JPH04273220A - Optical fiber amplifier - Google Patents

Abstract

PURPOSE:To miniaturize the optical fiber amplifier and to reduce its power consumption. CONSTITUTION:An optical demultiplexer 15 which separates light from a light source 11 for excitation and signal light 12 is connected between an optical fiber 10 wherein a rare earth element is added and an optical isolator 14 and a total reflecting mirror 17 is arranged on the demultiplexing-side projection terminal 16 of the optical demultiplexer 15. The exciting light from the light source 11 for excitation and the signal light are guided by the optical demultiplexer 13 to the optical fiber 10 and the signal light 12 is amplified. The amplified signal light 12 and the exciting light which does not contribute to the excitation are multiplexed by the optical demultiplexer 15. The signal light is guided to a transmission line and the exciting light is reflected by the total reflecting mirror 17 provided at the demultiplexing-side projection terminal 16 and guided to the optical fiber 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier used in optical communications using an optical fiber as an amplification medium.

0002

2. Description of the Related Art Generally, as an optical fiber amplifier, one using an optical fiber doped with a rare earth element as an amplification medium is mainly used. Conventionally, as shown in FIG. 4, this type of optical fiber amplifier includes an optical fiber 1 doped with a rare earth element and an excitation amplifier for exciting the rare earth ions inside the optical fiber 1 to perform optical amplification. A light source 2, and the excitation light and signal light from this excitation light source 2 are connected to an optical fiber 1.
The configuration includes an optical multiplexer 3 that guides the optical fibers.

Currently, when amplifying signal light having a wavelength of 1.55 μm, erbium (Er3+) is used as the rare earth element doped into the optical fiber 1.
The core portion is doped with several tens to several thousand ppm and becomes an ionic state. The excitation light source 2 for exciting the erbium ions to cause the optical fiber 1 to have an amplification effect has an oscillation wavelength of 1.
．． A 48 μm or 0.98 μm semiconductor laser is used. This excitation light is multiplexed with signal light 4 by optical multiplexer 3 and guided to optical fiber 1 .

[0004] The erbium ions of this optical fiber 1 are
It has a high absorption spectrum in the 1.48 μm band and 0.98 μm band, absorbs light energy, and excites it to a higher level. Then, due to the stimulated emission phenomenon in the 1.55 μm band when this excited ion returns to the ground level,
．． The 55 μm signal light is amplified. Further, an optical isolator 5 may be connected to the exit side of the optical fiber 1 doped with rare earth elements in order to prevent the amplifier itself from oscillating due to reflected return light.

On the other hand, when an optical fiber amplifier is used in a practical line, it may be necessary to monitor the output signal light as a means of keeping the output power constant. In this case, usually Figure 5
As shown in the figure, the branch ratio is 10:1 to 10 on the output side of the amplifier.
An optical coupler 6 of about 0:1 is connected, and the output light is monitored. Note that in FIG. 5, the configurations of the optical fiber 1, excitation light source 2, optical multiplexer 3, and optical isolator 5 are the same as those in FIG. 4.

[0006]

[Problems to be Solved by the Invention] However, the gain of an optical fiber amplifier (amplitude ratio of an output signal to a sine wave input signal of constant amplitude) is approximately proportional to the concentration of mainly erbium ions in the optical fiber 1 and the fiber length. , is the difference between the amplified signal light and the loss due to absorption in the optical fiber 1. Normally, in order to obtain maximum gain, the fiber length must be several tens to hundreds of meters.
is necessary, and the output of the excitation light source 2 is also several tens to hundreds of meters.
W is required.

[0007] Therefore, conventional optical fiber amplifiers have had the problem that the optical fiber 1 is long and the mounting size becomes large. Further, the excitation light source 2 requires a large output, and one or more excitation lasers may be required. Furthermore, when such a high-output excitation light source 2 is used, the power consumption becomes large and the excitation light source 2 itself generates a large amount of heat.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical fiber amplifier that is compact and consumes less power.

[0009]

[Means for solving the problem] The invention according to claim 1 includes:
Optical fiber amplifiers are equipped with an optical fiber that acts as an amplification medium, a pumping light source that amplifies the optical fiber, and an optical coupler that introduces the output light of the pumping light source into the optical fiber. An optical demultiplexer for separating the amplified light and the output light of the excitation light source is connected to at least one point in the path, and a total reflection mirror is arranged at the output end of this optical demultiplexer. be.

According to a second aspect of the invention, a fiber fusion type optical coupler is connected to an optical demultiplexer as a means for monitoring the output light of the excitation light source.

The invention as set forth in claim 3 provides an optical fiber that acts as an amplification medium, a pumping light source that causes the optical fiber to perform an amplifying action, and an optical coupler that introduces the output light of the pumping light source into the optical fiber. In an optical fiber amplifier equipped with a This configuration includes a filter that reflects only the wavelength of the excitation light source.

0012

[Operation] According to the present invention, the pumping light emitted from the optical fiber, which is the amplification medium, is reintroduced into the optical fiber, which is the amplification medium, so it is possible to utilize the pumping light power without wasting it. It is. Therefore, there is no need to use a high-output light source, and the length of the optical fiber serving as the amplification medium can be shortened. Therefore, it is possible to reduce the size of the optical fiber amplifier and also to reduce power consumption.

