JP5298973B2 - Optical amplifier, optical amplifier control method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical amplifier that can be compensated for gain tilt that depends on temperature without an increase in power consumption and equipment size and with no reduction in band and no deterioration of signals. <P>SOLUTION: An EDF 3 is divided into n portions, and optical tunable filters 4-1 to 4-(n-1) are inserted between the divided EDF portions 3-1 to 3-(n). The temperature of the EDF 3 is detected by a thermistor 11. On the basis of the detected temperature of the EDF 3, the characteristics of the optical tunable filters 4-1 to 4-(n) is controlled by lengthening the effective length relating to amplification of the EDF 3 when the temperature is high and by shortening the effective length relating to amplification of the EDF 3 when the temperature is low, to compensate for a gain/wavelength tilt due to dependency on temperature. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to an optical amplifier that performs optical amplification by supplying pumping light to an optical amplification medium, an optical amplifier control method, and a program, and more particularly, to compensation for a temperature-dependent gain tilt.

  An optical amplifier is an amplifier that does not convert an optical signal into an electrical signal but amplifies it in the state of direct light. As such an optical amplifier, an EDF (Erbium-doped fiber amplifier) optical amplifier is known. When an EDF optical amplifier injects excitation light for amplification into the EDF, erbium ions absorb the energy of the laser light and are once excited into a high energy state and return from the excited state to the original low energy state. In addition, light by stimulated emission is emitted and signal light is amplified by the energy of this light.

  In an EDF optical amplifier, a gain wavelength tilt due to temperature dependency occurs. Therefore, as shown in FIG. 4, an EDF 203 is put in a heat insulating case 214 to keep the temperature in the heat insulating case 214 constant and prevent occurrence of gain wavelength inclination due to temperature dependence.

In FIG. 4, an erbium-doped optical fiber (hereinafter abbreviated as EDF) 203 is arranged in a heat insulating case 214. An excitation light multiplexing coupler 201 is disposed in front of the EDF 203. Excitation light is supplied from the excitation light source 202 to the excitation light multiplexing coupler 201.

  Further, a heater 213 and a thermistor 211 are disposed in the heat insulating case 214. The thermistor 211 detects the temperature in the heat insulating case 214. The temperature detection output of the thermistor 211 is sent to the temperature control circuit 212. The temperature control circuit 212 controls the heater 213 based on the temperature data in the heat insulation case 214 sent from the thermistor 211 to keep the temperature in the heat insulation case 214 constant. As a result, the occurrence of gain wavelength tilt due to temperature dependence of the EDF 203 is prevented.

  Further, Patent Document 1 (Japanese Patent Laid-Open No. 2001-185788) discloses that an inter-wavelength gain deviation is generated by the net gain of a rare earth fiber, and cancels out the gain deviation due to temperature, thereby inter-wavelength gain. It describes what eliminates the deviation.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2003-332660), the upper limit of the amplification band of TDF doped with rare earth thulium generally used in S-band (1460-1530 nm) amplifiers extends only to about 1510 nm. Therefore, a hybrid amplifier of EDF and TDF is described as an optical amplifier capable of obtaining a gain even on the long wavelength side of the S-band. Among them, the EDF type amplifier side describes that a region on the longer wave side than 1530 nm, which is the main region of the EDF amplification band, is cut between a plurality of EDFs with an optical filter.

JP 2001-185788 A JP 2003-332660 A

  WDM (Wavelength Division Multiplexing) is a technique for increasing transmission capacity by multiplexing a plurality of optical signals having different wavelengths. In recent years, there has been an increasing demand for an increase in the number of wavelength division multiplexing for increasing the transmission capacity, but in order to widen the wavelength band, it is necessary to increase the bandwidth of the optical amplifier by EDF. In an optical amplifier for WDM communication, an EDF having an amplification band in the lowest loss wavelength 1.55um band of a Si optical fiber is generally used as an amplification medium. Recently, a WDM wavelength multiplexing number of 80 waves has appeared, and EDF optical amplifiers are also required to have a bandwidth exceeding 30 nm.

  As the wavelength band expands, the temperature dependent gain wavelength slope of the EDF cannot be ignored. That is, the wavelength dependence of the gain of the EDF is roughly divided into gain flatness and gain inclination. The former does not depend much on temperature or the like, and is compensated by a fixed filter, but the latter changes depending on the temperature and the gain of the EDF and needs to be compensated dynamically.

