JP2005210141A - Optical amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical amplifier in which the gain is not changed even if an external temperature is changed, the temperature controllability is good, the size is compact and the power consumption is reduced. <P>SOLUTION: The optical amplifier comprises at least an Er-added optical fiber for optical amplification giving an amplification band of 1.58 μm; a heating element to apply a positive or negative heat to the optical fiber; a temperature detecting means to detect the temperature of the optical fiber; a power control means to control power supplied to the heating element; and an wavelength combiner to combine the excitation light from an excitation light source with signal lights having a plurality of wavelengths giving a band of 1.58 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical amplifier that amplifies an optical signal.

  As is well known, an Er-doped optical fiber amplifier (EDFA) is a key device for 1.5 μm band optical communication, and research is proceeding toward application to a wavelength division multiplexing (WDM) communication system.

  The gain characteristics of the EDFA are temperature dependent. For this reason, in the EDFA, when the external temperature changes, the gain increases or decreases.

  By the way, this EDFA has a fiber length in which the temperature coefficient of gain at each temperature is equal, as illustrated in FIGS. That is, in FIGS. 13 to 15, there is a point (indicated by an arrow in the figure) where the gain curves with respect to each temperature intersect at one point, and the fiber length at this time is referred to as a temperature-independent fiber length. Therefore, a temperature-independent EDFA can be realized by using an Er-doped fiber (EDF) having this length (Non-patent Document 1).

  However, the temperature coefficient of gain differs depending on the signal wavelength. Therefore, in a WDM EDFA that amplifies signals of multiple wavelengths at once, the temperature-independent fiber length varies depending on each signal wavelength, and the fiber length is optimal with respect to temperature. Can not be converted. For this reason, it is necessary to keep the temperature of the WDM EDFA constant, and an EDFA with a temperature control function has been demanded.

  Conventionally, there has been an EDFA with a temperature control function in which temperature control is performed on a package containing an Er-doped fiber (EDF) in response to the above requirement (Patent Document 1).

  However, this conventional form does not directly control the temperature of the EDF, so the temperature controllability is poor, and the temperature of not only the EDF but also the entire package is controlled. There were three drawbacks:

Japanese Patent Application No. 2-208923 M. Yamada et al., IEEE Journal of Quantum Electronics, vol.28, No.3, pp.640-649, 1992

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical amplifier that does not vary in gain even when the external temperature changes, has good temperature controllability, is small, and has low power consumption. There is.

  The optical amplifier of the present invention is characterized by having a constant gain by keeping the temperature of the optical fiber constant, excellent temperature controllability, small size and low power consumption. Have

  In other words, the optical amplifier of the present invention detects an Er-doped optical fiber for optical amplification whose amplification band is in the 1.58 μm band, a heating element that applies positive or negative heat to the optical fiber, and detects the temperature of the optical fiber. Temperature detecting means, power control means for controlling the power supplied to the heating element, and a multiplexer for combining the excitation light from the excitation light source and the signal light having a plurality of wavelengths in the 1.58 μm band, It is characterized by providing.

  The optical amplifier according to the present invention is characterized in that the Er-doped optical fiber is wound in a coil shape.

  The optical amplifier according to the present invention is characterized in that the optical Er-doped fiber is in contact with the heating element, and an Er-doped optical fiber wound in a coil shape is covered with the heating element.

  In the optical amplifier, the Er-doped optical fiber and the heating element are formed in a state where the heating element is formed in a linear shape, and the linear heating element is wound around a bundle of Er-doped optical fibers wound in the coil shape. May be in contact with each other.

  In the optical amplifier, the Er-doped optical fiber is in contact with the heating element, the heating element is formed in a linear shape, and the heating element and the Er-doped optical fiber are wound together in a coil shape to add the Er The optical fiber and the heating element may be in contact.

  The optical amplifier according to the present invention is characterized in that the Er-doped optical fiber is wound around a bobbin in a coil shape, and the heating element is attached to the bobbin.

  The optical amplifier according to the present invention is characterized in that the Er-doped optical fiber, the heating element, the temperature detection means, and the power control means are housed in a package.

  The optical amplifier of the present invention is characterized in that a heat insulating material is attached to the inside of the package.