[0013]

EXAMPLES The present invention will be explained in detail with reference to Examples below.

FIG. 1 is a schematic diagram showing an embodiment of an optical fiber amplifier according to the present invention. This optical fiber amplifier includes an optical fiber 10 doped with a rare earth element such as erbium and acting as an amplification medium;
It includes a pumping light source 11 that excites internal rare earth ions to perform optical amplification, and an optical multiplexer 13 that guides the pumping light from the pumping light source 11 and signal light 12 to an optical fiber 10. In addition, the optical fiber 10 and the optical isolator 14
Pumping light from a pumping light source 11 and signal light 12 are provided between
An optical demultiplexer 15 is connected to the optical demultiplexer 15 to separate the
is located.

In the optical fiber amplifier configured as described above, the pumping light from the pumping light source 11 and the signal light 12 are guided to the optical fiber 10 by the optical multiplexer 13, and the signal light is 12 is amplified. and,
The amplified signal light 12 and the pumping light that does not contribute to pumping are separated by an optical demultiplexer 15. Here, the signal light 12 is guided to the transmission path, and the excitation light is reflected by the total reflection mirror 17 provided at the output end 16 on the demultiplexing side, and is then redirected to the optical fiber 1.
It leads to 0.

In this way, in this optical fiber amplifier, the pumping light emitted from the optical fiber 10 which is an amplification medium without contributing to optical amplification is reintroduced into the optical fiber 10 which is an amplification medium. It becomes possible to utilize the excitation light power without wasting it. As a result, there is an advantage that there is no need to use a high-power pumping light source 11, and the length of the optical fiber 10, which is an amplification medium, can be shortened.

Furthermore, when an optical fiber amplifier is used in a practical line, it may be necessary to monitor the output signal light in order to keep the output power constant. In this embodiment, when an optical demultiplexer 15 with an isolation of about 20 dB is used, a signal light corresponding to 1/100 of the pump light is branched.

Now, as shown in FIG. 2, it is also possible to connect a fiber fusion type optical coupler 18 to the optical demultiplexer 15 to monitor the pumping light, that is, the output light. In this case, there is no need for a new optical coupler for monitoring, and the same effect can be obtained with a much simpler configuration than before. In addition, a total reflection mirror 17 is disposed at the output end 16 on the demultiplexing side of the optical demultiplexer 15, and the excitation light and signal light 12 from the excitation light source 11 are guided to the optical fiber 10. fiber 10
the point where the signal light 12 is amplified, and the optical multiplexer 13,
The configuration of the optical isolator 14 is the same as that in FIG.

FIG. 3 shows another embodiment of the optical fiber amplifier according to the present invention. A filter 19 that transmits the signal light 12 and reflects the wavelength of the excitation light source 11, and a filter-fused optical coupler 20 that monitors the output light are connected to the demultiplexing side output end 16 of the optical demultiplexer 15. It is located. Note that the optical fiber 10, the excitation light source 11, and the optical multiplexer 13
The configuration of the optical isolator 14 is the same as that in FIG.

[0020]

As explained above, according to the optical fiber amplifier according to the present invention, a total reflection mirror or a filter that reflects only the wavelength of the excitation light source is arranged at the output end of the optical demultiplexer, and the amplification medium Since the pumping light emitted from the optical fiber is reintroduced into the optical fiber, which is the amplification medium, it has become possible to use the pumping light power without wasting it. Therefore, there is no need to use a high-output light source as in the past, and the length of the optical fiber that is the amplification medium can be shortened, making it possible to downsize the optical fiber amplifier and reduce power consumption. It has the excellent effect of being able to

[Detailed explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical fiber amplifier according to the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the optical fiber amplifier according to the present invention.

FIG. 3 is a schematic configuration diagram showing still another embodiment of the optical fiber amplifier according to the present invention.

FIG. 4 is a schematic configuration diagram showing an example of a conventional optical fiber amplifier.

FIG. 5 is a schematic configuration diagram showing another example of a conventional optical fiber amplifier.

[Explanation of symbols]

10 Optical fiber 11 Excitation light source 12 Signal light 13 Optical multiplexer 15 Optical demultiplexer 16 Demultiplexing side output end 17 Total reflection mirror 18 Optical coupler 19 Filter 20 Optical coupler

Claims (3)

[Claims] Claim 1: an optical fiber that acts as an amplification medium; a pumping light source that causes the optical fiber to perform an amplification action;
In an optical fiber amplifier including an optical coupler that introduces the output light of the pumping light source into the optical fiber, the amplified light and the output light of the pumping light source are separated at at least one location in the optical transmission line. An optical fiber amplifier characterized by connecting an optical demultiplexer and arranging a total reflection mirror at the output end of the optical demultiplexer. 2. The optical fiber amplifier according to claim 1, further comprising a fiber fusion type optical coupler connected to the optical demultiplexer as means for monitoring the output light of the excitation light source. 3. An optical fiber that acts as an amplification medium, and a pumping light source that causes the optical fiber to perform an amplification action.
In an optical fiber amplifier including an optical coupler that introduces the output light of the pumping light source into the optical fiber, the amplified light and the output light of the pumping light source are separated at at least one location in the optical transmission line. What is claimed is: 1. An optical fiber amplifier connected to an optical demultiplexer, and having a filter arranged at the output end of the optical demultiplexer to reflect only the wavelength of a pumping light source.