each core and the intermediate layer. and cracking without, and since also serves as the control of the refractive index, the effective core area can be in the range of 100μm ² ~140μm ^2. Since the optical amplifier can be constituted by one kind of optical fiber, the influence of the reflected light from the connection between the optical fibers, which is a problem in the optical amplifier, can be ignored.

[0029]

As described above, according to the present invention, high gain, wide band, low noise figure characteristics, low power consumption and low cost can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of a rare-earth element-doped optical fiber of the present invention, and a drawing showing a radial refractive intensity distribution in the cross-section.

FIG. 2 is a diagram showing the relationship between the refractive index and the additive concentration (mol%) when various additives are added to quartz glass.

FIG. 3 is a diagram showing the relationship between the coefficient of thermal expansion and the additive concentration (mol%) when various additives are added to quartz glass.

FIG. 4 is a cross-sectional view showing a second embodiment of the rare-earth element-doped optical fiber of the present invention, and a diagram showing a radial refractive power distribution in the cross-section.

FIG. 5 is a cross-sectional view showing a third embodiment of a rare earth element-doped optical fiber of the present invention, and a diagram showing a radial intensity distribution in the cross section.

FIG. 6 is a sectional view showing a fourth embodiment of the rare-earth element-doped optical fiber of the present invention, and a diagram showing a radial refractive power distribution in the section.

FIG. 7 is a block diagram showing a broadband optical fiber amplifier using a rare earth element-doped optical fiber according to a first embodiment of the present invention.

FIG. 8 is a block diagram showing a second embodiment of a broadband optical fiber amplifier using a rare earth element-doped optical fiber according to the present invention.

FIG. 9 is a cross-sectional view showing an example of a conventional rare earth element-doped optical fiber.

[Explanation of symbols]

10, 20, 30, 40, 104, rare earth element-doped optical fiber 11, 21, 31, 41, first core 12, 22, 32, 42, first intermediate layer 13, 23, 33, 43, second , 24, 34, 44, second intermediate layers 15, 25, 35, 45, claddings 100, 200, broadband optical fiber amplifier 101, input side optical fiber 102, optical isolator 103, WDM coupler 106, pumping Light source 107, WDM coupler 108, optical isolator 109, output side optical fiber 201, excitation light source

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masatake Ejima 2- 13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Kagaku Kogyo Co., Ltd. Precision Functional Materials Laboratory (72) Inventor Jun Abe Isobe, Annaka-shi, Gunma 2-13-1 Shin-Etsu Chemical Industry Co., Ltd.

Claims (12)