  In the optical amplifier according to the present invention, the host of the Er-doped optical fiber includes a quartz optical fiber material, a fluoride optical fiber material, a tellurite optical fiber material, a multicomponent oxide optical fiber material, and a fluorophosphate optical fiber material. It is characterized by being composed of one or more materials selected from chalcogenide glass optical fiber materials.

  In the optical amplifier of the present invention, the heating element is a conductive heating element that applies a positive amount of heat to the Er-doped optical fiber.

  In the optical amplifier of the present invention, the heating element is a heat absorption element that applies a negative amount of heat to the optical fiber.

  In the optical amplifier of the present invention, when the external temperature changes, the gain is controlled by keeping the temperature of the EDF constant, and a constant gain is always obtained. Furthermore, it is superior in temperature controllability compared to conventional optical amplifiers, and is small in size and low in power consumption.

  By applying such an optical amplifier to an optical communication system, it is possible to construct a system that does not deteriorate transmission characteristics even when there is a change in external temperature.

  Embodiments of the present invention will be specifically described with reference to the following embodiments. However, the present invention is not limited to the following embodiments.

(Example 1)
FIG. 1 is a perspective view showing a first embodiment of an optical amplifying element used in the optical amplifier of the present invention. In the figure, 1 indicates an Er-doped optical fiber, and 2 indicates a silicon rubber heater (conductive heating element) as a heating element. 3a is a thermocouple, 3b is a voltmeter or a temperature monitor, and these constitute temperature detecting means. Furthermore, 5 indicates a power supply device (power control means) for supplying power to the heating element 2. Each of the components is housed in a package for use, and is fixed on a support substrate 100 constituting a part of the package. As shown in the figure, the Er-doped optical fiber 1 is wound a required number of times on a support substrate 100 to form a coiled bundle, and the silicon rubber heaters 2 and 2 sandwich the coiled bundle portion. It is out.

  As described above, the optical amplifying element according to the present embodiment provides heat control directly to the Er-doped optical fiber 1 so that higher temperature controllability than that of the conventional device that applies heat to the package can be obtained. A power amplifying optical element has been realized. Quantitatively, the volume is three-quarters and the power consumption is one-half compared to the prior art described above. FIG. 1 shows a state in which the package is opened. As described above, the support substrate 100 is a part of the package, and the components 1 to 5 are included in the package (one box). It is stored in. In the present embodiment, a heat insulating material (not shown) is placed inside the package to improve temperature controllability.

  As the Er-doped fiber 1, an Er-doped silica fiber (refractive index difference 1.8%, cutoff wavelength 0.9 μm, Er addition concentration 1000 ppm, Al addition concentration 4 wt%, length 175 m) was used. The temperature of the Er-doped fiber 1 is kept constant by monitoring the temperature by the temperature detection means 4 including the thermocouple 3 and the voltmeter or the temperature monitor 4 and controlling the power supplied from the power supply device 5.

  2A to 2D are diagrams illustrating a configuration example of an optical amplifier using the optical amplifying element of this embodiment. In the figure, these optical amplifiers include an optical amplifying element 6 according to the present embodiment, multiplexers 7 and 7 that combine excitation light and signal light, excitation light sources 8 and 8, isolators 9 and 9, A circulator 10 and a total reflection mirror (fiber having a total reflection mirror coated on the end face) 11 are configured. A bulk WDM coupler was used as the multiplexer 7, and a 1.48 μm band LD was used as the excitation light source 8.

  In the case of using the configuration of FIG. 2A, FIG. 3 shows gain characteristics when temperature control is not performed, and FIG. 4 shows gain characteristics when temperature control is performed (80 ° C.).

  As apparent from FIGS. 3 and 4, it can be seen that the temperature dependence of the gain is eliminated by controlling the temperature. For example, the gain deviation of 3.7 dB at 1570 mm and 6.5 dB at 1595 nm is suppressed to 0.3 dB by temperature control.

  Even when the 0.98 μm band LD was used as the excitation light source, the gain could be kept constant by performing the temperature control as in the case of using the 1.48 μm band LD.

  As described above, by using the optical amplifying element of the present embodiment, a temperature-independent optical amplifier having better temperature control than the prior art, small size and low power consumption can be realized.

  Although the remaining configurations of FIGS. 2B, 2C, and 2D were used, a similar temperature-independent optical amplifier could be realized.

  5, 6 and 9 collectively show other forms of the optical amplifying element. In the figure, the same components as those in FIG.

