JPH0563284A - Optical amplifier - Google Patents

Abstract

PURPOSE:To provide an optical amplifier using a practical Pr3+-doped fiber by moving an exciting wavelength of the amplifier using the Pr<3+>-doped fiber to a wavelength band capable of being excited by a semiconductor laser. CONSTITUTION:An optical amplifier has an exciting light source 1, an optical coupler 3 for coupling an exciting light with a signal light, and an optical fiber 4 containing a rare earth element ions in a core, and comprises an infrared optical fiber doped with Pr<3+> ions and Nd<3+> ions as rare earth element ions in a core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier for optical communication operating in the 1.3 μm band.

[0002]

2. Description of the Related Art Recently, an optical fiber amplifier using a stimulated emission of a transition in a 4f shell by doping a core of an optical fiber with a rare earth ion, particularly an _Er ³⁺ ion, has been vigorously studied, and a 1.5 μm band Is being applied to optical communication systems. The rare-earth-doped optical fiber amplifier has high gain and polarization-independent gain characteristics, and also has low noise figure and wide-band wavelength characteristics, which makes its application in optical communication systems extremely attractive. .

On the other hand, the 1.3 μm band where the chromatic dispersion of a silica-based optical fiber is zero is an important wavelength band in optical communication along with the 1.5 μm band, and research on optical fiber amplifiers operating in this 1.3 μm band has been conducted. , Nd ³⁺ ion-doped silica and fluoride optical fibers have been used. However, both of the fibers used in optical communication 1.31
At μm, the excited state absorption of Nd ³⁺ ion (Excited State A
Since the absorption is large, for example WJ miniscalco, L.
J. Andrews, BAThompson, RS Qninby, LJB Vach
a and MG Drexhage, “Electron. Lett.” (vol.24, 1
988, P.28) or Y. Miyajima, T. Komukai, Y. Sugawa a
nd Y. Katsuyama, “Technical Digestof Optical Feber
Communication Conference '90 San Francisco ”(199
0, PD16), etc., no amplification has been confirmed.

Under such circumstances, it is strongly desired to realize an optical fiber amplifier having an amplifying function at 1.31 μm, and one of the candidates is Y. Ohishi, T. Kanamori, T. Kitagaw.
a, S.Takahashi, E.Snitzer and GHSigel “Technical
Digest of Optical Fider Communication Conference '91
In San Diego "(1991, PD2) , the fluoride glass of ZrF ₄ system as a host material, has been proposed an optical fiber amplifier using an optical fiber doped with P _r ^3+. The optical fiber amplifier 2 as can be seen from the energy diagram of P _r ³⁺ ions shown in, P _r ^{3+ 1} G ₄ ions
→ It uses stimulated emission of ³ H ₅ transition.

However, since it is difficult to obtain a high-power semiconductor laser operating in the same wavelength band using 1.017 μm as a pumping wavelength, it is necessary to use a semiconductor laser pumping light which is necessary for application in an actual optical communication system. The fiber amplifier has a drawback that it is difficult to construct and thus lacks practicality.

[0006]

[SUMMARY OF THE INVENTION The present invention, the excitation wavelength of the amplifier using a P _r ³⁺ doped fiber is moved to the semiconductor laser excitable wavelength band, the P _r ³⁺ doped fiber of utility It is to provide the used optical amplifier.

[0007]

The optical amplifier of the present invention co-dopes Nd ³⁺ ions with P _r ³⁺ ions in the core. Figure 3 shows the energy diagram of P _r ³⁺ and Nd ³⁺ . The ⁴ F _3/2 level of Nd ³⁺ can be excited by light in the 0.8 μm band, and when this ⁴ F _3/2 level is excited,
Nd ³⁺ causes a strong emission of 1.06 μm due to the ⁴ F _3/2 → ⁴ I _11/2 transition. At this time, when P _r ³⁺ ions coexist with Nd ^{3+ _{ions, Nd 3+ (4 F 3/2 →}} 4 I 11/2) → P r 3+ (3 H 4 → 1 G 4) energy process ¹ G ₄ level P _r ³⁺ is excited by the movement, ¹ G ₄ → ³ H ₅ transition P _r ³⁺ ions is induced.

