JPH085860A - Rare earth element doped optical fiber type optical amplifier - Google Patents

Abstract

PURPOSE:To provide a rare earth doped optical fiber type optical amplifier which is extremely less fluctuated in amplification characteristics and noise characteristics with an environmental temp. change and is extremely high in a stability of these performance characteristics at the time of using the amplifier as an optical communication system. CONSTITUTION:Heating and cooling means are joined to a supporting body 2 of the optical amplifier which amplifies signal light 20 with the induction released light obtd. by making the signal light 20 and exciting light 22 incident on an optical fiber 1 which is doped with a rare earth element and is wound around the supporting body 2. The material of the supporting body 2 is a thermal conductor consisting of metal. The heating and cooling means consist of a Peltier element 9, a temp. sensor 10, a comparator circuit 11 which compares the temp. measured by the temp. sensor 10 and a preset temp. and a working control circuit 12 which controls the operation of the Peltier element 9 by the result of comparison made by the comparator circuit 11. The height of winding of the optical fiber 1 wound on the supporting body 2 is above the winding width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth element-doped optical fiber type optical amplifier used in the field of optical communication.

[0002]

2. Description of the Related Art In an optical communication system, the amplification of an optical signal attenuated by long-distance transmission has conventionally been carried out by converting an optical signal into an electric signal, electrically amplifying it, and then converting it into an optical signal again. Has been done. However, such a method has a problem that the relay of large-capacity communication that requires high speed is limited and the system becomes complicated. Recently, an optical amplifier capable of directly amplifying an optical signal without converting the optical signal into an electric signal is being used. The optical amplifier is a device for directly amplifying the signal light passing through the optical fiber by the stimulated emission of the active element, which is excited by the excitation light incident on the optical fiber whose core portion is doped with a rare earth element such as erbium.

An optical amplifier using an optical fiber doped with erbium as an active element is suitable for optical amplification for 1.55 μm band optical communication and is already in practical use. Further, for optical amplification for 1.30 μm band optical communication, attention is paid to an optical fiber doped with neodymium or praseodymium.

The main components of the optical amplifier include, in addition to the rare earth element-doped optical fiber, a pumping light source for pumping the active element, a power supply circuit for driving the pumping light source, pumping light from the pumping light source and signal light. There is an optical multiplexer for making the incident light on the rare earth element-doped optical fiber, an optical isolator for removing the reflected light of the excitation light or the signal light, and the like.
The incident direction of the excitation light to the rare earth element-doped optical fiber is as follows: forward excitation of the signal light from the incident side to the rare earth element doped optical fiber, forward excitation of the signal light, backward excitation of the emission side, and excitation of the incident and emission sides. There is bidirectional pumping, which can be selectively used according to the intended use of the optical amplifier.

The rare-earth element-doped optical fiber used in the optical amplifier has a different length depending on the concentration of the active element in the core and the fiber structure, and various lengths from less than 10 m to more than 200 m are adopted. To make it compact, it is wrapped around a bobbin or reel with a diameter of several cm. Further, the main components of the optical amplifier are housed in one housing, and are electrically and optically connected to each other to function as an optical amplifier.

Optical amplifiers are required to have performance characteristics such as high amplification gain and low noise figure, and stability of those performance characteristics is also important when used as an optical communication system.
Especially, when an optical amplifier is installed outdoors, -20 to 20
It must operate stably even in an environment with a temperature change of about 50 ° C.

However, since the temperature of the conventional rare earth element-doped optical fiber type optical amplifier changes in accordance with the external environmental temperature, when it is exposed to an environment with a temperature change,
Especially, there is a problem that the amplification characteristic and the noise characteristic are deteriorated at a high temperature.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the variation of the amplification characteristic and the noise characteristic is extremely small with respect to the change of the environmental temperature, and therefore, when it is used as an optical communication system. It is an object of the present invention to provide a rare earth element-doped optical fiber type optical amplifier having high stability of their performance characteristics.

[0009]

A rare earth element-doped optical fiber type optical amplifier of the present invention made to achieve the above object is doped with a rare earth element and wound on a support 2 as shown in FIG. Signal light 20 and pump light 2 in the optical fiber 1
In the optical amplifier that amplifies the signal light 20 with the stimulated emission light obtained by making 2 incident, the heating / cooling means is joined to the support 2.

The material of the support 2 is a heat conductor made of metal, and the heating and cooling means is a Peltier element 9 (thermoelectric element).
And a temperature sensor 10 and a comparison circuit 11 for comparing the temperature measured by the temperature sensor 10 with a preset temperature.
And an operation control circuit 12 for controlling the operation of the Peltier element 9 according to the comparison result of the comparison circuit 11.

Further, in the optical fiber 1 wound around the support 2, it is preferable that the winding height is not less than the winding width.

[0012]

In the rare earth element-doped optical fiber type optical amplifier of the present invention, as shown in FIG. 1, the heating / cooling means is joined to the support body 2 around which the optical fiber 1 is wound.
Is maintained at a preset temperature. Moreover, since the material of the support 2 is a metal heat conductor and the winding height of the optical fiber 1 wound around the support 2 is sufficiently larger than the winding width,
The temperature control of the optical fiber 1 is efficiently performed.