  The first workaround for this problem is to cope with the increase in the number of wavelengths by increasing the density and not to expand the wavelength band to be used. In this method, since the crosstalk increases due to narrowing of the wavelength interval, it is necessary to perform wavelength multiplexing / demultiplexing of WDM communication more precisely, which causes an increase in cost. Further, since the risk of signal degradation due to nonlinear phenomena such as four-wave mixing and cross-phase modulation increases, it is necessary to reduce the signal power in order to suppress the nonlinear effect, resulting in a factor of shortening the transmission distance.

A second workaround for this problem is to keep the EDF at a constant temperature, as shown in FIG. However, in general, in the case of an optical amplifier for WDM communication, the length of the EDF is several tens of meters and the winding radius is also required to be at least 3 cm. It is a factor that hinders. In addition, in order to heat this space or to cool it as necessary, an enormous amount of power consumption equivalent to the power consumption used by the optical amplifier for signal amplification is required.

  Moreover, in what is shown in Patent Document 1, an optical variable attenuator is used in order to cancel out the gain deviation due to temperature by utilizing the fact that the gain deviation between wavelengths is generated by the net gain of the rare earth fiber. For this reason, signal loss due to the optical variable attenuator occurs.

  In addition, what is disclosed in Patent Document 2 is a TDF / EDF hybrid amplifier that can obtain a gain even on the long wave side of the S-band, and the filter disposed therein is a fixed filter. Yes, it does not control according to disturbances such as temperature.

  In view of the above-described problems, the present invention can compensate for a temperature-dependent gain tilt without increasing power consumption, increasing the size of the apparatus, and without reducing the bandwidth or causing signal degradation. It is an object of the present invention to provide an optical amplifier, an optical amplifier control method, and a program.

In order to solve the above problems, the present invention includes an optical amplifying medium is divided into a plurality of excitation light generating means for supplying pumping light to the optical amplifying medium, a temperature detecting means for detecting the temperature of the optical amplification medium And a control means for varying the effective length related to amplification of the optical amplification medium according to the temperature of the optical amplification medium.

Further, in an optical amplifier control method for performing optical amplification by supplying pumping light to an optical amplification medium, the optical amplification medium is divided into a plurality of parts, and an effective length related to amplification of the optical amplification medium according to the temperature of the optical amplification medium. Is variable.

  According to the present invention, the temperature-dependent gain tilt can be compensated without adjusting the temperature of the EDF by the heater or compensating the gain tilt by an optical device such as an optical attenuator. For this reason, there is no increase in equipment size or power consumption, and no optical power loss occurs. Further, since it is not necessary to store the EDF in a heat insulating case or the like, the degree of freedom for mounting the EDF is increased, and efficient arrangement is possible.

It is a block diagram of a 1st embodiment of the present invention. It is a graph used for description of a temperature dependent gain wavelength inclination. It is a block diagram of the 2nd Embodiment of this invention. It is a block diagram used for description of the conventional optical amplifier.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
As shown in FIG. 1, in the optical amplifier according to the first embodiment of the present invention, an erbium-doped optical fiber (hereinafter abbreviated as EDF) 3 as an optical amplification medium is divided into n pieces. Variable optical filters 4-1 to 4- (n-1) are inserted between the divided EDFs 3-1 to 3- (n). The variable optical filters 4-1 to 4- (n-1) can be changed to a characteristic that allows the excitation light to pass therethrough and a characteristic that blocks the excitation light. The excitation light multiplexing coupler 1 is disposed in front of the EDF 3. Excitation light is supplied from the excitation light source 2 to the excitation light multiplexing coupler 1.

  Further, the temperature of the EDF 3 is detected by the thermistor 11 as temperature detecting means. The temperature detection output of the thermistor 11 is sent to the optical filter wavelength control circuit 15. The optical filter wavelength control circuit 15 controls the variable optical filters 4-1 to 4 (n) based on the temperature data of the EDF 3 sent from the thermistor 11, and changes the effective length related to the amplification of the EDF 3 according to the temperature. Let Thereby, the gain wavelength inclination due to temperature dependence of the EDF 3 can be compensated.

  That is, FIG. 2 shows the gain wavelength tilt due to temperature dependence of the optical amplifier by EDF. In FIG. 2, the horizontal axis indicates the wavelength, and the vertical axis indicates the gain. Here, the gain wavelength inclination at each temperature of 0 degree, 25 degrees, and 50 degrees is shown.