[Claims] 1. An erbium (Er) having a high refractive index n ₀₁ (n ₀₁ > n _c ) having a diameter D, phosphorus (P), and aluminum (Al) are disposed substantially at the center of a clad having a circular cross section having a refractive index n _c. It has a first core formed of a codoped quartz glass (SiO _2), wherein the outer circumference of the first core, the thickness S ₁ of the low refractive index n _m1 (n
_m1 < _n01 ), and a high refractive index _n02 (n) having a thickness W on the outer periphery of the first intermediate layer.
₀₂ ≧ n ₀₁ ) erbium (Er) and aluminum (A
l) and a second core formed of germanium (Ge) codoped quartz glass (SiO _2), the outer periphery of the second core, the thickness S ₂ of the low-refractive index n _{m @ 2} (n
A rare earth element-doped optical fiber having a second intermediate layer _{satisfying m2} < _n02 ). 2. The method according to claim 1, wherein the first and second intermediate layers are made of quartz glass (Si) doped with phosphorus (P) and fluorine (F).
The rare-earth element-doped optical fiber according to claim 1, comprising O ₂ ). 3. The rare-earth element-doped optical fiber according to claim 2, wherein the cladding is made of silica glass (SiO ₂ ) doped with fluorine (F). 4. The optical fiber according to claim 1, wherein the first core is co-doped with titanium (Ti). 5. The refractive index n_cStone with added fluorine (F)
English glass (SiO_Two) Consisting of a circular cross-sectional shape
Approximately at the center, a high refractive index n of diameter D₀₁(N₀₁> N _cEl)
Bi (Er), aluminum (Al) and germanium
Quartz glass (SiO) co-doped with (Ge)_Two) Consisting of
And a thickness S on the outer periphery of the first core.₁Low refractive index n_m1(N
_m1<N₀₁) Quartz doped with phosphorus (P) and fluorine (F)
Glass (SiO_Two), And a high refractive index n having a thickness W on the outer periphery of the first intermediate layer.₀₂(N
₀₂≧ n₀₁) Erbium (Er), phosphorus (P) and aluminum
Quartz glass (SiO_Two)so
Having a thickness S on the outer periphery of the second core._TwoLow refractive index n_m2(N
_m2<N₀₂) Quartz doped with phosphorus (P) and fluorine (F)
Glass (SiO_TwoHaving a second intermediate layer comprising
Characteristic rare earth element doped optical fiber. 6. A 0.98 μm band or a 1.48 μm band.
An excitation light source that emits the excitation light of 1.5 μm band, and an excitation light emitted from the excitation light source.
A multiplexer for multiplexing the light emission, and a refractive index n_cAt the approximate center of the circular cross section of the cladding, the diameter
High refractive index n of D₀₁(N ₀₁> N_c) Erbium (Er)
With phosphorus and phosphorus (P) and aluminum (Al)
Glass (SiO_Two), The first core comprising:
Thickness S on the outer periphery of the core₁Low refractive index n_m1(N_m1<
n₀₁) Having a first intermediate layer, and an outer periphery of the first intermediate layer
And a high refractive index n with a thickness W₀₂(N₀₂≧ n₀₁) Erbium
(Er), aluminum (Al), and germanium (G
e) silica glass (SiO)_TwoThe second
A core having a thickness S on the outer periphery of the second core._TwoLow bow
Folding ratio n_m2(N_m2<N₀₂Rare earth element having a second intermediate layer)
An element-doped optical fiber, wherein the rare-earth-element-doped optical fiber is
Propagating the wave light, the output of the rare earth element-doped optical fiber
The amplified signal light is taken out from the end side.
A broadband optical fiber amplifier, characterized in that: 7. A 0.98 μm band or a 1.48 μm band.
An excitation light source that emits the excitation light of 1.5 μm band, and an excitation light emitted from the excitation light source.
A multiplexer for multiplexing the light emission, and a refractive index n_cAt the approximate center of the circular cross section of the cladding, the diameter
High refractive index n of D₀₁(N ₀₁> N_c) Erbium (Er)
With phosphorus and phosphorus (P) and aluminum (Al)
Glass (SiO_Two), The first core comprising:
Thickness S on the outer periphery of the core₁Low refractive index n_m1(N_m1<
n₀₁Quartz glass to which phosphorus (P) and fluorine (F) are added
(SiO_Two) Comprising a first intermediate layer comprising:
On the outer periphery of the intermediate layer, a high refractive index n having a thickness W₀₂(N₀₂≧ n₀₁)
Erbium (Er), aluminum (Al) and germanium
Quartz glass (SiO) co-doped with_Two)so
A second core having a thickness on the outer periphery of the second core.
S_TwoLow refractive index n_m2(N_m2<N ₀₂) Phosphorus (P)
Quartz glass (SiO 2)_TwoThe second
A rare earth element-doped optical fiber having an intermediate layer of