Conventionally, P_r ³⁺of¹G_FourExcite levels directly
Required excitation light in the 1.017 μm band.
There is no high-power semiconductor laser that operates in the band_r ³⁺of¹G_Four
It was difficult to pump with a level semiconductor laser. Only
Then P_r ³⁺With Nd³⁺Nd by co-doping
³⁺To P_r ³⁺Energy transfer to P_r ³⁺of ¹G
_FourThe level of 0.8 μm band available to excite levels
The point made possible by using an output semiconductor laser is
_r ³⁺It is different from a doped optical amplifier.

[0009]

1 is a block diagram of an embodiment of an optical amplifier of the present invention, in which 1 is a pumping light source, 2 is a signal source, 3 is an optical coupler,
Reference numeral 4 is an amplification fiber, 5 is an optical isolator, and 6 is an optical spectrum analyzer. Oscillation wavelength as excitation light source 1
GaAlAs semiconductor laser of 0.82 μm, DFB laser of oscillation wavelength 1.31 μm as signal source 2, and amplification fiber 4 of 10
m core diameter 2 μm, relative refractive index difference between core and clad 1.8
%, P _r ³⁺ concentration 500 ppm, Nd ³⁺ concentration fluoride fiber was used. The glass composition is core glass: ZrF ₄ (49) −BaF ₂
(22) −PbF ₂ (3) −LaF ₃ (3.5) −YF ₃ (2) −AlF ₃ (2.5) −Li
F (18 mol%), clad glass: ZrF ₄ (23.7) − H
_f F ₄ (23.8) −BaF ₂ (23.5) −LaF ₃ (2.5) −YF ₃ (2) −AlF ₃ (4.
5) -NaF (20 mol%). A gain of 13 dB was confirmed when the pump power was 100 mW. The gain was obtained by monitoring the signal intensity when the pumping power was turned on and off with the optical spectrum analyzer 6 and the intensity ratio thereof.

Here, a so-called ZrF ₄ containing ZrF ₄ as a main component is used.
Was used system glass as fiber glass, other fluoride glass, for example, InF ₃ system, ZnF ₂ system, AlF ₃ based glass (Tetsuro Izumiya supervision, "New glass and Properties" Chapter 16 Management System Laboratory issuance , 1984, or Tomozawa and Dor
emus bias Treatise on materials science and technolog
y volume 26, Chapter 4, Academic Press, Inc. 1985, etc.) Infrared glass may be used. In addition to fluoride glass, ThCl ₄ —PbCl ₂ —NaCl-based chloride glass,
AgBr-PbBr ₂ -CsBr-CdBr ₂ system of bromide glass, CdF ₂ -
BaCl ₂ -NaCl system fluoride - chloride glass, ZnBr ₂ -TlBr
-TlI-based bromide-iodide glass ("New Glass Handbook", New Glass Handbook Editorial Committee,
Maruzen Co., Ltd., 1991) or Ge-S series, As-S
System, Ge-P-S-based, may be used an infrared glass such as As-Ge-S chalcogenide glass, but is not limited to ZrF ₄ glass. The condition required for the fiber material is that the phonon energy of the fiber material is preferably 500 cm ^-1 or less so that the ¹ G ₄ level of P _r ³⁺ is not quenched by the phonon relaxation. The above glasses all satisfy this condition.

[0011]

As described above, the optical amplifier according to the present invention has a wavelength of P _r ³⁺ of 0.8 at which the semiconductor laser can be excited.
Since it can be moved to the μm band, it is possible to construct an amplifier using a semiconductor laser-pumped P _r ^{3 +} -doped fiber, which was difficult in the past, and to apply the amplifier using a P _r ^{3 +} -doped fiber to an optical communication system. There is an advantage that can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an optical amplifier of the present invention.

FIG. 2 is an energy level diagram of P _r ³⁺ .

FIG. 3 is a diagram showing energy transfer between P _r ³⁺ and Nd ³⁺ .

[Explanation of symbols]

 1 pumping light source 2 signal source 3 optical coupler 4 amplification fiber 5 optical isolator 6 optical spectrum analyzer

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01S 3/07 8934-4M

Claims (2)

[Claims] 1. An optical amplifier comprising an excitation light source, an optical coupler for coupling the excitation light and the signal light, and an optical fiber containing rare earth ions in the core, wherein P _r ³⁺ and Nd ³⁺ ions are used as rare earth ions. An optical amplifier characterized by using an infrared optical fiber having a core doped therein. 2. The optical amplifier according to claim 1, wherein an infrared optical fiber made of fluoride, chloride, bromide or iodide or an infrared optical fiber made of chalcogenide is used as the infrared optical fiber. Characteristic optical amplifier.