(Embodiment example 2 reference)
The configuration of FIG. 5 is characterized in that a linear heater 2a is wound around the Er-doped optical fiber 1 in a coiled bundle. By taking this form, the power consumption is further reduced as compared with the optical amplifying element of the first embodiment (FIG. 1). Specifically, in the element shown in FIG. 5, the required power consumption is three-quarters that of the optical amplifying element of the first embodiment.

(Embodiment example 3 reference)
In the configuration of FIG. 6, the Er-doped optical fiber 1 and the linear heater 2b are bundled so as to be alternately arranged and wound in a coil shape, as shown in FIG. 7 or FIG. The winding method of the optical fiber 1 and the linear heater 2b can be arranged as shown in FIG. 7 or FIG. Thus, by simultaneously winding the optical fiber 1 and the heater 2b, the power consumption is lower than that of the optical amplifying element of the first embodiment shown in FIG. Furthermore, work such as wrapping the heater after winding the optical fiber can be omitted, thus improving workability. Specifically, compared with the optical amplifying element of the first embodiment, the power consumption is three quarters and the creation work time is one half.

(Embodiment example 4)
The configuration of FIG. 9 is characterized in that a planar heater 2c is built in a bobbin 200 around which an Er light-added fiber 1 is wound. By adopting this embodiment, alignment between the optical fiber 1 and the heater, which is necessary in the configuration of FIG. 8, is unnecessary, and workability is improved as compared with the optical amplifying element of FIG. Specifically, compared with the optical amplifying element of FIG. 8, the working time was ½, and the power consumption was comparable to that of the optical amplifying element of the first embodiment (FIG. 1).

  5, 6, and 9 show a state where the package is opened, and the components 1 to 5 are housed in one box (package). In the present embodiment, a heat insulating material (not shown) is placed inside the package to improve temperature controllability.

  Using these optical amplifying elements, an optical amplifier was configured as in the first embodiment, and a temperature-independent optical amplifier could be realized.

(Embodiment 5)
The basic configuration of the optical amplifying element of this embodiment is the same as that of the first embodiment. In this embodiment, the material composition of the element was changed.

  An optical amplifying element was constructed using various Er-doped optical fibers having different host glass compositions, and an optical amplifier was constructed using this element. Tables 1 and 2 show the temperature characteristics of this optical amplifier. The temperature change of the gain in the table indicates the difference between the maximum gain and the minimum gain when the external temperature is changed from −40 to + 80 ° C.

  Thus, by changing the type of the optical amplifying element, a temperature-independent optical amplifier having better temperature control than the prior art, small size and low power consumption can be realized.

(Embodiment 6)
FIG. 10 shows a sixth embodiment of the optical amplifying element used in the optical amplifier of the present invention. In the figure, the same components as those in FIG. In the figure, reference numeral 12 denotes a Peltier element (an endothermic heating element) that applies a negative amount of heat, and is laid under the optical fiber 1 wound in a coil shape. Electric power is supplied from the power source 5 to the Peltier element 12.

  As described above, the optical amplifying element according to the present embodiment provides heat control directly to the Er-doped optical fiber 1 to obtain higher temperature controllability than the conventional one that applies heat to the package, and is small in size and low in power consumption. The optical amplifying element is realized. Specifically, compared with the prior art, the volume is 3/4 and the power consumption is 1/2. FIG. 10 shows a state in which the package is opened, and the components 1 to 5 and 12 are housed in one box (package). In the present embodiment, a heat insulating material is placed inside the package to improve temperature controllability.

  As the Er-added fiber 1, an Er-added silica-based fiber (relative refractive index difference 1.8%, cutoff wavelength 0.9 μm, Er addition concentration 1000 ppm, Al addition concentration 4 wt%, length 175 m) was used. The temperature of the Er-doped fiber 1 is monitored by the thermocouple 3 and the voltmeter or the temperature monitor 4 and is kept constant by controlling the power source 5.

  In the optical amplifier configured as shown in FIG. 2A, FIG. 11 shows gain characteristics when the temperature of the optical amplifying element is not controlled, and FIG. 12 shows gain characteristics when the temperature is controlled (20 ° C.).

  As is apparent from both figures, it is understood that the temperature dependence of the gain is eliminated by controlling the temperature. For example, the gain deviation of 3.7 dB at 1570 nm and 6.5 dB at 1595 nm is suppressed to 0.4 dB by temperature control.