  As is apparent from FIG. 2, the EDF has a gain slope that increases the gain on the short wave side when the temperature rises, and a gain slope that increases the gain on the long wave side when the temperature of the EDF decreases. On the other hand, with respect to the relationship between the length of the EDF and the gain, a gain slope is generated such that the longer the EDF length, the higher the gain on the long wave side. Therefore, when the temperature of the EDF rises, temperature-dependent gain wavelength tilt can be compensated by controlling the length of the EDF to be long.

  Therefore, in the first embodiment of the present invention, the temperature of the EDF 3 is detected by the thermistor 11, and the characteristics of the variable optical filters 4-1 to 4- (n) are controlled based on the temperature of the EDF 3, so that the temperature is high. The effective length related to the amplification of the EDF 3 is lengthened, and the effective length related to the amplification of the EDF 3 is shortened at a low temperature so that the gain wavelength inclination due to temperature dependence is compensated.

That is, when the temperature of the EDF 3 is the highest, the characteristics of all the variable optical filters 4-1 to 4- (n) are controlled so that the excitation light from the excitation light source 2 passes. In this case, the effective length related to the amplification of the EDF 3 is the total length of all the EDFs 3-1 to 3- (n). As described above, since the effective length related to the amplification of the EDF 3 becomes long at high temperatures, the gain on the long wave side is increased and the increase in the gain on the short wave side due to temperature dependence can be compensated.

When the temperature of the EDF 3 is slightly lowered, the characteristics of the variable optical filter 4- (n-1) are controlled so as to block the excitation light from the excitation light source 2. In this case, the effective length related to the amplification of the EDF 3 is the total length of the EDFs 3-1 to 3- (n-1), and the effective length related to the amplification of the EDF 3 is slightly shortened.

Hereinafter, as the temperature of the EDF 3 decreases from a high temperature to a low temperature, excitation from the excitation light source 2 is performed in the order of the variable optical filters 4- (n-1), 4- (n-2) ,. The characteristics of the variable optical filters 4-1 to 4- (n) are controlled so as to block light . As a result, as the temperature of the EDF 3 decreases from a high temperature to a low temperature, the effective length related to the amplification of the EDF 3 is sequentially shortened.

At the lowest temperature, the characteristics of the variable optical filter 4-1 closest to the excitation light source 2 are controlled so as to block the excitation light . In this case, the effective length related to the amplification of the EDF 3 is only the length of the EDF 3-1. As described above, since the effective length related to the amplification of the EDF 3 is shortened at a low temperature, the gain on the short wave side is increased, and the increase in the gain on the long wave side due to temperature dependence can be compensated.

  As described above, according to the first embodiment of the present invention, the temperature of the EDF 3 is measured, and the effective wavelength related to the amplification of the EDF 3 is changed in accordance with the temperature, so that the gain wavelength inclination depending on the temperature is changed. Can be compensated.

<Second Embodiment>
FIG. 3 shows a second embodiment of the present invention. As shown in FIG. 3, in the optical amplifier according to the second embodiment of the present invention, the EDF 103 is divided into n pieces. Optical filters 104-1 to 104- (n-1) are inserted between the divided EDFs 103-1 to 103- (n). The bands of the optical filters 104-1 to 104- (n-1) are different. In front of the EDF 103, an excitation light multiplexing coupler 101 is disposed. A pumping light multiplexing coupler 101 from the variable-wavelength excitation light source 102, the excitation light is supplied. The wavelength of the excitation light from the variable wavelength excitation light source 102 can be varied by a control signal from the pumping light wavelength control circuit 115.

Further, the thermistor 111 detects the temperature of the EDF 3. The temperature detection output of the thermistor 111 is sent to the excitation light wavelength control circuit 115. Pumping light wavelength control circuit 115, based on the temperature data EDF3 sent from the thermistor 111, and controls the wavelength of the excitation light from the variable wavelength excitation light source 102, depending on the temperature the effective length relating to the amplification of EDF3 change Let

  In the first embodiment described above, the temperature of the EDF 3 is detected by the thermistor 11, and the characteristics of the variable optical filters 4-1 to 4- (n) are controlled based on the temperature of the EDF 3, thereby relating to the amplification of the EDF 3. The effective length is varied.

In contrast, in this second embodiment, detects the temperature of EDF103 by the thermistor 111, based on the temperature of EDF103, by controlling the wavelength of the excitation light from the variable wavelength excitation light source 102, the amplification of EDF3 The effective length involved is varied.

