JPH0410586A - Optical fiber amplifier - Google Patents

Abstract

PURPOSE:To obtain an optical fiber amplifier which is high in gain and able to excite two or more light rays different in wavelength by a method wherein two or more excitation light rays to use are made to have wavelengths to which an amplification optical fiber has the same absorption coefficient. CONSTITUTION:Excitation wavelengths lambdap1 and lambdap2 of excitation light rays alphaand beta are 0.98mum and 0.65mum respectively, and an erbium doped quartz single mode optical fiber is used as an amplification optical fiber 1. The absorption coefficients of the amplification optical fiber 1 to light rays of 0.65mum and 0.98mum in wavelength are nearly equal to each other and larger than that to light ray of 1.48mum in wavelength. If the excitation light rays alpha and beta 0.65mum and 0.98mum in excitation wavelength equal to each other in absorption coefficient are used, the lengths of an optical fiber where light rays alpha and beta become maximum in gain are coincident with each other, so that light rays of single wavelength are improved in gain. In result, an optical fiber amplifier large in gain for light rays different in wavelength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical fiber amplifier for communication, particularly to a pumping wavelength.

(Prior Art) In recent years, research and development have been actively conducted on optical fiber amplifiers that introduce pumping light of an appropriate wavelength into an optical fiber doped with a rare earth element such as erbium.

Compared to laser amplifiers using semiconductor lasers, for example, this optical fiber amplifier has less polarization dependence, less coupling loss with the transmission optical fiber, excellent temperature characteristics, and a wider wavelength range for amplification. It has the following features and is considered to be extremely useful in the construction of future optical communication systems.

Currently, in order to actively apply these features to systems, improvements in various characteristics, including gain, are being considered. Optical fiber amplifiers configured to pump light of multiple wavelengths are also used.
Therefore, it has the advantage that the gain is larger than that of single wavelength pumping.

However, when pumping a conventional optical fiber amplifier using a plurality of wavelengths, there is a problem that the improvement in gain is not necessarily sufficient.

That is, FIG. 3 is a gain characteristic diagram with respect to the optical fiber length when pumping with a plurality of wavelengths in a conventional optical fiber amplifier, and the solid lines A and B are respectively when the wavelength λp of the pumping light is 0.
Showing the independent gain at 98 μm and 1,48 μm,
A broken line C shows the gain when both pump lights are used simultaneously. As is clear from Figure 3, when pumping with a single wavelength, a certain amount of gain is obtained, but when both are used at the same time, the optical fiber length at which the gain is maximum is different. The drawback was that the gain improvement was not necessarily large.

(Problems to be Solved by the Invention) As explained above, the conventional optical fiber amplifier has a problem in that the improvement in gain is small even when pumping multiple wavelengths.

The present invention was made to solve the above problems, and
[Structure of the Invention] (Means for Solving the Problems) The first invention aims to provide an optical fiber amplifier with multi-wavelength pumping that has improved gain or is larger than the conventional one. An optical fiber amplifier pumped by light is characterized in that the plurality of pump lights used are in a wavelength band in which the absorption coefficients of the amplification optical fibers are approximately the same.

A second invention is characterized in that in the first invention, the wavelengths of the plurality of excitation lights are approximately 0.65 μm and 0.98t1m, respectively.

(Function) Since the optical fiber amplifier according to the present invention selects and uses a plurality of pumping light wavelengths or the absorption coefficients of the amplifying optical fibers so that they are almost the same, each optical fiber amplifier has approximately the same optical fiber length region where the gain is large. A common and large gain improvement can be obtained.

(Example) Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 1 and 2 are drawings for explaining embodiments and examples of effects of the present invention.

In the embodiment shown in FIG. 1, the excitation wavelength λp of the excitation lights α and β is
1 and λp2 are 0.98 μm and 0.65 μm, respectively, and the amplification optical fiber 1 is an erbium-doped quartz single-mode optical fiber. In addition, 11 is the excitation wavelength λ
An optical filter 12 reflects the excitation light α of p1 and transmits the signal light λS, and 12 represents an optical filter that reflects the excitation light β of the excitation wavelength λp2 and transmits the signal light λS and the excitation light α.

In this invention, the main factor that determines the relationship between the gain and the optical fiber length is the amplifier optical fiber 1 at the pump wavelength λp.
This study focuses on the fact that when pumping at a wavelength with a small absorption coefficient, the optical fiber length at which the gain is maximum becomes long, and conversely, when pumping at a wavelength with a large absorption coefficient, it becomes short.

In other words, the absorption coefficient of the amplification optical fiber, which is an erbium-doped silica single-mode optical fiber, is at a wavelength of 0.65μ.
It is almost the same as m and 0.98 μm, and the wavelength is 1.48 μm.
larger than For example, the erbium concentration is 100 ppI1
1, each wavelength is 0.65μrn, 0.98μrn,
The absorption coefficient at 1.48 μm is 3.9 dB/a, respectively.
+, 3.7dB/m, 1. l1ldB/m. In this way, excitation light α with two wavelengths of 065 μm and 0.98 μm, which have almost the same absorption coefficient, is used.
If β is used, the length of the optical fiber at which the maximum gain can be obtained is almost the same as shown in Fig. 2, as shown by A, and the gain improvement at a single wavelength is the same as that of conventional amplification, as shown by code C. The size of the optical fiber is larger than that of optical fiber.

Although FIG. 1 describes the configuration in which a plurality of pumping lights (α, β) enter the amplifying optical fiber 1 from the same direction, the same effect can be obtained in a configuration in which the pumping lights enter from both directions.

[Effects of the Invention] As described above, the optical fiber amplifier according to the present invention can obtain a larger gain in multi-wave pumping than the conventional optical fiber amplifier, and has a great practical effect.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the optical fiber amplifier according to the present invention, Fig. 2 is an amplification characteristic diagram of the optical fiber amplifier shown in Fig. 1, and Fig. 3 is an amplification characteristic diagram of a conventional optical fiber amplifier. It is. 1... Optical fiber for amplification, 11.12... Optical filter, α, β... Pumping light, λS... Signal light. Agent Patent Attorney Norihiro Ogo 1: 1 Suga 11 round fufu 8゛11.12: Optical F 11 ref d, ρ: Moon power, Noyu-kiri Z Fig. ■

Claims (2)

[Claims] (1) An optical fiber amplifier that pumps with light of a plurality of wavelengths, wherein the plurality of pumping lights used are in a wavelength band in which the absorption coefficients of the amplification optical fibers are approximately the same. (2) The wavelength of each of the plurality of excitation lights is approximately 0.65μ
Claim (1) characterized in that m and 0.98 μm.
Optical fiber amplifier as described.