  Even when a 0.98 μm band LD was used as an excitation light source, the gain could be kept constant by performing temperature control as in the case of using a 1.48 μm band LD.

  As described above, in the present invention, by using the optical amplifying element of the above embodiment, a temperature-independent optical amplifier having better temperature control than the prior art, small size and low power consumption can be realized.

  Although the configurations of FIGS. 2B, 2C, and 2D were used, a temperature independent optical amplifier similar to the configuration of FIG. 2A could be realized.

It is a perspective view which shows the structure of the 1st Example of the optical amplification element used for the optical amplifier of this invention. (A)-(d) is a block diagram which shows the structure of the optical amplifier of this invention using the optical amplification element of 1st Embodiment, respectively. 6 is a graph showing temperature characteristics (without temperature control) of the optical amplifier according to the first embodiment. 6 is a graph showing temperature characteristics (with temperature control) of the optical amplifier according to the first embodiment. It is a perspective view which shows the 2nd reference embodiment example of the optical amplification element which can be used for the optical amplifier of this invention. It is a perspective view which shows the 3rd reference embodiment example of the optical amplifying element which can be used for the optical amplifier of this invention. It is sectional drawing which shows the combination structure of the optical fiber and heater of the optical amplification element shown in FIG. It is sectional drawing which shows the other combination structure of the optical fiber and heater of the optical amplification element shown in FIG. It is a perspective view which shows the example of 4th Embodiment of the optical amplification element used for the optical amplifier of this invention. It is a perspective view which shows the 6th Example of the optical amplification element used for the optical amplifier of this invention. It is a graph which shows the temperature characteristic (without temperature control) of the optical amplifier of this invention by the 6th Example of an optical amplification element. It is a graph which shows the temperature characteristic (with temperature control) of the optical amplifier of this invention by the 6th Example of an optical amplifier element. It is a graph explaining the characteristic of the conventional optical amplifier. It is a graph explaining the characteristic of the conventional optical amplifier. It is a graph explaining the characteristic of the conventional optical amplifier.

Explanation of symbols

1 Er-doped fiber 2 Silicon rubber heater (conductive heating element; heating element)
2a Linear heater (conductive heating element; heating element)
2b Linear heater (conductive heating element; heating element)
2c Planar heater (conductive heating element; heating element)
3 Thermocouple 3b Voltmeter or temperature monitor 4 Temperature detection means 5 Power supply (power control means)
6 Optical Amplifier 7 Multiplexer 8 Excitation Light Source 9 Isolator 10 Optical Circulator 11 Total Reflection Mirror 12 Peltier Element (Endothermic Heating Element)
100 substrate (part of the package)
200 bobbins

Claims (9)

An Er-doped optical fiber for optical amplification having an amplification band in the 1.58 μm band;
A heating element that applies positive or negative heat to the Er-doped optical fiber;
Temperature detecting means for detecting the temperature of the Er-doped optical fiber;
Power control means for controlling the power supplied to the heating element;
A multiplexer that combines the excitation light from the excitation light source and the signal light having a plurality of wavelengths in the 1.58 μm band;
An optical amplifier comprising:   The optical amplifier according to claim 1, wherein the Er-doped optical fiber is wound in a coil shape.   The optical amplifier according to claim 2, wherein the Er-doped optical fiber is in contact with the heating element, and the Er-doped optical fiber wound in a coil shape is covered with the heating element.   The optical amplifier according to claim 2, wherein the Er-doped optical fiber is wound around a bobbin in a coil shape, and the heating element is attached to the bobbin.   5. The optical amplifier according to claim 1, wherein the Er-doped optical fiber, the heating element, the temperature detection unit, and the power control unit are housed in a package.   The optical amplifier according to claim 5, wherein a heat insulating material is attached inside the package.   The host of the Er-doped optical fiber is a silica-based optical fiber material, a fluoride-based optical fiber material, a tellurite-based optical fiber material, a multicomponent oxide-based optical fiber material, a fluorophosphate-based optical fiber material, or a chalcogenide glass optical fiber material. 7. The optical amplifier according to claim 1, wherein the optical amplifier is made of one or more materials selected from the inside.   8. The optical amplifier according to claim 1, wherein the heating element is a conductive heating element that applies a positive amount of heat to the optical fiber. 8. The optical amplifier according to claim 1, wherein the heating element is a heat absorption element that applies a negative amount of heat to the optical fiber.

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