[0013]

EXAMPLES Examples of the present invention will be described in detail below.

FIG. 1 is a block diagram of an embodiment of a rare earth element-doped optical fiber type optical amplifier to which the present invention is applied.

The rare earth element-doped optical fiber type optical amplifier of this embodiment is constructed as follows as an optical amplifier for 1.55 μm.

The 40 m long silica glass optical fiber 1 doped with erbium is made of aluminum and has an outer diameter of 60 m.
The reel 2 having a width of m and a width of 4 mm is wound about 200 times with almost no tension. A case 8 containing a Peltier element 9 and a temperature sensor 10 is attached to the side surface of the reel 2. The temperature sensor 10 and the operation control circuit 12 are connected to the comparison circuit 11, and the operation control circuit 12 is connected to the Peltier element 9 (see FIG. 2). One end of the optical fiber 1 is connected to the optical multiplexer 3, and the other end is connected to the optical isolator 4. An optical fiber 6 for communication and an optical fiber connected to the pumping light source 5 are connected to the input side of the optical multiplexer 3. A communication optical fiber 7 is connected to the output side of the optical isolator 4.

When the temperature of the reel 2 is set in advance in the comparison circuit 11, the temperature of the reel 2 measured by the temperature sensor 10 is compared with the set temperature by the comparison circuit 11, and if different, the operation control circuit. The Peltier element 9 is activated by 12 to heat or cool the reel 2 to the same temperature as the set temperature.

The entire optical amplifier of the embodiment shown in FIG. 1 is placed in a temperature variable thermostatic chamber, the entire reel 2 is kept at a temperature of 20 ° C. ± 2 ° C., and the communication light 20 having a wavelength of 1.55 μm is supplied to the communication optical fiber 6. Then, the excitation light 22 having a wavelength of 1.48 μm was incident from the excitation light source 5. At this time, a heat cycle test at −20 ° C. to 50 ° C. is performed, the intensity and noise of the outgoing communication light 21 are measured to obtain the amplification gain and the noise figure, and their variations, and the results are shown in FIG. Is indicated by a solid line. The fluctuation of the amplification gain was 0.1 dB or less, and the fluctuation of the noise figure was 0.2 dB or less, which were extremely small.

For comparison, the characteristics of the rare earth element-doped optical fiber type optical amplifier to which the present invention is not applied are evaluated using the following comparative examples.

An erbium-doped silica glass optical fiber 1 having a length of 40 m, which has the same characteristics as in the above embodiment, has an outer diameter of 6
A polypropylene reel having a width of 0 mm and a width of 20 mm was wound about 200 times with almost no tension, and the case 8 containing the Peltier element 9 and the temperature sensor 10 was not attached to the side surface of the reel. An optical amplifier of a comparative example is constructed in the same manner as.

Using the optical amplifier of this comparative example, a heat cycle test was conducted under the same conditions as those of the example, and the result is shown by a chain line in FIG. 3 as a comparative example. The fluctuation of the amplification gain is 1.
The fluctuation of the noise figure was 8 dB and the fluctuation of the noise figure was as large as 0.6 dB.

[0022]

As described above in detail, in the rare earth element-doped optical fiber type optical amplifier of the present invention, the variation of the amplification characteristic and the noise characteristic with respect to the change of the environmental temperature is extremely small,
When used as an optical communication system, their performance characteristics are highly stable.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a rare earth element-doped optical fiber type optical amplifier to which the present invention is applied.

FIG. 2 is a control block diagram of an embodiment of a rare earth element-doped optical fiber type optical amplifier to which the present invention is applied.

FIG. 3 is a diagram showing a relationship between heat cycle time, amplification gain fluctuation, and noise figure fluctuation.

[Explanation of symbols]

1 is an optical fiber, 2 is a reel, 3 is an optical multiplexer, 4 is an optical isolator, 5 is an excitation light source, 6 and 7 are communication optical fibers, 8 is a case, 9 is a Peltier element, 10 is a temperature sensor, 11 is A comparison circuit, 12 is an operation control circuit, 20 is communication light, 21 is outgoing communication light, and 22 is excitation light.

Claims (3)

[Claims] 1. An optical amplifier for amplifying signal light by stimulated emission light obtained by allowing signal light and excitation light to enter an optical fiber which is doped with a rare earth element and wound around a support, and heating and cooling the support. A rare earth element-doped optical fiber type optical amplifier characterized in that the means are joined. 2. The material of the support is a heat conductor made of metal, and the heating and cooling means includes a Peltier element, a temperature sensor, and a temperature measured by the temperature sensor and a preset temperature. 2. The rare earth element-doped optical fiber type optical amplifier according to claim 1, comprising a comparison circuit for comparison and an operation control circuit for controlling the operation of the Peltier device according to the comparison result of the comparison circuit. 3. The rare earth element-doped optical fiber type optical amplifier according to claim 1, wherein the height of the winding of the optical fiber wound around the support is not less than the winding width.