JP2776322B2 - Optical amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an erbium (E)
The present invention relates to an optical amplifier using an optical fiber doped with a rare earth such as r) or neodymium (Nd).

[0002]

2. Description of the Related Art FIG. 3 shows an embodiment of a conventional optical amplifier.
In the figure, an optical amplifier comprises a rare earth doped fiber (hereinafter referred to as a REED fiber) 5 as an amplification medium and a pumping light source 4.
And a WDM coupler 2 for injecting the excitation light source into the amplification medium. The power of the pumping light output from the pumping light source 4 is injected into the REED fiber 5 by the WDM coupler 2, whereby the REED fiber 5 is put into an excited state. When an optical signal is input from the input terminal 1, the optical signal is amplified. And output from the output terminal 3. An example of such an optical amplifier is disclosed in Japanese Patent Publication No. 6-24273.

[0003]

The REED fiber has a characteristic of amplifying light in a specific wavelength band by injecting pump light of a certain wavelength.

An example of a REED fiber is an erbium-doped fiber (EDF). When this fiber is used, an optical amplifier for a 1560 nm band having a 3 dB gain bandwidth of about 20 nm can be realized. The amplification bandwidth is sufficient as a repeater when used alone, but when used in a multi-relay system such as a submarine repeater system, the bandwidth of the system is extremely low due to the effect called auto-filtering. It becomes narrow. In order to prevent this, strict accuracy is required for the transmission side optical wavelength, and wavelength multiplex transmission, which is an effective means for expanding the transmission capacity, is very difficult.

An object of the present invention is to eliminate the above-mentioned disadvantages,
An object of the present invention is to provide an optical amplifier capable of expanding a transmission band.

[0006]

The optical amplifier according to the present invention comprises:
In order to solve the above-described problems, an amplification medium configured by directly cascading a plurality of rare-earth doped fibers each having a different wavelength at which the gain of the fiber is maximized, and a single pump for pumping the plurality of fibers. A light source.

[0007] The gain characteristics of an optical amplifier using a REED fiber are wavelength-dependent, and the wavelength λp at which the gain is maximized.
Varies depending on the types of rare earth elements and other elements to be doped and their amounts.

Therefore, REED fibers with different λp can be realized by changing the kind or amount of the dopant. By cascading several types of REED fibers having different λp and using them in an optical amplifier, an optical amplifier repeater having a wider band can be realized.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In FIG.
Conventionally, one kind and one REED fiber is used as an amplification medium, whereas in this embodiment, n kinds and n pieces of REED fibers are used.
The ED fibers FA1 to FAn are cascaded and used as an amplification medium.

Each REED fiber FAi has a gain wavelength characteristic Gci at which the gain becomes maximum at the wavelength λpi (i represents the ith fiber of the n fibers). Specifically, λpi and Gci are determined by appropriately selecting the amount of doping or the type of rare earth to be doped and both. By cascading a plurality of these REED fibers having different gain peak wavelength characteristics and using them as an amplification medium, an optical amplifier having a very wide gain wavelength characteristic GcT as shown in FIG. 2 can be obtained. Note that the excitation light source 6 generates excitation light corresponding to each of these n fibers.

[0012]

As described above, the kind or amount of the dopant is different, and thus several kinds of REED fibers having different λp are cascaded and used for the optical amplifier, so that a wider band optical amplifier suitable for wavelength multiplexing transmission or the like can be obtained. A repeater can be realized.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing gain characteristics of the optical amplifier of the present invention.

FIG. 3 is a configuration diagram showing an example of a conventional optical amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal input port 2 WDM coupler 3 Signal output port 4 Light source for excitation FA Rare earth doped fiber Gc Gain wavelength characteristic λp Maximum gain wavelength

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/07 G02F 1/35 501 H01S 3/10 H01S 3/17

Claims (3)

(57) [Claims] The wavelengths at which the gain of the fiber is maximum are different from each other.
Cascade multiple rare earth doped fibers
Amplifying medium connected and configured and these multiple fibers
An optical amplifier, comprising: a single pumping light source for pumping . 2. The wavelength at which the gain of the fiber is maximum,
Different elements such as rare earth doped in the fiber
The optical amplifier according to claim 1, wherein the optical amplifier is set by performing the setting. 3. The wavelength at which the gain of the fiber is maximum,
Doping of the fiber with an element such as a rare earth
2. The photomultiplier according to claim 1, wherein the light intensity is set by varying the amount.
Breadboard.