Propagating the wave light, the output of the rare earth element-doped optical fiber
The amplified signal light is taken out from the end side.
A broadband optical fiber amplifier, characterized in that: 8. The 0.98 μm band or 1.48 μm band
An excitation light source that emits the excitation light of 1.5 μm band, and an excitation light emitted from the excitation light source.
A multiplexer for multiplexing the light emission, and a refractive index n_cGlass (Si) to which fluorine (F) is added
O_Two), The diameter of which is approximately at the center of the circular cross-section
High refractive index n of D₀₁(N₀₁> N_c) Erbium (Er)
With phosphorus and phosphorus (P) and aluminum (Al)
Glass (SiO _Two), The first core comprising:
Thickness S on the outer periphery of the core₁Low refractive index n _m1(N_m1<
n₀₁Quartz glass to which phosphorus (P) and fluorine (F) are added
(SiO_Two) Comprising a first intermediate layer comprising:
On the outer periphery of the intermediate layer, a high refractive index n having a thickness W ₀₂(N₀₂≧ n₀₁)
Erbium (Er), aluminum (Al) and germanium
Quartz glass (SiO) co-doped with_Two)so
A second core having a thickness on the outer periphery of the second core.
S_TwoLow refractive index n_m2(N_m2<N₀₂) Phosphorus (P)
Quartz glass (SiO 2)_TwoThe second
A rare earth element-doped optical fiber having an intermediate layer of
Propagating the wave light, the output of the rare earth element-doped optical fiber
The amplified signal light is taken out from the end side.
A broadband optical fiber amplifier, characterized in that: 9. The 0.98 μm band or 1.48 μm band
An excitation light source that emits the excitation light of 1.5 μm band, and an excitation light emitted from the excitation light source.
A multiplexer for multiplexing the light emission, and a refractive index n_cAt the approximate center of the circular cross section of the cladding, the diameter
High refractive index n of D₀₁(N ₀₁> N_c) Erbium (Er)
, Phosphorus (P), aluminum (Al), and titanium (Ti)
Quartz glass (SiO 2)_TwoA first core comprising
Having a thickness S on the outer periphery of the first core.₁Low refractive index
n_m1(N_m1<N₀₁A) a first intermediate layer, wherein the first
On the outer periphery of the intermediate layer, a high refractive index n having a thickness W₀₂(N₀₂≧ n₀₁)
Erbium (Er), aluminum (Al) and germanium
Quartz glass (SiO) co-doped with_Two)so
A second core having a thickness on the outer periphery of the second core.
S _TwoLow refractive index n_m2(N_m2<N₀₂) With a second intermediate layer
A rare-earth element-doped optical fiber,
Propagating the wave light, the output of the rare earth element-doped optical fiber
The amplified signal light is taken out from the end side.
A broadband optical fiber amplifier, characterized in that: 10. The 0.98 μm band or 1.48 μm
An excitation light source for emitting excitation light band, quartz was added and the multiplexer to the pumping light multiplexer emitted signal light of 1.5μm band from the excitation light source, fluorine refractive index n _c of the (F) Glass (Si
O ₂ ) is provided with erbium (Er) having a high refractive index n ₀₁ (n ₀₁ > n _c ) having a diameter D at substantially the center of the clad having a circular cross section.
Aluminum (Al) and has a first core formed of germanium (Ge) codoped quartz glass (SiO _2), the outer circumference of the first core, the thickness S ₁ of the low refractive index n _m1
A first intermediate layer made of quartz glass (SiO ₂ ) to which phosphorus (P) of (n _m1 <n ₀₁ ) and fluorine (F) are added, and a thickness W on the outer periphery of the first intermediate layer; High refractive index n ₀₂ (n ₀₂
≧ n ₀₁ ) having a second core made of quartz glass (SiO ₂ ) co-doped with erbium (Er), phosphorus (P), and aluminum (Al), and having a thickness around the second core. S
And a rare-earth-doped optical fiber having a second intermediate layer made of the _second low refractive index _{n m2 (n m2 <n 02} ) of phosphorus (P) and fluorine (F) quartz glass doped with (SiO ₂₎ A wide band, wherein the multiplexed light from the multiplexer is propagated to the rare earth element-doped optical fiber, and the amplified signal light is extracted from an output end side of the rare earth element-doped optical fiber. Optical fiber amplifier. 11. The broadband optical fiber amplifier according to claim 6, wherein an optical isolator is inserted on the input side and the output side of the signal light. 12. The wide-band optical fiber amplifier according to claim 6, wherein said signal light is wavelength-multiplexed with at least eight waves having different wavelengths.