That is, when the hottest temperature of EDF3 is, all light filter 104-1~104- (n) is to pass the excitation light, the wavelength of the excitation light from the variable-wavelength excitation light source 102 is controlled. In this case, the effective length related to the amplification of the EDF 103 is the total length of all the EDFs 103-1 to 103- (n). As described above, since the effective length related to amplification of the EDF 103 becomes longer at high temperatures, the gain on the long wave side is increased, and the increase in the gain on the short wave side due to temperature dependence can be compensated.

When the temperature of the EDF 103 decreases slightly, the optical filter 104- (n-1) blocks the excitation light, and all the other optical filters pass the excitation light . The wavelength is controlled. In this case, the effective length related to the amplification of the EDF 103 is the total length of the EDFs 103-1 to 103- (n-1), and the effective length related to the amplification of the EDF 103 is slightly shortened.

Hereinafter, as the temperature of the EDF 103 decreases from a high temperature to a low temperature, the excitation light is blocked in the order of the optical filters 104- (n-1), 104- (n-2),. , the wavelength of the excitation light from the variable-wavelength excitation light source 102 is controlled. As a result, as the temperature of the EDF 103 decreases from a high temperature to a low temperature, the effective length related to the amplification of the EDF 103 is sequentially shortened.

During the coldest, so that the characteristic of the optical filter 104-1 is closest to the excitation light source to block the excitation light, the wavelength of the excitation light from the variable-wavelength excitation light source 102 is controlled. In this case, the effective length related to the amplification of the EDF 103 is only the length of the EDF 103-1. As described above, since the effective length related to the amplification of the EDF 103 is shortened at a low temperature, the gain on the short wave side is increased, and the increase in the gain on the long wave side due to temperature dependence can be compensated.

  In the above-described embodiment, the configuration of forward excitation has been described. However, the present invention can be similarly applied to the configuration of backward excitation.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the gist of the present invention.

1 Pumping light coupler 1
2 Excitation light source 3,3-1 to 3- (n) EDF
4,4-1 to 4- (n-1) Variable optical filter 11 Thermistor 15 Optical filter wavelength control circuit 103, 103-1 to 103- (n) EDF
104, 104-1 to 104- (n-1) Optical filter 101 Excitation light multiplexing coupler 102 Variable wavelength excitation light source 104 Optical filter 111 Thermistor 115 Excitation light wavelength control circuit 201 Excitation light multiplexing coupler 202 Excitation light source 211 Thermistor 212 Temperature control circuit 213 Heater 214 Thermal insulation case

Claims (5)

An optical amplification medium divided into a plurality of parts;
An excitation light generating means for supplying pumping light to said optical amplifying medium,
Temperature detecting means for detecting the temperature of the optical amplification medium;
Control means for varying an effective length related to amplification of the optical amplification medium according to the temperature of the optical amplification medium;
With
Inserting a variable optical filter having a characteristic of passing / blocking the excitation light between each of the plurality of divided optical amplification media,
The control means controls the variable optical filter in accordance with the temperature of the optical amplifying medium to vary the effective length related to the amplification of the optical amplifying medium. An optical amplification medium divided into a plurality of parts;
Excitation light generating means for supplying excitation light to the optical amplification medium;
Temperature detecting means for detecting the temperature of the optical amplification medium;
Control means for varying an effective length related to amplification of the optical amplification medium according to the temperature of the optical amplification medium;
With
Inserting an optical filter having a passband of excitation light of a specific wavelength between each of the plurality of divided optical amplification media,
An optical amplifier characterized in that the control means controls the wavelength of the pumping light according to the temperature of the optical amplifying medium to vary the effective length related to amplification of the optical amplifying medium. The optical amplifier according to claim 1 , wherein the optical amplification medium is an erbium-doped optical fiber. In a control method of an optical amplifier that performs optical amplification by supplying excitation light to an optical amplification medium,
Dividing the optical amplification medium into a plurality of parts;
Inserting a variable optical filter having a characteristic of passing / blocking the excitation light between each of the plurality of divided optical amplification media,
An optical amplifier control method , wherein the effective length related to amplification of the optical amplification medium is varied by controlling the variable optical filter according to the temperature of the optical amplification medium. 4. An optical amplifier control program for executing the control means in the optical amplifier according to claim 1 .

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